FINAL PLAN OF REMEDIAL ACTION

FORMER MCGRELLIS AUCTION HOUSE SITE

713, 721, and 729 Valley Road Hockessin, Delaware

January 2018 DNREC Project No. DE-1610

This Final Plan of Remedial Action (Final Plan) presents clean-up actions required by the Department of Natural Resources and Environmental Control (DNREC) to address environmental contamination at the McGrellis Auction House Site.

DNREC issued public notice of the Proposed Plan of Remedial Action (Proposed Plan) for the Site on December 12, 2017 and opened a 20-day public comment period. The Proposed Plan is attached. There were no substantive comments from the public; therefore, the Proposed Plan is adopted as the Final Plan.

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

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PROPOSED PLAN OF REMEDIAL ACTION

Former McGrellis Auction House Site Hockessin, Delaware

DNREC Project No. DE-1610

November 2017

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

Site Investigation & Restoration Section 391 Lukens Drive

New Castle, Delaware 19720

CONTENTS

• Figures: 1 & 2

• Glossary of Terms

PROPOSED PLAN OF REMEDIAL ACTION

Approval:

Former McGrellis Auction House Site Wilmington, Delaware

DNREC Project No. DE-1610

This Proposed Plan meets the requirements of the Ha7.ardous Substance Cleanup Act.

Approved by:

Administrator

Date

PROPOSED PLAN Questions & Answers

Former McGrellis Auction House Site DE-1610

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 Former McGrellis Auction House Site?

The Former McGrellis Auction House Site is a 27.19 acre property comprised of three tax parcels (08-012.00-033; -073; -034) at 713, 721, and 729 Valley Road, located approximately 1 mile southwest of Hockessin, New Castle County, Delaware (Figure 1 ). Most of the property is currently covered by open field and grass lawn. An auction business operated from approximately 1998 until mid-2017 in a large building surrounded with paved parking and a paved drive to Valley Road. Two vacant homes fronting on Valley Road were formerly used as residences. South of the building, an area was leased for storage of equipment and fill soils, asphalt, and miscellaneous construction materials which were staged in piles along the south side of the parking lot. A small stormwater basin and a wetland mitigation area lie east of the parking lot. The southeast approximate quarter of the property is wooded, through which a tributary of Mill Creek flows towards the northeast.

Electric service, natural gas service, public water service (including a fire sprinkler hydrant), and public sewerage are available. However, due to the distance and elevation difference from the sewer main on Valley Road, the Auction House utilized a holding tank, which requires routine pump-out. Mushroom operations and private homes adjoin the property. Surrounding lands are used for agricultural farmlands and residential developments.

What happened at the Former McGrellis Auction House Site?

Two large ponds were present on the property near Valley Road until approximately 2002. The ponds were manmade, formed in historical kaolin clay borrow pits excavated in the early 1900s. The owners opened the pits to neighbors for dumping over a SO-year time span (1930s to 1980s), then DelDOT filled the ponds with soil and concrete to grade in approximately 2002. In 201 S, the quality and quantity of the fill materials were explored using a backhoe to excavate trenches into the former pond areas. Soil samples from the trenches were collected and analyzed at a laboratory. Some of the fill soils contained antimony, thallium, and the semi-volatile organic compound benzo(a)pyrene at concentrations above DNRECs Soil Screening Levels, and chromium and arsenic at concentrations above EPA's Industrial Regional Soil Screening Levels. In 2016-2017, prior to their purchase of the property for redevelopment, prospective purchasers investigated the former pond areas and the entire property under DNREC's Brownfields Program to identify the nature and the extent of the soil contamination.

What is the environmental problem at the Former McGrellis Auction House Site?

Surface soil samples (0-2 feet deep) contained thallium and up to 4 semi-volatile polynuclear aromatic hydrocarbon (PAH) compounds [benz(a)anthracene, benzo(a) pyrene, benzo(b) fluoranthene, and/or dibenz(a,h)anthracene] at concentrations above DNREC's soil Screening Levels. Subsurface soil contained antimony, beryllium, cobalt, iron, manganese, thallium, zinc and benzo(a)pyrene at concentrations above Screening Levels. Neither VOCs, pesticides, nor PCB homologs were detected in tested soil samples at concentrations above DNREC Soil Screening Levels. Acceptable levels of risk was calculated for future residential, commercial I industrial, and recreational exposures to surface soil.

Risks calculated for excavation worker exposures to surface soil plus subsurface soil were also cleared to be acceptable. Acceptable risks were calculated for future adult plus child residential exposures to surface plus subsurface soil. The individual Hazard Index for a future child resident posed a potentially unacceptable level of hypothetical non-cancer soil ingestion risk due to elevated manganese in subsurface soils.

Several of the 6 groundwater samples contained cobalt, iron, manganese, and mercury, while one sample had aluminum, lead, and vanadium, at concentrations above DNREC's groundwater Screening Levels for use as potable "tap water". One sample contained the VOC (tetrachloroethene or PCE) at a low concentration above the 1 microgram per liter (ug/L) Screening Level. Pesticides exceeded Screening Levels in 4 of 6 samples. No PCB homologs or semi-VOCs were detected in groundwater samples. Because the Site has public water service, the future use of site shallow groundwater for potable water is unlikely, however, maximum groundwater concentrations were used to quantify potential human health risks from hypothetical future ingestion of site groundwater as tap water. Unacceptable future ingestion risk levels resulted from the maximum concentrations of metals and pesticides. Due to Groundwater conditions, site groundwater cannot be used as a potable source and require monitoring and reporting that will be covered under a long-term stewardship plan.

Because PCE concentration (2 ug/L in MW-6) exceeded its Groundwater Screening Level (1 ug/L), a VOC Vapor Intrusion screening assessment compared the maximum observed concentration to EPA's residential I E-06 risk level concentration of 15 ug/L (EPA's VISL), indicating that potential vapor intrusion risks from 2 ug/L of PCE were acceptable (below I E-06).

What does the owner want to do at the Former McGrellis Auction House Site?

The prospective purchasers are planning to redevelop the property for mixed commercial and residential use.

What additional clean-up actions are needed at the Former McGrellis Auction House 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

2. The DNREC-approved 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 New Castle County Recorder of Deeds within 60 days of the issuance of the Final Plan of Remedial Action. The Environmental Covenant must include the following activity and/or use restrictions:

[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 DNREC-SIRS and DNREC Division of Water;

[b.] Limitation of Ground Disturbance (For possible single-family Residential use only). Future residents shall not perform land disturbance (digging, drilling, excavating, grading, constructing, earth moving, etc.) extending below 2 feet in depth on the Property, including any repair, renovation or demolition of the existing structures on the on the Property, without the prior written approval of DNREC;

[c.] 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; and

[d.] Compliance with the Long Term Stewardship Plan. All work required by the Long Term Stewardship 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 upon its approval by DNREC.

5. A Long-Term Stewardship Plan shall be submitted to DNREC for approval within 60 days of the issuance of the Final Plan of Remedial Action. The LTS plan will detail the groundwater monitoring requirements and schedule to be followed in order to monitor the attenuation of the groundwater Contaminants of Concern (COC).

6. A request for a Certification of Completion of Remedy (COCR) must be submitted to DNREC within 60 days of issuance of the Final Plan of Remedial Action.

What are the long term plans for the Former McGrellis Auction House after the cleanup?

The future activities allowable on the Site will be restricted in accordance with the Environmental Covenant. The CMMP will be completed and available for the Site.

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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 at the DNREC office, 391 Lukens Drive in New Castle, 19720. Most documents are also found on:

http://www.nav.dnrec.delaware.gov/DEN3/

The 20-day pub I ic comment period begins on November 20, 2017 and ends at close of business (4:30 pm) on December 12, 2017. Please send written comments to the DNREC office at 391 Lukens Drive, New Castle, DE 19720 attention of Patrick Boettcher, Project Officer or via email to Patrick.Boettcher@state.de.us.

Figure 1: Figure 2:

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GI ossarv o f T erms u d. th• p se ID IS ropose d Pl an Brownfield Development Agreement This legal agreement is between a potential developer of a (BDA) 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 A formal determination by the Secretary of DNREC that (COCR) remedial activities required by the Final Plan of Remedial

Action have been completed. Contaminant of Concern (COC) Potentially harmful substances at concentrations above

acceptable levels. Contaminated Materials Management A written plan specifying how potentially contaminated Plan 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. Groundwater Management Zone A geographical area where DNREC restricts drilling for

ground water because it is contaminated Hazardous Substance Cleanup Act Delaware Code Title 7, Chapter 91. The law that enables (HSCA) DNREC to identify parties responsible for hazardous

substances releases and requires cleanup with oversight of the Department.

Human Health Risk Assessment An assessment done to characterize the potential human (DURA) health risk associated with exposure* to site related

chemicals. Risk Likelihood or probability of injury, disease, or death. Risk Assessment Guidance for An EPA guidance document for superfund sites Superfund (RAGS) Restricted Use Commercial or Industrial setting

SIRS Site Investigation Restoration Section of DNREC, which oversees cleanup of sites that were contaminated as a result of past use, from dry cleaners to chemical companies

US EPA United States Environmental Protection Agency