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SDMS DocID 000232791

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Katherine A. Fogarty, P.E.QProject Manager __

Jerome J. Cura, Ph.D , LSP /, Project Reviewer

Workplan for Phase 2 Ecological Risk Assessment

W. R. Grace Site Acton, Massachusetts

Prepared for:

GeoTrans, Inc 6 Lancaster County Road

Harvard, MA 01451

Prepared by:

Menzie-Cura & Associates, Inc. One Courthouse Lane, Suite 2

Chelmsford, Massachusetts 01824 (978) 453-4300

April 19, 2002

x" / /xi i y' / ' -si/̂ - • / /<f 7? CV ^/Susan B. KaneDriscoU(Ph.D

Project Reviewer

MENZIE • CURA & ASSOCIATES, INC. One Courthouse Lane, Suite Two • Chelmsford, Massachusetts 01824 • Phone 978/453-4300 Fax 978/453-7260

TABLE OF CONTENTS:

1.0 INTRODUCTION

2 1 DATA COLLECTION AND ANALYSIS 2 3 1 GOALS AND OBJECTIVES 2 32 SITE CONCEPTUAL MODEL 3

321 Environmental Setting and COPCs Known or Suspected to Exist at the Site 3 322 Likely Categories of Potentially Affected Receptors 3 323 Complete Exposure Pathways 4

3 3 IDENTIFICATION OF RECEPTORS, ASSESSMENT ENDPOINTS, AND MEASUREMENT EN DPOINTS FOR THE ECOLOGICAL RISK ASSESSMENT 4

331 Receptors 4 3 3 1 1 Benthic or Soil Invertebrates 4 3 3 1 2 Fish 4 3 3 1 3 Turtles 5 3 3 1 4 Semi-Aquatic Mammals 5

332 Selection of Assessment Endpomts 5 333 Selection of Measurement Endpomts 6

34 RISK CHARACTERIZATION FOR THE ECOLOGICAL RISK ASSESSMENT 11 341 Use of Hazard Quotients 11

3 5 DISCUSSION OF UNCERTAINTIES AND EXPOSURE ASSUMPTIONS 12

4.0 REFERENCES 13

LIST OF TABLES:

Table 1 Assessment and Measurement Endpoints for Phase 2 Ecological Risk Assessment

LIST OF FIGURES:

Figure 1-1 Site Locus

Figure 1-2 Sediment and Surface Water Sampling Location

Figure 3-1 Ecological Conceptual Model

1.0 INTRODUCTION

Based on the potential risks identified in the Screening-Level Ecological Risk Assessment, this document presents a Phase 2 Workplan for additional ecological risk assessment at the W.R. Grace site in Acton, Massachusetts (Figure 1-1; Site Locus). The Screening-Level Ecological Risk Assessment included a site description and a description of historical and recently collected surface water and sediment data, and evaluated conditions in Sinking Pond, Gravel Pit Wetland, Assabet River, Fort Pond Brook, the former North Lagoon, and North Lagoon Wetland (Figure 1-2). The results indicated that:

• Two of those areas, the former North Lagoon and Assabet River, do not exhibit a potentially unacceptable ecological risk for any contaminant;

• There is potential risk in a limited area of Gravel Pit Wetland due to arsenic in sediment. We recommend no further ecological risk assessment in this area because the extent of potential exposure is limited.

• There is potential risk in Fort Pond Brook due to the detection of chiomium in surface water. We recommend additional surface water sampling to evaluate the presence of chromium, but no further ecological risk assessment for Fort Pond Brook.

• Sinking Pond exhibits a potential risk at several levels in the food web due to exposure to six metals (arsenic, cadmium, copper, iron, manganese, and lead), polynuclear aromatic hydrocarbons (PAHs), polychlorinated biphenyls (PCBs), and pesticides.

• North Lagoon Wetland exhibits a potential risk at several levels in the food web due to exposure to ten metals (aluminum, arsenic, cadmium, copper, iron, I ead, manganese, mercury, nickel, and zinc).

The Phase 2 Ecological Risk Assessment will address the potential risks in Sinking Pond and North Lagoon Wetland by collecting information on sediment/soil toxicity and site-specific information on food chain transfer of identified Compounds of Potential Concern (COPCs). The workplan also includes a plan for water quality monitoring in Fort Pond Brook.

2.0 SURFACE WATER SAMPLING AND ANALYSIS IN FORT POND BROOK

The Screening-Level Ecological Risk Assessment identified one sampling location, FPB-S01, in Fort Pond Brook where total chromium exceeded National Recommended Water Quality Criteria (NRWQC; USEPA, 1999) for total chromium and hexavalent chromium. This sampling station is upstream of the location where the North Lagoon Wetland meets Fort Pond Brook (FPB-T21). The total chromium concentration at FPB-T21 is much lower than at FPB-S01 and well below the NRWQC. Because this exceedance of criteria occurred at one location and was not detected 100 feet farther downstream, we recommend additional sampling to evaluate this condition in

Fort Pond Brook. We recommend no further ecological risk assessment for Fort Pond Brook at this time.

2.1 Data Collection and Analysis

Surface water samples will be collected upstream at location FPB-S02, at FPB-S01, and downstream at FPB-T21 during low flow conditions and immediately after a heavy rainfall to evaluate whether this condition is persistent in Fort Pond Brook. Samples wil I be analyzed for dissolved total chromium, hexavalent chromium, and hardness.

3.0 ECOLOGICAL RISK ASSESSMENT WORKPLAN

3.1 Goals and Objectives

This section describes the Phase 2 ecological risk assessment workplan for the W.R. Grace Site in Acton, Massachusetts. The ecological risk assessment will be conducted according to the following guidance:

U.S. Environmental Protection Agency. 1998. Guidelines for Ecological Risk Assessment. EPA/630/R-95/002F. Risk Assessment Forum. Washington, DC.

U.S. Environmental Protection Agency. 1997. Ecological Risk Assessment Guidance for Superfund, Process for Designing and Conducting Ecological Risk Assessments. EPA/540/R-97/006. Office of Solid Waste and Emergency Response. Washington, DC.

U.S. Environmental Protection Agency. 1993. Wildlife Exposure Factors Handbook Volume I. EPA/600/R-93/187a. Office of Research and Development Washington, DC.

Consistent with this guidance, the ecological risk assessment will include:

• Description of a Site Conceptual Model; • Identification of Contaminants of Potential Concern (COPCs); • Selection of Assessment Endpoints; • Selection of Receptors • Selection of Measurement Endpoints and their relation to Assessment Endpoints; • Risk characterization; and • Discussion of uncertainties and assumptions.

Details on the analytical and laboratory procedures, as well as on data validation techniques are described in the Quality Assurance Project Plan (QAPP) for the site in the Project Operations Plan (Revised), Operable Unit Three, W.R.Grace Superfund Site, Acton, Massachusetts (HSI GeoTrans, Inc., 2000). The QAPP describes the data analysis methods and data quality objectives (DQOs).

3.2 Site Conceptual Model

The foundation of an ecological risk assessment is the site conceptual model. According to USEPA guidance, the conceptual model addresses:

• environmental setting and COPCs known or suspected to exist at the site; • COPC fate and transport mechanisms; • mechanisms of ecotoxicity and likely categories of potentially affected receptors; • complete exposure pathways.

A complete exposure pathway occurs whenever there is a source of contamination, a fate and transport mechanism, which delivers a COPC to a receptor, and an exposure route, which results in uptake of the COPC by the receptor. The Site Conceptual Model (Figure 3-1) was presented in the Screening-Level Ecological Risk Assessment.

3.2.1 Environmental Setting and COPCs Known or Suspected to Exist at the Site

The screening-level ecological risk assessment identified the COPCs for Sinking Pond as:

Arsenic, cadmium, copper, iron, lead, manganese, PAHs, PCBs, and pesticides.

For North Lagoon Wetland, the COPCs are:

Aluminum, arsenic, cadmium, copper, iron, lead, manganese, mercury, nickel, and zinc.

The fate and transport mechanisms, and potentially affected receptors for these COPCs were discussed in the Screening-Level Ecological Risk Assessment. The Phase 2 ecological risk assessment will provide more information where appropriate.

3.2.2 Likely Categories of Potentially Affected Receptors

The categories of potentially affected receptors for Sinking Pond include:

• the benthic macroinvertebrate community; • fish; • turtles; • omnivorous mammals (e.g., muskrat).

The categories of potentially affected receptors for North Lagoon Wetland include:

• the soil/sediment invertebrate community; and • omnivorous mammals (e.g., muskrat).

3.2.3 Compl etc Exposure Pathways

The USEPA guidance indicates that the risk assessment should identify complete exposure pathways so that the assessment can focus on those COPCs that can reach ecological receptors. The likely complete exposure pathways in Sinking Pond are:

• sediment to fish and benthic invertebrates through direct uptake and ingestion; • sediment and surface water to aquatic plants through direct uptake; • surface water to invertebrates and fish through direct contact and ingestion; and • sediment and surface water via food chain pathways to higher organisms (e.g., turtles and

mammals) through ingestion.

The likely complete exposure pathways in North Lagoon Wetland are:

• Sediment/soil to soil invertebrates; • Sediment/soil via food chain pathways to higher organisms (mammals).

3.3 Identification of Receptors, Assessment Endpoints, and Measurement Endpoints for the Ecological Risk Assessment

3.3.1 Receptors

This section identifies species of ecological receptors and provides the rationale for their selection as representative of the species that occur or are likely to occur at the site. The Screening-Level Ecological Risk Assessment identified receptors and provided a brief description of their habitat requirements and feeding strategies.

3.3.1.1 Benthic or Soil Invertebrates

Benthic or soil invertebrates are potential receptor species in Sinking Pond and North Lagoon Wetland because they:

• are relatively immobile and have substantial exposure to sediments/soils; and • provide food for fish and wildlife;

3.3.1.2 Fish

Fish are potential receptor species in Sinking Pond because they:

• are resident in the pond; and • can be exposed to contaminated sediments and surface waters;

• can be exposed through consumption of contaminated prey items, such as benthic invertebrates.

3.3.1.3 Turtles

Turtles are potential receptor species in Sinking Pond because they:

• are resident in the pond; • can be exposed to contaminated sediments and surface waters; and • can be exposed through consumption of contaminated prey items, such as benthic

invertebrates and fish.

3.3.1.4 Semi-Aquatic Mammals

Mammals, such as muskrat, that feed on aquatic species are potential receptors in Sinking Pond and North Lagoon Wetland because they:

• can be exposed through incidental ingestion of contaminated water and sediment; and • can be exposed through ingestion of contaminated prey, such as invertebrates or plants.

3.3.2 Selection of Assessment Endpoints

Assessment endpoints are expressions of the environmental value to be protected at a site. The selection of assessment endpoints requires the consensus of the regulators, the regulated community, and state or local concerns. This work plan proposes the following assessment endpoints for the potentially affected aquatic receptors and their habitats in Sinking Pond:

• Sustainability (survival, growth and reproduction) of a benthic invertebrate community that can serve as prey items for fish;

• Sustainability (survival, growth, and reproduction) of a fish population; • Sustainability (survival, growth, and reproduction) of local populations of turtles; and • Sustainability (survival, growth, and reproduction) of local populations of omnivorous

mammals.

This work plan proposes the following assessment endpoints for the potentially affected aquatic receptors and their habitats in North Lagoon Wetland:

• Sustainability (survival, growth and reproduction) of an invertebrate community; and • Sustainability (survival, growth, and reproduction) of local populations of semi-aquatic

mammals (muskrat).

3.3.3 Selection of Measurement Endpoints

When assessment endpoints are not directly measurable, risk assessments examine measures of effects. Measurement endpoints are measurable characteristics that reflect the assessment endpoint (USEPA, 1997). In a weight-of-evidence approach (Menzie et al., 1996), each measurement endpoint is weighed qualitatively by considering:

• Strength of association between the measurement endpoint and the assessment endpoint; • Data quality; and • Study design and execution.

Strength of association refers to how well a measurement endpoint represents an assessment endpoint. The greater the strength of association between the measurement and assessment endpoint, the greater the weight given to that measurement endpoint in the risk analysis.

The weight given a measurement endpoint also depends on the quality of the data as well as the overall study design and execution. A summary of assessment endpoints and associated measures of effects is provided in Table 1.

Measurement Endpoints for Sinking Pond Assessment Endpoint SP1 and North Lagoon Wetland Assessment Endpoint NLW1: Sustainability of an invertebrate community

Measurement Endpoint SP la and NLW la: Sediment toxicity tests in comparison to reference areas

Rationale: Sediment toxicity tests provide a direct measure of adverse effects to benthic invertebrates. Sediment toxicity tests provide information about the integrated effect of exposure to the mixture of COPCs in sediment. Information on the toxicity of the mixture of COPCs is an important addition to information on the potential toxicity of individual compounds.

Approach: Sediment bioassays conducted in the laboratory will be used to evaluate the potential effects of whole sediment on representative benthic macroinvertebrates. Specifically, the assessment will use an acute and chronic bioassay with the midge larvae Chironomus tentans (EPA Method 100.2 and 100.5; USEPA, 2000). The toxicity of the sediment will be compared to that of the standard control sediment used by the laboratory as part of the standard operating procedure, as well as to sediment from the reference locations. Statistically significant decreases in survival, reproduction, and growth of organisms exposed to sediments or soil from Sinking Pond or North Lagoon Wetland relative to controls and reference locations may be considered a COPC-related effect. However, effects due to factors that are not related to the concentration of COPCs, such as sediment grain size, organic carbon content, and concentrations of ammonia, must also be considered.

Data collection and analysis - Sinking Pond: Three sediment samples (from depths of 0 to 2 inches) will be collected from Sinking Pond and one sample will be collected from the inlet to Sinking Pond. Approximate sample locations are near SP-S02 in the inlet, near SP-S03 at the

mouth of the inlet, and two other locations in Sinking Pond (Figure 1-2). Three sediment samples will also be collected from the southern end of White Pond that has organic sediments similar to Sinking Pond. Samples will be collected according to the FSP and QAPP. Sufficient sample volume will be collected for the toxicity test and chemical analyses. Samples will be homogenized before they are divided into separate containers for toxicity testing and chemical analysis.

Data collection andanalysis - North Lagoon Wetland:

Six soil/sediment samples from depths of 0 to 2 inches will be collected from North Lagoon Wetland according to the FSP and QAPP. Sample locations will be distributed along the length of the area called the North Lagoon Wetland. Approximate locations are near NLW-S01 and NLW-S02 in the grassy area north of the former North Lagoon, near NLW-S05 in the swale leading from the grassy area, and near NLW-S07, NLW-S08, and NLW-S09 in the riparian wetland south of Fort Pond Brook. Three samples will also be collected from a reference wetland area. The wildlife survey performed for the Screening-Level Ecological Risk Assessment identified a wooded riparian wetland along the Assabet River upstream of the site as a reference area for the North Lagoon Wetland. This area is south of Route 62 on the east side of the Assabet River downstream from sample location ASBRV-UP6 on Figure 1-2. Sufficient sample volume will be collected for the toxicity tests and chemical analyses for aluminum, arsenic, cadmium, copper, iron, lead, manganese, mercury, nickel, and zinc. Samples will be homogenized before they are divided into separate containers for toxicity testing and chemical analysis.

Measurement Endpoints for Assessment Endpoint SP2for Sinking Pond: Sustainability of the fish population of Sinking Pond

Measurement Endpoint SP 2a: Concentrations of COPCs in surface waters

Rationale: Accumulation of COPCs from surface water via the gills may possibly have an adverse effect on the survival, growth, and reproduction of fish that inhabit Sinking Pond. The screening-level ecological risk assessment indicated that cadmium and lead sxceeded the chronic National Recommended Water Quality Criterion in Sinking Pond during early spring sampling. Therefore, additional measurement will be made to evaluate whether this is a persistent condition.

Approach: This measurement endpoint will be evaluated by comparing measured concentrations of dissolved cadmium and dissolved lead in Sinking Pond surface waters to NRWQC. The criteria will be adjusted for the measured water hardness of Sinking Pond.

Data Collection and Analysis: Samples will be collected from the inlet and the center of the pond on four separate dates. At least one sampling round will occur after the fall overturn. Samples collected from the center of the pond while it is stratified will be collected from the epilimnion and hypolimnion. When the pond is not stratified, the center samples will be collected at mid-depth. Water levels in the inlet are shallow (less than 2 feet), so the inlet sample

will be collected at mid-depth for each sampling round. Samples will be analyzed for dissolved cadmium, lead, and hardness. Field sampling will be performed according to trie FSP. Sample handling and chemical analysis will be performed according to the QAPP.

Measurement Endpoint SP 2b: Body burdens of COPCs in fish

Rationale: Fish exposed to chemicals in their diets or in water can accumulate these chemicals in their tissues. Such accumulation may result in adverse effects on the survival growth and reproduction of the fish. Concentrations of COPCs in tissue offish that inhabit Sinking Pond will be compared to concentrations at a reference site (White Pond in Concord, MA) to assess the degree of exposure offish to COPCs in Sinking Pond. Concentrations of COPCs will also be compared to toxicity benchmarks as an indication of the potential for adverse effects on Sinking Pond fish due to exposure to COPCs.

Approach: Concentrations of arsenic, cadmium, copper, lead, manganese, and PCBs in whole forage fish from Sinking Pond will be compared to concentrations in fish collected from White Pond. Fish lipid content will also be measured. Concentrations of arsenic, cadmium, copper, lead, manganese, and PCBs in whole fish from Sinking Pond will also be compared to relevant toxicity benchmarks that are based on measured body burdens. The U.S. Army Corps of Engineers' Environmental Residue Effects Database (USAGE, 1998) will be used as a source of toxicity benchmarks that are based on tissue concentrations. Concentrations of arsenic, cadmium, copper, lead, manganese, and PCBs in fish will also be used in food chain models as described in the Screening-Level Ecological Risk Assessment. The models used previously will be modified to employ actual measured concentrations in food items and appropriate data far area use and migration.

Data Collection and Analysis: Three composite fish samples will be collected from Sinking Pond and White Pond. The species will be selected in the field based on species present in Sinking Pond. Collection methods may include gill netting, electroshocking, or seining. Sufficient fish tissue will be composited to obtain enough mass for chemical analysis. Samples will be analyzed for arsenic, cadmium, copper, lead, manganese and PCBs.

Measurement Endpoints for Assessment Endpoint SP3 for Sinking Pond: Sustainability of local populations of turtles

Measurement Endpoint SP 3a: Accumulation of COPCs in benthic invertebrates

Rationale: Some animals, such as turtles may eat invertebrates as a portion of their diet. This measurement endpoint evaluates this potential route of exposure.

Approach: Invertebrates of a sufficient size to be easily collectable for body burden analysis (such as freshwater mussels in Sinking Pond) are not expected to be present. To evaluate uptake into invertebrates, accumulation will be measured in invertebrates in the laboratory. For Sinking Pond, a 28-day bioaccumulation test will be conducted with the oligochaete v. orm, Lumbriculus

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variegatus (Method 100.3; USEPA, 2000). At the end of 28 days, the invertebrates will be analyzed for arsenic, cadmium, copper, lead, manganese, and PCBs. The concentrations measured in benthic invertebrates will be used in the multi-pathway exposure model for turtles that considers uptake of COPCs from sediment and food. These models were presented in the Screening Level Ecological Risk Assessment. Potential exposures to wildlife will be compared to: 1) appropriate No Observed Adverse Effects Levels (NOAELs) and Lowest Observed Adverse Effect Levels (LOAELs), and 2) potential exposures that occur in reference areas. Little information exists on toxicity of chemicals to turtles. A literature review of existing information will be included in this assessment; and toxicity reference values specific to l.urtles will be derived wherever possible.

Data Collection and Analysis: Data collection activities will be the same as those described above for Measurement Endpoint SPla.

Measurement Endpoint SP 3b: Concentration of COPCs in vegetation

Rationale: Some animals, such as turtles, may eat vegetation as a portion of their diet. This measurement endpoint evaluates this potential route of exposure.

Approach: To evaluate uptake into plants, concentrations of COPCs will be measured in three plant samples from Sinking Pond. Emergent vegetation is only present around the perimeter of Sinking Pond in a few locations. Samples will be collected of roots and leaves/stems, separately for a total of six samples. Three root samples and three leaf/stem samples will be collected from White Pond to compare this potential exposure with background. The species will be selected in the field based on its presence in Sinking Pond and potential use by wildlife

The concentrations measured in plants will be used in the multi-pathway exposure model for wildlife receptors that considers uptake of COPCs from sediment and food. These models were presented in the Screening Level Ecological Risk Assessment. Potential exposures of wildlife will be compared to: 1) appropriate NOAELs and LOAELs, and 2) potential exposures that occur in reference areas.

Data Collection and Analysis: Plant samples will be collected in mid-summer. Sinking Pond samples will be analyzed for arsenic, cadmium, copper, lead, manganese, and PCBs.

Measurement Endpoint SP 3c: Concentration of COPCs in fish

Rationale: Some wildlife species such as the turtle eat fish. This measurement endpoint evaluates this potential route of exposure.

Approach: Whole forage fish such as minnows or sunfish will be collected from Sinking Pond and analyzed for COPCs as described in Measurement Endpoint SP 2b. The: COPC concentrations measured in fish will be used in the multi-pathway exposure model for the turtle. The screening-level ecological risk assessment presented the details of the exposure models.

Potential exposure to receptor species will be compared to: appropriate NOAELs and LOAELs, and 2) potential exposures that occur in reference areas.

Data Collection and Analysis: Data collection activities were described under Measurement Endpoint SP 2b.

Measurement Endpointsfor Assessment Endpoint SP4for Sinking Pond and NL W2for North Lagoon Wetland: Sustainability of local populations of wildlife

Measurement Endpoint SP 4a and NLW 2a: Accumulation of COPCs in benthic or soil invertebrates

Rationale: Some animals, such as muskrat may eat invertebrates as a portion of their diet. This measurement endpoint evaluates this potential route of exposure.

Approach: Invertebrates of a sufficient size to be easily collectable for body burden analysis (such as freshwater mussels in Sinking Pond or earthworms in North Lagoon Wetland) are not expected to be present. The approach for Sinking Pond was described in Measurement Endpoint SP3a. Because the substrate in North Lagoon Wetland is soil, rather than sediment, a 28-day bioaccumulation test will be conducted with the earthworm Eisenia foetida (ASTM El676 Method A3). At the end of 28 days, the earthworms will be analyzed for alumnum, arsenic, and manganese. The concentrations measured in benthic or soil invertebrates will be used in the multi-pathway exposure model for muskrat that considers uptake of COPCs from sediment and food. These models were presented in the Screening Level Ecological Risk Assessment. Potential exposures to wildlife will be compared to: 1) appropriate No Observed Adverse Effects Levels (NOAELs) and Lowest Observed Adverse Effect Levels (LOAELs), arid 2) potential exposures that occur in reference areas.

Data Collection and Analysis: Data collection activities for Sinking Pond will be the same as those described above for Measurement Endpoint SPla and NLW la.

Measurement Endpoint SP 4b and NLW 2b: Concentration of COPCs in vegetation

Rationale: Some animals, such as muskrat, may eat vegetation as a portion of their diet. This measurement endpoint evaluates this potential route of exposure.

Approach: The approach for Sinking Pond was discussed previously in Measurement Endpoint SP3b. To evaluate uptake into plants in North Lagoon Wetland, concentrations of COPCs will be measured in six plant samples from North Lagoon Wetland and three plan! samples will be collected from the reference area upstream along the Assabet River. Approximate locations were discussed in Measurement Endpoint NLW la. Samples will be collected of aboveground plant matter. The species will be selected in the field based on its presence in the North Lagoon Wetland and potential use by wildlife.

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The concentrations measured in plants will be used in the multi-pathway exposure model for wildlife receptors that considers uptake of COPCs from sediment and food. These models were presented in the Screening Level Ecological Risk Assessment. Potential exposures of wildlife will be compared to: 1) appropriate NOAELs and LOAELs, and 2) potential exposures that occur in reference areas.

Data Collection and Analysis: Plant samples will be collected in mid-summer. Data collection and analysis for Sinking Pond was discussed above for Measurement Endpoi nt SP3b. North Lagoon Wetland samples will be analyzed for aluminum, arsenic, and manganese.

3.4 Risk Characterization for the Ecological Risk Assessment

Risk results will be presented as calculated Hazard Quotients as well as other measures (e.g., presence of toxicity). These results will be incorporated into the weight of evidence approach (Menzie et al., 1996) in the form of graphs and tables and will be explained in narratives. The results will be used to refine estimates of potential risk identified in the Screening-Level Ecological Risk Assessment. For example, for benthic invertebrates, the screening-level assessment identified potential risk if a COPC exceeded a sediment benchmark level. The Phase 2 ecological risk assessment will measure actual toxicity to a benthic invertebrate. For wildlife species, food chain modeling will employ actual measured concentrations of COPCs in food items rather than conservative values estimated from the literature.

3.4.1 Use of Hazard Quotients

Because the Hazard Quotient will be one of the more common methods used to express results, it is explained below. The method simply involves comparisons of exposure concentrations for COPCs to doses related to effects:

UOSC exposure

Hazard Quotient = Dose effects

where:

Dose exposure = the dose to which an organism is exposed

Dose effects = the dose at or above which effects may occur

If the Hazard Quotient exceeds "1", there is a potential for an effect. To some extent, the higher the number above "1", the more likely that an effect would occur. Calculations of Hazard Quotients need to take into account spatial and temporal factors inasmuch as these are related to the effect that might occur to populations of biota.

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3.5 Discussion of Uncertainties and Exposure Assumptions

Sources of uncertainty and variability within the ecological risk assessment will be identified. The impact associated with these uncertainties will be qualitatively addressed. If appropriate, sensitivity analyses will be conducted for the important exposure parameters that are used in the wildlife exposure models and for the TRVs that are used to determine risk to the representative wildlife species.

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4.0 REFERENCES

HSI GeoTrans, Inc. 2000. Project Operations Plan (REVISED), Operable Unit Three, W.R. Grace Superfimd Site, Acton, Massachusetts, March 10, 2000.

Menzie, C.A.. M.H. Herming, J. Cura, K. Finkelstein, J. Gentile, J. Maughan, D. Mitchell, S. Petron, B. Potocki, S. Svirsky, P. Tyler. 1996. Special report of the Massachusetts Weight-of-Evidence Workgroup: A Weight-of-Evidence Approach for Evaluating Ecological Risks. Hum. Ecol. Risk Assess. 2: 277-304.

Sample, B.E., D. M. Opresko and G.W. Suter II, 1996, Toxicological benchmarks for wildlife: 1997 revision. Oak Ridge National Laboratory, Oak Ridge, Tennessee.

United States Army Corps of Engineers, 1998. [ URL: http://www.wes.army.mil/el/ered/index.html1

United States Environmental Protection Agency. 1993. Wildlife Exposure Factors Handbook Volume I. EPA/600/R-93/187a. Office of Research and Development. Washington, DC.

United States Environmental Protection Agency. 1997. Ecological Risk Assessment Guidance for Superfund, Process for Designing and Conducting Ecological Risk Assessments. EPA/540/R­97/006. Office of Solid Waste and Emergency Response. Washington, DC.

United States Environmental Protection Agency. 1998. Guidelines for Ecological Risk Assessment. EPA/630/R-95/002F. Risk Assessment Forum. Washington, DC.

United States Environmental Protection Agency. 1999. National Recommended Water Quality Criteria-Correction. Office of Water, Washington, DC. EPA-822-Z-99-001.

United States Environmental Protection Agency, 2000. Methods for Measuring the Toxicity and Bioaccumulation of Sediment-associated Contaminants with Freshwater Invertebrates, 2nd ed., Office of Research and Development, Office of Water, EPA/600/R-99/064.

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TABLES

Table 1 Assessment and Measurement Endpoints for

Phase 2 Ecological Risk Assessment W.R. Grace Site

Acton, Massachusetts

Assessment and Measurement Endpoints for Sinking Pond

Assessment Endpoint SP 1: Sustainability (survival, growth and reproduction) of a benthic invertebrate community (that can serve as prey items for fish).

Measurement Endpoint SP la: Measures of sediment toxicity in comparison to reference areas.

Assessment Endpoint SP 2: Sustainability (survival, growth, and reproduction) of a fish population.

Measurement Endpoint SP 2a: Concentrations of Contaminants of Potential Concern (COPCs) in surface water.

Measurement Endpoint SP 2b: Body burdens of COPCs in fish

Assessment Endpoint SP 3: Sustainability (survival, growth, and reproduction) of a local population of turtles.

Measurement Endpoint SP 3a: Accumulation of COPCs in benthic inveitebrates

Measurement Endpoint SP 3b: Concentrations of COPCs in vegetation

Measurement Endpoint SP 3c: Concentrations of COPCs in fish

Assessment Endpoint SP 4: Sustainability, growth, and reproduction) of local populations of omnivorous mammals

Measurement Endpoint SP 4a: Accumulation of COPCs in benthic invertebrates

Measurement Endpoint SP 4b: Concentrations of COPCs in vegetation

Assessment and Measurement Endpoints for North Lagoon Wetland

Assessment Endpoint NLW 1: Sustainability (survival, growth and reproduction) of a sediment/soil invertebrate community

Measurement Endpoint NLW la: Measures of sediment/soil toxicity in comparison to reference areas.

Assessment Endpoint NLW 2: Sustain ability, growth, and reproduction) of local populations of omnivorous mammals

Measurement Endpoint NLW 2a: Accumulation of COPCs in sediment/soil invertebrates

Measurement Endpoint NLW 2b: Concentrations of COPCs in vegetation

FIGURES

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MENZIE • CURA & ASSOCIATES, INC. One Courthouse Lane, Suite Two • Chelmsford, Massachusetts 01824 • Phone 978/453-4300 Fax 978/453-7260