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PUBLIC T ALTH SERVI ES <br /> SAN JOAQUIN COUNTY <br /> a 2 <br /> ENVIRONMENTAL HEALTH DIVISION <br /> Karen Furst, M.D., M.P.H., Health Officer �. P <br /> 304 East Weber Avenue, Third Floor • Stockton, CA 95202 <br /> 209/468-3420 <br /> BRETT HUNTER cc, <br /> ENVIRONMENTAL ENGINEER SEP 12 1997 <br /> CHEVRON USA <br /> P O BOX 5004 <br /> SAN RAMON CA 94583-0804 <br /> RE: Lincoln Village Chevron Station#9-4275 SITE CODE: 1952 <br /> 2905 West Benjamin Holt <br /> Stockton CA 95207 <br /> San Joaquin County Public Health Services, Environmental Health Division(PHS/EHD)has completed <br /> review of the"Draft Addendum to Corrective Action Plan" dated August 15, 1997 prepared by Geraghty <br /> and Miller. PHS/EHD has the following comments for your action and consideration. <br /> PHS/EHD understands that a draft was submitted so that the due date established in PHS/EHD's <br /> correspondence dated June 17, 1997 could be met. PHS/EHD requires that a final report be submitted <br /> and that the report be signed by an appropriate registered professional. <br /> The Underground Storage Tank Regulations requires that a Corrective Action Plan include an assessment <br /> of the impacts that includes the physical and chemical characteristics,the hydrogeologic characteristics, <br /> the proximity of nearby surface and groundwater,the current and potential beneficial uses of these <br /> waters, the potential effects of residual contamination on nearby surface water and groundwater. A <br /> Corrective Action Plan shall also include a feasibility study to evaluate alternatives and cleanup levels <br /> for ground or surface waters that are affected or threatened by the unauthorized release that comply with <br /> water quality plans and policies. <br /> Assessment of Impacts <br /> The Corrective Action Plan included Figure 2 which depicted the maximum concentrations of TPH-gas <br /> and benzene in the soil. An estimate of the distribution laterally and vertically was not included, <br /> although a statement was included that no hydrocarbons were detected at 31.5 feet below ground surface <br /> (bgs). Estimates of the mass of contamination prior to implementing corrective action are useful when <br /> evaluating the effectiveness of the implemented corrective action. Please provide an estimate of the <br /> mass of soil and groundwater contamination prior to corrective action implementation with pictorial and <br /> mathematical explanations. <br /> PHS/EHD concurs that additional groundwater monitoring wells may be necessary to define the extent of <br /> the groundwater plume particularly in the area of MW4 which reportedly evidenced methyl tertiary butyl <br /> ether(MTBE)contamination of 3,600 ppb in the sample collected on May 6, 1997. PHS/EHD requested <br /> in correspondence dated June 25, 1997 that the third quarter's sampling results be submitted by <br /> September 5, 1997. PHS/EHD has not yet received these results. <br /> Feasibility Analysis <br /> The soil vapor extraction wells which have been installed were screened between 10 and 17 feet bgs. <br /> PHS/EHD understands given the rise in the groundwater table to approximately 10 to 11 feet bgs, that <br /> A Division of San Joaquin County Health Care Services <br />