By Don Corey
The Hanscom Air Force Base Restoration Advisory Board (RAB) met on September 18, 2012 to hear an annual update of current environmental conditions on the base.
The RAB was established after Hanscom AFB became a Federal Superfund Site in 1994 and is made up of Hanscom personnel, their environmental contractors, U.S. Environmental Protection Agency (EPA) personnel, Massachusetts Department of Environmental Protection (DEP) personnel, Town of Bedford representatives, and local citizens.
After a number of releases of hazardous substances to soil and groundwater were detected at the base, cleanup of many sites began in the 1980s. The majority of the restoration program sites have been cleaned up and closed out, with concurrence of the regulatory agencies.
However, eight of the sites have required long-term monitoring and management; six of those sites that deal with hazardous substances are subject to EPA oversight, and two that deal with petroleum releases are subject to DEP oversight. In all cases, the on-going remedial actions are intended to protect human health and the environment. Exposure pathways that could result in unacceptable risks (such as contact with contaminated soil or ingestion of contaminated groundwater) are being controlled until a permanent solution is achieved.
Sites where long-term monitoring and/or remedial actions are continuing include the following:
Site 1 – Fire training area located at the north end of the airfield in Bedford;
Site 2 – Paint waste disposal area in the northeast area of the airfield in Bedford;
Site 3 – Jet fuel residue/ tank sludge area in the western end of the airfield in Concord.
All wastes and contaminated soil were removed from these sites in 1988, and a groundwater collection and treatment system has been in operation since then to collect and treat contaminated groundwater and to prevent its migration off of the airfield complex. A long-term groundwater and surface water monitoring program is in place to ensure that contaminated groundwater is being contained and captured at the Hanscom Field boundary.
Site 4 – Former base municipal waste landfill located in Lincoln and Concord off of
An impervious cap was placed over the landfill in 1988. A long-term inspection and maintenance program was instituted to ensure that the installed cap and berms provide continued protection.
Site 6 – Former filter beds and landfill located in Bedford and Lexington.
Remedial actions completed in 2001 included containment and capping of three landfill areas, removal of contaminated sediment and debris from adjacent properties, long-term monitoring and institutional controls (to prevent contact with or use of the soil and groundwater). This also required restoration of wetlands adjacent to this site. A long-term inspection and maintenance program was also instituted in this area to ensure continued protection. An on-going issue at this site involves periodic spikes in dissolved arsenic concentrations in groundwater from several monitoring wells. The arsenic is believed to be either naturally occurring from bedrock or from agricultural applications to orchards, etc., in that area prior to Hanscom AFB’s existence.
Site 21 – Former aviation fueling facility in the northeast portion of Hanscom AFB in
Remedial actions were completed in 2003 that included installation of interceptor trenches with recovery wells; removal of petroleum contaminated soil; use of biodegradation additives to naturally break down remaining petroleum hydrocarbons; and, installation of a network of recovery wells connected to a small groundwater recovery and treatment system. A long-term groundwater and surface water monitoring program is also in effect in this area to ensure containment and natural attenuation of the groundwater contamination.
Site 13 – Military motor pool.
Site 22 – Civilian AAFES Service Station.
A long-term monitoring program is in place to track natural attenuation and eventual clean-up of these 2 sites, which are the ones subject to DEP’s oversight.Releases of gasoline and/or diesel fuel from underground storage tanks or dispenser pumps were detected at both locations. The former underground tanks were replaced, and the contaminated soil has been removed. Oxygen release compounds and oxygen diffusers are being used in wells to enhance and accelerate biodegradation of remaining dissolved petroleum hydrocarbons.
The next Restoration Advisory Board meeting is expected to take place in the fall of 2013.