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BROWN AND CALDWELL <br /> CONSULTING ENGINEERS } <br /> f ZS?A <br /> I <br /> June 29, 1989 J U L 1989 <br /> ENVIRONMENTAL.HEA!hli <br /> P1=RM?TE��R1ll��, <br /> Ms. Laurie Cotulla <br /> Registered Sanitarian <br /> Environmental Health Division <br /> San Joaquin Local Health District <br /> 1601 East Hazelton Avenue <br /> Stockton, California 95201 017-3174-0511 <br /> Subject: Quarterly Groundwater.Sampling Results, ARCO Station 2093, <br /> Tracy' California <br /> Dear Mr. Christie: <br /> This letter report describes the February ,groundwater sampling at ARCO Products Company <br /> 4 (ARCO) Station 2093 at 3425 Tracy Boulevard; Tracy, California'. ARCO has authorized <br /> quarterly water' level measurements and groundwater sampling for analysis of benzene, <br /> ethylbenzene, to and xylene (BETX) and .total petroleum hydrocarbons (TPH). On <br /> February 22, 1989, Brown and Caldwell personnel collected groundwater samples from the <br /> four on-site monitoring wells (ATR-l; ATR=2, -ATR-3, and ATR-4) which were installed in <br /> March, 1987. The purpose of the monitoring wells is to characterize hydrocarbon occurrence <br /> in groundwater beneath the site. <br /> Figure 1 shows the location of the monitoring wells, benzene concentrations in groundwater <br /> samples collected from these wells, and the'direction of groundwater flow at the time of the <br /> February, 1989 sampling. <br /> Field Methods <br /> Prior to sampling the wells, a diaphragm suction pump :was used to purge approximately <br /> three well volumes of water from each well. Armour Petroleum Company of Vacaville, <br /> California, operated the pump. The pH and specific conductance of the discharged water <br /> were monitored 'periodically and found to be-reladvely stable during the evacuation of Figure 1 <br /> water, Groundwater from each well was sampled using a teflon bailer equipped with a <br /> bottom-emptying valve. The sample was drained directly from the bottom valve into four <br /> 40-milliliter glass bottles and one 1-liter amber glass bottle with a Teflon-lined septa. The <br /> samples were stored on ice in a closed ice chest from thetime of collection through delivery <br /> to the laboratory. All purging and sampling equipment was washed with laboratory-grade <br /> detergent and tap water then rinsed with deionized water :before each use. All groundwater <br /> generated during the purging and sampling process was disposed of by Armour Petroleum <br /> Company for ARCO. <br /> 723 S STREET SACRAMENTO,CALIFORNIA 9 5814-709 2•(916)444-0123 <br />