National Grid’s Remediation Contractor continued with site remediation activities, which included the delivery of construction materials, additional equipment and supplies. The two foot thick Site Wide Cap and perimeter utility cut and cap excavations continued along the western, northwestern, and northern parts of the site. In addition, 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 materials were transported off-site for disposal at approved and licensed disposal facilities. Utility cut and cap activities commenced at the southern end of the tunnel entrance along Beach Channel Drive, which included the exposure of the southern end, utilities cut and cap, and construction of a tunnel entrance closure wall or plug. 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. Installation of temporary steel sheeting continued in the southeast corner of the site in preparation for the assembly and erection of the temporary fabric enclosure in this area (i.e., planned 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 southwest part of the Site for future use as backfill material. Maintenance of the site access roads and parking areas, 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 9, 2009 through March 13, 2009, six fixed 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 March 13, 2009, elevated concentrations of dust were reported for a period of two minutes at PAM-1. These elevated concentrations were caused by a street sweeper and was not associated with ground intrusive activities. Weekly Reports of the CAMP data can be found as a separate tab in the Weekly Report Archive section.

For the week of March 16, 2009 through March 20, 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. In addition, pre-trenching activities for the on-site DNAPL migration barrier wall will be conducted concurrently with the northern perimeter utility cut and cap activities. Utilities exposed during the excavation activities will be identified, surveyed, and decommissioned, as appropriate. Work activities will continue at the tunnel entrance to close off (i.e., plug) the southern end.  Concrete pads along the northern and northwest part of site will be demolished. Demolished concrete selected for reuse will be consolidated in the southwestern area of the Site for future crushing and reuse in accordance with the applicable NYSDEC approvals. Temporary sheet piling installations will continue and the erection of the temporary fabric enclosure base frame and structural members plus preparations for the installation of the vapor management system (VMS) will commence. 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.