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,VIA A S S O C I A T E S I N C be to be dissected by intermittent sloughs which have since been filled as a result of land leveling The annual precipitation is about 14 inches(USDA, 1992) ' The soil borings advanced at the site to date, indicate the soil column consists of interbedded sand, silt, clay, and to a lesser degree, gravel to a depth of approximately 91 5 feet bgs, the ' maximum depth explored during this investigation Noteworthy observations include an apparent discontinuous gravel bed observed at approximately 20 feet bgs in borings SBI, MW 1, MW2, and MW3 Also, a clay interval was observed at a depth of approximately 35 feet bgs in borings SBI, SB2, MW1, and MW2 Soil samples indicate ' the thickness of each of these units is generally less than five feet Although sand was logged periodically in the upper 60 feet of the soil column, no sand units were observed beyond 65 feet bgs Soils beyond 60 feet bgs generally consisted of silt and clay variations ' Soil lithology is depicted on the Geological Cross Section (Figures 5 and 6) 2.2 Hydrogeology Water level measurements were collected from wells MW 1 through MW3 on a quarterly basis from June 1999 to March 2000 The water levels were measured between 75 89 to 80 14 feet ' from the top of the well casings A summary of groundwater monitoring data is presented in Table 2 Water level measurement data indicates the water table is highest during spring (first quarter) and lowest during early winter (forth quarter) The water table has fluctuated as much as 3 91 feet in a single monitoring well based on water level measurements collected during the quarterly monitoring program 3.0 DISTIBUTION OF PETROLUEM HYDROCARBONS 3_1 Petroleum Hydrocarbons in Soil ' A total of 28 soil samples collected from borings SBI, SB2, and MW 1 through MW3 were submitted to the laboratory for chemical analysis The selected samples were collected at various rdepths ranging from 15 5 feet to 90 5 feet bgs The highest reported constituent concentrations were observed in soil samples collected at 25 5 r feet bgs in each of the borings The highest concentrations of petroleum constituents at this depth were observed in SB 1 and SB2 located in the immediate vicinity of the former USTs Laboratory results collected from SB 1 and SB2 include TPHg (9,500 mg/kg), toluene (65 mg/kg), ethyl benzene (82 mg/kg), and xylenes (470 mg/kg) The petroleum hydrocarbons appear to attenuate rapidly with depth as indicated greatest by soil samples from SB1 at 45 5 feet bgs and SB2 at 55 5 w 1148851repoFU\NFA-Rcqucst,doc 3 r