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PUBLIC HEALTH )ERVICES <br /> SAN JOAQUIN COUNTY _ x <br /> ENVIRONMENTAL HEALTH DIVISION <br /> Karen Furst, M.D., M.P.H., Healtl Officer '�rxflaa�P <br /> 304 East Weber Avenue, Third Floor • Stoc cton, CA 95202 <br /> 2091468-3420 (C (DPY <br /> ERNEST J POMBO JR <br /> P O BOX 805 <br /> TRACY CA 95378 NOV 2 2 1999 <br /> RE: Pombo Ranch Property SITE CODE: 508110 <br /> 24100 S Lammers Road <br /> Tracy CA 95378 <br /> San Joaquin County Public Health Services, Environmental Health Division (PHSIEHD) <br /> has reviewed the "Subsurface Investigation Repoit" dated September 10, 1999 that was <br /> submitted by M.J. Kloberdanz and Associates (M K) on behalf of the above referenced <br /> site and has the following comments. <br /> On July 6, 1999 four geoprobe soil borings were advanced on site to continue the <br /> investigation of the petroleum hydrocarbon contamination. Soil and grab groundwater <br /> samples were collected for analysis. The only soil sample which evidenced <br /> contamination was the 10-foot below surface grace (bsg) sample from boring SB-11, <br /> located approximately 45-feet east of the former t nk pit area. All grab water samples <br /> evidenced contaminant impact. No samples collected during this mobilization reported <br /> methyl tertiary butyl ether (MTBE). A positive hit for MTBE was confirmed by EPA <br /> Method 8260 analysis in a water sample collected from boring SB-3, located in the <br /> former tank pit area, on September 16, 1998. <br /> On July 20, 1999 three shallow groundwater mon toring wells were installed on-site. <br /> Three soil samples were submitted for analysis, results were all non-detect. The wells <br /> were developed and sampled on July 23, 1999. Analytical results for these samples <br /> were also non-detect. <br /> Data collected thus far indicates that the bulk oft the residual petroleum hydrocarbon <br /> contamination at this site is in the area of the former underground storage tank and to <br /> approximately 45-feet east of this area, to a depth of at least 10-feet bsg and not more <br /> than 15-feet bsg. Initial sampling of the monitoring wells indicates that the lateral extent <br /> of the shallow groundwater contaminant impact h s been defined. <br /> The report recommends that appropriate remedial measures for this site should include <br /> over-excavation of all contaminated soil in the former UST area. Groundwater <br /> monitoring of the on-site wells should continue to establish trends in the groundwater <br /> gradient flow direction and contaminant concentr tion/attenuation rates. <br /> A Division of San Joaquin Coun Health Care Services <br />