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S�C HLALTH SERVIC'eE PUBLr <br /> SAN JOAQUIN COUNTY ' h:2+ <br /> ENVIRONMENTAL HEALTH DIVISION <br /> Karen Furst, M.D., M.P.H., Health Officer <br /> 304 East Weber Avenue, Third Floor • Stockton, CA 95202 <br /> 2091468-3420 FILE <br /> C <br /> JAY L & VL SINCLAIR <br /> SINCLAIR TRUCKING <br /> 3780 LINNE ROAD AUG 0 6 1999 <br /> TRACY CA 95376 •7 <br /> RE: SINCLAIR TRUCKING SITE CODE: 1916 <br /> 3780 W LINNE ROAD <br /> TRACY CA 95376 <br /> San Joaquin County Public Health Services Environmental Health Division (PHS/EHD) has reviewed the <br /> files for the above referenced site including recent and historic quarterly ground water sampling data <br /> submitted to this office. <br /> A report titled Subsurface Investigation dated July 21, 1999 by Geological Technics Inc. (GT) for the <br /> above referenced site provides incomplete groundwater monitoring data. The report lacks benzene <br /> analytical results for monitor well MW-1 sampled February 19, 1999(see BSK Certificate of Analyses for <br /> MW-1 dated March 12, 1999). Please provide PHSIEHD with benzene analytical data for Monitor Well <br /> MW-1. In the event benzene data is not available please carefully review future reports for complete data <br /> sets to avoid data loss and the potential for costly resampling. 1n addition, it appears that MW-4 may not <br /> have been used to calculate groundwater gradient and flow direction. Please submit a copy of the <br /> registered surveyors well head elevation report for MW-4, a copy of the calculations used to <br /> determine the groundwater gradient and benzene data for MW-i from the February 19, 1999 <br /> monitoring event to PHS/EHD before September 1, 1999. <br /> Correspondence attached to the July 21, 1999 Subsurace Investigation report from GT dated Julv 27, 1999 <br /> indicates that Del-Tech will perform the next groundwater monitoring event on August 5, 1999. GT's <br /> request to perform standard monitor well sampling for TPH-G, BTEX,and Oxygenated Fuel Compounds is <br /> approved. However, PHS/EHD cannot approve collection of samples for natural attenuation parameters at <br /> this time for the following reasons. <br /> Sampling for natural attenuation parameters is premature and may not be cost effective. The soil and <br /> groundwater plume is currently undefined. Consecutive quarterly groundwater monitoring has not <br /> occurred. Small changes in depth to groundwater observed in monitor wells and concurrent fluctuations in <br /> contaminant concentrations suggest that as groundwater rises into the contaminated vadose zone leaching <br /> of hvdrocarbons into groundwater results, in this scenario a steady state plume condition cannot be <br /> documented. <br /> Prior to implementing an intrinsic bioremediation parameter sampling program initial screening and a more <br /> thorough conceptual model of the plume must be developed. PHS/EHD recommends that the responsible <br /> parry and consultant refer to and follow existing guidance documents from the United States Environmental <br /> Protection Agency regarding physical and biological remediation sampling (also referred to as Natural <br /> Attenuation in, How to Evaluate Alternative Cleanuq Technolo ies for Underground Stora e Tank Sites, <br /> USEPA, 1994, EPA 510-B-94-003)- <br /> A Division of San Joaquin County Health Care Services <br />