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h Remedial Action Plan-Tosco 76 Branded Facility No. 11195 June 21, 1999 transportation was performed by WMIS. The water was transported to the Tosca Refinery for disposal. A total of approximately 102,760 gallons of groundwater were removed from the former and present UST pits and transported to the Tosco Refinery between January 1999 and March 26, 1999. The groundwater wells Dave been monitored and samples on a quarterly or semi-annual to basis since 1993. The most recently collected groundwater samples, collected on March 22, 1999, contained petroleum hydrocarbons at concentrations ranging from not detected to 65,000 ppb (MW- 5) of TPHg, not detected to 95,000 ppb (MW-5) of MtBE, and not detected for benzene. Depth to water has historically ranged between approximately 6 to 12 feet below top of casing (TOC). The groundwater flow direction has ranged from southeast to southwest with an average gradient of 0.001 feet/feet or less (Alisto, 1999; Blaine Tech Services, Fourth Quarter 1998 Groundwater Monitoring Report, dated May 1999; and BP letter to the SJCEHD, dated May 3, 1999). DISCUSSION OF RECENT FIELD WORK AND ANALYTICAL RESULTS On April 9, 1999, GR personnel witnessed the removal of approximately 5,000 gallons of groundwater from the former UST backfill utilizing the conductor casing. The groundwater was pumped into a 5,000-gallon vacuum truck by WMIS and transported to the Tosco Refinery for disposal. After groundwater removal, a water sample, labeled CC-1, was collected from the conductor casing. Groundwater sample CC-1 was submitted to Sequoia Analytical (Sequoia), in Walnut Creek, California (ELAP #/1271), where it was analyzed for TPHg, BTEX, and MtBE. The sample contained 5.3 ppb of benzene, 6,300 ppb of MtBE, and was reported as not detected for all other analytes. Groundwater sample analytical methods and data are summarized in Table 1. Copies of the laboratory reports are attached. In conjunction with the April 9, 1999 groundwater purging and sampling, GR conducted a performance test to qualitatively analyze of the radius of influence generated during removal of 5,000 gallons of groundwater from the conductor casing. During pumping, GR personnel collected depth to water (DTW) readings from the conductor casing and on-site monitoring wells MW-3, MW-4, and MW-6 (Figure 2). These wells were used as observation wells. DTW readings were collected continuously, beginning prior to initiation of groundwater pumping until 125 minutes after completion of pumping activities, for a cumulative total of 160 minutes. The conductor casing was purged for 35 minutes to fill the 5,000-gallon vacuum truck, at which time the casing was beginning to dewater. The maximum observed drawdown in the conductor casing was 1.92 feet. Observation well MW-3, located approximately 45 feet from the conductor casing, showed a drawdown of approximately 0.70 feet after 55 minutes. Drawdown in observation well MW-4, located approximately 8 feet from the conductor casing, was approximately 0.38 feet after 40 minutes. Observation well MW-6, located approximately 114 feet from the conductor casing, showed a drawdown approximately 0.20 feet after 75 minutes. Groundwater drawdown data are summarized in Table 2. 140193.07-1 4