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13-Haul#749-50 Blaes En veronmenral Additional Site Characterization sections A-A' (Figure 5) and B -B' (Figure 6) The traverse of each cross section is shown on Figure 4 In general, the cross-sections indicate that more clayey soil is present on the eastern portion of the site The cross-sections and observations during drilling indicate that the soils beneath the site vary with depth and location Clearly defined soil horizons were not apparent ' 2 6 SITE HYDROGEOLOGY Blaes performed groundwater monitoring at the site in March and September 1999 Groundwater depth measurements collected on March 24, 1999 indicated groundwater levels between approximately 36 and 39 feet bgs These depths were approximately 25 feet higher than previous measurements collected by SOTA ' on September 24, 1997(Table 2) The apparent groundwater flow direction on March 24, 1999 was toward the south(Appendix A) Dissolved benzene concentrations from the March 1999 sampling event ranged from 0 9 to 45 micrograms per liter (pg/L) in groundwater samples collected from six of the seven on-site wells Historical analytical ' data indicate that groundwater from monitor wells MW-1, MW-4 and MW-6 have typically had higher dissolved hydrocarbons concentrations than the other monitor wells(Table 2) Groundwater depth measurements collected on September 3, 1999 indicated that groundwater levels ranged from 46 25 to 49 80 feet bgs These depths were approximately 10 feet lower than measurements taken in March 1999 The apparent groundwater flow direction in September 1999 was toward the northwest (Appendix A) According to Applied Consultants (1993), the groundwater flow direction at the site has vaned from westward to northeastward According to Mr Infirm, of the PHS-EHD, the historical low groundwater level at the site in 1990 was ' approximately 90 feet bgs The current and the historical low groundwater levels are illustrated on the cross- sections(Figures 5 and 6) Historic static water levels and corresponding elevations are included in Table 2 Based on soil sample descriptions(Appendix B), the aquifer beneath the site consists of sand and silty sand with interbedded silt, clayey sand, and clay Well development activities conducted at the new ' monitoring wells have indicated that the saturated sediments can yield approximately 2 to 3 gallons per minute In addition, recent groundwater measurements taken at the newly installed monitoring wells indicate that there is little or no difference in groundwater levels compared to the pre-existing monitor 6