PROPOSED PLAN OF REMEDIAL ACTION

DEERFIELD FARMS Dover, Delaware

DNREC Project No. DE-1701

September 2021

Delaware Department of Natural Resources and Environmental Control Division of Waste and Hazardous Substances

Remediation Section 391 Lukens Drive

New Castle, Delaware 19720

CONTENTS

• Figures: 1 & 2 • Glossary of Terms

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PROPOSED PLAN OF REMEDIAL ACTION

Deerfield Farms Dover, Delaware

DNREC Project No. DE-1701

Approval: This Proposed Plan meets the requirements of the Hazardous Substance Cleanup Act.

Approved by:

Qazi Salahuddin, Environmental Program Administrator Remediation Section

Date

09/27/2021

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PROPOSED PLAN Questions & Answers

Deerfield Farms Site

(DE-1701)

What is the Proposed Plan of Remedial Action? The Proposed Plan of Remedial Action (Proposed Plan) summarizes the clean-up (remedial) actions that are being proposed to address contamination found at the Site for public comment. A legal notice is published in the newspaper for a 20-day comment period. DNREC considers and addresses all public comments received and publishes a Final Plan of Remedial Action (Final Plan) for the Site. What is the Deerfield Farms Site? The Deerfield Farms Site [‘Site’] (DE-1701) is located off of West Denneys Road in Dover, Kent County, Delaware, and consists of one tax parcel (2-00-05700-02-0400-00001), totaling approximately 11.10 acres (Figure 1). The nearest intersection is West Denneys Road and Packard Drive/Grinding Wheel Drive about 1,000-feet to the west-southwest of the Site. The Site consists of undeveloped woodlands and wetlands with a small mowed upland area in the northern portion (Figure 2). The eastern Site boundary is adjacent to a railroad easement and the Cahoon Branch transects along the southern Site boundary. What happened at the Deerfield Farms Site? According to historical documentation, the Site was acquired by William McKee in the 1860s who farmed the area as well as operated a store at the former duPont Station located along the railroad easement to the east of the Site. Historical aerial photographs depict land disturbances in the central portions of the Site in the late-1930s indicative of potential borrow pit activities. The land disturbing activities appeared to have ceased by the early to mid-1950s. Vegetation clearing appeared in the early-1990s throughout the northern and central portions of the Site. By the late-1990s, much of the wooded areas of the northern central portion of the Site had been cleared from the area identified as the historical fill area in the Brownfield Investigation (BFI) Report (Figure 3). Furthermore, the Site is also located down-range of a former small arms firing range that was operated by the Delaware State Police from the late-1960s until the mid-2000s. What is the environmental problem at the Deerfield Farms Site? In October 2018, a Limited Subsurface Evaluation was completed on the Site to characterize the historical fill materials disposed on the property in the early- to late-1990s. Nine test pits were excavated from the suspected historical fill area in order to characterize the fill material and extent. The types of materials noted in the fill layer included a mix of select fill/sandy soils, and trace amounts of concrete, asphalt, wood, organic debris, metal, and/or plastic ranging from 1 to

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3 feet thickness in eight of the nine test pits. The fill layer thickness encountered in Test Pit 8 (TP-8) extended to 8 ft. of thickness. Generally, the fill layer was encountered within 3 to 4 feet (ft.) below ground surface (bgs) with extents encountered depths of 7 ft. bgs to 12 ft. bgs. Nine soil samples from were collected from the test pits at specific interval depths and analyzed for Target Compound List (TCL) Volatile Organic Compounds (VOCs), Priority Pollutant List (PPL) Metals, and Polynuclear Aromatic Hydrocarbons (PAHs). Several PAHs, metals, and two VOCs were detected at concentrations below their respective Hazardous Substance Cleanup Act (HSCA) Screening Levels (SLs). A Brownfield Investigation (BFI) was completed on the Site in April 2020. Prior to the commencement of the intrusive activities on the Site, an Unexploded Ordnance (UXO) Survey was completed in order to search for UXOs, bullets, lead shot, etc. on the ground surface originating from the former Delaware State Police small arms firing range located on the northwest adjacent property. The UXO surveyor cleared pathways to and surrounding the sample locations to assure safe access to those areas. According to the UXO report included in the appendices of the BFI report, debris encountered during the clearance activities included shotgun shell casings, an expended flare casing, wire, and additional solid waste materials. The report findings concluded that “[N]one of the materials encountered were identified as ordnance or material potentially presenting an explosive hazard (MPPEH).” During the BFI field investigation, eight (8) test pits and ten (10) soil borings were advanced on the Site. Five of the soil borings were converted to monitoring wells. Eighteen (18) surface soil and eighteen (18) deeper soil samples were collected from the test pits and soil borings. In addition, eight (8) surface soil samples were collected from the wetland areas of the Site and five (5) co-located surface water and sediment samples were collected. All solid samples were screened at the DNREC Screening Laboratory for TCL VOCs, TCL Semi-Volatile Organic Compounds (SVOCs), TCL pesticides, polychlorinated biphenyls (PCBs), and Target Analyte List (TAL) inorganics. Based on the screening results, confirmatory analysis was completed at a HSCA-approved laboratory on select solid samples. The five (5) groundwater samples and the five (5) surface water samples were analyzed at a HSCA-approved laboratory for TCL VOCs, TCL SOVC, TCL Pesticides, PCBs (EPA method 680), TAL inorganics (including cyanide and mercury), semi-volatile Explosive Residuals, and Perchlorate. Detected contaminant concentrations were compared against the HSCA Screening Levels (SLs) for human health and the environment. According to the analytical results, one (1) metal (thallium) and one (1) SVOC (benzo(a)pyrene) were detected above their respective HSCA Screening Level (SLs) for human health in the surface soil. Two (2) metals (arsenic and thallium) were identified above their respective HSCA SLs for human health in the subsurface soil samples. And four (4) metals (arsenic, cobalt, iron, and manganese) were detected above their respective HSCA SLs for human health in total and dissolved groundwater samples. Ten (10) metal (antimony, arsenic, barium, cadmium, copper, iron, lead, nickel, selenium, and zinc) contaminant concentrations exceeded their respective HSCA SLs for Ecological risk in sediment. Sixteen (16) metal (aluminum, arsenic, barium, beryllium, cadmium, cobalt, copper, iron, lead, manganese, mercury, nickel, selenium, thallium, vanadium, and zinc) concentrations exceeded their respective HSCA SLs for surface water samples compared to the Ecological Surface Water Fresh. No other contaminants were detected

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above their respective HSCA SLs. Contaminant concentrations above their respective HSCA SLs were retained as Contaminants of Potential Concern (COPCs) for carcinogenic and non-carcinogenic (Hazard Index, HI) risk assessment to human health and ecological risk. A Human Health Risk Assessment (HHRA) was completed as part of the BFI report for multiple exposure current and potential future scenarios including resident (child and adult), indoor worker, outdoor worker, composite (indoor and outdoor) worker, excavator, recreational users, and trespassers to surface and subsurface soil. A combined soils exposure risk was also calculated for the residential (child and adult) exposure scenario as well. Additionally, HHRA was calculated for the residential and indoor worker exposure scenarios to exposure to groundwater as tap water. According to the results of the HHRA, no unacceptable carcinogenic or HI risk were calculated for any of the exposure scenarios for the surface soil and subsurface soils as well as the combined soil for the residential exposure scenario. Unacceptable HI risk was calculated from the exposure to dissolved groundwater for the residential exposure scenario. However, there was no unacceptable carcinogenic risk to the residential and indoor commercial worker exposure to groundwater as tap water. A Screening Level Ecological Risk Assessment (SLERA) was completed as part of the BFI to evaluate the potential risk to plants, soil invertebrates, reptiles, amphibians, insectivorous birds and mammals, and predatory birds and mammals that might be exposed to the COPCs at the Site. The primary COPCs were metals in soil, sediment, and surface water at the Site. Refinement analyses were conducted to further evaluate the COPCs in the Site media as part of the SLERA. Multiple lines of evidence were used as a weight in evidence approach to assess the potential for adverse effects to populations of ecological receptors from the COPCs in the Site media. Based on the results of these analyses for risk characterization, the potential for adverse ecological effects is not expected and additional evaluations of potential ecological risk at the Site was not warranted. What does the owner want to do at the Deerfield Farms Site? The Brownfield Developer plans to preserve the land for conservation/open land purposes. What additional clean-up actions are needed at the Deerfield Farms Site? DNREC proposes the following remedial actions for the Site, which need to be completed before a Certificate of Completion of Remedy (COCR) can be issued.

1. A proposed Environmental Covenant must be submitted to DNREC for approval within 60-days of the issuance of the Final Plan of Remedial Action.

2. An Environmental Covenant, consistent with Delaware’s Uniform Environmental Covenants Act (7 Del.C. Chapter 79, Subchapter II) must be recorded in the Office of the Kent County Recorder of Deeds within 60-days of the issuance of the Long-Term Stewardship Plan. The Environmental Covenant must include the following activity and/or use restrictions:

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[a.] Limitation of Groundwater Withdrawal. No groundwater wells shall be installed, and no groundwater shall be withdrawn from any well on the Property without the prior written approval of the DNREC-RS and the DNREC Division of Water;

[b.] Compliance with Contaminated Materials Management Plan. All work required by the Contaminated Materials Management Plan must be performed to DNREC’s satisfaction in accordance with the Plan.

3. A Contaminated Materials Management Plan (CMMP) must be submitted to DNREC within 60-days of the issuance of the Final Plan of Remedial Action. The CMMP will provide guidance to enable construction workers to safely handle any potential contaminated soil and groundwater at the Site.

4. The CMMP will be implemented for any future soil disturbance upon its approval by DNREC.

5. Close and abandon the monitoring wells in accordance with state and local regulations.

6. A Remedial Action Completion Report must be submitted to DNREC within 60-days of the completion of the remedial actions required in this Proposed Plan.

7. A request for a Certification of Completion of Remedy (COCR) must be submitted to DNREC within 60-days of approval of the Remedial Action Completion Report.

What are the long-term plans for the Site after the cleanup? At the time of the publication of this document, the Brownfield Developer has expressed to DNREC-RS that their intentions are to preserve the land for conservation/open space use. At this time, the Brownfield Developer has not indicated that there are any intentions for land disturbing activities (e.g. digging, drilling, excavating, grading, constructing, earth moving, etc.) to take place on the Site. According to previous environmental investigations and the BFI, there is an approximately one (1) acre area of historical fill as been identified on the Site (Figure 3). The BFI included the collections of soil (shallow and deep) and groundwater from the historical fill area. Based on the HHRA and the SLERA, no unacceptable carcinogenic or Hazard Index (HI) risk was determined for the on-site soils (shallow and combined shallow and deep), including the areas of the historical fill. However, notwithstanding, the historical fill area contains trace amounts of solid waste debris outside the scope of the Regulations Governing Hazardous Substance Cleanup but warranting appropriate management if disturbed. During the BFI, materials identified within the historical fill area included a mix of select fill/sandy soils, with trace amounts of concrete, asphalt, wood, organic debris, metal, and/or plastic. Although not currently identified, the buried organic debris could pose a risk of methane to any future enclosed structures, or during land disturbing activities. As such, DNREC will require further evaluation of methane intrusion potential prior to approving future development of the Site with enclosed structures. Furthermore, as the Site is located down-range and adjacent

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to a former small arm shooting range, DNREC also advises continued awareness of the potential for encountering small arm bullet and/or shot fragments as well as inert training props, such as spent flares, etc. The DNREC-approved CMMP will include requirements regarding the management and disposal of the solid waste debris and any potential items related to the former small arm shooting range. How can I find additional information or comment on the Proposed Plan? The complete file on the Site including the Brownfield Investigation and the various reports are available online at:

http://www.nav.dnrec.delaware.gov/DEN3/Detail/FacilityDetail.aspx?id=10753527 The 20-day public comment period begins on Wednesday, September 29, 2021 and ends at close of business (4:30 pm) on Monday, October 18, 2021 Please send written comments to the DNREC to Morgan McGee-Solomon Project Officer or via email to RS_Public_Comments@delaware.gov.

Figure 1: Location Map Figure 2: Site Layout Map Figure 3: Site Features Map

MMS:slw; MMS21082.doc; DE 1701 II B 8

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Glossary of Terms Used in this Proposed Plan

Area of Concern (AOC) A discrete section of the Site representing the local bounds of contamination in soil or ground water.

Brownfield Development Agreement (BDA)

This legal agreement is between a potential developer of a Delaware-certified Brownfields Site and the DNREC. The developer agrees to investigate and cleanup a Brownfields property under the oversight of the Department in exchange for liability protection.

Brownfield Investigation (BFI) Thorough environmental study of a site which includes 1) sampling of site environmental media and/or wastes on the property and 2) conducting a preliminary risk assessment using the data collected to determine the risk posed to human health and the environment.

Certified Brownfield A Brownfield that DNREC has determined is eligible for partial funding through the Delaware Brownfields Program.

Certification of Completion of Remedy (COCR)

A formal determination by the Secretary of DNREC that remedial activities required by the Final Plan of Remedial Action have been completed.

Contaminant of Concern (COC) Potentially harmful substances at concentrations above acceptable risk levels.

Contaminant of Potential Concern (COPC)

A hazardous substance that may or may not be contributing to the unacceptable risk of the Site.

Contaminated Materials Management Plan

A written plan specifying how potentially contaminated material at a Site will be sampled, evaluated, staged, transported, and disposed of properly.

*Exposure Contact with a substance through inhalation, ingestion, or direct contact with the skin. Exposure may be short term (acute) or long term (chronic).

Final Plan of Remedial Action DNREC’s adopted plan for cleaning up a hazardous site.

Hazardous Substance Cleanup Act (HSCA)

Delaware Code Title 7, Chapter 91. The law that enables DNREC to identify parties responsible for hazardous substances releases and requires cleanup with oversight of the Department.

Human Health Risk Assessment (HHRA)

An assessment done to characterize the potential human health risk associated with exposure* to site related chemicals.

Polychlorinated biphenyls (PCBs) A synthetic, carcinogenic chemical formerly used in a wide

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variety of industrial applications but banned from most uses by the US EPA in 1979.

Risk Likelihood or probability of injury, disease, or death.

Risk Assessment Guidance for Superfund (RAGS)

An EPA guidance document for Superfund sites

Restricted Use Commercial or Industrial setting

RS Remediation Section of DNREC, which oversees cleanup of sites that were contaminated as a result of past use, from dry cleaners to chemical companies.

Toxic Substance Cleanup Act (TSCA) The federal statute requiring and regulating the cleanup of PCBs.

US EPA United States Environmental Protection Agency