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PUBLIC I�ALTH SERVIL- ,ES <br /> OPO.UIN,_C <br /> SAN JOAQUIN COUNTY <br /> r. <br /> ENVIRONMENTAL HEALTH DIVISION <br /> Karen Furst, M.D., M.P.H., Health Officer <br /> 304 East Weber Avenue, Third Floor • Stockton, CA 95202 cq.,t RN P <br /> co209/468-3420 <br /> BRETT HUNTER <br /> CHEVRON USA PRODUCTS COMPANY SEP 17 07 <br /> PO BOX 6004 <br /> SAN RAMON CA 94583-0904 <br /> RE: Former Chevron #9-4054 SITE CODE: 1780 <br /> 2103 Country Club Blvd. <br /> Stockton, CA., 95204 <br /> San Joaquin County Public Health Services, Environmental Health Division (PHS- <br /> EHD), has reviewed the "Additional Soil and Groundwater Investigation Workplan" <br /> submitted on September 8, 1997 and offers the following comments. <br /> Recent recommendations from the Central Valley Regional Water Quality Control Board <br /> (CVRWQCB), including the multiple oxygenate sampling memo mentioned in the <br /> workplan, suggest that additional data from the soil and saturated zone be collected at <br /> some sites. <br /> With the depth to first groundwater in this area of San Joaquin County now at the <br /> highest level ever recorded since the late 1970's, PHS-EHD is requiring soil samples to <br /> be collected well into the saturated zone in order to verify soil conditions at historical <br /> low groundwater depth. Soil samples are to be collected from the depth known to be <br /> where the deepest depth to the first groundwater was during the station's operating <br /> period. Additionally, PHS-EHD recommends that you have your consultant performing <br /> this phase of investigation utilize technology that will also allow groundwater samples to <br /> be collected at discreet depths without cross-contamination from contaminated <br /> groundwater at shallower depths. <br /> PHS-EHD is receiving information on other underground tank (UGT) sites that have had <br /> releases during drought/lower groundwater depths. The data suggests that petroleum <br /> contamination in this deeper soil is continuing to leach into the groundwater and <br /> hamper remediation efforts. <br /> Although the workplan mentioned "historical low water", it did not specify the maximum <br /> depth at which soil samples would be collected, nor whether or not deep/discreet <br /> groundwater samples would be collected. PHS-EHD is requiring saturated soil and <br /> discreet groundwater sampling from depths below grade known to be "historical <br /> drought" depths to groundwater during this station's operating period. The workplan <br /> should be modified so that this information is obtained during this mobilization. <br /> A Division of San Joaquin County Health Care Services <br />