ORIGINALSEMS DocID 2298711

FOURTH EXPLANATION OF SIGNIFICANT DIFFERENCES

for theHUNTERSTOWN ROAD SUPERFUND SITE

STRABAN TOWNSHIP, ADAMS COUNTY, PENNSYLVANIA

I. INTRODUCTION

Site Name:

Site Location:

Lead Agency:

Support Agency:

Hunterstown Road Superfund Site

Straban Township, Adams County, Pennsylvania

U.S. Environmental Protection Agency, Region III

Pennsylvania Department of Environmental Protection

Statement of Purpose

The U.S. Environmental Protection Agency (EPA) is issuing this Explanation of Significant

Differences (ESD) in accordance with Section 117(c) of the Comprehensive Environmental

Response, Compensation, and Liability Act, as amended (CERCLA), 42 U.S.C. § 9617(c), and

Section 300.435(c)(2)(i) of the National Oil and Hazardous Substances Pollution Contingency

Plan (NCP), 40 C.F.R. § 300.435(c)(2)(i). Section 117(c) of CERCLA and Section

300.435(c)(2)(i) of the NCP require the publication of an ESD when modifications to the

selected remedy are necessary, and such modification's significantly change, but do not

fundamentally alter, the remedy selected in a Record of Decision (ROD) with respect to scope,

performance, or cost.

EPA selected the remedy for the Hunterstown Road Superfund Site (the Site) in the following

ROD and three ESDs: an August 2, 1993 ROD (1993 ROD), an August 25, 1998 ESD (1998

ESD), a March 22, 2001 ESD (2001 ESD) and an August 11, 2003 ESD (2003 ESD). The ROD

and three ESDs collectively comprise the selected remedy for the Site (Selected Remedy).

Significant changes need to be made to the Selected Remedy in order for the remedy to be

protective of human health and the environment. This ESD (Fourth ESD) makes three

modifications to the Selected Remedy in regards to institutional controls, groundwater

performance standards, and a cumulative risk evaluation. Specifically, the institutional controls

(ICs) for the groundwater component of the Selected Remedy do not fully encompass all areas

where groundwater contamination is present or protect the entire groundwater extraction and

treatment system. This Fourth ESD modifies the Selected Remedy by expanding the

groundwater ICs to encompass the areal extent of groundwater contamination. This Fourth ESD

also changes the groundwater performance standards from background levels to federal

Maximum Contaminant Levels (MCLs), federal non-zero Maximum Contaminant Level Goals

(MCLGs) or Pennsylvania Medium Specific Concentrations (MSCs). MCLs are the maximum

permissible levels of a contaminant in public water supplies under the federal Safe Drinking

Water Act and codified at 40 C.F.R. Part 141. MCLGs are the levels of a contaminant in

drinking water below which there is no known or expected risk to health. MSCs are

Pennsylvania health standards for remediating contaminated sites. In addition to selecting new

groundwater performance standards for the Site, EPA is also requiring that a cumulative risk

evaluation be performed once MCLs, MCLGs and MSCs for the contaminants of concern (COC)

have been reached. Additionally, this Fourth ESD lists the COCs for the Site.

The information EPA has relied upon or considered to date in issuing this ESD has been added to

the Administrative Record for the Site in accordance with Section 300.825(a)(2) of the NCP.

The Administrative Record is available for public review at the locations listed below:

Adams County Public Library

140 Baltimore Street

Gettysburg, Pennsylvania 17325

(717)334-5716

U.S. Environmental Protection Agency, Region III

Administrative Record Reading Room

1650 Arch Street

Philadelphia, PA 19103-2029

(215) 814-3157Hours: Monday - Friday: 8:00 AM to 4:00 PM

Please call to schedule an appointment.

The Administrative Record is also available online at:

https://semspub.epa.gov/src/collection/Q3/AR108

H. SUMMARY OF SITE HISTORY. CONTAMINATION, AND SELECTED

REMEDY

A. Site History and Contamination

The Site is located on the east and west side of Hunterstown Road about 1.5 miles northeast of

downtown Gettysburg in Straban Township, Adams County, Pennsylvania (Figure 1). The

property owner, who operated a septic tank cleaning business, dumped waste at seven locations

on the property. The property is referred to as the Shealer property, which is comprised of two

parcels, one on each side of Hunterstown Road. The seven disposal areas are referred to as

Drum Burial Area 1, Drum Burial Area 2, North Cornfield Area, South Cornfield Area, Lagoon

Area, Stressed Vegetation Area and Borrow Area (Figure 1). The majority of the waste

consisted of paint sludge and various solvents. The disposal activities contaminated

groundwater, soil, surface water and sediment.

In 1983, the Pennsylvania Department of Environmental Resources, currently known as the

Pennsylvania Department of Environmental Protection (PADEP), initiated an investigation into

the dumping on the property as a result of a complaint from the Adams County Community

Environmental Control Office. In 1984, EPA issued an administrative order to conduct a

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removal action, requiring the Westinghouse Electric Corporation, one of the Potentially

Responsible Parties (PRPs) that had generated waste found at the Site, to provide potable water

to affected residents and remove all sludges and liquid materials from the Lagoon Area. The Site

was added to the National Priorities List in June 1986. Westinghouse Electric Corporation

conducted the removal of a large number of buried drums from December 1988 through May

1989.

In December 1988, the remedial investigation and feasibility study (RI/FS) was initiated. Based

on the Rl, the most significant surface soil contaminants included antimony, barium, copper,

chromium, lead, mercury, vinyl chloride and 1,1-dichloroethene (1,1-DCE). The most

significant contaminants in groundwater were volatile organic compounds (VOCs), including

trichloroethene, 1,1,1-trichloroethane, vinyl chloride, 1,1-DCE, 1,1-dichloroethane and 1,2-

dichloroethane. There are two distinct groundwater plumes (Figure 2). One of the groundwater

plumes originated from Drum Burial Area 1 and is located to the west of Hunterstown Road.

The other groundwater plume, located east of Hunterstown Road, originated from all the other

disposal areas on the Shealer property.

B. Selected Remedy

EPA issued the 1993 ROD selecting a remedy for the Site. The remedy for the Site was

modified by the 1998 ESD, 2001 ESD, and 2003 ESD. Although Remedial Action Objectives

were not specifically identified, the ROD states that the implementation of this remedy would

effectively eliminate the potential risk to human health which may result from exposure to

contaminated groundwater, soils and sediments from the Site.

The Selected Remedy consists of the following components:

• Extraction of contaminated groundwater above 800 feet below ground surface;

• Treatment of extracted groundwater via an air stripper with the off-gases treated utilizing

vapor-phase carbon adsorption;

• Discharge of the treated water to an on-site stream, in compliance with National Pollutant

Discharge Elimination System limits;

• Excavation, treatment and disposal of at least 2 feet of soil and backfilled with a soil

cover and re-seeding at the Former Lagoon and Stressed Vegetation Areas;

• Installation of a soil cover over a geotextile liner and subsequent revegetation to prevent

contact with contaminated soils at the North and South Cornfields and Borrow Area;

• Soil cover extended over contaminated soils between the Lagoon Area, Stressed

Vegetation Area and on-site stream (referred to as East Stream);

• A deed restriction for the Shealer property, restricting groundwater use and protecting the

soil covers;• Excavation, treatment and off-Site disposal of contaminated sediments;

• Replacement of wetlands destroyed as part of the remedial action; and

• A Technical Impracticability (TI) Waiver.

There is no soil component of the remedy for the Drum Burial Areas because these areas were

remediated as part of the removal actions before the ROD was issued.

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The groundwater performance goals selected by EPA in the 1993 ROD were “background levels

of contamination,” practically defined as no detection of VOCs using method EPA 524.2

Practical Quantitation Limits. For groundwater deeper than 800 feet below ground surface, EPA

issued a TI Waiver because of the complexity of the geology and the probable presence of dense

non-aqueous phase liquids in fractured bedrock at extreme depths. The TI Waiver waived the

requirement to meet the following ARARs: “background levels of contamination,” MCLs, and

non-zero MCLGs deeper than 800 feet below ground surface.

C. Remedy Implementation

In 2001, the soil and sediment excavation activities, with on-Site treatment and off-Site disposal,

were completed. During excavation buried drums were removed from the Former Lagoon and

were sent off-Site for disposal. All capped soils are located within a fenced-in area, which was

completed in 2001. The wetland, restoration was completed in 2003. There are three

groundwater extraction wells in each plume. The groundwater is pumped from the extraction

wells to a treatment system located adjacent to the capped soils. The groundwater is treated by a

shallow-tray air stripper system with the off-gas treated through carbon adsorption. The effluent

is discharged to an on-Site stream. The extraction and treatment of groundwater has operated

since September 2003. The capped areas, fence, restored wetlands and treatment system

building are shown on Figure 3.

D. Summary of Institutional Controls

In the 1993 ROD, EPA identified the need for ICs at the Site. ICs are non-engineered

instruments, such as administrative and legal controls, that help minimize the potential for

human exposure to contamination and/or protect the integrity of a response action.

The ICs required by the 1993 ROD consist of the following: a deed restriction on the Shealer

property that shall prevent any use of groundwater and use of the property by the owner for

storage or any other purpose that may impact the remedy; and installation of a chain link fence to

surround the Site to protect the soil covers.

The ICs required by the 1993 ROD have been implemented via a Restrictive Covenant, recorded

with the Adams County Recorder of Deeds for parcels 38-G12-10 and 38-G12-39G, on

September 23, 2008.

The Restrictive Covenant grants a permanent right of access over the property for purposes of

implementing, facilitating and monitoring the remedial action and impose activity and use

restrictions on the property that will run with the land. The property land use restrictions in the

Restrictive Covenant prohibit the following: using or extracting groundwater on the property for

any purpose, with the exception of groundwater extracted in connection with the groundwater

remediation systems; interference with the groundwater remediation system; excavation or

disturbance of earth within 50 feet of the groundwater remediation system except with prior

written approval by the PRP; the disturbance or interference to any of the capped areas and

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wetlands; excavation or disturbance of earth within 50 feet of the capped areas and wetlands; and

removing or disturbing the Site fencing constructed on the property.

III. DESCRIPTION OF SIGNIFICANT DIFFERENCES AND THE BASIS FOR

SUCH DIFFERENCES

This Fourth ESD will modify the Selected Remedy as described in detail below:

1. Change in groundwater performance standards:a. Replace natural background performance standards with current MCLs or non­

zero MCLGs; andb. Use Pennsylvania MSCs when there is no MCL or non-zero MCLG.

2. Performance of a cumulative risk assessment once MCLs, non-zero MCLGs and MSCs

are achieved.

3. Implementation of additional ICs:a. Prohibit the installation of new residential supply wells within the entire extent of

the groundwater contaminant plume, without prior written approval from EPA

and PADEP; andb. Prevent damage to the groundwater extraction system piping.

These modifications, collectively, represent a significant change to the Selected Remedy with

respect to scope and performance. The ICs and modified groundwater performance standards

will remain protective of human health and the environment, will comply with Federal and State

requirements that are applicable or relevant and appropriate, and will be cost effective as further

described below.

A. Change in Groundwater Performance Standards

When EPA issued the 1993 ROD, “background levels of contamination” was PADEP’s

groundwater remediation standard required by 25 Pa Code § 264. Subsequent to EPA’s issuance

of the 1993 ROD, Pennsylvania enacted the Pennsylvania Land Recycling and Environmental

Remedial Standards Act, 35 P.S. §§ 6026.101 et seq. (also known as Act 2). Act 2 changed the

PADEP groundwater cleanup standards from background to the Act 2 MSCs. The Act 2 MSCs

are set forth in 25 Pa Code § 250 Appendix A. This change in the Commonwealth cleanup

standard necessitates a change to the chemical-specific ARARs listed in the 1993 ROD. The

revised chemical-specific ARARs are included in Table 1.

For individual COCs with a non-zero MCLG, the non-zero MCLG will be the performance

standard. For individual COCs where MCLs are available and there is no non-zero MCLG, the

MCLs and the Act 2 MSCs for residential use aquifers are identical. For COCs without MCLs or

non-zero MCLGs, there is an applicable Act 2 MSC standard for residential used aquifers.

Therefore, for COCs with MCLs, the groundwater performance standard will be the MCL. For

COCs without MCLs, the groundwater performance standard will be the Act 2 MSC. The

groundwater performance standards and the associated ARARs on which they are based are

listed in Table 1. The COCs listed in Table 1 are the contaminants that have been detected above

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an MCL, non-zero MCLG or MSC in the most recent groundwater sampling event conducted as

part of the long-term monitoring of.the the Selected Remedy.

B. Performance of a Cumulative Risk Assessment

Due to the presence of multiple COCs at the Site, once the performance standards for each COC

has been achieved, the groundwater may nonetheless present an unacceptable cumulative risk.

Therefore, this Fourth ESD also adds the requirement for a cumulative risk evaluation of the

groundwater after MCLs, non-zero MCLGs and MSCs, as applicable, have been met. The

cumulative risk evaluation will take into account risks posed by all Site-related COCs in

accordance with the NCP in 40 C.F.R § 300.430(e)(2)(i), with specific reference to

§ 300.430(e)(2)(i)(A) and (D). The Selected Remedy, as modified by this Fourth ESD, shall

continue to be implemented until the cumulative risk evaluation indicates that the cancer risk

posed by the groundwater COCs is at or below the lxl 0”4 risk level and the non-cancer hazard

posed by the groundwater COCs is less than or equal to a hazard index of 1. The hazard index is

comprised of the sum of the chemical-specific, target-organ-specific hazard quotients for the

contaminants. The list of Site-related COCs is included as Table 1 of this Fourth ESD.

C. Documentation of Additional Institutional Controls

As documented in the April 4, 2019 Data Summary Report for the Site, the concentration of

VOCs in groundwater exceed their respective MCLs, set forth in the National Primary Drinking

Water Regulations, 40 C.F.R. § 141.61, on parcels of land located adjacent to the Shealer

property. The boundaries of the Shealer property versus the extent of. groundwater

contamination is shown on Figure 2. Piping for the groundwater extraction and treatment system

is located on parcels of land that do not have a restrictive covenant. There is approximately

1,500 feet of piping that is not located on the Shealer property. The piping is located to the west

of the treatment system building and is associated with extraction wells for the groundwater

plume located west of Hunterstown Road. The 1993 ROD did not require ICs on any additional

parcels of land apart from the Shealer property and did not require ICs to protect the physical

structure of the groundwater extraction system.

Additional ICs are necessary at the Site to restrict activities that could interfere with the

groundwater extraction and treatment system and to prohibit exposure to contaminated

groundwater. The ICs shall include restrictions in order to protect the Selected Remedy and

human health and the environment. The additional ICs have been implemented specifically as

follows:

1. Straban Township Ordinance § 135-11 Wells - Prohibits individual or semi-public wells

where a proposed or new structure is within 150 feet of the municipal supplied water

system and public water service is available to that site. Municipal water service lines are

located in vicinity of the Site and any new structure would likely have to be on municipal

supplied water.

2. EPA letter dated July 29, 2019 to Straban Township requesting that all well permits

proposed in designated parcels associated with the Hunterstown Road Superfund Site are

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forwarded to EPA for review to determine whether the proposed well is being installed

within an area of groundwater contamination. Straban Township has agreed to share the

requested well permits with EPA. The area for EPA permit review provided to Straban

Township is called a Well Restriction Area and shown on Figure 2.

a. EPA and PADEP will review any proposed well location(s) to determine whether

a well is likely to be impacted by groundwater contamination from the Site; and

b. EPA and PADEP will recommend whether Straban Township should approve or

disapprove of any proposed well location and, if necessary, recommend an .

alternate well location that is unlikely to be impacted by groundwater

contamination from the Site.

3. PA One Call - Pennsylvania’s Underground Utility Line Protection Law, Act 287, 73

P.S. § 180, requires excavators to call PA One Call prior to commencing excavation

work. Once notified about impending excavation work, PA One Call then notifies the

owner of the facility where the excavation work is to occur. The facility owner is

required to provide the excavator with the location(s) of any underground utility lines and

pipelines. The PRP has registered the Site with PA One Call and would be required to

provide the locations of the groundwater extraction system pipelines to the excavator

prior to the start of any excavation work.

IV. SUPPORT AGENCY COMMENTS

In accordance with 40 C.F.R. § 300.435(c)(2), EPA has consulted with PADEP concerning the

changes to the Selected Remedy in this Fourth ESD. EPA received a letter dated March 2, 2020,

indicating that PADEP concurs with the remedy as amended by this Fourth ESD. This letter of

concurrence can be found in the Administrative Record.

V. STATUTORY DETERMINATIONS

EPA has determined that the modified remedy described in this Fourth ESD complies with the

statutory requirements of Section 121 of CERCLA, 42 U.S.C. § 9621. EPA has determined that

the Selected Remedy, as modified by this Fourth ESD, will remain protective of human health

and the environment, will comply with Federal and State requirements that are applicable or

relevant and appropriate to this remedial action, and will be cost-effective.

VI. PUBLIC PARTICIPATION

As required, EPA will publish a notice of availability and a brief description of this Fourth ESD.

In accordance with CERCLA § 117(d) and NCP § 300.825(a), this Fourth ESD and supporting

information will become part of the Site’s Administrative Record, which is available for review

at the local repository and at EPA Region III office.

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VII. SIGNATURE

This Fourth Explanation of Significant Differences modifies the Selected Remedy set forth in the

ROD and the three ESDs (1998 ESD, 2001 ESD and 2003 ESD) for the Hunterstown Road

Superfund Site, to include additional institutional controls that will restrict the installation of

residential supply wells within the groundwater contamination plume and prevent damage to the

groundwater extraction and treatment system; to modify the groundwater performance standards;

and to require a cumulative risk evaluation after all groundwater performance standards are

reached.

Approved by:

Paul Leonard, Acting Director

Superfund and Emergency Management Division

EPA Region III

Date

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Figure 1 - Site Location

Sources Esri. DeLorme. AND. Tele Atlas. First American. UNEP-WCMC, USGS. DigitalGlobe. GeoEye. i-cubed. USDA. AEX. Getmapping, Aerogrid. IGN. IGPand the GIS User Community.

Legend| | Source Areas

>---- - Fence

oNORTH

Hunterstown Road Superfund SiteStraban Township, Adams County. Pennsylvania

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Figure 2 - Well Restrction Area

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Figure 3 - Site Layout

WaterTreatment Plant

0 250 500 1,000Feet

Sources: Esri. DigitalGlobe, GeoEye, i-cubed. USDA, USGS,

AEX. Getmapping, Aerogrid. IGN, IGP, the GIS User

Community and Adams County

Legend

“1 Wetlands

>—— Fence

| | Capped Areas

Hunterstown Road Superfund Site

Straban Township. Adams County, Pennsylvania

Table 1 — Groundwater Performance Standards for Site-related Contaminants of Concern

(COC)

COC MCL/Non-Zero MCLG MSC

1,1,1 -Trichloroethane

1,1,2-Trichloroethane

200 (ig/L3 gg/L

1,1-Dichloroethane 31 gg/L

1-Dichloroethene 7 gg/L

1,4-Dioxane 6.4 gg/L

cis-1,2-Dichloroethene 70 gg/L

Trichloroethene 5 gg/LVinyl Chloride 2 gg/L

Legend:pg/L - micrograms per liter COC - Contaminant of Concern MCL - Maximum Contaminant Level MCLG - Maximum Contaminant Level Goal MSC - Medium Specific Concentration 1 — Non-zero MCLG

Applicable or Relevant and Appropriate Requirements for Groundwater Performance Standards

1. MCLsand MCLGs - 40 C.F.R. Part 1412. MSCs - 25 Pa Code Section 250 Appendix A

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