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4- e <br /> PUBLIC nEALTH SvPQ.u,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 . <br /> ikS.R�'�P <br /> 209/468-3420 <br /> KLYE CHRISTIE AUG 1996 <br /> ARCO PRODUCTS COMPANY <br /> PO BOX 612530 <br /> SAN JOSE CA 95008 <br /> RE: ARCO Station #2133 SITE CODE: 1021 <br /> 2908 West Benjamin Holt Drive <br /> Stockton CA 95207 <br /> San Joaquin County, Public Health Services Environmental Health Division (PHS/EHD) has <br /> completed review of the "First Quarter 1996 Groundwater Monitoring Report" dated June <br /> 7, 1996 and prepared by Brown and Caldwell. PHS/EHD has the following comments for <br /> your consideration. <br /> Quarterly Sampling <br /> As you are aware, PHS/EHD makes periodic inspections of sampling events, but cannot <br /> provide inspections of each sampling event. Therefore, PHS/EHD reviews the sample field <br /> data sheets that are included with the quarterly reports. PHS/EHD requests that the depth <br /> to water measurement be collected prior to sampling, following the completion of purging <br /> activities. The field notes from the March 19, 1996 sampling event indicated that the <br /> minimum recharge of 80% was not achieved for each well prior to sampling. For example, <br /> the initial depth to water measurement for monitoring well E3 was 10.10' and the depth to <br /> water at the time of sampling was 13.40'. Since the total depth of the well was 18.72, <br /> the well only recovered to 62%. The time between the first water level measurement and <br /> sampling was approximately 13 minutes. PHS/EHD requests that groundwater wells <br /> recharge to at least 80% before samples are collected. <br /> Groundwater Extraction Performance Evaluation <br /> The Groundwater Extraction System Operation Report, First Quarter 1996 and Chart 2. <br /> Cumulative Hydrocarbons Removed (as TPH-G) Vs. Time indicated that 42 gallons of free <br /> product had been removed to date and that approximately 12,000,000 gallons of <br /> groundwater had been extracted. In fact, the groundwater extraction system was installed <br /> in 1984 as a free product recovery system and modified for use as a groundwater <br /> extraction system in 1986. Reportedly through March 1987, a total of 600 gallons of free <br /> product was removed and 19,842,800 gallons of groundwater had been extracted and <br /> discharged to the City of Stockton sanitary sewer. Since April 16, 1991, when the <br /> groundwater extraction system was re-started and through February 14, 1996, when the <br /> groundwater extraction system was indefinitely shut down, approximately 12,097,022 <br /> gallons of groundwater was extracted and discharged. Summaries of remedial actions <br /> should include all the information which is available. <br /> A Division of San Joaquin County Health Care Services <br />