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San Joaquin County DIRECTOR <br /> Donna Heran,REHS <br /> Environmental Health Department <br /> ASSISTANT DIRECTOR <br /> M <br /> -G Laurie Cotulla,REHS <br /> N 600 East Main Street <br /> Stockton, California 95202-3029 PROGRAM COORDINATORS <br /> Carl Borgman,REHS <br /> Mike Huggins,REHS,RDI <br /> •. :P Website: www.sjgov.org/ehd Margaret Lagorio,REHS <br /> q /F ORa phone: (209)468-3420 Robert McClellon,REHS <br /> Fax: (209) 464-0138 Jeff Carruesco,REHS, RD( <br /> August 22, 2008 Kasey Foley,REHS <br /> Mr. Gerald L. Thiemann <br /> 327 Blossom Drive <br /> Ripon, California 95366 <br /> Subject: Former Thiemann's Service Station <br /> 106 West Second Street <br /> Ripon, California 95366 <br /> The San Joaquin County Environmental Health Department (EHD) has reviewed <br /> Additional Subsurface Investigation Work Plan, Former Thiemann's Service Station, 106 <br /> West Second Street, Ripon, California, dated July 16, 2008, prepared and submitted by <br /> ATC Associates Inc. (ATC) on your behalf. In the work plan, ATC proposes the <br /> advancement of three cone penetration test (CPT) borings and adjacent direct-push borings <br /> to approximately 100 to 150 feet below surface grade (bsg) to assess soil lithology and <br /> stratigraphy and collect soil and groundwater samples for chemical analysis. <br /> The EHD believes impacted soil has been adequately delineated vertically at the source <br /> area, based on the analytical results for soil samples collected from soil boring SB-1 in the <br /> source area. Only total xylene at a concentration of 0.025 milligrams per kilogram (mg/kg) <br /> was detected in the soil sample collected at total depth of 49.5 feet bsg; therefore, you need <br /> to provide technical justification for collecting additional soil samples, the criteria for <br /> selecting soil sample locations, and an approximate number of soil samples proposed to be <br /> submitted for laboratory analysis. <br /> The EHD approves the advancement of one CPT boring to approximately 100 to 150 feet <br /> bgs, preferably in the source area. However, the EHD believes the depths for the <br /> remaining two CPT borings should be based on data generated from the initial CPT boring, <br /> and should exceed 100 feet bsg only if justified by findings from the initial CPT boring. <br /> Groundwater sampling should not arbitrarily be limited to two grab groundwater samples <br /> per CPT boring, but instead should be based on the number of permeable intervals <br /> identified from the CPT. Grab groundwater samples collected from discreet borings <br /> adjacent to the two onsite CPT boring locations should be collected below the screened <br /> intervals of 22 to 42 feet bsg for MW-1, MW-2, and MW-3. This criterion does not apply <br /> to off-site groundwater sampling. <br />