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M'MN <br /> Brown and Caldwell <br /> Consultants <br /> t 9,o ra 3SBt„-fJv; <br /> January 14, 1991 <br /> Mr. Kyle Christie <br /> ARCO Products Company <br /> 2000 Alameda de las Pulgas <br /> Post Office Box 5811 <br /> San Mateo, California 94402 017-3173-71/1 <br /> Subject: Third Quarter 1990 Sampling Results ARCO Station 2133, <br /> 2908 Uenjamin Holt Drive, Stockton,California <br /> Dear Mn Christie; <br /> On September 17, 18,and 19, 1990, Brown and Caldwell collected groundwater samples from <br /> 13 monitoring wells at the subject site. The site is on a.:alternating schedule for sampling with <br /> eight wells sampled during the second and fourth quarter,and 15 wells sampled during the first <br /> and third quarters. The September 1990 sampling ent is the third quarterly sampling of 1990. <br /> It is also the second sampl-ng event under Task Ogler 2133-90-2. <br /> Monitoring wells E-3 and E-6 were not sampled this quarter because they were dry. <br /> Additionally,most sample collection was slow and difficult because of very slow recharge rates. <br /> Monitoring wells E-5,E-7, E-9, $-10, E-11, and E-12 were especially stow to recharge. This <br /> condition may be the result of clogging of the well screens with clayey formational materials. <br /> 'r <br /> Quarterly Sampling <br /> Prior to sampling wells PR-I,PR-2,BHD-I, BHD-2,E-2,E-4,E-5, E-7,E-8,E-9, E-10,E-I1,-, f <br /> and E-12,Armour Petroleum Servic,s used a diaphragm pump to purge approxir.1ately three well•' - <br /> casing volumes of water from each well. Each well, was sampled using a separate,disposable, <br /> polyethylene bailer equipped with a bottom-emptying valve-The sample was transferred directly <br /> through the bottom valve it two 40-milliliter glass bottles with Teflon-lined septa. Cross <br /> contamination of samples was minimized through the use of sepLne disposable bailers and hoses <br /> on the diaphragm pump at each well. <br /> The sarnples were stored on ice and kept under chain-of-custody from the time of collection <br /> through delivery to Eureka Laboratories, in Sacramento, California. All of the samples were <br /> 1 analyzed for total petroleum hydrocarbons(TPM and benzene,ethylbenzene,toluene,and xylenes <br /> (BETX) by U.S. Environmrn'tal Protection Agency (EPA) Method 8035, modified with EPA <br />