National Grid’s Remediation Contractor continued with site remediation activities, which included the delivery of construction materials, imported backfill materials, additional earthwork equipment and supplies. Perimeter utility cut and cap excavations were completed along the northwestern perimeter of the site. Pre-trenching activities for the on-site DNAPL migration barrier wall were conducted concurrently with the northern perimeter utility cut and cap activities. Under the NYSDEC-approved 100% Remedial Design Report for the Site this work does not require a protective covering (i.e., tent) during the excavations and trenching. Utilities exposed during the operation were identified and marked to be subsequently surveyed and decommissioned, as appropriate. The excavated impacted materials were transported off-site for disposal at approved and licensed disposal facilities. Installation of the on-site Waterloo Barrier Wall continued in the northeast corner of the site and progressed in an east to west direction across the northern part of the Site. The assembly and construction of the temporary fabric enclosure (tent) framing and ribbing continued at the Site (Tent Location #1). Noise and vibration monitoring activities were conducted during the sheet piling operations of the on-site barrier wall (Waterloo DNAPL Migration Barrier Wall).
The personnel and equipment decontamination pads were utilized throughout the site operations. Further delineation of work zones (i.e., exclusion, decontamination, and support) continued, as required. Maintenance of the interior access roads, parking areas, staging area, and upgrade of the imported backfill material (i.e., clean fill) stockpile covers continued. Imported clean fill materials were removed from the stockpile located at the staging area in the southwest corner of the site and used as backfill for the perimeter utility cut and cap excavations. Imported clean fill material was delivered and staged in the central part of the site for use as backfill material. Maintenance of engineering controls and soil erosion and sediment control (SESC) measures continued. Odor and dust suppression activities were conducted as necessary. National Grid’s consulting engineer continued to monitor the site activities with the fixed base community air monitoring program (CAMP) equipment.
CAMP data is reviewed and compared to specific NYSDEC/NYSDOH approved criteria, known as “Action Limits.” As a result of this evaluation process, site conditions are categorized into two categories, “Operational Condition” and “Action Condition.” The “Operational Condition” is applicable when the data is below the “Action Limits”, and means that normal operations can continue. The “Action Condition” occurs when one or more of the fifteen minute average measurements for Dust (PM10), Total Volatile Organic Compounds (TVOC), Naphthalene or Odor Intensity are greater than the background or upwind measurement by the specified “Action Limits.” Reaching an Action Level requires corrective action or stopping work until the condition is addressed or abates. During the period from March 23, 2009 through March 27, 2009, sixed base CAMP units and one portable CAMP unit were in-use and measured TVOC and PM10. Fifteen-minute averages for TVOC and PM10 data remained in Operational Condition. No elevated readings for TVOC or PM10 were reported during the weekly monitoring period. Weekly Reports of the CAMP data can be found as a separate tab in the Weekly Report Archive section.
On March 27, 2009, National Grid and NYSDEC participated in a community outreach meeting at which company representatives and representatives of the NYSDEC discussed the commencement of the site remedial actions and obtained community input on a number of issues.
For the week of March 30, 2009 through April 3, 2009, installation of the on-site Waterloo Barrier Wall will continue from east to west across the northern part of the Site. Work activities will continue at the tunnel entrance to close off (i.e., plug) the southern end. Erection of the temporary fabric enclosure base frame and structural members, panels, plus preparations for the installation of the vapor management system (VMS) will continue. National Grid’s consulting engineer will continue to monitor the site activities with noise and vibration monitoring equipment. Odor and dust suppression activities will be conducted as necessary. National Grid’s consulting engineer will continue to monitor the site activities with CAMP equipment.