March 1, 2001
NEIGHBORHOOD NOTICE

Dear Resident,

The Air Force Center for Environmental Excellence (AFCEE) is committed to protecting public health. As part of this commitment, we wish to provide you with an update on the cleanup system operations in your neighborhood.

Since June 1999, two recirculating well treatment systems, located below Hillside Avenue and Wheeler Road, have been cleaning contaminated groundwater from the Storm Drain 5 South (SD-5S) groundwater plume. Through the end of December 2000, both recirculating wells have treated a total of 84 million gallons of groundwater. In response to neighborhood concerns, modifications were made in 1999 to both systems. These modifications eliminated the discharge of air from the systems to the ambient air outside of each vault. Subsequent monthly air and water samples collected from each system indicated they were operating efficiently with the modifications. Therefore, vent pipes and associated support poles were removed in August 2000.

The greatest concentration of trichloroethylene (TCE) detected in groundwater being treated at the Hillside Avenue treatment system was 22.0 parts per billion (ppb) when it first started operating in June 1999. Measured TCE concentrations have decreased over time, but currently are detectable in water samples collected from the system above the TCE Maximum Contaminant Level (MCL) of 5 ppb. The MCL is the maximum concentration of a given contaminant allowed in drinking water under the federal Safe Drinking Water Act. The Hillside Avenue system currently treats 60 gallons of contaminated groundwater per minute.

The greatest concentration of TCE detected in groundwater being treated at the Wheeler Road recirculating well treatment system was 14.1 ppb when it first started operating in June 1999. TCE concentrations detected in samples collected from the system have decreased over time and since August 2000 have not been detectable when analyzed. Since July 1999, no detections of TCE above its MCL (5 ppb) have been measured in samples collected from groundwater monitoring wells located upgradient (the area from which groundwater flows) of the Wheeler Road system. In addition, no contaminants have been detected in samples collected from groundwater monitoring wells located immediately downgradient (the area toward which groundwater flows) of the Wheeler Road system since December 1999.

Based on the information above, AFCEE recommended to the U.S. Environmental Protection Agency (EPA) and the Massachusetts Department of Environmental Protection (DEP) in mid-December 2000 that the Wheeler Road recirculating well treatment system be shut down temporarily. At that time, AFCEE also recommended sampling additional groundwater monitoring wells near the Wheeler Road area. On December 28, 2000, the Wheeler Road treatment system stopped operating because of a mechanical failure. AFCEE decided not to repair the well due to its recommendation to shut down the well temporarily. EPA and MassDEP reviewed AFCEE’s proposal and agreed to keep the well temporarily shut down.

Chemical Spill 10 and Storm Drain 5 South Treatment System Update

Two extraction wells, located on Hooppole Road, are associated with cleaning up portions of the Chemical Spill 10 (CS-10) groundwater plume and the remaining portions of the SD-5S groundwater plume not being cleaned up by the recirculating well treatment systems. Together, the two extraction wells continue to pump 175 gallons per minute of contaminated groundwater through double-walled pipes to the Sandwich Road Treatment Plant. The clean water is returned to the aquifer using re-injection wells located near the plant.

As of January 1, 2001, a total of approximately 81.5 million gallons of groundwater have been pumped since the wells began operating on January 22, 2000. Workers will continue requiring access to extraction well vaults on a periodic basis to perform routine operation and maintenance work. Based on direction from the Mashpee Department of Public Works, Hooppole Road will be re-paved this year.

Chemical Spill-10 Investigation Update

During the 2000 summer season, six additional groundwater monitoring wells were installed along Hooppole Road. This work was performed as part of the continuing CS-10 investigative work. The data collected from these monitoring wells helped engineers determine the location for two additional monitoring wells installed east of Johns Pond in October and November 2000. These eight additional wells helped identify the leading edge of the CS-10 groundwater plume. The results of that CS-10 investigative work will be presented at informational meetings to be held this spring and summer. Meetings will be held in an informal poster board setting, allowing for direct interaction with AFCEE project managers, and program engineers and scientists.