SITE INFORMATION AND CORRESPONDENCE

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y T: ! F PUBLIC h'"EALTH SERVICES u� •.,C SAN JOAQUIN COUNTY ENVIRONMENTAL HEALTH DIVISION Karen Furst, M.D., M.P.H., Health Officer 304 East Weber Avenue, Third Floor • Stockton, CA 952(}2 249/468-3420 MANUEL & MARY SANCHEZ OCT 21 1N7 1633 W WALNUT ST STOCKTON CA 95203 RE: Former Underground Tanks SITE CODE: 1844 1876 Country Club Blvd. Stockton, CA_, 95203 San Joaquin County Public Health Services, Environmental Health Division (PHS-EHD), has reviewed the "Workplan for Removing Contaminated Soil" received October 15, 1997, and has the following comments. Since the PHS-EHD correspondence in July 1997 that required this cost-effective study/workplan, recent changes in investigative techniques at groundwater contaminated underground tank (UGT) sites have been initiated at PHS-EHD and you and your consultant should be aware of the new requirements that affect you. Sites such as yours that have consistently high groundwater contamination levels and relatively low soil contamination are now being required to investigate the soil and groundwater conditions at the historical deepest depth to groundwater known to exist while the UGTs were onsite. Other UGT sites that now have high groundwater contamination and low soil contamination in the shallow vadose zone have gone on to verify that soil contamination exists at a deeper level. The significantly higher levels of soil contamination detected at the historical drought depth are continuing to leach into the groundwater and causing the elevated contamination levels seen in the samples collected from the shallow groundwater monitoring wells. In order to verify if this condition exists at this site, you will be required to investigate the soil and groundwater conditions at 40 feet below the surface, the historical drought of 1978-1979. Techniques that will allow for discreet soil and groundwater sample collection in the saturated zone should be utilized. With the possibility of cross-contamination from passing clean sample equipment through contaminated water in the boring or push- point, PHS-EHD recommends dual tube technology or equivalent be utilized so that valid samples can be collected. Continuous soil coring should be utilized. Deeper soil and/or groundwater contamination will require further delineation as well as a re- evaluation of your consultant's cost-effective proposal to excavate and remove the shallow soil discussed in his recent proposal. A Division of San Joaquin County Health Care Services