SITE INFORMATION AND CORRESPONDENCE

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Sanchez Property-Former UST page 2 1876 Country Club Blvd., Stockton. Actual successful field procedures included small pumping efforts by centrifugal pumps placed in the hole to push out the groundwater and allow for soil samples to be collected from the bottom of the excavation. These quick, aggressive methods have been successful in allowing for small excavations deep into the saturated zone to be conducted without large dewatering procedures or storage equipment to be used. EHD thanks you for your efforts to support continuous dewatering procedures, but feels that decommissioning monitoring wells and producing large amounts of groundwater to over- excavate the relatively small area of highly impacted soils is not the most practicable action. EHD does feel that over-excavation is the most aggressive remedial alternative for this site and with some modifications by WEGE this can be the most cost-effective alternative also. Rather than attempt to dewater the 'upper zone', EHD recommends that you evaluate a proposal to over-excavate thru the standing water that may/will enter the hole. Be prepared to containerize this sludge properly so that runoff is minimal. Since the actual excavation will be deeper than it is wide, a large, continuous dewatering process will not be required. A small dewatering effort will be needed when the bottom soil sample is collected and possibly if dry soil is to be used to backfill the excavation. Initially, the over-excavation proposal was to use the soil excavated from the treatment area as backfill for the hole. If a large dewatering process is needed to provide a dry hole for this fill material, EHD recommends that the water remain and another compactable, permeable material (i.e. pea gravel) be used to fill the excavation. Also the treatment area should now be lined prior to filling it with the excavated soil so that leaching of the petroleum constituents may not occur. Drying during the summer months will add to the degradation of the petroleum constituents in this sludge material. Importing clean, permeable backfill should be substantially less expensive that hauling off large amounts of contaminated water. WEGE should evaluate these comments and verify if they would work for this site. A revised remedial action work plan should be submitted to EHD for evaluation. Thank you for your continued cooperation and willingness to remediate your site. With just a little more effort this site could be entering it's last phase of investigation and well on it's way to no further action. Donna Heran, REHS, Director Enviro mental Health D' i ion 1 Michael J. Infurna Jr., Nor REHS Margaret agorio, REHS LOP/Site Mitigation Unit IV Supervisor MI: cc: CVRWQCB— Marty Hartzell, Sacramento. cc: WEGE—G. Converse, 1386 E. Beamer St.,Woodland, CA. 95776-6003.