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August 26, 1997 Beacon Station No.474 Remedial 'Testi,, Re art Stockton California rained sand. with some fine-g generally the site consisted predominantly of clayey silt (ML) groundwater flow g Groundwater data collected previously had shown a gentle g beneath the site,with an average gradient of less than 0.01 (E]Dorado testing showed a towards the southeast b gradient of less Environmental, April 1997). Groundwater data collected after the pump le groundwater trough flowing to the southeast beneath the site, with a g UST's, and gent g 1997 Locations of the soil borings, wells MW-1 through MW-5 are shov n on the Site plan(Figure 2). than Q.Q1 (El Dorado Environmental, July groundwater monitoring A uifer Pum in Tests in accordance with the Horizon Site Safety Plan dated April 29, Field work was conductedpumping tests at the 1997. Between May 13 and June 5, 1997, Horizon shallow water-bearing zone beneath the site. site to evaluate aquifer characteristics of the s p to urnp jests were performed by using a 4-inch diametermeasuring wdown in observvation wells The to _ groundwater from monitoring well MW 2, an loggers used to continuously record water MW-t,MW-3, and MW-4- Automated data Additionally, electronic water level level data in observation wells MW-1 and MW-3 well MW-2 was to measure water levels to the nearest Q.OI foot observation wells indicators were used well MW-2. Monit g MW-1, MW-3 and MW-4, as well aspum pumping g pumping well because historically this well episodes h d the hig est selected as thep p and monitoring concentrations of benzene detected during sampling tests were initiated at the site. Initial gr On May oundwater levels weze 13 1997, pumping s. During a preliminary test, found to be present at depths between 63.7 to 64.6 feet bg allons per minute (gpm) groundwater was in pumped from well MW-2�a er for°150Qminutes back to the initial g for 30 minutes, then well MW-2 was allowed vel. On May 14, 1997, the pumping test was started. Groundwater was Pump- water le rn far 54 hours and 11 minutes. After completion of the ateftorn we MW-2 at a rate of 2.0 gp purpose of this urn test, pumping of MW-2 continued at the sitetilp n5, effects on peel MW-2- pump in was to evaluate the long-term p A. Graphs of additional pumping Water-level data Horizon's Field Methods and procedures resented in Bent groundwater drawdown measurements are p Contour Map collected on May 2g, 1997 was used to construct the Groundwater Pumping (Figure 3). 500 gallon of groundwater was produced during the pumping for the Approximately 6, g test, the pump continued to operate at aquifer testing. After completion of the two-day Pump The m at the site until June 5, 1997. At that tinne, flow rates between 1.4 gpm and 2.0 gP ed from well MW~2 210 gallons of groundwater had been pip approximately 27, um in well to a flowmeter, and then D See it e pal pumped groundwater was routed frompumping sanitary sewer system under a Municipal UtilitiesdDepfVetuntwAugust 3Q, of Stocktonp 1995, permit for Wastewater Discharge of Stockton MUD discharge permit, the allowable limits for i 2000. According to the City 2 HORIZON ENVIRONMENTAL INC. 1474.11-rpt