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I ' GEOLOGICAL AUDIT SERVICES, INC. FIRST QUARTER 1993 PROJECT STATUS SUMMARY ' SITE: ARCO MINI MART ADDRESS: 4511 Pacific Ave. Stockton, CA I CLIENT: Arthur Wyatt TELEPHONE: 951-1207 LEAD AGENCY: SAN JOAQUIN COUNTY PHS/EHD AGENCY CONTACT: Diane Hinson TELEPHONE: 468-3452 ' SCOPE This report briefly summarizes the status of site assessment and provides recommendations for additional work. SUMMARY OF WORK COMPLETED Four soil borings (B1-B4) were installed on October 19 and 20, 1992 . Bl was completed as a vapor extraction well by the installation of perforated PVC pipe from 25 to 55 feet. Borings B5- B7 were drilled on January 22 and 25, 1993 and completed as groundwater monitoring wells by the installation of perforated PVC pipe from 50 to 70 feet in D6 and B7 and from 63 to 78 feet in B5. SUMMARY OF SOIL TYPES Surface to 15 feet--weakly consolidated silt 15-35 feet--downward coarsening sand 35-55 feet--moderately consolidated silt 55 to 70+ feet--silty sand, saturated LABORATORY ANALYTICAL RESULTS Soil: . TPH-G and BTE&X in B1, B2, B4; minor in B5-B7 . See Table 1 and Attachments A and B Water. BTE&X in MW-1, MW-2 , MW-3; TPH-G in MW-1, MW-2 ; TPH-O in MW3 . See Table 2 and Attachment C GROUNDWATER DEPTH AND GRADIENT I Monitoring Date: 29 January 1993 Field Data: See Table 3 Average Depth: 54. 5 feet Gradient: . 018 ft/ft to N430W CONCLUSIONS AND RECOMMENDATIONS Little or no soil contamination was detected in B3 and B5-B7 , which appear to be near or beyond the lateral limit of soil contamination. The calculated groundwater gradient is not in accord with prior expectations of an eastward gradient, suggesting either local or temporal variations from the regional gradient. The plume Of contaminated groundwater extends beyond the limits of the present data, but due to the low levels of contaminants and the I