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C 0 a ' z z z N a DOSERVICES, INCORPORATED saau R94 EI � MPDS-UN6981-03 May 23 , 1994 Unocal Corporation 2000 Crow Canyon Place, Suite 400 P O Box 5155 San Ramon, California 94583 Attention Mr David J Camille RE Quarterly Data Report Unocal. Service Station ##6981 4707 Pacific Avenue Stockton, California Dear Mr Camille This data report presents the results of the most recent quarter of monitoring and sampling of the monitoring wells at the referenced site by MPDS Services, Inc 40 RECENT FIELD ACTIVITIES The monitoring wells that were monitored and sampled during this quarter are indicated in Table 1 Prior to sampling, the wells were checked for depth to water and the presence of free product or sheen The monitoring data and the ground water elevations are summarized .in Table 1 The ground water flow direction during the most recent quarter 3s shown on the attached Figure 1 Ground water samples were collected on April 25 and 26 , 1994 Prior to sampling, the wells were each purged of between 12 and 19 5 gallons of water During purging operations, the field parameters pH, temperature , and electrical conductivity were recorded and are presented in Table 2 Once the field parameters were observed to stabilize, and where possible, a minimum of approximately four casing volumes had been removed from each well , samples were then collected using a clean Teflon bailer The samples were decanted into clean VOA vials and/or one-liter amber bottles, as appropriate, which were then sealed with Teflon-lined screw caps, labeled, and stored in a cooler, on ice, until delivery to a state-certified laboratory MPDS Services , Inc transported the purged ground water to the Unocal Refinery located in Rodeo, California, for treatment and discharge to San Pablo Bay under NPDES permit 2401 Stanwell Drive Suite 400 Concord CA 94520 TEL (510) 602 5120 FAX (510) 689-1918