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i C7 [7 (7 u z a , O a rp� a oPE) SERVICES, INCORPORATED MPDS-UN5098-09 January 24 , 1996 Unocal Corporation - 2000 Crow Canyon Place, Suite 400 P O Box 5155 San Ramon, California 94583 Attention: Ms Tina R Berry RE Quarterly Data Report Former Unocal Service Station #5098 5606 Pacific Avenue Stockton- California -- -_ --- Dear Ms Berry 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 . RECENT FIELD ACTIVITIES The Unocal monitoring wells that were monitored and sampled during this quarter are indicated in Table 1 Prior to sampling, the Unocal wells were checked for depth to water and the presence of free product or sheen The monitoring data and the ground water elevations for the Unocal wells are summarized in Table 1 . A point monitoring event was conducted with the consultant for the nearby Montgomery Ward site on December 19 1995 The monitoring data collected for Montgomery Ward' s monitoring wells (provided by Environ- mental Audit, Inc ) are summarized in Table 4 The ground water flow direction in the vicinity of the Unocal and Montgomery Ward sites during the most recent quarter is shown on the attached Figure 1 . Ground water samples were collected from the Unocal wells on December 19, 1995 Prior to sampling, the Unocal wells were each purged of between 12 and 18 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 stared in a cooler, on ice, until delivery to a state-certified laboratory Field blank, Equipment blank and Trip blank samples (denoted as ES1 , ES2 and ES3 respectively) were also collected for quality assurance and control 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 300 Concord CA 94520 TEL (510)602-5120 FAX (510)689-1918