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GEQMATRIX The estimated hydraulic gradients of horizontal groundwater flow have ranged from about 0 002 to 0 02 (Table 3) The groundwater potentiometnc surface estimated from the water level data measured in March 2003 is shown on Figure 5 Using data from the new and existing wells at the site, the horizontal groundwater gradient is estimated to be about 0 004 to the southwest The horizontal groundwater gradients and flow directions estimated from the three existing wells (Table 3) may be representative of the area in the immediate vicinity of the former USTs and not representative of the site as a whole The site groundwater flow direction will continue to be evaluated as part of the ongoing groundwater monitoring 4.3 EXTENT OF PETROLEUM HYDROCARBONS IN SOIL The logs for the soil borings advanced during this assessment are included in Appendix A Field screening results (e g , PID readings and petroleum odor) are recorded on the boring logs These results are consistent with previous site investigation results The field screening results of the soil samples collected from B3-14 indicated PID readings ranging from 122 to 309 parts per million by volume (ppmv) and strong petroleum odor between about 15 to 25 feet bgs The field screening results of the soil samples collected from the boring for MW3-6 indicated PID readings ranging from 26 to 49 ppmv and petroleum odor between about 15 and 24 5 feet bgs The PID readings of soil samples collected from the borings for MW3-4 and MW3-5 were zero to 2 ppmv, and no petroleum odor was detected PID readings of the soil samples collected during this and previous site assessments are summarized on Figures 3 and 4 Analytical data of the soil samples collected during this and previous site investigations are summanzed on Figures 6 and 7 Based on the field screening results and the soil analytical data, the estimated lateral extent of soil affected by petroleum hydrocarbons as result of the UST release is shown on Figure 2, and the estimated vertical extent of affected soil is shown on Figures 3, 4, 6, and 7 The maximum vertical extent of affected soil at the site is limited to a depth between about 13 and 35 feet bgs within the saturated zone The lateral extent of soil affected by petroleum hydrocarbons is limited to an 1 area of approximately 150 feet wide and 200 feet long within the saturated zone ' 4.4 EXTENT OF PETROLEUM HYDROCARBONS IN GROUNDWATER Analytical results of the grab groundwater sample collected at 40 feet bgs in B3-14 (Table 4 and Appendix B) indicate that TPHg,BTEX, 12DCA, and oxygenates (MtBE, ETBE, and ' TAME) were not detected, except for RIPE The reported DIPE concentration of 0 88 µg/L t I TRQJECI1 AMA6437 00016437-08 doc 10