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BROWN AND CALDWELL <br /> CONSULTING.ENGINEERS *' <br /> 1P xv� <br /> December 5, 1988 <br /> � 10 <br /> Ms. Laurie Cotulla <br /> Registered Sanitarian <br /> Environmental Health Division <br /> San Joaquin. Local Health District <br /> 1601 East Hazelton Avenue.. j <br /> Stockton, California 95201 017-3174-04/1 <br /> Subject: Quarterly Sampling Results, ARCO :Station 2093, <br /> 3425 Tracy Boulevard, Tracy, California <br /> Dear Ms. Cotulla: <br /> On September 29, 1988, Brown and Caldwell collected groundwater samples from the four <br /> monitoring wells.:at the subject site.. <br /> Quarterly Sampling <br /> Prior to sampling the wells, -a centrifugal pump was, used .to purge approximately three well <br /> volumes of water from each well. -Groundwater from each `well was then. sampled using a <br /> Teflon bailer equipped with a bottom-emptying valve. The sample was then drained I <br /> directly from the bottom valve into four 40-milliliter glass,bottles and a� 1-liter amber glass <br /> bottle with Teflon-lined septa. The samples were stored on ice from the. time of collection <br /> through delivery, to Eureka Laboratories. All of the samples were analyzed for benzene, <br /> ethylbenzene, toluene, and xylene (BETX) using. U.S.. Environmental Protection Agency <br /> (EPA) Method 602, total petroleum fuel hydrocarbons '(TPH) using EPA Method '8015, <br /> modified, and total lead using EPA Method 6010. The complete laboratory reports .are <br /> enclosed. All groundwater produced during well sampling was contained and !temporarily <br /> stored on site in'55-gallon drums pending results of the analytical-tests_ <br /> All constituents . in the groundwater .samples from well ATR-i and ATR-2 are below <br /> detection limits. BETX constituents are detectable in the -samples from. wells .ATR-3 and <br /> ATR-4. In these two samples, 'benzene, - and toluene concentrations exceed 'California--___ � <br /> Department of Health Services,drinking water action levels. <br /> BETX concentrations in wells ATR-3 and ATR4 have increased since June 1988. Table,'! <br /> summarizes the constituent concentrations for December, March, June,' and 'September 1988. <br /> ( <br /> I <br /> 723 8 STREET SACRAMENTO,CALIFORNIA 9 5814-709 2•(916)444-0123 <br /> F <br />