Checking temporary sheet pile installation for excavation area #2

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 the on-site Waterloo Barrier Wall continued across the northern part of the site.  In addition, installation of temporary sheet piling commenced at the planned Shallow Excavation Area at Tent Position #2 located along the southern part of the site. Record of construction surveys and construction stake-out surveys continued as site remediation activities progress. Shallow Excavation Area remedial activities continued inside the temporary fabric enclosure at Tent Position # 1 in the southeast corner of the site. Vapor Management System (VMS) operation continued at Tent Position # 1 and worker health and safety monitoring activities continued at the site. Noise and vibration monitoring activities were conducted during the on-site barrier wall sheet piling operations (Waterloo DNAPL Migration Barrier Wall) and during Tent Position #2 temporary sheet pile installations.

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 sheet pile for excavation area #2

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 11, 2009 through May 17, 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. During the overnight hours of Saturday, May 16, 2009 between 0615 Hours and 0652 Hours, elevated concentrations of PM-10 particulates were reported at the six fixed base CAMP units. These elevated concentrations for a period of 38 minutes, which were below the Action Limit, were caused by high moisture (high humidity, rain and fog) conditions and were not associated with site intrusive activities. These weather related elevated concentrations diminished when the rain ended. These weather related conditions interfered with the true measurement of PM-10 at the site and background concentrations reduced all elevated concentrations below the action limit; therefore the site remained in the Operational Condition (less than the Action Limit). Weekly Reports of the CAMP data can be found as a separate tab in the Weekly Report Archive section.

For the week of May 18, 2009 through May 22, 2009, temporary sheet pile installation at the proposed Tent Positions #2 and # 3 will continue. National Grid’s remedial construction team is currently studying Waterloo Barrier Wall installation methods and scheduling geotechnical subsurface investigations at the site. Shallow Excavation Area remedial activities including the off-site disposal of impacted soils has been delayed while the National Grid remedial construction team schedules and implements a revision in the type of trucks used.  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.