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l <br /> ENVIRONMENTAL HEALTH DEPARTMENT <br /> SAN JOAQUIN COUNTY <br /> Unit Supervisors <br /> Donna K. Heran, R.E.H.S. <br /> �IIIIIIca ;� Director <br /> 304 East Weber Avenue, Third Floor Carl Bergman, R.E.H.S. <br /> N'. Ltd Mike Huggins, R.E.H.S, R.D.I. <br /> Al Olsen, R.E.xs. Stockton, California 95202-2708 <br /> • c _� �, . P. � Proram Manaer Douglas W. Wilson, R.E.H.S. <br /> 4 � / FORS g g Telephone : (209) 468-3420 Margaret Lagorio, R.E.H.S. <br /> Laurie A. Cotulla, R.E.H.S. Fax : (209) 464-0138 Robert McClellan, R.E.H.S. <br /> Program Manager <br /> Mark Barcellos, R.E.H.S. <br /> RODGER LISTON SEP 2 7 ZOOS <br /> DARPETRO INC USA SERVICE STATION <br /> 3450 EL CAMINO <br /> CERES CA 95307 <br /> RE: DARPETRO, INC Site Code: 1060 <br /> 749 E CHARTER WAY <br /> STOCKTON, CA 95202 <br /> San Joaquin County Environmental Health Department (EHD ) has received and <br /> reviewed Drilling Activity, dated 24 August 2005 , and Quarterly Report (QR) , <br /> dated 08 August 2005 ; both prepared by California Geophysical Group (CGG) <br /> and comments as follows: <br /> Although monitoring wells MW-14 and MWA6 have not yet been sampled during <br /> a quarterly groundwater-monitoring event, some preliminary characteristics of <br /> your plume have been defined that establish the basis for additional corrective <br /> action at this time. The plume of dissolved fuel components covers an area at <br /> least 190 feet from north to south (MW- 10 to MW-1 ) and 110 feet west to east <br /> (MW-3 to MW-8 ); impacted groundwater encountered in MW-9 and MW-7 may <br /> be related to the plume originating on the 701 E . Charter Way site, and in view of <br /> the data from MW- 12, the relationship of the impacted groundwater in MW- 11 to <br /> your plume is not clear. Based on the CPT data , your dissolved plume appears to <br /> be as thick as 125 feet (top of groundwater to 158 feet below surface grade <br /> (bsg). <br /> Impacted groundwater in the former underground storage tank (UST) area , as <br /> indicated by the July 2005 monitoring event, contains as much as 57,000 <br /> micrograms per liter (µg/1 ) total petroleum hydrocarbons quantified as gasoline <br /> (TPH-g ) , 11 , 000 µg/I benzene , 270 Itg/I methyl tert-butyl ether (MTBE) and 8 . 5 <br /> µg/I 1 ,2-dichloroethane ( 1 , 2-DCA). The concentrations of these and other <br /> contaminants greatly exceed the maximum contaminant levels (MCLS) <br /> established by the Department of Health Services for public drinking water. The <br /> concentrations and extent of contaminants in your plume justify remediation of <br /> impacted groundwater. Submit a feasibility study to EHD no later than <br /> 14 November 2005 for groundwater remediation . As contamination at depth has <br /> not yet been verified through monitoring the work plan should be for interim <br /> remediation . And as remediation methodologies for shallow water are likely to <br /> differ from those employed for deeper impacted groundwater, the work plan <br />