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;� k + <br /> PUBLIC �IEALTH SEk4CES <br /> y o j <br /> SAN JOAQUIN COUNTY 'oPo.V.! .a <br /> ENVIRONMENTAL HEALTH DIVISION <br /> Ernest M. Fujimoto, M. D., M.P.H., Acting Health Offic <br /> 304 E. Weber Ave., Third Floor • P. O. Box 388 • Stockton, CA 201 38�� I F—� GjFaRN " l <br /> 209/468-3420 lI <br /> MAILED MAR 2 7199E <br /> W V RAYMOND <br /> P O BOX 567 <br /> STOCKTON CA 95203 <br /> E ' <br /> RE: California Welding Supply SITE CODE: 2083 <br /> 1000 East Eleventh Street <br /> Tracy, CA j <br /> San Joaquin County Public Health Services, Environmental Health Division (PHS/EHD) has reviewed the <br /> February 1996 Interim Assessment Report prepared by Wm. J. Hunter and Associates for the above <br /> referenced site. <br /> The report summarizes the interim remedial overexcavation performed on September 19, 1995. The <br /> conclusion of the report is that there is soil contamination beneath the site caused by leakage from the <br /> removed underground storage tanks (UST's) and that groundwater is assumed to be impacted due to the <br /> presence of groundwater observed seeping into the excavation. <br /> The report contains a workplan to determine the extent of soil and possible groundwater contamination <br /> encountered during the work described above. The workplan proposes obtaining soil and groundwater <br /> samples from 7 soil probe locations. Soil samples will be obtained from 5 and 10 feet below grade and <br /> a groundwater grab sample will be collected using a hydropunch from the capillary fringe estimated at 10 <br /> to 12 feet below ground surface. Samples will be analyzed for total petroleum hydrocarbons as gasoline, <br /> benzene, toluene, ethylbenzene, total xylenes and lead. ,l <br /> PHS/EHD recommends that the lead analysis be discontinued as an analytical test for this site. The lead <br /> levels appear to be in the range of naturally occurring lead. i t <br /> c <br /> The June 1995 workplan prepared by Wm. J. Hunter and Associates states that soil contamination and <br /> groundwater samples will be tested for BTEX, TPH-g, total leadand TPH-d. There are no laboratory <br /> results from the excavated soil for TPH-d. PHS/EHD recommends analysis for TPH-d be conducted on <br /> soil and groundwater samples submitted for analysis until the extent of diesel contamination can be <br /> determined. <br /> At this site there is less than a five foot separation between soil contamination and groundwater, therefore <br /> PHS/EHD requires the installation of monitoring wells to determine the impact to groundwater.t The <br /> minimum number of required wells is three. One of the wells must be placed within 10 feet of the original <br /> tank excavation. The remaining two well locations may be based upon data gathered during this phase <br /> of the investigation. The wells should be placed in a triangular formation to facilitate gradient <br /> determination and to increase the probability that one well will be in a downgradient position. PHS/EHD <br /> requires the analysis for methyl tertiary butyl ether(MTBE) on all groundwater sites polluted with gasoline. <br /> I <br /> i <br /> PHS/EHD recommends that the placement and number of probe locations be based upon field data. Once <br /> the lateral extent of soil contamination is determined, additional probe locations should be used to obtain <br /> groundwater data only. This methodology should minimize the number of samples submitted for analysis. <br /> j <br /> A Division of San Joaquin Count%Health Care Services 1II <br /> I <br /> t j <br />