October 29, 2003
Tetra Tech EM Inc. for the EPA

Tetra Tech EM Inc. (Tetra Tech) has prepared this statistical analysis report for the U.S. Environmental Protection Agency (EPA) in partial fulfillment of the s' .ement of work for Response Action Contract (RAC) No. 68-W6-0037 for Region 6, Work Assignment No. 943-RSBD-0539. The primary objective of the report is to evaluate the possible impact of the Neal's Landfill site in Monroe County, Indiana, on polychlorinated biphenyl (PCB) concentrations in fish samples collected from streams near the landfill. The fish samples evaluated in this report were collected and analyzed by EPA and by Viacom, Inc. (Viacom), the potentially responsible party for the site, during four sampling events that occurred between May 1998 and May 2003.

This statistical analysis report consists of six sections, including this introduction. Section 2.0 contains site background information for Neal's Landfill and the four fish sampling events. Section 3.0 provides a more detailed discussion of the objectives of the statistical analyses. Section 4.0 discusses the data available for the analysis and the statistical methods used to analyze the data. Section 5.0 presents and discusses the results of the statistical analyses, and Section 6.0 summarizes the conclusions and presents recommendations for future fish sampling events. References used to prepare this report are listed after Section 6.0. Appendix A presents complete PCB concentration results for all fish samples collected during the four sampling events, and Appendix B presents the results for all statistical analyses.

This section briefly summarizes the site's history and describes the four fish sampling events that generated the data analyzed in this report. Much of the site background information presented in this section was developed from Tetra Tech's revised current status report for the Neal's Landfill site (Tetra Tech 2002).

2.1 SITE HISTORY

The Neal's Landfill site is an inactive waste disposal site located about 4.5 miles west of Bloomington in Monroe County, Indiana. The site occupies about 18 acres and was used as an industrial and municipal waste landfill from 1950 to 1972. Disposal practices at the site included open burning of discarded materials. In 1966 and 1967, numerous capacitors filled with PCB-containing oil generated by Westinghouse Electric Corporation (Westinghouse, later known as CBS Corporation [CBS] and now known as Viacom) and PCB-contaminated rags, sawdust, and filter clay were disposed of at the landfill (EPA 1998).

The site was placed on the National Priorities List in October 1981. In 1985, EPA, the State of Indiana, Monroe County, the City of Bloomington, and Westinghouse (now Viacom) signed a consent decree. Under the terms of the consent decree, Viacom is to remediate six sites in the Bloomington area containing PCBs. Neal's Landfill is one of the six sites covered by the consent decree. In 1987, a number of interim measures were completed at the site, including removal of capacitors from the ground surface; removal of a total of 4,500 linear feet of contaminate.] sediment from two surface water bodiesÄ Conard's Branch (4,267 linear feet) and Richland Creek (233 linear feet); and installation of a soil cap over primary landfill areas. The interim measures also included construction of a spring treatment facility (STF), which began operation in 1990. The purpose of the STF is to collect and treat spring flow of up to I cubic foot per second (cfs). This flow is collected in a lined basin and travels by gravity to the STF, which consists of a clarifier, filters, and an activated carbon water treatment system that remove PCBs. The STF is designed to achieve an effluent PCB concentration of I part per billion (ppb). Spring flows exceeding I cfs overflow the lined basin and discharge directly to Conard's Branch.

Under the consent decree, Viacom was scheduled to excavate soil overlying the site and incinerate the soil in a municipal waste facility that Viacom was to build. However, remedial actions (RA) other than soil incineration had to be considered when the Indiana State Legislature passed a law in 1993 intended to block implementation of the incineration remedy.

In March and April 1998, EPA and Viacom conducted field ins estigations at the site. The objectives of these investigations were to characterize the landfill waste and identify PCB hot spots for removal. A total of 104 borings were drilled through landfill materials at approximately 100-foot spacings. Data from the investigations, which revealed the presence of PCB hot spots throughout the landfill at concentrations exceeding 500 parts per million (ppm), were used to evaluate RA alternatives by Viacom and government parties. The selected alternative included excavation of materials containing PCBs at concentrations exceeding 500 ppm and disposal of the materials at an off-site, Toxic Substances Control Act (TSCA)- permitted landfill. Materials containing PCBs at concentrations less than 500 ppm were to be consolidated on site and covered with a Resource Conservation and Recovery Act (RCRA) Subtitle C cap.

In April 1999, Viacom and its RA contractors began implementing the selected source removal RA under the oversight of EPA, the State of Indiana, and Monroe County. By November 1999, Viacom had completed material excavation, off-site disposal of material, waste consolidation, and construction of the RCRA Subtitle C cap.

2.2 FISH SAMPLING EVENTS

Between May 1998 and May 2003, four separate fish sampling events were conducted near Neal's Landfill. Viacom collected fish samples in May 1998, November 2002, and May 2003. U.S. EPA collected fish samples in August 2001. Fish sampling events focused on two surface water bodies- Conard's Branch and Richland Creek. Conard's Branch forms from subterranean drainage from springs located just northwest of the landfill area. Conard's Branch flows northwest and discharges to Richland Creek approximately 3,000 feet northwest of the site. Richland Creek flows west, then southwest. from Neal's Landfill.

Each fish sampling event is described briefly below. The first sampling event in May 1998 was conducted before Viacom started the source removal RA at Neal's Landfill. For subsequent statistical analyses, this event is defined as a "pre-remediation" sampling event. The remaining three sampling events were conducted after the 1999 RA and are defined as "post-remediation" sampling events. Appendix A lists all fish samples collected during these sampling events.

May 1998. During the May 1998 sampling event, Viacom collected whole fish and fillet samples from Conard's Branch (0.5 mile downstream of Neal's Landfill) and from two locations in Richland Creek (1.0 and 5.5 miles downstream). Nine types of fish were collected, but for reasons discussed in Section 4.0 below, only data for Creek Chub are usable for statistical analyses.

August 2001. EPA collected whole fish and fillet samples during the August 2001 sampling event. Whole fish samples were collected from Conard's Branch (0.5 mile downstream) and from five locations in Richland Creek (1.0, 3.0, 12.7, 21.8, and 34.5 miles downstream). Fillet samples were also collected at the 12.7-, 21.8-, and 34.5-mile downstream locations in Richland Creek. Nine types of fish were collected, but for reasons discussed in Section 4.0 below, only data for Creek Chub, Longear Sunfish, and White Sucker are usable for statistical analyses. [Note: The Indiana Department of Environmental Management (IDEM) collected several fish samples in conjunction with EPA's August 2001 sampling event. The IDEM samples were composited, and one PCB concentration result was reported for all fish of a particular type collected at each location. The IDEM results cannot be used in statisitical analyses and are not discussed further in this report.]

November 2002. Viacom collected whole fish samples from three locations and fillet samples from one location during the November 2002 sampling event. Whole fish samples were collected from Conard s Branch (0.5 mile downstream), from Richland Creek (1.0 mile downstream), and from a location in Richland Creek upstream of its confluence with Conard's Branch. Fillet samples were collected only at the downstream Richland Creek location. Three types of fish were collected (Creek Chub, Longear Sunfish, and White Sucker), and data for all three types have been used in statistical analyses.

May 2003. During the May 2003 fish sampling event, Viacom collected whole fish and fillet samples from three locations-Conard's Branch (0.5 mile downstream) and Richland Creek (1.0 and 3.0 miles downstream. Six types of fish were collected, and for reasons discussed in Section 4.0 below, data for three fish types (Creek Chub, Longear Sunfish, and White Sucker) were used in statistical analyses.

The primary objective of the statistical analyses presented in this report is to determine whether there are any significant trends (upward or downward) in PCB concentrations for fish samples collected near Neal's Landfill. The 1999 remedial actions, together with ongoing operation of the STF, are expected to gradually reduce the mass of PCBs discharged to Conard's Branch and Richland Creek. If these measures are effective in reducing PCB discharges, PCB concentrations in fish tissue should decline over time. Specifically, data from the May 1998 sampling event (pre-remediatiG~.) can be compel-. ~ with data from the post-remediation sampling events to determine whether PCB concentrations changed following the 1999 remedial action. Similarly, data for the post-remediation sampling events (August 2001 through May 2003) can be compared to determine whether any significant changes in PCB concentrations are occurring following the completion of the 1999 remedial actions.

A secondary objective of this report is to develop recommendations for future fish sampling events. This report presents a complete inventory of current fish sample results in terms of sampling event date, sampling location, fish type, number of fish collected, and the type of PCB results reported. This information along with the results of the statistical comparisons that can be made with the data currently available, can be used as the basis for recommendations concerning fish types and sampling locations for future sampling events.

Although over 200 fish samples were collected and analyzed during the four sampling events described in Section 2.2, not all of the sample results can be analyze ~ statistically. First. PCB analytical results must be comparable. Dunng the four PCB sampling events, two different analytical methods were used. and PCB concentrations measured by one method cannot be directly compared with PCB concentrations measured by the other method. Second, statistical analysis of the data for any sampling location is possible only if a sufficient number of comparable data points are available. Generally. at least three samples of a particular type of fish (analyzed by the same method) must be available for two or more sampling events. Finally, the statistical methods used must be appropriate for the type of data available for analysis. Section 4.1 briefly describes the types of available PCB results (Aroclors and congeners); Section 4.2 provides a complete inventory of fish sample results organized by sampling event, sampling location, and fish type; and Section 4.3 outlines the statistical methods Tetra Tech has used to analyze the data.

4.1 PCB ANALYTICAL METHODS AND RESULTS

As noted above, two different methods have been used to analyze PCB concentrations in fish samples collected near Neal s Landfill. For the first three sampling events, PCB concentrations for all samples ~ ere measured by gas chromatography (GC) and reported as Aroclors. Aroclors are commercial mixtures of PCBs characterized by the percentage of chlorine in the mixture. Variations of the GC method have been in use for over 25 years, and most historical PCB data for Neal's Landfill are reported as Aroclors. In this method, the GC instrument produces a series of peaks indicating the instrument's response to the Aroclor mixture present in the sample. The analyst selects a number of peaks that \vill be used to detemmine the Aroclor concentration, compares the sample results to the peak heights and pattern for a standard Aroclor mixture used to calibrate the GC~ and then uses this comparison to detemmine the Aroclor concentration in the sample.

For the November 2002 sampling event, Viacom reported two sets of Aroclor results original results using four peaks to determine the concentration and revised results using five peaks to detemmine the concentration. In this report, statistical analyses are conducted using both sets of results for the November 2002 samples. The temms "original 4-peak" results and "revised 5-peak" results are used to distinguish bets` een the two sets of results.

For some of the samples from the third sampling event (November 2002) and all of the samples from the fourth sampling event (May 2003), PCB concentrations were measured by high resolution GC/'mass spectrometry (MS) and reported as congeners. PCBs consist of a group of 209 individual chemicals called congeners, and the GC/MS method reports results for each individual congener. Congener results can be reported in two ways. First, results of all individual congeners can be summed and reported as a total PCB congener concentration. Second, the results for 13 toxic PCB congeners (as identified by the World Health Organization) can be combined to produce a "toxicity equivalent" (TEQ) concentration. At the present time, TEQ concentrations are available for both the November 2002 and May 2003 sampling events, but Viacom has reported total PCB congener results only for the May 2003 sampling event.

Currently there are no accepted methods to convert individual PCB congener or TEQ results into Aroclor results and visa versa. Statistical analyses can be conducted only when PCB results are reported in the same format. Table 1 summarizes the types of PCB results reported to date for whole fish and fillet samples for the four sampling events. Statistical comparisons are possible for data within each cell in Table 1, but data in one cell cannot be statistically compared to data in another cell.

4.2 INVENTORY OF FISH SAMPLE RESULTS

Table 2, table 3, and table 4 summarize the types of fish samples collected during the four sampling events at Neal's Landfill. The tables are organized by sampling location and sampling event date. For each location and sampling event, the tables list the types of fish collected and the numbers of samples for each fish type. The final column of the tables indicates whether the data are sufficient data for statistical analysis and the types of analyses that can be conducted. Statistical analyses are discussed further in Section 4.3.

Table 2 presents the available data for whole fish samples analyzed for total PCB Aroclor concentrations, and Table 3 presents similar results for fillet samples. As the tables indicate, much of the data cannot currently be used in statistical comparisons. For example, Crayfish were collected at the Richland Creek l-mile downstream location during the May 1998 pre-remediation sampling event, but not collected during the August 2001 and November 2002 post-remediation sampling events. Similarly, White Sucker fillet samples were collected at this location in both the May 1998 and November 2002 sampling events, but the two samples collected in May 1998 is below the minimum of three samples needed for statistical analysis.

Table 4 presents the available data for whole fish samples analyzed for TEQ concentrations. As noted in Table 1, TEQ concentrations are available tor some of the November 2002 results and all of the Mav 2003 results. Statistical analyses can be completed for most of the samples presented in Table 1. However. Crayfish and Shorthead Redhorse samples were not collected during the November 2002 sampling event.

Summary tables have not been prepared for whole fish and fillet results reported as total PCB congeners or for fillet results reported as TEQ concentrations. In each of these cases, data are available only for one sampling event, and no statistical comparisons are possible.

4.3 STATISTICAL METHODS

Based on the fish sample PCB results available for Neal's Landfill (Tables 2, 3, 4). three to pes of statistical comparisons can be made:

• Changes in fish PCB concentrations from the pre-remediation period to the post-remediation period. These changes can be evaluated by comparing the results for the May 1998 pre-remediation sampling event with the results from one or more post-remediation sampling events. These comparisons help answer the following question: "Are fish PCB concentrations lower after remediation than before remediation?"
• Changes in fish PCB concentrations during the post-remediation period. These changes can be evaluated by (1) comparing the August 2001 and November 2002 results (Table 2) and (2) comparing the November 2002 and May 2003 TEQ results (Table 1). These comparisons help answer the following question: "Are fish PCB concentrations changing over time after remediation?"
• Trends in fish PCB concentrations over time. Trends can be evaluated when comparable data are available for three or more sampling periods at a particular sampling location. The results of these analyses can be used to answer the following questions: ' Are fish PCB concentrations changing over the time period being evaluated?" and ''How quickly are the concentrations changing?"

The first two comparisons mentioned above (pre-remediation results vs. post-remediation results and post-remediation results vs. post-remediation results) each involve two different groups of data. In statistical terminology, a group of data is referred to as a "sample," and the types of statistical methods used to evaluate differences between the groups are called "two-sample" methods. The third statistical comparison requires looking at three or more groups of data and requires a different statistical method called a trend analysis. The following sections briefly describe the specific methods used to conduct both two-sample analyses and trend analyses.

4.3.1 Two-Sample Statistical Analyses

• Two-sample analyses were conducted only when at least three data points were available for each of the two sampling events analyzed.
• Two-sample analyses were conducted using Student's two-sample l-test. The Statistic program produces two t-statistics for this test. The appropriate t-statistic depends on whether data from both sampling events have equal or unequal variances. This determination was made using the F-test results included in the Statistix7 t-test output. Section 4.5 of EPA QA/G-9 (EPA 2000) describes the use of the F-test for this purpose.
• In one comparison, a nonparametric test (the Wilcoxon Rank Sum [WRS] test) was used to conduct the two-sample analysis. A critical assumption underlying the t-test is that the data being evaluated follow a normal (or bell-shaped) distribution. The WRS test vvas used as a supplemental statistical method when the data from one or both sampling events did not follow a normal distribution, as determined by the Shapiro-Wilk test for normality. The WRS test and the Shapiro-Wilk test are described in Sections 3.3 and 4.2 respectively, of EPA QA G-9 (EPA 2000).
• For all analyses, a probability value (p-value) of 0.05 was used to determine statistical significance - probability values (p-values) less than or equal to 0.05 were considered statistically significant, while p-values above 0.05 were not considered significant.

Student's t-test can be run as either a one-tailed test or as a two-tailed test. Tetra Tech used the two-tailed alternative for all statistical analysis conducted by l-test. The two-tailed test is used to determine whether fish PCB concentrations from two sampling events are different, without making any assumptions about w hether the concentrations are increasing or decreasing over time. The two-tailed test is more conservative than the one-tailed test-a larger difference between PCB concentrations for the two sampling events is needed to achieve statistical significance. A one-tailed test is appropriate for evaluating whether fish tissue PCB concentrations have changed in only one direction-for example, whether concentrations have decreased from an earlier sampling event to a later sampling event. The one-tailed test might seem appropriate for evaluating data for Neal's Landfill because fish tissue PCB concentrations are expected to decrease over time if the completed and ongoing remedial measures are effective. However, increasing PCB concentrations would be of obvious concern, and some increases were observed in comparing the November 2002 and May 2003 TEQ results.

Trend Analyses

Tetra Tech conducted all trend analyses following the methods described in Section 4.3 of EPA QA/G-9 (EPA 2000). These methods are described in more detail in Statistical Methods for Environmental Pollution Monitoring (Gilbert 1987). Tetra Tech adhered to the following general guidelines for all trend analyses:

• Trend analyses were conducted only when data were available for three or more sampling events, at least three data points were available for each sampling event, and the results of two-sample analyses involving the sampling events demonstrated statistically significant changes in PCB concentrations.
• Trend analyses were conducted using the nonparametric Mann-Kendall (M-K) test. This test can be used to evaluate whether an upward or downward trend in fish PCB concentrations exists over the sampling events evaluated. Specifically, Tetra Tech used a variation of the M-K test that evaluates multiple data points per sampling event. This variation is described in Section 4.3.4.2 of EPA QA/G-9 (EPA 2000) and in Section 16.4.3 of Gilbert (1987). Dr. John Warren of U.S. EPA's Quality Staff confirmed that this method is appropriate for evaluating fish PCB results for Neal's Landfill.
• If the M-K test indicated that a statistically significant trend existed, Sen's Slope Estimator, another nonparametric test, was used to estimate the magnitude of the trend. Sen's Slope Estimator can provide an estimate of the changes in fish PCB concentrations in units of milligrams of PCBs per kilogram of fish tissue per year. Sen's Slope Estimator is further described in Section 41.3.1 of EPA QA/G-9 (EPA 2000) and in Section 16.5 of Gilbert (1987).
• For the M-K test, a p-value of 0.05 was used to determine statistical significance-p- values less than or equal to 0.05 were considered statistically significant, while p-values above 0.05 were not considered significant.

5.0 RESULTS AND DISCUSSION

Fish samples have been collected at seven locations ranging from 0.5 to 34.5 miles downstream of Neal's Landfill. However, based on the factors outlined in Sections 4.1 and 4.2, statistical analyses are limited to two locations that contain a sufficient amount of comparable dataÄConard's Branch (0.5 miles downstream) and Richland Creek ( 1.0 mile downstream). All statistical analyses involve whole fish sample results; although fillet samples have been collected. the amount of data at ailable is not sufficient for statistical analyses. This section presents the results for (1) two-sample statistical analyses of pre- remediation results vs. post-remediation results; (2) two-sample statistical analyses of post-remediation results vs. post-remediation results; and (I) trend analyses. Complete results for these statistical analyses are presented in Appendices B-l, B-2, and B-3, respectively.

5.1 PRE-REMEDIATION VS. POST-REMEDIATION RESULTS

Table 5 summarizes the results of pre-remediation vs. post-remediation statistical analyses. These analyses are limited to Creek Chub samples collected at Conard's Branch (0.5 mile downstream and Richland Creek (1.0 mile downstream). For Conard's Branch, the sampling location closest to Neal's Landfill, there was a statistically significant decrease in Creek Chub PCB concentrations when the pre- remediation samples (May 1998) were compared to the post-remediation samples (August 2001 and November 2002 combined). The average whole fish PCB concentration decreased from 14.1 parts per million (ppm) to 5.2 ppm (using the original 4-peak November 2002 results) or 4.6 ppm (using the revised 5-peak November 2002 results).

At the Richland Creek location 1.0 mile downstream, Creek Chub PCB concentrations also decreased between the pre-remediation samples and the post-remediation samples, but this decrease was small and not statistically significant. The average whole fish PCB concentration decreased from 0.43 ppm to 0.33 ppm (using the original 4-peak November 2002 results) or 0.26 ppm (using the revised 5-peak Noverr.be. 2002 results).

For both the pre-remediation and post-remediation samples, average Creek Chub PCB concentrations were much higher in samples collected at Conard's Branch than in samples collected at Richland Creek. For pre-remediation samples, average concentrations were about 30 times higher; for post-remediation samples, average concentrations were about 15 times higher. These results suggest that the impact of continuing PCB discharges from Neal's Landfill is significant near the landfill, but decreases rapidly as downstream distance increases. Data for additional fish types and downstream sampling locations would be needed to confirm this observation.

5.2 POST-REMEDIATION VS. POST-REMEDIATION RESULTS

Table 6 summarizes the results of post-remediation vs. post-remediation statistical analyses. These analyses cover two sampling locations, Conard's Branch (0.5 mile downstream and Richland Creek (1.0 mile downstream), and three fish types, Creek Chub, Longear Sunfish. and White Sucker. PCB Aroclor results are available for post-remediation comparisons of fish samples collected in August 2001 and November 2002. PCB congener TEQ results are available for post-remediation comparisons of fish samples collected in November 2002 and May 2003.

PCB Aroclor concentrations decreased slightly between the August 2001 and November 2002 samples. but none of the decreases were statistically significant. Average PCB concentrations in Creek Chub samples collected at Conard's Branch decreased from 6.2 ppm to 4.9 ppm (or 4. I ppm using the revised --peak results). Average PCB concentrations in Longear Surfish samples collected at Richland Creek decreased from 0.60 ppm to 0.59 ppm (or 0.47 ppm using the revised 5-peak results). Average PCB concentrations in White Sucker samples collected at Richland Creek decreased from 2.1 ppm to 1.5 ppm (or 1.2 ppm using the revised 5-peak results). Additional PCB Aroclor results for these fish types and sampling locations would be needed to determine whether the observed decreases between the August 2001 and November 2002 samples represents a real trend in fish PCB concentrations or are due to random variation.

PCB congener TEQ concentrations were measured during the November 2002 and May 2003 sampling events. For Creek Chub samples collected at both Conard's Branch and Richland Creek, the TEQ concentrations showed a statistically significant increase between these two sampling events. At Conard's Branch, the average whole fish TEQ concentration increased from 72 parts per trillion (ppt) in November 2002 to 122 ppt in May 2003. At Richland Creek, the average concentration increased from 7.3 ppt to 20.3 ppt. For Longear Sunfish and White Sucker whole fish samples collected at Richland Creek, average TEQ concentrations increased slightly between November 2002 and May 2003, but the increases were not statistically significant. These comparisons involve two sampling events that were separated only by 6 months. Additional TEQ congener data for these fish types and sampling locations would be needed to determine whether the observed increases between the November 2002 and May 2003 samples represents a real trend in fish TEQ concentrations or are due to random variation.

As noted in Section 5.1, average Creek Chub TEQ concentrations were much higher in samples collected at Conard's Branch than in samples collected at Richland Creek. For the November 2002 samples, average concentrations were about 10 times higher; for the May 2003 samples, average concentrations were about 5 times higher.

5.3 TREND ANALYSES

Table 7 summarizes trend analysis results. Trend analyses were limited to Creek Chub samples collected at Conard's Branch during the May 1998 August and November 2002 sampling events. The trend analysis results indicate ~ statistically significant decreasing trend in whole fish PCB concentrations over the sampling events included. Sen's Slope Estimator indicates a 2.0 ppm-per-year decrease in PCB concentrations using the original 4-peak results for the November 2002 samples and a 2.2 ppm-per-year decrease using the revised 5-peak results for the November 2002 samples.

Fish samples were collected by Viacom and EPA at several locations downstream of Neal's Landfill during four sampling events between May 1998 and May 2003. As discussed in Section 4.0, over 200 samples have been collected and analyzed for PCB concentrations, but not all of these samples can be included in statistical analyses. The statistical analyses presented in Section 5.0 are limited to whole fish samples of three fish types (Creek Chub, Longear Sunfish, and White Sucker) collected at two sampling locations-Conard's Branch (0.5 mile downstream of Neal's Landfill) and Richland Creek (1.0 mile downstream).

Statistical analyses (both two-sample comparisons and trend analyses) comparing pre-remediation results from May 1998 with post-remediation results from August 2001 and November 2002 indicate that PCB Aroclor concentrations in Creek Chub decreased after completion of the 1999 RA. This decrease was large and statistically significant for samples collected at Conard's Branch, but was small and not statistically significant for samples collected at Richland Creek.

Results for statistical analyses that evaluated changes in PCB concentrations during the post-remediation period were ambiguous. In all analyses of PCB Aroclor results, concentrations decreased slightly from August 2001 to November 2002, but none of the decreases were statistically significant. In all analyses of PCB congner TEQ results, concentrations increased from November 2002 to May 2003, and the increases for Creek Chub at both sampling locations were statistically significant.

Future sampling events should focus on collecting data that will support statistical analysis of fish PCB concentrations during the post-remediation period. Future data must be comparable with past data, and trio issues significantly affect data comparability. First, target fish types collected at each sampling location should be consistent with fish types previously collected at each location.