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EPA Finds Cleanup to be Effective at Tinkham Garage Superfund Site in Londonderry, NH

Release Date: 05/05/04
Contact Information: Contact: Alice Kaufman, EPA Community Involvement Office, (617) 918-1064

For Immediate Release: May 5, 2004; Release # 04-05-04

Boston--The United States Environmental Protection Agency recently confirmed that the soil and groundwater remedies in place at the 375-acre Tinkham Garage Superfund Site in Londonderry, New Hampshire continue to be effective and protective of human health.

The study, called a five-year review, is a comprehensive evaluation of the ongoing cleanup being undertaken at the site. This is the second five-year review of the site.

Illegal dumping activities in the late 1970’s caused contamination of soil and groundwater with volatile organic compounds (VOCs), which are typically found in cleaning solvents. VOCs not only contaminated an approximate one-acre area of soils, but also leached into groundwater and migrated to nearby drinking water wells. EPA responded by installing a public water supply system to provide clean water to impacted residents along Mercury and McAllister Drives and the Woodland Village condominium complex. This system remains intact and will be expanded as future development occurs.

EPA also undertook a comprehensive investigation of the site to determine the nature and extent of all contaminants at the site. A cleanup plan was issued in 1989, which called for active treatment of soil and groundwater. The cleanup plan was modified in 1992 to incorporate a new soil treatment method at the time.

The cleanup began in 1994 and included extracting and treating VOC vapors from the soil. Contaminated groundwater was also extracted through a series of bedrock and shallow wells and then pre-treated on-site before being pumped to the Derry publicly owned treatment works (POTW) for final treatment. The soil cleanup was successfully completed in 1995. Groundwater extraction was discontinued from the bedrock wells in 1996 and from the shallow wells in 2001. EPA issued a modified cleanup plan in 2003 to formally announce that natural attenuation had replaced active extraction of VOCs from groundwater.

Extension of the public water supply system, cleanup of the source soils, and groundwater extraction and ongoing natural attenuation have greatly reduced contaminant levels in groundwater and have allowed for safe reuse of the site property. A New Hampshire groundwater management permit and deed restriction also ensures that wells within the affected area will not be used for drinking water purposes. Tinkham’s Garage, one of the first sites added to the national Superfund list in September 1983, is now home to one of the region’s newest Home Depots, Staples and a “99 Restaurant” all recently opened on the northern corner of the site. Additionally, construction is underway on approximately 125 units of mature housing over a large area of the site.

The five-year review included interviews with responsible parties (those funding the cleanup), a site visit by EPA and NH DES officials, and a comprehensive review of all site-related records and reports, as well as updated toxicity information.

In EPA’s five-year review report, the agency concludes that the soil and groundwater remedies at the site remain protective of public health and the environment. The report confirms that the groundwater will continue to be monitored on a regular basis until the aquifer is again safe to drink (about 15 years).

Because recent EPA guidance suggests that vapors from certain VOCs can migrate into structures through cracks in basement walls or slabs, the report also recommends expansion of the monitoring program to assess the potential impact of vapors from the VOCs. All new residential construction will include proper ventilation as a precaution to prevent possible inhalation of vapors.

More information about cleanup activities at the site may be found on the EPA New England web site at: EPA technical reports and documents are available for public review in the site information repository located in the Leach Public Library in Londonderry, New Hampshire.

Related Information:
Tinkham Garage Fact Sheet
Superfund in New England