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B R O W N AND rj jE <br /> 1 15v1 1 �1Qi'4 E�� '�`L HEE At TIi <br /> C A L D W E L L 96 OCT 15 P11 I <br /> October 8, 1996 <br /> Ms. Mary Meays <br /> San Joaquin County <br /> Public Health Service <br /> 304 East Weber Avenue <br /> Stockton,California 95202 017-3316-01/1 <br /> Subject: Response to the August 14, 1996 Letter from San Joaquin County <br /> regarding ARCO Facility.2133,Stockton,California <br /> Dear Ms. Meays: <br /> I <br /> Brown and Caldwell (BC) received a letter from you dated August 14, 1996 regarding ARCO <br /> Facility 2133 located at 2908 Benjamin Holt Drive, Stockton. The letter contained comments <br /> on the First 1996 quarterly groundwater monitoring report which was submitted to San i <br /> Joaquin County, Public Health Services, Environmental Health Division (PHS/EHD) orf- <br /> June <br /> riJune 7, 1996. The purpose of this letter is to address the comments contained in the <br /> August 14, 1996 letter. <br /> Quarterly Sampling <br /> The PHS/EHD letter indicates that "the minimum recharge of 80% was not achieved for each <br /> well prior to sampling....PHS/EHD requests that the groundwater wells recharge to at least j <br /> 80% before samples are collected". Upon review of the field data sheets we have determined j <br /> that the majority of wells were sampled after achieving 80% recharge. However, as you <br /> indicated, some of the wells did not achieve 80% recovery prior to sampling. The sampling <br /> contractor has assured us that in future sampling events, wells will not be sampled until 80% <br /> recharge is achieved. <br /> Groundwater Extraction Performance Evaluation <br /> 1 <br /> PHS/EHD states that slightly more than 12 million gallons have been extracted and removed <br /> through the groundwater extraction system since system modifications and restart in 1991, and <br /> that 42 gallons of free product have been removed. Between 1984 and 1987, nearly 20 million <br /> gallons of groundwater were extracted and discharged to the sewer. In addition, about 600 <br /> gallons of free product were removed following a gasoline release which occurred in the UST <br /> piping in 1984. The 42 gallons of free product removal reported in the First 1996 quarterly <br /> report reflects product removed from monitoring well E-10 and vapor extraction well V-3 <br /> 3316\CORRFS MTR-3.DOC <br /> Environmental Engineering And Consulting•Analytical Services <br /> 9616 MICRON AVENUE, P.O. Box 13449, SACRAMENTO, CA 95813-3449 <br /> (916) 444-0123 FAX (916) 856-5211 <br /> _ _ 1 <br />