Weekly Update Ending: May 28, 2010

Site cap ready for gravel

National Grid’s Remediation Contractor continued with site remediation activities, which included the delivery of construction materials, imported backfill material (stone and common fill), as well as construction equipment and supplies. Off-set Tent Position # 10 (Tent Position # 10a) continued to operate in support of the Phase 1b pre-drill operations as part of the on-site 120-foot deep DNAPL Migration Barrier Wall installation in accordance with the NYSDEC-approved Field Change Request, FCR-06. The pre-drill material management system and bentonite slurry mixing system continued to operate in support of the Phase 1b pre-drill operations.  The Phase 1b pre-drill operations continued to progress to the west from the eastern end of the 120-foot deep DNAPL Migration Barrier Wall. Difficult driving conditions were observed during the interlocking steel sheet piling installation efforts along the eastern end of the 120-foot deep DNAPL Migration Barrier Wall. Therefore, the interlocking steel sheet piling and Phase 1b pre-drill activities have been discontinued. Common fill material deliveries and final grading and cap installation activities continued to progress in the central, eastern, and southeastern parts of the Site. Temporary sheet piling continued to be decontaminated in preparation for demobilization from the Site.  National Grid’s consulting engineer conducted noise and vibration monitoring activities, as necessary.

Maintenance of the decontamination areas, work zones, on-site gravel access roads, parking areas and material staging areas, imported backfill material (i.e., clean fill) stockpile covers, the perimeter privacy screen, and soil erosion and sediment control (SESC) measures continued. Odor and dust suppression activities were conducted, as necessary. National Grid’s consulting engineers continued to monitor the site activities with the community air monitoring program (CAMP) equipment.

During the period from May 24, 2010 through May 31, 2010, six fixed base CAMP units and one portable CAMP unit were in-use and measured total volatile organic compounds (TVOC) and particulates (PM10). Fifteen-minute averages for both TVOC and PM10 data remained in the Operational Condition.  No elevated TVOC or PM10 readings were reported for the weekly monitoring period. The Weekly Report that summarizes the CAMP data can be found as a separate tab in the Weekly Report Archive section.

For the holiday week of June 1, 2010 through June 4, 2010, cap material deliveries along with final grading and Cap installation activities are scheduled to continue in the central and eastern parts, and progress toward the southeast corner of the Site.  Site preparations will commence for the installation of the 120-foot deep Composite DNAPL Migration Wall (Phase 3) in accordance with the NYSDEC-approved Field Change Request, FCR-06. Odor and dust suppression activities will be conducted, as necessary.  Work zone delineation, site maintenance activities, CAMP operation monitoring activities as well as noise and vibration monitoring activities will continue.