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i <br /> Z <br /> � z z z <br /> z a a it <br /> iED E)0 <br /> N ¢ SERVICES, INCORPORATED <br /> a a y <br /> MPDS-UN6981-07 <br /> May 22 , 1995 <br /> Unocal Corporation <br /> 2000 Crow Canyon Place, Suite 400 <br /> P.O. Box 5155 25'T <br /> San Ramon, California 94583 <br /> Attention Mr. David J Camille <br /> RE Quarterly Data Report <br /> Unocal Service Station :46981 <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 /> The monitoring 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 April 26 and 27, 1995 Prior to <br /> sampling, the wells were each purged of between 17 and 29 gallons of <br /> 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 an a cooler, <br /> on ice, until delivery to a state-certified laboratory MPDS Services, <br /> Inc . transported the purged ground water to the Unocal Refinery located <br /> in Rodeo, California, for treatment and discharge to San Pablo Bay <br /> 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 /> of Total Petroleum Hydrocarbons (TPH) as gasoline and benzene detected <br /> 2401 Stanwell Drive Suite 300 Concord,CA 94520 <br /> TEL (5 10)602 5120 FAX (5 10)689-1918 <br />