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  • Operation, Maintenance,and Management

    of Stormwater Management Systems

    Produced by the:

    Watershed Management Institute, Inc."Creating Practical Solutions for Complex Resource Challenges"

    in cooperation with

    Office of WaterU. S. Environmental Protection Agency

    Washington D.C.

    August 1997

  • This handbook was produced by the Watershed Management Institute in cooperationwith the United States Environmental Protection Agency, Office of Water, through

    Cooperative Agreement CX823621-01-0. The contents do not necessarily reflect theviews or policies of the Environmental Protection Agency, nor does mention of tradenames or commercial products constitute endorsement or recommendation for use.

    Produced by the Watershed Management Institute, Inc.

    Principal Authors: Eric H. LivingstonEarl ShaverJoseph J. Skupien, P. E.

    Contributing Author: Richard R. Horner, Ph. D.

    Watershed Management InstituteP.O. Box 14

    Ingleside, Maryland 21644Phone: 410/758-2731

    Fax: 410/758-0386

    Watershed Management Institute410 White Oak Drive

    Crawfordville, Florida 32327Phone: 850/926-5310

    Fax: 850/926-1534

    Printed on recycled paper


    The preparation of this document was made possible through a Cooperative Agreement withthe U. S. Environmental Protection Agency (Assistance ID No. CX823621-01-0).

    We would like to thank several individuals whose support and participation were essential to thecompletion of this handbook on the operation, maintenance, and management of stormwatermanagement systems. In particular, we want to extend our appreciation to Mr. Rod Frederick ofthe U. S. EPA for his support of this project, and especially to Mr. Robert Goo, our EPA ProjectOfficer, for his support and guidance in the preparation of this document. We also want to thankthe reviewers of the draft handbook who provided valuable comments which greatly improvedthe final document. Reviewers included:

    Robert Goo, U.S. EPA, Washington D. C.Rod Frederick, U.S. EPA, Washington D. C.Dov Weitman, U.S. EPA, Washington D. C.Bill Swietlik, U.S. EPA, Washington D. C.Tom Davenport, U. S. EPA, Region 5, ChicagoRick Watson, Bellevue (WA) Utilities DepartmentBill Chamberlin, Orlando (FL) Stormwater UtilityDan DeWiest, Florida Department of Environmental Protection

    We also want to thank the people who took time out from their busy schedule to respond to ourtelephone and mail requests, especially for information on the cost of operating, maintaining,and managing stormwater management systems. These individuals include Doug Harrison(Fresno Flood Control District), Paul Hoffman (Austin Public Works and Transportation Depart-ment), Scott Tucker and Mark Hunter (Urban Drainage and Flood Control District), Rick Watson(Bellevue Utilities Department), and Bill Chamberlin (Orlando Stormwater Utility).

    We also want to acknowledge and thank the following:

    The Delaware Department of Natural Resources and Environmental Control for allowingthe use of stormwater management system slides taken in Delaware.

    The Florida Department of Environmental Protection for many of the slides taken in Florida.

    Slides taken in Maryland were part of a personal collection, but were taken by a numberof individuals employed by the Maryland Department of the Environment.

    Other slides were taken by the authors in numerous locations around the country andinternationally.

    Finally, we want to acknowledge the 1989 Stormwater Management Facilities MaintenanceManual published by the New Jersey Department of Environmental Protection as one of theearliest efforts to address stormwater management facility maintenance in a coordinated andcomprehensive fashion. Many of the Manual's topics, definitions, recommendations, and evenmuch of its format, have been adapted for use in this handbook.

  • Operation, Maintenance, and Management of Stormwater Systems


    CHAPTER 1: INTRODUCTION1. Why Is Stormwater System Operation, 1-1

    Maintenance and Management Important2. Chapter Contents 1-23. Handbook BMP Terminology 1-4

    3.1 Detention Practices 1-43.2 Infiltration (retention) Practices 1-53.3 Filtration Practices 1-53.4 Biofiltration Practices 1-6


    1.1 Intended Readers 2-12. Stormwater Management Program Considerations 2-1

    2.1 Stormwater Program Components 2-12.2 Stormwater Program Evolution (Retrofitting) 2-22.3 Stormwater BMPs and New Development 2-6

    3. Stormwater Pollutants and Reduction Mechanisms 2-104. Stormwater Management Practices (BMPs) 2-13

    4.1 BMP Selection 2-154.2 BMP Fact Sheets 2-16

    Infiltration Practices 2-17Infiltration Basins 2-23Infiltration Trenches 2-26Exfiltration Trenches 2-30Pervious Pavement 2-32Modular Pavement 2-38Detention Practices 2-41Dry Detention Basins 2-42Extended Dry Detention Basins 2-45Wet Detention Ponds 2-48Biofiltration Practices 2-54Constructed Wetlands 2-59Stormwater Filters 2-65


    1.1 Objectives 3-11.2 Intended Readers 3-2

    2. Stormwater Management Practices and Components 3-22.1 Detention 3-22.2 Infiltration 3-3


  • Operation, Maintenance, and Management of Stormwater Systems


    Contents2.3 Filtration 3-32.4 Biofiltration 3-3

    3. The Responsibilities of the Facility Designer 3-34. BMP Design Considerations: Points to Ponder 3-7

    4.1 Interested Parties 3-84.2 Operating Conditions 3-104.3 Design Methodologies 3-124.4 Facility Type 3-12

    5. BMP Design Considerations: A Checklist 3-135.1 Safety 3-135.2 Performance 3-145.3 Constructability 3-145.4 Maintenance 3-155.5 Cost 3-165.6 Community Acceptance 3-16

    6. Specific Maintenance Considerations 3-176.1 Maintainability 3-176.2 Accessibility 3-176.3 Durability 3-18

    7. Suggested Design Review Techniques 3-187.1 Spend a Mental Year at the Facility 3-187.2 Who, What, When, Where, and How 3-19

    8. Design Guidelines 3-209. Summary 3-2010. Design Guidelines for Detention Practices 3-21

    10.1 Introduction 3-2110.2 Bottoms 3-2110.3 Dams, Embankments, and Side Slopes 3-2410.4 Principal Outlets 3-2510.5 Outflow System 3-2710.6 Inlets 3-2710.7 Emergency Outlets 3-2810.8 Low Flow Measures 3-2910.9 Vegetative Cover 3-3010.10Trash Racks 3-3110.11Access 3-3210.12Perimeters 3-34

    11. Design Guidelines for Infiltration Practices 3-3511.1 Introduction 3-3511.2 Bottoms 3-3511.3 Dams, Embankments, and Side Slopes 3-3811.4 Inlets 3-3811.5 Emergency Outlets 3-39

  • Operation, Maintenance, and Management of Stormwater Systems


    11.6 Vegetative Cover 3-4011.7 Access 3-4111.8 Perimeters 3-42

    12. Design Guidelines for Filtration and Biofiltration Practices 3-4312.1 Introduction 3-4312.2 Bottoms 3-4312.3 Dams, Embankments, and Side Slopes 3-4512.4 Principal Outlets 3-4612.5 Outflow Systems 3-4712.6 Inlets 3-4812.7 Emergency Outlets 3-4912.8 Vegetative Cover 3-4912.9 Trash Racks 3-5012.10Access 3-5112.11Perimeters 3-53

    Appendix 3-1 Drawings of Typical Details of Some Important 3-54Stormwater System ComponentsFigure 3A Detention Basin Orifice and Weir Plates 3-55Figure 3B Detention Basin Trash Rack 3-56Figure 3C Infiltration System Underdrain 3-57Figure 3D Nonvegetated Infiltration Basin Bottom 3-58


    1.1 Intended Readers 4-22. Roles of Government 4-23. Federal Stormwater Programs 4-34. State Stormwater Management Programs 4-3

    4.1 Program Guidance and Requirements 4-44.2 Stormwater Legislation 4-54.3 Stormwater Regulations 4-94.4 Example Language for State/Local Stormwater Rules 4-11

    5. Local Stormwater Management Programs 4-116. Recommendations on Public vs. Private Maintenance 4-137. Examples of Maintenance Agreements 4-14

    Appendix 4-1 Example Language That Should Be Contained 4-16in State, Regional, or Local Stormwater Rules

    Appendix 4-2 Olympia, Wa. Residential Agreement to Maintain 4-31a Stormwater Management Facility


  • Operation, Maintenance, and Management of Stormwater Systems


    Appendix 4-3 Olympia, Wa. Commercial/Industrial Agreement 4-35to Maintain a Stormwater Management Facility

    Appendix 4-4 Alexandria, Va. Standard BMP Maintenance and 4-39Monitoring Agreement

    Appendix 4-5 Recommended Maintenance of Stormwater 4-44Management Systems Included In FloridaNPDES Municipal Stormwater Permits


    1.1 Objectives 5-11.2 Intended Readers 5-2

    2. The Meaning of Stormwater Facility Ownership 5-22.1 Basic Stormwater Management Facility Operation 5-32.2 Stormwater Management Practices 5-42.3 Stormwater Facility Components 5-52.4 Operational Impacts of Facility Maintenance 5-52.5 Impacts of Facility Maintenance Neglect 5-7

    3. Types of Facility Owners 5-94. Maintenance Program Development 5-10

    4.1 Designate a Responsible Individual 5-104.2 Plan for Maintenance 5-114.3 Identify Costs and Allocate Resources 5-134.4 Create a Written Plan 5-144.5 Conduct Periodic Program Reviews 5-15


    1.1 Intended Readers 6-22. Stormwater System Construction Impacts & Mitigation 6-3

    2.1 Economic Impacts of Sedimentation 6-32.2 Environmental Impacts of Pollutant Discharge 6-4

    3. Legal Authority for Inspection 6-54. Preconstruction Activities 6-6

    4.1 Review of Approved Stormwater Plan 6-64.2 Preconstruction Site Meeting 6-7

    5. Inspection Responsibilities During Construction 6-75.1 Routine Inspection Responsibilities 6-75.2 Progress Meetings 6-85.3 Final Inspections 6-9

    6. Inspection Procedures 6-96.1 Have Necessary Inspection Equipment 6-10


  • Operation, Maintenance, and Management of Stormwater Systems


    6.2 Check In at the Construction Trailer 6-106.3 Always Complete an Inspection Form 6-106.4 Walk the Site in a Consistent Manner 6-106.5 Wear Safety Equipment 6-11

    7. Inspector Attitudes and Training 6-118. Individual BMP Inspection Considerations 6-13

    8.1 Detention/Retention Systems 6-138.2 Constructed Wetlands 6-168.3 Infiltration Practices 6-208.4 Filtration Systems 6-318.5 Biofiltration Systems 6-34

    9. Once Construction is Complete 6-3710. Recommendations for Inspector Training and 6-38

    Certification Programs

    Appendices - Construction Inspection Forms 6-396-1 Preconstruction Inspection Meeting Topics 6-406-2 General Site Inspection and Notice to Comply 6-436-3 Sediment/Stormwater Basin Construction Checklist 6-466-4 Sediment/Stormwater Pond Typical Sequence of 6-51

    Construction6-5 Construction Checklist for Infiltration Practices: 6-556-5A Basins 6-566-5B Trenches 6-576-5C Dry Wells 6-586-5D Pervious Paving 6-596-5E Swales 6-606-6 Construction Checklist for Filtration Practices 6-616-7 Construction Checklist for Biofiltration Practices 6-63


    1.1 Intended Readers 7-22. How Maintenance Can Reduce Downstream Impacts 7-2

    2.1 Increased Discharge of Pollutants Downstream 7-22.2 Increased Risk of Downstream Flooding 7-32.3 Increased Downstream Channel Instability 7-32.4 Potential Loss of Life and Property 7-42.5 Aesthetic or Nuisance Problems 7-4

    3. Importance of Checklists 7-53.1 Checklist for Inspectors 7-53.2 Checklist to Evaluate Stormwater System Function 7-5


  • Operation, Maintenance, and Management of Stormwater Systems



    4. Highlighted Expected Operation, Maintenance, and 7-6Management Needs as a Function of Components

    4.1 Detention/Retention Ponds 7-64.2 Infiltration Facilities 7-9

    4.3 Filtration Facilities 7-104.4 Biofiltration Facilities 7-11

    5. Inspection Frequency 7-126. Aesthetic and Functional Maintenance 7-13

    6.1 Aesthetic Maintenance 7-136.2 Functional Maintenance 7-14

    7. Training Needs 7-187.1 Mandatory vs. Voluntary Training 7-197.2 Components of an Inspector Training Program 7-197.3 Components of an Operator Training Program 7-20

    8. Equipment and Resources Needed 7-219. Typical OMM Tools 7-2110. Importance of Tracking OMM 7-2311. Prioritizing Maintenance Tasks 7-2312. Safety Issues 7-24

    12.1 Safety During Maintenance Inspections 7-2412.1 Safety During Actual Maintenance 7-26

    13. Specific Maintenance Activity for Each Type of Facility 7-2613.1 Detention/Retention Ponds 7-2713.2 Infiltration Practices 7-3113.3 Filtration Practices 7-3513.4 Biofiltration Systems 7-39

    14. General Discussion 7-41

    Appendices - Operation, Maintenance, and Management Checklists7-1 OMM Inspection Checklist for Ponds 7-437-2A OMM Inspection Checklist for Infiltration Basins 7-487-2B OMM Inspection Checklist for Infiltration Trenches 7-507-2C OMM Inspection Checklist for Dry Wells 7-527-2D OMM Inspection Checklist for Pervious Pavement 7-537-2E OMM Inspection Checklist for Swales 7-547-3 OMM Inspection Checklist for Filtration Facilities 7-557-4 OMM Inspection Checklist for Biofiltration Practices 7-58


    1. Overview 8-11.1 Intended Readers 8-1

  • Operation, Maintenance, and Management of Stormwater Systems



    2. Stormwater System Maintenance Costs 8-13. OMM Costs from Specific Stormwater Programs 8-2

    3.1 Orlando, Florida 8-63.2 Fresno, California 8-63.3 Somerset County, New Jersey 8-63.4 Austin, Texas 8-93.5 Denver, Colorado 8-93.6 Bellevue, Washington 8-163.7 Kitsap County, Washington 8-18

    4. Financing Stormwater System OMM 8-194.1 Public Financing of Stormwater OMM 8-20


    1.1 Intended Readers 9-12. Potentially Applicable Laws and Regulations 9-1

    2.1 Federal Laws and Regulations 9-22.2 State Laws and Regulations 9-3

    3. Characteristics of Stormwater Sediments and Wastes 9-63.1 Contaminant Levels in Ultra-Urban BMP Sediments 9-13

    4. Recommendations on Sediment Testing 9-144.1 Storm Facility Solids and Liquid Wastes 9-144.2 Sand Filter Medium and Accumulated Sediments 9-15

    5. Recommendations on Disposal of Stormwater Sediments 9-155.1 Waste Collection Considerations 9-155.2 Disposal Methods 9-155.3 Decant Water Disposal 9-165.4 Sand Filter Waste Disposal Methods 9-17



    Over the last two decades, stormwater man-agement systems have evolved considerablyfrom their traditional roles as conveyance de-vices that are only intended to transport storm-water runoff safely and efficiently from one lo-cation to another. Such conveyance systemshave included bridges, culverts, ditches, andthe ubiquitous piped storm drain (sewer).However, in response to growing concernsover nonpoint source (NPS) pollution, flood-ing, and erosion, a new type of stormwatersystem has been created. This type not onlyconveys runoff, but also manages it by delib-erately modifying its flow rate, volume, and/orwater quality. These stormwater managementsystems rely upon practices such as infiltra-tion or retention areas, extended dry or wetdetention, sand filters, vegetated swales, andconstructed wetlands.

    Whether designed for conveyance or man-agement, all stormwater systems requireproper design, construction, and mainte-nance to perform successfully. However,due to their more demanding duties and ob-jectives, today's multipurpose stormwaterpractices have proven themselves to be in-herently more complex than their more tradi-tional conveyance counterparts. Accordingly,they require a much greater level of effort bythose who design, construct, maintain, andoperate them.

    This is particularly true for stormwater man-agement system maintenance and manage-ment. Maintenance has always been recog-nized as vital to the proper and prolonged per-

    formance of all stormwater systems. How-ever, thorough and consistent maintenanceis particularly crucial to the successful per-formance of stormwater treatment prac-tices, an importance that carries over to theentire stormwater management program theysupport. Reasons for this increased impor-tance include:

    As noted above, stormwater managementsystems are inherently more complex thantraditional runoff conveyances. Not only intheir function or operation, but also in thenumber and types of materials used to con-struct them. This may even include naturalmaterials such as aquatic vegetation andmicroorganisms. This increased complex-ity and variety demands a greater level ofmaintenance and management to assuresafe and effective operation.

    Unlike drainage systems, many stormwaterpractices achieve their management goalsthrough impoundment or storage of runoffinstead of conveyance. This is accom-plished through the use of dams, berms,tanks, or chambers. To successfully im-pound water, either temporarily (for ex-ample, in a dry detention or infiltration ba-sin) or permanently (in a wet detention pondor constructed wetland), requires a greaterdegree of structural strength. Safely im-pounding stormwater requires more safe-guards to avoid the possibly catastrophicdownstream damage caused by structuralfailure and sudden release of the im-pounded water. These increased levels ofstrength and safety, which must be providedcontinually throughout the life of thestormwater management facility, demanda similarly higher level of maintenance.


    Chapter 1Introduction

  • Operation, Maintenance, and Management of Stormwater Systems


    Stormwater conveyances and flood controlsystems typically are designed to transportor impound the runoff from a relatively rarestorm event, with a recurrence interval of25 to 100-years. As such, they may expe-rience maximum design conditions only afew times during their lifetime. However,stormwater management systems, par-ticularly those intended to treat runoff andreduce pollutants, typically are designed tocapture smaller, more frequent rainfall/run-off events (e.g., half inch storm; 2-yr, 1-hrstorm). Therefore, they may experiencemaximum design conditions severaltimes each year. This more frequent andrepetitive operation at their design limit cre-ates more stress, which again demandsgreater attention and commitment to propermaintenance and management.

    Failure to perform adequate mainte-nance of stormwater management sys-tems not only leads to reductions in ex-pected or desired performance levels, butmay even create conditions that areworse than if the facility had not beenconstructed at all. For example, a ne-glected dam may fail and release im-pounded water onto downstream proper-ties, an eroding swale may be the sourceof excessive sediment, or a poorly managedconstructed wetland may create harmfullevels of nutrients or temperature.

    Stormwater management has become an im-portant part of our efforts to achieve cleanwater and a safe environment. However, asseen above, neglect of stormwater manage-ment systems not only poses a threat to thoseliving downstream, but it can also underminethe entire stormwater management programthat led to their creation. The importance ofregular inspection and thorough stormwatersystem maintenance can not be understated.In fact, stormwater systems should noteven be constructed if the stormwaterprogram is not willing to make the neces-

    sary commitments to assure that the sys-tems are properly maintained, managed,and operated.

    The objective of this handbook is to help as-sure that necessary maintenance and man-agement of stormwater systems is performed.The handbook is aimed at a diverse audience- all of those individuals and groups which havebeen shown by both experience and researchto play an important role in a successful storm-water management system maintenanceprogram. This includes persons involved indeveloping and implementing stormwatermanagement programs, stormwater systemdesigners and builders, land developers andtheir consultants, stormwater system plan re-viewers and inspectors, stormwater systemowners and operators, public officials, and allcitizens.


    The handbook is divided into eight additionalchapters, each addressing an important as-pect of stormwater system operation andmaintenance:

    Chapter 2 - Stormwater Management Prac-tices presents an overview of several dif-ferent types of commonly used stormwatermanagement practices. These include infil-tration or retention systems, wet and dry de-tention systems, constructed wetlands, veg-etated swales, and filtration systems such assand filters and biofiltration systems. For eachtype of practice, information is presented onits basic runoff quantity and quality controlmechanisms, pollutant removal potentials, siteand operating limitations, and operation andmaintenance obligations. This presentationof basic information is intended to improvethe understanding of the needs and limi-tations of each practice by those who de-sign, regulate, construct, own, operate, ormaintain them. All of these individuals play

  • CHAPTER 1 Introduction


    a vital role in assuring proper maintenance andoperation of the practice.

    Chapter 3 - Planning and Design Consid-erations is addressed directly tostormwater management system plannersand designers. Information is presentedwhich demonstrates how proper planningand design can help to both minimize andfacilitate system maintenance. The main-tenance problems that can result from inad-equate or inattentive planning or design arealso highlighted. Additionally, planning anddesign guidelines to help achieve minimummaintenance goals are presented for eachtype of stormwater management practice de-scribed in Chapter 2. This informationstresses the importance of simplicity, ac-cessibility, and durability in designingstormwater management systems.

    Chapter 4 - Programmatic and RegulatoryAspects highlights the key role thatprogram implementers play in achievingproper levels of stormwater managementsystem maintenance and how their igno-rance or indifference can lead to mainte-nance neglect and facility failure. Properplanning, design, and construction all contrib-ute to a successful maintenance program.However, the key to success is ensuring thateach of these activities gets done, a role forwhich program implementation staff areuniquely suited. To achieve this goal, imple-mentation staff must become as involvedin the maintenance of stormwater manage-ment systems as they are with the plan-ning, design, and construction. Mainte-nance of stormwater systems can not simplybe left for others to resolve. Guidance forestablishing the proper institutional frame-work and standards is provided, includingessential program aspects such as manda-tory operation and maintenance plans, desig-nating responsible entities, operating permits,enforcement options, and maintenance de-fault contingency plans.

    Chapter 5 - Owner, Operator, and User Con-siderations provides each of these indi-viduals and groups with important infor-mation regarding how their system works,why it is needed, and what maintenance itwill require. It also explains in clear termswhy it is in their best interest to provide thor-ough and consistent levels of system mainte-nance and how maintenance neglect on theirpart can lead to serious environmental, safety,and legal problems. The Chapter also pro-vides suggestions for establishing a success-ful maintenance program and will discuss theenvironmental, financial, aesthetic, and civicrewards for doing so.

    Chapter 6 - Construction Inspection high-lights a vital but often overlooked aspectof successful stormwater managementsystem maintenance. It is the inspectors whomust complete the job started by the adminis-trators, planners, and designers, and whomust provide the owners, operators, andmaintainers with a sound, durable facility thatis worthy of their maintenance investment.The Chapter assists construction inspec-tors by providing detailed checklists ofimportant inspection items during eachstage of construction. It also emphasizesthe importance of system construction sched-uling, phasing, and coordination with other siteactivities and promotes close coordination andcommunication between inspectors, contrac-tors, owners, designers, and reviewers. Fi-nally, recommendations for establishing train-ing and certification programs for inspectorsare also provided, including a model programcurriculum.

    Chapter 7 - Post-Construction Inspectionand Maintenance presents pertinent infor-mation to the final members of the overallmaintenance team - those responsible forinspecting, scheduling, and performing theactual maintenance and management ofstormwater management systems. ThisChapter seeks to address a deficiency in many

  • Operation, Maintenance, and Management of Stormwater Systems


    state and local stormwater management pro-grams. It provides detailed information to bothinspectors and owner/operators and empha-sizes the importance of both groups to the suc-cess of the overall stormwater managementprogram. Inspectors are provided withchecklists detailing a comprehensive sys-tem inspection program, including recom-mended inspection frequencies and a break-down of inspection practices by system com-ponent. Owner/operators are presentedwith descriptions of typical maintenancetasks, including recommended equipment,techniques, materials, and frequencies.Finally, information on developing a trainingand certification program for those who per-form system maintenance is also presented.

    Chapter 8 - Maintenance Costs and Financ-ing discusses an aspect of stormwater man-agement system maintenance that is of inter-est to everyone from administrators to own-ers, and which is vital to the success of anystormwater management program. Summa-ries of expected or typical costs for vari-ous maintenance tasks, both regular andepisodic, are presented. Estimated costsof materials and equipment also are provided.In addition, various means of financing thesecosts are discussed, with examples of vari-ous institutional programs highlighted.

    Chapter 9 - Disposal of Sediments presentsinformation on a new issue of concern thatemphasizes both the complex nature of storm-water management systems and the need fora comprehensive maintenance program.Sedimentation is one of the primary mecha-nisms for pollutant removal in manystormwater management systems. As a re-sult, the sediment collected in the facility maycontain heavy metals, hydrocarbons, greases,nutrients, and other pollutants depending uponthe character and use of the land draining tothe system. Depending upon their concen-trations and quantities, these pollutantsmay pose disposal problems for facility

    owners, operators, and maintainers. Gen-eral recommendations for analyzing and prop-erly disposing of these sediments are pre-sented along with a discussion of potentialregulatory constraints.

    As can be seen from the above review, storm-water management system maintenance is abroad and complex topic. It is hoped that thishandbook attracts an equally broad and di-verse group of readers. To assist readersfind the information they seek quickly, eachchapter in the handbook begins with a briefsummary of its contents, including thegoals of the Chapter and a list of its in-tended readers. This should allow the readerto quickly assess the contents of each Chap-ter and determine its applicability to his or herinterests or needs. To further guide the reader,major topics within each chapter are presentedunder their own descriptive headings.


    The field of stormwater management hasgrown considerably in the past two decades.This growth has produced, among many ac-complishments, a long and sometimes con-flicting list of names for various stormwatermanagement practices. Unfortunately, thesenames can vary by state or region. This canconfuse or mislead the experienced practitio-ner, not to mention the new reader. There-fore, in order to minimize such confusion andmaximize the handbooks effectiveness, thefollowing general definitions have beenadopted for use in the handbook:

    3.1. Detention Practice:A stormwater management practice whichtemporarily impounds runoff and dischargesit through an outlet structure. Any additionaloutflow through infiltration or evaporation isnegligible and, therefore, not ordinarily con-

  • CHAPTER 1 Introduction


    and chemical and biological processes to oc-cur, reducing stormwater pollutants. Duringand immediately after storms, runoff is tem-porarily stored above the permanent waterpool.

    3.2. Infiltration (Retention) Practices:A stormwater management practice whichtemporarily impounds a specified amount ofrunoff (treatment volume), retains it on-site,and discharges it through percolation into theunderlying soil and by evapotranspiration. On-line practices typically will have outlet struc-tures to safely convey the flood control vol-ume, and emergency overflows from extremestorm events. Infiltration practices are ex-pected to be dry during non-rainfall periods.The retention practice tool box includes infil-tration basins and trenches, swales, perviouspavements, dry wells, and seepage pits.

    3.3 Filtration Practices:A stormwater management system which fil-ters the runoff through a medium to removepollutants, especially particulate pollutants.

    sidered in the facilitys design. Detention prac-tices may be either wet or dry. They oftenare divided into three categories:

    A. Dry detention practices which detain run-off for a relatively short time (1 to 24 hours)and release it at a controlled rate until the sys-tem is once again dry.

    B. Extended dry detention practices whichdetain runoff for a longer time (24 to 48 hours),thereby increasing sedimentation and pollut-ant removal before the runoff is released at acontrolled rate and the system is once againdry.

    Extended Dry Detention System

    C. Wet detention practices, or wet ponds,which have a permanent pool of water, detainand release runoff over five days or evenlonger, and allow sedimentation, flocculation,

    Wet Detention System (Pond)

    Infiltration Trench

  • Operation, Maintenance, and Management of Stormwater Systems


    Sand Filtration Facility

    Filter systems usually are used in combina-tion with detention systems. Filter media in-clude mixtures of sand, peat, and compost.Filters can be either confined (in boxes, bags,etc.) or unconfined. They can be designedas sidebank or vertical systems, meaning thatthe water flow is sideways or downward, re-spectively.

    3.4 Biofiltration Practices:A stormwater management system which in-corporates vegetative filtration, allowing run-off to slowly pass through the vegetation toreduce pollutants. In addition to vegetativefiltering, these systems may also promote theinfiltration of runoff, depending on soil condi-tions. The organic nature of the soils and sup-porting vegetation helps reduce the potentialfor ground water contamination. Biofiltrationpractices include swales, buffer strips, andbioretention areas.

    Swale with a swale block.

  • Persons involved in developing andimplementing stormwater managementprograms.

    Stormwater system designers andbuilders.

    Land developers and their consultants.

    Stormwater system plan reviewers andinspectors.

    Stormwater system owners or opera-tors.

    Public officials and citizens.


    Before discussing stormwater practices,stormwater management program consider-ations will be briefly reviewed. Successfulstormwater management requires morethan simply the use of runoff controltechniques. It also requires a stronginstitutional foundation. A key componentof this foundation is establishing effectivemechanisms to assure that stormwatersystems not only are designed and con-structed correctly, but that they also areinspected, maintained and operated properly.

    2.1 Stormwater Program Components

    This section briefly discusses the manycomponents of a successful stormwatermanagement program. No single frameworkfor a stormwater management program canbe recommended. Flexibility is needed to

    Chapter 2Stormwater Management Practices


    State and local governments have imple-mented a wide variety of programs to addressthe stormwater problems resulting fromchanges to land use. Traditionally, theseprograms have focused on the prevention orminimization of flooding to protect thehomes, buildings, property and lives of theircitizens. Drainage ordinances and pro-grams have been established in mostcommunities. Today, however, existingstormwater programs must evolve andbecome more comprehensive to addressstormwater management objectives whichextend beyond the traditional drainagefocus. Expanded program objectives nowinclude: erosion and sediment controlduring construction, water quality protec-tion, stormwater reuse, and open spaceand recreation.

    The tools or management practices that areused to prevent and mitigate these stormwaterimpacts also need to evolve. This chapterwill review the stormwater managementpractices that are most commonly usedfor stormwater treatment. For eachpractice the pollutant removal mecha-nisms, expected performance, limitationson use, and operation, maintenance andmanagement needs will be discussed andsummarized. Additionally, for each practice,specific operation, maintenance, and man-agement recommendations will be made.

    1.1. Intended Readers

    This chapter is intended for all readers of thispublication. It's information will be useful to:


  • Operation, Maintenance, and Management of Stormwater Systems


    establish or refine programs, based on anarea's existing legal authorities and institu-tional framework.

    Experience has shown that no single entitycan do everything. Program implementa-tion typically will be shared by apartnership involving all appropriatelevels of government, together with thepublic sector and all citizens. Coopera-tion and coordination among all of thepartners involved in program implemen-tation are cornerstones of successfulprograms. It is especially important that theroles of each partner involved in programimplementation be clearly stated. This willhelp to avoid duplication and distributeprogram activities to the entity most suited forthe role. This is especially true for assuringthe long term performance of stormwatermanagement practices.

    Experience also has shown that successfulstormwater management programs shareseveral common building blocks (WMI,1997). These involve the program's institu-tional framework, its technical foundations,and the many activities that are undertakenby the stormwater program (Figure 2-1).

    2.2. Stormwater Program Evolution to Address Existing Development

    Stormwater quality management programstypically must be phased in. They usuallymust be integrated with existing "drainage"programs to provide coordinated manage-ment of stormwater quantity and quality.Initial program efforts are aimed atpreventing and mitigating stormwaterproblems from new development, bothduring and after construction. Generally,these programs rely upon on-site planningand BMP implementation. Once all aspects,including inspections and operation/mainte-nance, of this new development program are

    running smoothly, the program can beexpanded to correct stormwater problemscaused by existing development and landuses (retrofitting). Section 2.3 discussesimportant components of programs aimed atstormwater from new development.

    Establishing a program to retrofit existingstormwater systems, however, presentsmany technical, institutional, financial,and cultural dilemmas. In many instances,the unavailability or high cost of land in urbanareas makes the use of conventional BMPsinfeasible. State laws and institutionalarrangements promote piecemeal, crisis-solving approaches aimed at managingstormwater within political boundaries yetstormwater follows watershed boundaries.Retrofitting often is prohibitively expensive.With many local governments already shortof funds, the need for innovative, dedicatedstormwater funding sources, such asstormwater utility fees, cannot be overem-phasized. Finally, cultural change is neededto get citizens and businesses to embracenonstructural BMPs and to support thestormwater program.

    Solving existing stormwater problems willrequire comprehensive, coordinated, creativeapproaches and technology. Essential ele-ments of a comprehensive, long-term effort toreduce pollutant loadings from existing landuses and older stormwater systems include:

    A. Watershed Management

    A watershed approach which integrates landuse planning with the development ofstormwater infrastructure is essential. Afterall, it is the intensification of land use andthe increase in impervious surfaceswithin a watershed that creates thestormwater and water resources manage-ment problems. Consequently, a water-shed management team effort is necessarywhich involves state, regional and local

  • CHAPTER 2 Stormwater Management Practices




































    Govt. RolesResponsibilities



    Adopt stormwater utility ordinance/feesAdopt program laws/regulations

    Integration with other federal, state and local programs

    Watershed planningStormwater master planningLocal land use plan

    Program evaluationCitizen surveysBldg. community surveysBMP monitoringWater body monitoring

    Stormwater retrofittingWatershed goalTargeting/prioritizationCapital improvementsRegional BMPs

    Compliance/enforcementStop work ordersFinesCivil or criminal

    Education programsSchool curriculumGeneral publicElected officialsDesignersDevelopersBuildersInspectorsPractitioners

    AdministrationLead agency?Separate agency?


    Stormwater system operation/maintenancePublic facilitiesPrivate facilitiesAdopt a pond program

    Figure 2 -1. Cornerstones (the Big Cs), Building Blocks, and Activities of a Stormwater Management Program

    InspectionsErosion/sediment controlsStormwater system constructionStormwater system operation

    Plan review and approvalSite plansErosion control plansStormwater plans

    Structural BMPsDesign criteriaResearch/performanceProper constructionProper operationMaintenance

    Performance standardsPeak discharge rateVolumeTreatment

    Nonstructural BMPsSite planningSource controlsStreet sweeping

  • Operation, Maintenance, and Management of Stormwater Systems


    urban stormwater systems makes it essentialto carefully evaluate pollutant reductiongoals, allocation strategies, and BMPimplementation. States should establish apriority watershed program which leadsto development and implementation ofwatershed management plans. Implemen-tation of these long term (15-30 years) planswill be designed to protect or restore thebeneficial uses of priority, targeted waterbodies.

    Within priority watersheds, sub-basins canbe targeted based on pollution sources,flooding, and water quality problems.Regional and local stormwater master plansare an essential component of the watershedplan. In these local plans, existing stormwatersystems can be targeted for modification toassure that citizens receive the greatestbenefit (pollutant load reduction, floodprotection) for the dollar. The upgrading ofolder systems also needs to be coordinatedwith other planned infrastructure improve-ments, such as road widenings, and withpark, recreation, and urban redevelopmentprojects .

    D. Alternative Controls

    Nonstructural BMPs and source controlsneed to be used extensively to reducestormwater pollution from already devel-oped areas. For example, street sweepersremove lots of litter, debris, and sedimentsfrom paved surfaces even if they can't collectthe smaller particles (

  • CHAPTER 2 Stormwater Management Practices


    An excellent example is the stormwater utility- a dedicated source of revenue with feesbased on a sites contribution to thestormwater problem.

    F. Innovative BMPs

    The infeasibility of using traditional BMPs toreduce stormwater pollutant loads in urbanareas requires creative and innovative BMPs.Regional stormwater systems, whichmanage stormwater from several devel-opments or an entire drainage basin, offermany advantages over the piecemealapproach that relies upon small, indi-vidual on-site systems. Regional systemscan use natural processes, such as extendeddetention and constructed wetlands, ormechanical processes, such as alum injection,

    Storm drain stenciling.

    Education programs for the public and forstormwater management professionalsalso are vital. Citizens, businesses, andpractitioners need to understand how theireveryday activities contribute to stormwaterpollution. For example, citizens should notdiscard leaves, grass clippings, used motoroil or other material into swales or stormsewers. Yet many people believe thatstorm "sewers" go to the wastewatertreatment plant and not to the nearestwater body. Getting youth and citizen groupsinvolved in storm sewer stenciling projects(Dump No Wastes, Drains to Lake) is anexcellent way of reducing dumping ofpotential pollutants into these conveyances.Equally important are comprehensive trainingand certification programs for those in theprivate and public sectors who design, review,construct, inspect, operate, or maintainstormwater management systems.

    E. Funding

    Even just to solve existing flooding problems,the national cost of improving stormwaterinfrastructure is gigantic. Yet, local govern-ments already are struggling financially.Traditional revenue sources such asproperty taxes cannot be relied upon topay for stormwater management. Alterna-tive funding sources are needed. Lake Jackson regional stormwater

    system, Tallahassee, Florida.

  • Operation, Maintenance, and Management of Stormwater Systems


    to reduce stormwater pollutants. Theyprovide economies of scale in construction,operation and maintenance. Regionalsystems are especially useful in managingstormwater from existing land uses. Theyneed to be a central part of any retrofittingprogram. They can also be used to providestormwater management for new develop-ment, but this requires excellent planning andan expenditure of funds by the localgovernment or a developer to build theregional system and then get repaid by thosewho use it. Regional systems are mostsuccessful when a watershed approach isused that fully integrates land use, stormwa-ter management, wetlands protection, parks,and recreation/open space.

    Innovative practices which are not landintensive are urgently needed. Injectingchemical coagulating agents into stormsewers to enhance flocculation andsedimentation of stormwater pollutants isan example. This often may be a better BMPwhere land for traditional detention basins isunavailable or expensive. Several aluminjection systems have been installed inurban areas in Florida to help restorereceiving lakes. Concerns over potentialaluminum toxicity, however, must still beaddressed before this innovative BMP can befully endorsed.

    2.3. Stormwater BMPs and NewDevelopment

    This section will briefly discuss some keyissues of using BMPs to reduce thestormwater impacts associated with newdevelopment. These issues include thestormwater program's goals, the setting ofperformance standards, and the establish-ment of design criteria for specific BMPs.

    2.3.1. Program Goals

    The goals of a stormwater managementprogram must be clearly established upfront. Until recently, this was a relativelyeasy task since programs typically wereestablished only to control stormwater peakdischarge rates. This is why stormwatermanagement frequently is referred to asdrainage -- the traditional focus is ondraining runoff away from developedproperty as quickly as possible.

    A. Stormwater Quantity Goals

    Today, even the goals of stormwater quantitymanagement are changing and broadening.Control of stormwater volume, not just peakdischarge rate, is being required in closedbasins and for discharges to estuaries. Peakdischarge rate control also is evolving - fromcontrol of a single frequency storm tomultiple frequency storms. It is becomingcommon to control the peak dischargefrom a 1 or 2-year storm to minimize theerosion of stream channels, in addition tocontrolling the peak discharges for 10-,25- and/or 100-year storms for floodcontrol. Some stormwater managemententities such as the Suwannee River WaterManagement District and the FloridaDepartment of Transportation are requiringcontrol of the critical storm. This stormcreates the biggest difference between pre-development and post-development peakdischarge rate and/or volume.

    B. Stormwater Quality Goals

    The increasing awareness of stormwaterquality problems by citizens and electedofficials, along with Federal Clean Water Actrequirements, is stimulating state and localgovernments to broaden the objectives oftheir stormwater programs. Today,stormwater management program goalsinclude consideration of stormwater

  • CHAPTER 2 Stormwater Management Practices


    quantity, stormwater quality, erosionprevention and sediment control, aes-thetic values, stormwater reuse, and evenopen space and recreational benefits.

    Stormwater quality programs need to beimplemented within the framework of thefederal Clean Water Act. It establishes twotypes of regulatory approaches to controlpollutant discharges. Technology-basedeffluent limitations reflect the best controlsavailable, considering their technical andeconomic achievability. Water quality-based effluent limitations reflect the waterquality standards and allowable pollutantloadings set up by permit (U.S. EPA, 1994).

    With respect to stormwater discharges, thelatter approach possibly can be developedand implemented through a comprehensivemonitoring approach. This not only involvestraditional water chemistry monitoring, butalso needs to includes sediment chemistry,and an assessment of physical habitat,stream bank erosion, biological communitystructure, and possibly even whole-effluenttoxicity. These techniques are moreappropriate than water column chemistry inassessing cumulative, intermittent stormwa-ter impacts.

    However, implementing a water quality-based effluent limit permit program forstormwater discharges is nearly impossiblebecause of staffing and technical limitations.The many land use changes occurring in thiscountry create tens of thousands of newstormwater discharges each year. Site-specific analyses to establish water quality-based effluent limitations for so many newdischarges simply can't be done. Addition-ally, there is a sparsity of data on stormwatertoxicity and ecological impacts. Therefore,nearly all stormwater quality permittingprograms are technology-based.

    In 1987, the EPA issued guidance on the

    development of technology-based stormwa-ter programs and the role of water qualitycriteria. The guidance recognizes that BestManagement Practices (BMPs) are theprimary mechanism for achieving waterquality standards. BMPs are controltechniques used for a given set of siteconditions to achieve stormwater qualityand quantity enhancement at a minimumcost (Wanielista and Yousef, 1986). Theguidance also recommends that stateprograms should include the followingiterative process:

    1. Design of BMPs based on site-specificconditions, technical, institutional andeconomic feasibility, and the water qualitystandards of the receiving waters.

    2. Monitoring to ensure that practices arecorrectly designed and applied.

    3. Monitoring to determine the effectivenessof BMPs in meeting water qualitystandards and the appropriateness ofwater quality criteria in reasonablyassuring protection of beneficial uses.

    4. Adjustment of BMPs when water qualitystandards are not being protected to adesigned level, or evaluation and possibleadjustment of water quality standards.

    The ultimate water quality goal of stormwatermanagement programs is to protect or restorethe beneficial uses of the receiving watersthrough the proper installation and operationof program-approved BMPs. If beneficialuses are not maintained or restored,additional BMPs need to be implementedand/or the design criteria for current BMPsshould be modified to improve theirperformance.

    2.3.2. Program Performance Standards

    Whether for BMPs serving new developmentor for retrofitting, a performance standardmust be established so that specific BMP

  • Operation, Maintenance, and Management of Stormwater Systems


    design criteria can be developed. Theperformance standard establishes atechnology-based effluent limitation forstormwater treatment systems.

    A. Stormwater Management Goals

    Ideally, the basic goal for stormwater systemsserving new development is to assure thatthe post-development peak discharge rate,volume, timing and pollutant load does notexceed pre-development levels. However,this goal usually is unattainable because ourcurrent BMPs, either alone or in combination,can not achieve this level of treatment and/orvolume control, and because of the limitationsimposed by variations in site conditions. Thisnecessitates the establishment of perfor-mance standards that can be achievedthrough the implementation of BMPs.

    B. Stormwater Treatment PerformanceStandards

    The stormwater treatment programs inFlorida, Delaware, and Maryland haveestablished similar performance standardsfor stormwater systems serving new develop-ment. They require stormwater systems toachieve at least an 80% reduction in theannual average post-development pollut-ant loading of Total Suspended Solids(TSS) discharged to fishable/swimmablewaters. This performance standard corre-sponds to secondary treatment levels,thereby helping to create greater equitybetween intermittent stormwater dischargesand the treatment requirements for traditionalpoint sources such as domestic and industrialwastewater discharges. Floridas programalso sets a 95% removal level for stormwaterdischarges to sensitive waters such aspotable supply waters, shellfish harvestingwaters, and Outstanding Florida Waters.

    2.3.3. BMP Design Criteria Factors

    Once the performance standard is estab-lished, design criteria then need to be set foreach of the various BMPs that are going tobe used for stormwater management. Thissection will briefly review some of thefactors that must be considered whensetting BMP design criteria. The primaryfactors influencing BMP removal efficiencyinclude rainfall characteristics; the volume ofstormwater that is detained, infiltrated, orreused ("treatment volume"); the time neededto recover the treatment volume; theprocesses used to capture, filter, orassimilate stormwater pollutants; whetherthe system is on-line or off-line; and siteconditions. By analyzing the factors below,an average annual pollutant removal effi-ciency can be calculated based on the annualmass of pollutants introduced and the annualmass removed.

    A. Rainfall Characteristics

    An analysis of long-term rainfall recordsneeds to be undertaken to determine thestatistical distribution of various rainfallcharacteristics such as storm intensity andduration, precipitation volume, number ofstorms, time between storms, etc. Unlikeflood control, which focuses on large,infrequent storms, effective stormwatertreatment generally relies on capturingand treating runoff from small, frequentevents that carry the majority of pollut-ants. For example, in Florida, nearly 90% ofa years storm events produce one inch ofrainfall or less, and 75% of the total annualvolume of rain falls in storms of one inch orless (Wanielista, 1977). Also, the averagetime between storms is an importantconsideration in designing stormwater man-agement practices (Wanielista et. al., 1991).

  • CHAPTER 2 Stormwater Management Practices


    B. "First Flush" Phenomenon

    "First flush" describes the washing actionthat runoff may have on accumulatedpollutants in the watershed. In the earlystages of runoff, the land surfaces, especiallyimpervious surfaces like streets and parkingareas, are flushed clean by the stormwater.This can result in higher concentrations ofsome stormwater pollutants, especiallyparticulates, during the early part of the storm(Miller, 1985). However, the occurrence of"first flush" depends on many factors,including the pollutant, conveyance sys-tem, drainage area, percent impervious-ness, rainfall patterns, and location. Forexample, in the Pacific northwest, which hasfrequent, long duration, low volume storms,first flush is much less pronounced. Where atarget pollutant is associated with the firstflush phenomenon, only this early fraction ofthe total storm runoff volume must becaptured and treated to reach the desiredtreatment level.

    C. Land Use Pollutant Loadings

    Stormwater pollutant sources, concentrationpeaks, and decay functions vary from site tosite. Accordingly, the typical stormwaterpollutant loading from any particular typeof land use can vary greatly. Runoff from

    residential lands have lower concentrationsand loadings of most pollutants whencompared to stormwater from commercialland uses or highways. Runoff from streetsand parking lots will have higher concentra-tions of heavy metals and other petroleumassociated pollutants. Consequently, settingdesign criteria for stormwater BMPs mustinclude evaluation of factors such as landuse, the pollutants on site, and thecharacteristics of the drainage basin, suchas the soil type, amount of imperviousness,type of stormwater conveyance system, andthe length and time of travel.

    D. On-line vs. off-line BMPs

    On-line BMPs capture all of the runofffrom a design storm, temporarily storing itbefore discharge. They primarily provideflood control benefits, with water qualitybenefits secondary. However, some on-lineBMPs, such as wet detention systems, can doan excellent job of achieving both objectives.

    Off-line BMPs divert the runoff "treatmentvolume" for treatment and isolate it fromthe remaining fraction of runoff, whichmust still be managed for flood control. This

    Example of first flush runofffrom a parking lot.

  • Operation, Maintenance, and Management of Stormwater Systems


    helps to improve treatment efficiency, reduceBMP maintenance, and make maintenanceeasier.

    E. BMP Efficiency and Cost Data

    During the past 15 years, many investigationsof BMP effectiveness have been performed.Typical information generated often includesthe pollutant removal effectiveness of variousBMPs, and the costs of BMP construction andoperation. A review of Florida BMPinvestigations (Wanielista and Shannon,1977) revealed that the cost of treatmentincreases exponentially beyond second-ary treatment (i.e., removal of 80% of theannual load). Therefore, higher levels oftreatment are required in Florida only forstormwater discharges to the state's mostsensitive water bodies.

    F. Site evaluation

    The soil types, slopes, geology, water tableand other features of a site will greatlyinfluence which BMPs will be most effective.Sandy soils imply using infiltration practiceswhile natural low areas and high water tablesoffer opportunities for wet detention ponds orconstructed wetlands.


    The key to properly specifying, designing,and operating treatment practices is anawareness of the pollutants in stormwaterand an understanding of the biological,chemical, and physical mechanisms that canbe used to prevent them from proceeding intoreceiving waters. Table 2-1 lists the principalmechanisms that have potential to capture,hold, and transform the various classes ofpollutants in urban runoff. The most commonstormwater pollutants and ameliorationmechanisms are summarized below:

    1. Sediment is solid material that originatesmostly from disintegrated rocks, eroded soil,or accumulated organic materials depositedon the land surface. The quantity,characteristics, and causes of the sedimentare influenced by many factors includingslope, slope length, soil characteristics, andland use, and traffic volume. Sedimentparticles vary greatly in size and density. Thesettleability of a particular sedimentparticle depends directly on it's size anddensity. Sediment size and density must bedetermined to know which BMPs are mostappropriate to remove the particles and tobuild into the stormwater managementsystem appropriate mechanisms to promotethe settling of these particles. Some soils,because of their silty, colloidal nature, canalmost never be settled once they get intosuspension. These soils may require the useof coagulating agents, such as alum or ferriccompounds, to remove them from the water.Of course, the most effective controlmethod for sedimentation is erosioncontrol--prevent the production of sedi-ment as much as possible.

    2. Oxygen-demanding substances includenumerous organic materials that are decom-posed by microorganisms thereby creating aneed for oxygen. Consequently, a stormwa-ter system such as a detention pond mustinclude mechanisms to maintain high oxygenlevels and prevent the formation of anaerobicconditions. Oxygenation mechanisms can benatural (such as shallow depths, sufficientlength and width to induce wind mixing, andorientation to maximize the opportunities forwind mixing) or mechanical (such asaerators).

    3. Heavy metals in highway runoff originatefrom the operation of motor vehicles,atmospheric deposition, and the degradationof highway materials. The most abundantheavy metals in stormwater are lead, zinc andcopper, which together account for about 90

  • CHAPTER 2 Stormwater Management Practices



    Physical sedimentation Solids, BOD, pathogens,particulate COD, P, N,synthetic organics

    Low turbulence, increasedresidence time

    Filtration Same as sedimentation Fine dense herbaceousplants, constructed filters

    Soil incorporation All Medium-fine texture

    Chemical precipitation Dissolved P, metals High alkalinity

    Adsorption Dissolved P, metals,synthetic organics

    High soil Al, Fe, organics,circumneutral pH (around 7)

    Ion exchange Dissolved metals High soil cation exchangecapacity

    Oxidation COD, petroleumhydrocarbons, syntheticorganics

    Aerobic conditions

    Photolysis Same as oxidation High light

    Volatilization Volatile petroleumhydrocarbons, syntheticorganics

    High temperature and airmovement

    Biological microbialdecomposition

    BOD, COD, petroleumhydrocarbons, syntheticorganics

    High plant surface area andsoil organics

    Plant uptake andmetabolism

    P, N, metals High plant surface area andactivity

    Natural die-off Pathogens Plant excretions, saline water

    Nitrification NH-3 Dissolved oxygen < 2 mg/l,low toxicants, temperature >5-7 C, circumneutral pH

    Denitrification NO3 + NO2 Anaerobic, low toxicants,temperature > 15 C

    TABLE 2-1. Summary of Stormwater Pollutant Removal Mechanisms

  • Operation, Maintenance, and Management of Stormwater Systems


    percent of the dissolved heavy metals and 90-98 percent of the total metal concentrations(Harper, 1985). Except for copper, zinc,and cadmium, the majority of metals arepresent in particulate form. Consequently,very good removal efficiencies (60-95%) canbe obtained in properly designed stormwatermanagement practices.

    To maximize heavy metal removal indetention designs, designers should providephysical configurations which encourage agradual reduction in flow velocity to promoteparticle sedimentation; maximize the flowlength from inlets to the discharge point;prevent short circuiting of flows andhydraulically dead zones; and includesuitable aquatic plants to promote uptake andremoval of dissolved metal species. To keepmetals bound to sediment, it is importantthat the sediment pH be kept near 7 andthat the sediments be aerobic. A decreasein pH and, to lesser extent, a reduction inredox potential, will cause metals to becomesoluble and release from the sediment(Harper, 1985). For this reason, it isimportant to monitor the accumulation ofsediment and decaying organic matter withindetention ponds since this can result inlowered pH and possible anaerobic condi-tions. Failure to properly remove sedimentscould cause release of accumulated metalsinto the underlying ground water or intosurface waters.

    4. Nutrients, such as nitrogen andphosphorus, are common constituents ofstormwater. They stimulate the growth ofalgae and other aquatic plants, andcontribute to oxygen depletion as theseplants decompose. Excessive nutrientsaccelerate the natural process of eutrophica-tion in lakes and streams. Nutrients instormwater may be either dissolved orparticulate, with particulate forms slightlydominating (about 60%). Consequently, astormwater management system, especially

    a wet detention system, must incorporateprovisions for settling to remove particulateforms of nutrients and include nutrientassimilation for dissolved forms. A littoralzone planted with suitable aquatic plantsshould be concentrated near the dischargepoint to provide nutrient assimilation.Biofiltration, swale conveyance, sedimentsumps, or a perimeter swale and berm systemcan be used to reduce particulate nutrients.

    5. Increased temperature of stormwateroccurs because urban lands, especiallyimpervious surfaces, are heated on warmdays. Runoff stored in BMPs, especiallyshallow ponds, is also heated by the sunbetween storms. Proper selection of BMPs isthe best way to minimize adverse thermalimpacts from stormwater BMP discharges.Galli (1991) ranks the potential of BMPs toraise receiving water temperatures, fromleast to most serious, as: infiltration basins than 20% of swale design depth

    6. Outlets/overflow spillway (Annual, After Major Storm)

    Good condition, no need for repairNo evidence of erosionNo evidence of any blockages

    7. Integrity of biofilter (Annual)

    Biofilter has not been blocked or filled inappropriately

    Inspection Frequency Key Annual, Monthly, After major storm

  • Operation, Maintenance, and Management of Stormwater Systems


    Action to be taken:

    If any of the answers to the above items are checked unsatisfactory, a time frame shall be estab-lished for their correction or repair

    No action necessary. Continue routine inspections ___________Correct noted facility deficiencies by ______________________

    Facility repairs were indicated and completed. Site reinspection is necessary to verify corrections.

    Site reinspection accomplished on ________________________

    Site reinspection was satisfactory. Next routine inspection is scheduled for approximately:

    ________________________________ ____________________________________ Signature of Inspector

  • Chapter 8Costs and Financing of Stormwater

    Facility Operation and Maintenancetion on the costs of stormwater system op-eration, maintenance, and management to:

    Stormwater system owners.

    Directors of stormwater utilities,public works, stormwater programs,and other public and private agenciesresponsible for stormwater systemmaintenance.

    Purchasing agents, managers, anddirectors.

    The chapter also discusses various methodsof obtaining adequate public and private fundsfor required stormwater system operation,maintenance, and management. This infor-mation is intended specifically for:

    Elected officials and other leaders ofstate, regional, and local governmentsresponsible for stormwater systemmaintenance.

    Stormwater program administrators,business administrators, comptrollers,financial directors, and other public andprivate sector officials responsible forfinancing stormwater system mainte-nance.


    To develop sound stormwater system opera-tion, maintenance, and management budgetsand determine adequate funding levels, acomprehensive data base of OMM costs is



    Even if a stormwater management programhas established effective institutional mecha-nisms to help assure that stormwater systemsare operated and maintained properly, prob-lems can arise because of inadequate knowl-edge about the costs of maintenance. An-nual program budgets must include adequatestaffing and financial resources to conduct themaintenance activities needed to assure thatstormwater systems operate properly. Addi-tionally, the stormwater program must assurethat financial mechanisms are implementedto provide the needed funding.

    The fundamental role that proper budget-ing and financing plays in the successfulperformance of effective stormwater sys-tem maintenance cannot be overempha-sized. The specific objectives of this chapterare:

    To provide operating and maintenancecost information from several stormwaterprograms around the country.

    To provide methods by which stormwaterprograms can estimate operation andmaintenance costs.

    To provide general information on variousalternative methods of financingstormwater system operation, mainte-nance, and management.

    1.1. Intended Readers

    This chapter is intended to provide informa-

  • Operation, Maintenance, and Management of Stormwater Systems


    needed. Unfortunately, there is very little harddata on the actual costs of stormwater sys-tem OMM, especially for stormwater treatmentBMPs. This chapter will present data ongeneral OMM costs along with specific costdata from several stormwater programsaround the country.

    It is important to remember that the cost ofstormwater system OMM is very site specific.Factors that determine the frequency, type,and cost of OMM include the type and size ofBMP, use of source controls, land use, con-tributing drainage area, rainfall characteristics,climate, vegetation growing system, mainte-nance access, and disposal requirements.

    Table 8-1 presents cost estimates for variousequipment and materials used in typicalstormwater management system OMM. Costsare provided both for equipment purchase andrental. In many cases, renting equipment,is a preferred alternative. This is especiallytrue for infrequently used equipment orlarger, very expensive equipment. Addi-tionally, local governments often find itadvantageous to contract for the use ofhighly specialized equipment since staffmay not have the experience needed tooperate it. Purchasing these types of equip-ment, and especially more commonly usedequipment, may be justified when it can beused for activities other than stormwater facil-ity maintenance, such as by road, publicworks, or recreation departments. For largerequipment, it may be less expensive to leasefor a short time instead of renting by the day.

    These cost estimates are intended to providegeneralized cost data to those in both the pub-lic and private sectors involved either in theactual OMM of stormwater systems, or in theplanning, budgeting and financing forstormwater system OMM. The reader shoulddevelop more detailed cost estimates basedupon local data or data pertaining to a spe-cific program or type of stormwater system.

    Sources of more specific data include localequipment sales, lease, and/or rental compa-nies, and local maintenance and constructioncontractors. Valuable information can be ob-tained from local government stormwater,public works, parks, or road departments.Consultation and coordination between thesevarious departments within local governmentsor private companies is strongly recom-mended.

    Table 8-2 summarizes the estimated per-son-hours associated with many of themore common stormwater system opera-tion, maintenance, and management activi-ties. These values can be used with ap-plicable personnel rates to determine la-bor costs for a specific stormwaterprogram or facility. The reader should notethat the estimates are based on the entire areaof a stormwater system. Additionally, dryBMPs are assumed to be entirely covered withgrass which requires regular mowing, fertil-izer, and other management. Appropriateadjustments should be made for wet BMPsand for facilities that are larger than one acre.

    In addition to labor and materials costs,an additional allowance needs to be madefor the disposal of trash, debris, leaves,and sediments. These costs can be mini-mized by having a dedicated area where ma-terials can be composted or where sedimentscan be dewatered and reused. These areascan either be on-site near the stormwater sys-tem or at a centrally located materials yardwithin the community. Disposal of these ma-terials must comply with federal, state, and/orlocal regulations (See Chapter 9). Accord-ingly, costs and requirements can vary widely.


    This section will present cost information from

  • CHAPTER 8 Operation and Maintenance Costs and Financing


    TABLE 8 -1.Stormwater System OMM Equipment and Material Costs (1997).



    Hand mower $300 - $500 $25 - $50

    Riding mower $3,000 - $7,000 $75 - $150

    Tractor mower $20,000 - $30,000 $150 - $450

    Trimmer/edger $200 - $500 $25 - $35

    Spreader $100 - $200 $20 - $30

    Chemical sprayer $200 - $500 $25 - $40


    Hand saw $15 - $20 $5

    Chain saw $300 - $800 $15 - $35

    Pruning shears $25 - $40 $5

    Shrub trimmer $200 - $300 $25 - $35

    Brush chipper $2,000 - $10,000 $100 - $300


    Vactor truck $100,000 - $250,000 $700 - $1200

    Front end loader $60,000 - $120,000 $250 - $500

    Backhoe $50,000 - $100,000 $250 - $500

    Excavator >$100,000 $400 - $1,000

    Grader >$100,000 $400 - $1,000


    Van $18,000 - $30,000 $50 -$100

    Pickup truck $15,000 - $25,000 $50 - $100

    Dump truck $40,000 - $80,000 $100 - $200

    Light duty trailer $3,000 - $6,000 $50 - $100

    Heavy duty trailer $10,000 - $20,000 $100 - $250

  • Operation, Maintenance, and Management of Stormwater Systems


    TABLE 8 -1.

    Stormwater System OMM Equipment and Material Costs (Cont.).



    Shovel $15 $5

    Rake $15 $5

    Pick $20 $5

    Wheel barrow $100 - $250 $15 - $25

    Portable compressor $800 - $2,000 $50 - $150

    Portable generator $750 - $2,000 $50 - $150

    Concrete mixer $750 - $1,500 $50 - $100

    Welding equipment $750 - $2,000 $50 - $100



    Topsoil $35 - $50/cubic yard

    Fill soil $15 - $30/cubic yard

    Grass seed $5 - $10/pound

    Soil amenties (fertilizer, lime, etc) $0.10 - $0.25/sq. ft.

    Chemicals (ie,pesticides, herbicides, etc) $10 - $30/gallon

    Mulch $25 - $40/cubic yard

    Dry mortar mix $5/50 pound bag

    Concrete delivered $60 - $100/cubic yard

    Machine/motor lubricants $5 - $10/gallon

    Paint $20 - $40/gallon

    Paint remover $10 - $20/gallon

  • CHAPTER 8 Operation and Maintenance Costs and Financing


    TABLE 8 - 2.

    Typical Hours Needed To Perform Stormwater OMM Tasks.

    PREVENTATIVE MAINTENANCE TASKS(Values expressed in person-hours)

    TASK SMALL FACILITY(Total area < 0.25 acre)

    LARGE FACILITY(Total area > 1 acre)

    Grass cutting 1 1 - 4

    Grass management 0.5 1 - 2

    Trash & debris removal 0.5 1 - 2

    Sediment removal 4 6 - 10

    Mobilization 1 1

    Inspection & reporting 1 2

    CORRECTIVE MAINTENANCE TASKSTrash & debris removal 4 6 - 10

    Sediment removal 8 -12 8 - 40

    Dewater ing 4 8 - 16

    Aquatic vegetativemgmt.

    4 6 - 16

    Structural repairs 24 36 - 72

    Erosion repair 1 - 4 3 - 8

    Fence repair 2 - 4 4 - 10

    Snow & ice removal 1 - 4 2 - 6

    Mosquito extermination 1 2 - 4

    Mobilization 2 2 - 4

    AESTHETIC MAINTENANCE TASKSGrass trimming 0.5 - 1 1 - 4

    Weed control 0.5 - 1 2 - 4

    Landscape maintenance 1 - 2 2 - 8

    Graffiti removal 2 - 4 4 - 8

  • Operation, Maintenance, and Management of Stormwater Systems


    country associated with their facility operation, maintenance, and management activities.Because the information from each program varies so greatly, information from each programwill be presented separately and in different formats.

    3.1. City of Orlando, Florida

    Orlando has required the treatment of stormwater since 1984, with recent emphasis on retro-fitting older drainage systems to reduce stormwater pollutant loadings into the City's lakes.The City conducts a wide range of operation, maintenance, and management activities on itsstormwater systems and has a very active lake management program. Summarized beloware costs associated with major OMM activities:

    Activity CostHerbicide (Rodeo) application to ditch bottoms $170.00 per acreStreet grass control with herbicide (Roundup) $ 6.40 per city blockDitch mowing by hand using weed-eaters and mowers $ 60.00 per acreDitch mowing by large tractor $ 12.00 per acreCleaning of stormsewers and catch basins with Vactor $160.00 per hourRepair of structures (less materials) $ 50.00 per hour

    3.2. City of Fresno, California

    Fresno developed and is implementing a stormwater master plan which relies upon regionalstormwater retention (infiltration) facilities. The city's facilities are classified as "stormwatersystems", "recharge systems" or " fully landscaped systems", with the latter also serving as10 to 20 acre parks. The respective annual OMM costs for these facilities are $125/acre(stormwater systems), $197/acre (recharge systems), and $1,506/acre (landscaped systems).When accumulated sediments need to be removed from any of these systems the annualcost is approximately $275/acre. Table 8-3 provides a more detailed summary of thesecosts.

    3.3. Somerset County, New Jersey

    The primary focus of the stormwater management program in Somerset County is flood con-trol. The program, which began in 1975, operates an extensive flood control network withradiotelemetry controls of its main drainage structures. As part of its stormwater manage-ment system, a large number of dry detention basins, with concrete low flow channels, havebeen constructed. Maintenance of these systems primarily consists of grass trimming andmowing. When mowing is performed, erosion problems are identified and repaired, debrisand litter are removed, as is sediment which has accumulated in the low flow channel. TheCounty is responsible for the OMM of 52 dry detention systems with a land area of 164.5acres. These range in size from 0.5 to 21.5 acres.

    Until 1992, the County used its own maintenance crew to perform all OMM operations. In

  • CHAPTER 8 Operation and Maintenance Costs and Financing


    TABLE 8 - 3.

    Maintenance Activities and Costs for Stormwater Management Systems in Fresno, California (1996).

    STORMWATER SYSTEMS(No landscaping, 10 systems, 92.2 acres)

    Activity Cost

    Weeding $110/acre/year

    Special (erosion control) $ 6/acre/year

    Extra work (structural repairs) $ 4/acre/year

    Miscellaneous $ 4/acre/year

    FULLY LANDSCAPED SYSTEMS(10 basins, 84.1 acres)

    Mowing $770/acre/year

    Water $416/acre/year

    Extra work (erosion, structuralrepairs)


    P G & E $130/acre/year

    Rodent control $ 5/acre/year


    Basin/Size Cost Cost/Acre/Yr

    A - 10.0 acres $3,500 $350

    S - 26.9 acres $4,000 $149

    OO - 9.3 acres $ 57 $ 61

    AC - 10.4 acres $2,500 $240

    AE - 21.6 acres $1,728 $ 80

    BO - 15.0 acres $4,112 $274

    CL - 14.7 acres $4,400 $299

    CN - 21.0 acres $5,000 $238

    CO2 - 13.2 acres $1,535 $116

    CW 15 3 acres $3 602 $235

  • Operation, Maintenance, and Management of Stormwater Systems


    1993, the county solicited bids for the work and hired a private contractor who did an excellentjob. In 1994, the county once again solicited bids and received the following bids:

    Bidder Bid Price $/OMM Visit $/AcreCounty $68,236 $ 312 $414.81Bidder A $62,200 $ 284 $378.12Bidder B $56,100 $ 256 $341.03Bidder C $51,635 $ 236 $313.89

    The three bid prices include $8,000 in County costs for supervision and inspection. This costis based on three hours of supervision/inspection per day, assuming 2 to 3 basins per day, fora total of 110 days at $25 per hour personnel costs. Based on these bids, the County awardedthe work to the low bidder, a different contractor than the County had used in 1993. Thiscontractor did not perform as well as the previous contractor. The County received manycomplaints from residents about the contractor's poor OMM work. Consequently, Countystaff performed many remedial OMM tasks resulting in $6,000 in additional costs. In 1995,the County's elected officials decided to allow the County maintenance crew to once againperform all OMM operations. Even though the cost was about $5,000 more than using aprivate contractor, advantages of using the County crew included better workman-ship, quicker response time to resident requests, fewer complaints from residents,and greater accountability.

    Table 8-4 summarizes the activities and costs associated with the maintenance of 52 drydetention systems in Somerset County. The table shows the costs of maintenance for all basinsand for those with an area of 2 to 2.5 acres, the size of the typical system. It also shows the costsof performing stormwater maintenance activities two, three, and five times per year.

    TABLE 8 - 4.Summary of 1994 Stormwater System OMM Costs

    in Somerset County, New Jersey.

    ITEM ALL1994


    2 - 2.5 ACREBASINS

    2 OMM/YR 3 OMM/YR 5 OMM/YR

    Total cost $62,450 $22,037 $6,039 $2,792 $53,669

    Total #OMM 219 89 22 12 185

    Total area 164.5 49 25.5 8 131

    # Basins 52 22 11 4 37

    $/OMM $285.16 $247.61 $274.50 $232.67 $290.10

    $/Acre $379.64 $449.73 $236.82 $349.00 $409.69

    $/Basin $1,200.9 $1,001.68 $549.00 $698.00 $1,450.51

    OMM/Basin 4.21 4.04 2 3 5

    Acre/Basin 3.16 2.23 2.32 2 3.54

    $/Acre/OM $90 18 $111 32 $118 41 $116 33 $81 94

  • CHAPTER 8 Operation and Maintenance Costs and Financing


    3.4. City of Austin, Texas

    Austin, Texas began requiring the treatment of stormwater in 1984 as part of the city's programto protect its surface and ground water resources. The city's stormwater program annualbudget has varied in recent years from $16.28 million in FY93-94 to $16.76 million in FY94-95to $15.28 million in FY95-96. Stormwater OMM costs within these three budget years amountedto $3.16 million, $3.69 million, and $4.34 million. The primary funding source is from the city'sstormwater utility which collected $14.87 million, $15.42 million, and $13.56 million respec-tively in these three budget years. Additionally, stormwater OMM funding is obtained frominspection and maintenance fees which brought in $128,241, $170,000, and $260,131. Thenumber of employees at the utility has increased from 74 FTEs in FY93-94 to 78 in FY94-95to 86 in FY95-96, with increased maintenance of stormwater systems accounting for five ofthe eight new positions in this last year.

    Tables 8-5 A-E present information from the city's most recent five year stormwater mainte-nance plan. The city's budget also includes the following performance measures for OMM:

    Outcome 1993-94 1994-95 1995-96(goal)Removed sediments from creeks (cyds) n/a n/a 10,000Restore water quality ponds 8 12 20# restored ponds/maintenance FTE 0.8 2.0 4.0# water quality ponds maintained 161 273 327

    3.5. Urban Drainage and Flood Control District (Denver, Colorado)

    The UDFCD coordinates regional stormwater management in the metropolitan Denver area,covering 1608 square miles and 36 local governments. The District charges an annual drain-age fee which raises approximately $4 million per year. The District is responsible for OMMoperations at selected regional, multi-jurisdictional stormwater facilities, primarily drainageconveyances and dry detention systems. The District contracts most OMM work and con-ducts inspections to assure that the work is performed satisfactorily.

    Routine OMM activities include mowings of non-irrigated natural grasses along drainage chan-nels, regularly scheduled collection and disposal of debris and litter from the drainageway,and unscheduled debris removal that become necessary because of large storms. Non-routine OMM activities include erosion repair and construction to rehabilitate or replace exist-ing drainage structures.

    Table 8-6 summarizes information on the cost of OMM operations conducted for the UDFCD.It is important to note that the per foot costs of maintenance varies greatly depending on thewidth of the channel and its associated right of way, the type of bottom, the slope of thechannel sides, the type channel side slope stabilization, the type and extent of vegetation,and the ease of maintenance access.

  • Operation, Maintenance, and Management of Stormwater Systems


    Activity Inventor EstimatedNeed




    Contract channel vegetationremoval

    300 miles 82 miles 3X 64 miles 3X $700,000

    Contract pond vegetation removal 161 161ponds 3X 136 ponds4X


    Complaint handling N/A 1,500 1,500 $199,169

    Storm sewer locating (utility coord) N/A 2,000 loc./yr 2,000 loc./yr $91,152

    Maintenance scheduling/planning N/A N/A $206,239

    Street drainage repairs unknown unknown unknown $175,000


    Channel dredging/cleaning 300 miles 20miles 5 miles $578,984

    Bridge/culvert clearing 1,000 2,400 1,800 $579,384

    Erosion control projects 150 150 6 $200,548


    Storm sewer inlet inspection 18,000 18,000 2X 2,000 4X $51,073

    Storm sewer inlet cleaning 18,000 13,500 2X 1,500 4X $207,542

    Storm sewer inlet filter cleaning 178 7,476 7,476 $34,048

    Wet debris dewatering N/A 300 100 $293,097


    Storm sewer repair/installation 400 miles unknown 2,400 feet $277,145

    Storm sewer cleaning 400 miles unknown 10,000 feet $102,145

    Storm sewer inspection 400 miles unknown 6 miles/yr $151,073


    Water quality pond restoration 142 35 4 $212,078

    Water quality/detention pond OMM 161 126 50 N/A

    TOWN LAKE CLEANUP N/A 200 130 $34 048

    TABLE 8 - 5 A.City of Austin

    Stormwater Maintenance PlanFY 1995

    (Note: 2X,3X,4X =two times, three times, four times).

  • CHAPTER 8 Operation and Maintenance Costs and Financing


    TABLE 8 - 5 B.City of Austin

    Stormwater Maintenance PlanFY 1996.

    Activity Inventor EstimatedNeed




    Contract channel vegetationremoval

    300 miles 82 miles 3X 50 miles 3X $600,000

    Contract pond vegetation removal 273 273 ponds 3X 136 ponds4X


    Complaint handling N/A 1,650 1,650 $175,870

    Storm sewer locating (utility coord) N/A 2,330 loc./yr 2,330 loc./yr $87,935

    Maintenance scheduling/planning N/A N/A $179,170

    Street drainage repairs unknown unknown unknown $175,000


    Channel dredging/cleaning 300 miles 20miles 8 miles $1,010,061

    Bridge/culvert clearing 1,000 2,400 1,800 $533,374

    Erosion control projects 150 150 10 $342,750


    Storm sewer inlet inspection 18,000 18,000 2X 6,000 2X $66,996

    Storm sewer inlet cleaning 18,000 13,500 2X 1,900 4X $223,319

    Storm sewer inlet filter cleaning 178 8,544 8,544 $44,664

    Wet debris dewatering N/A 300 110 $89,328


    Storm sewer repair/installation 400 miles unknown 2,400 feet $173,991

    Storm sewer cleaning 400 miles unknown 10,000 feet $133,991

    Storm sewer inspection 400 miles unknown 4 miles/yr $86,996

    Special projects N/A unknown 6 projects $89,238


    Water quality pond restoration 240 56 30 $542,541

    Water quality/detention pond OMM 273 217 200 N/A

    TOWN LAKE CLEANUP N/A 200 140 $134 164

  • Operation, Maintenance, and Management of Stormwater Systems


    TABLE 8 - 5 C.City of Austin

    Stormwater Maintenance PlanFY 1997.

    Activity Inventor EstimatedNeed




    Contract channel vegetationremoval

    300 miles 82 miles 3X 72 miles 3X $700,000

    Contract pond vegetation removal 327 327 ponds 3X 327 ponds4X


    Complaint handling N/A 1,825 1,825 $181,146

    Storm sewer locating (utility coord) N/A 2,650 loc./yr 2,650 loc./yr $90,573

    Maintenance scheduling/planning N/A N/A $538,146

    Street drainage repairs unknown unknown unknown $175,000


    Channel dredging/cleaning 300 miles 20miles 9 miles $1,100,063

    Bridge/culvert clearing 1,000 2,400 2,000 $549,375

    Erosion control projects 150 150 20 $228,145


    Storm sewer inlet inspection 18,000 18,000 2X 6,000 2X $69,006

    Storm sewer inlet cleaning 18,000 13,500 2X 4,500 2X $275,018

    Storm sewer inlet filter cleaning 178 8,544 8,544 $46,003

    Wet debris dewatering N/A 300 130 $112,008


    Storm sewer repair/installation 400 miles unknown 2,600 feet $309,011

    Storm sewer cleaning 400 miles unknown 10,500 feet $138,011

    Storm sewer inspection 400 miles unknown 14 miles/yr $119,005

    Special projects N/A unknown 7 projects $92,007


    Water quality pond restoration 288 38 38 $207,176

    Water quality/detention pond OMM 327 289 289 N/A

    TOWN LAKE CLEANUP N/A 200 170 $46 004

  • CHAPTER 8 Operation and Maintenance Costs and Financing


    TABLE 8 - 5 D.City of Austin

    Stormwater Maintenance PlanFY 1998.

    Activity Inventor EstimatedNeed




    Contract channel vegetationremoval

    300 miles 82 miles 3X 78 miles 3X $750,000

    Contract pond vegetation removal 382 382 ponds 3X 382 ponds4X


    Complaint handling N/A 2,000 2,000 $186,580

    Storm sewer locating (utility coord) N/A 3,000 loc./yr 3,000 loc./yr $93,290

    Maintenance scheduling/planning N/A N/A $186,580

    Street drainage repairs unknown unknown unknown $175,000


    Channel dredging/cleaning 300 miles 20miles 15 miles $1,347,784

    Bridge/culvert clearing 1,000 2,400 2,200 $720,856

    Erosion control projects