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Working To Restore Nature <br /> 1710 Main Street <br /> Escalon, CA 95320 S-301Ad3Sf11M]d <br /> Phone (209) 838-3507 HIIVIH JViNI1ltN081AN3 <br /> FAX (209) 838-3509 t 833 February 17, 1993 <br /> Mr Harlin Knoll <br /> San Joaquin County Public Health Services <br /> Environmental Health Division <br /> P O Box 2009 <br /> Stockton, CA 95201 <br /> RE Workplan for Soil Excavation, J B Terminal/Blincoe Trucking, 6700 Grantline <br /> Road, Tracy, CA <br /> This letter will serve as a Workplan for soil excavation to be conducted at the above referenced <br /> site (Figure 1) The scope of the work is based upon the findings from previous investigations <br /> SITE BACKGROUND <br /> The site was the location of two 500 gallon underground storage fuel tanks The tanks and <br /> ancillary burred product lines were removed in September 1987 The tanks were used to store <br /> leaded and unleaded gasoline fuel Figure 2 depicts the former tank locations relative to other <br /> facility features <br /> During tank removal field evidence and subsequent laboratory analyses indicated the presence <br /> of low concentrations of toluene, xylenes, and total petroleum hydrocarbons as gasoline in the <br /> soils and groundwater within the tank excavation Ethylene dibromide, organic lead, and <br /> benzene were not detected above method detection limits in any samples Based upon the <br /> constituents and the levels detected the excavation was backfilled Laboratory results for <br /> samples are summarized in Tables 1 and 2 <br /> Five monitoring wells have been installed on the site (MWI, MW2, MW3, MW4, MWS) since <br /> the site investigation was initiated in March of 1990 During the monitoring and sampling <br /> history petroleum hydrocarbons have been detected in the groundwater collected from well MWI <br /> which is next to the former tank location in the down gradient direction Historical data for <br /> monitoring well MWI indicates that petroleum hydrocarbon analytes have been gradually <br /> decreasing in the groundwater except when irrigation of the fields surrounding the site in late <br /> summer causes an increase in the water levels When water levels rise into the petroleum <br /> hydrocarbon contaminated soils left in place contaminants are released into the groundwater and <br /> higher levels of contaminants are detected in well MWI Additionally the petroleum <br /> hydrocarbons eventually impact the downgradient wells MW2 and MW4 (On July 30, 1992 <br /> WP-0293 LF <br />