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I� v , A S S O C I A T E S I NC . probe capable of measuring with an accuracy of 11100 of a foot. Groundwater elevation data are presented in Table 3. =' 2.5 Groundwater Sampling and Analysis t="! On March 11, 1999, groundwater samples were collected from wells MW-1 through MW-6. The } samples were collected after purging a minimum of three well volumes and stabilization of electric conductivity, pH, and temperature. Field development/purge logs are presented in Appendix C. G Subsequent to purging, groundwater was sampled and transferred to appropriate sample containers, using clean, disposable bailers with bottom emptying devices to reduce volatilization. Sample containers were then labeled with sample identification, placed on ice, and shipped under chain-of-custody to Sequoia Analytical. The groundwater samples from wells MW-1 through MW-6 were analyzed by Sequoia Analytical for TPHg, BTEX, and methyl tertiary butyl ether (MTBE) by EPA methods 801518020. Samples from wells MW-4, MW-5, and MW-6 were also analyzed for oxygenate fuel additives by EPA <: method 8260. Groundwater analytical results are summarized in Table 2, and laboratory data sheets are presented in Appendix D. 3.0 SUBSURFACE CONDITIONS 3.1 GeoloQy == Soil in borings MW-4, MW-5, and MW-6 generally consisted of lean clay from the ground surface to depths between 26 to 28 feet bgs, the maximum depth explored. Each boring had sand with varying amount of silt and/or gravel from depths between 11.5 to 15 feet bgs and 16.5 to 20 k ' feet bgs. Boring MW-5 also had poorly graded sand from 10.5 to 11 feet bgs and sandy clay from between 21.5 to 25 feet bgs and 26 feet bgs, the maximum depth explored. 3.2 Hydro-geology Water level measurements were collected from wells MW1 through MW6 on March 11, 1999. Water levels ranged from 6.93 to 8.55 feet below the tops of the well casing elevations. Water eet since January 1999. The water level data were used levels have increased an average of 0.28 f r`. to develop the groundwater elevation contour map (Figure 3). Assuming that horizontal isotropic conditions prevail, groundwater in the uppermost aquifer beneath the site flowed towards the ;==3 north-northeast. The average hydraulic gradient on March 11, 1999 was calculated to be 0.002 ft/ft or approximately 11 ft/mile. These results are consistent with results of previous monitoring events. A summary of groundwater monitoring data is presented in Table 3. w:113099\reports%sumwel.doc 4 F:.'f