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.  Tent relocation activities from Tent Position #11 to the next Tent Position (Tent Position #10) were completed. Tent relocation activities included the temporary disassembly and staging of tent anchors and the vapor management system (VMS), temporary removal of the central panel, end panels and access doors, followed by the relocation of the two tent sections and replacement of the central panel, access doors, and end panels.  The temporary fabric enclosure supports, tent anchors, and VMS were reset as the final phase of the tent position relocation.  Tent Position # 10 will be operated to support the Phase 1b pre-drill operations part of the on-site 120-foot deep DNAPL Migration Barrier Wall installation in accordance with the NYSDEC-approved Field Change Request, FCR-06. Common fill material deliveries and final grading and cap installation activities continued to progress in the south-central part of the Site. Phase 1b pre-drill equipment mobilization activities were completed and initial pre-drill operations were performed in accordance with the NYSDEC-approved FCR-06. 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 April 26, 2010 through May 2, 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 except for short-durations on April 29, 2010 and April 30, 2010. On Thursday, April 29, elevated PM10 concentrations were reported for short durations (i.e., less than 30 minutes) at Fixed Air Monitoring Stations 4 (FAM 4) and 5 (FAM5) and on Friday, April 30, 2010 at Station 5 (FAM5). The elevated concentrations were attributable to wind-blown clean fill associated with the Site-Wide Cap construction operations. The elevated levels were immediately mitigated with dust suppression measures (i.e., water truck operations) and PM10 concentrations were quickly reduced to the Operational Condition.   The Weekly Report that summarizes the CAMP data can be found as a separate tab in the “Weekly Report Archive” section.

For the week of May 3, 2010 through May 7, 2010, Tent Position # 10 will be operated to support the Phase 1b pre-drill activities. Phase 1b On-Site 120-foot deep DNAPL Migration Barrier Wall pre-drilling operations (relief / tool shafts) will continue and the sheet pile driving will commence in accordance with the NYSDEC-approved FCR-06.  Cap material deliveries and final grading and cap installation activities are scheduled to continue to progress toward the central part of the Site.  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.