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ASSESSMENT OF CONTAMINATED SEDIMENTS IN COMMENCEMENT BAY (PUGET SOUND. WASHINGTON) Thomas C. Ginn PTI Environmental Services ABSTRACT Sediments in Commencement Bay have been contaminated by a wide variety of inorganic and organic contaminants result- ing from numerous industrial activities and pollutant dis- charges. Because of this contamination and associated bio- logical effects, the area has been the subject of a Remedial Investigation/Feasibility.Study to evaluate alternatives for sediment cleanup and source control. Prior to these evalua- tions, a decision-making framework was needed to focus the evaluation of remedial alternatives on those areas and con- taminants posing the greatest hazards to the environment and to public health. The resulting assessment approach devel- oped for the Commencement Bay investigations is described, contam- Assess- and showing how a preponderance ot evidence on sediment ination and biological effects is used in an Action ment Matrix to define and rank problem contaminants problem sediments. INTRODUCTION Commencement Bay is an urban embayment of approximately 9 mi2 in south-central Puget Sound, Washington (Figures 1 and 2~. The bay opens to Puget Sound in the northwest, with the city of Tacoma situated on the south and southeast shores. The Commencement Bay study area con- sists of a series of eight waterways, the lower Puyallup River, and the Ruston shoreline. Industrialization of Commencement Bay began in the late 1800s, at which time dredging and filling operations began in the tideflats area of the Puyallup River Delta. Numerous industrial and commercial opera- tions were located in the filled areas of the bay, including pulp and lumber mills, shipbuilding facilities, metal smelting, oil refining, marinas, food processing, chemical manufacturing, and many other commercial operations. Much of the tideflats area was constructed on slag from a copper smelter at Ruston that was used as fill and ballast material. Pollutant loadings in Commencement Bay result from numerous point and nonpoint sources. Recent surveys have indicated over 281 indus- trial activities in the nearshore/tideflats area. Comprehensive 425

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426 shoreline surveys have identified over 429 point- and nonpoint-source discharges in the study area, consisting primarily of seeps, storm drains, and open channels. Only 27 of the point sources were identi- fied as NPDES-permitted discharges. Several investigations conducted in the late 1970s and early 1980s indicated that Commencement Bay waterways were contaminated by a wide variety of metals (e.g., arsenic, copper, and mercury) and organic chem- icals (e.g., PCBs, PAN, and chlorinated butadienes). The historical data suggested that sediment contamination was spatially extensive and highly heterogeneous. These studies also indicated areas of high sedi- ment toxicity, accumulation of toxic substances in indigenous biota, and the presence of liver abnormalities and tumors in flatfish. As a result of these findings, the Commencement Bay nearshore/tideflats area was added to the U.S. Environmental Protection Agency's (EPA) National Priorities List of hazardous waste sites in 1983. Subsequently, EPA entered into a cooperative agreement with the Washington Department of Ecology to conduct a remedial investigation in Commencement Bay under the Comprehensive Environmental Response, Compensation, and Liability Act (CERCLA). :~ ~ {I ./ ~ ., ~, . ~ : .~ - . . ::1 . .- - . .. ~ , :.~r . . ... .J ~ [ \ : ~ ~ -.. VASHON, ;./ as'. ISLAND ''`r ~ PT. DEFIANCE N: :\ \':: ~ ~ ~ ".-L ~ ~ x ~ . at ~ ~ . RUST it, At' i, -\ i.,:: .,.- - ~ . ... ~ \2"'-''''N ~ . COMMENCEMENT \- -: Hi,- .. - BAY ^~ ~\;~ FIGURE 1 South-central Puget Sound showing locations of Commencement Bay and Carr Inlet.

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427 I; \. . , DEFIANCES .... -. L: ; \ , ' - - : - :. \, ', ' W~2'2-2''--. ' ' . ~ ' ,~,\ '-' 2-.. RUSTON ~ .., :k :::. .... . . . . : ~ ' - . , . . _ .... _ ~ : ... . ~ . \ ... _ : . _ ,~ - , , ,~ -i FIGURE 2 Commencement Bay nearshore/tideflats study area. I.. : ,...... f: .. . . BROWN'S POINT I' ': . ' COMMENCEMENT . . . \; ' . , \ .'.''.'-' A. a, ~ ~6i~t'litii ~ CAT PA WILTEARUKEE . WATERWAY NN ~ \ i,, ,,, : t~ ' WHEELER \ . ~ , OSGOOD \N' CITY . ~ WATERWAY \\ WATERAY ~ . ~ ~ GALLUP RIVER The goal of the remedial investigation was to identify potential remedial alternatives that could be used to reduce or eliminate the risks to the environment and to public health resulting from contam- inated sediments in Commencement Bay. However, because of the complex- ity of sediment contaminants and pollutant sources in Commencement Bay and the lack of available cleanup criteria for sediment contaminants, the investigation required the development of a decision-making frame- work to assess and prioritize contaminated sediments prior to evaluat- ing cleanup alternatives. The development of this framework included the specification of several objectives associated with the assessment of sediment contamination: characterization of sediment contamination, sediment toxicity, and biological effects; development of criteria to def ine problem sediments ; application of the criteria to define problem areas; determination of problem chemicals for the problem areas; and prioritization of problem areas and problem chemicals relative to environmental and human health risks.

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428 This paper describes the approach used in the Commencement Bay reme- dial investigation to meet these objectives and the results of the overall assessment of contaminated sediments. GENERAL ASSESSMENT APPROACH The decision-making framework developed for Commencement Bay incor- porates a "preponderance-of-evidence" approach that is implemented in a step-wise manner to identify toxic problem areas (Figure 3~. Informa- tion on the extent of sediment contamination, adverse environmental effects, and potential threats to public health form the basis for pri- oritization of areas for cleanup and/or source control. The decision- making framework for the Commencement Bay investigations was developed to integrate these kinds of technical information in a form that could be understood by regulatory decision makers and the public. The frame- work uses six steps to identify and rank problem areas and problem chemicals. Study areas that exhibit high values of indices for contam- ination and biological effects relative to reference areas receive a ranking of "high priority" for evaluation of pollutant sources and potential cleanup alternatives. A review of site characteristics and historical data for Commence- ment Bay in conjunction with available information on the effects of contaminated sediments led to the development of three important prem- ises as part of the decision-making process. First, it was determined that criteria to define problem sediments could not be established a priori because of limitations in the historical database and the ab- sence of regulatory sediment criteria at the national or state levels. Therefore, site-specific criteria would be developed based on an inte- gration of historical data and data gathered as part of this investi- gation. Second, it was determined that no single chemical or biolog- ical measure of environmental conditions could be used to define Problem sediments. Therefore. Problem areas would be defined according , . ~ ~ . _ . ~ . ~ ~ ~ red . . to the magnitude and extent or cont~mlnarlon ana expects evidences oy several independent sediment and biological observations. These meas- urements would not be combined into a single index. Instead, the approach defines multiple environmental conditions to define problem areas and prompt possible remedial action. Third, it was assumed that adverse biological effects are linked to environmental conditions and that these links may be characterized empirically. Proof of cause/ effect relationships would therefore not be provided by the studies. However, quantitative relationships derived from analysis of field observations would be used, where possible, to demonstrate links between sediment contamination and biological effects. In this sense, cause/effect relationships may be implied by a preponderance of field and laboratory evidence, including the correlation of specific contam- inant concentrations with the occurrence of adverse biological effects.

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429 1 ASSEMBLE ACTION ASSESSMENT M AT R I C ES L 1 1 APPLY ACTION LEVEL GUIDELINES it. . . IDENTIFY STUDY AREAS AND SEGMENTS OF CONCERN ! i QUANTITATIVE I ' I I RELATIONSHIPS I AND HISTORICAL r , ~ ' _ i DEFINE EXTENT OF PROBLEM AREAS I WITHIN STUDY AREAS Tic SEGMENTS 1 1 RANK PROBLEM AREAS (WORST CONDITIONS) | DATA Al IDENTIFY POTENTIAL PROBLEM I 'l ~I CHEMICALS IN PROBLEM AREAS I RANK STUDY AREAS AN D 1 AREAS AN D ~ r SEGMENTS | I (AVERAGE i ! SEGMENTS I CONDITIONS) 1 ~ ! .. i ~- RANI: PROBLEM CHEMICALS , CONDUCT SOURCE EVALUA1 IONS 1 FINAL PRIORITIZATION OF PROBLEM AREAS FOR REMEDIAL ACTION FIGURE 3 Decision-making approach for evaluation and ranking of prob lem areas and problem chemicals. CHEMICAL AND BIOLOGICAL INDICATORS The preponderance-of-evidence approach discussed above required the selection of several measurements that would serve as indicators of contamination and biological effects in Commencement Bay. To conserve costs, the objective was to select the minimum numbers of indicators that could be used to adequately characterize the contaminant situation, as well as enable a prioritization of problem sediments. The following five groups of indicator variables were selected: 1. sediment contamination--concentration of chemicals and chemical groups;

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430 2. bioaccumulation--contaminant concentrations in English sole; 3. sediment toxicity--acute mortality of amphipods; abnormalities in oyster larvae; 4. benthic infauna--abundances of major taxa; 5. fish histopathology--prevalences of liver lesions in English sole. Chemical contaminants of concern selected for study in the remedial investigation included many EPA priority pollutants, EPA Hazardous Sub- stance List compounds, and several organic compounds identified in Com- mencement Bay samples that are not on the EPA lists. Chemicals were selected based on their historical occurrence and their documented potential for toxicity or bioaccumulation. Sediment concentrations of individual chemicals or groups of contaminants were normalized to sediment dry weight and organic carbon content of the sediments. Bioaccumulation of contaminants in fish was selected to evaluate the bioavailab~lity of sediment contaminants and the potential for human health effects resulting from consumption of contaminated sea- food. English sole was selected as the target species because it is abundant in the study area, lives in close contact with the bottom, and has been shown to accumulate many chemicals of concern at relatively high levels. The toxicity of sediments was based on amphipod (Rhepaxynius abronius) mortality as a measure of acute lethality and oyster larvae shell deformation as an indicator of sublethal effects. The amphipod bioassay was selected based on its demonstrated sensitivity in Commence- ment Bay, its ecological significance, and the availability of a rou- tine protocol. The oyster larvae bioassay has also been shown to be sensitive to a wide range of contaminants and was selected to gauge potential sublethal effects. Assessment of benthic infaunal assemblages was performed because of their sensitivity to sediment contamination, their importance in local trophic relationships, and their site-specific response gradients relative to sediment contamination. English sole liver was selected for pathological analyses because it is the organ most closely associated with regulation and storage of many toxic chemicals and has been shown to be afflicted with pathological disorders in sole living in contaminated areas of Puget Sound. FORM OF THE INDICATORS A series of simple indices was developed for each of the five indicators to enable ranking of areas based on the relative magnitude of observed contamination and effects. These indices have the general form of a ratio between the value of a variable at a Commencement Bay site and the value of the variable at a reference site. For the Com- mencement Bay studies, Carr Inlet (Figure 1) was selected as a refer- ence area based on its proximity and its documented low contamination. The indicator ratios are structured so that the value of the index increases as the deviation from reference conditions increases. Thus,

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431 each ratio is termed an Elevation Above Reference (EAR) index. For example, the EAR for sediment toxicity is expressed as EART = MSi/MRi where MSi- mortality or abnormality rate i at a Commencement Bay study area, and MRi= mortality or abnormality rate i at the reference area. Benthic community structure is somewhat different from the other variables because it is not expressed as a single ratio. Instead, four separate ratios were used for the abundances of crustacea, molluscs, annelids, and total organisms. The benthic EAR was also expressed as the inverse ratio of study area and reference area because affected study areas would be expected to have lower infaunal abundances. There- fore, all of the EAR are in a form where increasing magnitudes of con- tamination or biological effects are expressed as increasing values of the index. It should be noted that these indices were not used in lieu of the original data, but in addition to them. The original data were used to identify statistically detectable increases in sediment contamination, sediment toxicity, or biological effects indicators, and to determine quantitative relationships among these variables. The indices are used to reduce large, complex data sets into interpretable numbers that reflect the magnitudes of the different indicators among study areas. ACTION ASSESSMENT MATRIX The environmental contamination and effects indicators (EAR) were organized into an action assessment matrix used to compare the Commence- ment Bay study areas (Table 1~. This matrix contains the EAR for each indicator as well as the reference values for that indicator. There- fore, original values for any indicator can be obtained by multiplying the EAR by the appropriate reference value. For the Commencement Bay project, such matrices were developed for the entire study area (i.e., with waterways as the study units as in Table 1) and for individual waterways with individual sampling stations or groups of stations (i.e., waterway segments) as the study units. In assembling the matrix, each study area indicator is evaluated relative to reference conditions to determine if there is a significant difference. All biological indicators were tested using parametric or nonparametric statistical tests to determine statistical differences at P < 0.05. Because sediment chemistry data were not replicated at each site, chemical contamination in the study area was determined to be sig- nificant if it exceeded the upper end of the range of values from all Puget Sound reference areas. Development of an action assessment matrix enables the decision maker to answer the following kinds of questions relative to sediment contamination:

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432 TABLE 1 Action Assessment Matrix of Sediment Contamination, Sediment Toxicity, and Biological Effects Indices for Commencement Bay Study Areas 1 Stu(ty Arca Elcvationsa [ OCR for page 425
433 Is there a significant increase in sediment contamination, sediment toxicity, or biological effects at any study site? What combination of indicators is significant? o What are the relative magnitudes of the elevated indices (i.e., which represent the greatest relative hazard)? Evaluation of the action assessment matrix for Commencement Bay waterways (Table 1) revealed many significant areas of contamination and effects. For example, one or more metals were significantly ele- vated in all areas except St. Paul Waterway. All areas contained at least several significant organic contaminants, with maximum levels (averaged over the waterways) over 100 times higher than reference con- centrations. The matrix indicates that Blair and Milwaukee waterways had the least chemical contamination, based on the number and magnitude of significantly elevated chemical indices. Average sediment toxicity, based on one or both of the bioassay indices, was significantly elevated in all areas except Middle Water- way. The maximum toxicity occurred in St. Paul Waterway, where amphipod toxicity was 4.8 times the reference level of 9.3 percent (i.e., the average toxicity in the waterway was about 45 percent). Significant depressions in infaunal abundances were detected in five of the eight study areas. Depressions in the abundances of molluscs were the most frequently observed effect. Evaluation of the fish pathology and bioaccumulation indices indi- cated that St. Paul Waterway and the Ruston shoreline area had the least impacted fish assemblages. The value of these two indices as independent measures of contaminant effects is also indicated in the matrix, since the highest lesion prevalence occurred in an area (Middle Waterway) where there was no significant bioaccumulation in English sole. The probable explanation is that the chemicals suspected as important causative agents in the development of liver lesions (e.g., PAH) are not bioaccumulated because of rapid metabolism in fishes. Overall, the matrix demonstrated that Hylebos Waterway had the largest number of significant indicators (significant EAR for 18 chemicals or chemical groups and eight toxicity or biological effects indicators). The lowest number of significant indicators averaged over a study area was found in St. Paul Waterway. The chemical and biological data for Commencement Bay indicated that contamination, toxicity, and biological effects were heterogeneous within the eight primary study areas. Therefore, the waterways were subdivided into segments based on patterns of chemical contamination. Action assessment matrices were then constructed for each segment. DEFINITION AND RANKING OF TOXIC PROBLEM AREAS Toxic problem areas were defined as those areas with sufficient evidence of contamination and biological effects to warrant the evalu- ation of contaminant sources and possible remedial alternatives. The identification of these problem areas required the specification of cri- teria that could be applied to the action assessment matrices. Such

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434 criteria were specified as "action levels" for combinations of contami- nation and effects indices that would result in problem area identifi- cation. Exceedance of action levels was dependent on specific combina- tions of the indices being significantly elevated in the area or segment matrices. It was assumed that an area or segment requires no action unless at least one of the indicators of contamination, toxic- ity, or biological effects was significantly elevated above reference conditions. In this approach, problem areas are defined according to two basic criteria: (1) the number of indicators that are significantly ele- vated, and (2) the magnitude of elevation of each indicator. The action level criteria are summarized as follows: Significant elevation above the reference for three or more in- dices identifies a problem area requiring evaluation of sources and potential remedial action. For any two indices showing significant elevations, the decision to proceed with source and remedial action evaluations depends on the actual combination of indices and the relative degree to which they are site specific. Even when only a single index is significantly elevated, a problem area may be defined when additional criteria are met (i.e., the magnitude of the index is sufficiently above the significance threshold to warrant further evaluation). Specific action-level guidelines for the Commencement Bay project are presented in Table 2. Application of these guidelines resulted in classification of all of the areas and segments as problem areas. All areas would therefore require further evaluation. A ranking system was also implemented to identify the problem areas posing the greatest envi- ronmental or public health risks. The ranking system was independent of the criteria used to define the problem areas. The criteria for ranking problem areas are based on numerical scores of O to 4 for each indicator (Table 3~. Rank scores for each problem area or segment were based on the sum of individual scores for each indicator. All areas and segments were ranked according to aver- age conditions within the areas and on a worst-case basis according to the maximum observed value at any station within the area. Based on this approach, eight high-priority problem areas were identified (Fig- ure 4), including three within Hylebos Waterway, two within City Water- way, one within each of Sitcum and St. Paul Waterways and along the Ruston shoreline. These areas all exhibited significant contamination, toxicity, and benthic effects, in addition to having at least one signi- ficant indicator of fish pathology or bioaccumulation. The lowest ranking problem areas did not exhibit significant sediment toxicity or benthic effects. The boundaries of the problem areas were established based on data collected in the Commencement Bay investigations as well as from the historical chemical and toxicity data available for the area. Applica- tion of Apparent Effects Thresholds (AET) were especially useful for defining boundaries based entirely on sediment chemistry data. The

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435 TABLE 2 Action-Level Guidelines Condition Observed Threshold Required for Action I. Any THREE OR MORE significantly elevated indicesa II. TWO significantly elevated indices 1. Sediments contuninated, but below 80th percentile PLUS: Bioaccumulation without an increased human health nek relative to that at the reference ares, OR Sediment toxicity with less than 50 percent mortality or abnormality, OR Major benthic invertebrate taxon depressed, but by less than 96 percent 2. Sediments contaminated but below 80th percentile PLUS elevated fish pathology 3. Any TWO significantly elevated indices, but NO elevated sediment contanunation III. SINGLE significantly elevated index 1. Sediment contamination 2. Bioaccumulation 3. Sediment toxicity d. Depressed benthic abundance 5. Fish pathology Threshold exceeded, continue with definition of problem area. No inunediate action. Recommend site for future monitoring. Threshold for problem area definition exceeded if elevated contaminants are considered to be biologically available. If not, recommend site for future monitoring. Conduct analysis of chemistry to distinguish site from adjacent areas. If test fails, no immediate action warranted. Otherwise, threshold exceeded for charactencation of problem area. Re-e~raluate significance of chemical indicators. If magnitude of contamination exceeds the 80th percentile for sill study areas, recommend area for potential source evaluation at a low priority relative to areas exhibiting contamination and effects. increased human health threat, defined as: prediction of >1 additional cancer cases in the exposed population for significantly elevated carcinogens, OR For noncarcinogens, exceedance of the acceptable daily intalce value ~ required. Greater than 50 percent response (mortality or abnormality). 95 percent depression or greater of a major tarpon (equals an EAR of 20 or greater). Insufficient as ~ single indicator. Recommend site for future monitoring. Checl: adjacent areas for significant cont~nination, toxicity, or biological effects. NOTES: aCombinations of significant indices are from independent data types (i.e., sediment chemistry, bioaccumulation, sediment toxicity, benthic infauna, fish pathology). Significant indices are defined as follows: Sediment chemistry = chemical concentration at study site exceeds highest value observed at any Puget Sound reference area. Sediment toxicity, benthic abundance, bioaccumulation, and pathology ~ statistically significant (p < 0.05) difference between study area and reference area.

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436 TABLE 3 Summary of Ranking Criteria for Sediment Contamination, Toxic- ity, and Biological Effects Indicators Indicator Criteria Scor Total Metals Contamination Concentration not significant O Significant; EAR < 10 1 Significant; EAR 10-< 50 2 Significant; EAR 50-< 100 3 Significant; EAR > 100 4 Total Organic Compound Concentration not significant O Contamination Significant; EAR < 10 1 Significant; EAR 10-< 100 2 Significant; EAR 100-< 1,OOO 3 Significant; EAR > 1,000 4 Toxicitya No significant bioassay response O Amphipod or oyster bioassay significant 2 Amphipod and oyster bioassay significant 3 . > 50 percent response in either bioassay 4 Macroinverteb~ates No significant depressions O (abundance) 1 significant depression 1 2 significant depressions 2 2 3 significant depressions 3 2 1 taxon with >95% depression 4 Bioaccumulation (fish No significant chemicals O muscle) Significant chemical 1 2 significant chemicals 2 2 3 significant chemicals 3 Significant bioaccumulation of 2 1 chemical posing a human health threats 4 Fish Pathology (liver lesions Maximum Possible Score No significant lesion types 1 significant lesion type 2 significant lesion types 2 3 significant lesion types > 5% prevalence of hepatic neoplasms 4 o 1 2 3 24 . NOTES: aToxicity based on amphipod mortality and oyster larvae abnormality bioassays. bTaxa considered were total benthic taxa, Polychaeta, Mollusca, and Crustacea. CAs defined in Table 2 (Action-Level Guidelines). dLesions considered were hepatic neoplasms, preneoplastic nodules, megalocytic hepatosis, and nuclear pleomorphisms.

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437 \\\\ ~ l HYLEBos W:'r~y 'a' / `. ~\~ ._ i\ \ WATERWAY 7~: \\\ MI~AUKEE PUYALLUP RIVER I., ~ \\ WHEELER OSGOOD \ WAT=WAY 1 Cry Iris - Ally a\\\ HAL Penn ~nnn FIGURE 4 Definition and prioritization of Commencement Bay problem areas. development and application of AET are discussed in Barrick et al. (these proceedings). IDENTIFICATION AND RANKING OF PROBLEM CHEMICALS HIGHEST PRIORITY PROBLEM AREAS SECOND HIGHEST PRIORITY AREAS ~ POTENTIAL PROBLEM AREAS `~ (NO CONFIRMING BIOLOGICAL '`` DATA AVAILABLE) POTENTIAL PROBLEM AREA BY HISTORICAL DATA ONLY N The Commencement Bay investigations indicated that area sediments were contaminated by numerous inorganic and organic chemicals at levels substantially above Puget Sound reference conditions. Because of the

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438 extensive list of sediment contaminants, a procedure was developed to identify and rank problem chemicals so that source and cleanup evalua- tions could be focused on the chemicals posing the greatest environ- mental or public health risk. The overall prioritization of sediment contaminants is described in Figure 5. Of all detected chemicals, chemicals of concern are defined as chemicals with concentrations exceeding all Puget Sound reference conditions. These chemicals are not necessarily considered problem chemicals, because sediments may be contaminated above reference con- ditions without exhibiting toxicity or biological effects. However, chemicals that are detected at concentrations exceeding 80 percent of the values determined for all stations within the project area were of greater concern based entirely on the magnitude of contamination. Such chemicals may be subject to source evaluations depending on available resources and the identification of problem chemicals. Problem chemicals were defined as those chemicals whose concentra- tion exceeded the AET in the problem area. Because the AET was defined as the contaminant concentration above which toxicity or benthic effects are always observed, chemicals present above this threshold may be contributing to observed biological effects. Problem chemicals were further ranked according to their association with toxicity or biologi- cal effects. Based on this approach, three priorities of problem chemi- cals were given for each problem area. The highest priority (Priority 1) chemicals are those that were present above an AET in a problem area and that also exhibited a concentration gradient corresponding to ob- served changes in sediment toxicity or benthic effects. For example, strong linear relationships were found between sediment toxicity and PCB concentrations in Hylebos Waterway and between sediment toxicity and 4-methylphenol concentrations in St. Paul Waterway. Other contami- nants were found above AET in these problem areas, but none displayed these strong relationships with sediment toxicity. Therefore, these chemicals were given the highest priority for source evaluation and cleanup actions because of their demonstrated correspondence with the observed tax- icity. It is recognized that some unidentified contami- nant~s) with similar distributions may have been the actual problem chemicals in these areas. However, source identifications for PCBs and 4-methylphenol would still be recommended based on the assumption that the problem chemical came from the same sourceks), and that corrective action at the source may effectively control its release as well as the release of the identified target chemical. CHEMICAES DETECTED CONCENTRATION EXCEEDS REFERENCE CONCENTRATION EXCEEDS 80TH PERCENTILE FIGURE 5 Prioritization of AET EXCEEDED problem chemicals. CONCENTRATION GRADIENT CORRESPONDS TO EFFECTS GRADIENT CHEMICAES OF CONCERN PROBLEM CHEMICABS

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439 Priority 2 chemicals were defined as those that occur above the AET in the problem area but show no particular relationship with effects gradients (or insufficient data were available to evaluate their corres- pondence with gradients). Chemicals with concentrations above AET only at nonbialogical stations were therefore placed no higher than Priority 2 because of the lack of biological data. Finally, chemicals with con- centrations above AET at only one station within the problem area were assigned Priority 3. Problem chemicals for problem areas that were small hot spots of sediment contamination usually fell into this category. Using this approach, Priority 1 chemicals were identified in six of the eight highest priority problem areas. These chemicals included mercury, lead, zinc, and arsenic; and PCBs, 4-methylphenol, low-MW PAH, and high-MW PAH. Priority 1 chemicals were not identified in any of the remaining 12 problem areas with lower overall priority. For most of these areas there were insufficient sampling stations to establish correspondence between sediment contamination and biological effects. Priority 2 chemicals were identified in all eight of the highest priority problem areas. Priority 2 chemicals were also identified in three of the lower priority problem areas. These chemicals included cadmium, nickel, and antimony; and hexachlorobutadiene, chlorinated benzenes, chlorinated ethenes, phenol, 2-methylphenol, N-nitrosodiphenyl- amine, dibenzofuran, selected phthalate esters, and selected tentatively identified compounds (e.g., 2-methoxyphenol). SUMMARY AND RECOMMENDATIONS In Commencement Bay, the complex situation of sediment contam- ination by multiple contaminants resulting from numerous point and nonpoint sources of pollution is typical of many urban coastal areas throughout the United States (e.g., New York Harbor, Los Angeles/Long Beach Harbor, and San Francisco Bay). Such situations require an ini- tial assessment and ranking of contaminants and areas so that remedial resources can be directed appropriately. A decision-making approach and associated criteria were developed for the Commencement Bay Superfund investigations to identify and rank problem areas and problem chemicals. This approach was successfully implemented in the study area. For this complex case of sediment contamination, it enabled regulatory agencies to focus source control and sediment cleanup activities on those sediments and contaminants posing the greatest environmental and public health hazards. This approach is recommended for other areas with contaminated sediments requiring similar assessments and prioritizations before initiating cleanup activities.