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Pombo Ranch Facility May 2006 Site Closure Report 1 ; 40 ground surface in the area of the former UST on February 28th limiting the vertical extent of the excavation to 12 feet below grade surface. Apparent contamination extended in a north to northeast direction establishing and the ' lateral limits of the excavation resulted in an irregular shape 65' to the east of the existing above ground tanks and 50 to 62 feet north of the east lateral line (see Figure 4). Monitoring well MW-4, located within the excavation, was destroyed during the ' excavation. The well was replaced on May 4, 2005. Confirmation samples were collected from each of the four sidewalls of the excavation at 1 about ten feet in depth. Gasoline hydrocarbons were,not detected in the samples above reporting limits. Kerosene range hydrocarbons were present in very low levels in two of the samples. Volatile aromatic hydrocarbons were detected in low concentrations on the ' west wall and in moderate concentrations on the east wall. None of the Oxygenated Compounds, including MTBE, were present in the confirmation samples. Lead levels were similar to the pre-qualification sample levels. Confirmation laboratory sample ' results are shown in Appendix B. Table of Anal tical Results (03101105) ' Sample Gasoline TEPH Benzene Toluene E-Benzene Xylenes Oxys Lead I.D. mg/Kg mg/Kg IK K IK K IK m IK CW-1-10' <1.0 29 <5.0 <5.0 19 19 ND 5.6 CS-2-10' <1.0 <1.0 <5.0 <5.0 <5.0 <5.0 ND 5.6 CN-3-10' <1.0 <1.0 <5.0 <5.0 <5.0 <5.0 ND 5.0 CE-4-10' <1.0 37 <500 <500 670 1290 ND 5.5 ND=Non Detect ' 1,524.71 tons of excavated soils were removed from the site and transported to Forward Landfill for disposal. Disposal Activity Reports, shown in Appendix C, list Class lI soil ' and Environmental I, which is a surcharge in addition to the Class II soil disposal charges. ' Due to seasonally late rain the soil had to be transported over a number of weeks. Since the soil was damp and "sticky", and had a tendency to stay in the trailer, vegetable oil ' was used to lubricate the 33 foot long end dump trailer between each load. The excavation was backfilled with clean soils segregated from the excavation and soil provided by Pombo from an onsite source. The surface was graded and the base rock or troad base replaced. Contamination was apparent at depths of 5 to 8 feet to groundwater and below. The excavation was limited to the soil above the depth to groundwater on February 28th and ' March 1" 2005. Petroleum contaminated soil approximately 12 feet in depth with a lateral area of 3640 square feet was excavated from the Pombo Ranch Facility. An area of ' approximately 3500 square feet was estimated from the site map and used in the mass balance estimates. Direct comparisons between the volume of in place soil estimated from the maps and cross sections and the volumes reported at the disposal site are 7 I