Background

Established in 1961, the US Army Corps of Engineers’ (USACE) Cold Regions Research and Engineering Laboratory (CRREL) in Hanover, New Hampshire has conducted large scale studies in controlled refrigerated environments as one of its primary missions for the nation. Trichloroethylene or TCE was used as a refrigerant for many years in refrigeration systems used to conduct research in cold environments.

1970s and 1980s – Several major spills and leaks of TCE occurred on the CRREL property.  Use of TCE was discontinued as a refrigerant in 1987, and general use of TCE at CRREL no longer occurs.

1990 – TCE was detected in three of four cooling water production wells located on the CRREL site, and in several wells across the Connecticut River in Norwich, Vermont.

Groundwater Investigations and Remediation

1993 – The US Army Environmental Command (USAEC) and the US Army Corps of Engineers New England District (NAE) began operating a continuous groundwater treatment system in accordance with New Hampshire Department of Environmental Services (NHDES) and US Environmental Protection Agency (EPA) policies and guidelines. Investigations of the sources of TCE contamination in the soil and groundwater continued through the 1990s, including pilot tests of in situ treatment of soils using injections of potassium permanganate (KMnO4).

2001 – A draft Remedial Action Plan was submitted to NHDES in 2001.

2003 – NHDES approved a Remedial Action Plan that established a Groundwater Management Zone with treatment of groundwater pumped from the on-site extraction wells, and monitoring requirements to verify that TCE contamination in groundwater was being contained on-site.

2008 – present – Sampling of treated cooling water being discharged to the Connecticut River has shown TCE concentrations to be at or below detection limits.

TCE Vapor Intrusion Detected in CRREL Buildings

2010 – Following Department of Defense (DoD) guidelines, contractors for USACE New England District (NAE) took indoor air samples in several buildings on the CRREL site to determine if TCE vapor was migrating into the buildings. TCE was detected in indoor air in several locations.

2011 – NAE launched a full scale Remedial Investigation/Feasibility Study (RI/FS) for TCE and other potential contaminants in soil, groundwater, bedrock and indoor air on the CRREL site.  A contractor was selected to identify data gaps from previous investigations, and develop a new Remedial Action Plan for the site.

September/October 2011 – TCE was detected in low concentrations in the basement of the Child Development Center (CDC), but not in the upstairs daycare space. A “time-critical removal action” was implemented at the CDC that consisted of a sub-slab depressurization system (SSDS) in the CDC basement to mitigate the potential intrusion of vapor contamination into the building from the subsurface. Other interim and time-critical mitigation measures, including portable room air treatment units and sub-slab depressurization systems, have been implemented in the CRREL Main Lab and other buildings at CRREL to protect the health and safety of workers and visitors by minimizing TCE exposure.

2011- present – Additional comprehensive rounds of groundwater, soil vapor and indoor air testing have been conducted throughout the site. Soil vapor investigations are intended to identify and monitor vapor migration pathways and provide knowledge of potential off-site vapor migration.

2018 – The Final Phase III Remedial Investigation Report was completed.

2019 – The CERCLA investigation was separated into two remedial investigations for the CRREL Main Site and for the Connecticut River and Vermont.

2021 – The Final Feasibility Study for the Main Site was completed in 2021; it is currently under negotiation with NHDES which will result in a FS Addendum.

2022-present – The Draft Final Remedial Investigation Report for the Connecticut River and Vermont was completed and is under review by the Vermont and New Hampshire environmental regulatory agencies.

Continued Operation of the Interim Remedial Actions has Resulted in Significant Decreases in Concentrations of TCE in Soil Gas and Groundwater Both On-Site and Off-Site; There are No Actionable Human Health Risks On-Site or Off-Site.

2012-2022 – Off-site sampling for TCE in soil vapor and indoor air has shown no actionable risk on neighboring properties. When high concentrations of TCE were measured in deep soil samples (25 to 50 feet below ground surface) near the CRREL property boundary, USACE-NAE decided it was necessary to sample buildings on abutting properties to see if TCE vapors were migrating into buildings on neighboring properties. In March 2013, property owners were notified and CRREL was given permission to sample in the Richmond Middle School, Dartmouth Housing rental units, and several neighboring businesses. All samples of indoor air off-site showed concentrations below or very near laboratory detection limits and below applicable health-protective screening levels. This indicates safe conditions with respect to TCE exposure at those places. Soil vapor TCE concentrations were observed to be elevated in the deep vadose zones (> 50 feet) during the initial sampling rounds. Due to implementation of the soil vapor extraction pilot at CRREL, soil vapor TCE concentrations have been significantly reduced.

2013-present – Daily monitoring of the indoor air in CRREL buildings continues using a portable air monitor; an additional stationary indoor air monitoring instrument will be added in the summer of 2024.  Implementation of an Employee TCE Action Plan (updated Sept 2023) has been successful in limiting any unacceptable exposures in the buildings.

Communication with the Public

2013-2014 – In April 2013, prior to off-site sampling, USACE-NAE and CRREL conducted an Open House for the community to explain the ongoing investigation and reason for sampling off-site. A second community Open House was  held on October 22, 2014. USACE-NAE also invited community members to participate on a Restoration Advisory Board (RAB) for the Hanover community.

2014-2022 – The RAB continued to meet bimonthly or quarterly, or more frequently as needed, to discuss the ongoing investigations and sampling results, and to communicate the restoration team’s progress to the Hanover community. 

2022-present – The RAB now meets three times a year in January, May, and September to discuss the ongoing investigations and sampling results, and to communicate the restoration team’s progress to the community. 

The Administrative Record is available for review at the CRREL library (hard copies) and Howe Library in Hanover (digital copies-see the information desk to access the files), and includes all final reports.

For more information, please contact the Project Manager, by e-mail or by calling 978-318-8025.

Updated: August 8, 2024