Continued installation of Waterloo barrier on north side of site

National Grid’s Remediation Contractor continued with site remediation activities, which included the delivery of construction materials, imported backfill material (clean fill), construction equipment and supplies.   Installation of temporary sheet piling continued at the planned Shallow Excavation Area at Tent Positions #2, #3, and #4.  Record of construction surveys and construction stake-out surveys continued as site remediation activities progress. In addition, maintenance of the temporary fabric enclosure was conducted at Tent Position # 1 in the southeast corner of the Site.  Periodic inspections of the Vapor Management System (VMS) and worker health and safety monitoring activities were conducted as necessary at Tent Position #1 for limited maintenance operations performed within the tent. Noise and vibration monitoring activities were conducted during the on-site temporary sheet piling operations at Tent Positions #2, #3, and #4, and during the preparation of the on-site Waterloo DNAPL Migration Barrier Wall. On-Site Waterloo DNAPL Migration Barrier Wall installations continued along the northern part of the Site.

Personnel and equipment decontamination pads were utilized throughout site operations.  Further delineation of work zones (i.e., exclusion, decontamination, and support) continued, as required. Maintenance of the on-site gravel access roads, parking areas and material staging areas, the imported backfill material (i.e., clean fill) stockpile covers, and the perimeter privacy screen continued.  Imported clean fill materials continued to be staged in the central part of the site and utilized as backfill material for the Tent Position #1 Shallow Excavation Area.   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.

Installation of temporary sheeting to support excavation at south side of site.

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 May 18, 2009 through May 24, 2009, six fixed 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 the Operational Condition. No elevated TVOC and PM10 measurements were reported for the weekly CAMP monitoring period. Weekly Reports of the CAMP data can be found as a separate tab in the Weekly Report Archive section.

For the week of May 25, 2009 through May 29, 2009, National Grid’s remedial construction team is currently studying Waterloo Barrier Wall installation methods and has scheduled a geotechnical subsurface investigation (borings and cone penetrometer tests) at the site. Shallow Excavation Area remedial activities will resume at Tent Position #1 with off-site transport and disposal of impacted soils at the approved and permitted disposal facilities.  Work zone delineation and maintenance of the on-site gravel access roads, truck lining and tarping stations, personal and equipment decontamination pads, and the truck scale will continue. National Grid’s consulting engineer will continue to monitor the site activities with noise and vibration monitoring equipment. Maintenance of engineering controls and SESC measures will continue. Work zone air monitoring and VMS system inspection and performance monitoring will continue.  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.