FINAL PLAN OF REMEDIAL ACTION

100 Walnut Street Site

100 Walnut Street, 103 North Poplar Street 105 North Poplar Street Wilmington, Delaware

September 2018 DNREC Project No. DE-1114

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 100 Walnut Street Site.

DNREC issued public notice of the Proposed Plan of Remedial Action (Proposed Plan) for the Site on August 8, 2018, and opened a 20-day public comment period. The Proposed Plan is attached. There were no 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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Date

mistrator Section

PROPOSED PLAN OF REMEDIAL ACTION

100 Walnut Street Site Wilmington, Delaware

DNREC Project No. DE-1114

t

August 2018

Delaware Department of Natural Resources and Environmental Control Di vision of Waste and Hazardous Substances

Site Investigation & Restoration Section 391 Lukens Drive

New Castle, Delaware 19720

CONTENTS

• Figures: 1, 2 & 3

• Glossary of Terms

PROPOSED PLAN OF REMEDIAL ACTION

Approval:

100 Walnut Street Site Wilmington, Delaware

DNREC Project No. DE-1114

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

Approved by:

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PROPOSED PLAN Questions & Answers

l 00 Walnut Street

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. A legal notice is published in the newspaper for a 20-day public 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 100 Walnut Street Site?

The 100 Walnut Street Site consists of the properties located at 100 North Walnut Street, 103 North Poplar Street, and 105 North Poplar Street in Wilmington, Delaware (Figure 1 ). It is identified as New Castle County tax parcel numbers 26-043.40-051 , 26-043.40-054, and 26-043.40-055, which are currently zoned 26C-3 - Central Retail. It is bounded to the north by an aspha)t parking Jot, to the northeast by the Gateway House, a short-tenn residential facility for men, to the east/southeast by 121 North Poplar Street, to the south by Front Street, and to the west by Walnut Street. The Site is currently utilized by a car rental business, consisting of an office building, asphalt parking lot, and an empty grassy lot (Figure 2). The I 03 North Poplar Street and I 05 North Poplar Street properties were previously a part of the 121 North Poplar Street Site (DE-I 066), but have been incorporated into the I 00 Walnut Street Site as part of the redevelopment of all of the properties, along with the DTC-2°d and Walnut Street Site, into a transit center.

What happened at the 100 Walnut Street Site?

According to historical maps, the Site was the former location of various leather factories and other manufacturing businesses, which operated on the property from approximately 1868 through sometime in the 1950s/1960s.Manufacturing operations included the leather tanning process, which resulted in the release of elevated concentrations of metals, namely arsenic and lead, into site soils. Subsequently, a retail gas station was in operation on the Site for a period of time. Most recently, the property has been utilized as a public parking lot and car rental facility and the grassy lot has remained vacant with some off street parking of cars.

What is the environmental problem at the 100 Walnut Street Site?

In I 992, a Phase II Investigation was conducted on the 100 North Walnut Street property in order to determine impacts from past releases from underground storage tanks located on the Site at that time. This release at the property was addressed under the Underground Storage Tank Branch of DNREC and a No Further Action letter was issued. Subsequently, in 1998, a more comprehensive Phase II Investigation was conducted on the Site in order to identify the presence of contamination associated with former tannery operations. In 2003, a Remedial Investigation was initiated on the Site, on behalf of the Delaware Department of Transportation, who had

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purchased the property that year with plans to redevelop it into a transit center and commercial businesses. A human health risk assessment indicated that arsenic, lead, and multiple polycyclic aromatic hydrocarbons, or PAHs, were the contaminants of concern in soil at the Site. Volatile organic compounds, or VOCs, were identified in the groundwater flowing beneath the Site. 'Theoretical impact posed by site groundwater to the waters of the Christina River, located approximately 1,000 feet south of the Site was determined to be insignificant. Site operations as a car rental facility and parking lot continued during this time.

ln preparation for redevelopment as the transit center, additional soil, and groundwater sampling was conducted on the Site in October 2016 and March/ April 2017 to assess current conditions. A Supplemental Environmental Summary Letter Report was issued to document both the sample results and the evaluation of risk to human health and the environment. Field observation and soil sample results confirmed the presence of elevated arsenic and lead from tannery waste, in the interval between 0 to greater than 4 feet below ground surface. Repeated exposure to this soil could pose an unacceptable increased human health risk to future site workers and site occupants. The Site is currently, and will continue to be, serviced by the City of Wilmington public water utility, meaning that site users will not be exposed to the groundwater flowing beneath the Site. However, it was determined that in the unlikely event that groundwater flowing beneath the Site was consumed, the exposure could also pose an unacceptable increased human health risk to future site occupants due to the presence of elevated metals and voes, which appear to originate from an off-site source. An assessment of the potential for the intrusion of vapor, generated by VOCs into the encfosed structures focated on the Site, indicate that the increased human health risk posed by exposure to these vapors is acceptable. Updated ca\cu\aticms of the theoretica\ discharge of groundwater COCs into the Christina River indicate negligible risk to the environment.

In 1996, a Phase II Investigation was completed on the 103 and 105 North Poplar Street properties in order to identify the presence of contamination as part of the I 21 North Poplar Street Site (DE-1066). The properties were capped in 1997 with two feet of clean fill. Soil samples were collected as part of the October 2016 investigation conducted on the 100 North Walnut Street property to evaluate if site conditions had changed since the soil cap was installed. There was no change in soil quality, therefore the Certification of Completion of Remedy (COCR) for the soil was issued by DNREC for the soil on the entire 121 North Poplar Street Site, including the 103 and 105 North Poplar Street properties.

What does the owner want to do at the 100 Walnut Street Site?

The Site will be redeveloped into a transit center and multi-story parking facility with commercial facilities on the street level, as part of the Wilmington Transit Center project.

What clean-up actions are needed at the t 00 Walnut Street Site?

DNREC proposes the following remedial actions for the Site, which need to be completed before a Certification of Completion of Remedy (COCR) can be issued.

I . A Remedial Action Work Plan must be submitted to DNREC for approval within 60 days of the issuance of the Final Plan of Remedial Action.

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2. Areas as identified in Figure 3 must be capped with impervious material (e.g. buildings, asphalt, or concrete). The remainder of the Site must also be capped, but may be covered with either impervious material or a minimum of one foot of DNREC-approved fill material. Capping must be performed pursuant to the schedule indicated in the DNREC-approved Remedial Action Work Plan.

3. A draft Environmental Covenant must be submitted to DNREC for approval within 60 days of the issuance of the approved Long Term Stewardship (LTS) Plan.

4. 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 New Castle 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:

a. Use Restriction. Use of the Property shall be restricted solely to those non-residential type uses permitted within Commercial, Manufacturing, or Industrial Districts;

b. Installation of Clean Utility Corridors. Soil excavated for the installation of utility corridors must be properly disposed of at a licensed disposal facility. The material imported to backfill the ex.cavations must be DNREC-approved materia\ meeting the qwdity requirements for the use restriction noted above.

c. 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 DNREC­SIRS and DNREC Division of Water;

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; and

e. 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.

5. 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 potentially­contaminated soil and groundwater at the Site.

6. The CMMP will be implemented upon its approval by DNREC.

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7. A Long-Term Stewardship Plan shall be submitted to DNREC for approval in accordance with the schedule set forth in the approved Remedial Action Work Plan. The L TS plan will detail: 1) the groundwater monitoring requirements and schedule to be followed in order to monitor the attenuation of the Contaminants of Concern (COC) in groundwater; and, 2) the site-inspection schedule to be followed in order to ensure the long-term integrity of the remedy.

8. The L TS Plan must be implemented within 60 days of its approval by DNREC.

9. 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.

10. 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.

How can I find additional information or comment on the Proposed Plan?

The complete file on the Site including the Remedial Investigation Report 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 public comment period begins on August 8, 2018 and ends at cfose of business (4:30 pm) on August 28, 2018. Please send written comments to the DNREC office at 391 Lukens Drive, New Castle, DE 19720 to Lindsay Hall, Project Officer or via email to Lindsav. Hall@state.de.us.

Figure 1: Site Location Figure 2: Site Layout Figure 3: Area Requiring Impervious Cap

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Glossary of Terms Used in this Proposed Plan

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 orooerlv. 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 site on which hazardous substances have been found.

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 (IIlIRA) health risk associated with exposure to site-related

contaminants Phase II Assessment Environmental study of a site which includes the sampling

of one or more of the following media: soils, groundwater, surface water, sediment, and/or wastes on the property, as appropriate.

Remedial Investigation (RI) Thorough environmental study of a site which includes I) 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.

SIRS Site Investigation and Restoration Section of DNREC, which oversees the investigation and cleanup of sites that may have been contaminated as a result of oast use

CJ 100 N. Walnut St (OE-1114)

Site Location!fopographic Map 100 N. Walnut St (DE-1114)

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