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1 <br /> Working To Restore Nature <br /> and within a radius of about 20 feet of the former 1,000 gallon gasoline UST tank pit A soil <br /> vapor extraction system was constructed at the site and began operating July 23, 1993 <br /> Quarterly groundwater monitoring results have shown detectable levels of petroleum <br /> hydrocarbons in the monitoring wells in the past (Table 1). <br /> GROUNDWATER SAMPLING AND GRADIENT EVALUATION <br /> RESNAPersonnel Performed the latest quarterly groundwater monitoring of monitoring wells <br /> on September 9, 1994. At the direction of SJCPHS in a conversation on July 14, 1994, the <br /> number of wells to be sampled was decreased from six to three. Field work consisted of <br /> measuring depth-to-water(DTW) levels in all wells, collecting groundwater samples from wells <br /> MW-1, MW-3, and MW-4, and submitting groundwater samples for laboratory analysis <br /> 1 <br /> Water level measurements were collected from wells MW-1 through MW-6 The depth to water <br /> ' ranged from 67.10 to 67 76 feet below top of well casing elevation. Groundwater elevations <br /> have decreased an average of 2.82 feet since June 2, 1994 The water level data were used to <br /> develop the groundwater elevation contour map (Plate 3). Assuming that horizontal isotropic <br /> ' conditions prevail, groundwater in the uppermost aquifer beneath the site flowed in a <br /> northeasterly direction The hydraulic gradient on September 9, 1994 was calculated to be 0.001 <br /> ft/ft or about 5 feet/mile. These data indicate a slight change in gradient direction but no change <br /> in magnitude when compared with the previous quarterly monitoring results A summary of <br /> groundwater monitoring data is presented in Table 2. Groundwater elevations are referenced <br /> to feet mean sea level. <br /> iGroundwater samples were collected from three shallow groundwater monitoring wells, MW-1, <br /> MW-3, and MW-4. Prior to collection of groundwater samples a minimum of three well casing <br /> volumes were purged. The depth-to-water, pH, electrical conductivity, and temperature were <br /> measured and allowed to stabilize before groundwater samples were collected No evidence of <br /> measurable floating product or hydrocarbon vapor was noted in the water samples. Samples <br /> ' were then collected from each well using disposable bailers Purge water was contained in 55 <br /> gallon DOT approved drums and stored on-site pending proper disposal. Purge water from <br /> previous sampling was disposed of at an approved facility <br /> Theroundwater samples collected from each well were submitted with Cham of Custody <br /> g P Y <br /> Record to Sequoia Analytical Laboratories, a State Certified laboratory (FLAP#2000). Samples <br /> ' were analyzed for total petroleum hydrocarbons as gasoline (TPHg), total petroleum <br /> hydrocarbons as diesel (TPHd), and benzene, toluene, ethylbenzene, and total xylenes (BTEX) <br /> ' utilizing EPA methods 8015/8020. <br /> Groundwater well purge and sample logs are provided in Appendix A. <br /> 1 <br /> UW561QUARTLWQMR19%DRF 2 <br />