Construction Update for Briarwood Neighborhood

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 an update on cleanup system construction activities and to inform you of planned fieldwork in the Briarwood neighborhood.

Construction Update:

You are may be aware that the drilling of two extraction wells and trenching/piping activities along Hooppole Road were completed at the beginning of December. The installation of the two extraction wells and piping is associated with the cleanup of the Trichloroethylene (TCE) plume and remaining portions of the Storm Drain-5 South (SD-5S) groundwater plume. As part of this work, overhead electrical utilities at the intersection of Hooppole Road and Highland Avenue were moved from the west side of Hooppole Road to the east side. Six new performance monitoring and evaluation (PME) wells were installed which will monitor the performance of TCE and SD-5S cleanup systems. These activities were coordinated with the Town of Mashpee, representatives of the Briarwood Homeowners Association, the State Division of Fish and Wildlife, local police and the school bus company. Workers will require access to the extraction well vaults on a regular basis to perform routine operation and maintenance work.

Background:

The two extraction wells recently installed on Hooppole Road will pump contaminated groundwater through double-walled pipes to the Sandwich Road Treatment Facility located along Back Road in Mashpee. The clean water will be re-injected into the aquifer through existing wells located near the Sandwich Road Treatment Facility. The system began operating on January 22, 2000, nine days ahead of the enforceable milestone of January 31, 2000.

Six new PME wells were installed in the Briarwood neighborhood. Data collected from PME wells will be used to evaluate the performance of the TCE and SD-5S cleanup system. Two of these PME wells were installed on Highland Street and Hillside Avenue; two on Wheeler Road; one in the parking area of the state-owned boat ramp and one on a private residence located along Hooppole Road (see attached figure). Neighbors located directly adjacent to these PME well locations were notified of this work by hand-delivery of neighborhood notices.

Construction Update:

In early August the recirculating wells were modified so that the same air that is used to remove contaminants from the groundwater is treated and then re-used. This is called a closed air stream loop. Air and water samples are taken from each system regularly to measure VOC concentrations. Samples were collected weekly, then bi-weekly since system startup in mid-June. Samples now will be collected on a monthly basis. Data collected through November 23, 1999, suggests that closing of the air stream loop has not changed the cleanup effectiveness of either recirculating well system. Both systems have continued to operate at approximately 91-94% efficiency (i.e., 91-94% of VOCs are being removed from the air entering the air stripper) after closing the air stream loop. The cleanup system located under Wheeler Road has removed 0.49 pounds of volatile organic compounds (VOCs) from the groundwater. The system under Hillside Avenue has removed 2.2 pounds of VOCs. Both systems have treated a total of approximately 25.6 million gallons of groundwater. Carbon canisters that remove contaminants from the air stream have been replaced twice in both systems since they began operation. Changing the carbon canisters is a normal and regularly scheduled part of operating and maintaining these cleanup systems in order to maintain their effectiveness.

The first performance and monitoring report will be available in late March 2000. After the first report is issued, quarterly reports will be prepared. They will be available at the main libraries in Bourne, Falmouth, Mashpee, and Sandwich. Reports will also be available at the Installation Restoration Office and the US Coast Guard library located on the MMR.

Background:

Two recirculating wells were installed in spring 1999. One is located under Wheeler Road and a second under the corner of Highland Street and Hillside Avenue. Both wells began operating June 17, 1999. In July, air monitoring of the systems detected three VOCs in the air stream within the vault. As soon as these results were received, air monitoring was conducted at the top of the 30-foot air discharge pipe located near each recirculating well. No VOCs were detected at the actual discharge point to the atmosphere. The Massachusetts Department of Public Health reviewed the concentrations of contaminants detected within the vaults. They determined that there would be no human health risk associated with exposure to the concentrations of contaminants detected during air monitoring. However, in order to eliminate any potential exposure, both systems were changed to close the air discharge pipe and re-incorporate the treated air back into the air stream of the treatment system. Closing the air discharge pipe on the system prevents any air discharge from the system and prevents any potential exposure to contaminants present within the air stream of the treatment system. Modifications to both systems were completed August 7, 1999.

Recirculating well technology on which the original AFCEE design was based allowed the treated air stream to discharge to the atmosphere. This configuration had been implemented previously in the United States and shown to be an effective treatment technology. However, the closed loop version of this design had been tried in few locations in other countries. AFCEE preferred installation of the more proven design over one that could not be documented as being state-of-the-art technology at that time. The system was designed so that the less-proven closed system might be installed if needed. Recognizing neighborhood concerns, AFCEE later modified the system, retaining effectiveness.

For more information about this project, please call Douglas C. Karson, AFCEE Community Involvement Specialist, at (508) 968-4678 extension 2.