ARCHIVED REPORTS_FEASIBILITY STUDY AND CORRECTIVE ACTION PLAN

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Standard earth moving equipment (backhoes, bobcats, loaders, etc.) is typically utilized for soil excavation. Depending on available space, this range of equipment can excavate to a depth of approximately 20 fbg. Larger earth moving equipment (excavators) can excavate slightly deeper. Typically, large diameter augers are used for very deep excavations. Entry into excavations deeper than 5 fbg requires sidewall shoring per Occupational Safety and Health Administration regulations. Deep excavations may require shoring to prevent collapse of the sidewalls, and to prevent damage or undermining of neighboring structures, utilities, sidewalks, etc. Additionally, dewatering of the excavated area may be required depending on the groundwater elevation and recharge rates. The extent of excavation is typically estimated in advance using available soil boring data,but is ultimately directed by field personnel using field monitoring equipment such as a photo-ionization detector to screen soils by measurement of soil headspace vapor concentrations. Soil samples are collected for chemical analysis to confirm that the excavation limits are sufficient to meet soil cleanup levels. 5.3.3.2 FEASIBILITY AND COST-EFFECTIVENESS Excavation would be the most effective method for removing hydrocarbon mass in shallow soil. Dissolved-phased hydrocarbons would attenuate more rapidly once the bulk of the source material is removed. The addition of an amendment to the fill material may also enhance the attenuation rate. Currently, the existing facilities (ASTs, loading rack, piping, etc.) limit the excavation extents and would result in incomplete mass removal. However, excavation could be conducted in the future, concurrent with any site improvement work. Assuming future site improvements allow for focused excavation in the three source areas,CRA conceptualized the following excavation limits: • SA-1: 60-feet wide by 60-feet long by 15-feet deep excavation encompassing MW-10, MW-39, and AS-1 through AS-5. These limits equate to 2,000 cubic yards or 3,000 tons of soil. • SA-2: 40-feet wide by 140-feet long by 10-feet deep excavation encompassing AS-8, MW-1, AS-9, AS-11, and MW-24. These limits equate to 2,100 cubic yards or 3,100 tons of soil. • SA-3: 40-feet wide by 40-feet long by 10-feet deep excavation encompassing MW-13R and SB-24. These limits equate to 590 cubic yards or 890 tons of soil. 247729(33) 20 CONESTOGA-ROVERS&ASSOCIATES