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Dissolved Oxygen TMDL Protocols and Submittal Requirements Originally Prepared by the Dissolved Oxygen TMDL Protocol Team: Ron Jacobson (retired), Jim Klang (former MPCA employee), Carol Sinden, Chuck Regan (former MPCA employee), Hafiz Munir Reviewed by: John Hensel, Glenn Skuta, Jeff Risberg, Tim Larson, Lee Ganske, Greg Johnson, Jim Hodgson, and Chris Zadak Modified by the Current Dissolved Oxygen TMDL Protocol Team: Mark Evenson, Nick Gervino, Bruce Henningsgaard, Hafiz Munir, Mike Trojan, Jim Ziegler Minnesota Pollution Control Agency December 2008

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Dissolved Oxygen TMDL Protocols

and Submittal Requirements

Originally Prepared by the Dissolved Oxygen TMDL Protocol Team:

Ron Jacobson (retired), Jim Klang (former MPCA employee), Carol Sinden, Chuck Regan (former MPCA employee), Hafiz Munir

Reviewed by: John Hensel, Glenn Skuta, Jeff Risberg, Tim Larson, Lee Ganske, Greg Johnson,

Jim Hodgson, and Chris Zadak

Modified by the Current Dissolved Oxygen TMDL Protocol Team:

Mark Evenson, Nick Gervino, Bruce Henningsgaard, Hafiz Munir, Mike Trojan, Jim Ziegler

Minnesota Pollution Control Agency December 2008

Minnesota Pollution Control Agency 2

Table Of Contents I. Introduction

A. Purpose.............................................................................................................................5 B. How this report is organized ............................................................................................5 C. Total Maximum Daily Load overview ............................................................................5 D. What is a TMDL? ............................................................................................................6 E. What is the process for completing TMDLs? ..................................................................6 F. Who is responsible for doing TMDLs? ...........................................................................7 G. Site-Specific Approaches.................................................................................................8

II. About DO and Watershed Investigations A. DO Technical Resources..................................................................................................8 B. Stressor Identification Overview .....................................................................................10

a. Stressor Identification Information Resources ....................................................10 b. Definitions............................................................................................................10 c. Stressor Identification Framework.......................................................................11

C. Stream Health and DO.....................................................................................................16 a. Definitions............................................................................................................16 b. DO Chemical and Physical Stressor Parameter Interactions ...............................18 c. External Influences ..............................................................................................20 d. Internal Influences ...............................................................................................20 e. Stressor Sources on Streams ................................................................................26

D. Problem Definition...........................................................................................................31 a. Applicable Water Quality Rules ..........................................................................31 b. Numeric Standards...............................................................................................32

E. Overview of TMDL Project Decision Points...................................................................35 F. Initial Problem Assessment..............................................................................................39

a. Comprehensive Data Collection from Existing Resources..................................41 b. Data Review and Evaluation................................................................................44 c. Prominent Data Gaps ...........................................................................................44 d. Stressor Identification Starting Questions ...........................................................45 e. Consideration of the Dynamics in a Watershed...................................................46

G. Critical Project Design Conditions ..................................................................................46 a. Early Monitoring Contract...................................................................................47

H. Determining Rigor ...........................................................................................................49 I. Analysis............................................................................................................................50

a. Basic Objectives...................................................................................................50 b. Selecting an Appropriate Analytical Tool ...........................................................51 c. Available Models .................................................................................................54 d. General Approach Alternatives............................................................................56 e. Define and Develop Specific Approach ..............................................................56 f. Additional Data Acquisition to Support Analysis Framework ............................56 g. Model Set-Up and Evaluation..............................................................................60

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Dissolved Oxygen TMDL Protocols and Submittal Requirements

J. Development of Example Evaluation Scenarios..............................................................63 K. Project Case Example and Stressor ID Discussion .........................................................65

III. Dissolved Oxygen TMDL Submittal Requirements A. Dissolved Oxygen TMDL Submittal Requirements........................................................74 B. Identification of Waterbody, Pollutant of Concern, Pollutant Sources and

Priority Training...............................................................................................................75 C. Description of the Applicable Water Quality Standards and Numeric Water

Quality Target ..................................................................................................................76 D. Loading Capacity - Linking Water Quality and Pollutant Sources .................................77 E. Load Allocations (LAs) ...................................................................................................79 F. Wasteload Allocations (WLAs) ......................................................................................80 G. Margin of Safety (MOS) .................................................................................................86 H. Reserve Capacity (allocation for future growth) ............................................................88 I. Seasonal Variation ..........................................................................................................90 J. Reasonable Assurances ...................................................................................................90 K. Monitoring Plan to Track TMDL Effectiveness .............................................................93 L. Implementation ...............................................................................................................96 M. Public Participation .........................................................................................................98 N. Submittal Letter ..............................................................................................................101 O. Administrative Record ....................................................................................................101

IV. Appendices

A. Minnesota’s TMDL submittal checklist ..........................................................................102 B. Guidance for Communities on How to Integrate Lower Minnesota River Dissolved Oxygen

TMDL Requirements and MS4 Stormwater Pollution Prevention Programs .................104 C. More Case Examples (under construction)

V. Figures

1: Stressor Identification Management Context...................................................................12 2: Subsets of Figure 1. SI Management Context (Figures 2-5) ...........................................13-15 6: Stream DO Balance..........................................................................................................19 7: Stream DO Response to a Point Source Discharge .........................................................21 8: DO sag curve from multiple pollutant loadings along a reach from nonpoint sources (response not modeled or to scale; example only)..............................................22 9: Diurnal Dissolved Oxygen response to photosynthetic cycles ........................................23 10: Diurnal Dissolved Oxygen response to photosynthetic cycles comparison with eutrophic systems.............................................................................................................24 11: A stream reach without vegetative shade.........................................................................25 12: A wide stream with no riparian slopes with significant tree shade..................................25 13: Flowchart Diagram of the Low Dissolved Oxygen General Problem Investigation and Attainment Strategy.............................................................................36

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Dissolved Oxygen TMDL Protocols and Submittal Requirements

14. Stick Figure and Equation for Mass Balance Approach..................................................52 15. Diagram concept of a one-dimensional model ................................................................53 16. Graphical depiction of a 3-dimensional model................................................................54 17. Collection of velocity data to use in combination with channel geometry to develop stage-discharge relationships for the stream ..................................................58 18. A time-of-travel study using dye tracer techniques .........................................................59 19. Preliminary Data Stick Figure Map ................................................................................66 20. Stick Figure Map Showing Longitudinal Survey Stations ..............................................68 21. Iterative TMDL Process...................................................................................................93

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Dissolved Oxygen TMDL Protocols and Submittal Requirements

Part I. Introduction

A. Purpose The purpose of this document is to provide guidance on the submission requirements for Low Dissolved Oxygen Total Maximum Daily Load (TMDL) studies by the Minnesota Pollution Control Agency (MPCA) and the United States Environmental Protection Agency (EPA). The intended audience is MPCA staff and management, as well as technical staff of local organizations and consulting firms responsible for developing TMDLs. While several technical Dissolved Oxygen (DO) references are provided, the guidance is based on the assumption that the reader has some working knowledge of watershed science and is willing to augment the TMDL project technical team with members who have a deeper knowledge regarding DO as needed. This includes the specific skills required for monitoring and assessment techniques, modeling tools and restoration practices. This guidance is designed to bridge the gap between general watershed programs, such as Minnesota’s Clean Water Partnership and Section 319 programs, and the unique requirements of TMDLs. While this guidance is intended to build a common understanding of TMDLs, it will not meet every project need. Each TMDL project tends to have its own unique set of issues and challenges. The MPCA will provide the assistance and oversight needed to address these issues on a case by case basis.

B. How This Report Is Organized This document is organized into three sections:

Chapter I explains the purpose and scope of this document, and provides a brief overview of the TMDL process.

Chapter II explains the science principles and fundamentals needed to undertake an investigative study. Discussion includes: the stressor identification tool and how it is used in the discovery process, a chapter continues with a discussion explaining the fragile natural balance a healthy watershed has with regard to stream health and DO, and the critical parameters and typical sources commonly found to be contributing to a low DO condition.

Chapter III explains the EPA and Minnesota TMDL submission requirements. Chapter IV (undeveloped) reviews project options for conditions when very low or no flow exists in

the receiving water. These conditions can occur in backwater effects at river confluences, intermittent streams, or ephemeral conditions (standing water without velocity in natural or artificial systems).

C. TMDL Overview The TMDL process offers an excellent opportunity to identify and restore water quality in stream, rivers, and lakes, as well as enhance involvement of watershed residents and stakeholders in water quality issues. Other potential benefits of the TMDL process to projects include:

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Encourages the development of a consistent framework for conducting water quality studies; Defines existing impairments and pollution sources, quantifies source reductions, and sets

comprehensive restoration strategies to meet water quality standards; Provides a framework for assessing future impacts to water quality; Accelerates the schedule at which impaired waters are addressed through more effective

coordination of existing and future resources among local entities, state, and federal environmental agencies;

Provides a basis for revising local regulations (e.g., zoning and sub-division) and developing performance-based standards for future development; and

Facilitates the incorporation of TMDL schedules and implementation activities into local government water plans.

D. What is a TMDL? A TMDL or Total Maximum Daily Load (TMDL) is a calculation of the maximum amount of a pollutant that a water body can receive and still meet water quality standards, and an allocation of that amount to the pollutant’s sources. Section 303(d) of the Clean Water Act (CWA) and its implementing regulations (40 C.F.R. § 130.7) require states to identify waters that do not or will not meet applicable water quality standards and to establish TMDLs for pollutants that are causing non-attainment of water quality standards. Water quality standards are set by States, Territories, and Tribes. They identify the uses for each water body, for example, drinking water supply, contact recreation (swimming), aquatic life support (fishing), and the scientific criteria to support that use. As described in detail in Part II of this guidance, a TMDL needs to account for seasonal variation and must include a margin of safety (MOS). The MOS is a safety factor that accounts for any lack of knowledge concerning the relationship between effluent limitations and water quality. Also, a TMDL must specify pollutant load allocations among sources. The total of all allocations, including wasteload allocations (WLA) for point sources, load allocations (LA) for nonpoint sources (including natural background), and the MOS (if explicitly defined) cannot exceed the maximum allowable pollutant load:

TMDL =sumWLAs + sumLAs + MOS + RC* • The MPCA also requires that “Reserve Capacity” (RC) which is an allocation for future growth be

addressed in the TMDL. See page 88 for more information. A TMDL study identifies all sources of the pollutant and determines how much each source must reduce its contribution in order to meet the quality standard. The sum of all contributions must be less than the maximum daily load.

E. What is the process for completing TMDLs? As noted above, the Clean Water Act Section 303 establishes the water quality standards and TMDL programs. Section 303(d) of the CWA requires states to publish, every two years, an updated list of streams and lakes that are not meeting their designated uses because of excess pollutants. These water bodies are considered impaired for their uses.

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The TMDL Process

Assess the state’s waters ↓

List those that do not meet standards

↓ Identify sources and reductions

needed (TMDL Study)

↓ Implement restoration activities

(Implementation Plan) ↓

Evaluate water quality

The list, known as the 303(d) list, is based on violations of water quality standards and is organized by river basin. States must establish priority rankings for waters on the lists and develop TMDLs for listed waters. Minnesota’s 303(d) list can be found on the MPCA Web site at: http://www.pca.state.mn.us/water/tmdl/index.html. The 2006 Guidance Manual for Assessing the Quality of Minnesota’s Surface Waters for Determination of Impairment: 305(b) Report and 303(d) List explains MPCA’s process for assessing water bodies for the 305(b) report and the 303(d) impaired waters list. The guidance manual is also on the MPCA web site at: http://www.pca.state.mn.us/publications/manuals/tmdl-guidancemanual04.pdf .

The Clean Water Act requires a completed TMDL for each water identified on a state’s Impaired Waters list. Lakes or river reaches with multiple impairments require multiple TMDLs. States have the primary responsibility for developing TMDLs and submitting them to EPA for review and approval. If EPA disapproves a TMDL, EPA is required to establish the TMDL. The process for completing a TMDL study is complex and varies significantly from project to project. Some of the many variables that determine scope of a project include:

o Number of pollutant sources o Type of pollutant and size of the watershed o Amount of existing data o Relationship of one impairment to others that

may exist in the same or nearby water bodies o Extent of stakeholder involvement o Availability of necessary resources.

Public participation is critical throughout the TMDL process and Minnesota expects advisory groups to be involved from the earliest stages of the project. At a minimum, the EPA requires that the public must be given an opportunity to review and comment on TMDLs before they are formally submitted to EPA for approval. Every TMDL is formally public noticed in Minnesota with a minimum 30-day comment period. After a TMDL is approved by the EPA, a detailed implementation plan is finalized to meet the TMDL’s pollutant load allocation and achieve the needed reductions to restore water quality. Depending on the severity and scale of the impairment, restoration may require 10-20 years or longer and millions of dollars. Further information on MPCA’s TMDL implementation policy can be found at: http://intranet.pca.state.mn.us/policies/programpolicies/i-wq2-031.pdf The reader is also encouraged to refer to EPA’s 1991 guidance document: “Guidance for Water Quality- based Decisions: The TMDL Process” at http://www.epa.gov/OWOW/tmdl/decisions/ for a more complete description of the federal program.

F. Who is responsible for doing TMDLs? The MPCA is ultimately responsible for completing and submitting TMDLs to the EPA. However, stakeholders play a critical role in the development and implementation of TMDLs. Locally-driven

Dissolved Oxygen TMDL Protocols and Submittal Requirements

projects are most likely to succeed in achieving water quality goals because local communities often best understand the sources of water quality problems and effective solutions to those problems. Their work to develop and implement TMDLs is a key tool to restore and maintain our rivers, streams and lakes. For more than two decades, the MPCA has contracted with counties, watershed districts, soil and water conservation districts, and other local organizations to diagnose and help restore lakes and streams polluted from nonpoint sources. This watershed work was completed through the agency’s Clean Water Partnership and Clean Water Act Section 319 programs. Many local government agencies have gained considerable expertise in watershed work and public involvement in part due to this experience. Building off of this success, the MPCA will provide grant contracts to qualified local governments and watershed organizations to lead an estimated two-thirds of TMDL projects. The MPCA will direct the remaining projects. The contracts cover staffing, equipment, lab costs, and other project expenses. In addition, scientific and technical experts provide valuable information and insight. In many cases, private consultants assist with data collection, modeling, and development of draft reports. The MPCA estimates that nearly 95 percent of all the state’s TMDL funding for study completion will be passed through to local-governments and contractors. The MPCA provides oversight, technical assistance, and training to ensure regulatory and scientific requirements are met. The MPCA submits final TMDLs for EPA approval. For additional information on TMDL grant requirements, see MPCA’s TMDL workplan guidance at: http://www.pca.state.mn.us/publications/wq-iw1-01.pdf.

G. Site-Specific Approaches The Clean Water Act, federal regulations, Minnesota’s State Water Pollution Control Act and Minnesota’s water quality rules establish opportunities to use site-specific approaches to address water quality impairments. These may be appropriate for some water bodies where numeric criteria different from those presently contained in the water quality standards need to be established to protect beneficial uses. Site-specific options allow the MPCA to consider data on local water body characteristics to apply more precise numeric standards to protect the beneficial uses of the water body. A detailed discussion of site-specific approaches is contained in the companion TMDL protocol for lakes impaired by excessive nutrients. The MPCA does not anticipate that site-specific approaches will be applied frequently, but these options may be required with some dissolved oxygen TMDLs. Part II: About DO and Watershed Investigations This chapter is meant to bring individuals that are new to the chemistry and physical sciences regarding stream interactions with DO and the stressing pollutant parameters to a working understanding for project management. If the reader does not have a significant understanding of the watershed management requirements for DO, then the project team should include individuals with the expertise.

A. DO Technical Resources DO guidance documents for wastewater treatment facilities are well established for determining the allowable remaining load (wasteload allocations) for the National Pollutant Discharge Elimination

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System (NPDES) permit effluent limit setting purposes. These processes are either: a) reach specific and often assume upstream loads at the reach boundary as a given; or b) TMDL watershed guidance (with less specific detail). The purpose of the documents in group a) are for the NPDES program and most often are used to determine the remaining loading capacity available in order to set limits for those NPDES permits under review. These documents present the detailed science requirements for assessing or modeling one or more pollutant source impact on a given stream reach. These detailed guidance documents are useful resources to give the project team the deepest understanding of the science principles needed, plus provide EPA standard methods. The purpose of those documents in group b) is to provide some detail on how to apply in a TMDL setting. The additional principles described in this TMDL protocol document provide Minnesota’s guidance on applying these principles of low DO stream interactions to a TMDL project using stakeholder involvement and assessing the impairment at a watershed scale.

1. Handbook: Stream Sampling for Waste Load Allocation Applications. EPA Office of Research and Development. EPA/625/6-86/013. http://www.epa.gov/waterscience/library/modeling/streamsampling.pdf (PDF, 5M)

2. Technical Guidance Manual for Performing Waste Load Allocations: Simplified Analytical Method for Determining NPDES Effluent limitations for POTWs Discharging into Low-Flow Streams http://www.epa.gov/waterscience/library/modeling/npdeslowflow.pdf

(PDF, 2MB)

3. Establishing Total Maximum Daily Load (TMDL) Wasteload Allocations (WLAs) for Storm Water Sources and NPDES Permit Requirements Based on Those WLAs” (November 22, 2002); http://www.epa.gov/npdes/pubs/final-wwtmdl.pdf

4. Technical Guidance Manual for Developing Total Maximum Daily Loads: Book 2, Rivers and Streams; Part 1 Biochemical Oxygen Demand/DO and Nutrient Eutrophication, EPA/823/B-97-002 Year 1997 http://www.epa.gov/waterscience/tmdl/guidance.pdf

5. Water Quality Assessment: A Screening Procedure for Toxic and Conventional Pollutants in Surface and Ground Water, Part 1 [Revised]. EPA#: 600/6-85-002a YEAR: 1985. (PDF, 31MB) http://www.epa.gov/waterscience/library/modeling/wqascreenpart2.pdf

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B. Stressor Identification Overview Stressor Identification is a process that narrows the possible pollutants and sources down to the significant loadings using a formalized method. The process laid out in the EPA Stressor Identification guidance manual (see web link below) explains a logical process to:

(a) Select the right questions needing to be answered (information protocol), (b) Formalize the decision process steps, (c) Provide a predictability for the communication, information gathering, professional

judgment, and when a decision can be made; and (d) Require documentation of decisions in an organized fashion.

This process is meant to enhance traditional project decision processes rather than replace the current methods. The reader should consider the content of the following section and apply it to build on their own experience in project management. Ultimately, for impairments like dissolved oxygen, a parameter that is responding to a number of possible pollutant parameters and sources, the Stressor Identification tool chest is very useful in organizing the discovery process.

a. Stressor Identification Information Resources The United States EPA has developed a Stressor Identification Guidance document for biotic impairments that contains principles for investigation that are very useful in low DO studies. These principles are explained in different perspectives in the following guidance documents:

1. Stressor Identification Guidance Document; EPA-822-B-00-025, December 2000 http://www.epa.gov/ost/biocriteria/stressors/stressorid.pdf

2. Draft Handbook for Developing Watershed Plans to Restore and Protect Our Waters http://www.epa.gov/nps/watershed_handbook/#contents

3. MPCA TMDL Training Modules (to be) posted on the MPCA website

b. Definitions Stressor Identification (SI) is a term used by EPA guidance documents describing a process for use in biotic impaired waters that 1) develops a exhaustive list of potential physical and chemical parameters and the sources contributing to the impairment, and 2) provides an information flow and logic process that can narrow down the larger list of potential candidate stressors to those parameters and sources that are confirmed to be contributing or are considered to have a high potential of contributing to the impairment. Weight of Evidence, sometimes also called Strength of Evidence, is a term used to describe a process that settles on a decision when sufficient (circumstantial) justification exists, despite lack of hard science linking causal effects.

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Potential Sources is a term to identify all the possible pollutant loading sources in a given watershed that contain the potential candidate parameters. Primary Sources are those sources that are determined to be critical source loaders of the key stressor parameters to be allocated in the TMDL. Stakeholder Involvement refers to the levels of citizen communication during and after development of a draft TMDL. The communication can be one way or two way feedback depending on the level of effort applied or the timing in relation to the stage of development in the TMDL project. Examples of often used processes are: Stakeholder Advisory Committee is a citizen committee that is formed and evolves to include representation from the community in the potentially affected pollutant loading sectors, those interested in protecting water quality attainment and finally the Local Governmental Units (LGUs). The committee is not a final decision authority but has multiple purposes including identifying local early perceptions, identifying potential controversial issues, testing equity and reasonableness for individual sector expectations and total allocation applications and finally as a strong influence on the proper application of professional judgments being used during the project development. Technical Advisory Committee is a group of “experts” on watershed management or individual sector management that develop, review and adjust the assessment process while developing the TMDL. Public Meetings for the TMDL. Presentations announcing the project kick off or key findings of the TMDL project as an advertised event to reach out to citizens current not involved in the study. The meeting can set up selecting from many different formats, examples are: classroom style presentations, town hall style meetings, or more informal poster board displays with project team members available to discuss the issues. Public Notice of the TMDL. Presentation of the report, the public record documenting the findings and the logic process and/or the assessment process used in considering stressor parameters and the different sources resulting in the reduction expectations used development of the TMDL.

c. Stressor Identification Framework The SI process is meant to balance the needed information gathering effort, without having perfect information for cause and effect relationships. It is a strong means of reducing project costs and rigor by introducing a repeatable method for professional judgment decision-making. It begins with the current data or present understanding and uses the conversations of the project team and project committees, plus a data gathering process in an iterative fashion to evaluate the adequacy of the professional judgment being applied. The process uses the understanding, acceptance or comfort levels of the participants as an important consideration in finalizing a decision or revisiting the data or data gathering steps. There is a base assumption that there are areas of concern that reflect the greater community, and tends to be a good assumption when the committee membership is selected from a wide range of interests and not just the watershed restoration advocates. The decision process involves “starts and stops” as the project iterates between actively discussing the analysis or the need to gather more information to analyze. The project team’s watershed understanding will grow with each iteration of

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data collection and analysis steps. It is important to stress that the cycle and decision is not a total consensus vote, but instead a means to identify and influence the process. The following diagram is taken from the EPA Stressor Identification Guidance Document:

Figure 1. Stressor Identification Management Context

With regard to DO, the measurement of oxygen concentrations does not measure the pollutants contributing to the impairment. In the DO listings, the Stressor Identification process should be used to key into the appropriate sources that are driving the impairment by adding other pollutant parameters to the system. Therefore, the process started with the listing and the project team enters the diagram at the box that states “List Candidate Causes”. In the process, as a gap or an insufficiency occurs that limits a decision an iterative process is used as provided by the SI process to organize the conversations, planning task and data gathering tasks to revisit the issue at a later time with more information or to assign the decision an adequate margin of error and proceed on with the current understanding. The “Characterize Causes” box uses three categories of decision outcomes to process data: 1) Elimination, 2) Validation, and 3) Weight of Evidence. The first two categories are based on hard evidence such as: watershed monitoring indicating the lack of presence or presence of a stressor parameter that provide hard science conclusions that a parameter stressor is or is not a significant causal linkage. The third category is an effort that introduces and fosters a more formal “scientific hypothesis” process to develop significant circumstantial evidence to make a decision. By using the principals of

Dissolved Oxygen TMDL Protocols and Submittal Requirements

science to provide a relative comfort level for most involved parties based on indicators the weight of evidence approach becomes more defendable even though it continues to be based on professional judgment. The team must balance the spectrum of expending too much time and resources to gather information versus “pulling the decision out of the air.” Introduction of information from past research papers, using average literature values from technical publications, other local/regional site specific information, and alternative analysis methods (like GIS spatial analysis, simple analysis tools, statistics applications) will help balance the tension between wanting perfection and not pursuing anything further. The fear of decisions being “pulled out of the air” is minimized by a decision made on professional judgment being based on many indicators to be organized by using the defendable documentation from the stakeholder groups weight of evidence process that support the decision. There are many possible ways of gathering information and filtering the information into watershed understanding. The craft or art behind the weight of evidence processes is selecting which data gathering processes will be used to substantiate the decision. The final decision-maker is influenced by type of data, when the data is an indicator (circumstantial evidence), then the opinions of the two committees on the subject. Options available or not available for further investigations are also considered (i.e., is the weight of evidence strong enough to make a decision as to its significance or not – and then require more information and a next step, or explore the margin of error and related MOS to manage the resources and TMDL progress). The decision is represented by the process represented in the SI Management Context diagram, Figure 1; however the key location to note is between the “Analyze Evidence” box and the “Characterize Causes” box as shown in Figure 2. There are 5 possible results resulting from analysis of the evidence available. Figure 2. A subset of Figure 1. SI Management Context

Eliminated: Data set confirms elimination finding and project documents the parameter stressor or source as a noncontributing factor in the watershed.

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Or,

Figure 3. A subset of Figure 1. SI Management Context

Validated: Data set confirms the stressor parameter is present and significant, or that a source contributes to the significant stressor parameter loading in the watershed and allocations are required.

Or, Figure 4. A subset of Figure 1. SI Management Context

Weight of Evidence: Sufficient indicator evidence is present to use the Weight of Evidence justification to move forward in the project with adequate minimization of risks.

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Or, Figure 5. A subset of Figure 1. SI Management Context

As the decision makers find there is not enough information to follow any of the three category steps, the project plans for more information gathering and returns back into the analyze evidence box with new data to repeat the process. [Over time, the teams working in the Impaired Waters program will develop more confidence with each project and be able to manage risk based on program wide experience.] A similar iterative process is done with the pollutant source information available in the watershed. This should be done early and be in step with the pollutant stressor iterative loop. In this case, the land use or channel assessment focuses on sources that have the key pollutant stressor parameters and the key limiting physical parameters. Again, hard evidence like permit information, including NPDES DMR reports, ambient monitoring combined with spatial assessments (for instance determination of no hydrologic connection) can be used to validate or eliminate sources. Other indicators such as presence in a subwatershed, timing, literature estimates of magnitude, or detailed modeling can create sufficient weight of evidence to make allocation decisions. Remember that it is just as important to document and communicate why a source is eliminated as it is to set reduction goals for a source that is validated or pursued using strength of evidence. All projects using this process benefit from starting with simple data sets and graduating to more complex efforts only as needed. Other benefits are:

Cost savings, Documentation of findings and decisions, Flexibility in project flow, yet with consistent logic on how, when and where to use the iterative

information collection process, and More acceptance from program staff and watershed participants that the risks are minimized and

reasonable solutions are being selected.

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Dissolved Oxygen TMDL Protocols and Submittal Requirements

C. Stream Health and DO DO is an important water quality indicator parameter for the protection and management of aquatic ecosystems. All higher life forms such as vertebrates and macroinvertebrates are dependent on minimum levels of oxygen for critical life cycle functions such as growth, maintenance, and reproduction. Problems with oxygen depletion in river systems are often the result of excessive loadings of carbonaceous biochemical oxygen demand (CBOD) and nitrogenous biochemical oxygen demand (NBOD), particularly in combination with high temperature and low flow conditions.

a. Definitions

Algal Respiration: Process in which organic carbon biomass is oxidized to carbon dioxide, produced from within the algal organism. Ambient Water Quality: Natural concentration of water quality constituents prior to mixing of either point or nonpoint source load of contaminants. Reference ambient concentration is used to indicate the concentration of a chemical that will not cause adverse impact to human health. Ammonia: Inorganic form of nitrogen; product of hydrolysis of organic nitrogen and denitrification. Ammonia is preferentially used by phytoplankton over nitrate for uptake of inorganic nitrogen. Anaerobic: Environmental condition characterized by zero oxygen levels. Describes biological and chemical processes that occur in the absence of oxygen. Anoxic: Aquatic environmental conditions containing zero or little dissolved oxygen. Anthropogenic: Pertains to the (environmental) influence of human activities. Assimilative Capacity: The amount of contaminant load (mass per unit time) that can be discharged to a specific stream or river without exceeding water quality standards or criteria. Assimilative capacity is used to define the ability of a waterbody to naturally absorb and use waste matter and organic materials without impairing water quality or harming aquatic life. Background Levels: Background levels represent the chemical, physical, and biological conditions that would result from natural geomorphological processes such as weathering or dissolution. Benthic: Refers to material, especially sediment, at the bottom of an aquatic ecosystem. It can be used to describe the organisms that live on, or in, the bottom of a waterbody. Bed Material: The moving sediment mixture that is present on the channel floor. Bias: A systematic error introduced into sampling or testing by selecting or encouraging one outcome or answer over others. Bias can be introduced by setting variables or factors which would result in one outcome.

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Boundary Conditions: Definition or statement of conditions or phenomena at the boundaries. Water levels, flows, concentrations, etc., that are specified at the boundaries of the area being modeled. Calibration: Adjustment of a model’s parameters such as roughness or dispersion coefficients so that it reproduces observed prototype data to acceptable accuracy. Carbonaceous Biochemical Oxygen Demand (CBOD): The amount of oxygen required by bacteria to oxidize organic carbon material to carbon dioxide (its lowest energy state). Deterministic Model: Mathematical model in which the behavior of every variable is completely determined by the governing equations and the initial states variables. Detritus: Any loose material produced directly from disintegration processes. Organic detritus consists of material resulting from the decomposition of dead organic remains. Discharge Monitoring Report (DMR): Report of effluent characteristics submitted by a municipal or industrial facility that has been granted an NPDES discharge permit. Dissolved Oxygen Sag: Longitudinal variation of dissolved oxygen representing the oxygen depletion and recovery following a waste load discharge into the water. Diurnal: Actions or processes having a period or cycle of approximately completed actions within a 24-hour period and which recur every 24 hours. Dye Study: Use of conservative substances to assess the physical behavior of a natural system. Effluent: Municipal sewage or industrial liquid waste (untreated, partially treated or completely treated) that flows out of a treatment plant, septic system or pipe, etc. Empirical Model: Representation of a real system by a mathematical description based on experimental or observed data rather than on general physical laws. Hydrograph: A graph showing variation in stage (depth) or discharge of water in a stream over a period of time. Hydrologic unit: A geographic area representing part or all of a surface drainage basin or distinctive hydrologic feature as delineated by the Office of Water Data Coordination on State Hydrologic Unit Maps; each hydrologic unit is identified by an eight-digit number code (HUC). Low Flow (7Q10): Low-flow (7Q10) is the 7-day average low flow occurring once in 10-years; this probability-based statistic is used in determining stream design flow conditions and for evaluating the water quality impact of effluent discharge limits. Nitrogenous Biochemical Oxygen Demand (NBOD): The amount of oxygen required by bacteria to oxidize ammonia to nitrite, and then nitrite to nitrate (the process is called nitrification).

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One-Dimensional Model: Model defined with one space coordinate, i.e., variables are averaged over the other two directions. Parameter: A chemical or physical property whose value determines the characteristics or behavior of something. Probabilistic Model: Mathematical model in which the behavior of one or more of the variables is either completely or partially subject to probability laws. Qualitative: A relative assessment of quantity or amount. Quantitative: An absolute measurement of quantity or amount. Sediment Oxygen Demand (SOD): Combination of several processes, primarily the aerobic decay of organic materials (such as leaf litter, particulate BOD in wastewater discharges, or algae or plant biomass) that have settled to the bottom of the stream bed. Total Kjeldahl Nitrogen (TKN): The total of organic and ammonia nitrogen in a sample, determined by the Kjeldahl method. Ultimate Biochemical Oxygen Demand (UBOD or BODU): Total oxygen consumed by carbonaceous and nitrogenous material or the amount of oxygen required to oxidize organic carbon and ammonia nitrogen. The value is typically estimated by a 40 or 70 day BOD test. Watershed: A topographically defined area drained by a river/stream or system of connecting rivers/streams such that all outflow is discharged through a single outlet. Also referred to as a drainage area. b. DO Chemical and Physical Stressor Parameter Interactions The amount of oxygen that a given volume of water can hold is a function of atmospheric pressure, water temperature, and the amount of other substances dissolved in the water. At sea level, fresh water can absorb more oxygen per volume than water at mountainous elevations because of the higher atmospheric pressure near sea level. Cool water can hold more oxygen than warm water. Water with high concentrations of dissolved minerals such as salt will have a lower DO concentration than fresh water at the same temperature. When water can no longer absorb more oxygen at a given temperature, pressure, and dissolved solids content, it is said to be saturated with DO (or 100% saturation). Unlike air, which is normally about 21% oxygen, water contains only a tiny fraction of a percentage of DO. Oxygen dissolved in water is usually expressed in milligrams per liter (mg/L), parts per million (ppm), or percent of saturation. At sea level, typical DO concentrations in 100% saturated fresh water will range from 7.56 mg/L (or 7.56 parts oxygen in 1,000,000 parts water) at 30 degrees Celsius to 14.62 mg/L at zero degrees Celsius. The saturation concentration decreases about 3.5% for every 1000 feet increase in elevation.

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Reference: Bowie, G.L., Mills, W.B., et al. 1985. Rates, Constants, and Kinetics Formulations in Surface Water Quality Modeling (Second Edition). Environmental Research Laboratory, Office of Research and Development, U.S. Environmental Protection Agency. EPA/600/3-85/040. June 1985.

At any given time, the concentration of DO in a riverine environment is dynamic and influenced by the interaction of physical, chemical, and biological factors. By accounting for factors affecting DO, a mass balance model is often used to help quantify the important components of a low DO problem in the river. Figure 6, schematically depicts a segment of stream and the major factors affecting the balance of DO within the water column.

DissolvedOxygen

Algae:•Phytoplankton•Periphyton

Other Aquatic Plants

Photosynthesis

Respiration

NH4+ NO2

- NO3-

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Sediment O 2

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(Reaeration)

Atmospheric Oxygen

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Conditions

• DO• BOD• VSS• Algae

• Volume• Depth• Velocity

CBOD: Carbonaceous Biochemical Oxygen Demand. The rate of oxygen consumption from carbon available for bacterial decay processes and the amount of oxygen bound in chemical reactions. NBOD: Nitrogenous Biochemical Oxygen Demand. The rate of bacterial transformation of ammonia into nitrite and then nitrate consuming oxygen with each step. SOD: Sediment Oxygen Demand. Depositions on the stream bed consisting of organic material originating from external sources, such as leaf litter or particulate BOD in wastewater discharges, or algae and other plant biomass, decomposing and creating a sediment oxygen demand

Water Surface

Stream Bed

Figure 6. Stream DO Balance

Dissolved Oxygen TMDL Protocols and Submittal Requirements

c. External Influences The factors external to a specific river segment that affect DO include the atmosphere-water interface, the streambed-water interface, the upstream water quality conditions, and pollutant loadings directly to the segment. Whenever the water column DO concentration is less than saturation, there is a net transfer of atmospheric oxygen into the water in a process called reaeration. The rate of atmospheric reaeration is a function of the magnitude of the DO deficit in the water column, atmospheric pressure, temperature, wave action, and water turbulence. A shallow, turbulent stream has a higher rate of reaeration than does a deeper, quiescent stream. On occasion, rivers can become supersaturated with oxygen due to the photosynthetic production of algae and plant matter, in which case there is a net loss of oxygen from the water to the atmosphere. Ground water, a primary source of river flow during dry weather and base flow conditions, is naturally low in DO. During winter months when ice coverage inhibits atmospheric reaeration, ground water inflows will contribute to occurrences of low DO in a river. During summer, the cooler ground water inflow may at first lower the DO concentration, but it also tends to reduce the river temperature which improves the ability of the water to hold oxygen. Ground water introduces dissolved materials into surface waters, such as minerals related to hardness, but generally has low concentrations of oxygen demanding organic substances. Ground water inflow to streams in agricultural regions may be high in inorganic nitrate-nitrogen. Nitrate is not an issue for stream DO, but it can be problematic for downstream uses of surface water as a source of drinking water. The quality of water at an upstream boundary reflects the pollutant loads from upstream sources and tributaries in the watershed. Affected by natural and anthropogenic factors, this headwater quality may exert a large influence on the DO balance of a downstream river segment. Natural characteristics such as lakes or wetlands affect downstream water quality much differently than does a typical riffle-pool run of river. Human influence is evidenced by physical alterations such as dam construction, by point source discharges from municipal and industrial wastewater treatment plants, storm water runoff from urban areas, and nonpoint loadings from agricultural areas. Direct discharge of pollutants from point source and nonpoint sources into a subject river segment add to its CBOD and NBOD loadings, creating an oxygen demand that may depress DO below acceptable concentrations. Nutrient levels can occasionally, in certain rivers, cause sufficient eutrophication to generate CBOD loads from decaying algae. This may not occur locally, but instead further downstream in pools where the velocities slow and the algae population collect. Once identified, these source loads become prime candidates for allocation within a TMDL plan. d. Internal Influences The DO present within a river segment at any point in time is dependent upon a delicate balance between the physical, chemical, and biological sources and sinks of oxygen interacting within the segment. Sources of oxygen are atmospheric reaeration, mass transport into the segment from upstream and ground water, and the photosynthetic production by algae and aquatic plants. Pathways, or sinks, for oxygen loss to the segment include the biochemical oxidation of suspended and dissolved organic waste material, oxygen demands from settled organic and inorganic materials, respiration of aquatic plants and animals, and the conversion of nitrogen forms through biological nitrification.

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When oxygen is consumed or otherwise lost at a greater rate than it is being replenished within a river segment, then the resultant DO concentration declines. Figure 7 illustrates the theoretical response of DO in a flowing river to a continuous point source load of BOD.

0

2

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8

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-1 1 3 5 7 9 11 13

River Miles

mg/L

BOD

DO

Cs

Organic Load

Cs = D.O. Saturation

The classical “sag” or DO response that is observed downstream from a point source discharge results from the increased respiration of the natural bacteria population in a flowing river that grows in response to its increased food source of organic matter from the discharge. As the river moves downstream the organic food source is decomposed by the bacteria and becomes depleted. With its food supply gone, the bacteria die off and river DO recovers to the natural background level. In another case where nonpoint sources of BOD are loading the river system over a broad area, the spatial extent of DO depression may be more extensive. Typical nonpoint source sag curves could be either a flatter curve with no visible recovery or a series of smaller sag curves indicating new loading sources interfering with the previous curves recovery. Both conditions are presented, though not to scale in Figure 8, below.

Figure 7. Stream DO Response to a Point Source Discharge

Dissolved Oxygen TMDL Protocols and Submittal Requirements

Figure 8: DO sag curve from multiple pollutant loadings along a reach from nonpoint sources (response not modeled or to scale; example only)

0

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8 mg/L

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River Miles

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PS & NPS Organic Loads

Cs = D.O. Saturation

BOD

The oxygen demand exerted by benthic sediments (on the stream bed) can represent a significant oxygen sink in some rivers. Benthal deposits result from the deposition of organic material originating from external sources such as leaf litter or particulate BOD in wastewater discharges, or it may be generated within the river system as algae and other plant biomass. The decomposing organic material creates a sediment oxygen demand (SOD) that may become localized and more significant at given locations in a river system such as in the deeper pooled regions. The photosynthetic oxygen production (a source) and respiration (a sink) associated with aquatic plant life are important factors in the DO balance of natural waters. Of special concern are situations with an overabundance of free floating algae (phytoplankton), attached algae (periphyton), or larger submerged or emergent aquatic plants (macrophytes). The extent to which aquatic plant life impacts the oxygen resources of a water body is dependent on factors such as light availability and light intensity as well as an adequate supply of nutrients essential for growth. Photosynthetic rates respond to variations in sunlight intensity and water turbidity, which can decrease light transmittance through the water column. The diurnal variations observed in oxygen concentrations result from a net photosynthetic oxygen production during daylight hours and a net consumptive loss from plant respiration during the evening and night. When algae or plant densities are high, large diurnal swings in DO can occur with peak concentrations during the day exceeding 100% saturation and nighttime minimum concentration well below saturation. An idealized diurnal stream response for DO is shown below in Figure 9. Typically, the daily minimum

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Dissolved Oxygen TMDL Protocols and Submittal Requirements

DO occurs within the first two hours after dawn. The daily maximum normally occurs in late afternoon, about three to five hours after noon.

Figure 9: Diurnal Dissolved Oxygen response to photosynthetic cycles

Idealized Diurnal Dissolved Oxygen (DO) Curve Mid-Summer

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Sunrise

Sunset

Highly eutrophic conditions can occur at times in nutrient-enriched rivers, usually during low flow conditions when increased hydraulic residence times are favorable to producing a large standing crop of algae. These periods of active plant growth and respiration are marked by large diurnal fluctuations in DO. When river or meteorological factors change to less favorable growth conditions, algae and aquatic plants will die, decompose, and use up oxygen resources. Algal biomass, a potential BOD load, can be transported miles downstream and create oxygen deficits in critical reaches. Algal oxygen production followed by respiration and later death and decay create a magnified amplitude in the diurnal response curves as shown below in Figure 10.

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Figure 10: Diurnal Dissolved Oxygen response to photosynthetic cycles comparison with eutrophic systems

Idealized Diurnal Dissolved Oxygen (DO) Curve Mid-Summer

0.0

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Sunset

Where a source of ammonia-nitrogen and a viable population of nitrifying bacteria are present in natural waters, the bacteria oxidize ammonia to nitrite, and then nitrite to nitrate in a process called nitrification. Ammonia sources may be external, such as from sewage discharges and animal feedlots, or ammonia can be released internally within the system from the process of organic nitrogen decay (ammonification). While nitrifying bacteria may be present in the water column, nitrification occurs primarily in the sediment bed. Nitrification by attached bacteria is more likely to be of significance in relatively shallow, wide rivers having a stable bottom substrate (see Water Quality Assessment: A Screening Procedure for Toxic and Conventional Pollutants in Surface and Ground Water, Part 1). The nitrification of ammonia to nitrate is important to the oxygen resources of a stream because up to 4.6 parts of DO are consumed for each part of ammonia converted. Water temperature is an important physical parameter that not only establishes the maximum oxygen-holding capacity of water, but also has direct influence on rates of biochemical reactions and transformation processes occurring within the water column and in the sediment bed. Warmer temperatures decrease oxygen solubility in water while at the same time increasing metabolic rates that affect BOD decay, sediment oxygen demand, nitrification, photosynthesis, and respiration. In Minnesota, the critical conditions for stream DO usually occur during the late summer season when water temperatures are high and stream flow rates are normally low. The following figures, Figure 11 and Figure 12, relate physical stream riparian corridor vegetation differences that affect critical shading and resulting water temperatures.

Diurnal response curve in a more eutrophic system

Dissolved Oxygen TMDL Protocols and Submittal Requirements

Figure 11: A stream reach without vegetative shade.

In the stream pictured above the riparian area exists without shade as result of intensive livestock traffic and little to no slopes in land. The wide shallow stream with raised temperatures due to lack of vegetation canopy over significant areas of the stream represent aspects in the watershed that might lend themselves to opportunities for improved DO.

Figure 12: A wide stream with no riparian slopes with significant tree shade.

Gentler land use in the riparian corridor combined with a natural forested area provides for lower temperatures as more of the stream surface area is shaded.

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When a pollutant load enters a flowing body of water, it is subject to fate and transport processes that modify its concentration. Organic loads are subject to chemical, biological, and biochemical reactions that attenuate the material by degradation into stabile end products such as carbon dioxide, nitrate, and water. However, a pollutant load of oxygen-demanding organics that is large enough to overwhelm the oxygen resources of a water body creates an imbalance that destabilizes the stream environment and leads to aquatic life impairments. An important task for TMDL managers is to understand the cause-effect relationships that govern DO in site-specific situations in order to design and implement a successful remediation strategy for their impaired waters. Water quality parameter interactions and other factors affecting DO can range from the obvious to the complex. Although the basic principles affecting the DO balance in a stream are constant, each impaired reach has a unique set of factors contributing to its impairment. These contributing factors may be naturally occurring or human-induced, internal or external to the impaired reach, may be seasonal in nature, or some combination thereof. For example, an impaired trout water on the North Shore of Lake Superior will have a set of contributing factors much different from an impaired headwater creek in southern Minnesota. The northern trout stream may suffer from watershed disturbances due to urbanization and the loss of riparian vegetation that once provided shade to cool the stream. The southern creek may be impacted by agricultural nonpoint loadings as well as hydrological changes from past practices of artificial drainage in the watershed. A small, first order stream will be more sensitive to an external pollutant loading input than will a larger, third or fourth order stream. The natural setting, stream morphology, and flow regime also play large roles in the reaeration and oxygen capacity of a stream. For example, a stream reach directly downstream from a wetland complex may reflect the naturally low DO concentrations found in wetlands. A shallow, high gradient turbulent stream has better inherent reaeration potential than does a low gradient, sluggish stream with deep pools. Under conditions of low stream flow, a normally well-aerated stream with alternating riffles and pools may be reduced to mostly stagnant pools having low oxygen levels. Therefore, any analysis of DO impairment must recognize and acknowledge these types of physical constraints that are imposed by the natural characteristics of a watershed on its riverine system. e. Stressor Sources on Streams A given stream watershed has multiple sources of pollutants or physical features that affect the stream loading capacity. These can be subdivided into human induced (anthropogenic) and natural or background sources. Further social or political subdivisions exist to address human induced categories, such as those regulated by the National Pollutant Discharge Elimination System (NPDES) permit program, which controls water pollution by issuing permits that regulate point sources that discharge pollutants into waters of the United States. Those sources with a more diffuse nature like forestry logging or agriculture row cropping are sometimes supported by programs to assist in funding actions like soil conservation or better site planning. Anthropogenic (human induced activities) Permitted pollution sources: the Clean Water Act has recognized several types of discharges from known sources to at a potential strength of oxygen demanding substances that a National Discharge Elimination System (NPDES) permit is required. The Chapter 40 Code of Federal Regulations Section 130 (40 CFR 130) dealing with the TMDL program requires all NPDES sources to be handled in the

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wasteload allocation portion of the TMDL allocation. However, not all NPDES sources have the same measures or controls placed on them in the TMDL process NPDES types: Industrial Process wastewater and Domestic Wastewater Treatment Facilities. These types of facilities have a technology based effluent limit (TBEL), routinely called “secondary treatment” in domestic facilities, of 25 mg/l five day Carbonaceous Biochemical Oxygen Demand (CBOD5) and 30 mg/l Total Suspended Solids (which in small part are undigested organic matter that was not captured in the clarifiers) for general protection of healthy rivers and streams. Some facilities may have older technology such as trickling filters and have a 40 mg/l CBOD5 limit. However, the TMDL is an assessment that defines water quality based effluent limits (WQBEL) to achieve beneficial use protection. Tertiary treatment limits in Minnesota are as low as 5 mg/l CBOD5. But limits this low are attained with a high cost associated with the treatment plant construction and operation. These point sources also have the potential to, and most often do discharge nitrogenous sources of oxygen demanding material like TKN. Some also may have a temperature impact and/or a nutrient enriched wastewater. Any of these potentially are contributing to lower dissolved oxygen levels as a direct source of oxygen demanding material, as a catalyst, or by increasing eutrophication. Domestic wastewater: Includes municipal wastewater treatment plants and other privately owned plants. Minimum secondary treatment requirements are applicable for domestic wastewater facilities where there is enough available dilution in the receiving water to assimilate the waste and maintain water quality standards. The TBEL limits include 25 mg/L CBOD5 and 30 mg/L TSS. Equivalent secondary treatment limits of 40 mg/L CBOD5 and 45 mg/L TSS may be applicable for some older trickling filter facilities that meet certain criteria, as long as water quality standards are maintained in the receiving water. When receiving water flow is low and dilution is not adequate, WQBEL applications may require advanced wastewater treatment CBOD5 limits as stringent as 5 mg/L CBOD5, with seasonal ammonia nitrogen limits applicable on a site-specific basis. Industrial wastewater: Includes multiple manufacturing wastes or processing wastes, such as in the food industry. The strength of the raw wastes can be from very light loading concentrations, such as from noncontact cooling water (but with high temperatures which affect streams), to very concentrated raw wastewater organic loads such as from food processing facilities. Federal categorical (industry specific – best technology economically possible – established by USEPA) or technology based discharge limits are assigned except where water quality based limits are more stringent. Feedlots. In Minnesota Confined Animal Feeding Operations over 1,000 animal units must have a NPDES permit. Minnesota stipulates in this type of permit: a zero discharge from the animal production area; manure application set back restrictions from open water and/or tile intakes; and cropping nutrient management requirements. These manure management requirements are sufficient to classify the manure as agricultural stormwater runoff and not a NPDES discharge. Stormwater Permits: Municipal Separate Storm Sewer Systems (MS4s), Construction Stormwater and Industrial Stormwater. These types of permits may contain pollutants such as CBOD5, nitrogenous oxygen demanding materials, nutrients, and may have the additional issue of raised temperature due to stormwater ponding or heated impervious surfaces. In a November 2002 EPA policy memorandum discussing how the Stormwater Programs and the TMDL programs will interact, the EPA acknowledged that this type of permitted source acts most like other nonpoint source types, and not a wastewater

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Dissolved Oxygen TMDL Protocols and Submittal Requirements

discharge of constant volume and concentration makeup. Due to this variability, the memorandum further defines that it is desired that individual allocations be made for permits when possible, but it is also acceptable to group multiple permits geographically or by type when the assessment can not distinguish between multiple stormwater permits. The memorandum further explains that concentration effluent limits will not typically be applied in the permit’s Stormwater Pollution Prevention Plan, but TMDL mass wasteload allocations will be met most often through implementation of BMPs. Reservoirs and hydropower dams: Hydropower facilities are licensed by the Federal Energy Regulatory Commission (FERC). Hydropower licenses last from 30 to 50 years and typically stipulate how the dams are operated, what minimum water flow levels are required, what forms of fish passage must be installed and, in some cases, how watershed lands are managed. Well before (often 5 years) a license expires, the dam owner must apply to FERC for a new license. The relicensing process allows FERC, state and federal resource agencies, conservation groups, and the general public to reconsider appropriate operations and land management for each project, taking into account current social and scientific knowledge. If release water is from the bottom of the reservoir and the water is stratified there is the potential for low DO concentrations downstream. If hydropower turbines appropriate a substantial percentage of flow during low flow periods, and are withdrawing water from the lower portion of a stratified water column, the facility may be discharging water with low DO concentrations. Spilling through the gates or over the dam during low flows will provide aeration and increase DO concentrations while not detracting significantly from power generation. Parameters of Concern for NPDES sources: CBOD, NBOD, suspended solids, temperature, nutrients.

Water withdrawal permits

Department of Natural Resources Water Appropriation Permits; Regarding Dilution Ratios. A Minnesota Department of Natural Resources (MDNR) water use permit is required for all users withdrawing more than 10,000 gallons per day or one million gallons per year. In order to safeguard water availability for natural environments and downstream higher priority users, Minnesota law requires MDNR to limit consumptive appropriations of surface water under certain low flow conditions. Additional detailed information may be found at http://www.dnr.state.mn.us/waters/watermgmt_section/appropriations/permits.html

• A river or stream ecosystem is often times most stressed during low flow, late summer conditions. These warm temperatures and slow moving waters limit not only the amount of oxygen that can be held in the water column, but also limit the natural sources or reaeration that would further benefit the stream. Permit effluent limits are developed based on the 7-day average, 10-year return low flow (7Q10) events of the stream and the dry weather design flow of the wastewater treatment facility. Experience with numerous cases indicates that if the stream-to-effluent dilution drops below a 10 to 1 ratio, the strength of waste will not be adequately assimilated by the stream’s natural processes. Proper periods of allowed withdrawals must be considered regarding low flows.

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(a) Nonpoint source loadings. Human activities on landscapes that increase either the mass or the concentrations of pollutants associated with runoff can contribute stressors to dissolved oxygen levels. An incomplete list of example sources of anthropogenic nonpoint source loading includes: nonpermitted stormwater from small towns or unincorporated areas; smaller permitted feedlots; row crop agriculture; intensively grazed areas with or without livestock exclusion provisions; peat mining; forestry harvest sites; and domesticated animals, like house pets or hobby farms. (1) Common Anthropogenic Nonpoint Source Types

(i) Landuse conversions 1. Small feedlots. Smaller feedlots may have a permit, or be considered to be

not connected with surface waters, and therefore not require a State Disposal System Permit. Small feedlots sometimes may have treatment systems that allow a direct discharge to surface.

2. Stormwater Runoff. Small communities, roads and unincorporated developed areas most likely contribute increased runoff and concentrations of pollutants, similar to MS4s. However, they do not always have administrative oversight from a NPDES permit or a Local Unit of Government.

3. Forestry Harvest Sites. Forested areas can have a very gentle presence on the land and typically are one of the best watershed landscapes regarding water quality. However, forestry harvests can be very disruptive during the clearing process by introducing heavy equipment traffic, removal of vegetation and the associated rutting and road construction. While most of these events can be short-lived, the road construction and staging areas can have longer term impacts.

4. Row Cropping. Agricultural row cropping can be a very intensive land use which disturbs the vegetative cover twice a year and introduces higher concentrations of nutrients and pesticides. Typical runoff concentrations of sediment and sediment associated pollutants can be up to 10 times higher than if the land was grassed or forested.

5. Pastured and Hayed lands. These lands provide a more gentle footprint, acting like a more natural setting. However, livestock grazing in or along a stream or river and manure application to the hay may create a scenario similar to small feedlot concerns. The historic intensity of grazing can be indirectly determined by the types of forage present on the site. Presence of Kentucky Blue Grass, other short grasses, or areas completely devoid of vegetative cover indicate higher livestock pressure.

• Parameters of Concern: CBOD, NBOD, Sediment, Nitrogen, Phosphorus and higher temperature.

(2) Common watershed physical changes (i) Stream alterations: The changes on a natural stream’s form and functions can

directly impact one or more potential stressors of dissolved oxygen. The following is an incomplete list of alterations and a short description of the stress.

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1. Riparian Landuse Efforts to make the riparian landuse more productive result in several limiting features: loss of shading, higher temperature runoff, less infiltration and therefore less cool groundwater recharge back into the stream, disconnecting the stream from the flood plain terrace and potentially creating a unstable channel.

2. Dams and Reservoirs Many reservoirs placed in a riverine setting can create pools which affect eutrophication, pH, temperature, ammonia levels, reduced surface turbulence and therefore less aeration.

3. Channelization and dredging Stream straightening and deepening can reduce the streams physical ability to provide aeration back into the water column. Changes result in a range of impacts from stagnation (creating an ephemeral stream where there was an intermittent stream), higher temperatures, loss of riffles and runs (beneficial for re-entraining oxygen) and poorly managed or outright loss of riparian area woody vegetation (beneficial shading). A channelization project upstream of the resource also affects peak flow events and can begin to destabilize the channel.

4. Agricultural Drainage Tile Subsurface tile can be a direct connection for pollutant sources that were previously remotely located in the watershed. For soluble parameters, interception and direct transport to the stream or ditch is enhanced. For sediment and sediment attached parameters, higher delivery ratios can occur when surface tile intakes are present. These systems can also alter the 1 ½ to 2 year frequency flows, which determine a stream’s bankfull flow, thus destabilizing the channel and kicking off a channel evolution process. Under certain circumstances frost can seal the soil pores and sufficient soil bacteria activity can then create an anaerobic environment, which results in by-products such as ammonia.

• Parameters/stressors: Flow, temperature, reaeration, sediment, nutrients and organics

(3) Cultural Eutrophication Over-enriched sources of nutrients can create a nutrient to plant (algal or weeds) production for oxygen demanding materials through a lifecycle process. Also, too many weeds can lessen the turbulence in a stream and reduce the reaeration process. (i) High nutrients (phosphorus, nitrogen) can directly create a shift in the ecosystem

where boom and bust life cycles create a collection of biomass in slow velocity reaches, which become available for bacterial decay processes using higher than normal levels of dissolved oxygen.

(ii) Plant cell wall decomposition from natural or human induced alterations in wetland hydrology. For instance disturbances that access high organic materials previously sequestered are: ditching through wetlands, peat mining, and abnormally heavy traffic from short term site use, such as from logging, can create rutting which flushes or creates a flow blockage of parts of wetlands.

• Parameters phosphorus, nitrogen, organic detritus, diurnal fluctuations in dissolved oxygen (excessive high to low daily results).

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Dissolved Oxygen TMDL Protocols and Submittal Requirements

(4) Natural: Many of the conditions described above occur naturally in the environment; some at a reduced rate where the stream dissolved oxygen balance can be brought back into compliance, and some at a rate that always held a reach out of compliance, such as below a large wetland complex with high organic decay and little natural aeration capability.

(i) Groundwater recharge to the stream Groundwater coming into a reach may be doing so with little or no dissolved oxygen present. An isotopic survey of the stream and groundwater can be done to compare the ratio of dilution occurring.

(ii) Riparian and Backwater Interactions Large sources of stagnate water with low dissolved oxygen, or water with a high detritus content, can be flushed into a stream under certain flow conditions.

(iii) Winter Ice Cover Winter ice cover can limit the amount of reaeration that occurs. When this is combined with oxygen demanding material loadings from eutrophication or point sources (for instance), winter low dissolved oxygen levels can develop.

• Parameters: organic, low DO water causing dilution, nutrients, pH

D. Problem Definition a. Applicable Water Quality Rules Water quality standards are fundamental tools that help protect Minnesota’s abundant and valuable surface and ground water resources. The comprehensive Clean Water Act amendments of 1972 require states to adopt water quality standards that meet the minimum requirements of this federal law. Minnesota’s water quality standards meet or exceed federal requirements. The federal Clean Water Act also requires all states to review and revise where necessary their water quality rules every three years. Water quality standards should be updated periodically to reflect the latest scientific information. Water quality standards and related provisions are found in several Minnesota rules, but the primary rule for statewide water quality standards is Minn. R. Ch. 7050. Included in this rule are:

A classification system of beneficial uses for both surface and ground waters Numeric and narrative water quality standards Nondegradation provisions Provisions for the protection of wetlands Treatment requirements and effluent limits for wastewater discharges Other provisions related to the protection of Minnesota’s water resources from pollution.

Water quality standards generally include the following components:

• Beneficial uses – identification of the uses our water resources provide to people and wildlife. • Numeric standards – allowable concentrations of specific pollutants in a waterbody, established

to protect the beneficial uses.

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Dissolved Oxygen TMDL Protocols and Submittal Requirements

• Narrative standards – statements of unacceptable conditions in and on the water. • Nondegradation – extra protection for high-quality or unique waters.

“Beneficial uses” are the uses that states decide to make of their water resources. The process of determining beneficial uses is spelled out in the federal rules implementing the Clean Water Act. Seven beneficial uses are defined in Minn. R. 7050.0200. These uses and the use-class designations are listed below. The class numbers 1–7 are not intended to imply a priority ranking to the uses.

Class 1 - Drinking water Class 2 - Aquatic life and recreation Class 3 - Industrial use and cooling Class 4A - Agricultural use, irrigation Class 4B - Agricultural use, livestock and wildlife watering Class 5 - Aesthetics and navigation Class 6 - Other uses Class 7 - Limited Resource Value Waters All surface waters are protected for multiple uses:

o Most are Class 2 – protected for aquatic life and recreation o Some are Class 7 – Limited Resource Value Waters

Both Class 2 and Class 7 waters are protected for: o Class 3 – Industrial uses o Class 4 – Agriculture and wildlife uses o Class 5 – Aesthetics and navigation o Class 6 – Other uses

In addition, some surface waters are also protected for drinking (Class 1) The vast majority of surface waters in Minnesota are Class 2, protected for aquatic life and recreation. Limited Resource Value Waters are protected for very limited aquatic community and recreational uses. Each Class 7 waterbody has been individually assessed and the change from Class 2 to Class 7 adopted into Minn. R. 7050.0470. Most Class 7 waters are headwater streams or channelized ditches that provide poor aquatic habitat due to low flows and/or channel alterations. Class 7 reaches range from less than one to about 20 miles in length, and all together make up about one percent (~ 900-950 miles) of Minnesota’s 92,000 miles of rivers and streams.

Subclasses. Use classes 1, 2, 3 and 4 have subclasses. Of these, the Class 2 subclasses are the ones most people should be familiar with; they are listed below:

2A Cold-water fisheries, trout waters, also protected as a source of drinking water 2Bd Cool- and warm-water fisheries, also protected as a source of drinking water 2B Cool- and warm-water fisheries (not protected for drinking water) 2C Indigenous fish and associated aquatic community (not protected for drinking water) 2D Wetlands (not protected for drinking water).

b. Numeric standards Numeric water quality standards represent safe concentrations in water that protect a specific beneficial use. If the standard is not exceeded, the use should be protected. Minnesota R. Ch. 7050 has numeric

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standards designed to protect drinking water, aquatic life and recreation, industrial, agricultural, aesthetic and wetland uses, and Limited Resource Value Waters. In general, the numeric standards used most often to protect surface waters are the Class 2 aquatic life and recreation standards. And, with a few notable exceptions (e.g., the Class 3B chloride standard and the Class 4A sulfate standard), if the Class 2 standards are met, the other usually “less sensitive” uses are protected as well. Most of Minnesota’s aquatic life (Class 2) standards are based on EPA aquatic life criteria. The EPA develops and publishes the criteria as required by the Clean Water Act

Numeric standards are listed in two places in Minn. R. Ch. 7050. First, all the numeric standards applicable to four common categories of surface waters are listed in Minn. R. 7050.0220. For example, all the standards applicable to trout waters, and their associated uses (including the drinking water standards), are listed together. This helps remind users that surface waters are protected for multiple uses and that some pollutants have more than one applicable standard. In such cases the most restrictive standard applies.

The second place numeric standards are listed is by individual use classes in Minn. R. 7050.0221 – 7050.0227. For example, Minn. R. 7050.0222 has separate lists of the standards for each Class 2 subclass.

The Dissolved Oxygen water quality standards for Class 2 waters are listed in Minn. R. 7050.0222 subp. 2,3,4,5.

Subp. 2. Class 2A waters; aquatic life and recreation. The quality of Class 2A surface waters shall be such as to permit the propagation and maintenance of a healthy community of cold water sport or commercial fish and associated aquatic life, and their habitats. These waters shall be suitable for aquatic recreation of all kinds, including bathing, for which the waters may be usable.

Dissolved oxygen 7.0 mg/l as a daily minimum This dissolved oxygen standard requires compliance with the standard 50 percent of the days at which the flow of the receiving water is equal to the lowest weekly flow with a once in ten-year recurrence interval (7Q10).

Subp. 3. Class 2Bd waters. The quality of Class 2Bd surface waters shall be such as to permit the propagation and maintenance of a healthy community of cool or warm water sport or commercial fish and associated aquatic life and their habitats. These waters shall be suitable for aquatic recreation of all kinds, including bathing, for which the waters may be usable.

Dissolved oxygen 5.0 mg/l as a daily minimum

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This dissolved oxygen standard may be modified on a site-specific basis according to subpart 8, except that no site-specific standard shall be less than 5 mg/l as a daily average and 4 mg/l as a daily minimum. Compliance with this standard is required 50 percent of the days at which the flow of the receiving water is equal to the lowest weekly flow with a once in ten-year recurrence interval (7Q10).

Subp. 4. Class 2B waters. The quality of Class 2B surface waters shall be such as to permit the propagation and maintenance of a healthy community of cool or warm water sport or commercial fish and associated aquatic life, and their habitats. These waters shall be suitable for aquatic recreation of all kinds, including bathing, for which the waters may be usable.

Dissolved oxygen 5.0 mg/l as a daily minimum This dissolved oxygen standard may be modified on a site-specific basis according to subpart 8, except that no site-specific standard shall be less than 5 mg/l as a daily average and 4 mg/l as a daily minimum. Compliance with this standard is required 50 percent of the days at which the flow of the receiving water is equal to the lowest weekly flow with a once in ten-year recurrence interval (7Q10). This standard applies to all Class 2B waters except for those portions of the Mississippi River from the outlet of the metro wastewater treatment works in Saint Paul (River Mile 835) to Lock and Dam No. 2 at Hastings (River Mile 815). For this reach of the Mississippi River the standard is not less than 5 mg/l as a daily average from April 1 through November 30, and not less than 4 mg/l at other times.

Subp. 5. Class 2C waters. The quality of Class 2C surface waters shall be such as to permit the propagation and maintenance of a healthy community of indigenous fish and associated aquatic life, and their habitats. These waters shall be suitable for boating and other forms of aquatic recreation for which the waters may be usable. The standards for Class 2B waters listed in subpart 4 shall apply to these waters except as listed below:

Dissolved oxygen 5.0 mg/l as a daily minimum. This dissolved oxygen standard may be modified on a site-specific basis according to subpart 8, except that no site-specific standard shall be less than 5 mg/l as a daily average and 4 mg/l as a daily minimum. Compliance with this standard is required 50 percent of the days at which the flow of the receiving water is equal to the lowest weekly flow with a once in ten-year recurrence interval (7Q10). This dissolved oxygen standard applies to all Class 2C waters except for those portions of the Mississippi River from the outlet of the metro wastewater treatment works in Saint Paul (River Mile 835) to Lock and Dam No. 2 at Hastings (River Mile 815) and except for the reach of the Minnesota River from the outlet of the Blue Lake wastewater treatment works (River Mile 21) to the mouth at Fort Snelling. For this reach of the Mississippi River the standard is not less than 5 mg/l as a daily average from April 1 through November 30, and not less than 4 mg/l at other times. For the specified

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reach of the Minnesota River the standard shall not be less than 5 mg/l as a daily average year-round.

E. Overview of TMDL project decision points The TMDL project development process includes decision points and may often be an iterative process backtracking occasionally to confirm or adjust pre-existing decisions with regard to newly gathered information or understanding. The following flow chart is a logic tree showing some of the critical steps a project team works through: It is followed by a table with narrative keys referencing the pages where the technical discussion can be found in this protocol and then referencing stakeholder process and stressor identification steps.

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Dissolved Oxygen TMDL Protocols and Submittal Requirements

Figure 13. Flowchart Diagram of the Low Dissolved Oxygen: General Problem Investigation and Attainment Strategy

General Problem Definition

Data Review and Evaluation

303d TMDL List

• WQ Standards • NPDES data • Stakeholder input

• Stream DO data • Mapping tools • Flow data

Yes

Are key DO stressors solely due to natural

background? Or in Attainment?

Develop and Implement the TMDL

Delisting Strategies: • Site-specific standards • Use Attainability Study to remove/modify beneficial uses • Variance

Delisting Strategies: • Natural background • Site-specific standards • Use Attainability Analysis to remove/modify beneficial uses • New Data in Attainment

Comprehensive Data ollection (existing) C

Acquire New Data to Evaluate

Background

(1)

No

No Yes

Possibly

Select Analysis Framework

Develop Analysis Tool(s)

Develop WLA and LA Scenarios

Is DO standard

attainable?

Acquire New Data to Support

Analysis

Identify Data Gaps

Policy and Stakeholder

Inputs

Policy and Stakeholder Inputs

RFP Potential

Start

Policy and Stakeholder

Inputs

Policy and Stakeholder

Inputs

Policy and Stakeholder Inputs

Policy and Stakeholder Inputs

(5)

(6) (13)

(14)

(12)

(11)

(4) (10)

(9)

(8)

(3)

(2) (7)

Try mitigation measures

first?

Implement & monitor

Yes No

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Table 1. Flowchart Key (Part 1: Protocol Technical Flow Path; Part 2: Strength of Evidence and Stakeholder Parallel Flow Path)

Low DO: General Problem Investigation and Attainment Strategy

Box Key

Part 1: Description Technical Flow Path

Protocol References

1 Develop a general description of what is known about the water quality impairment, using readily available information on applicable water quality standards, discharger data, monitoring data, assessment data, and local knowledge.

¶ page 39

2 Identify sources of physical, chemical, and biological data; obtain and compile data; and develop a data management system.

¶ page 41

3 Provide preliminary review and evaluation. What are key stressors on stream DO? What are critical conditions for DO impairments? What are the prominent data gaps?

¶ page 45

4 From existing data review and evaluation, is the impairment due solely to natural and/or irreversible conditions? If yes, then consider strategy for delisting the impaired water (6). If no, then proceed into detailed analysis (7). If additional data is needed to make a determination on natural conditions, identify data needs and acquire new information (5).

¶ page 45

5 Identify data gaps and collect additional background information. ¶ 45 6 Delisting strategies may include: natural background conditions preclude WQ standard

attainment; unique conditions warrant a site-specific standard development; designated beneficial uses are neither present nor attainable; the existing condition may not be natural but is basically irreversible.

7 With consultation and input from stakeholders, assess project objectives, available resources, and analytical tools to develop an overall project framework that identifies roles of key participants and stakeholders. What is the proper balance of local/state/contracted resources? Define scope of services, if any, to be provided by contracted consultants. Develop RFP(s) as needed.

¶ Stakeholder process page 6; Rigor page 50 and Analysis page 51, approaches page 58

8 Based on the preliminary data review and evaluation (3), identify information gaps critical to the selected analysis alternative.

III. Analysis ¶ page 59

9 Design and conduct field studies to obtain physical, chemical, biological stream information; kinetic rate determinations; flow and hydraulics (time-of-travel); diurnal DO data (algal productivity); point and nonpoint loadings; bio-assessments; etc., to satisfy data needs of analysis tool (model).

III. Analysis ¶ page 59

10 Set up the selected general modeling framework with site-specific information. Calibrate and validate model with observed data. Use model to perform component analysis of DO sources and sinks and relate to the prominent stressors. Perform sensitivity analysis on key parameters to understand model response to loadings. Perform accuracy check by comparison of model output with observed data. Report results; receive feedback from stakeholders.

III. Analysis ¶ page 63

11 With consultation and input from stakeholders, design and perform analysis for various example scenarios that evaluate and define WLA, LA, MOS, and reserve capacity.

III. Analysis ¶ page 67

12 Does the analysis predict management scenarios having reasonable potential to meet project objectives for attaining water quality standards? If yes, proceed to TMDL development and implementation (13). If no, then consider strategies for delisting the impaired water (14).

III. Analysis ¶ Page 6 SI and weight of evidence

13 Prepare final technical report with recommendations for developing and implement the TMDL.

IV. Chapter 3 submission requirements

14 Delisting strategies may include: natural background conditions preclude WQ standard attainment; unique conditions warrant a site-specific standard development; designated beneficial uses are neither present nor attainable; the existing condition may not be natural but is basically irreversible; water quality variance.

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Box Key

Part 2: Description Strength of Evidence (Stakeholder Flow Path)

Stakeholder Key

1 Assemble stakeholder group(s) that will: 1) provide local information, 2) communicate well with other watershed interests, 3) assess policy questions, 4) assess technical questions, and 5) provide perspectives and input to the “Reasonable Decision Maker” regarding the influencing of the final decisions.

(Page 6)

2 Identify sources of physical, chemical, and biological data; obtain and compile data; and develop a data management system.

(page 41 and example Section J, page 69)

3 Provide preliminary review and evaluation. What are key stressors on stream DO? What are critical conditions for DO impairments? What are the prominent data gaps? Do local perceptions line up with data evaluation?

(page 45; seeking to identify the

stakeholder opinions) 4 From existing data review and evaluation, is the impairment due solely to

natural and/or irreversible conditions? If yes, then consider strategy for delisting the impaired water (6). If no, then proceed into detailed analysis (7). If additional data is needed to make a determination on natural conditions, identify data needs and acquire new information (5).

(page 45)

5 Identify data gaps and collect additional background information. Page 45 6 Delisting strategies may include: natural background conditions preclude WQ

standard attainment; unique conditions warrant a site-specific standard development; designated beneficial uses are neither present nor attainable; the existing condition may not be natural but is basically irreversible.

7 With consultation and input from stakeholders, assess project objectives, available resources, and analytical tools to develop an overall project framework that identifies roles of key participants and stakeholders. What is the proper balance of local/state/contracted resources? Define scope of services, if any, to be provided by contracted consultants. Develop RFP(s) as needed. Set up RFP(s) to answer questions, validate or modify preconceived notions and provide detailed reports.

Stakeholder process page 6; Rigor page 50 and

Analysis page 51, approaches page 58

8 Technical team 9 Technical team 10 Set up the selected general modeling framework with site-specific

information. Calibrate and validate model with observed data. Use model to perform component analysis of DO sources and sinks and relate to the prominent stressors. Perform sensitivity analysis on key parameters to understand model response to loadings. Perform accuracy check by comparison of model output with observed data. Report results; receive feedback from stakeholders.

(page 63) An iterative process, updating the decision makers with progress, sometimes modifying

the analysis via the weight of evidence.

11 With consultation and input from stakeholders, design and perform analysis for various example scenarios that evaluate and define WLA, LA, MOS, and reserve capacity. Seek expertise on specific issues that arise on each Sector regarding the challenges of change during implementation.

(page 67) Sector costs and risks.

Shared reduction decisions

12 Does the analysis predict management scenarios having reasonable potential to meet project objectives for attaining water quality standards? If yes, proceed to TMDL development and implementation (13). If no, then consider strategies for delisting the impaired water (14).

(page 6 & 67) Encouraging (11) to be an iterative process if

not attained 13 Prepare final technical report with recommendations for developing and

implement the TMDL.

14 Delisting strategies may include: natural background conditions preclude WQ standard attainment; unique conditions warrant a site-specific standard development; designated beneficial uses are neither present nor attainable; the existing condition may not be natural but is basically irreversible; water quality variance.

(g) Consideration of future NPDES

ramifications, Landuse Ordinances,

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F. Initial Problem Assessment Section 305(b) of the federal Clean Water Act requires states to report to Congress with an assessment of their water bodies, whether meeting standards or impaired, while Section 303(d) requires states to develop a list of impaired waters for purposes of the TMDL program. In general, the MPCA assessment process uses established protocols for interpreting water quality data and other information used to determine impaired conditions by stream reach. The Professional Judgment Group (PJG) is composed of assessment staff who know how the preliminary assessments were done, and monitoring staff who advise on the correct interpretation of monitoring data collected by their organization. For additional information on the assessment process, see: Guidance Manual for Assessing the Quality of Minnesota Surface Waters For Determination of Impairment, 305(b) Report and 303(d) List, MPCA, October 2005. http://www.pca.state.mn.us/publications/wq-iw1-06.pdf 1) Impairment Status and History Assessments of use support in Minnesota are made for individual waterbodies. The waterbody unit used for river system assessments is the river reach or “assessment reach”. A river reach extends from one significant tributary river to another and is typically less than 20 miles in length. The reach may be further divided into two or more assessment reaches when there is a change in the use classification (as defined in Minn. R. ch. 7050), or when there is a significant morphological feature such as a dam, or a lake within the reach. All assessment reaches are indexed to the National Hydrographic Data set (NHD). Each waterbody is identified by a unique waterbody identifier code, comprised of the USGS eight digit hydrologic unit code plus the three digit assessment reach. It is for these specific reaches that the data are evaluated for potential use impairment. Water quality and other types of data are the most important component of impairment determinations. Data collection and analysis involves sampling, laboratory analysis, quality assurance/quality control (QA/QC), data storage, and finally, data analysis. Most water quality data used in this process are a result of condition monitoring by the MPCA, but comparable data collected by others are used too, as long as it conforms to acceptable QA/QC requirements. The MPCA uses data collected over the most recent 10-year period for all the water quality assessments. The Professional Judgment Group recognizes that dissolved oxygen can naturally drop below the standard in rivers at times for reasons that have nothing to do with pollution. These natural occurrences, to the extent they are known, are taken into consideration as part of the impairment assessments. The listing of a waterbody on the 303(d) list triggers a regulatory response on the part of the MPCA to address the causes and sources of the impairment through the TMDL process. Starting with data and information used in the impairment assessment, the TMDL project team must pull together additional information that is readily available in order to develop a general description of what is known about the impairment. 2) Prepare a Preliminary Delineation of the Study Area Create project maps of the stream reaches of concern, their contributing watersheds, current land use, and permitted discharger locations. Use appropriate paper maps and MPCA GIS software (ArcGIS) with readily available data layers. Ensure that all newly constructed or imported data layers are fully compatible with MPCA spatial data storage standards:

Condition monitoring is designed to determine current status and trends in water quality.

Dissolved Oxygen TMDL Protocols and Submittal Requirements

Coordinate system: UTM zone 15 (extended) Datum: North American Datum of 1983 (NAD83) Spheroid GRS1980 Units: Meters

Simple stick diagrams are often useful to illustrate the connectivity of the river system and the relative locations of tributary inputs, permitted dischargers, and nonpoint source regions.

3) Define the Spatial and Temporal Scale of the Impairment From existing monitoring data, define which reaches of the waterbody have documented impairments for dissolved oxygen. Is the DO impairment problem localized and distinct or is it more extensive? Do the monitoring data indicate any seasonal pattern to the times of DO impairment? Do the monitoring data provide any insight into the duration (days, weeks, months) of low DO? Do the monitoring data provide any information about the diurnal variation of DO concentrations? What is the magnitude of the DO deficits (DO concentration and % saturation)? What is the frequency of low DO occurrences? Are the occurrences predictable or do they occur randomly? 4) Investigate Flow Dependency of the Impairment Using available stream flow information in the project area, determine the flow conditions at the time of water quality sampling. Are there any apparent relationships between prevailing flow conditions and the instances of low DO? For example, are DO problems most prevalent during periods of low stream flow? Are impairments more prevalent under higher flow conditions when episodic surface runoff events may provide a major component of stream flow? Also identify any reservoirs, dams, or hydropower facilities that may regulate flows in the project area.

5) Compile a List of Permitted NPDES Dischargers in the Study Area Using MPCA discharger inventory databases (WQ DELTA), generate a list of all permitted dischargers including major animal feedlots in the study area. Describe their facility, their design flow, location and receiving waters, permitted load limits, discharge frequency, and general compliance status.

6) Develop a List of Potential Stakeholders Identify and initiate contact with individuals and groups in the governmental and private sectors that should be advised of the TMDL development schedule and plan. Potential stakeholders may include representatives of federal, tribal, state, local (county and municipal) governments; NPDES permitted dischargers; watershed organizations; landowners; agricultural producers; industry trade organizations; and environmental advocacy groups. Consider the potential role each stakeholder could play in the TMDL development and implementation. 7) Develop a Technical Advisory Team The technical advice solicited during development of a TMDL can be both water quality management issues and for a better understanding of land use specific issues. The technical advisory team is composed of a diverse group of local representatives who work with the different land uses and have different expertise areas. Their input on critical aspects of change potential assists during the identification of potential local sources of the key parameters. Later in the process these members can provide assistance in defining the reasonable levels of expected change from an economic or social point of view. The individual members also can be sources of communication to others in their line of work.

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The project manager should develop a summary statement that describes the impairment problem, its spatial and temporal boundaries, and which identifies known factors potentially impacting the oxygen resources of the impaired stream. This summary will provide a focus for the more comprehensive follow-on task of gathering and compiling existing data from various sources that will be used later in the problem analysis tasks.

a. Comprehensive Data Compilation from Existing Resources Factors potentially affecting the dissolved oxygen balance in streams are numerous and complex. Therefore, a DO impairment analysis requires site-specific data in order to define the important cause-effect relationships unique to each case. A comprehensive effort is needed to assemble existing environmental data collected from a variety of sources. An inventory of the compiled data would reveal the areas of obvious data deficiencies in content, quality, and spatial and temporal coverage.

1) What are the Sources of Existing Data?

The answer to this question, when combined with the evaluation of quantity and quality of the data available, will in large part set the scope of the project. The following is a listing of environmental data types and source information.

Ambient Water Chemistry A number of federal, tribal, state, and local government entities, and local water management organizations, collect water quality data. In large part, these data are stored in and can be retrieved from the MPCA Water Quality Database system. Access to data is available through the Water Quality Assessment Viewer site: http://pca-gis03/website/umrb/pjg/index.htm which highlights and displays the Assessment Unit Identifier (AUID) and monitoring stations, and links to the EDA site. Access to data that can easily be exported is available through the Lookup Assessment database: x:\Databases\Water_Quality\Assessment Data Lookup This database contains information from the PJG Assessments meetings, data summaries for AUIDs listed 1992-1998, and direct access to assessment data for AUIDs listed 2002-2006. These sources are preferable to the Environmental Data Access webpage (EDA), which is not as useful for retrieving data. EDA can provide valuable information on alternate station ids, period of record, project and purpose associated with sampling, etc. Access to water quality data through a map-based system is available online at the MPCA Environmental Data Access (EDA) site: http://www.pca.state.mn.us/data/eda/index.cfm. Staff in the MPCA Environmental Data Management Unit can also provide assistance in data search and retrieval from the national STORET database.

EPA’s volunteers guide to setting watershed goals lays out steps that are the building blocks for a robust public involvement process when the teams formed learn to use the key tools of the stressor identification process of validation, elimination and weight of evidence.

Dissolved Oxygen TMDL Protocols and Submittal Requirements

Data may also be available from the WQDelta permitting database (Daily Values Screen) if an NPDES permittee is required by permit to sample the receiving water upstream and/or downstream of the discharge. Standard reports are available in the database that include all individual sample results. These data, though, have not gone through the QA/QC process that applies to data in STORET, so should be used with some caution. Staff in the Water Standards Unit can provide assistance in data search and retrieval for these data.

Biological Assessments The MPCA conducts biological monitoring to assess the health of riverine and wetland environments utilizing fish, macroinvertebrate, or plant communities. Biological communities are subjected to the cumulative effects of all activities within a watershed and are continually integrating environmental conditions over time. They represent the condition of their aquatic environment. Biological monitoring is often able to detect water quality impairments that other methods may miss or underestimate. It provides an effective tool for assessing water resource quality regardless of whether the impact is chemical, physical, or biological in nature. Information and data from biological monitoring sites are available online at the MPCA EDA site: http://www.pca.state.mn.us/data/eda/index.cfm or from the MPCA Biological Monitoring Unit staff.

Fish Kill Incidents The Minnesota Department of Natural Resources (MDNR) is the lead agency that investigates reported fish kills to determine causes and to assess damages. Causes range from the obvious contaminant spills to less obvious natural occurrences. The MPCA and Department of Agriculture is a principle cooperator.

Stream Flow Stream flow data is essential for the analysis of dissolved oxygen impairments. The U.S. Geological Survey (USGS) is the principal source of daily stream flow data. These data can be accessed online at: http://mn.water.usgs.gov/. The site also provides links to other sources of water resource and stream flow data, such as MDNR and the U.S. Army Corps of Engineers. Hydstra The HYDSTRA data base is under development at the MPCA. Hydstra will also be storing diurnal DO data because only summary data is expected to go into STORET. Contact information regarding the stage of development should be requested from Wade Gillingham at the MPCA. Meteorological Weather conditions play a key role during periods of low dissolved oxygen in streams. Historical meteorological data for Minnesota is available online from the Climatology Working Group at: http://climate.umn.edu/. NPDES Point Sources The MPCA maintains a computerized database of permitted NPDES dischargers in its WQ DELTA system. Monthly summary reports (Discharge Monitoring Reports or DMRs) of effluent quantity and quality monitoring submitted by each permittee are available in paper files or electronically from

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DELTA. Web-based access to data from the same reports is available at the MPCA EDA site: http://www.pca.state.mn.us/data/eda/index.cfm The MPCA OnBase Web Client software also provides access to more detailed supplemental reports that are submitted along with the DMRs. Staff in the Regulatory Data Management and Analysis Unit in the Land and Water Quality Permits Section of the Industrial Division can provide assistance in data search and retrieval. Soils and Land Use GIS-based information on land use, soils, and other mapping layers are available at the Minnesota Land Management Information Center: http://www.lmic.state.mn.us/. Other possible sources of information include: Agroecoregions: The University of Minnesota has created a land form data base referred to as Agroecoregions which combine soil types, land use and agricultural production statistics. This is available in map form and tabular and is an excellent means of beginning the data discussion with locals. This can be found on the X-drive at X:\Agency_Files\Water\Impaired Waters\GIS Projects\TMDL Info\Agroecoregions

Historical Water Quality and Hydrological Studies Federal, state and local entities may have conducted special stream studies in your project area that can have valuable historical information applicable to current impairments. Check with the regional USGS office and the MDNR area hydrologist for information on past studies. The MPCA Environmental Analysis and Outcomes Division maintains paper files of historical stream and water quality surveys. Typically these are intensive synoptic type surveys conducted over 1 to 3 days duration to collect physical and chemical stream data to be used for waste load allocation purposes.

Using the Stressor Identification Process: Using the stakeholder advisory group and the technical advisory group, have a guided discussion on where pollution source activities are located in the basin. It is often good to do this over a topographical map with facilities indicated to confirm locations. During the course of the discussion, record the opinions and concerns of the members. Identifying the perceptions and potential sources is critical to creating a better information process for the watershed and to make sure the rigor of the investigation will match the questions that need to be answered.

Local Watershed Studies Local watershed and lake management organizations could provide valuable historical information on the resource and special insight for problem definition. How will Data be Managed for this Project? Development of an efficient and reliable data management system is important for each TMDL project to provide for the proper documentation of subsequent analysis and implementation planning. Decisions on how paper files and electronic data are to be inventoried and stored should be made early in the TMDL planning phase. The data management system should be designed so that project staff and

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Dissolved Oxygen TMDL Protocols and Submittal Requirements

cooperators have efficient access to the data and files. The data management system must be consistent with all MPCA policies and procedures (ref: Policy and Procedures Manual for Management of Public Access to Government Data, MPCA, March 2003). Consideration should be given to developing an on-line web presence for the TMDL project that will allow public access to project information. b. Data Review and Evaluation Once existing data have been collected and compiled, the TMDL team needs to provide a critical evaluation and interpretation of the data with a goal of addressing the key questions: (1) What are the prominent data gaps?, (2) Can the key stressors of stream DO be identified?, (3) What are the critical design conditions for the impairment analysis? c. Prominent Data Gaps Whenever the data review identifies large and obvious data gaps that are critical to the preliminary identification of stressors on stream DO, the TMDL team should initiate a plan for MPCA staff or local cooperators to begin collecting the appropriate data. The plan should be designed with flexibility to screen out less likely sources in order to focus efforts on the more likely stressors. A stream reach may be listed for DO impairments based on data collected from a single monitoring site, or from a very few monitoring sites. Often, the coarse spatial resolution of the existing monitoring data does not provide adequate definition of the zone of oxygen impairment, or whether significant spatial gradients in organic pollutants exist in the study area. For these cases, additional monitoring sites need to be identified and data collected. The same issues pertain to the temporal resolution of existing data. If the existing data was only collected under similar seasonal or flow conditions, the potential for impairment at other times is unknown. Additional monitoring is warranted for screening purposes to identify other possible periods of impairment. Background conditions need to be defined at the boundaries of the study area for the pollutant mass balance and transport analysis. Information is needed on the quantity and quality of water entering and leaving the study area boundaries; i.e., the headwater, major tributary inflows, and study area terminus. Data for point source discharges is generally available. On the other hand, mass loading data for nonpoint sources is not commonly available. These data, which are event-based and runoff dependent, become important when the DO impairments in a stream appear to be related to periods of unsteady flow conditions. In such cases, high-resolution monitoring during runoff events may be needed to define the timing and loading from nonpoint sources.

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d. Stressor Identification Starting Questions Major parameters affecting the DO balance within a stream can be summarized as:

Carbonaceous deoxygenation Nitrogenous deoxygenation Atmospheric reaeration Sediment oxygen demand Photosynthesis and respiration of aquatic plants

Evaluate the existing data to identify the pollutants of concern (projects can often expect existing information will not be adequate to identify the concerns) by looking for evidence of strong linkages between stressor parameters and watershed sources with respect to the DO impairment. For example, does the data sufficiently define the extent of the impairment upstream and downstream from the stations which were used to list it on the 303d list? Or, are there known landuse sources such as a wastewater discharge of organic pollutants which can impact stream DO through both the carbonaceous and the nitrogenous deoxygenation processes? Does the data suggest any correlation exists between point source discharges and observed water quality impacts? Should the project be faced with either of these situations certain questions should be asked of the assessment:

1) Does the data define the spatial and temporal extent of the impairment or source loading? What are the critical periods?

2) Does the project need to set up further monitoring or data gathering to investigate land use types? Or, land use source loadings? Or, water chemistry in the stream?

Spatial locations of the sources and sample locations for the stream chemistry and physical parameters such as temperature and flow are important to record with each step. Using GIS or stick figure maps of the watershed are good ways to communicate information and document assumptions and findings. Sources, both point and nonpoint, may not only have just immediate impacts on stream DO. Nutrients in runoff will stimulate growth and photosynthetic productivity of aquatic plants. Temperature shifts may be sufficiently offset where a stream gradient is steep but impair the system where the gradient is flatter. Is there any correlation between storm frequency, duration, and magnitude with downstream water

When the data does not offer cause and effect relationships or adequate information to eliminate a potential source from further consideration, the EPA stressor identification guidance recommends using a weight of evidence approach. Weight of evidence (sometimes called “strength of evidence”) is best explained as sufficient circumstantial evidence to convince the reasonable decision maker that the source is or is not a primary candidate of the stress. Similar to how a doctor diagnoses a patient, or a detective investigates a crime, fulfilling certain key requirements must be met before a source can be considered for further evaluation.

• Does the source contain or emit any of the critical parameters?

• Is there a pathway to the reach in question?

• Is the key parameter(s) persistent enough to impact the reach in question?

• Does the source discharge the key parameters in the same time period that the impairment occurs over?

Only when the answers to these questions are positive should further investigation be done to quantify or estimate the relative potential and actual loadings that do occur.

Dissolved Oxygen TMDL Protocols and Submittal Requirements

quality responses? Hydrological alterations within a watershed, such as dam construction and channel dredging and straightening, can affect the natural reaeration and sediment transport.

e. Consideration of the Dynamics in a Watershed In many cases, cause-effect linkages will be obscured by a combination of stressor sources impacting stream DO through multiple processes. The data evaluation should try to identify cases of DO impairment that are of possible natural origin, and not from a direct result of human influence within a watershed. Groundwater influences, backwater or wetland influences are a few examples. Where data gaps exist, additional focused data collection of background water quality may be needed to help make that determination. When well defined and understood, these cases of natural impairment may qualify for special consideration under a delisting strategy and would not be subject to the full TMDL development process. However, if a reach is delisted due to the condition being attributed to natural background conditions, future anthropogenic sources, especially those requiring a NPDES permit will be restricted by the implementation plan. Where data evaluation suggests that a DO impairment caused by an obvious and dominating stressor that can be readily mitigated through voluntary actions or by applying existing regulatory authorities (e.g., an NPDES discharge permit or a dam removal project), then there may be reason to consider implementing the mitigation directly and monitor for improvements in water quality before making a decision to continue through the TMDL development process. If the mitigation corrects the DO impairment, then this situation would also be a candidate for delisting.

G. Critical Project Design Conditions

A thorough evaluation of existing data should characterize the DO impairment problem by identifying the conditions under which the stream is most often stressed for DO. This characterization provides the framework for establishing the conditions to be used in designing the impairment analysis. Critical conditions to consider include:

Flow regime Discharge events Storm/runoff events Seasonality Biological Project Boundary

The capacity of a stream to assimilate a waste load of pollutants generally decreases proportionally with decreasing stream flow. A given load of pollutants discharged into a low flow stream will result in higher concentrations of the pollutant and a greater chance of water quality problems than if the same load were discharged into the same stream under higher flow conditions. Because the ambient flow conditions may also influence factors affecting deoxygenation, reaeration, and biological processes, defining the critical flow regime for DO impairments is important to the analysis.

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An evaluation of the magnitude, frequency, and duration of deliveries of pollutant loads to the stream is an important consideration for designing the impairment analysis. A continuously discharging point source with low effluent variability has a much different impact on stream water quality than does a seasonal or intermittent point source discharge, or a nonpoint source loading driven by storm events. Impacts from a continuous discharge may best be evaluated under design conditions using steady-state analytical methods and assumptions. The event-based and intermittent loading situations will require non-steady state analysis with variable design conditions. Seasonally variable ambient conditions, especially temperature, may be strongly correlated with DO impairment problems. The data evaluation should identify design conditions that establish the critical seasons for impairment analysis. Although DO impairments are most common during late summer under low flow and high water temperature conditions, event-based pollutant loadings may cause problems during other seasons. In river systems impacted by large standing crops of aquatic plant life, design conditions for the impairment analysis must include consideration of population dynamics and productivity of the plants. While an actively growing plant population may provide a net benefit to stream dissolved oxygen through photosynthesis, the most critical conditions in the stream may coincide with a dying or respiring plant community. When establishing the boundary conditions for headwater and tributary inputs into the study area, consideration must be given to understanding the factors affecting present quality and quantity of the incoming water, as well as those factors that may change over time and affect boundary conditions in the future. Some questions to be considered may include:

Do the upstream watersheds meet water quality standards? Do the upstream watersheds contain significant anthropogenic loadings that may be amenable to

further control? Do upstream watersheds pass through a natural water body that dampens either pollutant

concentration or flow variability? For persistence parameters such as phosphorus and nitrate, which can be long lasting in the riverine

system, are they at natural background levels or are they amenable to reduction? Will TMDLs be established for parameters in upstream watersheds that may change future boundary

conditions? Are there any hydrological modifications planned for upstream watersheds?

If boundary conditions are expected to change in the future, the impairment analysis should be constructed to evaluate both current and future condition scenarios.

a. Early Monitoring Contract When the existing data does not provide adequate definitions of the problem, the discovery process and the stressor identification methodology can provide cost saving advantages. The process allows for low level of effort expenditures to begin to define the critical conditions and spatial extent of the impairment. Then the project team can make decisions based on the newly acquired information to plan the higher

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level of effort monitoring regime (flow and rigorous chemical sampling). These sites can be limited to fewer locations and not placed exorbitantly in limited value locations in the watershed. For instance to define the extent of the impairment and the critical conditions for which low DO exists in the summer a project might consider the following roll-out of water chemistry monitoring: • As the summer season passes through the typical higher flow regimes in June and flows begin to

drop towards the NPDES permitting design criterion of 7Q10, then a monitoring contract with the Local Governmental Unit (LGU) could include:

1. A longitudinal field parameter sample regime at every culvert, bridge, large discharge source and tributary confluence. The desired field parameters would be DO, temperature, and pH and flow stage (if a permanent structure or feature is available). The sampling should consider diurnal DO fluctuations and multiple visits as the flows continue to drop to adequately define critical conditions.

2. Based on the results from the longitudinal field parameter gathering effort, a similar effort should be conducted for lab analytical samples of CBOD, the complete nutrient suite of nitrogen and phosphorus, chl-a, TSS, as well as the field parameters of pH, temperature and DO values plus specific conductance (significant shifts can be an indicator of groundwater influence). This should be done for the sites that were identified by the field parameter survey as approaching or below water quality numeric criteria as well as a location upstream that is in compliance with the numeric criteria for each critical tributary. It is important to note bed sediment conditions, whether or not a fine organic material exists on the bed, as an indicator of SOD potential. (Note: this survey is done shortly after each field parameter survey and therefore may have an increasing number of locations as flows continue to drop.)

3. Based on land use maps and information gathered from items 1 and 2 a long term monitoring plan is set up including flow stations, event-based water quality sampling stations and collection of field parameters. It is important to relate the longitudinal survey stage information to the flow station information if the flow stations were not pre-existing.

If desired by all parties this monitoring contract can be rolled into a larger LGU contract to facilitate and/or documentation development of the TMDL report and record of decision for the expected duration of the project. As related above the preliminary data set may not be sufficient and have basic data gaps. Local project staff or existing watershed management organizations working with the project may have sufficient training to gather core information regarding those gaps. At this point in the project the team should again evaluate the potential for cost savings. By considering the potential need for: a) time of travel studies, development of dissolved oxygen sag curves, groundwater studies or other investigations. Can the LGU or project team handle any of these special studies? Is it better to have a phased professional contract to: 1) develop an analysis framework, 2) develop these higher level of effort monitoring considering the proposed analysis tool, and 3) set up the analysis tool? Or, are the watershed considerations such that it is possible to do mass balance or simple analysis tool applications with the level of effort being supplied by the project team? In other words, what is the desired level of rigor?

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H. Determining Rigor: Key Concepts to Consider for TMDL Work Plans Rigor as used in the TMDL assessment process means the level or strictness of the science and professional judgment being applied. The use of extreme rigor comes with a high time, staff, and financial resource cost, while a low level of rigor may not be sufficient to develop an adequate plan or allow successful defense of the TMDL if challenged. To prepare an adequate TMDL work plan, project managers need to carefully consider the degree of rigor needed in order to better anticipate resource needs. This is often best done as an iterative process as the project development and scoping work is begun. All watersheds are unique regarding scale, hydrology, types of land use, number and sources of pollutants and their political culture. The final study for a completed TMDL for your specific watershed must balance the complexity of the watershed, the potential for controversy and a limited staff and financial resource pool in the ongoing decisions to achieve the appropriate level of rigor to be useful for returning the water quality back to attainment conditions. There is not a test or quantified metric to use for setting rigor. Instead, after the team has completed pulling together the initial available information for land use and water quality data, during the contract/workplan development process, they should discuss the following open ended questions to guide the project towards an appropriate level of resources needed for developing and implementing a monitoring plan and watershed land use assessment. The process is then extended again when consideration of the data is used in selection of the analysis tool(s) required for a balance of complexity, controversy and cost: Water Quality Monitoring • How robust is the data set?

What is the watershed scale? Do the data sets adequately define the extent of the impairment for the study? Are the sample sets adequate for concentration determinations? Are the flow stations adequate for determining loading? Are data sets available for the critical conditions for the impairment? (considering seasons, changes

in flow, temporal factors and source(s) prominence) Are there critical breaks in information? (either spatially or temporally)

Land use Information • What is the watershed scale? • What are the suspected pollutant sources in the watershed? • Is there information on what pollutant sources potentially discharge? • Are the sources easily related to the chemistry water quality findings? • Are the pathways of the pollutant sources known? • Are their obvious significant loaders or is it a cumulative issue? • What are the NPDES DMR monitoring results for the parameters of concern? • How specific should the Load Allocation source partitioning be? Would finer resolution improve

negotiations significantly? • Are the water quality monitoring stations located adequately to help define the sources?

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How many potential pollution parameters contribute to the impairment? • Can any of the potential pollutant parameters possibly be eliminated based on monitoring? • Do some parameters warrant further investigation? • Are some pollutant parameters more significant than others? What are the probable outcomes of the study? • Will meeting the water quality standard be difficult? • Are there NPDES implications? • Is there a commonly held or developing majority consensus on fairness? These questions and others you may think of help a project consider if the data sets currently are adequate for the negotiations ahead. Also, the rigor of the assessment process can be selected appropriately when the problem and complexities are better understood. This list is used to find out the perceptions and explore a process to manage the project with expectations being appropriate as early as possible.

I. Analysis

a. Basic Objectives The basic objective for a DO impairment analysis is to understand the cause-and-effect relationships governing water quality, such that management alternatives can be explored that will bring the water back into compliance. Simply monitoring and measuring water quality is necessary to define existing conditions, but provides little predictive capability. Employing an analytical tool such as a water quality model helps both to provide an understanding of the complex cause-and-effect relationships currently affecting DO and to provide a capability for extrapolating predictions of water quality over space and time. A modeling analysis can be used to understand and project the consequences of alternative management and planning activities. Models can significantly improve the informational background on which decisions are based, and substantially reduce the cost of managing water resources. When selecting an appropriate analytical tool, some basic guidelines are: • Choose to use the simplest analysis that will provide reliable answers and which will meet project

objectives. • Focus on the key parameters of interest identified in the problem definition phase, avoiding

unnecessary complexities that can waste time and project resources. • Ensure that the analytical framework will provide information for making decisions about resource

management alternatives. • For complex impairments, ensure that the analytical tool provides the capability to define and

partition loadings from the various pollutant sources. • Ensure that funding and human resources are available to perform the analysis.

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b. Selecting an Appropriate Analytical Tool When monitoring and basic water quality investigations alone do not meet the goals and objectives of a TMDL for addressing DO impairments, it will be necessary to select an appropriate water quality model that provides analytical and predictive capabilities. Water quality models are mathematical abstractions or simplifications of enormously complex natural aquatic systems. They can range in complexity from screening-level analysis employing simple mass balances and empirical relationships to multi-dimensional, fully-dynamic models designed for large and complex river systems. Where nonpoint sources of oxygen-demanding pollutants play a significant role in the stream oxygen budget, a watershed runoff simulation model may need to be linked with the stream model. Selection of an appropriate model or analysis framework suitable to a specific TMDL application is no small task. In addition to the basic guidelines presented in the previous section, a basic understanding of the river system and its impairment problem can be applied to select the appropriate time and space dimensions needed for modeling. When the impairment is thought to be from a single permitted source, a simpler analytical method may be applied from the following EPA guidance: Technical Guidance Manual for Performing Waste Load Allocations: Simplified Analytical Method for Determining NPDES Effluent limitations for POTWs Discharging into Low-Flow Streams http://www.epa.gov/waterscience/library/modeling/npdeslowflow.pdf (PDF, 2MB) More complicated scenarios need to begin by asking the following questions regarding simulation options:

a. Is a Steady-state or Dynamic Model Needed? Flows and loads specified for steady-state models are considered to be constant with respect to time. Steady-state models use loads and flows that are averaged over a specified period of time to compute an average response in the stream. Steady-state models are most appropriate to simulate DO impairments that occur during steady base flow conditions in a stream or other times of fairly constant flow conditions. A classic example is the analysis of water quality impacts from a point source discharge under a summer 7-day average low flow condition.

Dynamic models are more complex and are used to describe time-dependent water quality responses from highly variable boundary and pollutant loading conditions, such as would be expected during storm-related loading events in a watershed. Data requirements can be extensive for dynamic simulation models. Rather than time-averaged data as model inputs, these models require discrete time-series data to describe the variability of flow and loadings. Dynamic models may be needed to simulate DO impairments that are variable and not constrained in time or space.

b. Spatial Dimension?

Zero-dimension: A segment of stream is described as a single computation element treated like a completely mixed reactor. Often used in simple screening-level models, these are useful in developing a preliminary indication of the major cause of a water quality problem. An example of a zero-dimension model is a simple mass balance analysis. Conservation of mass is an important basic principle

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underlying all water quality analysis. This is an accounting of material; both suspended and dissolved, moving into and out of a defined volume of water at its interfaces with the sediment bed, the atmosphere, and upstream and downstream waters. Where internal kinetic transformations are known, a mass balance can also account for changes in the mass of a constituent caused by physical, chemical, and biological processes within the defined volume of water. The strength of a mass balance approach is its conceptual simplicity and ease of use. Boundary conditions for the analysis can be obtained by monitoring or estimated using empirical loading factors. A spreadsheet or desktop analysis is often used. The weaknesses of a simplified analysis include a lack of definition of pollutant gradients and a loss of predictive capability that the more process-oriented models can offer.

Figure 14, Stick Figure and Equation for Mass Balance Approaches

QU: is the volume of water in the stream, upstream of the discharge

CU: is the Concentration of the chemical parameter in the water upstream of the discharge

QW: is the volume of wastewater discharged CW: is the Concentration of the chemical parameter in the wastewater discharge

One-dimension: a stream is described as a series of computational elements, each representing a completely-mixed reactor, extending downstream to define only the longitudinal gradients of water quality. A one-dimensional model can accommodate a branching stream network. Since smaller streams are considered well-mixed both vertically (top to bottom) and laterally (bank to bank), a one-dimension formulation is most commonly used to describe stream water quality. The strength of one-dimensional models is their efficiency in simulating pollutant concentration gradients and the longitudinal water quality responses downstream from known loadings. The size of individual

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computational elements can be tailored to the river system. Adequate data must be collected to adequately calibrate these models to site-specific conditions in order to use their predictive capabilities. Figure 15: Diagram concept of a one dimensional model. In a one dimensional model the stream segments are assumed to be well-mixed vertically and laterally (graphic adapted from the EPA Handbook: Stream Sampling for Waste Load Allocation Applications. EPA Office of Research and Development. EPA/625/6-86/013.)

Two-dimension: in wider or deeper streams additional computational elements are added where water quality gradients may vary laterally or be vertically stratified in addition to the longitudinal variation. An example where a two-dimensional analysis may be needed is where it may be important to describe a mixing zone or plume downstream from a discharge in order to protect a sensitive downstream resource. These models are only needed sparingly for specific applications in wide or deep rivers. Adequate data is needed for calibration. Three-dimension: a complex riverine model to describe a system having strong lateral, vertical, and longitudinal water quality gradients that may be found in large river and reservoir systems such as the Mississippi River and Lake Pepin. Multi-dimensional models require much more observational data to calibrate the hydrodynamic transfers of water volume and water quality between the adjoining computational elements. The more complex models often contain a large number of unobservable parameters which complicates model setup and calibration.

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Figure 16: Graphical depiction of a 3-dimensional model. The stream segment is assumed to have width and depth gradients for parameters and/or physical features that need to be explicitly considered by the model.

c. Available Models Generally, water quality models employed by the MPCA for TMDL development should be readily available in the public domain, be well-tested, widely used, and be supported by or acceptable to the U.S. EPA. Again, the preferred and most cost-effective approach is to use the simplest model that includes all the important processes affecting water quality in your study area. However, caution should be exercised in selecting too simple a model which may result in inaccurate predictions that will affect resource management decisions. When the complexities of a DO impairment are not understood at the outset, it is advisable to initially employ a flexible and comprehensive model, but simulate only those processes with the model that appear significant and are supported by monitoring data. As project needs dictate and as more supporting data is obtained, additional model processes can be turned on to provide better definition to the DO impairment and management alternatives. Screening Analysis and Models: A simple mass balance can be used to evaluate the significant loading sources in an impairment study. Using the classic dissolved oxygen deficit equations developed by Streeter and Phelps in 1925, the impact from sources of oxygen-demanding pollutants to a stream can be defined using a desktop analysis or computer spreadsheet application. Nonpoint pollutant loads can be estimated using simple loading functions and empirical expressions relating nonpoint loads to other available parameters.

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One-dimensional, Steady-State Stream Model: QUAL2K is a modernized version of the QUAL2E stream water quality model and is the version currently supported by the U.S. EPA. The model is programmed in the Windows macro language and uses Microsoft Excel as the graphical user interface. The QUAL2K model is available at: http://www.epa.gov/waterscience/wqm/. The QUAL2x modeling framework has a long history of use and is a proven, effective analysis tool. QUAL2K is one-dimensional (longitudinal) and assumes steady-state hydraulics but will allow simulation of diurnal variations in temperature or algal photosynthesis and respiration. It allows for multiple waste discharges, withdrawals, tributary flows, and incremental inflow and outflow. Water quality variables simulated include conservative substances; temperature; bacteria; CBOD; DO; ammonia; nitrite, nitrate, and organic nitrogen; phosphate and organic phosphorus; and algae. QUAL2K improved upon the flexibility of model segmentation, CBOD simulation, sediment-water interactions, light extinction, and simulation of benthic algae. Multi-dimensional, Dynamic Stream Model: The U.S. EPA provides support for the current model version 7 of the Water Quality Analysis Simulation Program (WASP). The model is available at: http://www.epa.gov/waterscience/wqm/. WASP is a dynamic compartment-modeling program for aquatic systems, including both the water column and the underlying benthos. The model can be used to simulate 1, 2, and 3-dimensional systems for a variety of pollutant types. Time-varying processes of flow advection and dispersion; point and diffuse mass loading; and boundary exchanges are represented in the model. WASP can be linked with hydrodynamic flow and sediment transport models that can provide flows, depths, velocities, temperature, salinity, and sediment fluxes. The modeling framework in development for the Mississippi River (Lake Pepin) eutrophication model shares basic simulation processes used in WASP. The US Army Corps of Engineers (USACE) supports the CE-QUAL-RIV1 model which is a dynamic, one-dimensional model that simulates flow and water quality in rivers and run-of-the-river reservoirs where variation in depth is neglected. Where vertical water quality gradients are important, another Corps model designated CE-QUAL-W2 provides a two-dimensional hydrodynamic and water quality analysis that includes the major processes of eutrophication kinetics and sediment interactions. An adaptation of the CE-QUAL-W2 model is being proposed for the Lower Minnesota River Modeling update study. Additional information on the USACE models is available at: http://el.erdc.usace.army.mil/products.cfm?Topic=none. Linked or Integrated Watershed and Stream Models: For watershed and water quality-based analyses, U.S. EPA supports and promotes the Better Assessment Science Integrating point and Nonpoint Sources (BASINS) software system. The system is designed to be flexible, allowing analysis at a variety of scales using tools that range from simple to sophisticated. A geographical information system (GIS) provides the integrating framework for BASINS and organizes spatial information so it can be displayed as maps, tables, or graphics. The software system includes data retrieval and management tools, a series of simulation models, and customizable databases. Core data to run the models can be downloaded via an EPA website. Simulation models included in the BASINS system include the Hydrological Simulation Program – Fortran (HSPF), the Soil and Water Assessment Tool (SWAT), and a simplified pollutant loading program known as PLOAD. HSPF is a comprehensive model of watershed hydrology and water quality

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that allows the integrated simulation of land and soil contaminant runoff processes with in-stream hydraulic and sediment interactions. HSPF was designed as a basin-scale model that includes fate, transport, and transformation of pollutants in one-dimensional stream channels. HSPF is a complex model normally run on an hourly time scale, requiring large amounts of data. The MPCA used a stand-alone version of HSPF for simulating a large portion of the Minnesota River Basin. SWAT, developed by the USDA Agricultural Research Service (ARS), is a physical based watershed-scale model run on a daily time steps. Its design facilitates the prediction of impacts from land management practices over long periods of time on water, sediment, and agricultural chemical yields in large complex watersheds having varying soils, land uses, and management conditions. Additional information on the SWAT model can be found at: http://www.brc.tamus.edu/swat/index.html. PLOAD is a simple screening model that can be used to estimate nonpoint sources of pollution on an annual average basis, using either an export coefficient or another simple method approach. For additional information on BASINS, see: http://www.epa.gov/OST/BASINS/

d. General Approach Alternatives Using the basic understanding of a DO impairment to select an appropriate analytical tool, the next step for the TMDL project manager is to determine a general approach for conducting the technical analysis. Input from project stakeholders and consideration of schedule, budget, and staffing will direct the most efficient utilization of resources to complete the TMDL study. The unique needs of each project will determine the appropriate mix of resources. Options to consider include: • Use state staffing only; • Use a cooperative mix of local resources and state staffing; • Use a cooperative mix of local and state resources with contracted support for specific technical

expertise; or • Use contracted consultant as project lead with cooperative support from state and local resources.

e. Define and Develop Specific Approach Selection of a general approach to undertake the technical analysis leads to the next step of identifying the specific roles of project participants and developing the scope of service for which each participant will be responsible. Stakeholder input is essential to this plan design. For technical services to be provided by contracted consultants, detailed requests for proposals (RFP) must be developed to clearly define the scope of needed services and work product deliverables.

f. Additional Data Acquisition to Support Analysis Framework Identify Specific Data Gaps For the analytical tool or model selected for the DO impairment analysis, specific data elements may be needed to directly support the use of the tool. Watershed and water quality models are general in nature and need to be calibrated with site-specific information to validate their use as reliable tools for

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analyzing DO responses and predicting changes associated with management alternatives. Model documentation can be consulted for specific data requirements. Customizing a model setup for specific applications requires information about the physical characteristics of the river system, information on boundary conditions of the study area, and adequate spatial and temporal coverage of water quality conditions. Water quality models also employ many kinetic rate parameters to simulate the physical, chemical, and biological processes affecting stream DO. Rate parameters that can be field-measured, should be measured. Parameters that can not be measured directly will be set during the model calibration process and adjusted within acceptable ranges supported by the literature. Much of the needed information is not available from historical data collection programs. These specific data gaps need to identified and plans implemented to obtain information critical to the analysis. Design Field Studies and Water Quality Sampling It is not the intent of this protocol to detail the procedures for designing and conducting stream surveys to support modeling applications for DO impairments. Abundant information and guidance manuals are available from the various water resources agencies that cover equipment requirements, personnel requirements, sample collection, determination of stream geometrical and flow characteristics, laboratory analytical techniques, and quality assurance and control. A particularly useful guidance document for general sampling design is from the U.S. EPA is: Handbook: Stream Sampling for Waste Load Allocation Applications. EPA Office of Research and Development. EPA/625/6-86/013. http://www.epa.gov/waterscience/library/modeling/streamsampling.pdf (PDF, 5M)

Other reference documents: Technical Guidance Manual for Developing Total Maximum Daily Loads: Book 2, Rivers and Streams; Part 1 Biochemical Oxygen Demand/Dissolved Oxygen and Nutrient Eutrophication, EPA/823/B-97-002 Year 1997 http://www.epa.gov/waterscience/tmdl/guidance.pdf (PDF, 88M) An often useful exercise is to use the selected model to help design stream surveys. Using readily available information, the model can be set up to examine the available data. Preliminary sensitivity analysis runs can be made to help identify the most needed data. Stream surveys are then focused on the collection of this data while de-emphasizing less important data. Stream surveys used to calibrate and validate a steady-state model are typically intensive synoptic surveys. These are surveys that are usually completed within a few days to a week. They are intended to provide a definition of river responses to a specific set of loadings over a limited time span. On the other hand, data used to calibrate dynamic watershed and stream models that are used to simulate transient water quality events tends to be collected over a longer term to capture the variability of flow and loading conditions that would impact DO. Intensive, short-term data collection efforts are also used to define critical storm-related loading events.

Synoptic survey: a “snapshot in time” of conditions over the area of study.

Dissolved Oxygen TMDL Protocols and Submittal Requirements

Stream Morphology and Hydraulic Geometry: Channel geometry is critical to the modeling of water volume, flow rates, depths, and velocities. Data are used to define the stream configurations and segment characteristics. Because models generally assume constant channel geometry within each computational segment, it is important that stream surveys identify points where channel geometry changes significantly so that the model can be segmented accordingly. Flow Gaging and Stage-discharge Relationships: A simulation model needs an accurate accounting of boundary flows, tributary flows, and diversion flows which can be measured directly. Ungaged surface runoff and lateral inflows from, or losses to, ground water can only be estimated from differences in measured flows at different locations along the stream channel. Development of stage-discharge relationships, together with information on channel geometry, will be useful to understand how water depth relates to flow. An accurate depiction of stream depth is crucial for simulating reaeration and the light attenuation impacts on algae growth. Figure 17: Collection of velocity data to use in combination with channel geometry to develop stage-discharge relationships for the stream

.

Time-of-travel: When stream geometry varies widely within reaches or when lateral inflows are not well defined, it is often necessary to supplement the hydrologic and channel geometric data with time-of-travel studies using dye tracer techniques, typically with rhodamine-WT dye. While stream gaging measures stream flow and velocity at a specific point in time and space, dye tracer studies give a more accurate picture of average water transport velocity over the entire study reach. The time it takes a parcel of water to travel through the study reach is critical to the calibration of important model transformation rates, such as CBOD decay and nitrification.

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Figure 18. A time-of-travel study using dye tracer techniques

Water Quality: The evaluation of information data gaps should provide guidance on where, when, and what additional water quality parameters are needed for modeling analyses. For DO impairment modeling, it is desirable to run long-term CBOD analyses to estimate the ultimate CBOD parameter used by most models. Where nitrification is important to the DO balance in a stream, it may be necessary to collect additional data on the nitrogen species to understand the transformation rates. Point Source Discharges: For steady-state analysis of DO impairments, continuously discharging point sources are assumed to be constant over time, often represented by 24-hour composite sampling of the effluent. For intermittent discharges or highly variable discharges in rate or quality, a sampling program should be designed to get the best representative sample. Times, frequency, duration, and volume of discharge should be noted. Ground Water: Where the estimates of ground water inflow rates appear to be significant in the study reach, water chemistry data from area wells should be examined to estimate the average quality of ground water. Also, isotope aging techniques may be useful to determine the geological sources of ground water impacting the stream; for example, surficial aquifers versus deep bedrock aquifers. Diurnal Dissolved Oxygen, Temperature, pH monitoring: Stream dissolved oxygen fluctuates in diurnal cycles in response to changing water temperatures and biological activity in the water column and sediment bed. Warm water temperatures during daytime reduce the ability of water to hold dissolved oxygen (lower saturation concentration) while the cooler temperatures at night raises the saturation concentration potential. In eutrophic stream environments dominated by aquatic plants such as algae, the opposite effect takes place. High rates of photosynthetically generated oxygen can raise daytime oxygen levels to super-saturation concentrations. At night when plants are respiring and

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consuming rather than producing oxygen, stream concentrations can plunge below the standards set to protect fish and other aquatic animals. For any DO impairment analysis, it is critical that the diurnal patterns of stream dissolved oxygen be measured and the underlying causes understood. Historical grab sample monitoring for DO and temperature do not usually provide the information needed. Automatic recording monitors with DO, temperature, and pH probes should be employed to collect data that will characterize the diurnal fluctuations for the critical design conditions of the TMDL study. Not only will the data show daily minima and maxima, but the continuous data record can be analyzed to derive estimates of photosynthetic oxygen production rates to be used for modeling. Alternatively, but less desirable, a grab sample program can be structured to obtain samples during times representing daily minimums (early morning, up to two hours after sunrise) and daily maximums (late afternoon). Biological Assessments: Measurements of the density and diversity of a biological community within a stream study reach is a useful gage of stream health at a point in time. Biological assessment techniques can be employed to characterize a stream’s biological health both before and after resource management activities are in place. Along with water chemistry data, bio-assessments provide a valuable tool to document changes in the water resource.

g. Model Set-Up and Evaluation Generally, models are simplified mathematical representations of the extremely complex real world systems. Models cannot accurately depict the multitude of processes occurring at the various chemical and physical levels. Still, models can make use of known interrelationships among variables in order to predict how a given quantity (or extensive variable such as sediment load) or state variable (or intensive variable such as water temperature or pollutant concentrations) would change in response to a change in an interdependent quantity or state variable. These interrelationships are expressed as sets of equations. In this way, models may be useful frameworks for investigations of how a given system would likely respond to a perturbation from its current state. For this reason, the predictive capabilities of models are often helpful in the study of large natural systems. Watershed models are particularly useful, since it is often difficult to actually change such existing conditions as land use or weather patterns in the real world. Each set of equations contain different variables. Some of these variables are input parameters which must be assigned for the model to formulate a simulation. Other variables are output variables. The model uses the set of equations to estimate output variables as a result of the simulation process. Model Parameter Assignment The modeler must assign values to each of the required input parameters. Some of these input parameters can be direct measurements of real world quantities or state variables. For instance, watershed models generally require meteorological records for input. These contain quantities such as hourly rainfall amounts and state variables such as air temperature, dew point, and solar radiation. These values are generally place directly into the model input files without manipulation or estimation of uncertainties associated with these parameter values. This type of input is often called a “forcing function” since it is regarded as a fundamental condition affecting model output.

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Other input parameters are not as easily measurable as air temperature. They require the modeler to use professional judgment in the estimation of that parameter. In some cases the parameter can be estimated on the basis of laboratory or field experimentation. In other cases, there is no “real world” surrogate for that parameter. The modeler must use available information to determine an appropriate parameter value. In other cases, the parameter has surrogates in the physical world, but the parameter is averaged over such a large and heterogeneous scale that it is impossible to extract a single value based on experimentation. The estimated parameter value must be the result of the aggregation or lumping of values over various smaller scales. Selecting values for estimated parameters is a critical step in the initial set-up of the model. It is these parameters that normally require some adjustment in the calibration process. Since most of the uncertainty of the model results is related to parameter estimation, it is usually prudent to include a sensitivity analysis of the output of interest to changes in value of the estimated parameters as part of the model evaluation. Comparison of Simulated Output with Observed Data Comparison of simulated output with observed data should be made during all phases of the model set-up process. Obviously, when the modeler is assigning values to estimated input parameters; she/he should do so in such a way that the simulated output that the model generates resembles the observed data. For hydrological models, in general, the meteorological conditions (temperature, rainfall amounts) are considered forcing functions and are direct parameter inputs. The modeler then assigns values to estimated input parameters (i.e. infiltration, field roughness) so that the model output (simulated flow in a river reach) matches the observed data, which in this case would be measured flow in that river reach. The modeler should systematically compare observed data with simulated output during the calibration process, and adjust the estimated parameters accordingly. Statistical comparisons of the simulated output with the observed data should be made during the model validation and the sensitivity analysis to demonstrate the utility and relative “accuracy” of the model.

Calibration Calibration of most models involves adjusting the estimated model parameters in such a way that model output resembles values available observed data. In the case where observed data is lacking, the model should output values that are in a reasonable and expected range. Watershed models contain a hierarchy of simulations. This hierarchy dictates the order of model routine calibration. The calculation of water flow within a given riverine reach is the most fundamental routine in a model. Any error in water flow will be propagated and often multiplied in other model routines. For this reason, the flow calculations in a given model should be calibrated first. Once the modeler is satisfied with the calibration of flow, the calibration of routines simulating sediment and dissolved constituents, such as dissolved oxygen, can occur. Finally, once the sediment simulation has been adequately calibrated, the modeler can calibrate routines involving the simulation of sediment-sorbed constituents, such as phosphorus. For watershed models which simulate output in a time series format (i.e. hourly values for a period of several years), it is recommended that the simulated time series output be compared to the time series of

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observed data. Visual comparisons should be made to assure that the simulated output is in general agreement with the available data. These comparisons should be made on different time scales, beginning with a long-term coarse timeframe. For instance, when calibrating flow, one should first compare simulated annual flows to observed annual flows. On this broad timescale, it is particularly important to be sure that the model is neither consistently over predicting nor under-predicting observed data. Next the plots on the monthly timeframe should be examined. It is not uncommon for some models to accurately predict annual flows, however, these models can have a seasonal bias (i.e. under-predict flows in the spring and over-predict flows in the summer). An analysis of monthly plots allows the modeler to recognize these seasonal inaccuracies. The modeler can then proceed with the comparisons at a daily, or in some cases, even hourly timeframe. At these timeframes, not only is the magnitude of an event very critical, but the timing of the event is also important. When calibrating flow, it is important not only to compare peak height, but also the peak width, the area under a storm peak, the overall shape of a storm peak and the position in time of a storm peak. It is also important to compare the values of baseflow, between storm peaks. These visual comparisons are usually the most helpful and informative tool in model calibration. It is critical to make these comparisons for flow as well as concentrations and loads of constituents of interest. Unfortunately, a lack of observed data often compromises the utility of concentration, especially load comparisons. In this case, it is often beneficial to rely on statistical comparisons between the data sets of observed values and simulated output. These comparisons are often useful. It is important however, to only compare data on time periods when observed data is available. Often, a lack of data from a station consistently occurs under certain conditions. For example many gauging stations are unable to report flow when water elevation drops below a certain level. In this case, the low flow portion of the observed record is absent. Care should be taken not to compare this observed data set with the entire corresponding simulated output which would contain flow values under all conditions. It is also important to construct plots of observed versus simulated loads and concentrations. These plots and their associated linear regressions are often useful in identifying systematic biases within the set of model parameters. Validation or Verification Model validation involves the input of a separate record of timeseries data into the simulation. This data record must not have been used in the model calibration process. The modeler follows the steps of the calibration process and makes the same visual and statistical comparisons. However, the model output must satisfactorily match the observed record for that time period without the manipulation of any model parameter values, estimated or otherwise, which were determined during the calibration process. In this manner, the validation process must be completely independent of the calibration. If the model output does not adequately match the observed data for the validation record; the calibration and subsequent validation process must be repeated. Principal Component Analysis Principal component analysis is a statistical technique usually applied to identify which sets of variables within a larger set form coherent subsets that are independent of other subsets. Variables that correlate

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with one another and are also mostly independent of other subsets of variables are combined into “factors”. Principle component analysis can be very useful in determining which groups of variables are interrelated and also in reducing the number of variables in the system by combining correlated variables into factors. If for a large set of data there is a strong correlation between BOD and VSS, then the set of these two input parameters can be combined into one factor. In a sense, this reduces the dimensionality of the system. If there is a strong positive correlation between these two parameters, then the modeler may wish to only vary these two parameters in the same direction (i.e. increase both or decrease both) when performing a sensitivity analysis involving these parameters. Sensitivity Analysis Sensitivity Analysis is the study of how the uncertainty in the output of a model (such as dissolved oxygen concentration) can be assigned to different sources of uncertainty in the model input. Sensitivity analysis is an essential step in the evaluation of any model and a required part of any discussion of model defensibility. In any model there are one or more input parameters which are interrelated with the output parameter of interest. The modeler must identify the input parameters which have a mathematical influence on the value of the output parameter. Once the related input parameters are identified, the modeler must systematically and individually increase and decrease the value of each relevant input parameter. If small changes in the value of an input parameter result in a large change in value of the output parameter, the output parameter is said to be very sensitive to that input parameter. If large changes in the value of an input parameter result in a small change in value of the output parameter, the output parameter is said to be relatively insensitive to that input parameter. The modeler must identify which input parameters the output parameter displays the greatest sensitivity. The modeler should statistically quantify the uncertainties apportioned to the values of each of the sensitive input parameters, especially the estimated input parameters. The modeler should also use statistical tests to express the impacts of varying more than one of the sensitive input parameters simultaneously. For models which predict dissolved oxygen concentrations, it is normally appropriate to include any input parameters that affect the following variables in the sensitivity analysis: water flow, water depth, water velocity, CBOD, SOD, VSS, nitrogen, phosphorus, phytoplankton, and any other parameters which are mathematically related to dissolved oxygen concentrations. Uncertainty Analysis The uncertainty analysis can be used in exploring the requirements for the margin of safety (MOS) that is needed in the specific watershed and this model application. The uncertainty analysis will tie in nicely with the sensitivity analysis mentioned in chapter III section C. However, now that a balanced allocation scenario is developed it may be important to rerun the allocation and select incremental key stressor parameter changes. Evaluating temperature, CBOD, nitrogenous and eutrophic factors in this way will assist in understanding the needed MOS for the assessment. A suggested starting increment trial would be 5 percent steps, ranging from -10 to + 10 percent of the given loading for the pollutant parameters at the future conditions.

J. Development of Example Evaluation Scenarios Commonly occurring within stakeholder advisory discussions is the desire to have a discussion on three main themes;

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(i) What range of reductions could be expected from each source type or category? (ii) What are the costs, in terms of economics or risk? (iii) What are equitable allocations between source categories that will meet the TMDL

allocation?

To answer these questions in a public setting some preparation work must be done in advance. It is often a good process to have some preselected scenarios ready to foster discussion. It is important to remember that each future scenario might contain several model runs that identify the changes or balance needed for the number of significant contributing stressing parameters (CBOD, NBOD, temp, SOD and eutrophication) and there individual reduction goals. Typical examples could be:

(a) Natural background/presettlement – Some models balanced on current hydrology can not simulate the system without the drainage enhancements already in place in the system because the hydrographs and resulting loadings reflect the altered pathways. Yet it is valuable to consider a regional presettlement vegetation coverage. This can be used to evaluate the extreme end point of current day loading with a given hydrology.

(b) Seasonal/critical conditions – The system may move in and out of compliance with the numeric criteria for given flows and for given reaches in the watershed. A detailed output for current day conditions can help the discussions along regarding the transition flows, seasonal effects such as eutrophication, ice cover or temperature regimes.

(c) Geographic assessments – In larger watersheds with tributaries a system of model runs to vary a subwatersheds input can help in defining area hot spots, and potential for reductions from significantly contributing subwatersheds.

(d) Future loading considerations (no action) - Including new point and nonpoint projected loadings for the watershed if the system was not altered beyond today’s level of applied treatment for existing similar source technologies.

(e) Ranges of point source reductions in the watershed – Using different levels of treatment for the key stressor parameters, determine what are the expected load reductions for each parameter and then with regard to improvements in dissolved oxygen.

(f) Results from varying levels of effort for nonpoint source Best Management Practice Systems (BMPs) – using different levels of adoption for a given set of previously selected BMPs, provide the output results for changes in loading of the key stressor parameters and the improvement in dissolve oxygen.

(g) Best available technologies – Applying the highest level of effort that the current technology supports within each source sector’s realm.

(h) Balanced Allocation example – Explore a combination of treatment measures from all sectors that will work to balance the allocation with or without reserve capacity.

These model outputs will not generate the whole background for the discussion. Other aspects should include the local perspectives on the controversial issues, sector specific cost estimates for the implementation measures modeled, manager risk elements (such as crop yield loss, compliance determinations, etc.). When developing these scenarios and the scenario discussions, the team should keep in mind the needed Margin of Safety. Can these scenarios be used to assist in understanding the benefits from incorporating implicit or explicit safety assumptions?

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K. Project Case Example and Stressor ID Discussion The following case example contains some of the typical considerations occurring in active TMDL studies in Minnesota. This case example is meant to illustrate when and how critical management concepts (Stressor Identification considerations) are introduced into the TMDL project process. As an illustration, the process has a flow where one step leads to the next in a logical progression; however, any given project may encounter data sets that do not at first make sense. More information or additional team members with higher expertise (including professional contracts) may need to be added throughout the course of a project. It is recommended that a project consider using contracts for LGU services and the master contract for professional services in a staged fashion, considering:

• the level of effort required to gather, assess and advance the current watershed understanding, and

• the desired rigor (see Chapter 2, section H) and resources available. Some project teams will consider using a professional contract that has a phased approach, with the options in each phase as separate line items to enable that option to be not implemented if that task is not needed. These contract methods will help avoid and prevent significant contract delays or large change orders to amend the contract for special studies that were not previously predicted. These methods also can provide significant cost saving features; as the contracts to deal with special studies or new professional services can be developed based on the specific information and consideration of the rigor needed to move the TMDL forward.

Ailing River - fictional case study

The MPCA staff project manager assigned to the project is able to gather existing documents and data to compile the following information. Ailing River is listed on the 303d impaired waters list for low DO based on a permit effluent limit study for point sources. The listing data set contains two synoptic data sets of three days each at two lower flow regimes. The low flow conditions provided are the 20 percentile and the 7Q10. The data set has a time-of-travel dye study and diurnal DO information for the reach closest to Larson City. In Larson City there are three NPDES permitted discharges, the city municipal wastewater treatment works, one food processing industry with stabilization ponds, and one industry with a noncontact cooling water discharge. Ailing River Watershed District has been in existence for two years. The District has one hydrologic event sampling station at a USGS flow station located downstream at the mouth of the River prior to entering into Slow River, and two grab sampling sites. One is located at Larson City and one on Ditch 12. Event monitoring data sets are available for one summer season (with a wet year as a base, higher flow regimes than 7Q10). Ailing River watershed is dominated by agricultural land use with two small communities, Larson City and Olsen City. Larson City is the only community with active industrial NPDES permits. The watershed has a steeper gradient in the upper reaches with shaded riparian canopy and lower gradients in the downstream reaches with no perennial vegetative canopy. Noncompliant Individual Septic Tank Systems (ISTS) are known to exist in the watershed. The main noncompliance issue is septic tank direct discharges into agricultural tile drainage lines occurring in about 35 percent of the sites. Three livestock operations are located in the watershed.

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A core or starter technical committee is formed consisting of the representatives from the Watershed District, SWCD technical staff, a local environmental activist who also is farming, and MPCA staff. It is important to try and gather all the existing watershed water quality data and the landuse data into visual aids for the preliminary assessment discussions. This will be the center of activity as early discussions with the project team and committees take place. This project does not have GIS mapping capability and instead chose to use a stick figure map showing the current understanding of the preliminary watershed information, as shown in Figure 19.

Figure 19, Preliminary Data Stick Figure Map. The culvert/bridge crossings are indicated by breaks in the lines.

Mouth at Slow River

WQ Sta. & USGS Flow

Larson City

(Grab Samples)

Ailing River Stick Figure Map

Olson City

Food Processor

Ponds

Ditch

# 12Cooling water

Feedlot # 1

Grazing

Feedlot #2

(Grab Samples)

Upon looking at the preliminary data the team concludes that the listing data set does not provide a good description of the spatial and temporal extent of the impairment or define the critical conditions. The parameter list for the event station and grab sampling by the District is limited to TP, ortho-P, TSS, and nitrate/nitrite nitrogen and therefore does not provide adequate information on most of the parameters that may stress DO. A work plan must now be discussed for the project to gather more information in a timely and cost effective manner. The project team decides that an “early monitoring contract” should be extended to the Ailing River Watershed District to:

• Facilitate the TMDL project meetings, and documentation/report writing.

Dissolved Oxygen TMDL Protocols and Submittal Requirements

• Define the spatial extent of impairments by conducting preliminary longitudinal surveys throughout the watershed with field parameters (temperature, DO and pH) in late summer as flows drop throughout the watershed. Locations are at bridges, culverts and tributary confluences plus downstream of the two communities and two industries.

• Conduct two longitudinal intensive surveys that include field temperature, pH, DO and stream flow measurements, and water grab samples for lab analytical parameters (CBOD, TKN, ammonia, Nitrate-Nitrite, Chl-a, total Phosphorus, ortho-phosphorus, total suspended solids, turbidity and specific conductance) just after the preliminary longitudinal survey and with coverage throughout the discovered non-attainment reaches and at one compliant site upstream for each tributary (if any). Coordinate with NPDES dischargers to obtain effluent samples, if discharging during the surveys. Field notes will include descriptions of aquatic vegetation and sediment characterization on the bed of the river.

• Assist with establishing, use and maintaining up to four flow and water quality event sampling stations in the watershed. Stations will have the capability to do a diurnal automatic sampling regime, including continuously recording sondes for pH, temperature, and DO as needed.

The contract begins in July and during the late summer season the weather cooperates and the longitudinal sampling surveys are completed in a stepwise fashion as flow drops. At the early low flow stages, first a field parameter survey is done and then the lab analytical sampling survey is completed. As stages continue to drop the series is repeated and expanded if the field parameter survey indicates a larger spatial extent. The pre-existing hydrologic event-monitoring station has a probe added for DO, pH and temperature. Using the extended parameter list, at least 8 samples are collected and analyzed per season, targeting three storm hydrographs, three late summer base flow periods and two discretionary samples. The project team compiles the data sets from each longitudinal survey into one stick figure map and table of key WQ parameters for the watershed. At this time the land use information previously gathered is also discussed for new information from the larger team. Figure 20, is the updated stick figure map and Table 2 is the survey results.

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Figure 20, Stick Figure Map Showing Longitudinal Survey stations

Mouth at Slow River

Sta. A 1 & USGS Flow

Larson City

A2

Ailing River Stick Figure Map

Olson City

Food Processor

Ponds

Ditch

# 12Cooling water

Feedlot # 1

Feedlot #2A11

A 4

A5A6

A7

A10

A9

WWTP

WWTP

Grazing

A3

A8

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Table 2, Longitudinal Survey Results by date

Sta Date Time cfs pH Temp DO Spec Cond.

TP mg/l

CBOD NBOD Chl-a

A1 7/20 6:15 12 8.5 23.0 2.54

A2 7/20 6:33 18 8.6 22.8 3.85

A3 7/20 6:55 17 7.9 25.2 3.15

A4 7/20 7:53 10 7.9 32.5 2.89

A5 7/20 8:05 4 8.1 21.6 4.66

A6 7/20 8:30 5 7.9 24.2 4.54

A7 7/20 8:50 3 8.6 22.6 5.13

A8 7/20 8:58 3 8.5 21.2 6.20

A9 7/20 9:20 4 8.4 20.6 6.15

A10 7/20 9:49 3 8.1 19.2 6.33

A11 7/20 9:59 1 8.3 20.0 6.14

A1 7/22 5:30 11 8.4 18.8 2.89 682 0.165 7.1 9.9 32.3

A2 7/22 6:10 18 8.3 19.9 3.85 700 0.175 2.8 1.6 26.0

A3 7/22 6:45 16 7.8 22.8 4.37 520 0.103 1.4 0.75 15.9

A4 7/22 7:20 11 8.3 26.5 4.6 500 0.110 0.8 .65 20.5

A5 7/22 7:48 4 7.8 17.3 1.4 380 0.275 1.5 1.9 53.6

A6 7/22 8:22 4 7.9 24.6 1.9 498 0.300 1.3 1.8 47.1

A7 7/22 8:51 4 8.4 19.3 6.1 550 0.090 1.5 0.80 3.72

A9 7/22 9:45 3 8.5 21.2 5.8 650 0.110 2.0 1.4 1.46

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Table 3, Longitudinal Survey Results by date

Sta Date time cfs pH temp

ºC

DO

mg/l

Spec

cond

TP

mg/l

CBOD

mg/l

TKN

mg/l

Chl-a

ug/l

A1 8/15 6:20 5 8.1 27.0 1.3

A2 8/15 6:40 9 8.2 25.3 2.7

A3 8/15 6:50 8 7.7 29.4 2.2

A4 8/15 7:35 10 7.9 35.7 2.1

A5 8/15 7:55 5 8.2 24.6 3.5

A6 8/15 8:20 6 7.8 25.5 4.8

A7 8/15 8:45 4 8.5 24.6 5.6

A8 8/15 8:53 3 8.4 23.2 5.4

A9 8/15 9:15 5 8.3 22.0 5.8

A10 8/15 9:39 4 8.0 20.5 5.6

A11 8/15 9:56 3 8.0 23.0 5.7

A1 8/16 5:45 6 8.4 20.8 2.15 750 0.125 6.1 11.8 45.8

A2 8/16 5:59 9 8.3 25.9 3.05 880 0.375 5.8 7.6 35.0

A3 8/16 6:38 9 7.8 27.8 2.45 680 0.203 4.6 5.75 16.7

A4 8/16 7:12 11 8.3 29.5 3.96 708 0.135 0.5 1.65 18.5

A5 8/16 7:39 5 7.8 21.3 1.9 390 0.195 2.5 2.7 35.6

A6 8/16 8:19 5 7.9 23.7 2.8 518 0.215 2.8 3.5 45.1

A7 8/16 8:46 5 8.4 22.6 4.9 500 0.130 2.1 1.80 18.7

A9 8/16 9:26 4 8.5 20.9 5.1 625 0.189 3.0 4.4 11.5

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Careful consideration of the findings, in Tables 2 and 3, from the surveys reveals that head water ditch 12 remains in compliance and the field notes indicate that it has a relatively good velocity, and that no fines (detritus) are building up on the channel bed at the velocities currently in the stream. However, the channelized system leading from Olson city above station A5 has little if any flow and numerous pools exist in the reach with a significant build up of small detritus type material on the bed. The DMR records for the stabilization ponds for the City of Olson and the food processing industry above station 9 indicate that no discharge occurred during these survey periods. Table 4, below is a historic record for conductance that can be used to guide the project team on the range of values that will inform them on the influence of ground water and surface water. Agency Station Date Time Parameter Result

USGS 5300000 10/3/1960 10:40 95 1010USGS 5300000 3/20/1961 9:20 95 678USGS 5300000 5/15/1961 17:00 95 1390USGS 5300000 3/29/1962 9:15 95 309USGS 5300000 2/28/1963 9:30 95 2310USGS 5300000 8/4/1965 12:05 95 1150

Table 4. # 00095 - Specific conductance, water, unfiltered, microsiemens per centimeter at 25 degrees Celsius

for Lac Qui Parle River This table provides actual data for specific conductance, parameter number 95, sampled in Lac Qui Parle River (while the case example is not Lac Qui Parle River this data demonstrates a common range in south western Minnesota). The samples were collected by the USGS from 1960 to 1965. The key point to use as a project reference is the variability regarding winter frozen conditions (with little run off and mostly groundwater feed 2/28/1963) versus the other times of year when varying ratios of groundwater and surface water is mixed. In March of 1962 during a snow melt runoff event the specific conductance is relatively low for this river relating to the high percentage of surface runoff contributing to the river flow (309 microsiemens/centimeter). In the winter period when ground water recharge is the dominant source of river flow the specific conductance jumps up to reflect the higher mineral content of the dissolved solids (2/28/1963, 2310 microsiemens/centimeter). A project team can look at historic data and compare specific conductance or temperature (groundwater temperatures typically are around 49 degrees Fahrenheit, or 10 degrees centigrade) to determine if certain reaches are showing significant groundwater influence during dry weather conditions. Ground water may be entering the stream with little or no dissolved oxygen and therefore may be a natural source of stress on a given reach. During the low flow surveys, the whole system overall does not have temperature, or specific conductance indications of being significantly influenced by groundwater or of containing eutrophication related issues as determined by the low Chl-a and regional comparisons with TP.

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Other information obtained at this time are the Larson City WWTP permitted effluent limits of 15 mg/l CBOD5, 30 mg/l TSS and 1 mg/l for ammonia. The noncontact cooling water industry does not have to monitor for CBOD nutrients or TSS, but did happen to have the monthly temperature reading of 35 ºC taken on the 7/22 survey date. The monthly flow average permitted flow is 1.3 MGD. Concerns over temperature and the unknown source contribution from the noncontact cooling water were discussed. Nonpoint sources from feedlots indicate little significant impacts from the two headwater feedlots during this period of time. A feedlot assessment is set up to confirm the management goals of these sites. However, the grazing facility on the mainstem of Ailing River downstream of Larson City is suspected of being a significant loader even under the higher flow regime of the first two surveys as is indicated by the TKN and CBOD values. An interview with the feedlot manager is being set up. Based on the improved watershed understanding, the project team recommends that a professional contract for a modeling effort to include related data gaps assessment and monitoring study. This higher level of rigor was selected because of: • The complexity of finding multiple stressor parameters contributing to the impairment issues, • The close proximity of NPDES facilities to the monitoring stations with some of the lowest DO

readings and highest concentrations of stressing parameters (indicating a possible NPDES effluent limit change as a likely outcome).

• The lack of data on the two NPDES pond facilities and the need to estimate possible impacts from these sources.

The professional contract was issued to a consultant on the master contract list who performed a data gaps assessment for the proposed QUAL2K one dimensional model. The results were: a combined data collection effort by the LGU; installing the new event sampling stations for collecting four grab samples of ultimate CBOD, continuous DO, temp and pH readings during low flow stages as advised by the consultant; and augmenting the information with grab sample collections in the compliant tributaries. The professional contract also allowed for a new time-of-travel dye study and velocity data gathering from station A6 down through Station A1. It also provided for a three day low flow study in the following year. The contact was specific with requesting the uncertainty analysis and model performance criteria related in Chapter 2, Section I and the EPA reference material. Upon completion of the first monitoring season for the professional contract, the model calibration effort began. Midway through the second monitoring season in the LGU contract, the loading information was included in the calibration effort and the model was then verified with the conditions provided by the low flow study from 1988. Next, the consultant worked with the project team and committees to provide scenarios that fostered robust discussions of possible results from land use changes and treatment measures that are possible in the watershed. The model results were also augmented by sector experts from the municipal wastewater representative (their consulting engineer), the industrial wastewater representatives, and University of Minnesota Department of Soil Water and Climate professors regarding agricultural measures. These discussions included possible existing measures available, risks and costs of each, and other impediments to change. From these discussions, an example scenario was generated for water quality attainment. The committees attempted to adjust the attainment goal strategy with two attempts before finding an alternative that would attain water quality objectives and represented an “equitable” solution from all contributing sources.

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The professional contractor provided a model calibration and verification report, scenario development report, and special monitoring study report in addition to answering questions for the LGU during development of the TMDL study report. The LGU provided a report on the monitoring results from the contract period, a TMDL study report, and facilitated the multiple meetings setup and documentation to keep all participants in the process informed throughout the project. The wasteload implementation measures selected were: • An adjustment to 5 mg/l CBOD limit, 6 mg/l (minimum) dissolved oxygen effluent limits for the

City of Larson WWTP, • Further limiting the window for allowable discharge from the stabilization ponds for the food

processor and the City of Olson to October where cooler water temperatures provided conditions for sufficient assimilative capacity in the stream (estimated by the professional model contract).

• Twice a week temperature and daily flow measurements, plus monthly CBOD, nutrient and TSS monitoring requirements for the noncontact cooling water facility, with a potential permit reopener contingent on the watershed response to other implementation measure and the findings from the new DMR requirements, and

• 100 percent non-compliant ISTS correction watershed wide. The load implementation measures selected were: • Livestock exclusion incentives are provided for the grazing operation near station A2, • Soil erosion control measures to achieve “T” (tolerable soil erosion loss; defined by the Natural

Resource Conservation Service) to reduce the soil organic matter contributions from row cropped fields, and

• Riparian woody vegetation management buffer program initiatives for soil erosion control and temperature benefits (with the understanding that some leaf litter will be contributed as an organic load back into the system).

Due to the scale of the watershed and the potential size of each contributing source type, the project did not pursue other professional contracts such as watershed land use modeling to quantify the WLA loading for each NPDES permit or septic system. The NPS contributions from the grazing operation and row cropping were estimated using a simpler mass balance approach. No additional stream temperature studies were pursued for sizing the woody vegetation canopy goals. In the TMDL report, each sector was provided an estimate of its current loading and needed reduction goal. These goals were documented using the weight of evidence and stressor identification organization process. The TMDL development process also instructed the watershed district to engage in adaptive management during implementation for confirmation of the goals set in the TMDL. Instead of higher rigor NPS quantifying efforts, the stressor identification process brought all of the participants, point and nonpoint, up to a confidence level where use of “typical” literature based loadings could be used. The concerns of the group were further addressed by using the adaptive management check during implementation (proper effectiveness monitoring tied to, as necessary, adjustments in implementation goals) to obtain compliance with water quality standards.

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Part III: Dissolved Oxygen TMDL Submittal Requirements

A. Dissolved Oxygen TMDL Submittal Requirements For an approvable Dissolved Oxygen TMDL, the final report must meet both federal requirements and state protocols. Each major component of a TMDL is described in this section and includes:

• Federal requirements, which are used by the EPA as a basis for reviewing and approving TMDLs; and

• Minnesota’s protocols as required by the MPCA. In addition, “MPCA’s Checklist” (Appendix A) for reviewing the adequacy of draft TMDLs prior to submittal to EPA should also be consulted to ensure the report is complete. EPA Guidelines for Reviewing TMDLs Under Existing Regulations Issued in 1992 (http://epa.gov/owow/tmdl/guidance/final52002.html) Section 303(d) of the Clean Water Act (CWA) and EPA's implementing regulations at 40 C.F.R. Part 130 describe the statutory and regulatory requirements for approvable TMDLs. Additional information is generally necessary for EPA to determine if a submitted TMDL fulfills the legal requirements for approval under Section 303(d) and EPA regulations, and should be included in the submittal package. Use of the verb "must" below denotes information that is required to be submitted because it relates to elements of the TMDL required by the CWA and by regulation. Use of the term "should" below denotes information that is generally necessary for EPA to determine if a submitted TMDL is approvable. These TMDL review guidelines are not themselves regulations. They are an attempt to summarize and provide guidance regarding currently effective statutory and regulatory requirements relating to TMDLs. Any differences between these guidelines and EPA's TMDL regulations should be resolved in favor of the regulations themselves.

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B. Identification of Waterbody, Pollutant of Concern, Pollutant Sources, and Priority Ranking Federal Requirements: The TMDL submittal should identify the waterbody as it appears on the State's/Tribe's 303(d) list. The waterbody should be identified/georeferenced using the National Hydrography Dataset (NHD), and the TMDL should clearly identify the pollutant for which the TMDL is being established. In addition, the TMDL should identify the priority ranking of the waterbody and specify the link between the pollutant of concern and the water quality standard (see section 2 below). The TMDL submittal should include an identification of the point and nonpoint sources of the pollutant of concern, including location of the source(s) and the quantity of the loading, e.g., lbs/per day. The TMDL should provide the identification numbers of the NPDES permits within the waterbody. Where it is possible to separate natural background from nonpoint sources, the TMDL should include a description of the natural background. This information is necessary for EPA's review of the load and wasteload allocations, which are required by regulation. The TMDL submittal should also contain a description of any important assumptions made in developing the TMDL, such as:

(1) the spatial extent of the watershed in which the impaired waterbody is located; (2) the assumed distribution of land use in the watershed (e.g., urban, forested, agriculture); (3) population characteristics, wildlife resources, and other relevant information affecting the characterization of the pollutant of concern and its allocation to sources; (4) present and future growth trends, if taken into consideration in preparing the TMDL (e.g., the TMDL could include the design capacity of a wastewater treatment facility); and (5) an explanation and analytical basis for expressing the TMDL through surrogate measures, if applicable. Surrogate measures are parameters such as percent fines and turbidity for sediment impairments; chlorophyll-a and phosphorus loadings for excess algae; length of riparian buffer; or number of acres of best management practices.

Protocol for Minnesota Dissolved Oxygen TMDLs: See Minnesota’s Checklist (Appendix A) for background information needed in addition to the federal requirements.

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C. Description of the Applicable Water Quality Standards and Numeric Water Quality Target Federal Requirements: The TMDL submittal must include a description of the applicable State/Tribal water quality standard, including the designated use(s) of the waterbody, the applicable numeric or narrative water quality criterion, and the antidegradation policy. (40 C.F.R. §130.7(c)(1)). EPA needs this information to review the loading capacity determination, and load and wasteload allocations, which are required by regulation. The TMDL submittal must identify a numeric water quality target(s) - a quantitative value used to measure whether or not the applicable water quality standard is attained. Generally, the pollutant of concern and the numeric water quality target are, respectively, the chemical causing the impairment and the numeric criteria for that chemical (e.g., chromium) contained in the water quality standard. The TMDL expresses the relationship between any necessary reduction of the pollutant of concern and the attainment of the numeric water quality target. Occasionally, the pollutant of concern is different from the pollutant that is the subject of the numeric water quality target (e.g., when the pollutant of concern is phosphorus and the numeric water quality target is expressed as Dissolved Oxygen (DO) criteria). In such cases, the TMDL submittal should explain the linkage between the pollutant of concern and the chosen numeric water quality target. Protocol for Minnesota Dissolved Oxygen TMDLs: The Minnesota Rule 7050.0222 subp. 2,3,4,5 provides the numeric criteria for DO in Minnesota’s waters. A complete quotation from the Minnesota Rule 7050.0222 is provided on page 31. The numeric criterion for DO is a daily minimum. Compliance with this standard is required 50 percent of the days at which the flow of the receiving water is equal to the lowest weekly flow with a once in ten-year recurrence interval (7Q10). Two provisions are provided for specific reaches on the Mississippi River and the Minnesota River that are less restrictive but comply with Subpart 8 which allows for site specific standards but is limited to a 5 mg/l daily average and 4 mg/l daily minimum. Compliance with this standard is required 50 percent of the days at which the flow of the receiving water is equal to the lowest weekly flow with a once in ten-year recurrence interval (7Q10).

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D. Loading Capacity - Linking Water Quality and Pollutant Sources Federal Requirements: A TMDL must identify the loading capacity (LC) of a waterbody for the applicable pollutant. EPA regulations define LC as the greatest amount of a pollutant that a water can receive without violating water quality standards (40 C.F.R. §130.2(f)). The pollutant loadings may be expressed as either mass-per-time, toxicity or other appropriate measure (40 C.F.R. §130.2(i)). The TMDL must be expressed in terms of a daily load, but may additionally be expressed in terms other than a daily load, e.g., an annual load. The submittal should explain why it is appropriate to express the TMDL in the terms and units of measurement chosen. The TMDL submittal should describe the method used to establish the cause-and-effect relationship between the numeric target and the identified pollutant sources. In many instances, this method will be a water quality model. The TMDL submittal should contain documentation supporting the TMDL analysis, including the basis for any assumptions; a discussion of strengths and weaknesses in the analytical process; and results from any water quality modeling. EPA needs this information to review the LC determination, and load and wasteload allocations, which are required by regulation. TMDLs must take into account critical conditions for steam flow, loading, and water quality parameters as part of the analysis of LC. (40 C.F.R. §130.7(c)(1)). TMDLs should define applicable critical conditions and describe their approach to estimating both point and nonpoint source loadings under such critical conditions. In particular, the TMDL should discuss the approach used to compute and allocate nonpoint source loadings, e.g., meteorological conditions and land use distribution. Protocol for Minnesota Dissolved Oxygen TMDLs: As described in EPA guidance, a TMDL identifies the assimilative or LC of a waterbody for a particular pollutant. EPA regulations define LC as the greatest amount of loading that a waterbody can receive without violating water quality standards (40 C.F.R. § 130.2(f)). For impaired waterbodies, the LC will define the overall pollutant reductions that are necessary to attain water quality standards or achieve designated use for recreation, fisheries, drinking water supplies, aesthetics, and wildlife. DO is a response parameter and not a pollutant loading parameter. This requires that the LC be defined in the balanced allocation as a combination of all the contributing stressor parameters being allocated. It would simplify the TMDL if only one parameter allocation can be reduced to attain the water quality numeric limits, but if several of the stressor parameters are in need of reduction then LC of each must be described. This includes the physical parameter of temperature which would be given in a maximum daily value. The loadings are required to be expressed as either mass-per-time (pounds per day), toxicity, or some other appropriate measure (40 C.F.R. § 130.2(i)). As the term implies, TMDLs are typically expressed as total maximum daily loads, or loads per year. For example, it is appropriate and justifiable to express a DO TMDL in relationship to flow in terms of allowable loadings at the 7Q10 and increments higher as needed to balance all the sources of stress as they are introduced into the system under higher flow regimes. The TMDL submittal must identify the waterbody’s LC for the applicable pollutant and describe the rationale for the method used to establish the cause-and-effect relationships between the numeric target and designated uses to the identified pollutant sources. In most instances, this method will be a water quality model. Supporting

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documentation for the TMDL analysis also must be contained in the submittal, including the basis for assumptions, strengths and weaknesses in the analytical process, results from water quality modeling, etc.

Goal: Attain Designated Uses

• Achieve numerical goals

• Compliance Rate– 50% time at 7Q10– Other restrictive flow

goals as identified– Or, goal not to be

exceeded according to Subpart 8?

• Drinking Water• Fisheries• Recreation• Habitat• Wildlife• Aesthetics

Critical Condition TMDLs must take into account critical conditions for stream flow, and water quality parameter concentrations and loading, as part of the analysis of LC (40 C.F.R. §130.7(c)(1)). Factors, such as leaf canopy protection or the rate of human soil disturbance activities, affecting the critical conditions and the resulting TMDL often vary seasonally. Likewise, different sources may dominate the stressor parameter loading under different flow regimes. Dominance of nonpoint runoff related sources may significantly drop off during dry weather periods when point sources become a more significant portion of the loading. TMDLs should define applicable critical conditions that consider these source and delivery factors and the timing of when the beneficial use is impaired. Late summer low flow DO impairment can be impacted by loadings delivered earlier in the year and by loads occurring during the observed impairment, depending on watershed dynamics. In the Waste Load Allocation requirements for NPDES permitted wastewater facilities EPA requires that water quality protection exist down to a defined low flow condition. That low flow is defined as (7Q10): Low-flow (7Q10) is the 7-day average low flow occurring once in 10-years; this probability-based statistic is used in determining stream design flow conditions and for evaluating the water quality impact of effluent discharge limits. TMDLs should describe their approach to estimating both point and nonpoint source loadings under such critical conditions. In particular, the TMDL should discuss the approach used to compute and allocate nonpoint source loadings, e.g., meteorological conditions and land use distribution. For information on how to set up the study and the suggested rational for developing a TMDL study refer to Chapter 2, Section G. Critical Project Design Conditions (page 46) through Section I. Analysis (page 51) for the methods of identification of critical periods, modeling or analysis considerations, and frameworks for project process.

Dissolved Oxygen TMDL Protocols and Submittal Requirements

E. Load Allocations (LAs) Federal Requirements: EPA regulations require that a TMDL include LAs, which identify the portion of the LC attributed to existing and future nonpoint sources and to natural background. Load allocations may range from reasonably accurate estimates to gross allotments (40 C.F.R. §130.2(g)). Where possible, load allocations should be described separately for natural background and nonpoint sources. Protocol for Minnesota Dissolved Oxygen TMDLs: The load allocation (LA) is all those sources of pollutant loading not associated with a point source – non-NPDES or non-septic system. For DO TMDLs these sources include atmospheric deposition, natural land use such as limited use forests, grasslands, and wetlands and watershed runoff from managed land such as row cropped fields, silver culture, roads and non-MS4 communities. Natural background load is a portion of the watershed loading, and should be defined as precisely as possible. This analysis will range from having a value derived by multiplying a runoff coefficient for each critical stressor parameter times the spatial coverage of natural land uses that exist without roads and artificial drainage to a predictive model output for these uses. The LA should be as source specific as the data allows. Source specific could be by watershed sub-basin, land-use activity (agriculture), land-use sub-activity (row crop agriculture) or by individual sources (a particular row crop field). The more source specific the LA is, the more tailored the implementation recommendations can be. The location of sources in the watershed may need to be evaluated for its loading potential at the point of LC calculation. Load impact reductions from source location considerations (fate and transport) need to be documented to justify reduction allowances for loads entering surface waters. This consideration may apply to both the WLA and LA. Pollutant trading can be included as a means to meet a TMDL allocation. However, the details of trading can be determined in the TMDL implementation plan. Trading may further the need for geographic consideration of loads.

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F. Wasteload Allocations (WLAs) Federal Requirements: EPA regulations require that a TMDL include WLAs, which identify the portion of the LC allocated to individual existing and future point source(s) (40 C.F.R. §130.2(h), 40 C.F.R. §130.2(i)). In some cases, WLAs may cover more than one discharger, e.g., if the source is contained within a general permit. The individual WLAs may take the form of uniform percentage reductions or individual mass based limitations for dischargers where it can be shown that this solution meets WQSs and does not result in localized impairments. These individual WLAs may be adjusted during the NPDES permitting process. If the WLAs are adjusted, the individual effluent limits for each permit issued to a discharger on the impaired water must be consistent with the assumptions and requirements of the adjusted WLAs in the TMDL. If the WLAs are not adjusted, effluent limits contained in the permit must be consistent with the individual WLAs specified in the TMDL. If a draft permit provides for a higher load for a discharger than the corresponding individual WLA in the TMDL, the State/Tribe must demonstrate that the total WLA in the TMDL will be achieved through reductions in the remaining individual WLAs and that localized impairments will not result. All permittees should be notified of any deviations from the initial individual WLAs contained in the TMDL. EPA does not require the establishment of a new TMDL to reflect these revised allocations as long as the total WLA, as expressed in the TMDL, remains the same or decreases, and there is no reallocation between the total WLA and the total LA. Protocol for Minnesota Dissolved Oxygen TMDLs: In addition to the technical aspects of determining pollutant load allocations outline below, the process may also involve intensive stakeholder and policy-making efforts.

• WLA Sources All sources that are covered by a National Pollutant Discharge Elimination System (NPDES) permit plus certain septic systems are to be considered in the WLA. These sources, for the purpose of the TMDL should be referred to as point sources. Point Sources include:

• Public Owned Treatment Works (POTWs) and other Wastewater Treatment Facility

(WWTF) permittees with discrete discharges and explicit numeric discharge limits need to be included in the waste load allocation.

• NPDES stormwater permits, including from those communities designated as Phase I and

Phase II Municipal Separate Storm Sewer System (MS4s), and for permitted construction and industrial stormwater activities.

• Straight-Pipe Septic Systems: Straight-pipe septic systems are illegal and un-permitted, and

as such are assigned a zero wasteload allocation.

• Livestock facilities that have been issued NPDES permits are assigned a zero wasteload allocation. This is consistent with the conditions of the permits, which allow no pollutant discharge from the livestock housing facilities and associated site. Discharge of pollutants

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from fields where manure has been land applied may occur at times. Such discharges are covered under the load allocation portion of the TMDLs, provided the manure is applied in accordance with manure management provisions of the permit.

• It is important to note that all relevant NPDES permits in an impaired reach watershed need

to be listed individually in the TMDL document. To the extent possible and practical, individual WLAs should be established for NPDES dischargers, including regulated MS4s (see below – “Estimating WLAs”). Construction and industrial stormwater permits should get an individual WLA when deemed necessary, although categorical allocations may be the norm in most TMDLs.

• The location of sources in the watershed may need to be evaluated for their water quality

impact at the point of LC calculation. For example, while phosphorus entering surface waters is generally transported downstream, there may be specific instances where phosphorus load retention upstream of an impairment should be taken into account. In order to justify any allocation allowances based on source location, clear support and documentation is necessary. This consideration may apply to both the WLA and LA.

• Pollutant trading, including trading either between point sources or trading between point

sources and nonpoint sources, can be included in the TMDL and developed in detail in the subsequent implementation plan, as a means to meet a WLA. However, the MPCA’s trading policy has not been finalized. Trading may further the need for geographic consideration of loads.

• Water Quality Based Effluent Limits

As noted in the federal requirements in the box above, NPDES permits must be consistent with the assumptions and requirements of a TMDL’s wasteload allocation. Therefore, for Wastewater Facilities, water quality-based effluent limits contained in the permit must be consistent with the individual WLAs specified in the TMDL. In most cases, the WLA in the TMDL and effluent limit in the permit will be expressed in terms of mass. Attainment is needed at or above low flow conditions as defined by (7Q10). For regulated MS4s, water quality-based effluent limits may be in the form of Best Management Practice (BMPs) or in the form of numeric effluent limits. If data allows, the TMDL should define the percentage of the load allocation for each NPDES permitted facility and for each MS4.

• Estimating WLA Loads and Allocations

Wastewater point sources: For POTWs and industrial wastewater facilities, either the MPCA should be contacted for the electronically-available discharge monitoring reports (DMRs) for that facility, or the facility should be contacted directly. These data should be used to define the current WWTF phosphorus loading to the water body, which will serve as a basis for the allocations.

MS4 Stormwater: For estimating current loads from regulated MS4s and establishing allocations, each MS4 should be contacted for pertinent information. Current loading should be estimated as precisely as data allows. Guidance issued in 2002 from EPA (“Establishing Total Maximum Daily Load (TMDL) Wasteload Allocations (WLAs) for Storm Water Sources and NPDES Permit Requirements Based on

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Those WLAs” (November 22, 2002); http://www.epa.gov/npdes/pubs/final-wwtmdl.pdf) will be useful in determining your approach.

EPA notes that it may be reasonable to express NPDES-regulated storm water discharges from multiple point sources as a single categorical waste load allocation when data and information are insufficient to assign each source or outfall individual WLAs. More specifically, the waste load allocation in the TMDL can be expressed as either a 1) single number for all NPDES-regulated stormwater discharges, or 2) when information allows, as different WLAs for different categories, such as all MS4s separated out from construction and industrial stormwater and treated either in aggregate or as individual MS4s (City A vs. City B). In keeping with this guidance, the MPCA believes that many waste load allocations for regulated MS4s will be made in the aggregate by categorical sector (e.g. a 33 percent reduction for the MS4 sector) because of the insufficient quantity and quality of existing data on each individual MS4. However, if enough data exists, it is strongly encouraged that an individual WLA be set for each MS4 discharger. Here are examples of these two options: 1. Sector-wide allocation: A TMDL could find that all regulated MS4 sources together

contribute a total of 300 lbs. of phosphorus and a load reduction of 100 lbs. is necessary to meet the WLA goal, or roughly a 33 percent load reduction. All MS4s would be evaluated together to achieve the load reduction of 100 lbs.

2. Individual allocation (Also see detailed guidance in Appendix B developed for the Minnesota

River low dissolved oxygen TMDL).

a.) If a city-by-city WLA approach for MS4s is preferred, the MPCA proposes that the WLA be divided equally among MS4s, in proportion to the size of their contributing watershed. For example, the TMDL finds that a 33% reduction (equivalent to 100 lbs. of phosphorus) is needed. The total contribution from three cities in a TMDL watershed is 300 lbs. and the total WLA requires a reduction of 100 lbs of phosphorous. If cities A, B, and C together have 100% of the impaired watershed, and City A’s permit boundaries cover 80%, City B’s 10% and City C’s 10%, then the load allocation for City A’s reduction goal would be 80 lbs, and City B and C would be 10 lbs each. However, all three cities reduce the same proportional amount of phosphorus.

b.) If sufficient water quality data exists on specific MS4 contributions and applied BMPs, a

more tailored WLA can be set for each city. For example, if a city has eliminated its illicit discharges while another city has not, equal load reductions may not be equitable.

• NPDES Permit Compliance Schedules and Water Quality Trading

Federal regulations set requirements for NPDES permit compliance schedules to meet effluent limits. In general, there are two expectations:

1. Each NPDES permit must meet effluent requirements; and 2. The compliance schedule for meeting the requirements should be within one permit

cycle.

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Despite these expectations, there is flexibility in setting permit compliance schedules to meet TMDL WLAs in certain situations. It is important that TMDL project teams discuss these situations with MPCA permitting staff as WLAs are being developed to ensure that compliance schedules are set appropriately. Compliance Options for Wastewater Facility Permits: As noted above, there is an expectation for all wastewater NPDES permits to meet the TMDL WLA in the first five-year permit cycle. However, there can be exceptions to this process when justified:

1) Multiple TMDLs in the same watershed: When NPDES permitted facilities may have to comply with more than one TMDL for the same pollutant parameter but are on different completion timelines, a longer compliance schedule may be necessary. This is to ensure that facility upgrades are made to meet the most restrictive TMDL WLA (i.e., the TMDL that may require more restrictive limits or longer seasonal application of the limits).

For example, in the case of the Minnesota River low dissolved oxygen TMDL, the critical period was during summer months. However for the Lake Pepin excess nutrient TMDL, the critical period will most likely be year-round. Therefore, the upgrade of the facilities for the seasonal effluent limitation versus the upgrade needed for year-round treatment can be significantly different. Setting milestone markers until the other TMDL studies are completed will minimize the occurrence of new or expanding systems being built that are immediately required to upgrade again to meet a more restrictive TMDL.

It is important to discuss this type of justification (including expected timelines for milestones and steps necessary to meet them) in the TMDL report to clarify how NPDES permit compliance schedules will meet the TMDL’s WLA.

2) Pollutant Trading and Watershed Permits: For NPDES-permitted wastewater facilities

that may not be able to meet a TMDL WLA, two options are emerging: pollutant trading and watershed permitting. A policy for the first option, pollutant trading, is currently being developed by the MPCA. Trading enables entities located upstream of a given impairment to work together to cumulatively achieve the WLA. Pollutant trading can benefit dischargers by using either the benefits of economy of scale, or by limiting the upgrades or installations of BMPs (in the case of point to nonpoint trading) to those that are the least expensive and “trading” the activities of the most expensive for an equivalent reduction or a net pollutant load decrease.

The second option, a watershed permit, allows all NPDES activities to be sequenced and considered on a cumulative basis in a watershed. In this process, a cumulative problem can be solved by sequencing all the NPDES permits to implement a specified set of reductions across a given timeframe. This has the potential to accelerate implementation schedules and also provides a better opportunity to set expectations for reductions at an equitable level.

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It is important that if either of these alternatives are factored into final TMDL implementation strategies to meet a WLA, they are discussed in the TMDL report. This will provide guidance on permit compliance schedules and/or the use of more flexible compliance alternatives. Compliance Options for Stormwater Permits: TMDL WLAs for regulated MS4s should reflect the timing required to retrofit existing developed areas with BMPs and to set adequate milestones for developing areas. In general, it should be assumed that multiple permit schedules will be needed to meet TMDL reduction targets and the regulated MS4 needs to make progress in each permit cycle to meet a WLA. Progress indicators include establishing a stormwater program, doing good housekeeping, addressing retrofits and new development, prevention and education, and structural BMPs. If the TMDL study has enough data to set reduction milestone timelines and goals, then the SWPPP for each permit cycle can reference the TMDL and the milestones to justify its compliance with the TMDL. Other options are also possible: 1) Phased TMDLs: For instances where the TMDL study has significant uncertainty about

stormwater loadings and management practices to effectively address that loading, an EPA memorandum dated August 2, 2006 entitled Clarification Regarding “Phased” Total Maximum Daily Loads (http://www.epa.gov/owow/tmdl/tmdl_clarification_letter.pdf) outlines acceptable methods to discuss “phased” approaches in the TMDL study.

As noted in this document, “phased TMDLs be limited to TMDLs that for scheduling reasons need be established despite significant data uncertainty and where the State expects the loading capacity and allocation scheme will be revised in the near future as additional information is collected.” The document cites examples of situations where this may apply, including lake nutrient TMDLs where there are uncertain loadings from major land uses and/or limited knowledge of in-lake processes. As with any TMDL, each phase must be established to attain and maintain the applicable water quality standard and would require re-approval by EPA if the LC, wasteload or load allocations are revised.

For stormwater TMDLs using a phased approach, collection of missing data needed to assess loading or management practices would be required through SWPPPs. This should be clearly discussed in the TMDL report.

2) Pollutant Trading: EPA is currently developing an approach for stormwater pollutant

trading. There are a few pilot programs ongoing at the national level testing the situations that would provide clarity on how and when stormwater pollutant trading would be allowed. The MPCA will be developing options in this area as well.

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References:

“Establishing Total Maximum Daily Load (TMDL) Wasteload Allocations (WLAs) for Storm Water Sources and NPDES Permit Requirements Based on Those WLAs” (November 22, 2002); http://www.epa.gov/npdes/pubs/final-wwtmdl.pdf Appendix B: “Guidance for Communities on How to Estimate and Achieve Phosphorus Reductions and Report it in their SWPPPs”

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G. Margin of Safety (MOS) Federal Requirements: The statute and regulations require that a TMDL include a margin of safety (MOS) to account for any lack of knowledge concerning the relationship between load and wasteload allocations and water quality (CWA §303(d)(1)(C), 40 C.F.R. §130.7(c)(1) ). EPA's 1991 TMDL Guidance explains that the MOS may be implicit, i.e., incorporated into the TMDL through conservative assumptions in the analysis, or explicit, i.e., expressed in the TMDL as loadings set aside for the MOS. If the MOS is implicit, the conservative assumptions in the analysis that account for the MOS must be described. If the MOS is explicit, the loading set aside for the MOS must be identified. Protocol for Minnesota Dissolved Oxygen TMDLs: The rationale for selecting the MOS and its adequacy must be included in the TMDL submittal. As indicated in the federal requirement, an explicit MOS would include setting a portion of the LC aside as the MOS (i.e., not allocated to any source). Examples of an implicit margin of safety include the use of conservative assumptions in selecting a numeric water quality target and predicting the performance of best management practices. A related implicit MOS is the use of conservative design criteria for the sizing of best management practices.

TMDL = Background + ∑ LA+ ∑WLA + MOSNatural or Non-Point Point Sources Margin of SafetyUnregulated

Regional Runoff Urban WWTF VariabilityAtmospheric Agriculture SW MS4 Uncertainty

Silvaculture Industrial Transportation Commercial

ISTS

Expected Long-Term-Average Load to Water

+Consideration of Future Growth as Reserve Capacity

The basic purpose of the MOS component of the TMDL equation is provide additional assurance that the projected load estimation process will attain water quality numeric standards and to allow the project a reasonably high likelihood of success. As such, MOS encompasses two primary factors affecting these outcomes: variability and uncertainty. “Variability” refers to the fluctuations in measured values for a given parameter across flow regimes, up and down the reaches (spatially) and as well as by temporal factors - such as within year (seasonal) and year-to-year changes (induced by climatic conditions and

Dissolved Oxygen TMDL Protocols and Submittal Requirements

biological response). “Uncertainty” refers to prediction error resulting from limits in the data and predictive models. Walker (2001 & 2003) has provided detailed discussions of these subjects and the reader is directed to these articles for more detail on the topic. The Margin of Safety should not encompass future growth or allocations of reserve capacity. It is encouraged that these aspects of assimilation capacity should be dealt with as a separate allocation explicitly stated as a part of the formal TMDL process. In instances where there is a scarcity of data, the TMDL components need to be estimated with greater uncertainties and hence, higher MOS. As more data is collected, estimates of variability and uncertainty can be reduced thereby allowing a smaller MOS component – and greater allocations to the other components balancing the TMDL equation. In short, if there are limited data available, a model based portrayal may have to suffice until more monitoring is conducted. Alternatives to explicit Margin of Safety expressions include: conservative water quality criteria/standards, conservative reduction goals, conservative modeling assumptions, conservative effluent limits/ discharge permits, conservative BMP designs, and/or conservative growth projections. In these cases, the MOS is included in the other terms of the TMDL equation and is not explicitly quantified, either in terms of load or the corresponding risk that the goals will be achieved (Walker, 2001). Hence, the risk of making improper management decisions can become larger. Uncertainty Estimates Uncertainty analyses should be included in TMDL allocations, ranging from the model professional contract if one is used or by the technical team members using the analysis tool selected. Refer to Chapter 2 for details on the options for analysis and methods to test the predictive capability of the assessment tool. In summary on these topics Walker (2003) cautions against setting an unrealistically high confidence level and/or compliance rates as TMDL goals. A high MOS could hinder progress of restoration by increasing costs, reducing credibility, and stimulating controversy. Rather, he suggests an incremental or adaptive approach to achieving the desired compliance rate and confidence level through successive TMDLs as may be appropriate, as recommended by the National Research Council (2001). This will often be the case in TMDLs where a majority of the loading which needs be reduced to achieve the TMDL, arises from unregulated nonpoint source runoff, or as Walker (2003) states, “a phased approach is applicable where the load allocation is not immediately achievable (with or without an MOS) because of limits in control technology.” In any case, the TMDL equation must be written such that the TMDL is met by the allocations.

References:

Walker, 2001 and 2003.

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H. Reserve Capacity (allocation for future growth)

Federal Requirements: Implied under LA and WLA requirements as the “portion of the loading capacity attributed to existing and future sources” Protocol for Minnesota Dissolved Oxygen TMDLs: Reserve Capacity is that portion of the TMDL that accommodates future loads. The MPCA’s policy on reserve capacity is that it be considered by all TMDL projects and the final report should clearly describe the rationale for a decision regarding this issue. Inclusion of an allocation for reserve capacity in the TMDL is strongly encouraged. Reserve capacity can be ascribed singly to the WLA, the LA or both; e.g. new and expanding WWTF’s, MS4s that will be covered by a permit in the future or that are permitted now and may expand, and/or land use changes. If an allocation for reserve capacity is not included, either no new future loads are anticipated or allowed, or increased loads must be accommodated by pollutant trading. In the case of MS4s, growth may also be accommodated in the WLA based on larger municipal boundaries or expansion area designations, if appropriate. If reserve capacity is accommodated by trading only, a discussion of a viable trading program and the implications to new loads should be included. A typical 20-year planning timeline for consideration of reserve capacity is recommended. The TMDL report should provide the basis for the amount of reserve capacity, guidelines for making reserve capacity available to new loads, and the means to replenishing reserve capacity when it has been depleted. Replenishing reserve capacity can be accomplished through the following options: WWTF sources

• Concentration adjustments – reallocation based on concentration effluent limits at the given design flow;

• Flow adjustments – reallocation of allowed design flow at the given concentration; or • Mass adjustments – mass-based effluent limit

Nonpoint sources and MS4s • Additional BMP implementation • Reducing watershed loads

General

• Reducing margin of safety through greater understanding of load response conditions. It is anticipated that reserve capacity issues will largely be a policy discussion that requires input from all affected parties and consideration of future loads in the watershed. Policy considerations for allocating reserve capacity to new loads should be based on an equitable and consistent set of criteria. In the case of WWTFs, it may not be completely possible to anticipate all new future loads. An example of this would be those loads from new unplanned industrial sources. If this appears a likely scenario, an increased reserve capacity over that anticipated to be necessary may be warranted.

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The allocation of reserve capacity should be fully documented so that any future reallocation can consider past allocation changes. Additionally, reserve capacity balances must be documented at all times. This should include detailed documentation of all new loads that have been transferred to the WLA and LA. Consideration may be given to requiring new loads to provide a higher level of treatment/BMP implementation to access reserve capacity. For example, if WWTFs are generally meeting a 1.0 mg/L phosphorus effluent limitation, a 0.5 mg/L phosphorus limit may be a criteria to access reserve capacity. New loads from new sources or expanded sources may be treated the same or differently.

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I. Seasonal Variation Federal Requirements: The statute and regulations require that a TMDL be established with consideration of seasonal variations. The TMDL must describe the method chosen for including seasonal variations. (CWA §303(d)(1)(C), 40 C.F.R. §130.7(c)(1)). Protocol for Minnesota Dissolved Oxygen TMDLs: Nothing additional at this time. J. Reasonable Assurances Federal Requirements: When a TMDL is developed for waters impaired by point sources only, the issuance of a National Pollutant Discharge Elimination System (NPDES) permit(s) provides the reasonable assurance that the wasteload allocations contained in the TMDL will be achieved. This is because 40 C.F.R. 122.44(d)(1)(vii)(B) requires that effluent limits in permits be consistent with "the assumptions and requirements of any available wasteload allocation" in an approved TMDL. When a TMDL is developed for waters impaired by both point and nonpoint sources, and the WLA is based on an assumption that nonpoint source load reductions will occur, EPA's 1991 TMDL Guidance states that the TMDL should provide reasonable assurances that nonpoint source control measures will achieve expected load reductions in order for the TMDL to be approvable. This information is necessary for EPA to determine that the TMDL, including the load and wasteload allocations, has been established at a level necessary to implement water quality standards. EPA's August 1997 TMDL Guidance also directs EPA Regions to work with States to achieve TMDL load allocations in waters impaired only by nonpoint sources. However, EPA cannot disapprove a TMDL for nonpoint source-only impaired waters, which do not have a demonstration of reasonable assurance that LAs will be achieved, because such a showing is not required by current regulations. Protocol for Minnesota Dissolved Oxygen TMDLs: Generally, reasonable assurances include descriptions of the regulatory and nonregulatory efforts at the state and local levels that will likely result in reductions from the load allocation portion of the TMDL. Reasonable Assurances also include the identification of potential or likely funding sources that will enable reductions from the load allocation. The following list of scenarios describes when to include Reasonable Assurances in the TMDL submittal: • Nonpoint source only TMDLs (Load Allocation only):

Although EPA does not require reasonable assurances in this type of TMDL, the MPCA requires a description of reasonable assurances for nonpoint only TMDLs. Reasonable assurances in these

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types of TMDLs allow the MPCA to evaluate the potential options available to enable reductions from nonpoint sources.

• TMDLs with offsets in the Waste Load Allocation from the Load Allocation:

EPA requires reasonable assurances in this situation in order to approve the TMDL. This is clarified in the 1991 EPA guidance document, Guidance for Water Quality-Based Decisions: The TMDL Process. The guidance addresses waters impaired by both point and nonpoint sources where the wasteload allocation to point sources is not as strict because of nonpoint source loading reductions. In such cases, some additional provisions in the TMDL, such as a schedule and description of the implementation mechanisms for nonpoint source control measures, are needed to provide reasonable assurance that the nonpoint source measures will achieve the expected load reductions. Such additional provisions are needed in this type of TMDL to assure compliance with the federal regulations at 40 CFR 130.2(i), which require that in order for wasteload allocations to be made less stringent, more stringent load allocations must be “practicable.”

• TMDLs without offsets in the Waste Load Allocation from the Load Allocation:

Although EPA does not require reasonable assurances in this type of TMDL, the MPCA requires a description of reasonable assurances. Reasonable assurances in these types of TMDLs allow the MPCA to evaluate the potential options available to enable reductions from nonpoint sources.

• TMDLs with wastewater permittees in the Waste Load Allocation:

Where the reductions are stemming solely from wastewater permittees without LA reductions for attainment goals, or the permits are at Best Available Technology, reasonable assurances are not required for wastewater permittees because federal regulations require that permits with numeric effluent limits comply with the Waste Load Allocation in the TMDL.

• TMDLs with required and discretionary MS4 stormwater permittees in the Waste Load

Allocation: As noted in the box above, NPDES permit requirements must be consistent with the assumptions and requirements of available WLAs. See 122.44(d)(1)(vii)(B). Since permits for required and discretionary MS4 do not contain numeric limits, the MPCA requires an MS4 to provide reasonable assurances in the following manner:

“If a USEPA-approved TMDL(s) has been developed, you must review the adequacy of your Storm Water Pollution Prevention Program to meet the TMDL’s Waste Load Allocation set for storm water sources. If the Storm Water Pollution Prevention Program is not meeting the applicable requirements, schedules, and objectives of the TMDL, you must modify your Storm Water Pollution Prevention Program, as appropriate, within 18 months after the TMDL is approved.”

This permit language should be cited in the reasonable assurance section of the TMDL. In addition, note that the implementation plan, likely to be finalized one year following EPA approval of the TMDL, will identify specific BMP opportunities sufficient to achieve their load reduction and their adoption schedule, and the individual SWPPPs would be modified accordingly following the recommendations of this plan.

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TMDLs with construction stormwater permittees in the Waste Load Allocation: As noted in the Federal Requirements section above, NPDES permit requirements must be consistent with the assumptions and requirements of available WLAs. (See CWA section 122.44(d)(1)(vii)(B)). Since permits for construction stormwater do not contain numeric limits, the MPCA requires a construction stormwater permittee to provide reasonable assurances by citing the TMDL compliance requirements of provisions in the NPDES Construction Stormwater Permit (Part I.B.7, Part III.A.4.d, and Part III.A.7). According to Part I.B.7 of the General Permit:

“Discharges to waters for which there is a total maximum daily load (TMDL) allocation for sediment and parameters associated with sediment transport are not eligible for coverage under this permit unless the Permittee(s) develop and certify a SWPPP that is consistent with the assumptions, allocations and requirements in the approved TMDL. To be eligible for coverage under this general permit, Permittee(s) must incorporate into their SWPPP any conditions applicable to their discharges necessary for consistency with the assumptions, allocations and requirements of the TMDL within any timeframes established in the TMDL. The SWPPP must include the provisions in Part III.A.7. If a specific numeric wasteload allocation has been established that would apply to the project's discharges, the Permittee(s) must incorporate that allocation into its SWPPP and implement necessary steps to meet that allocation.”

As with MS4s, the permit language above should be cited in the reasonable assurance section of the TMDL. Note that the implementation plan, to be finalized within one year following EPA approval of the TMDL, will identify specific BMP opportunities sufficient to achieve their load reduction and their adoption schedule, and the individual SWPPPs would be modified accordingly following the recommendations of this plan.

References:

EPA's 1991 document, Guidance for Water Quality-Based Decisions: The TMDL Process (EPA 440/4-91-001) http://www.epa.gov/OWOW/tmdl/decisions/

MS4 permit requirements: http://www.pca.state.mn.us/water/stormwater/stormwater-ms4.html#requirements

Construction stormwater permit requirements: http://www.pca.state.mn.us/water/stormwater/stormwater-c.html#forms

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K. Monitoring Plan to Track TMDL Effectiveness Federal Requirements: EPA's 1991 document, Guidance for Water Quality-Based Decisions: The TMDL Process (EPA 440/4-91-001) http://www.epa.gov/OWOW/tmdl/decisions/ recommends a monitoring plan to track the effectiveness of a TMDL, particularly when a TMDL involves both point and nonpoint sources and the WLA is based on an assumption that nonpoint source load reductions will occur. Such a TMDL should provide assurances that nonpoint source controls will achieve expected load reductions, and should include a monitoring plan that describes the additional data to be collected to determine if the load reductions provided for in the TMDL are occurring and leading to attainment of water quality standards. Protocol for Minnesota Dissolved Oxygen TMDLs: A monitoring plan associated with DO TMDLs offers an opportunity to focus existing monitoring activities in the watershed, as well as identify additional needs toward achieving the common goals of assessing and improving water quality. Many of Minnesota’s waters have active watershed associations that routinely collect water quality data and information. The monitoring plan for the TMDL could outline how collaborative monitoring efforts could be used to better define sources, target sources for control actions, evaluate the effectiveness of controls, and ultimately assess the adequacy of the TMDL. The watershed assessment options presented in Chapter 2 provide multiple methods to gather monitoring data. Data sets can vary from relatively few data to progressively more sophisticated studies. Generalized monitoring designs for streams and watersheds are presented below. In addition, it is also recommended that the reader review EPA’s clarifying guidance on three situations where follow-up monitoring strategies are needed to provide assurances that nonpoint source controls will be achieved: “phased TMDLs”, “adaptive implementation” and “staged implementation” http://www.epa.gov/owow/tmdl/tmdl_clarification_letter.html . Figure 21: Iterative TMDL Process

Schematic of TMDL Adaptive Management (Walker, 2001) Monitoring – Rivers

Dissolved Oxygen TMDL Protocols and Submittal Requirements

Consideration of critical conditions and the analysis tool used to assess the progress towards compliance with the numeric criteria is the first step to designing an effectiveness monitoring program for DO in rivers. The summer low flow condition is often the primary critical condition designed for. However, the 1 in 10-year low flow return frequency is based on probability and may not occur until much later than the first decade. For instance, the last 7Q10 condition in the Minnesota River was in 1988. Therefore, it is necessary to implement a monitoring program that will track the resource conditions as implementation activities take place regardless of flow conditions, so that it will be able to be used to estimate the progress in a flow regime where monitoring data is not available. Delisting will only be possible after the critical conditions have existed and adequate monitoring can be provided that demonstrates the system to be in complete water quality attainment. Monitoring Change Tracking of water quality changes over time resulting from the implementation of watershed and lake rehabilitations can be reasonably accomplished with due consideration of time lags, geographic scale, monitoring approaches and quality assurance. The monitoring efforts in Minnesota have been routine based (every month or every two weeks), and event based with consideration to continuous measurement of flows. Whether the monitoring data is collected by grab sampling, or by storm hydrograph sampling by automated equipment depends on the project goals and station location to field crew. However, with many parameters needed to track progress in DO TMDLs, limited holding times for parameters such as CBOD need to be considered. Key parameters to select from are the field parameters of pH, DO, and temperature, plus the analytical parameters of total phosphorus, total suspended solids, TKN, Chl-a. The selection will depend both on the analysis tool used for tracking progress (suggested to be the analysis tool utilized in the TMDL) and the critical parameters identified by the TMDL. In addition, the implementation of significant percentages of BMPs or treatment measures needs to be in place prior to initiating the "after" condition water quality monitoring efforts. It is suggested that upon obtaining a good "prior" condition baseline, that a skewed rollout be used, with the more significant resource monitoring being initiated after 60 percent or more of the reduction measures are implemented (this percentage best applied by load, however if not available then a number count of the measures can be done). This requires adequate land use tracking efforts to be set up and in place during the implementation period, such as e-Link, the residue transect survey, wastewater DMR reports, county feedlot inventories and others as determined by the specific TMDL.

Time Lags Before and after monitoring - Quality assurance plans are required for TMDL projects by ensuring that appropriate field and laboratory procedures are employed. Use of certified labs is a part of this quality assurance process. Other typical quality assurance aspects include consideration of:

• accuracy as a function of methods (field and laboratory); • precision as a function of methods, and sample frequency; and • probability of detecting change as a function of precision, variability, and duration of

sampling, much of which was described in previous sections of this document.

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Over the course of a watershed management effort, there can be significant time periods that occur from the time of recognition of water quality problems, rehabilitation of key watershed areas and improvement of water quality. Projects usually begin with a one to three year diagnostic study coupled with building requisite local partnerships. Additional time is needed for public notices and contracts leading up to planning and design of watershed corrective actions. The final leg of the restoration journey involves BMP construction, usually coupled with vegetative re-growth. All of these changes need to occur before the stream has a chance to reach attainment. After implementation and establishment of all the treatment measures the flow regimes in the stream may need to be from a wet weather period to be high enough to flush SOD out of the system prior to the complete compliance attainment. Geographic scale and Rehabilitation Sequencing The size of the contributing watershed to a given impaired reach will be a large determinant in the time and effort needed to affect improved water quality. The monitoring options defined in the above guidelines will help guide establishment of required stream flow gauging and sampling efforts, with smaller areas showing changes more quickly. Smaller watersheds can be typically expected to respond more quickly to watershed corrective measures. Large watershed projects are encouraged to develop smaller, more optimal detection tracking project areas. References:

EPA 2006. Clarification regarding “Phased Total Maximum Daily Loads”

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L. Implementation Federal Requirements: EPA policy encourages Regions to work in partnership with States/Tribes to achieve nonpoint source load allocations established for 303(d)-listed waters impaired by nonpoint sources. Regions may assist States/Tribes in developing implementation plans that include reasonable assurances that nonpoint source LAs established in TMDLs for waters impaired solely or primarily by nonpoint sources will in fact be achieved. In addition, EPA policy recognizes that other relevant watershed management processes may be used in the TMDL process. EPA is not required to and does not approve TMDL implementation plans. Protocol for Minnesota Dissolved Oxygen TMDLs: For DO TMDLs, the detailed and site specific implementation planning will take place during the Implementation Plan development. Projects must include in the written TMDL submitted to MPCA the broad implementation strategies to be refined and finalized after the TMDL is approved. Projects are required to submit a separate, more detailed implementation plan document to MPCA within one year of the TMDL’s approval by EPA. For example, highly complex TMDLs or TMDLs requiring reductions for NPDES-permitted point sources (wastewater, stormwater, feedlots) may require this additional time following approval to prepare detailed implementation plans. The Minnesota Clean Water Legacy Act requires a range of implementation costs to be included in the TMDL. It is recommended that a range of probable costs be included in the discussion by land use type. For instance, large watershed scale TMDLs may have significant implementation cost ranges due to the large number of measures needed, even though they are implementing the least expensive measure on a unit cost basis. The factors that contribute to or control the cost estimate ranges should be broadly outlined in the narrative. For further information on implementation plan requirements, review MPCA’s TMDL work plan guidance at http://www.pca.state.mn.us/publications/wq-iw1-01.pdf and the MPCA policy on implementation plans at http://intranet.pca.state.mn.us/policies/programpolicies/i-wq2-031.pdf . In the DO TMDL implementation plan section, the broad implementation strategies, activity areas, and mechanisms for achieving loading reductions should be identified. The implementation plan section should identify:

• How the public will be involved. • What mechanisms such as financial assistance, ordinances etc., exist or are proposed for

development. • How progress will be monitored such as WQ monitoring, BMP tracking etc. • How control activities will be sited. • What planning tools or processes will be used to achieve nonpoint source reductions. • What planning tools, processes, ordinances are in-place or will be proposed to control point

sources.

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• What educational and cooperative efforts among stakeholders, landowners, and agencies exist or a proposed for development.

• What time period each sector will be given for adoption goals, retrofitting and implementation of structural measures.

For MS4s, this section of the TMDL should provide a high level overview of activities that will be refined in the implementation plan. Providing this information will help enhance reasonable assurance, including:

• The current BMPs that are planned (to be refined during implementation planning and SWPPP development);

• The current schedule (i.e., how many permit cycles) for putting BMPs in place; and • Expected range of potential reductions, based on literature, which can be achieved for each

category of BMP (e.g., citizen education program, stormwater ponds, alum treatment, etc.). Note: Additional guidance on this is currently being developed by the MPCA.

References:

MPCA’s TMDL work plan and implementation plan guidance.

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M. Public Participation Federal Requirements: EPA policy is that there should be full and meaningful public participation in the TMDL development process. The TMDL regulations require that each State/Tribe must subject draft TMDLs to public review, consistent with its own continuing planning process (40 C.F.R. §130.7(c)(1)(ii)). In guidance, EPA has explained that final TMDLs submitted to EPA for review and approval should describe the State's/Tribe's public participation process, including a summary of significant comments and the State's/Tribe's responses to those comments. When EPA establishes a TMDL, EPA regulations require EPA to publish a notice seeking public comment (40 C.F.R. §130.7(d)(2)). Provision of inadequate public participation may be a basis for disapproving a TMDL. If EPA determines that a State/Tribe has not provided adequate public participation, EPA may defer its approval action until adequate public participation has been provided for, either by the State/Tribe or by EPA. Protocol for Minnesota Dissolved Oxygen TMDLs: An active stakeholder and public participation process is required throughout the development of every TMDL, from the development of the project workplan to the approval of final pollutant load allocations and public notice process. The ultimate success of the project is in large part dependent upon the effectiveness of this process, and development of practical, pragmatic solutions with stakeholders is fundamental. It is critical that the diverse stakeholders affected by any given TMDL project (and those who must implement it) share a common understanding of the problem and what is needed to solve it. Public participation is also required through the 2006 Clean Water Legacy Act which requires the MPCA to seek “broad and early public and stakeholder participation in scoping the activities necessary to develop a TMDL, including the scientific models, methods, and approaches to be used in TMDL development, and to implement restoration…” Based on the recommendations of a broad-based group of stakeholders (“The G16”) advising the MPCA on TMDLs, the MPCA has piloted an intensive public participation process through its Lake Pepin TMDL. The results of this process will be critical to determining guidance for other TMDL projects. This will include development of a stakeholder advisory group which will provide recommendations on a project throughout the process. The stakeholder advisory group can also receive advice on technical issues from a technical/science advisory group, comprised of experts from academia and other institutions. More information on this structure and process can be found by referring to a fact sheet on the Lake Pepin project: http://www.pca.state.mn.us/publications/wq-iw9-01f.pdf Probably the most critical phase of a stakeholder advisory group process is in developing and making recommendations for source reductions and pollutant load allocations (load allocations, wasteload allocations, margin of safety, and reserve capacity). Federal regulations specify only that the total allocations (point source and nonpoint source, margin of safety) prescribed by a given TMDL must satisfy water quality standards for that water’s designated use. The specific method for allocating pollutant loads among sources is a policy issue that must be determined by states according to their own priorities and judgment.

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The MPCA will carefully consider stakeholder recommendations and the MPCA’s final decision will be made after considering a range of allocation options, ensuring that they meet water quality standards, are technically and practically feasible, and are consistent with other regulatory programs that might apply. In addition, competing measures of desirability (where regulatory flexibility allows), such as cost-effectiveness and equity, will be critical factors in determining load allocations. More specifically, final policy decisions on allocations should reflect public and stakeholder perceptions about acceptable tradeoffs. For example, strategies that minimize costs may be perceived as unfair if particular sources carry most of the load reduction, while allocations based on equal load reductions may be more costly. Other factors that should be considered when making allocation decisions include relative source contributions, technical limitations of any given source to reduce, ability of small entities to pay, and prior load reductions. Additional information on the allocation process and options can be found at these EPA websites: http://www.epa.gov/waterscience/models/allocation/def.htm; and http://www.epa.gov/waterscience/models/allocation/19schemes.htm. Local government (contractors) will have a primary role throughout the public participation process. In general, local government should be prepared to be engaged in these public participation activities:

• Help identify stakeholders that can represent diverse public and private interests in affected watersheds on the Stakeholder Advisory Group for the project.

• Conduct public outreach and education activities at key points throughout the project and prepare a report or section of the draft TMDL that describes those activities.

• Coordinate with the MPCA as needed to assist in the formal public notice process for the draft TMDL, including:

o Help organize a public meeting(s) for the draft TMDL and compile comments from the public.

o Help respond to comments, as needed, on the draft TMDL from technical staff, citizens and other interested parties, and EPA.

o Submit public outreach materials along with the draft TMDL or final report, such as charts, graphs, modeling runs, fact sheets, presentation materials, maps, etc.

Following the allocation process and the final development of a draft, the public notice process can begin. These steps will be led by the MPCA, coordinating with the local government contractor. Most activities will be conducted by the project manager, basin coordinator, public information officer, or impaired waters coordinator, as appropriate. In general, following are the basic steps to the public notice process:

1. MPCA public information staff and project manager prepare public notice package, to include draft TMDL, fact sheet, public notice and news release.

2. Public Notice o The draft TMDL must be on public notice for a minimum of 30 days. o The public notice must be published in the State Register. o The notice must be published on the MPCA Web site.

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o The notice should also be mailed or e-mailed to a list of interested parties for the project, and must be mailed to a statewide list of interested parties maintained by the impaired waters program coordinator.

o Public meetings during the public notice phase will be determined based on the level of public participation and outreach during other phases of the project.

3. Public comments: All written public comments must be provided to EPA with the submission of the TMDL. Copies of each comment letter must also be submitted.

4. Final MPCA approvals (either by the Commissioner or the Citizens Board). 5. The TMDL is submitted to EPA for final approval. In accordance with the 2006 Clean Water

Legacy Act (114D.25), the final TMDL is submitted to EPA no sooner than 30-days following the conclusion of the public notice period.

References: 2004 Impaired Waters Legislative Report: Impaired Waters Stakeholder Process: Policy Framework: http://www.pca.state.mn.us/publications/reports/lrwq-iw-1sy04.pdf

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N. Submittal Letter Federal Requirements: A submittal letter should be included with the TMDL submittal, and should specify whether the TMDL is being submitted for a technical review or final review and approval. Each final TMDL submitted to EPA should be accompanied by a submittal letter that explicitly states that the submittal is a final TMDL submitted under Section 303(d) of the Clean Water Act for EPA review and approval. This clearly establishes the State's intent to submit, and EPA's duty to review, the TMDL under the statute. The submittal letter, whether for technical review or final review and approval, should contain such identifying information as the name and location of the waterbody, and the pollutant(s) of concern. Protocol for Minnesota Dissolved Oxygen TMDLs: The submittal letter is written by the MPCA and signed by the Commissioner. In addition, the final TMDL report, and any other documents that are a necessary part of the TMDL submittal are ultimately approved by the Commissioner. In accordance with Minn. Stat. Sec. 114D.25, MPCA will submit the TMDL to the U.S. Environmental Protection Agency for review and final approval after a 30-day waiting period upon agency approval. This delay and notice will be facilitated by the TMDL coordinator position at the MPCA. O. Administrative Record Federal Requirements: While not a necessary part of the submittal to EPA, the State should also prepare an administrative record containing documents that support the establishment of the TMDL and calculations/allocations in the TMDL. Components of the record should include all materials relied upon by the State to develop and support the calculations/allocations in the TMDL, including any data, analyses, or scientific/technical references that were used, records of correspondence with stakeholders and EPA, responses to public comments, and other supporting materials. This record is needed to facilitate public and/or EPA review of the TMDL. Protocol for Minnesota Dissolved Oxygen TMDLs: The MPCA project manager and administrative staff will gather and file all necessary documents for the administrative record.

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Appendix A

Minnesota’s TMDL submittal checklist

This checklist outlines the basic needs for all TMDLs. It is used by MPCA management prior to submittal to EPA. It supplements the detailed description from EPA’s review guidelines found in Chapter 3 TMDL Submission Requirements

Item Page Adequate (yes/no) Comments

Executive Summary – should briefly summarize the key findings in each of the sections below, particularly the final allocation of pollutant loads.

Background Information, including: - Spatial extent of watershed (HUC codes are

helpful)

- Waterbody identified as on list (with numeric identifier)

- Land use distribution - Population, including present & future growth

trends

- Wildlife resources - Recreational uses, if relevant - Pollutant of concern and, if applicable,

justification for using surrogate measures

- Description of pollutant sources (PS and NPS; also, describe natural background, if distinguishable from NPS)

Description of Applicable Water Quality Standards and Numeric Water Quality Target

- Water quality standard (numeric or narrative) - Designated use - Description of impairment (extent, magnitude,

etc.)

Pollutant sources (PS and NPS; also, describe natural background, if distinguishable from NPS)

Loading capacity of each listed waterbody - Description of methodology used - If both acute and chronic standards exist, as

with fecal coliform, and are exceeded then must explain how both are addressed in TMDL

- Critical conditions (e.g., low flow) accounted for, if applicable

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Load allocation attributed to existing and future NPS, including description of methodology used

Wasteload allocations for each NPDES permitted source and straight pipe septics (loading of 0 for these septics)

Margin of Safety and justification

Reserve Capacity description (if not included in TMDL needs discussion of why not)

Reasonable Assurance that TMDL will be achieved (describe regulatory and nonregulatory efforts at state and local levels; funding possibilities)

Seasonal Variation

Monitoring plan to track TMDL effectiveness

Implementation Strategy providing general approach, but not a formal implementation plan. This should include broad cost ranges for implementation, per the 2006 Clean Water Legacy Act

Public Participation summary, including public notice process to be used

Is technical discussion throughout transparent and defensible in court (BPJ is justified at all points) balanced with “is this a reasonable approach”?

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Appendix B:

Guidance for Communities on How to Integrate Lower Minnesota River Dissolved Oxygen TMDL Requirements and MS4 Stormwater Pollution

Prevention Programs

Introduction

Overview The Lower Minnesota River is impaired by low dissolved oxygen concentrations during periods of low flow. The low oxygen concentrations result from elevated phosphorus concentrations. To reach acceptable water quality in the river during periods of low flow, a Total Maximum Daily Load (TMDL) was completed. The TMDL requires MS4 communities to reduce phosphorus loading from stormwater runoff by 30 percent. The MS4 stormwater general permit requires permittees to develop and implement Stormwater Pollution Prevention Programs (SWPPPs) and to meet requirements of a TMDL. The SWPPP is therefore the tool for identifying how requirements of a TMDL will be met. The following guidance outlines steps needed by permittees to amend their SWPPPs and comply with requirements of the TMDL. The following guidance for TMDL-affected communities does not supersede requirements of the stormwater general permit, but includes recommendations for inclusion into the SWPPP. General Approach The TMDL reduction will be met by implementing Best Management Practices (BMPs) rather than meeting effluent limits. For example, if a BMP reduces phosphorus loading by 30 percent and that BMP is implemented across an entire community, the 30 percent reduction would be met. This is discussed in detail in this document. Permittees should begin implementing BMPs as opportunities arise during the first permit cycle. The first permit cycle is also used to identify and establish resources and mechanisms necessary to implement BMPs. During the subsequent three permitting cycles, progress on BMP implementation and effectiveness of BMPs will be monitored to determine if the water quality objectives for the Minnesota River are being met. All BMPs necessary to achieve the water quality goal for the river must be in place by 2025. The phosphorus reduction is based on 2000 land use and assumes no BMPs were in place at that time. Consequently, changes in land use since 2000, future growth, and BMPs currently in place will be

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accounted for in calculating load adjustments. These concepts are illustrated in an example at the end of this document. During the remainder of 2006, MPCA will meet with MS4 communities to work out details of this guidance. MPCA will first conduct a pilot study to test this guidance with one MS4 community, make modifications as necessary, then meet with the remaining MS4 communities. Information gained from discussions between MPCA and MS4 communities will be used to complete SWPPPs in February 2007. Depending on available expertise and resources, development of SWPPPs and incorporation of this guidance may require involvement of consultants. During the first permit cycle, MPCA will continue collecting information useful for selecting and implementing BMPs during the final three permit cycles.

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Guidance

Mapping and calculating load adjustments 1. This section provides information about mapping discharges, conveyance systems, stormwater

watersheds, and existing BMPs. Identification and mapping of discharges is necessary to select and implement BMPs that will meet the TMDL requirements. Mapping existing BMPs is necessary to determine what reductions, if any, have already occurred. The following information should be compiled in an appropriate electronic database and used to create GIS coverages. The example should help illustrate some of the following items.

1.1. The stormwater general permit requires identification of outfalls, conveyances 24 inches or

greater in diameter, DNR subwatersheds (see http://gisdmnspl.cr.usgs.gov/watershed/index.htm), wetlands, and structural pollution control devices. To meet the conditions of a TMDL, greater detail will be required. The greater the detail that can be achieved in mapping discharges, the greater will be the flexibility in implementing BMPs to meet the reduction requirement. We thus recommend identifying and mapping discharge points, watersheds contributing to discharge points, and within each watershed, mapping the conveyance system. The conveyance system includes all below ground (e.g. pipes) and above ground (e.g. curb and gutter systems, ditches) conveyances. Examples of mapped systems can be provided.

1.2. Identify and map factors useful in identifying potential phosphorus contributions. These

include percent impervious surface (using Landsat imagery), land use (e.g. commercial, residential, industrial, park), and soil type (sand, clay). The greater the detail that can be achieved in mapping these, the greater will be the flexibility in implementing BMPs to meet the reduction requirement.

1.3. Identify and map your current and year 2000 urban footprint. Aerial photos and satellite

imagery will be useful for identifying the 2000 footprint. To the extent practical, identify and map future land use. The following link identifies projected population growth over the next 20 years and may be useful in identifying future expansion of your community (http://www.demography.state.mn.us/a2z.html#Population%20forecasting). The calculated load will need to be adjusted to account for differences between current and future land use compared to the 2000 footprint. In a situation where the current or future urban footprint is greater than the 2000 footprint, the required phosphorus reduction will be more than 30 percent. These scenarios and calculations are illustrated in the example at the end of this document.

1.4. The stormwater general permit requires identification of BMPs as they relate to the six

minimum control measures. We recommend mapping existing BMPs and calculating phosphorus reductions associated with these BMPs. These include structural (e.g. infiltration ponds, biofiltration systems, etc.) and non-structural (e.g. street sweeping) BMPs.

1.4.1. Identify and map the BMPs and map watershed areas contributing to the BMPs. 1.4.2. Estimate reductions associated with the BMPs. For example, in the Minnesota

Stormwater Manual (Table 7.4) average total phosphorus removal from vegetation

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filtration is given as 65%, while a value of 50% is given for wet ponds. The Minnesota Stormwater Manual contains some of this information, but MPCA is compiling additional data on efficiencies of BMPs for reducing phosphorus loading from stormwater.

1.4.3. Calculate reductions associated with the existing BMPs. For example, if 10% (0.1) of stormwater from an MS4 is treated using wet ponds, and an average value of 50% (0.5) phosphorus removal is given to wet ponds, then wet ponds have achieved a 5% (0.1*0.50) overall reduction in phosphorus loading.

1.4.4. Note that in the case of BMP sequencing, reductions are not additive. For example, two BMPs in one area that work in series and each achieve a 50 percent phosphorus reduction do not provide a 100 percent phosphorus reduction.

Identifying tools to implement BMPs 2. This section provides methods to 1) identify tools and resources that exist for selecting and

implementing BMPs, 2) list BMP options, and 3) identify future resources needed to achieve reductions through implementation of BMPs.

2.1. List city entities that have functions or requirements associated with stormwater management.

Identify all city operations and determine their relationship to general municipal operations and stormwater management. For example, the City of New Ulm has three departments that may interact on stormwater issues – Administration, which works with finance and community development; Engineering and Inspections, which works with permits, zoning and community development; and Public Works, which works with street and sewer maintenance.

2.2. List other agencies that have functions or requirements associated with stormwater

management. For example, the City of Eden Prairie, in its SWPPP, identifies the Metropolitan Council, MPCA, Hennepin Conservation District, and two watershed districts as entities that have regulatory and non-regulatory responsibilities related to stormwater.

2.3. List existing water resource planning tools. Examples include drainage plan updates, wetland

protection and management plans, local water management plans, and wellhead protection plans.

2.4. The stormwater general permit requires mapping of impervious surfaces for conditions

outlined in Appendix C of the general permit (Limitations of Coverage). These include waters with prohibited or restricted discharge, wetlands, trout waters, historic or archeological sites, threatened or endangered species or associated habitat, and source water protection areas. To meet the conditions of the TMDL, we recommend developing GIS coverages for all waters associated with Limitations of Coverage.

2.5. Identify and list other TMDLs that may affect your community. For example, a Lake Pepin

TMDL may affect communities within the Minnesota River watershed. MPCA’s 2006 list of impaired waters and the current TMDL list will be of value in identifying these water bodies. A GIS-based viewer on MPCA’s website can also be used to identify impaired waters (http://www.pca.state.mn.us/data/edaWater/index.cfm). The purpose of identifying other TMDLs is to identify as early as possible the most restrictive TMDL. For example, the Lower

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Minnesota River Dissolved Oxygen TMDL calls for a 30 percent phosphorus reduction. For purposes of this exercise assume the Lake Pepin TMDL, which will be completed in 2009, calls for a 25 percent reduction. Under this scenario, the Dissolved Oxygen TMDL’s phosphorus reduction would be adequate because it has a more restrictive requirement. MPCA understands this is a complicated issue, since it may be difficult to identify or predict future TMDLs. The Minnesota Pollution Control Agency is preparing a list of TMDLs that apply to MS4s and this list can be used to identify TMDLs that potentially affect a community. There are also difficulties in comparing TMDLs that are based on different physical conditions. For example, the Lower Minnesota River Dissolved Oxygen TMDL applies to low flow conditions in the Minnesota River, while the Lake Pepin TMDL is likely to be a year round TMDL. These are issues the MPCA will continue to work through.

2.6. Develop a menu or matrix from which to select BMPs for implementation. For each BMP in

this menu, include the information described below. The Minnesota Stormwater manual provides information useful for completing this menu. MPCA will continue to gather additional information useful to you in completing the menu.

2.6.1. Effectiveness for reducing phosphorus. For example, the Minnesota Stormwater Manual indicates wet ponds, on average, have a phosphorus removal efficiency of 50 percent.

2.6.2. Time to achieve effectiveness, maturity rate and expected life expectancy. 2.6.3. Maintenance requirements. Maintenance includes both structural and non-structural

maintenance, and training. An example of structural maintenance is ensuring that an infiltration pond is functioning properly. An example of non-structural maintenance is maintaining a schedule for street sweeping. An example of maintenance for training is ensuring there is on-going training and certification for developers and engineers.

2.6.4. Costs associated with each BMP. These include construction and maintenance costs. Consider both monetary and non-monetary costs. An example of a non-monetary cost is a stormwater pond that could be a drowning hazard or provide mosquito breeding habitat.

2.7. Develop a list of water quality modeling options. Water quality models are used to simulate

phosphorus loading reduction associated with different BMP implementation strategies. Models can be used to develop a scenario that achieves the 30 percent reduction. For example, models can be used to identify locations where BMPs will help achieve the greatest reductions. The Minnesota Stormwater Manual provides a list of water quality models. In general, more accurate mapping of stormwater conveyances and watersheds allows employment of simpler water quality modeling.

2.8. Determine if low impact development (LID) is an option in new developments and in

redevelopment. MPCA is conducting studies with communities to investigate ways in which to incorporate LID into new developments.

2.9. Describe legal tools that can be used or will be needed to implement BMPs. These include

ordinances, building codes, easements, and ownerships. Determine what changes can be made in legal authorities, including development of new ordinances or changes to existing ordinances. Determine the relationship between individual BMPs from the BMP menu and regulatory or non-regulatory requirements. Adopt or establish the framework and schedule needed for new legal authorities.

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2.10. Describe the plat review process. State whether the city has control or a voice in the planning

of land developments. Identify the relationships between different entities involved in the plat review process and the communication tools that exist between these different entities. Determine if changes to the plat review and building permit process, including inspections, will be needed to implement BMPs identified in the BMP menu. Determine if appropriate authority exists to modify the existing plat review process. Modify or establish the framework for modifying the plat review process.

2.11. Describe existing funding mechanisms that can be used or will be needed to implement and

maintain BMPs. These include fees, taxes, escrows, capital improvement projects, and trusts. Examples include stormwater utility fees assessed against monthly utility bills or, conversely, incentives to homeowners to reduce utility fees by implementing BMPs such as rain barrels or rain gardens. Identify mechanisms for increasing funding and capital improvement project scheduling. Determine if there is a relationship between individual BMPs from the BMP menu and funding mechanisms. Implement or establish the framework for implementing needed funding mechanisms.

2.12. Establish a schedule for monitoring, operating, and maintaining BMPs. Permittees will be

responsible for monitoring progress in implementing BMPs to meet the TMDL requirement and in maintaining BMPs that have been implemented. The MPCA and University of Minnesota are currently developing guidance that establishes four levels of monitoring. This guidance will be useful to communities in deciding appropriate levels of monitoring for BMPs. Monitoring requirements may be included in the BMP menu. For BMPs in place, implement the monitoring, operation, and maintenance schedule. The Minnesota Stormwater manual contains information on maintenance requirements for different BMPs.

2.13. Inventory current and future technical tools and expertise necessary to accomplish the

conditions of this SWPPP and subsequent SWPPPs. For example, will training be required of existing city staff or will database, GIS, or modeling expertise be required either from consultants or from MPCA staff? As funding allows, secure technical resources needed for BMP selection and implementation. It may be necessary to hire consultants early in this process to select appropriate models and address data management and GIS issues.

2.14. Determine if there are BMPs that can be implemented immediately. This may require

completion of the BMP menu so that appropriate BMPs can be selected. MPCA benchmarking studies will be of value in identifying generic BMPs that can be employed for phosphorus reduction.

Actions for First Permit Cycle 3. This section describes actions that can be taken during the first permit cycle to begin achieving

reductions. It will be important to link these actions with many of the actions in Section 2. For example, it may be prudent to develop an ordinance requiring incorporation of BMPs in new or re-development projects.

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3.1. Implement nonstructural BMPs, such as street sweeping, storm drain maintenance, storm drain

stenciling, lawn care education, and mowing reductions. 3.2. Incorporate Better Site Design and Low Impact Development into all redevelopment and new

development projects. 3.3. Develop a Communication Plan to inform the community and stakeholders about the TMDL

and the process for meeting requirements of the TMDL.

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Timelines

The following timelines are intended to get appropriate BMPs into place during the first permit cycle, but also acknowledge that additional cycles will be required to identify resources and establish the infrastructure necessary to meet the TMDL requirement. In the table below, shaded boxes indicate when an activity should begin and end, rather than a range of times over which an activity may be started. MPCA will work with MS4 communities during 2006 to finalize this guidance. SWPPPs are due for submittal in February of 2007. The MS4 permit requires that an annual report be submitted by June 30th of each year describing progress toward completion of conditions in the SWPPP. The timelines in the following table are shorter than those for MS4s that have previously submitted SWPPPs. This is due to requirements of the TMDL and because the communities affected by this guidance are generally considerably smaller than other MS4s that have submitted SWPPPs. The methods for addressing TMDL requirements presented in this guidance are in approximate chronological order. Most recommendations described in this guidance can be initiated in 2007, with maps, an inventory of existing resources, and identification of future needs completed by June of 2008. Completion of a BMP menu, establishing new funding, regulatory, and plat review processes, and securing technical resources will in general take longer to complete.

Description 2006 – Feb.-07 2007 2008

2009-2010

Cycle 2

Cycles 3 and 4

Finalize guidance and submit SWPPP Identify and map discharge points, watersheds

contributing to discharge points, and within each watershed, map the conveyance system

Identify and map factors useful in identifying potential phosphorus contributions

Identify and map current and 2000 urban footprint Calculate loading corrections for differences

between current and future land use compared to the 2000 footprint

Identify and map the BMPs and map watershed areas contributing to the BMPs

Estimate reductions associated with the BMPs Calculate reductions from existing BMPs

List city entities that have stormwater management functions or requirements

List other agencies that have stormwater management functions or requirements

List existing water resource planning tools Develop GIS coverages for all waters associated

with Limitations of Coverage

List other TMDLs that may affect your community Develop a menu from which to select BMPs for implementation in subsequent permitting cycles

Develop a list of water quality modeling options

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Determine if low impact development (LID) is an option in new developments and in redevelopment.

Describe legal tools that can be used to implement BMPs

Develop a framework needed to establish legal tools needed for implementing BMPs

Describe the plat review process Modify or establish a framework needed for

modifying the plat review process as needed for implementing BMPs

Describe existing funding mechanisms that can be used to implement and maintain BMPs

Develop or establish a framework needed to secure funding needed for implementing BMPs

Establish a schedule for monitoring, operating, and maintaining BMPs

Inventory current and future technical tools and expertise necessary to accomplish the conditions of

this SWPPP and subsequent SWPPPs

Secure or establish framework for securing technical tools needed to select and implement

BMPs

Implement BMPs Maintain BMPs Monitor BMPs

Modify legal, funding, plat review, or technical processes and resources as needed to implement

BMPs

Implement non-structural BMPS during first permit cycle

Incorporate Better Site Design/LID into new and re-development projects during first permit cycle

Develop Communication Plan to inform community and stakeholders about the TMDL and

process for meeting TMDL requirements

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Example

This example for an imaginary City A illustrates some tasks targeted for the first permit cycle. a. The following figure shows locations of discharge points, watershed areas, and conveyance

systems.

b. The following figure shows percent impervious surface and land use.

Minnesota River

Residential, 40-60% impervious (6000 acres)

Industrial, 40-60% impervious (1000 acres)

Commercial, 40-60% impervious (2000 acres)

Green space, 0-10% impervious (1000 acres)

c. The following figure shows 2000 and projected land use. Projected growth is 10 percent (1000

acres). To adjust for this increased growth, the required load reduction must be recalculated and equals 1-(0.7/(1.0 + 0.1)), or about 36 percent.

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Minnesota River

2000 footprint (10000 acres) Projected growth (11000 acres)

d. The following figure shows locations of existing BMPs, acreages they serve, and other water resources within the city. If we assume a wet pond reduces phosphorus loading by 50 percent and bioretention by 60 percent, then we have already achieved a 16 percent reduction in phosphorus loading (0.5*2000/10000)+(0.6*1000/10000).

Minnesota River

Wet stormwater ponds (servicing 2000 acres)

Infiltration Bioretention (servicing 1000 acres)

e. BMPs in sequence (series) do not result in additive reductions. For example, assume we implement street sweeping and that results in a 10 percent load reduction. In the area where we have wet ponds, the reduction is not 60% (10% + 50%), but instead will be less than 60% because the 50 percent reduction from wet ponds applies to the phosphorus remaining after the 10 percent reduction from street sweeping. There are some difficulties in calculating

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effectiveness of BMPs in sequence. For example, two BMPs in series may both be effective at removing phosphorus associated with sediment but not soluble phosphorus.