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1444 MARIPOSA ROAD <br /> WKA No. 2938.05 <br /> April 28, 2000 <br /> Page 2 <br /> Prior to purging and sampling, the water level in each well was measured with an electronic <br /> water level indicator and checked for visual signs of free product using new, disposable <br /> polyethylene bailers. No free product, sheen or petroleum hydrocarbon odor was observed in the <br /> monitoring wells. The depth-to-groundwater measurements were used to calculate the volume of <br /> water in each well. Once calculated, approximately three well volumes of water were purged <br /> from each well using a two-inch submersible pump until temperature,pH, and conductivity <br /> readings stabilized and/or the water cleared of sediment. Groundwater was allowed to recharge <br /> to at least 90% at each well prior to obtaining samples. Water samples were then collected <br /> through the sampling pump. Sample water pumped from the wells was poured into appropriate <br /> sample containers provided by the laboratory. The submersible pump was cleaned with a <br /> solution of Liqui-nox and water prior to purging each well to minimize the potential for cross- <br /> contamination. In addition, the wells were sampled in order of increasing concentration based on <br /> previous sampling results. All water removed during sampling and purging operations was <br /> placed in sealed and labeled 55-gallon drums and stored on-site. <br /> The samples were immediately placed in an ice-chest with ice and submitted under chain-of- <br /> custody to a California-certified laboratory for analysis of Total Petroleum Hydrocarbons (TPH) <br /> as gasoline,Benzene, Toluene, Ethylbenzene and Total Xylenes (BTEX)using EPA Method <br /> 8260B. The fuel oxygenates Tert-Butanol,Methyl tent Butyl Ether, Di-isopropyl Ether, Ethyl <br /> tert-Butyl Ether, Tert-Amyl methyl Ether, Ethanol, and Methanol were additionally analyzed <br /> using EPA Method 8260B. <br /> Results of laboratory analysis of water samples obtained from wells MW 1 through MW3 and <br /> MW5 through MW7 revealed no detectable concentrations of TPH as gasoline or BTEX <br /> constituents. TPH as gasoline was detected in the water sample obtained from well MW4 at a <br /> concentration of 50 µg/1. A minor concentration of MTBE(0.78 µg11)was detected in well <br /> MW2 only. Trace concentrations of Tert-butanol was detected in MW2 and MW7 and ethanol at <br /> a concentration of 9.8 µg/1 was detected in MW3. Analytical results for the water samples are <br /> summarized in Tables 2 and 3. Chain-of-custody documentation and laboratory analytical <br /> reports are appended. <br /> Conclusions and Recommendations <br /> Groundwater flow direction during the last three monitoring and sampling events has been to the <br /> south-southeast with a variable gradient. Petroleum hydrocarbons in groundwater in the vicinity <br /> of wells MWI, MW3, MW6, and MW7 have not been detected during the last three sampling <br /> events. TPH as gasoline has decreased to nondetectable levels in wells MW2 and MW5 and has <br /> INK <br /> WALLACE-KUHL <br /> r: <br /> Er ASSOCIATES INC. <br />