ARCHIVED REPORTS XR0000007 - Laserfiche WebLink

Home Browse Search

IcV0 A S S O C I A T E S I N C 4.0 SUBSURFACE CONDITIONS 4_I Geology Soil in borings MW1, MW3, MW4, and MW5 consisted of poorly graded sand with silt from the surface to 6 5 to 10 feet bgs Soil from depths between 6 5 to 10 feet bgs and 31 to 35 feet bgs consisted of well graded sand and poorly graded sand Soil from depths between 31 and 35 feet bgs to approximately 36 5 feet bgs, the maximum depth explored, consisted of lean clay and/or elastic silt with sand Soil in boring MW2 consisted of poor to well graded sand with varying amounts of silt from the surface to 35 feet bgs Soil from depths between 35 feet bgs and 38 feet bgs consisted of elastic silt Soil from depths between 38 feet bgs and 39 feet bgs consisted of silt with gravel Soils from depths between 39 feet bgs and 40 feet bgs consisted if silt Soil from depths between 40 feet bgs and 45 feet bgs, the maximum depth explored, consisted of silt with sand 442 Hydrogeol_ogy Water level measurements were collected from wells MW1 through MW5 on December 10, 1999 Water levels ranged from 20 89 to 21 81 feet below the tops of the well casing elevations, representing an average decrease in the water table elevation of approximately 0 24 feet since September 1999 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 southwest The average hydraulic gradient on December 10, 1999 was calculated to be 0 0004 ft/ft or approximately 2 ft/mile In addition, water level measurements were collected from wells MW 1 through MW5 on ' October 27, 1999 Assuming that horizontal isotropic conditions prevail, groundwater in the uppermost aquifer beneath the site flowed towards the southwest A summary of groundwater monitoring data is presented in Table 1 1 50 ANALYTICAL RESULTS The groundwater sample collected from well MW2 on October 27, 1999 contained detectable concentrations of TPHg, TPHd, toluene, ethyl benzene, and xylenes The groundwater sample collected from well MW2 on October 28, 1999, after the 24-hour pump test was completed, also contained detectable concentrations of TPHg, TPHd, toluene, ethyl benzene, and xylenes The concentrations of TPHg, toluene, ethyl benzene, and xylenes had decreased to the sample collected on October 28, 1999, but the concentration of TPHd had increased in the sample collected on October 28, 1999 Analytical results of groundwater samples are summarized in Table 2 W%130991reportslsumwe11 doc 6