FIELD DOCUMENTS_FILE 1 - Laserfiche WebLink

Home Browse Search

STATE OF CALIFORNIA GEORGE DEUKMEJIAN,Governor CALIFORNIA REGIONAL WATER QUALITY CONTROL BOARD— CENTRAL VALLEY REGION -. 3443 ROUTIER ROAD SACRAMENTO,CA 95827-3098 3 August 1989 Ms. Diane Hinson, Registered Sanitarian Environmental Health Division San Joaquin County Public Health Services P.O. Box 2009 Stockton, CA 95201 FORMER EXXON SERVICE STATION, 4444 NORTH PERSHING AVENUE, STOCKTON; GROUND WATER REMEDIATION PLAN We have reviewed the 23 March 1989 Ground Water Remediation Plan for the subject site. The proposal to extract free hydrocarbon product and contaminated ground water from a number of wells and discharge the treated water to an infiltration trench is generally acceptable, provided that the extraction system is capable of recovering the full extent of the contamination and that the infiltration trench is properly designed and permitted. However, the proposal includes a number of statements regarding the probable source of the ground water contamination which are misleading and are not supported by the available information. The proposal states that the major source of the hydrocarbons in the ground water appears to be a Shell service station west of the site. This conclusion is based on the detection of hydrocarbon contamination in soil and ground water samples from a monitoring well across the street from the former Exxon station. While we do not discount the possibility that contaminants may have been released at the Shell station, the proposal failed to note that previous discharges of hydrocarbons from the former Exxon station have been documented. We note that the 8 July 1988 report prepared by E A Engineering Science and Technology, Inc. , (EA) included a similar discrepancy. The report stated that neither free product nor hydrocarbons were detected in soil samples in the excavation. However, the 19 December 1986 Remedial Excavation and Soil Aeration Report, prepared by Harding Lawson Associates, documents that 300 cubic yards of contaminated soil was removed from the tank excavation. After the soil was excavated, hydrocarbon contamination was detected in soil samples taken at the bottom of the tank excavation. In addition, a sample of ground water taken from the tank excavation contained 130,000 parts per billion (ppb) total petroleum hydrocarbons, 40,000 ppb benzene, 43,000 ppb toluene and 9,000 ppb xylene. These values indicate that free hydrocarbon product was probably present in the excavation. We believe that the failure to include this information and information about other documented discharges at this site may have contributed to the above