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1' U .C5 Li t1 SAL 11-x. SERVICES <br /> SAN JOAQUIN COUNTY Y c <br /> ENVIRONMENTAL HEALTH DMSION �' < <br /> Karen FursC, M D , Ni RH , Hcalrh Officcr <br /> 304 Easc Wcbcr Aycnuc, Third Floor - Scockion, CA 9520 crFaR�► <br /> 2091468-3420 (a P <br /> ROBERT BOUST <br /> UNOCAL—DBG/AMG <br /> 2121 NORTH CALIFORNIA BLVD STE 250 1998 <br /> WALNUT CREEK CA 94596 NOV 2 <br /> iRE Former Unocal #5098 SITE CODE 2162 <br /> 5606Paafic Ave , <br /> Stockton, CA 95207 <br /> San Joaquin County Public Health Services, Environmental Health Division (PHS- <br /> EHD) has reviewed the "Work Plan for Supplement Environmental Investigation" <br /> submitted by Environmental Resolutions Inc ,(ERI) on November 12, 1998 and has <br /> the following comments <br /> Wissing from the plan are monitoring well construction details Diagrams <br /> and <br /> specifications are to be included for the wells that detail the size, length, placement <br /> depths, intervals, and materials to be included in the construction of the well The <br /> `deep" screened monitoring wells proposed in the plan shall not have screened <br /> intervals greater than 5 feet long In addition, the screened interval of these deep <br /> monrtonng wells shall be placed in the most permeable soil layer closest to the <br /> historical deepest (drought) depth to groundwater (-60 feet below grade) during Fall- <br /> 1978 <br /> Soil samples collected from the monitoringwell installations s steal[ be additionally <br /> analyzed for the seven oxygenates listed in the enclosed PHS-EHD policy The <br /> presence of these constituents has not been investigated and is required by PHS- <br /> EHD All groundwater samples collected from all monitoring wells (new and <br /> existing) are to have all seven oxygenates analyzed by EPA Method 8260 and are to <br /> be in the report due at PHS-EHD at the end of this phase of investigation Ethanol <br /> and Methanol groundwater samples may be analyzed by EPA Method 8015m direct <br /> injection Oxygenate detection limits should be in the 1 0 to 50 0 ug/I range <br /> Soil samples are to be collected and analyzed from at least the current <br /> vadose/saturated zone interface and the historical deepest depth to first <br /> groundwater Additional soil samples may be required to be analyzed as determined <br /> by PHS-EHD staff during the well construction Only consecutive five-foot soil <br /> samples that are non-detect for petroleum and oxygenates at LUFT detection limits <br /> can be used for supporting vertical delineation conclusions <br /> Please report all soil sample data in "mg/kg" only The detection limit for Total <br /> Petroleum as Gasoline (TPH-G) is 10 0 mg/kg or less The detection limit for <br /> Benzene, Toluene, Ethylbenzene, and Xylene (BTEX) soil samples is 0 005 mg/kg <br /> Reports that contain sample data using elevated detection limits should list results <br /> as "less than elevated detection limits" instead of"non-detect" <br /> A Divuion of San Joaquin County Halch Cara Sen ecu <br />