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� � � R S A S S O C I A T E S I N C volatilization Groundwater samples were placed on ice and delivered under chain-of-custody documentation with the groundwater samples collected from borings CPTI and CPT2 to Excelchem for chemical analysis Following groundwater sample collection, dissolved oxygen and oxidation reduction potential measurements were taken in the field and recorded on field purge logs The groundwater matrix samples from wells MW1 through MW8 and borings CPT-1 and CPT-2 _T_ v were analyzed for hexavalent chromium by EPA Method 7199, total chromium by EPA Method ' 200 7, and total hardness by EPA Method 2340C Copies of the analytical reports and chain of custody documentation are included in Appendix D ' 3.0 SUBSURFACE CONDITIONS ' 3_,_1 Geolo�y r Soil from borings MW4 through MW8 consisted mainly of silts, silty clays, and clays to depths of approximately 50 feet bgs At depths of approximately 50 to 65 feet bgs, silty sands, sands and gravels were encountered Soil from the bonngs CPT-1 consisted of alternating layers of silt and clayey silt to a depth of approximately 55 feet bgs Soil from approximately 55 feet to 60 feet consisted of layers of sandy silt and clayey silt Soil from approximately 60 feet to 105 feet consisted of silt, clayey ' silt with layers of cemented sand from approximately 70 feet to 75 feet bgs Soil from approximately 105 feet to 120 feet, the maximum depth the CPT probe explored, consisted of sand and gravelly sand followed by silt ' Soil from the boring CPT-2 consisted of silt and clayey silt to a depth of approximately 38 feet bgs Soil from approximately 38 feet consisted primarily of sandy silt and some silt to a depth of ' approximately 60 feet bgs Soil from approximately 60 feet to approximately 139 feet, the maximum depth explored, consists of alternating layers of silt and clayey silt Copies of boring logs and CPT logs are contained in Appendix B 3_2 Hydrogeology ' Water level measurements were collected from monitoring wells MW 1 through MW8 and the facility well on October 1, 2002 Water levels in groundwater monitoring wells MWI through ' MW8 ranged from 5176 to 56 42 feet below the tops of the well casing elevations representing a decrease in the water elevation of 136 feet since July 2002 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 east-northeast The average hydraulic gradient on October 1, 2002 was calculated to be 0 001 ft/ft or approximately 6 ft/mile A summary of groundwater monitoring data is presented in Table 2 ' wlwordpro1625831reports\Well_Enstall_rpt doc 5