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WrerAN'Tar.c. SACRAMENTO <br /> 5.3 Excavation <br /> Excavation will entail four phases of activity centered around the area <br /> depicted in Figure 5-1. In the first phase, the upper one to two feet of top <br /> soil must be removed in order to disclose the location of underground utility <br /> lines in the area to be excavated. This will be required due to the presence <br /> of numerous utility lines, that were discovered during the site assessment <br /> and are not on the facility plans. All disrupted lines will be returned to <br /> their former condition upon completion of the remediation. A backhoe and <br /> hand digging will be employed for this phase of the excavation. <br /> The second phase will entail removing all soil from the excavation area <br /> to a depth of eight feet. This soil which is not contaminated with <br /> hydrocarbons will be reused as fill . The soil from phases one and two will <br /> be placed on a polyethylene sheet during the remainder of the excavation. A <br /> bucket-type excavator will be used for this and subsequent phases of <br /> operation. Bucket excavators typically have the capability to extend to <br /> approximately 18 feet below grade. Ramping, or the use of an extended arm <br /> excavator, will be required in order to reach the deepest contaminated soil . <br /> Phase three will involve the excavation of soil containing diesel <br /> contamination at levels greater than 100 mg/kg TPH. The excavation will be <br /> N centered on the former UST site, above the vertical plume of diesel <br /> contamination. Contaminated soil will be removed between eight to <br /> approximately 35 feet below the surface, from an area approximately 20 feet <br /> by 20 feet. Approximately 400 cubic yards of diesel contaminated soil will <br /> 1 be removed. The actual volume of the contaminated soil removed will be <br /> determined by visual examination of the excavation and by the analysis <br /> of headspace samples using an Organic Vapor Analyzer (OVA) . This <br /> determination will be confirmed by sampling the boundaries of the <br />! excavation and submitting the samples for laboratory analysis. When <br /> analysis confirms that the level of soil contamination in the excavation <br /> is less than 100 mg/kg, the excavation will be halted. The contaminated <br /> 1 <br /> 13 <br /> 1 <br />