2017_Dec_21_Prime_Hook_EECA_Geosyntec__(1).pdf

Final Engineering Evaluation/Cost Analysis for Wetlands Adjacent to the Former Trap Range

Prime Hook National Wildlife Refuge Milton, Delaware December 2017

Contract Order Number: F16PX02621

Prepared for

U.S. Fish and Wildlife Service Chesapeake Bay Field Office 177 Admiral Cochrane Drive Annapolis, Maryland 21401

Prepared by Geosyntec Consultants, Inc.

321 SW Morrison Street Suite 600 Portland, Oregon, 97205

Reviewed by

KOMAN Government Solutions, LLC 180 Gordon Drive, Suite 110

Exton, PA 19341 http://www.google.com/url?sa=i&rct=j&q=&esrc=s&source=images&cd=&ved=0ahUKEwihkdbSzZ7QAhWB3YMKHYJMDYgQjRwIBw&url=http://www.coastalrefuges.org/page-1415194&psig=AFQjCNHTWWggr_dEJ9UGVK7Mm0JnHlLp8A&ust=1478881661616217

Final Engineering Evaluation/Cost Analysis Prime Hook National Wildlife Refuge

Contract Order Number:

F16PX02621 ES-1 December 2017

Executive Summary KOMAN Government Solutions, LLC (KGS) and Geosyntec Consultants, Inc. (Geosyntec) (the KGS Team) have prepared this Engineering Evaluation/Cost Analysis (EE/CA) for the U.S. Fish and Wildlife Service (Service) as part of the Non-Time Critical Removal Action (NTCRA) on a small portion of the Prime Hook National Wildlife Refuge (NWR) near Milton, Delaware. The Prime Hook Lead Shot Site (Site) is defined as the Refuge property bordering the former Broadkill Sportsman’s Club trap range. This EE/CA is focused on the forested area of the Refuge immediately adjacent to the upland area where an Interim Remedial Action was performed in 2002-2003.

The EE/CA was performed pursuant to the Service’s delegated response action authority under Section 104 of the Comprehensive Environmental Response, Compensation, and Liability Act (CERCLA) to characterize the nature and extent of contamination at the Site and evaluate removal action alternatives to protect public health, welfare, and the environment from risks associated with such contamination.

The Prime Hook NWR is located along Prime Hook Creek and the western shore of Delaware Bay in Sussex County, Delaware, approximately three miles northeast of the town of Milton. The 9,700-acre NWR was established in 1963 and consists of approximately 7,400 acres of freshwater and tidal marsh, 1,000 acres of timber and brush, and 1,300 acres of grassland and croplands.

The Broadkill Sportsman’s Club (the Club) was founded on adjacent land in 1962. The Club used five shooting ranges, each built behind a small (approximately 10 by 10 feet) concrete block bunker known as the trap house, which launched the clay targets into the air. Individual ranges had an arrangement of five angled concrete walkways behind the trap house, with shooting stations and distances marked on the walkways.

The Club was located in an upland area that acts as a drainage divide for two wooded wetlands containing unnamed tributaries of Prime Hook Creek. The highest land elevation at the axis of the upland is about 10 feet above mean sea level. Most of the land in the wooded wetland areas is 5 feet or less in elevation.

The trap-shooting range operated from 1962–1998 when a land trade with the Service was initiated by the Club. As part of the trade, the Service began a review of potential contamination of the site and, in 1998, the Service collected soil samples on Refuge property to determine the extent of lead shot deposition and lead concentrations in soil. Results indicated that the surface soil in the shooting trajectory contained elevated concentrations of lead and high numbers of lead shotgun pellets.

The objectives of this EE/CA are to characterize the nature and extent of contamination at the forested portion of the Site, evaluate cleanup alternatives based on the criteria set out in the National Oil and Hazardous Substances Pollution Contingency Plan (NCP) and Title 40 of the Code of Federal Regulations (CFR), Part 300, and to select a preferred alternative which will be available for public review and comment. This EE/CA was prepared in accordance with the requirements of CERCLA, the NCP, Guidance on Conducting Non-Time-Critical Removal Actions under CERCLA [U.S. Environmental Protection Agency (EPA)/540-R-93-057, August 1993]; and other documents which are cited therein.

F16PX02621 ES-2 December 2017

As part of the EE/CA, the KGS Team first completed a Supplemental Site Investigation (SSI) (Attachment 1) where additional soil, sediment, and surface water samples were collected and analyzed to define Remedial Action Areas (RAAs). The data were compared to the Service-generated preliminary remediation goals (PRGs) which were subsequently used to formulate removal action objectives (RAOs) for the EE/CA and to define the RAAs. Once the RAAs were identified, removal action alternatives were developed and comparatively analyzed for effectiveness, implementation ability, and costs to select a removal action approach.

Results of the 2017 Supplemental Site Investigation The SSI at the Site was completed in early 2017 to eliminate or reduce remaining data gaps regarding the nature and extent of contaminants in soil and sediment. The SSI confirmed that lead is the primary contaminant of potential concern (COPC) for the Site and that, in general, soil and sediment within the shot fall zone contain concentrations of lead above the PRGs. Several additional constituents were also detected in surface water; however, it is reasonable to assume that the removal or treatment of soil and sediment containing lead above the PRGs will be effective in reducing COPC concentrations in surface water. In addition, because COPCs detected in water samples are thought to originate from erosion of upland soil and sediment, the removal action described in this EE/CA focuses on soil and sediment.

Removal Action Areas RAAs were defined based on locations of the Site that contained lead concentrations above PRGs. As such, the removal footprint is subject to modification based on future additional data (if collected).

Summary of the Alternative Evaluation and Recommended Alternative Based on the results of the comparison of alternatives, Alternative 2 - excavation of soil with off-site disposal and Alternative 3 - excavation of soil with on-site treatment followed by off-site disposal were ranked the same during the evaluation process. Therefore, either alternative or some combination of the two were selected as the recommended removal action. The preferred alternative involves the mechanical excavation, potential on-site treatment of a portion of the excavated material to reduce toxicity, and disposal of the excavated material at an appropriate off-site facility. The completed excavations in the upland areas would be backfilled with clean borrow soil and the affected areas would be restored and replanted with native vegetation, providing for unrestricted future land use. The time to complete the removal action was estimated to be approximately three months and the estimated cost with contingency is approximately $3,370,000 to $3,990,000.

TABLE OF CONTENTS

Page

F16PX02621 ii December 2017

1. INTRODUCTION

1.1 Objectives

1.2 Report Organization

2. SITE CHARACTERIZATION AND HISTORY

2.1 Site Description and Background

2.2 Summary of Previous Investigations

2.2.1 Initial Service Response

2.2.2 Preliminary Assessment

2.2.3 2000 to 2001 Groundwater Investigation

2.2.4 Interim Remedial Action

2.2.5 2004 Ecological Risk Assessment

2.2.6 2007 to 2015 Groundwater and Surface Water Sampling

2.2.7 Amphibian Investigation

2.2.8 Development of Preliminary Remediation Goal

2.2.9 2017 Supplemental Site Investigation

3. SOURCE, NATURE, AND EXTENT OF IMPACTS

3.1 Extent of COPCs in Soil

3.2 Extent of COPCs in Sediment

3.3 Extent of COPCs in Surface Water

3.4 Extent of Impacts and Transport Mechanisms

4. IDENTIFICATION OF REMOVAL ACTION OBJECTIVES

4.1 Removal Action Objectives

4.2 Statutory Authority

4.3 Determination of Removal Action Scope

4.4 Removal Schedule

4.5 Planned Removal Action Activities

4.6 Applicable or Relevant and Appropriate Requirements

4.6.1 Chemical-Specific ARARs

4.6.2 Location-Specific ARARs

4.6.3 Action-Specific ARARs

5. IDENTIFICATION AND SCREENING OF REMOVAL ACTION ALTERNATIVES14

5.1 List of Potential Technologies

5.2 Screening of Unsuitable Removal Action Alternatives

5.3 Development of Removal Action Alternatives

5.3.1 Alternative 1 – No Action

5.3.2 Alternative 2 – Excavation with Off-Site Disposal

TABLE OF CONTENTS (Continued)

F16PX02621 iii December 2017

5.3.3 Alternative 3 – Excavation, Treatment, and Off-Site Disposal

5.3.4 Alternative 4 – Soil and Sediment Capping

5.3.5 Surface and Groundwater Remedy

6. COMPARATIVE ANALYSIS OF REMOVAL ACTION ALTERNATIVES

6.1 Effectiveness

6.1.1 Overall Protection of Human Health and the Environment

6.1.2 Compliance with ARARs

6.1.3 Short-Term Effectiveness

6.1.4 Reduction of Toxicity, Mobility, and Volume through Treatment

6.1.5 Long Term Effectiveness and Permanence

6.1.6 Implementability

6.1.7 Availability of Resources

6.1.8 Costs

6.1.9 Ranking of Alternatives

7. RECOMMENDED REMOVAL ACTION ALTERNATIVE

8. ADDITIONAL COST SCENARIOS

8.1 Breakdown of Alternatives 2 and 3 Costs by Area

8.2 Cost Scenarios for Alternative 2

9. REFERENCES

LIST OF FIGURES

Figure 1 Site Vicinity

Figure 2 Site Map

Figure 3 Shot Count Results

Figure 4 Removal Action Area Extent

Figure 5 Removal Action Area with Excavation Extents

Figure 6 Summary of Select Lead in Soil and Sediment Results

TABLE OF CONTENTS (Continued)

F16PX02621 iv December 2017

LIST OF TABLES

Table 1 Potential Chemical-Specific ARARs

Table 2 Potential Location-Specific ARARs

Table 3 Potential Action-Specific ARARS

Table 4 Alternative 2 - Excavation with Off-Site Disposal

Table 5 Alternative 3 - Excavation, Treatment, and Off-Site Disposal

Table 6 Alternative 4 - Soil and Sediment Capping

Table 7 Comparison of Alternatives

Table 8 Scoring of Alternatives

Table 9 Summary of Costs by Alternative and Area

Table 10 Alternative 2 - Excavation with Off-Site Disposal, Removal of Soil Within Areas 1, 2 and 4

Table 11 Alternative 2 - Excavation with Off-Site Disposal, Removal of 6-inches of Soil in Areas 1, 2 and 4

Table 12 Alternative 2 - Excavation with Off-Site Disposal, Removal of 6-inches of Soil in Areas with Visible Shot

LIST OF ATTACHMENTS

Attachment 1 Supplemental Site Investigation

F16PX02621 1 December 2017

1. INTRODUCTION

KOMAN Government Solutions, LLC (KGS) and Geosyntec Consultants, Inc. (Geosyntec) (the KGS Team) have prepared this Engineering Evaluation/Cost Analysis (EE/CA) for the U.S. Fish and Wildlife Service (the Service) as part of the Non-Time Critical Removal Action (NTCRA) on Service property near the Former Trap Range on the Prime Hook National Wildlife Refuge (NWR or the Refuge). The Site location is shown on Figure 1, and the Site layout is shown on Figure 2.

In accordance with Section 300.415 of the National Oil and Hazardous Substances Pollution Contingency Plan (NCP), 40 Code of Federal Regulations (CFR) Part 300; the Service is performing this EE/CA through its contractor, KGS, under Contract Order Number F16PX02621. The Service has the authority to undertake Comprehensive Environmental Response, Compensation, and Liability Act (CERCLA) response actions under 42 United States Code (USC) Section 9604, which has been delegated to the Service by Executive Order 12580, as amended by Executive Order 13016, and Departmental Manual, Chapter 7, Part 207.

CERCLA and the NCP authorize two types of responses to releases of hazardous substances into the environment: remedial and removal actions. Remedial actions involve the study, design, and construction of long-term actions directed toward permanent remedy. In contrast, removal actions are usually short-term actions typically taken within hours, weeks, or months to “abate, prevent, minimize, stabilize, mitigate, or eliminate the release or threat of release” of hazardous substances [40 CFR 300.415(b)]. This EE/CA pertains to the NTCRA, which allows for a response to releases where a planning period of at least six months is available before on-site activities must begin and the need is less immediate. NTCRAs generally attempt to control the source of contamination and are sometimes followed by a remedial action to complete site response. However, NTCRAs may be used to remediate a site completely.

As part of the EE/CA, the KGS Team completed a Supplemental Site Investigation (SSI) (Attachment 1). Additional soil, sediment, and surface samples were collected and analyzed during this limited investigation to better define removal action areas (RAAs). Finally, the data was compared to the Service-generated preliminary remediation goals (PRGs) which were subsequently used to formulate removal action objectives (RAOs) for the EE/CA. This EE/CA was prepared in accordance with the requirements of CERCLA, the NCP, Guidance on Conducting Non-Time-Critical Removal Actions under CERCLA [Environmental Protection Agency (EPA)/540-R-93-057, August 1993]; and other documents which are cited therein.

1.1 Objectives

The objectives of this EE/CA are to 1) characterize the nature and extent of contamination exceeding PRGs; 2) evaluate risks to human health and the environment; 3) identify the goals of a removal action, 4) evaluate potential removal action alternatives and 5) recommend a removal action alternative that is protective of human health and the environment and complies with applicable or relevant and appropriate requirements (ARARs).

To meet these objectives, the following items were completed.

• Compiled site data and conducted a data gap analysis.

• Completed an SSI to fill identified data gaps.

• Prepared this EE/CA document, which provides the following information:

F16PX02621 2 December 2017 o A list of proven technologies and process options that address RAOs identified for the Site;

o A screening of the technologies and process options according to effectiveness and implementability;

o A listing of the retained technologies and process options and an assessment of the most feasible removal actions; and o A detailed comparative analysis of each alternative.

The Service will use the above objectives together with this EE/CA and documents in the administrative record to select an appropriate NTCRA. A public comment period will follow publication of the EE/CA. After responding to public comments on the EE/CA, the Service will formally document the selected remedy in an Action Memorandum.

1.2 Report Organization

This EE/CA report consists of nine sections:

• Executive Summary - presents a concise summary of this EE/CA.

• Section 1: Introduction - describes the framework for this EE/CA and states the objectives and scope.

• Section 2: Site Characterization and History - presents background information and setting for the Site, including a summary of its development history, location, geology, hydrogeology, and ecosystems. Previous site investigations and results are also summarized in this section.

• Section 3: Source, Nature, and Extent of Impacts - describes the source, nature, and extent of contamination from historic site uses and site data.

• Section 4: Identification of RAOs - identifies RAOs and presents chemical-, location-, and action-specific ARARs.

• Section 5: Identification and Screening of Removal Action Alternatives - describes general response actions that address RAOs, identifies and screens removal action technologies and process options, and introduces the identification and more detailed screening of removal action alternatives. Provides a detailed discussion of the applicable alternatives for the Site.

• Section 6: Comparative Analysis of Removal Action Alternatives - presents a detailed comparison and analysis of the potential removal actions remaining after the screening process.

• Section 7: Recommended Removal Action Alternative - describes the recommended removal action alternative and a summary of the recommendations.

• Section 8: References - provides references used for preparation of this document.

F16PX02621 3 December 2017

2. SITE CHARACTERIZATION AND HISTORY

2.1 Site Description and Background

The Prime Hook NWR is located along Prime Hook Creek and the western shore of Delaware Bay in Sussex County, Delaware, approximately three miles northeast of the town of Milton. The 9,700-acre Refuge was established in 1963 and consists of approximately 7,400 acres of freshwater and tidal marsh, 1,000 acres of timber and brush, and 1,300 acres of grassland and croplands.

The Broadkill Sportsman’s Club (the Club) was founded on adjacent land in 1962 and operated a trap shooting range on the property until 1998. The Club used five shooting stations, each built behind a small (approximately 10 by 10 feet) concrete block bunker known as the trap house, which launched the clay targets into the air. Individual stations had an arrangement of five angled concrete walkways behind each trap house, with shooting stations and distances marked on the walkways.

The Club was located in an upland area that acts as a drainage divide for two wooded wetlands containing unnamed tributaries of Prime Hook Creek. The highest land elevation on the axis of the upland is about 10 feet above sea level; most of the land in the wooded wetland areas is 5 feet or less in elevation. Prime Hook Creek is freshwater through this area and with levels controlled by a downstream dam. The Broadkill River is tidal through the Refuge, but Prime Hook Creek behind the flow-control structure (the dam) is not (Harding ESE, 2001).

The portion of Prime Hook NWR bordering the Club downrange from the trap-shooting area consists of a forested wetland along a small, unnamed tributary or slough to Prime Hook Creek, shown in Figure 2 as the wooded areas to the north and east of the former Club. The slough consists of a series of small, shallow ponds or pools, a few to possibly a dozen feet wide and only a few feet deep, separated by saturated hummocks of mud, fallen trees, and organic matter.

The water drains slowly to Prime Hook Creek. The size and shape of the slough varies greatly with the seasonal rise and fall of the water table, and it dries up completely on occasion. The slough is heavily forested, and is not used much by migratory fowl, which prefer open water.

There are numerous small mammals, birds, amphibians, and insects that are common in and around the slough.

2.2 Summary of Previous Investigations

The trap-shooting range operated from 1962–1998 when a proposed land trade with the Service was initiated by the Club. As part of the proposed trade, the Service began a review of potential contamination of the site and, in 1998, the Service collected soil samples to determine the extent of lead shot deposition and lead concentrations in soil. Results indicated that the surface soil in the shooting trajectory contained elevated concentrations of lead and high numbers of lead shotgun pellets. The Service ordered the Club to discontinue shooting onto the Refuge property and in 2000 funded the first year of a proposed 3-year Refuge cleanup project to delineate the magnitude and extent of soil contamination. The SSI Report (Attachment 1) contains tables and figures that summarize the historical sampling results from that investigation.

F16PX02621 4 December 2017

2.2.1 Initial Service Response

A synthetic geotextile cover was placed over the highest concentrations of lead pellets in July 2000, with the intention of preventing waterfowl and other birds from ingesting the pellets. The textile material was initially anchored in place using 18-inch steel spikes. Following deployment, it was determined that placing numerous 6-inch concrete blocks on top of the cover would help it to resist wind damage.

2.2.2 Preliminary Assessment

A Preliminary Assessment (PA), completed in 2001, concluded that lead shotgun pellets from the trap shooting range had accumulated on Refuge property in an area of about 22 acres downrange from the Club (Harding ESE, 2001). The highest density of pellets on the Refuge was concentrated in a zone of approximately 26,200 square feet (0.6 acre) immediately adjacent to the Club property and directly downrange from the trap houses. As many as 57,868 lead pellets per square foot were counted in the center of this high-density area, which is referred to as the “drop zone” in previous reports.

2.2.3 2000 to 2001 Groundwater Investigation In 2000 and 2001, shallow groundwater was monitored in wells installed in the upland, and in upgradient and downgradient locations within the forested wetland (Soeder and Miller, 2003).

Results from two sampling rounds at 19 shallow wells indicated that elevated levels of dissolved lead were present in groundwater at the site. It was concluded that lead and associated metals, such as antimony and arsenic (common small arms constituents), were being transported in shallow groundwater towards the slough in the forested wetland adjacent to the downrange target area.

Groundwater samples from wells located along the bank of the slough contained dissolved lead concentrations higher than 400 micrograms per liter (µg/L) and as high as 1 milligram per liter (mg/L). In contrast, the background concentration of lead in groundwater from an upgradient well was on the order of 1 µg/L. Two water samples collected directly from the slough, several months apart and downgradient of the shooting range, contained 24 and 212 µg/L of lead, respectively.

The report concluded that lead from a concentrated deposit of shotgun pellets on the Refuge has been mobilized through a combination of acidic water conditions and a very sandy, shallow, unconfined aquifer, and is moving along groundwater flow-paths toward the surface water drainage.

2.2.4 Interim Remedial Action

As an interim remedial action, the Service determined that soil from the membrane-covered area should be removed immediately. In 2002-2003, the geotextile was removed, and the top eight inches of soil and lead shot were excavated and transported off-site for disposal. The underlying 8-inch layer of soil was stabilized through the addition of Portland cement, and the area was backfilled with clean soil and re-seeded with a mixture of grasses (Shaw Environmental & Infrastructure, 2003).

Because of funding constraints, the cleanup was restricted to the upland area and a decision was made to monitor the wetland area.

F16PX02621 5 December 2017

2.2.5 2004 Ecological Risk Assessment In 2004, the Service completed an ecological risk assessment (ERA) for the site (Guy, et al, 2004). The ERA was intended to evaluate the potential threats to ecological receptors from direct exposure to lead contaminated soil and sediment as well, as from ingestion of lead shot. Toxicity tests, food chain accumulation models, and lead shot ingestion probability models were used to evaluate the risk to receptors that use the Site.

In toxicity tests, earthworms had reduced survival and rye grass had reduced growth when exposed to lead contaminated soil. The hazard quotients (HQ) calculated with food chain accumulation models for insectivorous birds and mammals exceed 1 (using a maximum soil concentration compared to a lowest-observable-adverse-effect-level (LOAEL). The results of the probability models indicated that waterfowl and terrestrial birds were at risk because of the ingestion of lead shot.

Based on the results of the studies, preliminary remediation goals (PRGs) were developed for the cleanup of lead contaminated soil, sediment, and lead shot. Because this site may be dry for long periods of time, the PRGs were developed to be protective of all species, without designating separate soil or sediment cleanup values. A comparison of the LOAELs calculated for the toxicity tests and the food chain accumulation models indicated that 421 milligrams per kilogram (mg/kg) lead was the lowest LOAEL. A comparison of the no-observed-adverse-effect-levels (NOAELs) calculated for the toxicity tests and food chain models indicated that 310 mg/kg was the highest NOAEL that was still less than the lowest LOAEL. Therefore, the targeted PRG for soil and sediment should be within the range of these values (310 - 421 mg/kg lead) to be protective of the endpoints evaluated in this risk assessment. By accepting an ingestion probability of 0.10, a PRG for lead shot was established at between 7 and 9 lead shot per cubic foot for the protection of waterfowl and upland birds.

2.2.6 2007 to 2015 Groundwater and Surface Water Sampling In 2007, the Service began a monitoring program to assess lead concentrations in groundwater and surface water at the Site, and the potential for bioaccumulation and adverse effects in amphibians. As part of the program, it was determined that from 2007 through 2015 there were infrequent detections of dissolved lead (at approximately 5 to 10 µg/L) in upland wells and no detections in upgradient and downgradient wells in the wetland (Pinkney and Callahan, 2014).

However, surface water in the unnamed tributary had lead concentrations that exceed the chronic state ambient water quality standard (0.93 µg/L) as adjusted for water hardness of 40 mg/L calcium carbonate (CaCO3). For example, during the December 2015 sampling event, dissolved lead concentrations in the tributary ranged from 5.3 to 10,400 µg/L (Pinkney and Callahan, 2017).

2.2.7 Amphibian Investigation

As part of the amphibian investigation, the wetlands were surveyed and adult green frogs (Lithobates clamitans), southern leopard frogs (L. sphenocephalus), bullfrogs (L. catesbeianus), Northern cricket frogs (Acris crepitans), and Fowler’s toads (Anaxyrus fowleri) were observed in the wetlands, but tadpoles and/or egg masses were not observed (Sparling et al., 2006).

A laboratory sediment toxicity study was completed using southern leopard frog tadpoles.

Sediment collected from a reference location on the Refuge with a lead concentration of 45 mg/kg dry weight were spiked with reagent grade lead (II) acetate to create lead concentrations

F16PX02621 6 December 2017 of 75, 180, 540, 2,360, 3,940, 5,520, and 7,580 mg/kg. Tadpoles were exposed beginning at Gosner (1960) stage 26 (early limb bud) through metamorphosis. Tadpoles exposed to concentrations of lead greater than 3,940 mg/kg died within two to five days, with a lead LC50 calculated as 3,728 mg/kg. All tadpoles exposed to lead concentrations greater than 2,360 mg/kg displayed severe spinal problems, reduced femur and humerus lengths, and deformed digits. It was reported that tissue residues (body minus liver) increased with sediment concentration, but only the tadpoles exposed to concentrations of lead greater than 2,360 mg/kg were statistically elevated above all other groups including the control.

2.2.8 Development of Preliminary Remediation Goal

The Service (Krest et al., 2017) conducted an additional amphibian study to determine whether toxic effects and bioaccumulation of lead would occur under natural conditions in the wetland and if the results could be used along with literature and guidance to develop an updated PRG for possible sediment cleanup based on risk to amphibians. The studies were conducted before the upland remediation (spring 2002), and afterwards in 2004, 2005, and 2011. The specific objectives of these studies were to determine whether: 1) lead was accumulating in the caged tadpoles; 2) lead was adversely affecting the frogs by inhibiting δ-aminolevulinic acid dehydratase (ALAD) activity; and 3) to compare residue and ALAD results before and after the upland cleanup. ALAD is used as a sensitive biomarker of lead exposure and response in mammals, birds, fish, and amphibians.

The three- to eight-week tests were conducted in the wetlands at a “Hot Spot” with an average sediment lead concentration of 4,457 mg/kg, and at a “Warm Spot” (initially 207 mg/kg in 2002) that was subsequently moved (because of low water) to a location with lead concentrations ranging from 13.4 to 75.1 mg/kg. Tests were also conducted at a reference location (Fred’s Pond) where sediment lead concentrations ranged from 35.7 to 91.1 mg/kg.

In each year, there were statistically significant differences in mean lead concentrations in all three groups of tadpoles. At the Hot Spot, there was a greater than 50 percent (%) decrease in the mean (± one standard deviation) lead concentration in tadpoles exposed in 2002 (57.0±21.1 mg/kg) compared with the post clean-up years (2004: 17.4±6.1 mg/kg; 2005: 27.7±11.0 mg/kg;

2011: 28.0±15.3 mg/kg). In year to year comparisons, both the Hot Spot and the Warm Spot tadpoles had significantly higher ALAD activity in 2004, 2005, and 2011 than in 2002. The Hot Spot tadpoles also had significantly higher ALAD activity in 2011 compared with those from 2005. Relative to Fred’s Pond, the percent reduction at the Hot Spot was 91% in 2002, 54% in 2004, 66% in 2005, and 16% in 2011. There was a significant negative linear correlation between ALAD activity and the natural log of lead concentrations in the tadpoles, but the relationship was weak (r = -0.53).

Bioaccumulation of lead and ALAD inhibition occurred at the Hot Spot where the Service calculated an average sediment concentration of 4,457 mg/kg dry weight. The inconsistent sediment concentrations at the Warm Spot precluded the use of those results in developing a PRG. Based on the laboratory study (Sparling et al., 2006) and EPA guidance, the Service proposed a 312 mg/kg lead as a PRG for sediment in wetland locations where amphibians breed to reduce the risk of serious malformations. The 312 mg/kg concentration closely matches the 310 mg/kg that was identified as the highest NOAEL in the 2004 study. A copy of the tadpole enclosure study detailing the PRG is included in the SSI (Attachment 1).

F16PX02621 7 December 2017

2.2.9 2017 Supplemental Site Investigation In 2017, an SSI was completed at the Site to reduce remaining data gaps regarding the nature and extent of contaminants in soil and sediment in the forested wetland portion of the Site. A copy of the SSI is included in Attachment 1. The SSI confirmed that lead was the primary COPC for the Site and that, in general, soil and sediment within the shot fall zone contain concentrations of lead above the PRGs. Other metals were also detected in soil and sediment samples; however, those constituents were only detected above applicable cleanup values in samples where lead was also above PRGs. Accordingly, lead concentrations can be used as an indicator compound for the delineation of soil containing any metals above their respective PRGs.

In addition, several COPCs were detected in surface water at concentrations that exceed State of Delaware cleanup values; however, it is reasonable to expect that the removal or treatment of soil and sediment containing lead above the PRGs will be effective in reducing COPC concentrations in surface water.

A review the data indicates that the extent of the lead contamination has been delineated to the PRGs, however, there is a potential that additional lead in soil or sediment exceeding the PRGs may be present along the northern portion of the 200D grid line, as one historical soil location (200D-250L) contained lead at 710 mg/kg. During the SSI, additional samples were not advanced near that location because of access limitations. It is likely that this area contains elevated lead concentrations since this area is down gradient of the general surface water flow from the Site. Accordingly, that area has been included in the preliminary remedial action area.

Figures 3, 4 and 5 in the SSI (Attachment 1) show the location of the historical sample locations for soil, sediment, and surface water samples in the forested wetland.

F16PX02621 8 December 2017

3. SOURCE, NATURE, AND EXTENT OF IMPACTS

This section summarizes the nature and extent of contamination at the Site based on the analytical results collected during previous investigations and the SSI. This discussion has been organized by media including soil, sediment, and surface water for clarity. During the completion of the SSI, the KGS Team compiled a dataset of historical analytical results. This dataset was reviewed and georeferenced, and the data used for subsequent risk evaluations. The nature and extent of contamination was identified through screening of the consolidated data set against applicable screening levels, as described below.

3.1 Extent of COPCs in Soil

Soil and sediment was screened against applicable PRGs that were established by the Service (see Section 2.2.8). Figure 14, Attachment 1 illustrates the boundary of the area with lead concentrations exceeding the 421 mg/kg PRG. In summary:

• Nearly all the samples collected along edge of the former geomembrane (Figures 7 and 10, Attachment 1) had total lead concentrations above the PRG of 421 mg/kg. In general, most of the samples collected along the geomembrane boundary exhibited lead concentrations in excess of 10,000 mg/kg.

• All of the deeper (6 to 12-inch samples) collected along the former geomembrane (Figure 10, Attachment 1) had concentrations above the PRG. All but one had concentrations above 1,000 mg/kg.

• The eastern boundary of the soil and sediment contaminated by lead is located where soil with lead above the PRG appears to fall between the 200D and 250D grid lines. The northern boundary of the contamination is approximately at the 150L grid line and the southern boundary is near the 150R grid line (Figure 9 and 10, Attachment 1).

• Laboratory preparation included the use of a sieve stack with a final #35 sieve. This size is equal to a 0.5-millimeter (mm) opening. In general, most trap and skeet shotgun rounds fire size 8 to size 9 lead shot are approximately 2.3 to 2.03 mm in size. The use of the #35 sieve screened out all but the most fragmented lead shot. Based on the high lead concentrations in the sieved soil, the data suggests that lead concentrations in the samples tested was predominantly the result of leaching and not lead present in the form of shot.

• Four samples were analyzed for leachable lead by the toxicity characteristic leaching procedure (TCLP) method. The results ranged from 0.15 mg/L to 140 mg/L. Three of the four samples contained leachable lead concentrations above the Resource Conservation and Recovery Act (RCRA) hazardous waste designation for lead (D008 waste) of 5 mg/L.

• Twenty soil samples were screened and evaluated for pellet counts. Based on the data collected, the conversion factor was 15.48 pellets per gram of weight. This is relatively comparable to the previous conversion factor used by Harding of 12.3 pellets per gram.

Pellet counts ranged from zero to 15,799. Figure 3 shows the current and historical pellet counts.

3.2 Extent of COPCs in Sediment

The total lead concentrations in sediment were compared to the PRG of 312 mg/kg. The additional metals were compared to the Delaware Department of Natural Resources and

F16PX02621 9 December 2017

Environmental Control (DNREC) screening level tables (DNREC, 2016). This table provides a preliminary screening value to determine if potential additional ecological risk evaluations are necessary.

At the request of the Service, the sediment results were also compared to the threshold effect concentration (TEC) and probable effect concentration (PEC) values provided by MacDonald et al (2000).

• The total lead concentrations in both the shallow and deep samples from SED-01, SED- 04, SED-05, and SED-06 exceed the lead PRG of 312 mg/kg.

• The total lead concentrations in both the shallow and deep samples from SED-02, SED- 03, SED-07, and SED-08 did not exceed the PRG of 312 mg/kg. These samples are also located outside of the boundary where elevated (>312 mg/kg) concentrations of lead were detected in soil (Figures 12 and 14, Attachment 1).

• Antimony, arsenic, copper, lead, and mercury were detected at concentrations above DNREC screening level values for freshwater sediments. In general, elevated concentrations of antimony, arsenic, copper, and mercury correlated closely to total lead concentrations. Samples with lead concentrations above the PRG also exhibited elevated concentrations of other metals. As such, lead can be used as an indicator compound for other metals that have concentrations above screening values.

• Arsenic, copper, lead, and mercury were detected at concentrations above the TEC presented in the above cited reference.

• Arsenic and lead were detected at concentrations above the PEC presented in the above cited reference.

3.3 Extent of COPCs in Surface Water

The surface water analytical results were compared to DNREC screening levels for freshwater ecological receptors and DNREC 2016 acute and chronic water quality standards for freshwater.

In summary, the following metals were observed in the following sampling locations at concentrations above screening values:

• Aluminum – SW-01, SW-06, SW-07, and SW-08

• Antimony - SW-04

• Arsenic - SW-01

• Barium - all eight locations

• Iron - SW-01, SW-07, and SW-08

• Lead - SW-01, SW-04, SW-05, SW-06, and SW-07

• Manganese - SW-07 and SW-08

• Mercury – all eight locations Lead concentrations in SW01 and SW04 were the only samples to contain concentrations above surface water screening values for acute values.

F16PX02621 10 December 2017

The following metals were observed in the following sampling locations at concentrations above chronic freshwater screening values:

• Aluminum – SW-01, SW-06, SW-07, and SW-08

• Cadmium - SW-01

• Iron – SW-07 and SW-08

• Lead - SW-01, SW-04, SW-05, SW-06, SW-07, and SW08

3.4 Extent of Impacts and Transport Mechanisms

As described in previous sections, the soil and sediment COPC associated with the firing range is lead, which is primarily found in soil and sediment within the shot fall zone to depths at least 12 inches below ground surface (bgs). The primary transport mechanism for the existing contamination is through upland and sediment erosion and surface water runoff. Erosion of contaminated soil and/or sediment is the likely source of COPCs to surface water.

Pellet density counts were conducted during the previous sampling event and the SSI. The extent of visible and sieve counted pellets are shown on Figure 3. It is assumed that lead shot is the primary source of COPC at the Site and the boundary shown on Figure 3 (roughly the 10-count contour line) provides the extent of source material.

F16PX02621 11 December 2017

4. IDENTIFICATION OF REMOVAL ACTION OBJECTIVES

Based on the Guidance on Conducting Non-Time-Critical Removal Actions under CERCLA (EPA, August 1993) and information required by the NCP (40 CFR 300.415), an EE/CA includes the development of RAOs as the first of three phases. The following steps were used in developing the RAOs.

• Identify ARARs;

• Identify cleanup levels using ARARs, background conditions, and human health and environmental risk-based levels, including levels necessary to protect wildlife species;

• Develop general response actions;

• Identify and screen technologies and process options (including innovative technologies);

and

• Assemble remaining technologies and process options into removal action alternatives.

4.1 Removal Action Objectives

The RAOs for the Site are to: (1) prevent potential exposure of ecological and human receptors to unacceptable concentrations of lead in soil and sediment; and (2) attain all ARARs. RAAs are based on soil and sediment areas with lead concentrations that exceed the site-specific PRGs.

4.2 Statutory Authority

Section 104 of CERCLA vests the President with the authority to respond to releases and threatened releases of hazardous substances to protect human health and the environment (42 USC § 9604). That authority has been delegated to the Secretary of the Interior with respect to releases on or from land under the jurisdiction, custody, or control of the Department of the Interior [Executive Order 12580, 52 Fed. Reg. 2923 (Jan. 29, 1987), as amended by Executive Order 13016, 61 Fed. Reg. 45871 (Aug. 30, 1996)]. The Service has been delegated the Secretary’s response authority for land under its jurisdiction (Departmental Manual, Chapter 7, Part 207), and it exercises that authority in accordance with requirements of the NCP.

4.3 Determination of Removal Action Scope

The following sections detail the proposed RAAs for both soil and sediment containing lead concentrations exceeding the site-specific PRGs.

The RAAs for soil and sediment are outlined on Figures 4 and 5. Those areas were established laterally based on a point-by-point, direct comparison of the recent and historical locations that had lead concentrations above the PRGs. Estimated removal depths were based on the available point-by-point, depth-discrete, analytical data from the recent and historical sampling events.

The lateral and/or vertical extent of soil contamination in the proposed RAAs may be subject to modification should additional data become available. Such a change would not affect the cost comparison in this EE/CA; however, it could affect the total cleanup costs. In general, the extent of contamination has been defined; however, additional characterization could further reduce uncertainty and could further constrain the final removal volumes. Additional site characterization activities could include the use of an x-ray fluorescence (XRF) instrument, visual observations, and/or discrete soil sampling and subsequent laboratory analysis.

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4.4 Removal Schedule

The Service has determined that a NTCRA is appropriate at the Site. The removal action could begin within three to six months following approval of this EE/CA, but the timeframe for the initiation of removal actions is dependent upon the availability of funds and seasonal limitations on work as dictated by the presence of threatened and endangered species, weather conditions, and/or equipment availability.

Based on prior experience with implementation of removal action technologies similar to those proposed in this EE/CA and the volume of material to be removed, it is estimated that a typical removal action undertaken can be completed in approximately three months, excluding time for rehabilitation/revegetation. The proposed schedule does not account for the time required to obtain State and/or Federal permits.

4.5 Planned Removal Action Activities

After the Service releases this EE/CA, and solicits and responds to public comment; an Action Memorandum will be issued selecting a removal action. Following issuance of the Action Memorandum, removal action activities at the Site can be initiated.

4.6 Applicable or Relevant and Appropriate Requirements

Applicable requirements are those standards, requirements, criteria, or limitations determined to be legally applicable under Federal or State laws that specifically address a hazardous substance, pollutant, contaminant, response action, location, or other circumstance at a CERCLA site.

Relevant and appropriate requirements are those standards, requirements, criteria, or limitations promulgated under Federal and State laws that address problems or situations similar to those encountered at the CERCLA site, and therefore, are well suited for that site. Although not legally applicable, these requirements are relevant and appropriate for a CERCLA site [NCP (40CFR 300.415(j))].

A requirement under other environmental laws may be either applicable, or relevant and appropriate, but not both. Identification of ARARs must be done on a site-specific basis and involves a two-part analysis: 1) a determination whether a given requirement is applicable; then, if it is not applicable; 2) a determination whether it is nevertheless both relevant and appropriate.

To Be Considered (TBC) criteria are non-promulgated advisories or guidance issued by the Federal or a State government that are not legally binding and do not have the status of potential ARARs. However, in many circumstances TBCs will be considered along with ARARs.

Potential ARARs are summarized in Tables 1, 2, and 3. The ARARs are divided into three categories and described in the following sections.

4.6.1 Chemical-Specific ARARs

Chemical-specific ARARs address management of specific chemicals, including the release into the environment of materials possessing certain chemical or physical characteristics or containing specific chemical compounds. These requirements generally set health or ecological risk-based concentration limits for specific chemicals or hazardous substances. Summaries of chemical-specific ARARs are presented in Table 1.

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4.6.2 Location-Specific ARARs

Location-specific ARARs are based on the geographical or physical location of the Site, rather than the nature of the contaminants or the proposed removal actions. These requirements may restrict activities in certain sensitive environments, such as wetlands, endangered species habitats, or areas of historical or cultural significance. For example, Federal and State ARARs exist for sites where removal activities would impact wetlands, flood plains, critical habitats, wilderness areas, or areas of historic and/or archeological preservation areas. Summaries of location-specific ARARs are presented in Table 2.

Any removal action selected for the Site must meet the substantive requirements of the National Wildlife Refuge System Improvement Act (NWRSIA) (16 USC § 668dd).

4.6.3 Action-Specific ARARs

Action-specific ARARs are activity-based or technology-based requirements, and typically affect performance, design, or other similar action-specific controls or restrictions on certain activities related to remediation.

This group of requirements includes ARARs that are action-specific for the management of hazardous substances, such as Resource Conservation and Recovery Act (RCRA) regulations for landfills, Clean Air Act standards for air contaminant emission sources, and Clean Water Act standards for effluent discharges to surface water bodies and pretreatment standards for storm water discharges. Summaries of potential action-specific ARARs are presented in Table 3.

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5. IDENTIFICATION AND SCREENING OF REMOVAL ACTION ALTERNATIVES

The general approach for identifying removal action alternatives is as follows:

• Develop a Comprehensive List of Potential Technologies – The KGS Team initially screened potential technologies from a complete summary of technologies that could be applied to soil and sediment removal actions for the Site.

• Eliminate Unsuitable Technologies Based on Initial Criteria – Potential removal or remedial alternatives are screened, and some removed from further consideration based on likely concerns with effectiveness, implementability, cost, or a combination of these criteria.

• Develop Alternatives Based on Technologies Retained – Section 5.3 presents the final technologies used to develop the removal action alternatives discussed below.

5.1 List of Potential Technologies

For the purposes of this EE/CA, the following soil/sediment removal action alternatives are considered and discussed in more detail in following sections:

• Geosynthetic barrier

• In-situ treatment

• Excavation with ex-situ treatment

• Capping

• Excavation with off-site disposal

• Soil screening

• pH amendments

5.2 Screening of Unsuitable Removal Action Alternatives

Technologies that were screened out, included:

• Geosynthetics for minimizing exposure - The effectiveness of geosynthetics to minimize contact is well documented. However, the use of geosynthetics alone would result in significant loss of habitat, which is incompatible with the purposes of the Refuge and the National Wildlife Refuge System as described in NWRSIA. In addition, geosynthetics are also not permanent and subject to degradation and damage. As such, geosynthetics were screened out from consideration for both upland soil and sediment.

• In-situ treatment of upland soil - In-situ treatment refers to the physical or chemical treatment of soil in place. Treatments include soil flushing, solidification, stabilization, electrokinetic separation, or phytoremediation. Because of potential ecological habitat disturbance and destruction, and the shallow nature of the contamination, in-situ treatments were not retained for further evaluation.

• Excavation with onsite consolidation - Excavation with onsite consolidation and capping can be an effective means to manage contaminated soil. The site is relatively small in nature and capping in place is a more viable solution than excavation, consolidation, and

F16PX02621 15 December 2017 capping. As such, excavation and consolidation has been screened from use for both upland soil and sediment.

• Screening of soil for lead removal – At firing ranges that use large projectiles (e.g., rifles, etc.) the removal of lead fragments via physical screening can be a viable alternative. The Site is impacted by small lead shot associated with trap and screen shooting, and based on the data collected in the SSI; the soil that were passed through a #35 sieve still contained highly-elevated lead concentrations. Further, use of a small screen size in a removal action of this magnitude is not viable. As such, onsite removal of lead via screening and reuse of the soil onsite has not been retained.

• pH amendments – pH amendments can successfully be used to minimize the leaching of lead in soils. While raising the pH of soils may assist in reducing future leaching, it would not eliminate direct exposure to lead. The addition of amendments would also have a harmful effect on ecological receptors and significantly inhibit plant growth at the Refuge. As such, pH amendments have not been retained for further consideration.

• In-Situ Treatment for Wetlands – Numerous studies have shown that various forms of activated carbon (such as SediMite™) can be used to treat contaminated sediments.

However, there is very limited data on the applicability of these in-situ methods to sediments contaminated with the relatively high levels of lead at the Site. Other challenges for the application of in-situ methods include the presence of a dense organic mat in the wetland.