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Beacon Station No, 474 August 26, 1997 Stockton California Remedial Testing Report • the discharged groundwater were 100 parts per million (ppm) [or 100,000 parts per billion (ppb)] of TPHg. LaboratoEy Water Anal ses Water samples were collected from pumping well MW-2 on May I3, 16, and 21, and June 4, 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- tertiary-butyl ether(MTBE) according to Method 8020 /602. The water samples collected from pumping well MW-2 in May and June 1997 indicated concentrations of TPHg between 20,000 parts per billion (ppb) and 37,000 ppb; concentrations of benzene between 4,300 ppb and 12,000 ppb; and nondetectable concentrations of MTBE (less than 250 ppb). Laboratory analytical results are summarized in 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 14 and 15, 1997 indicated minimal measurable drawdown in wells MW-1 (0.10-foot), MW-3 (0.11-foot), and MW-4 (0.10- foot) during the pump test. By May 28, 1997 continued long-term pumping still indicated minimal measurable drawdown in wells MW-1 (0.15-foot), MW-3 (0.15-foot), and MW-4 (0.14 foot). Well MW-1 is located approximately 114 feet southwest of pumping well MW- 2; well MW-3 is located approximately 62 feet west of pumping well MW-2; and well MW- 4 is located approximately 85 feet northeast of pumping well MW-2. 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 in May 1997, and a pumping rate of 2.0 gpm, the calculated transmissivities (T) were 3,429 gallons per day per foot (gpd/ft) for the MW-1 data and 3,200 gpd/ft for the MW-3 data. The calculated storativities (S) were 0.0045 for the MW-1 data and 0.0113 for the MW-3 data. Using an aquifer thickness of 15 feet from the boring log for well MW-1, results in an estimated value of hydraulic conductivity (K) of approximately 30 feet per day. Using an aquifer thickness of 15 feet from the boring log for well MW-3, results in an estimated value of hydraulic conductivity (K) of approximately 28 feet per day. Graphs of distance vs. drawdown, as measured with the water level indicators in wells MW- 1, MW-3, and MW-4 are included in Attachment B. Using the distance-drawdown method for the long-term water level indicator data collected in June 1997, and an average pumping rate of 2.0 gpm, the calculated transmissivity (T) was 13,367 gpd/ft, and the calculated 1474.11-rpt 3 HORIZON ENVIRONMENTAL INC.