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a <br /> PUBLIC IJEALTH SERVICES N <br /> SAN JOAQUIN COUNTY <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 9520 38 #..4:i209/468-3420 <br /> ELLEN AQUARO NOV 2 0 1996 <br /> SAN JOAQUIN COUNTY CAPITAL PROJECTS <br /> 222 E WEBER AVE RM 678 <br /> STOCKTON CA 95202 <br /> RE: San Joaquin County Human Services Building SITE CODE: 1257 <br /> 145 South Sutter Street <br /> Stockton CA 95202 <br /> San Joaquin County Public Health Services, Environmental Health Division <br /> (PHS/EHD) has completed review of the "San Joaquin County Human Services <br /> Administration Phase IV Site Investigation and First Quarter Groundwater Sampling <br /> Report" dated October 1996 and prepared by Weston. <br /> The report included the August 23, 1996 results from the drilling and sampling of <br /> soil boring BH-13 (total depth 65.8 feet below ground surface (bgs)) and <br /> monitoring well MW9 (total depth 55 feet bgs). Static water levels were measured <br /> at 37.5 feet bgs. Soil boring, BH-13, was drilled to a significant depth below the <br /> current static water level to investigate the disposition of soil contaminants when <br /> the static water level was greater than 50 feet bgs. Extremely high concentrations <br /> of soil contaminants were evidenced, up to 37 ppm benzene and 650 ppm TPH <br /> gas. It is clear that until remedial efforts are underway the soil contamination <br /> adsorbed below the static water level will continue to provide a source of <br /> contamination to groundwater. The groundwater sample collected from BH-13 <br /> evidenced 16,000 ppb benzene. <br /> The cross section A-A' provided misleading information, with regard to the <br /> designation of "ND". Not detected IND) at the reporting limits infers that there <br /> was no contamination, when in fact the reporting limit was elevated because a <br /> highly contaminated sample was diluted. PHS/EHD has indicated on numerous <br /> occasions the appropriate methodology to indicate that the reporting limits were <br /> elevated. Thank you for accurately reporting the modified ND results on the <br /> analytical summary tables. Please also recall that PHS/EHD has requested that the <br /> depth to water be included on all groundwater analytical results tables. Also all <br /> reports should include historic summary tables for soil and groundwater results. <br /> The quarterly groundwater results continued to evidence significant groundwater <br /> contamination. The abbreviated sampling schedule which was referenced was <br /> related to a yearly calendar schedule rather than individual sampling events. <br /> A Division of San Joaquin County Health Care Services <br />