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f M F D S SERVICES, INCORPORATED MPDS-UN6015-01 April 29 , 1994 Unocal Corporation 2000 Crow Canyon Place, Suite 400 P O Box 5155 San Ramon, California 94583 Attention Mr David B DeWitt RE Semi-Annual Data Report Unocal Service Station ##6015 601 E Kettleman Lane Lodi California Dear Mr DeWitt This data report presents the results of the most recent monitoring and sampling of the monitoring wells at the referenced site by MPDS Services, Inc RECENT FIELD ACTIVITIES The monitoring wells that were monitored and sampled during this semi-annual period 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 directions during the most recent semi-annual period are shown on the attached Figures 1 and 2 Ground water samples were collected on March 30 and 31, 1994 Prior to sampling, the wells were each purged of between 4 and 10 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 appropri- ate, 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,California 94520 Tel (510) 602-5120 Fax (S 10)689-1918