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Stantec Consulting Corporation <br /> 3017 Kilgore Road <br /> Rancho Cordova CA 95670 <br /> Tel:(916)861-0400 <br /> Fax:(916)861-0430 <br /> Rantec <br /> August 13, 2009 <br /> Michael lnfura /L <br /> San Joaquin Environmental Health Department <br /> l <br /> o� <br /> 304 East Webber Avenue, 3ro Floor <br /> Stockton, California 95202 <br /> �J`r�6��Q,GrA <br /> RE: Additional Work at PG&E French Camp Site <br /> PG&E General Construction Yard <br /> 401 French Camp Road <br /> French Camp, California <br /> Dear Mr. Infurna, <br /> Per our recent electronic correspondence, Stantec Consulting Corporation (Stantec) intends to <br /> conduct additional soil investigation activities at the Pacific Gas & Electric Company (PG&E) <br /> General-,G truction Yard located at 401 East French Camp Road in French Camp, California. <br /> Field activities are currently scheduled for Friday, August 14, 2009. All drilling activities will be <br /> performed by Gregg Drilling and Testing. Ms. Kristi Shelton of the Central Valley Regional Water <br /> Quality Control Board has approved the collection of additional data at the site to support a risk <br /> assessment and derivation of site-specific cleanup goals. <br /> Stantec will advance four (4) direct-push soil borings directly adjacent to soil borings advanced at <br /> the site on June 6, 2009. Proposed soil boring locations are illustrated on the attached figure. Soil <br /> borings SB-5A, SB-7A, SB-8A, and SB-10A will be advanced to approximately 20 feet below <br /> ground surface (bgs) for examination of soils and collection of soil samples. Boreholes will be <br /> abandoned using neat cement grout. p" ,lei ,,� 4 4J 'C" -COC <br /> In addition, Stantec proposes installing three(3)semi-permanent soil gas sampling probes,the <br /> proposed locations of which are illustrated on the attached figure. Each soil gas sampling probe will <br /> have two completed sampling intervals, at 5 and 12 feet below ground surface. <br /> Soil vapor sampling points will be installed using a truck-mounted direct-push drilling rig. A steel <br /> rod and sampling tool will be driven to a depth of approximately 12 feet 6 inches below ground <br /> surface(bgs). Following removal of the tool string,the borehole will be filled with approximately 6 <br /> inches of No. 3 sand to provide a base for the sampling implant.The 1.5-inch sampling implant is <br /> perforated to allow the flow of soil vapor into the collection point. The implant will be fitted to the <br /> end of a new section of Y4-inch-diameter Nylaflow tubing that will be installed in the open borehole. <br /> While resting the sampling point on the bedding sand and holding the tubing in the approximate <br /> center of the borehole, the annular space around the implant and tubing will be filled with sand to <br /> approximately 6 inches above the implant, creating an approximate 124nch-thick sand pack from <br /> which to draw the vapor sample. <br /> The remaining annular space will be backfilled using hydrated bentonite installed in six-inch lifts to a <br /> depth of 5.5 feet,where approximately 12 inches of No. 3 sand will be installed with an additional <br /> soil gas sampling point centered at 5 feet bgs. The remaining annular space will be filled with <br />