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ENVIRONMENTAL HEALTH'I)EPARTMENT <br /> SAN JOAQUIN COUNTY <br /> Unit Supervisors <br /> Donna K.Heran,R.E.H.S. Carl Borgman,R.E.H.S. <br /> Director 304 East Weber F�VeriUd, Third FIOOC Mike Huggins,R.E.H.S.,R.D.I. <br /> Al Olsen,R.E.H.S. Stockton, California 95202-2708 Douglas W.Wilson,R.E.H.S. <br /> • �.. '- 'PProgram Manager Telephone: (209) 468-3420 Margaret Lagorio,R.E.H.S. <br /> R.E.H.S. Robert McClellon,R.E.H.S. <br /> Laurie A.Cotulla, Fax' (209) 464-0138 Mark Bareellos,R.E.H.S. <br /> Program Manager <br /> BOB COCHRAN JUL 14 2004 <br /> CHEVRON PRODUCTS COMPANY <br /> BLVD V-1140 PO BOX 6004 <br /> SAN RAMON CA 94583-0904 <br /> RE: Former Chevron #9-4054 SITE CODE: 1780RO#: 0000635 <br /> 2103 Country Club Blvd. <br /> Stockton, CA., 95204 <br /> San Joaquin County Environmental Health Department (EHD) has reviewed the June <br /> 28, 2004 Revised Corrective Action Plan (CAP) submitted by SECOR Consulting and <br /> offers the following comments. <br /> Included in the CAP were results of ground water extraction tests, piezometers and <br /> extraction well installation and destruction, remedial alternative evaluation (feasibility), <br /> and a scope of work to continue with the subsurface investigation. <br /> The evaluation of five remedial alternatives was discussed and based on site-specific <br /> parameters, limited soil over-excavation and offsite disposal was concluded to be the <br /> most feasible. No cost comparison for the alternatives was included. <br /> Based on CPT activities conducted on site in March 2004, three water-bearing zones <br /> were identified and the scope of work included in the CAP will target these zones for the <br /> continuing investigation. <br /> The TPHg, Benzene, and TBA detected in the grab ground water sample from CPT-5b <br /> at 78 feet below ground surface (`bgs) is inconclusive so EHD will require additional <br /> investigation at this depth. EHD cannot conclude that the contamination noted at this <br /> extent is truly present in this "C-zone" or just the product of cross-contamination from <br /> the drilling process. With only one ground water sample from only this one CPT <br /> location, EHD does not have a high confidence level that this result in the clayey silts <br /> identified at this depth is a valid reason to install six additional deep CPTs around the <br /> site. <br /> EHD recommends that a monitoring well be installed at CPT-5b location and a short <br /> screen interval be placed at this depth of concern. Sampling this monitoring well over a <br /> short period of time should provide support for vertical delineation or the need for <br /> additional investigation at or below this depth. <br />