National Grid’s contractor and Project Team continued to construct the composite 120-foot deep dense non-aqueous phase liquid (DNAPL) Migration Barrier Wall (i.e., jet grouted barrier). The Production Jet Grouted Column Barrier Wall Installation Program was completed at the northern part of the site. The jet grouting contractor and waste management contractor commenced the demobilization of construction equipment and materials. The contractor continued the management of jet grouting derived wastes within the Waste Management Facility (WMF). The WMF, which manages wastes (e.g., soils, cement mix and water) that are generated from jet grouting activities, is operated inside the tent with an active Vapor Management System (VMS). Jet grouting wastes were managed in accordance with NYSDEC approved procedures and wastes were disposed of off-site at a licensed and permitted disposal facility. General maintenance and security activities also continued at the Site. Contractor demobilization of construction equipment and materials commenced. Maintenance of the imported backfill material (i.e., clean fill) stockpile covers 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 30, 2012 through May 6, 2012, six fixed base CAMP units were in operation and measured total volatile organic compounds (TVOC) and particulates (PM10). Fifteen-minute averages for both TVOC and PM10 data remained in the Operational Condition. There were no elevated readings for TVOC or PM10 for this 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 week of May 7, 2012 through May 11, 2012, the final backfill of the jet grouted column sleeves and coreholes is scheduled for completion. The jet grouting contractor will commence the demobilization of the jet grouting equipment. General Site maintenance will be performed and demobilization of construction equipment and materials will continue. Further, the load-out of the jet grouting derived wastes (solids and wastewater) is scheduled to continue throughout the week. Dust suppression activities will be conducted, as necessary. The contractor will perform general maintenance activities and housekeeping at the Site, as necessary.