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U-Haul#704-50 Blaes Environmental IAdditional Site Characterization S 21 2 Lateral Extent Figures 7 and 8 illustrate the source area and the lateral extent of hydrocarbons in soil Figure 8 illustrates the cross-section A- A' and the corresponding hydrocarbon concentrations with depth According to these two figures, borehole DP-6 defines the western lateral extent of hydrocarbons in soil with detectable Iconcentrations near detection limits and non-detectable results at depths of 60, 90, and 120 feet bgs Borehole DP-3 defines the northern lateral extent of hydrocarbons in soil with detectable concentrations of TPHg less than or equal to 10 mg/Kg and detectable benzene concentrations less than 0 72 mg/Kg (Figure 8) Soil from this borehole did not contain detectable concentrations of hydrocarbons at depths of 70, 100, and 110 feet bgs The southeastern extent of hydrocarbons apparently extends off site The limits of impacted soil to the southeast of the source area was inferred using the distance between DP-6 and the source area Southeast of the source area, analytical results of soil from DP-4 and MW-4a defined the degree of impacted soil near the eastern property boundary 5 2 13 Vertical Extent The vertical extent of hydrocarbons in soil is defined with analytical results of soil samples from boreholes DP-2, DP-3,DP4 and DP-6 The soil sample from DP-2 at 120 feet bgs consisted of sandy clay and did not contain detectable concentrations of hydrocarbons This was the deepest sample collected from DP-2 Soil samples collected from DP-3 at approximately 100 and 110 feet bgs consisted of silty sand and sand Both of these samples from DP-3 did not contain detectable concentrations of hydrocarbons (Table 4) Soil samples collected from DP-4 indicate detectable hydrocarbons at depths of approximately 110, 120, and 125 feet bgs However, detections in the sample from 110 feet bgs, which consisted of sand, were less than 0 016 mg/Kg Also, detections in the sample from 125 feet bgs, which consisted of sandy clay, were less than 0 020 mg/Kg (Table 4) These detectable results are very near the detection limit of 0 005 mg/Kg for BTEX The more elevated concentrations exhibited in the soil sample collected at 120 feet bgs may be result of cross contamination Despite this inconsistency, Blaes Environmental believes that these samples adequately define the vertical extent of hydrocarbons at DP-4 1 Analysis of soil samples collected from DP-6 indicate non-detectable concentrations of hydrocarbons at 120 ' feet bgs and detectable concentrations of hydrocarbons at depths of approximately 110 and 125 feet bgs However, detections in the sample from 110 feet bgs, which consisted of sand, were less than 0 024 mg/Kg Again, these detectable results are very near the detection limit of 0 005 mg/Kg for BTEX Also, detections ' in the sample from 125 feet bgs, which consisted of silty sand, were less than 0 37 mg/Kg (Table 4) The elevated concentrations exhibited in this soil sample may be representative, however, the low level 22