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U-Haul#709-50 Rlaes Enwronmental Additional Site Charactenzation detections in soil at• similar depths support evidence that the vertical extent of the hydrocarbon plume is Y within 10 feet of the total depth of the boreholes Based on the data collected from direct-push and cone- penetrometer soil sampling, the vertical extent of hydrocarbons in soil is approximately 125 to 135 feet bgs 5 2 2 HydMccarbons in Ciroundwater The installation of the new monitoring wells provided data to re-establish a more representative understanding of groundwater conditions beneath the site Groundwater level measurements indicated that the depth to groundwater ranged between 44 83 and 46 43 feet below top-of-casing Calculating the elevation of groundwater, the groundwater surface was mapped (Figure 9) The interpretation of the resulting groundwater elevation surface indicates that the groundwater flow direction was toward the north on the northern portion of the site and toward the south on the southern portion of the site (Figure 9) A variable groundwater flow direction is common with a generally flat groundwater gradient tComparing the groundwater level measurements from the new wells with the level measurements from the r pre-existing well,which are screened at approximately 15 to 30 feet below the groundwater surface, suggests Ithat the saturated soil beneath the site is not confined Groundwater level measurements from both well types indicate comparable groundwater level measurements Characterization of the extent of dissolved-phased hydrocarbons at the site involved evaluation of the analytical results of groundwater samples from the new monitoring wells and analysis of the hydro-punch groundwater sample Conclusions of groundwater characterization include the following I Analytical results of groundwater samples indicated that the source area of dissolved-phase ! hydrocarbons is probably near monitoring well MW-3a Groundwater from MW-3a contained 160,000 gg/L TPHg and 18,000 4g/L benzene (Table 6) Analytical results of groundwater from MW-4b, the nearest sample point to MW-3a, further defined the center portion of the hydrocarbon plume Groundwater from MW-4b contained 34,000 µg/L TPHg and 3,000 gg/L benzene (Table 6) I The results of samples collected from monitoring wells MW-5 an BP- P $ d 1 were used to define the lateral extent of dissolved-phase hydrocarbons Despite detections of toluene (0 5 pg/L) and total xylenes (1 1 gg/L), groundwater from MW-5a did not contain detectable concentrations of TPHg or benzene (Table 6) This sample point is used to define the probable northern extent of impacted groundwater The hydro-punch groundwater sample (HP-1) collected approximately 85 feet south of the source area 23