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' 1 • 3.'0 EXCAVATION AND ASSESSMENT PROCEDURES 3.1 Vertical Extent of Contamination The first objective of the investigation was to determine the maximum depth of contaminated soil, if possible For operational reasons, excavation began at the north end of the product line trenches and worked southward A Caterpillar excavator was used to excavate the soil and stockpile it adjacent to the excavation The excavated soil, which emitted strong to very strong hydrocarbon odors during the first two days (November I6 and 17), was stockpiled north of the excavation A front-end loader worked continuously to load the stockpiled soil into dump trucks for transwrt and disposal Penocheally, Upgradient prepared a sketch of the sndewalls and screened the excavated soil for hydrocarbon vapors using a portable photo-ionization detector The PID readings were recorded on the sketches (Figure 3) PTD readings ranged between 250 parts per million (ppm) and 2,000 ppm on the north wall of the excavation throughout the morning of November 16 Because of these high readings, Upgradient directed the operator to don his respirator PID readings increased from west to east across the north wall By noon, the depth of the excavation had reached 25 feet and readings had decreased to 25-50 PPM Bid mud-afternoon, the excavator had reached its depth hrrut, and the operator ramped down to 11 feet • to allow the excavation to be deepened to 35 feet Samples collected from the excavator bucket during this time period remained in the 20-35 ppm range, and a slight odor of degraded gasoline or diesel was noticeable At 3 00 p m , Mr Harlin Knoll arrived at the site and witnessed the collection of two soil samples from the base of the excavation Sample JL-P-7 was collected from a sand layer at an approximate depth of 35 feet, sample JL-P-8 was collected from a clay layer below the sand, at an approximate depth of 38 feet A slight odor was evident in JL-P-7, none was present in JL-P-8 Based on the recommendation of Upgradient, Elite TV requested that the samples be run on 12-hour turnaround to allow excavation to continue by 8 00 on the following morning (November 17) The samples were delivered to Excelchem Environmental Laboratories in Roseville and analyzed for Total Petroleum Hydrocarbons in the gasoline and diesel ranges and BTEX The chain-of-custody form and laboratory report are contained m Appendix A As shown in Table 1, no contaminants were detected in either sample Based on these results, Upgradient requested permission to discontinue further assessment of the vertical extent of contamination and approval to begin delineation of the lateral extent of contain nation Mr Knoll approved this request at 8 30 a m on November 17 2