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4 Y <br /> Mr George Takemon Project OF90-002 05 <br /> . August 15, 1996 <br /> Page 7 <br /> CONCLUSIONS AND RECOMMENDATIONS <br /> During excavation activities, approximately 7,200 pounds of TPHG were removed Prior to <br /> operating the remediation system, EMCON has estimated that approximately 3,200 pounds of <br /> hydrocarbons renmained beneath the fom-cr USTs and dispenser islands Based on the results of <br /> operating the remediation system, approximately 3,000 pounds of TPHG have been removed <br /> primarily from depths of approximately 55 feet bgs to the groundwater surface (based on <br /> screen Intervals of vapor extraction wells) <br /> The results of the groundwater sampling events Indicate that dissolved hydrocarbons have been <br /> delineated and appear to be Isolated beneath the former USTs and dispenser islands Within the <br /> last five sampling events, benzene has not been detected In groundwater monitoring wells, with <br /> the exception of wells MW-13 and MW-14, which contain relatively low concentrations In <br /> general, TPHG and benzene concentrations have declined and the hydrocarbon plume appears <br /> to be stable <br /> It is EMCON's opinion that natural biodegradation will further reduce residual and <br /> dissolved petroleum hydrocarbons Therefore, due to the removal of residual <br />. hydrocarbons via excavation and remediation, the decline of dissolved hydrocarbons, and <br /> the process of natural biodegradation, it is EMCON's opinion that no further action is <br /> warranted at the site In addition, EMCON recommends that the wells be destroyed <br /> OCCUMENT DiSTR;BUT:ON <br /> We recommend copies of this report to be forwarded to the following <br /> Linda Turkatte <br /> San Joaquin County Public Health Services <br /> Environmental Health Division <br /> P O Box 388 <br /> Stockton, California 95201-0388 <br /> Elizabeth Thayer <br /> California Regional Water Quality Control Board <br /> Central Valley Region <br /> 3443 Routier Road, Suite A <br /> Sacramento, California 95827-3098 <br /> SAC\N\PJ"F90\OF9000205AS-95\p I <br />