rethinking groundwater monitoring at the hanford site

Rethinking Groundwater Monitoring at the Hanford Site

Daniel Michael Evan Dresel Charissa Chou Chris Murray Dick Gilbert Brent Pulsipher

Daniel Michael is currently executive vice president of Neptune and Company. He holds an M.S. in Environmental Biology and a BA. in Environmental Studies and Biology. Evan Dresel has a Ph.D. in geochemistry j+om the Pennsylvania State University. His work includes interpretation of chemical and radiological groundwater data at the Hanford Site. Charissa Chou is a stagscientist at Padfic Northwest National Laboratory in the Applied Geology and Geochemistry Group. Chris Murray is a staff scientist at Pacific Northwest National Laboratory in the Applied Geology and Geochemistry Group. Dr. Murray received his degree from the Geostatistics program in the Applied Earth Sciences Department of Stanford University. Dick Gilbert obtained his M.S. in Statistics at Kansas State University in 1965 and his Ph.D. in Biomathematics at the University of Washing- ton in 1969. Dr. Gilbert has been with the Statistics Group at Battelle, Pacific Northwest Laboratories for 31 years. Brent Pulsipher obtained an M.S. in Statistics from Brigham Young University in 1981. He is the statistics technical resource manager and PNNL’s Statistics Technical Network leader.

Groundwater monitoring at Department of Energy’s (DOE’S) Havzford Site is a large, expensive undertaking serving multiple puqoses, including compliance rilith regulations and DOE orders, remediation efforts under CERCLA, and sitewide risk evaluations. Like most large Federal facilities, the monitoringprogram currently in place has evolved andgrown ouer time as new requirements were established andgroups were assigned to address them. DOE and its regulators simultaneously awakened to the fact that there was a need to reevaluate the monitoring activities at Hanford, to better integrate theprogram, to avoid duplicativesampling, to improve eve yone’s understanding of theperformance of the network, and to evaluate whether adequate data could be collected for lower cost. This paper describes the approch that was developed to guide the rethiizking effort with direct and extensive involvement of DOE, EPA, Washington Department of Ecology, Indian Tribes, and DOE Contractors, and bow this approach was applied to a largeportion of thesite. Both the human element of theprocess (cultural change), as well as some of the technical details associated with the effort, including aflexible application ofEPA ’s data quality objectivesprocess, are discussed. 02000 John Wiley & Sons, Inc.

INTRODUCTION Groundwater monitoring at the Department of Energy’s (DOE) Hanford

Complex frequently comes under close scrutiny by the regulatory authori- ties, including the Washington Department of Ecology (WDOE) and the Environmental Protection Agency (EPA) Region Ten, as well as adjacent tribes and stakeholders. Beacuse of the historical operations at Hanford, and the past practice of direct discharge of wastewater into unlined trenches, pits, ponds, etc., large portions of the uppermost unconfined aquifer underlying the site are contaminated with tritium, iodine-129 and nitrates. Other contaminants present in more restricted areas include such radionuclides as techetium-99, uranium, plutonium, cesium-137, cobolt- 60, and strontium-90, various other solvents including carbon tetrachlo- ride, chloroform, trichoroethylene and dichloroethylene and other constituents such as fluoride and chromium.

0 2000 John Wiley & Sons, Inc. 19

DANIEL MICHAEL EVAN DRESEL CHARISSA CHOU CHRIS MURRAY DICK GILBERT BRENT PULSIPHER

Some stakeholders express the view that not enough is known about the nature and extent of groundwater contamination and its potential impact on the Columbia River. Others express their concern about duplicative inefficient programs and unnecessary expenditures of taxpayer dollars (e.g., see Seattle Postlntelligencer, Dec. 12,1776). These apparently divergent perspectives, combined with DOE’s concern about how to adequately monitor its facilities in the face of shrinking budgets, provided the sense of urgency needed to propel this effort forward.

DOE spent approximately 9.14 million dollars in 1778 to collect, analyze, report and interpret Hanford groundwater monitoring data (not including well installation). The monitoring program that exists today has grown and evolved over the 50 year history of the Site in a manner similar to other large industrial facilities. New wells were added to the program over the years in response to new regulatory requirements, to monitor specific facilities, or to investigate known or expected problems. During 1778 approximately 700 wells were sampled to comply with requirements of the Resource Conservation and Recovery Act (RCRA), Atomic Energy Act, DOE Orders, and the Comprehensive Environmental Response, Compensation and Liability Act (CERCLA). Many of the wells in this monitoring network have been under surveillance for over 40 years. In numerous cases, year after year, sample after sample, the same analyses are performed revealing little if any change.

In the past few years, DOE embarked on an effort to restructure groundwater monitoring activities at Hanford. This effort was launched in part due to decreasing federal budgets, in part in response to requests from WDOE and EPA, and in part simply because DOE managers recognized that the time had come to reevaluate what they were doing. As part of this restructuring effort, a single groundwater project was molded out of three historical programs, producing one consolidated annual report, rather than several separate reports. In addition, Hanford contractors were assigned distinct roles related to groundwater sampling, data analysis, modeling and other functions, thereby reducing historical redundancies and inefficien- cies. These changes marked a commitment on the part of DOE to move forward with the consolidation efforts, and to solve some of the historical logistical problems. However, DOE also decided to embark on a more fundamental, significant effort: to truly rethink the technical and regulatory basis for groundwater monitoring and develop an integrated monitoring strategy. To assist with this effort, DOE decided to implement a systematic planning process known as the Data Quality Objectives (DQO) process, with direct participation by its regulators, tribes and stakeholders.

A discussion of the process and associated outcomes that resulted from DOE’s effort to develop an integrated groundwater monitoring program is presented. The discussion will focus on approaches that were taken to: reevaluate the purpose and the use of groundwater monitoring data; come to consensus on the decisions that monitoring data are needed to support; and determine what changes to the actual monitoring design are needed to support the identified requirements.

20 REMEDIATION/SPRING 2000

RETHINKING GROUNDWATER MONITORING AT THE HANFORD SITE

Like any large business embarking on an effort to transform its organization, Hanford encountered numerous forms of resistance, complacency, and compromise.

Like any large business embarking on an effort to transform its organization, Hanford encountered numerous forms of resistance, complacency, and cornproniise. This ”human side” of the change process will also be discussed in the light of phenomena frequently observed in the business world as institutional change unfolds. Parallel to the experience of many other large institutions undergoing reengineering or reorganiza- tion efforts, the actual progress achieved through this effort took longer and fell short of the stated expectations of the participants, and yet did attain significmt achievements, successes and advances in thinking. An assessment of how well the effort achieved its goals will be presented.

SETTING THE STAGE: DEVELOPING A VISION AND FORMING A GUIDING COALITION

Early on in the process, a common set of expectations for the effort was established in a series of meetings. Project managers recognized that the type of fundamental, major change that was being contemplated would be difficult to accomplish, and that progress would not be rapid. In the culture that exists at Hanford, as is often true at large Federal Facilities, most if not all participants were vocally skeptical concerning the possibility for “real” change. Given the nuniber of parties involved, and the prevalence of internal and external disagreements and hidden agendas, it was essential to identlfy a group of senior individuals from each of the major parties, and to agree on a common set of objectives for this effort. Building this strong guiding coalition, and developing a shared vision concerning the integrated monitoring program, constituted the first stagesetting step.

Fortunately, in this instance there were only a few individuals who felt that ‘.all the system needed was a little fine tuning.” There was general acceptance of the need to create something different from what they had. Even so, getting started on this effort involved meeting “internally” within DOE and its support contractors, before opening discussion to the regulators. tribes, and stakeholders. While this process created some internal nionientuiii and excitement, when it came time to open discussions, external parties were suspicious of both the draft products generated in the internal meetings and the process itself. So, rather than saving time by creating a “strawman” set of objectives (which was the intent), this approach actually took more time than if all internal and external managers had fully participated from the start. Eventually, a consensus set of expectations for the integration effort and an explicit charter (Exhibit 1) for the team was produced. The team also acknowledged existing regulatory, administrative. and technical obstacles to achieving the vision, and coinniitted to working through the process to overcome as many of these obstacles as possible. In short, a guiding coalition was formed. However, the question of whether this coalition included people with sufficient authority and steadfast commitment t o success was yet to be tested.

One of the key obstacles concerned situations where multiple, conflicting regulatory objectives applied to a well or set of wells (for example when there was a requirement for RCRA monitoring and CERCLA

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REMEDIATION/SPRING 2000 21

DANIEL MICHAEL EVAN DRESEL CHARISSA CHOU CHRIS MURRAY DICK GILBERT BRENT PULSIPHBR

Exhibit 1. Team Charter

To apply the data quality objectives (DQO) process to the development of a sharply focused, efficient, technically defensible, decision oriented, groundwater monitoring strategy that is based on a common set of objectives, and incorporates all technical, regulatory and scientific data needs.

To design a groundwater monitoring strategy based on historical information that:

1. 2 . 3. 4.

represents the most efficient and effective use of resources; specifies the minimum number, location and frequency of sampling; maximizes the use of existing wells; focuses on key analytes and incorporates the best mixture of analytical procedures expected to achieve the data quality objectives.

To ensure that the groundwater monitoring strategy is logistically efficient, leads to streamlined reporting, integrates with vadose monitoring, and includes well decommissioning to prevent further groundwater contamination.

remediation in the same area). Other concerns included the potential for strict interpretation and application of regulations, such as requirements for RCRA monitoring, to get in the way of efforts to integrate the monitoring program and do what “makes sense.” Finally. it was recognized that it was important to involve people who were in a position to make decisions for their respective agencies/organizations.

To overcome some of these obstacles, the group decided to maintain senior manager involvement through periodic core team meetings, while holding more regular, detailed meetings among the technical and lower level managers involved in implementation of the change process. The core team agreed to apply EPAs facilitated systematic planning process, known as the Data Quality Objectives (DQO) process (EPA QMG-4 [19941), to keep discussions focused, but there was recognition that a strict application of this process at a programmatic level was not possible or desirable.

While each group came to the table with its own agendas, perspectives, and priorities, a set of joint expectations for the effort was developed (see Exhibit 2). The process of developing these expectations allowed all members of the team to express what they hoped to get out of the exercise, and to see what was important to other members. Establishing these goals also provided the team with a useful metric that could be used to gauge the success of their efforts at a later date, in addition to a useful reminder of why the effort was initiated.

SITE DESCRIPTION The Hanford Site is a U S . Department of Energy site in Eastern

Washington State that was used for plutonium production between 1944 and 1988. Industrial discharges and releases from this mission have

22 REMEDIATION/~PRING 2000


Exhibit 2. Expectations for an Integrated Monitoring Program

Efficient, technically sound monitoring capable of detecting Contamination

Keep vadosc and other source terms in mind and coordinate with Tank Waste Remediation System (TWRS) contractors

Remove existing redundancies in analyses, wells sampled, etc.

Increase emphasis on site-wide modeling

Clarify how contractors will be working together

Increase the ability to defend budgets needed to achieve goals

Identify specific decisions that data are needed for high level decisions made by each existing program should be identified and integrated

Arrive at a consensus set of objectives

Identify sources and primary pathways

Program should make technical sense and go beyond traditional interpretations of the regulations, identify those requirements that are not technically defensible, and address existing problems

Integration should entail a process to work through existing issues

Integrated monitoring should account for the concerns of the Columbia River Comprehensive Integrated Assessment (CRCIA)

Integration should result in a sharply focused, technically defensible program that makes sense and is based on a common set of objectives

The program should identify and incorporate all technical, regulatory and scientific data needs

The program should include measurement of continual discharges

The program should generate useful interpretations of data

The program should support the cleanup and waste disposal mission

impacted groundwater over approximately 250 km2 of tlie 1450 km2 site (Hartman, 1999. The impacts include radionuclides (approx. 220 kin2) and non-radioactive chemical constituents (approx. 52 km?. The groundwater contamination on site has been monitored since early in the site’s history. Exhibit 3 illustrates the general extent of radionuclide contamination at Hanford, while Exhibit 4 illustrates the general extent of non-radioactive chemical contamination on site.

Much of the existing groundwater contamination resulted from past discharges of process water, radioactive, and chemical wastes to the ground. Discharges of untreated wastewater to the ground at Hanford have ceased since June 1995. The 400 area process ponds and the 200 areas


DANIEL MICHAEL EVAN DRESEL CI-IARISSA CHOW CHRIS MURRAY DICK GILBERT BRENT PULSIPHER

treated effluent disposal facility were constructed to discharge treated waters that are considered to be non-contaminated. The 200 areas state approved land disposal site discharges water containing tritium after treatment to remove other radionuclides and chemicals. These discharges are permitted by the state. In addition, treated water from pump-and-treat groundwater remediation systems is discharged to injection wells in the 100-K, 100-H, 100-N, and 200-west areas.

Numerous landfills containing hazardous and radioactive wastes are present on site and may represent potential sources of groundwater contamination. Although many landfills are no longer active, several remain in service. The low level burial grounds store radioactive and mixed waste and continue to receive radioactive waste. Low level waste management areas 1 ,2 ,3 , and 4, located in the 200-east and 200-west areas have been designated RCRA treatment, storage, and disposal areas. The environmental restoration disposal facility, located between the 200-east and 200-west areas, is a landfill regulated under CERCLA that receives waste from remediation activities. The central landfill complex consists of the RCRA-regulated non-radioactive dangerous waste landfill and the state permitted solid waste landfill. Both have stopped receiving waste. All other landfills are no longer active but continue to contain a variety of solid and liquid waste materials and are considered past practice sites to be addressed under CERCLA or RCRA.

Waste tanks containing high level radioactive waste are also potential sources of continuing contamination. The radioactive waste tanks are located in the 200-east and 200-west areas. The oldest, single-shell, tanks do not have secondary containment and many are known or assumed to have leaked in the past, and may still be leaking today. Single-shell tank waste management areas have groundwater monitoring under RCRA interim-status requirements. Currently groundwater monitoring requirements for detection of contamination resulting from the newer, double- shell, waste tanks are exempted due to the presence of leak detection systems within the secondary containment.

Numerous facilities were used for waste disposal during the production mission at Hanford, and in many instances have produced considerable groundwater contamination. These include ponds, cribs, ditches, injection wells, and specific retention trenches. Disposal facilities that were active in 1988 and later and which may have received dangerous waste are regulated under RCRA and in many cases have groundwater monitoring requirements under that act. Other disposal facilities are considered CERCLA or RCRA past practice facilities. Contaminants remain in the vadose zone under these facilities, and may provide continuing sources of groundwater contamination.

Miscellaneous sources such as spills, pipeline leaks, sewers, septic systems, and fuel storage tanks are also considered potential sources of groundwater contamination.

COMING TO CONSENSUS The process of identifying the major decisions for which groundwater

monitoring data were required involved several steps. First an analysis of

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24 REMEDIATION/SPRINC 2000

RETHINK~NG GROUNDWATER MONITORING AT THE HANFORD SITE

Exhibit 3. Radionuclide Contamination in Groundwater at the Hanford Site



Exhibit 4. Nonradioactive Contamination in Groundwater at the Hanford Site

the primary drivers for monitoring was performed. Next, monitoring objectives associated with these drivers or otherwise identified by the planning team were listed. Decisions that were explicitly or implicitly associated with each objective or driver were then identified. Finally, a

26 REMEDIATION/~PRING 2000


Hanford’s federal facility agreement and consent order sets out a process and schedule for site remediation and a schedule for permitting TSD units.

decision logic diagram was developed as a tool for integrating the requirements, and a careful crosswalk between each of the objectives and the applicable decisions was performed.

There are three primary regulatory drivers for groundwater monitoring: the Atomic Energy Act of 1954 as amended (AEA), the Resource Conservation and Recovery Act (RCRA) of 1976 as implemented by the Washington State Department of Ecology (WDOE) through the Washing- ton state code WAC 173-303-400 and 645, and the Comprehensive Environmental Response, Compensation and Liability Act of 1980 (CERCLA) as amended (40 CFR 3001, which establishes the federal program for waste cleanup.

Two aspects of RCRA are of concern to groundwater monitoring: cleanup of RCRA past practice sites, and monitoring of treatment storage and ciisposal facilities (TSDs). Hanford’s federal facility agreement and consent order sets out a process and schedule for site remediation and a schedule for permitting TSD units.

DOE Orders 5400.1 and 5400.5 mandate groundwater monitoring under the authority of the AEA. 5400.1 requires sites to demonstrate compliance with all federal, state and local regulations. while 5400.5 defines standards and requirements for radiation protection of the public. DOE Order 5820.2. which deals with radioactive waste management, is also covered under the 54~0.1-series requirements.

Exhibit 5 presents the decision logic diagram that covers the major anticipated uses for groundwater monitoring data. Six subgroups within this figure can be identified. Boxes 1-5 represent the background information and conceptual model needed to develop a monitoring system. If new inforniation uncovers a flaw in the conceptual model upon which the monitoring program was based, or if data are inadequate to support the development of the conceptual model for some region of the site, additional data would be gathered to fill this gap. Boxes 6-8 represent the plume tracking decisions. Two decisions are evaluated:

Plume Related Decisions Do any groundwater plumes, of sufficient size and concentration to warrant interest or action, exist in an area? Are groundwater use restrictions needed?

Boxes 9-13 address the detection and/or assessment of relatively new impacts to groundwater fro111 specific source areas, and are consistent with the intent of RCKA TSD monitoring requirements.

Source Related Decisions Is ;I TSD or other potential source term impacting groundwater? Does assessment monitoring verifSi TSD or other potential source term is the source?

Boxes 14-21 address groundwater remediation decisions. At the heart of this sequence is Box 16 which asks whether new or additional remedial



Exhibit 5. Hanford Integrated Groundwater Decision Logic

proQram and historical data and conceptual model

InlisetrUCture Iw the area and Sub-areed under

~41iect addillonal cnanctarlzalion dote conceptual model

Decommlsslon or reconflpure any problem we118

I TSDI or oVYlr known souru term

Adequate evidence

aJSeumnt monllwinp verily TSD M other ptenllal

dawn a dnnking waler supply well)

Y

source Ierm Is the

INITIATE CHANGES

In DrcgreM In thls area?

IMPLEMENT REMEDY AND CONDUCT PERFORMANCE

MONITORING MONITORING

Is remedlatlon Judped praci~cm?

and establish cleanup gOab (RODZAD)

2s REMEDIATION/SPRING 2000


The development of the decision logic diagram involved an iterative process that eventually led to consensus on both the sequence and words used to describe the decisions and activities depicted.

action is needed to meet all cleanup goals. All monitoring data and previous decisions flow down to this question, although many remediation decisions have already been made (as established in records of decision for interim actions).

Remedial Action Decisions Are new or additional remedial actions needed to meet all cleanup goals? Is the (existing) remedial action performing as expected? Is the (existing) remedial action complete?

Boxes 22-24 of the diagram complete the logic, and address the stopping rule for monitoring. Monitoring is terminated when it no longer provides needed input to the decision process.

Monitoring Design Decisions Is continued monitoring in this area required or warranted?

The developnient of the decision logic diagram involved an iterative process that eventually led to consensus on both the sequence and words used to describe the decisions and activities depicted. Once completed, DOE, EPA and the two state agencies (WDOE and the Department of Health) all agreed that the decisions and logic depicted should form the basis for evaluating monitoring requirements. This diagram represented a major milestone for the project, and one that was held up as evidence of success of the effort.

APPLYING THE DQO PROCESS TO ARRIVE AT MONITORING SPECIFICATIONS

The DQO process is a planning tool specifically designed by EPA for facilitating the essential communications that must occur between data generators and data users (the decision maker and other important stakeholders) prior to designing a data collection program. Application of the DQO process results in the development of the full set of specifications needed by the statistical design team to meet the data users' expectations. These specifications include statements of the type of data that are needed to support a decision, the amount of uncertainty or error that the data user can tolerate in decisions that depend on the results derived from the data, and how the collected data will be used to support decision-making. The first two components are used to optimize the data collection or sample design efficiency. The latter component is used with the stated statistical decision rule to determine the decision outcome. Through use of the DQO process, the probability that a data collection design will generate the right type, quality and quantity of data can be greatly increased.

The DQO process was used at Hanford to guide the planning meetings in a flexible iterative manner. Use of the process ensured that all essential specifications were discussed systematically and efficiently. During the process, it was necessary to revisit the charter statement (Exhibit 1) froin



time to time to remind participants what they had set out to do. When facing the reality that this process might actually result in changing some aspect of the program for which they were responsible, people began to resist this change and question whether revising the design was actually part of the process agreed upon at the outset. The resistance to change that was observed as part of this process is typical of organizational change efforts (see, for example, Kotter, 1996). A clearly stated charter provides a tool that can assist in overcoming or at least acknowledging this resistance.

The DQO process consists of seven steps (Exhibit 6), starting with stating the problem to be solved, and going through a sequence o f steps each of which produces an essential specification for the design of a data collection activity. The process was implemented on an area-by-area basis, focusing on each of the decisions specified in the logic diagram that were applicable to the area in question. Among the specifications crucial to the Hanford groundwater monitoring program are the specific inputs to each decision (analytes or other parameters to be measured), the area and timeframe for which the decision would be made, and the decision rule which specified how data would be used to support the decision. In cases where a statistical analysis of the performance of alternative designs was conducted, limits on the probability of making an incorrect decision were specified, and designs were optimized accordingly.

Given the size and complexity of the Hanford site, a portion of the site thought to capture most of the important issues and problems was selected

Exhibit 6. Seven Steps of the Data Quality Objectives Process

~

1. Stale the Problem

+ I 2. Identify the Decision I

~~

3. Identify Inputs to the Decision

Ir 1 I I 4. Define the Study Boundaries

5. Develop a Decision Rule

* 6. Specify Limits on Decision Errors

7. Optimize the Design for Obtaining Data I



as the initial area to be considered. The selected area encompassed a major source area, known as the 200-east area, as well as the majority of the site east of this area that had previously been contaminated by groundwater flowing from this area all the way to the Columbia River.

General Problem Statement The 200-east area is the origin of the largest groundwater plume at the

Hanford site. Approximately two thirds of the groundwater under the 200- east area is Contaminated at levels greater than drinking water standards. Potential contaminant source areas include active and inactive disposal and storage sites as well as accidental spills and releases. The major types of potential sources include:

Given the size and complexity of the Hanford site, a portion of the site thought to capture most of the important issues and problems was selected as the initial area to be considered.

Ponds: Used for disposal of large quantities of aqueous discharge. This discharge generally contained what was considered (at the time) low levels of contaminants, although some accidental releases of higher concentrations of contaminants may have occurred. Because river water was used in the processing, much of the discharge to ponds was more dilute than the nahiral groundwater. Ditches and trenches: Lined or unlined ditches and trenches were used to convey water to ponds, or were used for disposal of some discharges. Cribs: Underground structures used for disposal of contaminated water to the vadose zone and groundwater system. Cribs were retired when impact on groundwater was seen. Specific retention trenches: Used for the disposal of highly contaminated water with the goal of retaining the contamination in the vadose zone to postpone or avoid unacceptable impact on the groundwater system. Trenches generally received less fluid than cribs. Injection wells: Vertical disposal wells that generally did not penetrate the water table, although the 216-B-5 injection well is a notable exception. Burial grounds: Used for the disposal of radioactive or mixed waste. The waste was mostly solid. High level waste storage tanks: Used for the storage and management of high level radioactive and mixed waste. Many singleshell tanks :$re known or assumed to have leaked. LERF (Liquid Effluent Retention Facility): A facility currently used for storage of liquid waste prior to treatment and disposal. TEDF (200 Area Treated Effluent Disposal Facilities) consists of a pair of infiltration basins that receive wastewater originating from the 200 west and 200 east Areas. The TEDF has been in operation since 1995 and is regulated by State Waste Discharge Permit ST 4502.

0

All discharge of liquid to the soil column within this area has ceased with the exception of the 200 areas TEDF, which is permitted for the


DANIEL MICHAEL EVAN DRESEL CWSSA CHOU CHRIS MURRAY DICK GILBERT BRENT PULSIPHER

Contamination from the 200-east area has impacted the part of the site to the southeast and east as far as the Columbia River, and has also impacted the site north of the ZOO-east area through the gap between Gable Mountain and Gable Butte.

disposal of treated, non-hazardous and non-radioactive waste. Waste continues to be stored in tanks, burial grounds, and the LERF.

Facilities that are no longer in use for disposal or storage may provide new or continuing sources of contamination to groundwater through several mechanisms. Continued drainage of moisture from the vadose zone is probably occurring at many facilities. Natural recharge may be enhanced by removal of vegetation and by covering surfaces with coarse- grained material. Water or sewer line leaks may provide additional water to transport contamination to groundwater in some locations.

Because of the large number of liquid disposal areas in the 200-east area, it is generally not considered practical to link most existing groundwater plumes that are now widespread to specific source areas. The general strategy for groundwater in 200-east is to monitor to track plume migration, and determine if action is needed to control the contamination, or to respond to a new source. Pilot studies have concluded that extensive remediation of groundwater contaminants through mass removal in this area is not practical.

Contamination from the 200-east area has impacted the part of the site to the southeast and east as far as the Columbia River, and has also impacted the site north of the 200-east area through the gap between Gable Mountain and Gable Butte (Exhibit 3). The DQOs developed here address the 200-east area and the areas where groundwater has or may be impacted by sources within the 200-east area and the immediate surroundings. Spatial boundaries for specific decisions will be further defined below.

The regional groundwater flow direction is generally from west to east; however, the flow continues to be influenced by past discharge of large amounts of wastewater to the B Pond, located east of the 200-east area. Radial flow from the pond produces flow towards the west in the eastern part of the 200-east area. There is a groundwater divide across the area, producing flow northward through the gap between Gable Mountain and Gable Butte. Over a large portion of the 200-east area, the gradient is almost flat. Historically, liquid disposal dominated the flow patterns. As the water table drops (operations ceased direct discharge of large volumes of water to the ponds, or other disposal areas on 6/30/95), the direction of groundwater flow is changing and monitoring wells in some areas are drying up.

Constituents that have moved northward through the gap include tritium, iodine-1 29, technetium-99, and nitrate at concentrations above drinking water standards, and cobalt-60 and cyanide at concentrations well below the drinking water standards. Flow from the southeastern part of the 200-east area is towards the southeast. Tritium and iodine-1 29 are the dominant plumes moving from the 200-east in a southeasterly direction towards the river and Richland. Additionally plumes of cobalt-60 at concentrations well below the drinking water standard and restricted amounts of nitrate at levels above the drinking water standard are found within the tritium plume. The volume of water exceeding the tritium drinking water standard has not changed greatly in the past five years. but

32 &MEDIATION/SPRING 2000


tritium concentrations in the northern part of the 300 area are increasing. Tritium in this region is closely monitored, since it is close to the Richland well fields. However this plume is not currently expected to impact the well fields.

DQO SUMMARY FOR SOURCE DETECTION DECISIONS APPLICABLE TO THE 200 EAST AREA

it applies to source detection decisions is presented below. A brief summary of the output from each step of the DQO process, 3s

Source Detection Decision 1. Is a TSD or other potential source term impacting groundwater?

This decision applies to each of the TSDs in this region, as well as a number of sites that, due to the date that operations ceased, are not regulated as RCRA sites, but nonetheless received process wastes and are potential source terms.

Inputs To identify measurements that need to be made to support this

decision. the general approach will be to apply the COC selection criteria (see Exhibit 7) to historical data to select constituents of interest based on a conceptual model developed earlier for each identified unit of interest. The use of the selection criteria is considered to be more technically defensible than a simple application of RCRA indicators (many of which are not specific to a site and have been of little or no value in the past in determining whether there is a contribution from a facility to contaminants in groundwater ).

Exhibit 7. Criteria for Defining Constituents of Interest

Constituents present at levels greater than MCLs or interim DWS are of interest through the whole area. Radionuclides that are significant contributors to effective dose equiva- lents of 4 mrendyr or greater (interim DWS). Radionuclides that are significant contributors to effective dose equiva- lents of 100 mrem/yr or greater (DOE Derived Concentration Guide). Hazardous constituents which produce hazard quotients greater than 1. Constituents present at levels greater than applicable Washington State groundwater cleanup levels. Radionuclides migrating off site in groundwater at levels above background levels. Tritium in the southern part of the site has been identified as of concern for future offsite migration. Tritium levels in the southern part of the site that indicate increasing concentration trends are of interest as predictors of possible future offsite impacts. Constituents migrating offsite at levels of potential ecological risk.



After selecting potential constituents of concern in an area, a further evaluation was performed to identifi constituents suitable for statistical or trending evaluation based on mobility, reliability of detection, lack of interferences, etc.

After selecting potential constituents of concern in an area, a further evaluation was performed to identify constituents suitable for statistical or trending evaluation based on mobility, reliability of detection, lack of interferences, etc. Other measurements needed to support RCRA detection decisions, or to continually evaluate the appropriateness of the monitoring included water level measurements to verify flow directions and local potentiometric changes.

Boundaries The 200-east region was divided into subareas for this decision. These

subareas were defined based on geographic proximity, waste types, and flow directions. In subareas that contain more than one potential source a subsequent decision on the scale of monitoring needs to be made. Four TSDs were considered during the scope of this project.

Decision Rule Three decision rules have been developed for application to the 200-

east area for this decision. Each TSD was evaluated carefully to determine the best decision rule to apply.

1. Comparison to control limits (Intrawell comparison) If for the ith sampling event the “standardized measurement” exceeds the Shewart Limit (SCL) or the CUSUM statistic exceeds the critical value h, then declare the site out of control for the i” sampling event and resample. If resample or verification sampling confirms the initial exceedance then initiate assessment or compliance monitoring activities, else continue detection monitoring. If the exceedance is readily explainable because of upgradient trends or other sources clearly unrelated to the unit in question, then reevaluate the constituents of interest and continue detection monitoring.

If any downgradient measurement (within a subregion represented by at least one upgradient well) exceeds the 95 /95 UTL (the upper 95 percent confidence limit on the 75”’ per- centile) of the upgradient well(s) for any COC, then perform verification sampling, else continue detection monitoring. If the verification sample exceeds the 7 5 percent UPL (upper prediction limit) calculated from the upgradient well data (based on the assumption that two verification samples will be taken, and based on the number of wells that were found to exceed the UTL), then take a second verification sample, else, revert to detection monitoring. If the second verification sample exceeds the 95 percent UPL, then initiate assessment activities.

In some instances the disposal history at a site may have resulted in lower concentrations of constituents of interest than

2. Comparison to upgradient wells (Interwell comparison)

3. Comparison to sitewide background



Detailed DQOs specific to each of the TSDs were developed, including modified sampling and analysis plans.

occur naturally. An example of this is B-Pond where discharge of large volumes of process water have resulted in a general dilution of groundwater dissolved solids, If concentrations of a constituent in any well are greater than the 95 percent UTL of background calculated from samples collected from wells considered to represent the background for the flow regime, then initiate assessment if the result is confirmed by a single verification sample.

Detailed DQOs specific to each of the TSDs were developed, including modified sampling and analysis plans. To become effective, each plan must be approved by the Washington Department of Ecology and be incorporated into a permit modification. At present, several plans have been submitted and are under consideration. The major change is associated with the proposed decision rules, analyte lists and data collection designs. Historically, all of these units were required to perform the traditional up/down gradient comparisons, which have led to numerous decision errors due to the close proximity of sites, and influence of regional plumes in the area. Each area was considered separately and alternative statistical tests, consistent with either EPA or American Society for Testing and Materials (ASTM) guidelines proposed (EPA, 1992; ASTM, 1996).

DQO Summary for Plume Monitoring Decisions

it applies to plume detection decisions is presented below. A brief summary of the output from each step of the DQO process, as

Plume Monitoring Decisions 1. Are any new groundwater plumes of sufficient size and concentra-

tion to warrant interest or action moving off the 200-east area or contacting the Columbia River?

If new contamination or unexpected contamination increases are detected and confirmed, then DOE will be informed, an effort to identify the source and evaluate the extent of the new plume will be initiated, and subsequent nodes in the decision logic addressed (e.g., evaluation of use restrictions).

If concentrations at a well are below drinking water standards, use restrictions could be relaxed. If concentrations are increasing above some previous use-specific threshold, further restrictions may be necessary.

2. Are further groundwater use restrictions needed?

Inputs Past data from intensive sampling of large numbers of constituents

were used to determine the main constituents of interest currently present in groundwater. Preliminary list of constituents of interest include: ICP metals, anions, gross alpha, gross beta and gamma emitters. strontium-90, technetium-99. tritium, total organic halidedtotal organic carbon and some


DANIEL MICHAEL EVAN DRESEL CHARISSA CHOW CHRIS MURRAY DICK GILBERT BRENT PWLSIPHER

The use restriction decision potentially applies to all groundwater in the upper unconfined or confined aquifers in the defined study region.

measure of inorganic carbon such as total inorganic carbon or alkalinity. Current drinking water standards for each constituent will be needed.

Boundaries The spatial boundaries for this decision include the portions of the

upper unconfined aquifer located down-gradient from the 200-east area that could be affected in the future from 200-east area sources. Two belt transects perpendicular to the direction of groundwater flow, and downgradient from the 200-east area: one to the east of the 200-east area, and one to the north across the gap will be used to monitor for previously undetected plumes. A region represented by a transect of wells along the river is also of interest to detect new plumes or greatly increased levels of known contaminants impacting the river.

The use restriction decision potentially applies to all groundwater in the upper unconfined or confined aquifers in the defined study region. The decision of whether any new plumes of interest exist will be revisited once a year. Any new findings will be confirmed by resampling the affected wells (and any previously unsampled adjacent wells) prior to the next annual sampling event. The decision of whether further use restrictions are needed will be made at least every three years based on plume mapping.

Decision Rule If one or more transect wells is found to exceed the current drinking water

standard for any constituent that previously was not above standards, and this finding is confirnied by subsequent sampling, then a plume of interest exists, efforts to identdy the source and determine the extent of the plume will be initiated, and the adequacy of existing use restrictions will be evaluated.

DESIGN EVALUATIONS To evaluate alternative designs, the DQO process recommends that

limits on uncertainty be developed to provide the statistical design team with some sense of the types of decision errors that are of concern, and the degree to which the decision maker desires to limit uncertainty. However, in mid-course evaluations such as this case study, it is common practice to provide the planning team with an idea of how well the existing design is performing, and to indicate how reductions or changes to this program would affect uncertainty. Accordingly, design evaluations were completed for each component of the monitoring program. In particular, two major components were analyzed statistically: source detection (RCRA TSD monitoring) and plume tracking. The power (ability to detect a difference between upgradient and downgradient wells) of the current RCRA monitoring design for each regulated RCRA unit was determined, and compared to alternative statistical approaches that required far fewer measurements. A geostatistical approach for determining the uncertainties in plume maps based on existing wells and a ranking of the impacts of removing wells from the monitoring network was developed. In both cases, significant reductions in the number and frequency of samples resulted, in some cases with an improvement in performance.

36 REMEDIATION/SPRING 2 0 0 0

RETHINKING GROUNDWATER MONITORING AT THE &FORD SITE

The detection monitoring program (1 73-303-645[91) is designed to

~ determine whether a RCRA-regulated unit has adversely affected the groundwater quality in the uppermost aquifer beneath the site.

I

Source Detection EPA promulgated groundwater monitoring and response standards for

certain land-based interini-status facilities in 1980 (Doc. No. 45 FR 33232, May 19, 1980), codified in 40 CFR Part 265, Subpart F, and permitted facilities in 1982 (Doc. No. 47 FR 32350, July 26, 19821, codified in 40 CFR Part 264, Subpart F. Facility owners and operators are required to sample groundwater at specified intervals and to use a statistical procedure to determine whether or not hazardous wastes from these units are contami- nating groundwater. The Hanford site is designated as a single RCRA facility and has been assigned a single identification number for the purpose of RCRA permitting activity. Because of the complexity of the Hanford Site, most of the RCRA-regulated units are interim-status facilities and will be brought into the Hanford Facility RCRA Permit through a permit modification process that will extend out past 2015. The site thus is in a state of regulatory limbo with monitoring under interim status regulations continuing for the foreseeable future.

The detection monitoring program (173-303-645[91) is designed to determine whether a RCRA-regulated unit has adversely affected the groundwater quality in the uppermost aquifer beneath the site. This may be accomplished by testing for statistically significant changes in concentrations of constituents of interest in a downgradient monitoring well relative to upgradient (or background) wells, referred to as interwell (or between-well) comparisons. This is the approach required by interim- status regulations. Alternatively, if baseline values are obtained and compared from historical measurements within a downgradient well, the comparisons are referred to as intrawell (or within-well) comparisons. Final-status regulated units are provided the flexibility of choosing either approach, based on the particular circumstances at a site.

Interim-status regulations established specific requirements for detection monitoring (e. g., comparing individual downgradient wells to upgradient wells), statistical methods (e.g., student’s t-test), and replicate sampling. More recently, these requirements have gradually been replaced by more robust approaches (developed for final-status RCRA facilities) that require fewer samples, yet result in lower false-positive (resulting in an unnecessary and expensive phase of monitoring) and false-negative (resulting in instances where actual contamination would not be detected) decision error rates. Although EPA recognized the fact that all the reasons for replacing the Student’s t-test at a permitted facility should apply equally to an interim-status facility, EPA did not amend the interim-status requirements. This was because EPA expected that by November 1988, the majority of interim-status land disposal facilities should either be permitted (and regulated under final status) or be closed (Doc. No. 53 FR 39720, October 11, 1988). The Tri Party agreement consent order between DOE, EPA and WDOE, however, extends this timeframe for Hanford. Thus a hybrid system where the application of final status statistics to the interim status sites was evaluated for the RCRA detection monitoring networks.

The team began by performing a statistical comparison of existing designs to alternative approaches developed for final-status units. The



Site-specific plans including the statistical approach and specific wells that would be monitored were developed for a target interim status TSD (the B-Pond system).

intent of this work was to determine if new approaches developed by EPA, ASTM, and others (EPA 1992, ASTM 1996, Gibbons 1994) could provide DOE with improved performance and cost savings.

Statistical power analyses based on historical data clearly demonstrated that the alternative approaches put forth by both EPA and ASTM (EPA 1992, ASTM 1996) performed better than the existing approaches. The approach Hanford was employing for detection monitoring involved the collection of four replicate samples at each well, and performance of interwell tests. The new methods involved either inter- and intra-well comparisons to detect contaminants resulting from RCRA units. Both alternatives have the desirable properties of requiring far fewer measurements, while at the same time being more sensitive and likely to detect changes associated with a unit. Based on the alternative approaches, the wells will be sampled semiannually during the active life of the regulated unit. Rather than collecting four independent samples per sampling event (as required by final-status default testing procedure, i.e., ANOVA), a single sample will be collected and analyzed.

DOE decided that due to the combined features of improved performance (ability to detect a leak) and reduced costs associated with data collection and analysis, it would propose the use of these methods now, instead of waiting years for the permit modification process that would bring each of the interim-status units under final status. This approach was consistent with the charter and mission of the team effort and reflected 3

commitment by team members to think “outside the box” in search of improved ways to meet the intent of regulations.

Site-specific plans including the statistical approach and specific wells that would be monitored were developed for a target interim status TSD (the B-Pond system). In addition final status statistical methods were proposed for monitoring of the low-level waste management areas which were slated to be permitted in 1997 (the time frame for incorporation into the permit has slipped to 2000 for other reasons). To assist WDOE in understanding these approaches, DOE sponsored a training workshop to familiarize State regulators with the RCRA statistical procedures involved.

For the low level waste management areas it was possible to define valid upgradient wells so interwell comparison approaches were em- ployed. In this case the 95/95 upper tolerance limit was generated for upgradient well concentrations using existing well data, and downgradient well values were compared to the upper tolerance limit. If exceeded, at least two verification sampling events were implemented. and if the results from both are found to exceed the 95 percent upper prediction limit for the upgradient wells, the conclusion is reached that the RCRA unit is leaking, triggering further assessment efforts leading to the development of remedial alternatives.

Intrawell comparison approaches were proposed for the B Pond system because groundwater flows in a roughly radial pattern, away from the apex of a groundwater mound created by past wastewater disposal activities. Thus, there is no “upgradient” location in the vicinity of the ponds. The intrawell comparison methods involve the developmrnt of a



I l l Another approach to improving the eficiency of groundwater monitoring involves aggregating waste units and treating the aggregates as single areas for both regulatory enforcement and monitoring.

Shewhart Control Limit (SCL) and a CUSUM Control Limit. This method detects both sudden major changes in a given well, as well as subtle longer term elevations (detected with a high degree of confidence after several sampling periods).

For each RCRA unit, a careful evaluation of historical data was performed, and the adequacy of the existing well network evaluated. This evaluation included the selection of the specific constituents to be measured for detection purposes. In many instances a new list of constituents (that included radionuclides, but dropped many standard general contamination indicators) was proposed. In addition, use of gross count indicators (e.g., gross alpha, gross beta) as screening indicators of major contaminants of interest (e.g., uranium and strontium-90) was proposed. This reduces analytical costs and was one of the DQO processes used to develop a new groundwater monitoring plan (Barnett and Chou 1998). Also, in many cases, a subset of existing wells were selected for continued monitoring. In all cases, the use of four replicate analyses was abandoned, resulting in a potential analytical cost savings of 75 percent. The resulting designs were considerably more efficient, more effective, and more scientifically justifiable. These design changes will be implemented, once approved by WDOE.

Another approach to improving the efficiency of groundwater monitoring involves aggregating waste units and treating the aggregates as single areas for both regulatory enforcement and monitoring. This approach was successfully used on a small scale at Hanford, and further aggregation of monitoring was evaluated as part of the DQO design process but was ultiniately rejected for several reasons. The first reason was that for sites in close proximity, the regulatory status and thus the level of required monitoring varied greatly. For example the 216-A-29 ditch is a RCRA TSD monitored under interim status detection monitoring that is located near the RCRA TSD PUREX cribs which are monitored as interim status assessment sites (i.e. they have impacted groundwater quality). Although the spatial relationships seemed amenable to designing a combined monitoring network, the regulatory objectives (as well as the frequency of monitoring and number of constituents to be evaluated) were very different. Extremely high risk sites-primarily high level waste tanks-were determined to be of such importance that close intensive monitoring was required. Finally there was a reluctance to either apply the prescriptive monitoring required for RCRA TSDs to past practice sites or to relax the monitoring of the TSDs to the lower intensity currently applied to past practice waste sources

Plume Tracking The primary purpose of plume tracking is to improve DOE’S under-

standing of how known groundwater contaminant plumes are moving, and to update plume maps. These data are also used to support decisions related to groundwater use in certain locations, and to support modeling and off-site dose assessments. Monitoring will continue as long as Hanford is operated as a DOE facility, and until groundwater protection standards



The information value of individual monitoring stations was approached in two ways.

are achieved. In 1996, approximately 300 wells were sampled to monitor the plumes within the area impacted by 200 east operations. As part of the DQO process, a decision was made that given the slow rate of change in the distribution of site-wide plumes, updating plume maps every three years would be adequate. The next question the DQO team sought to evaluate was whether all 300 wells were needed to support the generation of plume maps.

To evaluate the then current monitoring program, a method was sought to quantitatively rank the information value of individual monitoring stations. Using this method, a determination would be made about whether some wells could be eliminated from the monitoring network without significantly affecting the quality of the plume maps. The method was initially applied to tritium, because it is the most widespread of the three main contaminants. The resulting recommended sampling set was then tested against nitrate and iodine-129 to determine if it would be suitable for them as well.

The information value of individual monitoring stations was approached in two ways. First, a measure of spatial redundancy of the existing wells in the network was obtained using declustering weights (Deutsch, 1992). Individual monitoring wells were ranked, with very small declustering weights being indicative of a large number of active wells in the surrounding area, and large declustering weights indicating that a well is the only location providing information over a large area.

The second approach was to build a geostatistical model of the uncertainty of the contaminant distribution with respect to several contour levels of interest. Variogram modeling of the contaminant plumes based on indicator variograms (Isaaks, 1989) was used to generate a suite of conditional stochastic simulations (Goovaerts, 1997; Deutsch, 1992) of the contaminant distributions. A suite of 100 conditional simulations of the tritium concentration was generated for the base case. Using the results of the conditional simulations, statistics of interest were generated for each node in the grid including the median simulated value, other percentiles of the distribution, and the probability that the contaminant concentration exceeds a given threshold. The spread of simulated values produced at each grid node provided an estimate of the uncertainty in the contaminant concentration at that location.

Ameasure of uncertainty relative to specific thresholds of interest, referred to as the “reference uncertainty,” was used to rank each station (Kyriakidis, 1997). The reference uncertainty increases as the spread of simulated values increases, and decreases as the median simulated value diverges from the threshold of interest. One threshold of interest used was the drinking water standard (DWS) for tritium of 20,000 pCi/L, so the reference uncertainty statistic measured the uncertainty at each location with respect to the DWS (i.e., to the edge of the tritium plume where concentrations exceed the DWS). Locations where the median simulated values are well above or below the DWS are therefore well within or outside the plume, respectively, and would have a low reference uncertainty.



The impact of reducing the number of wells sampled was assessed by repeating the geostatistical analysis using truncated datasets with different numbers of wells.

A linear average of the DWS reference uncertainty statistic ranks and the declustering weight ranks was used to rank the information value of each monitoring well in the network design. The ranking produced by this metric was then modified using hydrogeological and regulatory consider- ations (e.g. requirements that a given well be monitored in support of a RCRA facility) in order to determine candidate wells for deletion from the network.

The impact of reducing the number of wells sampled was assessed by repeating the geostatistical analysis using truncated datasets with different numbers of wells. The truncated datasets included sets with 42, 72, 102, 132, and 172 data points deleted from the original database of 293 locations. The same indicator simulation program and variogram model was used to generate suites of simulations for each truncated dataset as was used for the base case. The median simulated value at each grid node was retained as an estimate of the tritium contamination for each dataset. The maps for the truncated datasets were compared with the base case map by calculating the mean absolute difference between each case and the base case. The results indicated that the accuracy of the map was not significantly affected if 72 or fewer sampling points were deleted from the base case. Deleting more than 72 sampling points (e.g., when 102 wells were removed) resulted in significant reductions in the ability to track plumes (hence the region of diminishing returns was found).

Prior to concluding that a monitoring network, less these 72 stations, would provide adequate data to support plume mapping, the effect of deleting the sampling points was also assessed by calculating and modeling the variogram for each truncated data set. All variograni modeling for the base case and truncated datasets was performed using an automated fitting routine to eliminate subjectivity in fitting the models. For datasets with 72 or fewer sampling points deleted, interpretable directional variograms were produced, in terms of the number of variogram lags supported by at least 30 data pairs. Models fit to those directional variograms agreed reasonably well with the models fit to the base case directional variograms (direction of maximum continuity reproduced within 15 degrees, and range reproduced within 25 percent).

Once the tritium sampling locations were chosen by the above procedure, tests were made to determine if those locations would also be suitable for sampling nitrate and iodine-129. The tests were the same as those previously described for tritium, involving comparison of mapping and variogram results for the truncated dataset with results from the original base case for each variable. The results indicated that the locations chosen for tritium sampling would also serve for both nitrate and iodine- 129.

The results of the geostatistical analyses indicate that monitoring goals for these plumes can be achieved with an approximately 25 percent reduction in wells sampled (72 of 293 monitoring wells not sampled). The decrease in the number of sampled monitoring wells will reduce sampling costs without significantly impacting the quality of the plume maps. This

~ ~~



In addition to plume tracking and source detection, monitoring is needed to determine i f any new groundwater plumes of sumcient size and concentration to warrant interest or action are moving o f f the 200 east area or contacting the Columbia River.

reduction has been implemented with support of the regulators. The total list of wells scheduled for plume tracking is somewhat higher (233) because additional wells monitoring specific facilities are scheduled and because a few wells were retained to provide sufficient coverage of nitrate in the southern part of the Site. This list does not include wells which sample the deeper parts of the aquifer but those represent only a small fraction of the sampling program.

N e w Plume Detection In addition to plume tracking and source detection, monitoring is

needed to determine if any new groundwater plumes of sufficient size and concentration to warrant interest or action are moving off the 200 east area or contacting the Columbia River. If new contamination or unexpected contamination increases are detected and confirmed, then an effort to identify the source and evaluate the extent of the new plume will be initiated, and subsequent nodes in the decision logic addressed (e.g., evaluation of use restrictions).

To support this decision, two transects of existing wells that generally intersect the direction of groundwater flow from the 200 east area will be monitored annually: one set to the north through Gable Mt. Gap, and one set to the east. Wells within this transect will be monitored for ICP metals, anions, gross alpha, beta and gamma, Sr-90, Tc-99, tritium, total organic halideshotal organic carbon (TOWTOC) and some measure of inorganic carbon such as total inorganic carbon (TIC) or alkalinity. If TOWTOC increases are confirmed, subsequent samples will be analyzed for volatile and semi-volatile organic compounds (VOCs and SVOCs). The transect monitoring partially offsets the cost savings of the reduction in plume monitoring discussed above, but focuses the monitoring on decisions deemed to be most critical.

EVALUATING THE SUCCESS OF THE PROCESS Efforts undertaken to rethink Hanford’s groundwater mon.itoring

program have resulted in a number of significant positive changes, both in the revised monitoring network, and in processes that will continue to be used to evaluate and update the monitoring program. Now that the team has reached consensus on the decisions and objectives that groundwater monitoring data will support, and has developed a generic tool to assist in defining how data will be used to support decisions, Hanford is poised to continue the change process until the entire site has been reevaluated. In addition, the statistical approaches and associated changes in the number, frequency and analyte lists (see Exhibit 8) resulted in significant cost savings, with either no loss, or even improvement, in the statistical power. Similar approaches are likely to be of use at other RCRA facilities (for example in the 200 west area, and reactor areas); and for evaluating plume tracking and detection associated with these areas.

Clearly, by evaluating the performance of the existing and revised monitoring designs, Hanford has a stronger basis for defending the monitoring design (and associated budget) and for determining what to

42 R.EMEDIATION/~PRING 2000

RETHINKING GROUNDWATER MONITORING AT THE HANFORD SITE ~~~

Exhibit 8. Approximate Changes to 200 East Area Monitoring Design

Preexisting Program (1996) Proposed Program

Number Number of Number Number Number of Number of Wells samples per year ol analytes of Wells samples per year of analytes

B-Pond 13 4* 9 8 2 6 LLWhU- 1 17 2* 12 12 1 or 2 12 LLWMA-2 13 2* 13 8 1 or 2 13 LERF 'f 2* 12 4 1 or 2 12

Site Wide plume tracking 293** 1 to 4 3 (most wells) 233** 1 per 3 yr 3 (most wells)

Transect 20 1 11

* Quadruplicate samples for indicator parameters: total organic carbon, total organic halides. pH, and specific conductance ** Plume tracking wells monitoring the uppermost iincY.mfined aquifer

expect if future budget cuts require further reductions in monitoring. Through implementation of the DQO process, each component of the program is more sharply focused, with a specific clearly stated use for each iiieasurenieiit included in the program. In developing a revised approach for RCRA monitoring, the planning team went beyond the strict interpretations of interim status regulations, and recommended changes that, while supporting the intent of the regulations (i.e., detection). differed from the prescribed regulatory approaches.

Developing a geostatistical model that accounts for an anisotropy (directional element) to predict plume distributions, and using that model to assess uncertainty in plume predictions, should be of great value to other sitewide modeling efforts, including the CRCIA program. Monitoring and modeling together will support meaningful interpretations, and provide decisionmakers with increased comfort in determining the need for remedial actions across the site.

There are a number of areas that require further attention, and fit in well with the current emphasis on vadose studies at Hanford. It would be beneficial to, adjust, or even eliminate the need for, groundwater monitoring. In addition, there are numerous source terms that warrant attention in a more rigorous way. These include older disposal facilities which are not RCRA TSDs. These areas were discussed by the planning team, but not formally included in the design efforts. Finally, the 200 east area consists of multiple sources in close proximity monitored as several independent networks. The close proximity of these sites provides additional protection for detecting ncw impacts and for contaminant assessments. It would be useful to quantify the interrelated support provided by the various

~

REMEDIATION/~PRING 2000 43

DANIEL MICHAEL EVAN DRESEL CHARISSA CHOU CHIUS MURRAY DICK GILBERT BRENT PULSIPHER

monitoring systems and incorporate this kind of thinking when seeking additional improvements. Finally, while significant changes have been proposed, WDOE must approve the revisions and support the direction offered by the planning team if the benefits are to be realized. To ensure success, DOE, WDOE and EPA must continue to communicate in the open fashion in which they conducted this effort, and to make the hard decisions to overcome the temptation to stick with the way things have always been done, and endorse the changes that emerge.

ACKNOWLEDGMENTS The work reported herein was performed for the U S . Department

of Energy under contract DE-AC06-76RLO 1830. We wish to acknowledge the statistical support provided by Robert F. O’Brien and Guang Chen (PNNL). Maw Furman, DOE, provided leadership throughout the effort and a thoughtfd review of this document. We also wish to extend our appreciation for the active participation by DOE, EPA Region Ten, Washington Departments of Ecology and Health, stakeholder input, and tribal input.

REFERENCES

Barnett, D. B. & Chou, C. J. (1998). Groundwater monitoring plan for the Hanford Site 216- B-3 Pond RCRA Facility, PNNL-11903. Pacific Northwest National Laboratory, Richland, Washington.

USEPA (1992). Statistical analysis of groundwater monitoring data at RCRA facilities-Draft Addendum to Interim Final Guidance EPM530-R-93-003.

ASTM (1996). Provisional standard guide for developing appropriate statistical approaches for groundwater detection monitoring programs.

USEPA, QMG-4 (1994). Guidance for the data quality objectives process.

Kotter, J.P. (1996). Leading Change, Harvard Business School Press. Cambridge, MA

Deutsch, C. V., & Journel, A. G. (1992). GSLIB: Geostatistical Software Library and User’s Guide. New York, NY: Oxford University Press.

Isaaks, E. H., & Srivastava, R. M. (1989). An Introduction to Applied Geostatistics. Oxford University Press, New York, NY. Goovaerts, P. (1997). Geostatistics for natural resources evaluation. Oxford University Press, New York, NY.

Hartnian, M.J. (ed.) (1999). Hanford site groundwater monitoring for fiscal year 1998. PNNL- 12086, Pacific Northwest National Laboratory, Richland WA.

Kyriakidis, P. C. (1997). Selecting panels for remediation in contaminated soils via stochastic imaging. Geostatistics Wollongong ’96. E. Y. Baafi and N. A. Schofield. Dordrecht, Kluwer Academic Publishers. 2: 973-983.

Gibbons, R. D., (1994). Statistical methods for groundwater monitoring. New York: Wiley.


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