EXPLANATION OF SIGNIFICANT DIFFERENCES

WILLIAMS PROPERTY SUPERFUND SITE

Site Name and Location

Williams Property Superfund SiteMiddle Township, Cape May County, New Jersey

Introduction

This decision document presents an Explanation of Significant Differences (ESD) for theWilliams Property Superfund Site (#NJD980529945), located in Middle Township, New Jersey.

Under Section 117 (c) of the Comprehensive Environmental Response, Compensation, andLiability Act of 1980 42 U.S.C. §9601 et. seq., as amended (CERCLA or Superfund), EPA isrequired to publish an ESD when, after issuance of a Record of Decision (ROD), subsequentenforcement or remedial actions lead to significant, but not fundamental, changes in the selectedsite remedy. Sections 300.435(c)(2)(i) and 300.825(a)(2) of the National Oil and HazardousSubstances Contingency Plan (NCP) set forth the criteria for issuing an ESD and requiring thatan ESD be published if the remedy is modified in a way that differs significantly in either scope,performance, or cost from the remedy selected in the ROD for the site.

- This ESD presents the details of significant differences to the remedy selected in theSeptember 29, 1987 ROD, as once modified by an earlier ESD issued February 11, 1993 for theSite. This ESD provides a brief history of the Site, describes the original remedy, and explainshow, subsequent to the finalization of the decision document, issues concerning the scope oftheselected remedy have been identified for this Site.

This ESD will become part ofthe Administrative Record for the Site (NCP 300.825(a)(2)),which has been developed in accordance with § 113 (k) ofCERCLA, 42 U.S.C. § 9613 (k).

The Administrative Record is available for review at the Cape May County Health Department,Crest Haven Complex, Cape May Court House, New Jersey 08210, and at U.S. EPA Region 2,Administrative Record File Room, 290 Broadway, 18th Floor, New York, New York 10007,Monday - Friday, 9:00 a.m. to 5:00 p.m.

Statement of Purpose

The purpose of this ESD is to document that an institutional control in the form of aClassification Exception Area/Well Restriction Area (CEAlWRA), in accordance with the NewJersey Department of Environmental Protection (NJDEP) regulations, was implemented and is apart ofthe groundwater remedy for the Site. Institutional controls such as a CEAlWRA are non-engineering measures, usually legal controls, intended to limit human activity in such a way as toprevent or reduce exposure to hazardous substances. Although not part of the selected remedy

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for the Site, the CEAlWRA was required by the NJDEP as a permit condition and significantlyreduces the future risk of contaminated groundwater ingestion by potential users in the vicinityof the Site.

Site History and Contamination

Site History

The Site is located on Siegtown Road in Middle Township, Cape May County, New Jersey. It islocated less than three miles southeast of the Timber Beaver Swamp Fish and WildlifeManagement Area, a major aquifer recharge zone, and is bordered by prime wetlands habitats.The nearest surface water is about 400 feet northeast from the Site in the form of water- filledsand and gravel pits. There are no natural surface streams located in the immediate vicinity ofthe Site. The nearest stream is Deep Creek, which is approximately 3,000 feet southeast of theSite.

In August 1979, approximately 150 drums ofliquid chemicals and sludge were emptied on theSite by the property owner (Theodore Williams), adjacent to the Williams residence.

The Site was placed on the National Priorities List in 1983.

Based on the findings ofthe remedial investigation/feasibility study (RIIFS), a ROD was signedon September 29, 1987, for the remediation of the Site soils and groundwater.

Initial Response

In response to the release of the chemicals, the NJDEP undertook extensive investigations todetermine the impact of the spill on the environment, and in particular, on the groundwater.These investigations showed that both the soils and groundwater had been contaminated. As aresult of these findings, NJDEP conducted an emergency cleanup of the spill site in 1980 thatremoved approximately 1,200 cubic yards of soil and sludge.

In 198311984, Middle Township provided public water to approximately 140 homes andbusinesses that were potentially affected by the Site.

Site Contamination

Through a Cooperative Agreement with EPA, the NJDEP completed a RIIFS for the Site in1987. The investigation found a plume of volatile and semi-volatile organic contaminants in thegroundwater beneath the Site emanating from the original spill area and extending at least 600feet downgradient. Some residual soil contamination was also found.

The chemicals of concern (COCs) selected were as follows: bis (2-chloroethyl) ether; bis (2-ethylhexyl) phthalate; methylene chloride; tetrachloroethene; 1,1, I-trichloroethane; total xylenes;cadmium; chromium; lead; and nickel. Subsequent investigatory work conducted during designactivities determined that acetone, 2-butanone (methyl ethyl ketone) {MEK}), and 4-methyl-2-

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pentanone (methyl isobutyl ketone {MIBK}) were also COCs. Some or all of the contaminantsidentified are hazardous substances as defined in § 104(14) ofCERCLA, 42, U.S.C. § 9601(14),and 40 C.F.R. § 302.4.

Groundwater migration is the primary transport pathway for COCs from the Site. Potentiallyexposed populations included downgradient potable well users, although remedial actionssubsequently taken included the connection of local downgradient homes to a public watersupply.

Selected Remedy

On September 29, 1987, a ROD was signed for selection of a remedy to clean up thegroundwater and soil. There is one operable unit at this Site addressing contaminants. Theprimary remedial response objectives of the 1987 ROD include:

.:. mitigation of migration of contaminated groundwater in the Holly Beach Aquifer;

.:. remediation of contaminated groundwater in the Holly Beach Aquifer; and

.:. mitigation of leaching from contaminated Site soils into the groundwater and preventionof direct contact.

The major components of the remedy selected in the 1987 ROD include the following:

.:. extraction and treatment of contaminated groundwater on-site using air stripping toremove volatile organics and carbon adsorption to remove remaining volatile organicsand semi-volatile organics;

.:. recharge of the treated groundwater to the aquifer on-site;

.:. provision of an alternate water supply to residents with individual wells impacted by theSite;

.:. excavation of the contaminated soils above the action level at the original spill area;

.:. removal of the excavated soils to an approved off-site disposal facility for incineration;and,

.:. re-grading the Site with clean fill, re-vegetation and restoration of the Site.

1987 ROD Implementation

The selected remedy in the 1987 ROD was to address organic compounds detected ingroundwater during the RI. In August 1990, NJDEP awarded a design contract for the soilscleanup and completed the design. At the request of the NJDEP, the EPA's removal programcompleted the soil cleanup portion of the remedy in July 1991. The soil cleanup included the

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excavation and removal of approximately 1,500 tons of contaminated soil which was shippedoff-site for treatment and disposal. In addition, EPA removed 55-gallon drums, 5-gallon pails,and gas cylinders from the Site.

In September 1990, the NJDEP completed design field investigations to construct thegroundwater remediation portion of the remedy. The investigations found that the systemoutlined in the ROD had to be modified and, thus, an ESD was issued in 1993.

1993 Explanation a/Significant Differences

The groundwater remediation system required modification because the groundwater was foundto contain significant levels of ketones, such as acetone, 2-butanone (MEK), and 4-methyl-2-pentanone (MIBK), that could not be effectively treated by the air stripping and granularactivated carbon (GAC) system selected in the ROD.

Based on the conclusions of subsequent treatability studies on the groundwater, the remedy wasmodified to exclude air stripping and to include biological treatment for ketone removal. Inaddition to the biological treatment, the modified remedy includes the following treatmentprocesses: hydrogen peroxide to control hydrogen sulfide odors; an iron removal system toprotect the GAC and the re-injection wells from clogging; sulfuric acid to neutralize thegroundwater for re-injection; and ultraviolet light disinfection to prevent bacterial growth in theinjection wells.

The changes did not functionally alter the groundwater remedy.

In February 1993, EPA issued an ESD that provided the rationale for the changes made to thegroundwater remedy discussed above. The remedial design was completed by NJDEP in June1993.

Remedy Implementation

In April 1993, a cooperative agreement with EPA provided funding to the NJDEP for theremediation of the Site's contaminated groundwater.

Construction of the groundwater remediation system was officially completed in September1995 in accordance with the Preliminary Close-Out Report that was signed on September 15,1995. Physical construction had been completed in December 1994, and the system was put intooperation in January 1995. The system is comprised of two groundwater recovery wells, a watertreatment plant that includes biological treatment in sequencing batch reactors, GAC adsorption,and re-injection wells for the treated water. A group of approximately twenty-five monitoringwells and well points used in the investigations is available to monitor the progress of theremediation.

System Operation and Maintenance

The operation, maintenance, and monitoring manual for the Site specifies the procedures for

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operating, inspecting and maintaining the remediation system, and for monitoring the cleanupprogress in the affected aquifer.

The groundwater extraction and treatment system, operating since early 1995, has attainedcomplete hydraulic capture of the plume. By the summer of 2000, sampling showed that muchof the plume of contamination had been remediated and that the cleanup standards for theketones had been met throughout the affected aquifer.

In response, the biological treatment unit was shut down along with the groundwater extractionwell associated with the apparently clean portion of the original plume. Operations continuedusing the remaining extraction well along with water treatment centering on the GAC adsorptionunit.

Approximately 279 million gallons of contaminated groundwater have been extracted, treatedand re-injected to the aquifer. Reviews of ongoing monitoring results show that the remainder ofthe plume was more difficult to clean. The concentrations of trichloroethylene (TCE) and 1,4-dioxane have decreased more slowly with time toward its respective New Jersey Ground WaterQuality Criteria (NJGWQC) of 1 part per billion (ppb) for TCE and 0.4 ppb for l,4-dioxane. Afew semi-volatile tentatively identified compounds (TICs) were found at levels that required there-starting of operations (after a planned shutdown of the treatment plant) for control of theplume.

2011 Five-Year Review

Monitoring data collected by NJDEP during this five-year review period showed thatconcentrations of the primary Site contaminants remaining in the groundwater met State andFederal standards, with the exception of TCE, which was detected at a low concentration of2.7ppb in monitoring well OP-9l-1B. The NJGWQC for TCE is 1 ppb. The data also indicated thatl,4-dioxane concentrations in groundwater from several wells exceed the NJGWQC level of 10ppb (which has since been revised to 0.4 ppb). However, monitoring data collected by NJDEPduring this five-year review period indicate that the concentrations of l,4-dioxane have generallytrended downward from concentrations in the 25 ppb to 35 ppb range to concentrations in the 15ppb to 20 ppb range. The groundwater sample collected for the 2011 five-year review at thefurthest downgradient monitoring well location (MW-13B) did not detect l,4-dioxane.

Compounds that were tentatively identified as unknown semi-volatile chloro-organic phosphateswere detected in some wells at levels that exceed the NJGWQC of 100 ppb for individualsynthetic organic compounds and 500 ppb for total synthetic organics. EPA's National ExposureResearch Laboratory subsequently conducted an extensive effort to identify the TICs andconcluded that they were mainly comprised of isomers of tris (l-chloro-2-isopropyl) phosphate(TCPP), a flame retardant.

NJDEP's Office of Science undertook an effort to derive a site-specific health-basedgroundwater concentration for TCPP in 2010. NJDEP concluded that there was a high degree ofuncertainty in the toxicological database for TCPP and therefore, a specific health-basedgroundwater concentration was not recommended. A generic groundwater criterion for

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chemicals with no evidence of carcinogenicity of 100 ppb was recommended for TCPP.

A review of TIC groundwater concentration data obtained during the 2010 five-year reviewperiod indicated that concentrations have declined over time. The groundwater data from thelatest monitoring event indicates the concentrations of TICs were at levels below the NJGWQC.

The five-year review did not identify any issue or make any recommendation for the protectionof human health and/or the environment which was not included or anticipated by the Sitedecision documents. There were no recommendations or follow-up actions associated with thisreview. The next five-year review will be completed in 2016.

Description of Significant Differences and Basis for the ESD

A CEAlWRA was not included in the 1987 ROD or 1993 ESD but was required by NJDEP as apart of the permit equivalency for the injection of groundwater that was treated in connectionwith the 1987 ROD. The CEA/WRA for the Site was established in 1999. A CEA/WRA servesas an institutional control by providing notice that there is groundwater pollution in a localizedarea caused by a discharge at a contaminated site. Because the CEA/WRA prevents watersupply wells from being drilled within the designated CEA/WRA area, its incorporation as acomponent of the Site remedy provides additional long-term protectiveness until groundwaterstandards are achieved. A full description of the CEA/WRA requirements is found in the NewJersey Administrative Code in Section 7:26E-8.3.

Support Agency Comments

EPA consulted with the NJDEP and provided it the opportunity to comment on this ESD inaccordance with NCP § 300.435 (c)(2) and § 300.435 (c)(2)(i) and CERCLA § 121(f). TheNJDEP concurred with this ESD in correspondence dated April 20, 2016.

Statutory Determination

EPA has determined that these significant changes comply with the statutory requirements ofCERCLA § 121,42 U.S.C. § 9621, are protective of human health and the environment, complywith Federal and State requirements that are applicable or relevant and appropriate to theremedial action, are cost-effective, and utilize permanent solutions and alternative treatmenttechnologies to the maximum extent practicable.

Public Participation

The public participation requirements set out in the NCP § 300.435(c)(2) have been met bypublishing this ESD, making it available to the public in the Administrative Record, andpublishing a notice summarizing the ESD in a major local newspaper.

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Authorizing Signature

I have determined that the remedy for the Site, as modified by this ESD, is protective of humanhealth and the environment, and will remain so provided the actions presented in this report areimplemented as described above. This ESD documents the significant changes related to theremedy at the Site.

EPA selected these changes with the concurrence of New Jersey Department of EnvironmentalProtection.

By . enr:¥Walter E. Mugdan, D rectorEmergency and Remedial Response Division

Date:

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