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� v o ASSOC IATES INC The groundwater samples collected from each well were submitted to State-certified Argon Laboratories, Inc (ELAP Cert No 2359) for chemical analysis of TPHg and TPHd utilizing ' EPA method 8015 modified, and BTEX utilizing EPA method 8020, and MTBE, ethyl tertiary butyl ether (ETBE), di-isopropyl ether (DIPE), tertiary amyl ether (TAME), and tertiary butyl alcohol (TBA) by EPA method 8260 Groundwater well purge and sample logs are contained in ' Appendix A 2,^2 H dro eolo Water level measurements were collected from wells MW1 through MW6 on September 24, ' 2001 Water levels ranged from 8 61 to 14 01 feet below the tops of the well casing elevations The water level data were used 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 south-southwest The average hydraulic gradient on September 24, 2001 was calculated to be 0 002 ft/ft or approximately 11 ft/mile A summary of groundwater monitoring data is presented in Table 1 ' 2.3 Analytical Results The groundwater samples collected from wells MWI, MW5, and MW6 contained no detectable concentrations of TPHd, TPHg, BTEX, MTBE, and/or oxygenate fuel additives The groundwater sample collected from well MW3 contained no detectable concentrations of TPHg, ' BTEX, or MTBE, but did contain low concentrations of TPHd The groundwater samples collected from wells MW2 and MW4 contained no detectable concentrations of benzene, toluene, ethylbenzene, or MTBE The groundwater samples from wells MW2 and MW4 ' contained low concentrations of xylenes, moderate concentrations of TPHg, and elevated concentrations of TPHd Analytical results of groundwater samples are summarized in Table 2 ' An isoconcentration map showing the extent of TPHd impacted groundwater is shown on Figure 4 Laboratory data sheets and chain-of-custody documentation for groundwater samples are contained in Appendix B 3.0 DISCUSSION ' The following paragraphs summarize the results of the subsurface investigations performed at the project site 1 Based on previous work at the site, lean clay, lean clay with sand, and clayey sand is present from the surface to approximately 15 feet bgs This extends beyond the vadose zone and into the capillary fringe From 15 feet bgs to approximately 45 feet bgs, soil ' generally consisted of varying types of sand with a few layers of lean clay From 45 feet bgs to approximately 51 feet bgs, soil consisted of well graded sand Boring logs for soil borings and monitoring wells are included in Appendix C w 1625001reports\CAP doc 3