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PUBLIC HEALTH SERV710ES <br /> SAN JOAQUIN COUNTY <br /> 2• •.y <br /> ENVIRONMENTAL HEALTH DIVISION <br /> Ernest M. Fujimoto, M. D., M.P.H., Acting Health Officer <br /> 304 E. Weber Ave., Third Floor • P. O. Box 388 • Stockton, CA 95201-0388 °4�1FORr'�P <br /> 209/468-3420 <br /> Q <br /> JEFF GRANBERRY <br /> SHELL OIL CO MAILED NOV 14199 <br /> P O BOX 4023 <br /> CONCORD CA 94524 <br /> RE: WATERLOO SHELL SITE CODE: 1760 <br /> 4315 WATERLOO ROAD <br /> STOCKTON CA 95205 <br /> San Joaquin County Public Health Services, Environmental Health Division (PHS/EHD) has <br /> reviewed the September 22, 1995 "Site Investigation Workplan" prepared by Fugro West, Inc. <br /> of Roseville CA, for the above referenced site. <br /> The workplan was sent in response to the PHS/EHD letter dated August 29, 1995, concerning <br /> the petroleum hydrocarbon contamination discovered when the underground storage tanks were <br /> upgraded in December of 1994. The letter describes three areas of the site that require <br /> additional characterization. These areas are identified by sample locations. The area of PL-13, <br /> PL-9, and the area of PL-12 (the two dispenser islands); and the area of WE-14 (the east wall <br /> of the former tank excavation). <br /> In the workplan, Fugro proposes to investigate the three areas identified in the August 29, 1995 <br /> letter, and an additional location identified as EW-19. The contamination in the area of EW-19, <br /> 1.3 ppm TPH-g and .012 ppm Xylenes, does not pose a significant threat to groundwater, and <br /> may remain in place. PHS/EHD does not require further characterization of contamination in <br /> this area. <br /> Fugro proposes to investigate the area of PL-12 and WE-14 with one GeoProbe each. The <br /> purpose of the single GeoProbe, as explained by a Fugro representative during a telephone <br /> conversation which occurred on October 3, 1995, is to determine the vertical extent of <br /> contamination. The lateral extent of contamination in these areas also requires definition. <br /> PHS/EHD requests additional GeoProbes in these areas for lateral definition. <br /> Fugro proposes to investigate the area of PL-9 and PL-13 with three GeoProbes. Using three <br /> strategically placed GeoProbes, it may be possible to obtain data which defines the vertical and <br /> lateral extent of contamination in this area. <br /> Fugro proposes to advance the GeoProbes around the dispenser islands to a maximum depth of <br /> 15 feet, and the GeopProbe in the east wall of the former tank excavation to a depth of 30 feet. <br /> PHS/EHD recommends that the depth of the borings be based upon field screening, in order to <br /> assure that the borings extend beneath the contamination, and define the vertical extent of the <br /> contamination. <br /> A Division of San Joaquin County Health Care Services <br />