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SUPERFUND SITE PRELIMINARY CLOSE OUT REPORT

Holton Circle Groundwater Contamination Superfund Site Londonderry, New Hampshire

September 30, 1992I. INTRODUCTION

This Preliminary Close Out Report documents that the Environmental Protection Agency (EPA) has issued a Limited Action Record of Decision for the Holton Circle Groundwater Contamination Superfund Site in Londonderry, New Hampshire. Limited Action RODs require no construction activities, therefore a pre-final inspection is not necessary. Activities required to attain site completion are underway.

II. SUMMARY OF SITE CONDITIONS Background The Holton Circle Groundwater Contamination Superfund Site includes a residential development of 23 homes (Holton Circle), the Londonderry Town Garage area located approximately 1/4 mile west of Holton Circle on High Range Road, and an undeveloped hill slope and wetland area between the Town Garage and Holton Circle which, in total, comprise approximately 100 acres of land in Londonderry, New Hampshire (see enclosed Site Location Map). The property where the Town Garage is located was previously owned by the United States Department of Defense and used as a radio beacon facility. Because of their current ownership of the property, the Town of Londonderry has been named as the only PRP, to date, at the Site. Excluding the Town Garage, land use in the immediate Site area is strictly residential. Drinking water in the area is obtained via private bedrock wells except for nine residents on Holton Circle and the residents of the adjacent Isabella Drive development, all of whom use public water from the Southern New Hampshire Water Company which was installed during 1989 and 1990. The only health threat which exists at the site is from the future ingestion of contaminated groundwater. The primary contaminants of concern at the site are 1,1 dichloroethene (DCE), 1,1,1 trichloroethane (TCA) and several inorganics including chromium (total), barium, beryllium, and antimony. The Site was proposed to the National Priorities List (NPL) on June 21, 1988, and was added to the final list on March 31, 1989. Selected Remedy On September 30, 1992, the Regional Administrator signed a Record of Decision (ROD) for the Site which specified the following remedy:
1. restoration of contaminated groundwater in the overburden and bedrock aquifers by natural attenuation;2

2. institutional controls to prevent ingestion of contaminated groundwater; 3. groundwater monitoring. The goal of the selected remedy is to restore contaminated groundwater to its beneficial uses in 2 to 3 years in the overburden aquifer and 7 to 25 years in the bedrock aquifer. The selected remedy includes no construction activities. Interim Groundwater Cleanup levels, as summarized in Table 1 below, were established for 1,1 DCE, 1,1,1 TCA, chromium, barium, beryllium and antimony.

TABLE I: INTERIM GROUNDWATER CLEANUP LEVELS
Carcinogenic Contaminants

of Concern Interim Cleanup Level (ug/l) Basis

Beryllium 4 MCLG 1,1 Dichloroethene 7 MCLG

Non-Carcinogenic Contaminants of Concern Interim Cleanup Level(ug/1) Basis

Antimony 6 MCLG Barium 2000 MCLG Beryllium 4 MCLG Chromium 100 MCLG 1,1 Dichloroethene 7 MCLG 1,1,1 Trichloroethane 200 MCLG

• micrograms per liter (ug/l) = parts per billion (ppb)
At the time that these Interim Groundwater Cleanup Levels have been achieved and have not been exceeded for a period of three consecutive years, a risk assessment will be performed to determine whether the remedial action is protective. The risk assessment will follow EPA procedures and will assess the cumulative carcinogenic and non-carcinogenic risks posed by ingestion of groundwater.3

If, after review of the risk assessment, the remedial action is determined by EPA to not be protective for unrestricted uses, the remedial action shall continue until either protective levels are achieved and not exceeded for a period of three consecutive years, or until the remedy is otherwise deemed protective. These protective residual levels shall constitute the final cleanup levels for the site. OSWER guidance 9355.7-02 states that five-year reviews will be conducted at sites where cleanup levels will take five or more years to achieve (policy review). Therefore, five-year reviews will be required during this natural attenuation activity.

III. DEMONSTRATION OF QA/QC FROM CLEANUP ACTIVITIES EPA and State Quality Assurance/Quality Control (QA/QC) procedures will be followed during implementation of the monitoring program. Only EPA analytical methods will be used for all validation and monitoring samples. The QA/QC program to be utilized throughout the monitoring program will be sufficiently rigorous and adequately complied with to enable EPA and the State to determine that all analytical results reported are accurate to the degree needed to assure satisfactory execution of the monitoring program consistent with the ROD.

IV. ACTIVITIES AND SCHEDULE FOR SITE COMPLETION The following activities will be completed according to the schedule in Table II below:

TABLE II: SCHEDULE FOR SITE COMPLETION. Task Estimated

Completion Responsible Organization 1. Implementation of institutional controls June 1993 EPA and/or PRP

2. Final inspection September 2022 EPA/STATE/PRP 3. RA Report/Approval September 2022 EPA/STATE/PRP 4. Final Close Out Report December 2022 EPA All preliminary completion requirements for the Site have been met as specified in OSWER Directive 9320.2-3C. Specifically, there are no construction activities at the Site and therefore, no pre-final inspection is necessary.4

A bibliography of all reports relevant to the preliminary completion of this Site under the Superfund program is attached. These documents are available for review by calling the Region 1 office at (617) 573-5729.
Approved By:

Merrill S. Hohman Division Director Waste Management Division• 453 / • • • •

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HOLTON CIRCLE 394 'LondoncLer y \\* ..\.. 1 1 \ Londond erry • •

Moose Hill'

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0 SCALE IN FEET Source: USGS Topographic Maps: Nashua North, NH 1968, Photorevised 1985 Manchester South, NH 1968, Photorevised 1985 Deny, NH 1968, Photorevised 1985 Windham, NH 1953, Photorevised 1985 (-\ 2000 2000

FIGURE 1-1. LOCATION MAP, HOLTON CIRCLE, LONDONDERRY, NEW HAMPSHIRE

1 -1 ••1iC•L n FOO•REFERENCES

Metcalf & Eddy, "Remedial Investigation - Holton Circle Groundwater Contamination Site", March 1992. Metcalf & Eddy, "Feasibility Study - Holton Circle Groundwater Contamination Site", June 1992. United States Environmental Protection Agency, "Record of Decision for the Holton Circle Groundwater Contamination Site", September 1992. United States Environmental Protection Agency, "Procedures for Completion and Deletion of National Priorities List Sites - OSWER Directive 9320.2-3A", April 1989. United States Environmental Protection Agency, "Update to the Procedures for Completion and Deletion of National Priorities List Sites - OSWER Directive 9320.2-3B", December 29, 1990. United States Environmental Protection Agency, "Update No. 2 to the Procedures for Completion and Deletion of National Priorities List Sites - OSWER Directive 9320.2-3C", February 19, 1992.SUBJECT: Holton Circle Close-Out Report

FROM: Jo Ann Griffith

Design and Constr & tion Managem Branch UNITED STATES ENVIRONMENTAL PROTECTION AGENCY

WASHINGTON, D.C. 20460

SEP 25 092

OFFICE OF SOLID WASTE AND EMERGENCY RESPONSE

MEMORANDUM

TO: Jim DiLorenzo

RPM, Region 1
Thank you for allowing me the opportunity to review the Holton Circle Preliminary Close-Out Report. Based on my review, I have the following comments:
Cover: The NCP specifies groundwater restoration as long-term

remedial actions. OGC (larry Starfield) has informed me that this applies only to active measures such as pump and treat and not natural attenuation. It has to do with the state cost share provisions. Page 2: In Table 1, you provide the interim clean-up goals and

the associated cancer and non-cancer risks. You may want to provide the EPA acceptable risk levels for comparison. Page 3: Just an editorial comment here. The first sentence on

the page is a little long and convoluted. In that same and the next sentence, the you say that at the point the interim goals are met, a risk assessment will be performed to "determine whether the remedial action is protective." The site is already protective with the use of institutional controls. What you mean to say, is that if the clean-up goals are no longer protective for unrestricted use, then the remedial action will continue. Five-year reviews will be required during this natural attenuation activity. In the OSWER guidance 9355.7-02, where the clean-up levels will take five or more years to achieve (policy review).



### 46 Printed on Recycled Paper-2- You may want to make a statement to that effect in the text. It will also need to be listed in the schedule of activities, with completion dates. We need a copy of the signed report as soon as possible. It must be faxed or pouched (new mail code is 5203G). Please call me if necessary to discuss my comments. My phone number is (703) 603-8774.