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PUBLIC HEALT SERVICES <br /> �. � ..o <br /> SAN JOAQUIN COUNTYz` s <br /> JOG[KHANNA M.D.,M. .H. <br /> Health Officer r" <br /> P.O. Box 2009+ (1601 East Hazelton Avenue) Stockton,California 95201 <br /> �4L1 jcpR�\ <br /> (209) 468-3400 <br /> JOHN DIECKMAN EXECUTOR <br /> 'MCCALLISTER TRUST JUN 0 8 1993 <br /> 500 AIRPORT BLVD <br /> SUITE 200 <br /> BURLINGAME CA 94010 <br /> RE: System 99 SITE CODE 1275 <br /> 601 South Ventura <br /> Stockton, CA 95203 <br /> San Joaquin County Public Health Services,Environmental I lealth Division(PHS/EHD)has completed review <br /> of the "Problem Assessment Report and Soil Contamination Work Plan" dated May 1993 and prepared by <br /> RESNA. PHS/EHD has the following comments for your consideration. <br /> The Problem Assessment Report (PAR) described the site history and reviewed analytical results from the <br /> March 1989 tank removal (8,000 gallon gasoline and 8,000 gallon diesel) the October 1989 re-excavation <br /> attempt,the August 1990 installation of monitoring wells,1v1W1 -MW3,the March 1992 installation of MW4 <br /> and the quarterly sampling of monitoring wells. <br /> Residual soil contamination was documented in samples collected from the October 1989 re-excavation <br /> attempt. Analysis of sidewall samples, 15'NE and 17'NW (composited) evidenced 6 ppb benzene, 98 ppb <br /> toluene, 110 ppb ethylbenzene, 430 ppb xylene, and 16 pp TPH-gas. Analysis of bottom samples, 15.5'NE <br /> and 17'NW (composited) evidenced 4 ppb benzene, 72 ppl, toluene, 150 ppb ethylbenzene, 610 ppb xylene, <br /> and 30 ppm TPH-gas. Unfortunately, analysis for T?H-dic sel was not conducted on samples collected from <br /> the re-excavation, despite the detection of TPH-diesel, 32 ppm, in samples collected at the time of tank <br /> removal. Analysis of soil samples collected during the "istalIation of MW1-MW4 did not evidence soil <br /> contamination. However, petroleum odors were observed during the installation of MWI at 31.5-36.51. <br /> Evidently PID measurements were not recorded during the installation of MW1-MW3. <br /> Groundwater contamination has been detected in monitoring wells, MW1 and MW3. Contamination of up <br /> to 7.3 ppb benzene (1990) and 1,800 ppb TPH-gas (1991) and 1,800 ppb TPH-diesel (1992) was detected in <br /> MWl which is directly downgradient of the tank pit. <br /> Three remedial alternatives were evaluated: cap and monitoring, soil excavation, and in-situ soil <br /> venting/vacuum extraction. Soil excavation was the preferred alternative. PHS/EHD concurs that soil <br /> excavation is an effective soil remedial action. <br /> The Soil Contamination Work Plan included excavation of contaminated soil and groundwater extraction. The <br /> area of residual soil contamination was estimated to be 25 feet by 55 feet by 20 feet. It is anticipated that <br /> approximately 300 - 350 cubic yards of contaminated soi will be excavated. The stockpiled soil will be <br /> segregated based on field PID measurements. It should b noted that diesel is classified as a semi-volatile; <br /> therefore,PID measurement of diesel contamination is no representative as PID measurement of gasoline <br /> contamination. All stockpiled soil should be placed on ani permeable barrier.Contaminated soil should also <br /> be covered during evaluation by the San Joaquin Valley Unified Air Pollution Control District for aeration <br /> permit requirements. <br /> A Division of San Joaquin County health Care Servlces <br />