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' Pombo Ranch Facility May 2006 Site Closure Report appears to be confined to semi-confined beneath the overlying silty clay in borings 133/9, B10, and B11. The shallow sandy unit is not present in borings to the east and south of ' the former underground storage tank. A coarse sand to pebble gravel was encountered at 5 feet in boring B 12. The sand unit is underlain by wide spread clay layer in the western ' portions of the site. Hydrogeologic cross sections are shown in figures 8 and 9. �, � k4 vv,cb�_ Unconfined groundwater was ranged from 9.3 to 13.3 feet below grade during groundwater monitoring�om August 1999 to April 2006. Groundwater elevations have — ranged_fftr 31.7 tofeet above sea level between August 1999 and April 2006. �< s" ),1 Groundwater flow has been consistently to the northeast with a very shallow gradient. Groundwater elevations in the well pair MW5 (shallow) 1 MW105 (deep discretely screened) have been similar, indicating a lack of vertical groundwater movement. ' 2.0 REMEDIAL EXCAVATION ' On February 8, 2005 M.J. Kloberdanz & Associates collected soil samples in the area proposed for excavation to pre-qualify the soil to be excavated for disposal at Forward Landfill. Four soil samples were collected at varying depths to provide an estimated ' average concentration of the petroleum contamination present in the soil near the original release at the Pombo Facility as shown in Figure 3. A backhoe was provided by Pombo Ranch to facilitate sample collection. Gasoline, gasoline constituents and diesel were present in low to moderate levels in some of the samples. Lead concentration was consistent with normal background levels in the area. ' Table of Analytical Results (02108105 Sample Gasoline TEPH Benzene Toluene E-Benzene Xylenes Lead I.D. mg/Kg _M&/Kg p /K IK K mg/Kg t PQ-1-5' <1.0 <1.0 <5.0 <5.0 <5.0 <5.0 5.7 PQ-3-8' <1.0 <1.0 <5.0 <5.0 <5.0 8.1 6.0 P -3-5' 302 652 247 2320 1470 4030 7.8 PQ-3-8' 1 2.7 1 37 <5.0 10 24 134 5.9 On February 28, 2005 M.J. Kloberdanz & Associate started the excavation of the source ' area of contamination closest to the former underground gasoline tank. A Photo Ionization Detector was used to screen contaminated soils from clean soils and to assist in worker health and safety. The impacted soils exhibited a dark gray discoloration and ' gasoline odor, which was confirmed with the Photo Ionization Detector. Soils near the original release were impacted below a depth at about 5 feet below grade. Away from the point of release, the depth to impacted soils increased to an average of 8 feet below surface grade. Soils above 8 feet in depth were then segregated into a "clean pile" for reuse as fill Int the excavation. ' Groundwater was measured at a depth of about 12 feet from the surface in the January 2005 quarterly monitoring event. Depth to water was estimated at least 12 feet from ' 6