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PUBLIC HEALTH SERVICES oP. ....c <br /> �. <br /> SAN JOAQUIN COUNTY <br /> ENVIRONMENTAL HEALTH DIVISION z� <br /> Ernest M. Fujimoto, M.D., M.P.H., Acting Health Officer <br /> 445 N. San Joaquin Street • P. O. Box 388 • Stockton, CA 95201-0388 <br /> 209/468-3420 <br /> D <br /> DON HOFFMAN <br /> DON HOFFMAN AND MAVIS HOFFMAN <br /> 1935 LA CADENA 2 4 <br /> DIABLO CA 94258 <br /> RE: RALPH HAYES SITE CODE: 2068 <br /> 835 W CLOVER <br /> TRACY 95376 <br /> San Joaquin County Public Health Services, Environmental Health Division(PHS/EHD)has reviewed the March 3, <br /> 1995 "Phase II Workplan Supplement" (workplan)and the March 22, 1995 "Additional Groundwater Sampling and <br /> Excavation of Contaminated Soil" (report)report prepared by Terra Search Inc., for the above referenced site. We <br /> have also reviewed your April 3, 1995 letter. <br /> The report was sent in response to a telephone conversation which took place on March 14, 1995 between PHS/EHD <br /> and Terra Search where PHS/EHD requested additional information necessary to review the March 3, 1995 <br /> Workplan. The workplan concluded that further work is not necessary for closure. <br /> After reviewing the workplan the report and the letter PHS/EHD has determined that there is additional work which <br /> must be completed prior to closure of this site in order to assure that impact to the environment from this site has <br /> been mitigated. <br /> During the March 14, 1995 telephone conversation staff requested mass balance calculations of the remaining <br /> contamination. The report provides mass balance calculations of the contaminated stockpile and the remaining below <br /> groundwater trim and sluff material in the excavation. The report does not estimate the mass balance of <br /> contaminated groundwater, indicated in the last round of sampling, which is present at the site. <br /> Monitoring well data prior to completion of the overexcavation indicates the presence of a low concentration plume <br /> which was detected in Monitoring wells 4,2,and 3. The upgradient well is ND. It is recommended the monitoring <br /> wells be sampled subsequent to an overexcavation to determine the effect of soil remediation on groundwater. <br /> During the overexcavation, the analysis for motor oil was discontinued and the analysis for diesel was added due <br /> to information obtained during the procedure. The monitoring wells have never been sampled for diesel. <br /> After the excavation was completed there were two stockpiles. One stockpile was considered clean overburden and <br /> was separated from soil removed from the excavation which was considered contaminated by field observations. <br /> During the inspection of November 8, 1994 three discrete samples were taken from the clean stockpile which was <br /> estimated at that time to be 80 cubic yards (cy). The report states that the clean stockpile is 100 cy and will be <br /> returned to the excavation. PHS/EHD requires a discrete sample for every 25 cy of stockpile material which is to <br /> be disposed of on site. Since no contamination was detected at proper detection limits, and at the time of sampling <br /> the stockpile was estimated to be 80 cy, PHS/EHD will allow this material to be used as clean backfill in the <br /> excavation as long as it is placed last and occupies the uppermost portion of the backfill. <br /> a <br /> A Division of San Joaquin County Health Care Services <br />