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. The two foot thick Site Wide Cap and perimeter utility cut and cap excavations continued along the northern part of the Site west of the tunnel entrance and in the northwestern part 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. 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 commenced in the northeast corner of the site and progressed in an east to west direction across the northern part of the Site.  Demolition of concrete continued along the northern part of the site. The demolished concrete was relocated to a staging area in the southwest corner of the site. The initial assembly and construction of the temporary fabric enclosure (tent) framing and ribbing commenced and a part of the tent anchoring system ballast block was set in the southeastern corner of the Site (Tent Location #1). Noise and vibration monitoring activities were conducted during the concrete demolition activities and sheet piling operations.

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 necessary. 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 future 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 16, 2009 through March 20, 2009, sixed base CAMP units and two portable CAMP units were in-use and measured TVOC and PM10. Fifteen-minute averages for TVOC and PM10 data remained in Operational Condition. On Monday, March 16, 2009, intermittent elevated concentrations of dust were reported at FAM-1 and were not associated with ground intrusive activities. These elevated concentrations were caused by regional influences. Weekly Reports of the CAMP data can be found as a separate tab in the Weekly Report Archive section.

For the week of March 23, 2009 through March 27, 2009, perimeter utility cut and cap excavation activities are scheduled to be completed along the northern and northwestern parts of the site with off-site transport and disposal of excavated impacted material at an approved and licensed disposal facility. Utilities exposed during the excavation activities will be identified, surveyed, and decommissioned, as appropriate. Pre-trenching activities for the on-site DNAPL migration barrier wall will be performed and completed concurrently with the northern perimeter utility cut and cap activities. 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 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.