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ti <br /> z z Z <br /> Q . o a <br /> DOSERVICES, <br /> INCORPORATED <br /> • a a a v �-----r. <br /> MPDS-UN6981-10 <br /> February 15 , 1996 <br /> Unocal Corporation <br /> 2000 Crow Canyon Place, Suite 400 <br /> P O Box 5155 <br /> San Ramon, California 94583 <br /> Attention- Mr David J Camille <br /> RE Quarterly Data Report <br /> Unocal Service Station # 6981 <br /> 4707 Pacific Avenue <br /> Stockton California <br /> Dear Mr Camille <br /> This data report presents the results of the most recent quarter of <br /> monitoring and sampling of the monitoring wells at the referenced site <br /> by MPDS Services, Inc <br /> RECENT FIELD ACTIVITIES <br /> 01Themonitoring wells that were monitored and sampled during this <br /> quarter are indicated in Table 1 . Prior to sampling, the wells were <br /> checked for depth to water and the presence of free product or sheen <br /> The monitoring data and the ground water elevations are summarized in <br /> Table 1 The ground water flow direction during the most recent <br /> quarter is shown on the attached Figure 1 <br /> Ground water samples were collected on January 24 and 25, 1996 Prior <br /> to sampling, the wells were each purged of between 17 . 5 and 31 5 <br /> gallons of water During purging operations, the field parameters pH, <br /> temperature, and electrical conductivity were recorded and are <br /> presented in Table 2 Once the field parameters were observed to <br /> stabilize, and where possible, a minimum of approximately four casing <br /> volumes had been removed from each well, samples were then collected <br /> using a clean Teflon bailer The samples were decanted into clean VOA <br /> vials and/or one-liter amber bottles, as appropriate, which were then <br /> sealed with Teflon-lined screw caps, labeled, and stored in a cooler, <br /> on ice, until delivery to a state-certified laboratory. Field blank, <br /> Equipment blank and Trip blank samples (denoted as ESI, ES2 and ES3 <br /> respectively) were also collected for quality assurance and control <br /> MPDS Services, Inc transported the purged ground water to the Unocal <br /> Refinery located in Rodeo, California, for treatment and discharge to <br /> San Pablo Bay under NPDES permit <br /> ANALYTICAL RESULTS <br /> The ground water samples were analyzed at Sequoia Analytical Laboratory <br /> and were accompanied by properly executed Chain of Custody <br /> documentation The analytical results of the ground water samples <br /> collected to date are summarized in Tables 3 and 4 The concentrations <br /> 2401 Stanwell Drive Suite 300 Concord CA 94520 <br /> TEL (510)602-5120 FAX (5 10)689-1918 <br />