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Beacon Station No 419 August 13, 1997 Stockton,California Aquifer Testing Report • Laboratory Water Analyses Water samples were collected from the discharged groundwater on May 28 and 30, and June 4, 11 and 16, 1997 Collected samples were submitted under chain-of-custody (CoC) to Kiff Analytical (Kiff), a California Department of Health Services-certified analytical laboratory (ELAN No 2236) located in Davis, California Groundwater samples were analyzed for Total Petroleum Hydrocarbons as gasoline (TPHg) according to EPA Method 8015, benzene, toluene, ethylbenzene, and xylenes (BTEX) according to EPA Method 602 and Methyl-t-butyl ether (MTBE) according to Method 8020 / 602 Copies of the CoC are included in Attachment C The water samples collected from the pumped groundwater (influent) in May and June 1997 indicated concentrations of TPHg between 6,700 parts per billion (ppb) and 38,000 ppb, concentrations of benzene between 960 ppb and 5,300 ppb, and nondetectable concentrations of MTBE (less than 100 ppb) The water samples collected from the discharged (effluent) groundwater in May and June 1997 indicated concentrations of TPHg between nondetectable (less than 50 ppb) and 6,500 ppb, concentrations of benzene between nondetectable (less than 0 50 ppb) and 3,000 ppb, and nondetectable concentrations of MTBE (less than 5 0 ppb) Laboratory results are summarized on Table 1 Copies of the laboratory reports and CoC are included as Attachment C Results_of Aquifer Pumping Tests Observation water-level data collected between May 28 and 30, 1997 indicated measurable drawdown In wells MW-1 (0 43-foot), MW-2 (0 26-foot), and MW-6 (0 51-foot) during the pump test Continued long-term pumping in June 1997 indicated further measurable drawdown in wells MW-1 (0 77-foot), MW-2 (0 40-foot), and MW-6 (0 89-foot) Well MW-1 is located approximately 63 feet southwest of pumping well MW-3, well MW-2 is located approximately 77 feet west of pumping well MW-3, and well MW-6 is located approximately 49 feet northeast of pumping well MW-3 The groundwater measurements recorded by the datalogger during the first 210 minutes of the test were not used because of the submersible pump malfunctioned early in the test Graphs of time vs drawdown, as measured with the data loggers are included in Attachment B Using the time-drawdown method for the datalogger data measured during the two-day pump test, and a pumping rate of 4 0 gpm, the calculated transmrssivrtres (T) were 5,280 gallons per day per foot (gpd/ft) for the MW-6 data and 6,600 gpd/ft for the MW-1 data The calculated storatrvities (S) were 0 024 for the MW-6 data and 0 027 for the MW-1 data Using an aquifer thickness of 19 feet from the boring log for well MW-1, results in an estimated value of hydraulic conductivity (K) of approximately 46 feet per day Using an aquifer thickness of 22 5 feet from the boring log for well MW-6, results in an estimated value of hydraulic conductivity (K) of approximately 31 feet per day 1419 11-rpt HORIZON ENVIRONMENTAL INC