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f 4 1 <br /> PUBLIC HEALTH SERVICES <br /> SAN JOAQUIN COUNTY a` <br /> N: < <br /> JOGI KHANNA M.D,M.P.H <br /> Health Officer <br /> r.. <br /> P.O. Box 2009 9 (1601 East Hazelton Avenue) 0 Stockton, California 95201 <br /> 4GIFOR� P <br /> (209) 468.3400 <br /> MR CHUCK CARMEL Cc !1, I <br /> ARCO PRODUCTS COMPAN ` <br /> P O BOX 5811 FEB 1 1993 <br /> SAN MATEO CA 94402 <br /> RE: ARCO Station #6100 SITE CODE: 1708 <br /> 25775 Patterson Pass <br /> Tracy, CA 95376 <br /> San Joaquin County Public Health Services, Environmental Health Division (PHS/EHD) has reviewed the <br /> "Status of Environmental Investigation" dated November 12, 1992, prepared by RESNA for the above <br /> referenced site. <br /> Included in the report was information from the well log for the drinking water well at the site. <br /> Apparently in 1969 first water was approximately 100 feet below ground surface (bgs). Although water was <br /> not encountered in boring B-9, which was drilled to 115 feet bgs, the boring log does note slightly damp <br /> soil at 106 feet bgs. Since this area of the county is not in the flood control zone San Joaquin County <br /> Flood Control does not have information on depth to groundwater at this site. <br /> Also since surface elevations differ greatly in this area information from surrounding wells cannot be used. <br /> PHS/EHD requested in a April 24, 1992 letter that the drinking water well at this site be measured for <br /> depth to first groundwater. This has not been done to date. PHS/EHD requeststhat this well be <br /> measured and that PHS/EHD staff be present during the measurement. <br /> Soil contamination of up to 7400 parts per million of total petroleum hydrocarbons as gasoline exist at 25 <br /> feet bgs below the existing underground tanks. Boring B-6 evidences some contamination at 35 feet bgs in <br /> this same area. Installation of vapor extraction wells to address this area should be considered. <br /> Soil samples were not analyzed from 46 feet to 76 feet bgs in boring B-25 so the extent of contamination <br /> in this area should be further investigated. <br /> In December 1992 borings and vapor extraction wells were installed to the southeast of the site. The <br /> completion of boring B-26 as a vapor extraction well entailed the use of three different drilling contractors. <br /> On December 22, 1992 WESTEX was to complete the installation of the well. An early afternoon grout <br /> time was scheduled. The well was not completed when PHS/EHD staff arrived. The driller stated the <br /> boring was not straight and he was essentially redrilling the boring. It was noted that about one third of <br /> the bags of cement brought for grout mix were Nevada cement. PHS/EHD staff have found this type of <br /> cement to sometimes have a black oily substance float to the top of the grout when it is mixed. If this <br /> occurs, the grout is considered adulterated and it is not allowed as well grout. Completion of the well and <br /> mixing of the grout was very slow. PHS/EHD staff time (including overtime) will be billed site specific <br /> through the Local Oversight Program. <br /> A Division of San Joaquin County Heath Cp SCMCCS 10 <br />