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l <br /> Upon completion of each phase of excavation, backfilling was begun. Clean import gravel <br /> roadbase was placed into the excavation below the standing water level. The material imported <br /> contained gravel, sand and fines which allowed for proper compaction below water and the <br /> retardation of ground water flow. The requirement for the fill material to retard the flow of <br /> ground water was made by the PHSIEHD. <br /> During installation of the import gravel, Oxygen Release Compound (ORC) was added to the fill <br /> as a slurry mixture. The addition of ORC was intended to aid in the aerobic degradation of <br /> residual hydrocarbons that were not accessible to excavation. A total of 510 pounds of dry ORC <br /> ' was added to the two excavations. This amount was calculated based on anticipated contaminant <br /> levels that would remain after excavation. <br /> 3.4 Collection of Excavation Interior, Sidewall and Bottom Samples <br /> Soil samples were collected from known or suspected contaminated material to aid in the <br /> ' characterization of the type and level of contamination present. Four samples were collected <br /> from the first phase excavation and three were collected from the second. These samples were <br /> ' designated with a "Pit" prefix. Each Pit sample was collected from the excavator bucket by <br /> driving a clean brass sampling sleeve into freshly exposed soil and filling completely without <br /> headspace. The ends of the sleeve were sealed with plastic end caps, labeled with the location, <br /> date and time, and placed into a cooler chilled to 4° Celsius for transport to the analytical <br /> laboratory. <br /> Once a determination was made to cease excavation in a particular direction based upon PID <br /> headspace readings or physical or structural limitations, soil sidewall or bottom samples were <br /> collected. Soil samples were collected from sidewalls every 20 feet around the perimeter of the <br /> excavation. Sidewall samples were designated with an "SW" prefix. Bottom samples were <br /> designated with a"Bottom" prefix. Each soil sample was collected from the excavator bucket by <br /> driving a clean brass sampling sleeve into freshly exposed soil and filling completely without <br /> headspace. The ends of the sleeve were sealed with plastic end caps, labeled with the location, <br /> date and time, and placed into a cooler chilled to 4° Celsius for transport to the analytical <br /> laboratory. <br /> All soil samples were transported to GeoAnalytical Laboratories in Modesto, California. <br /> ' Samples were handled in strict accordance with chain of custody protocol. Soil sample <br /> analytical results are presented in Section 4.0 below. <br /> 3.5 Additional Soil Investigation <br /> Field observations made during the remedial excavation, in conjunction with analytical <br /> ' laboratory data obtained from the first phase of excavation, indicated that the soil boring data <br /> from previous investigations did not adequately define the level or extent of soil contamination. <br /> ' In order to attempt to further define the lateral extent of contamination, the excavator was used to <br /> 10 dig several "potholes" to the west and northwest of the remedial excavation. This work was <br /> ' American Geological Services, Inc. <br /> CA95DE-029 <br /> 8 <br />