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4 <br /> I <br /> DETAILED COST ESTIMATES <br /> ORC Oxygen Barrier Treatment Assumptions <br /> ► 6-inch well casing in 12-Inch well. <br /> ► ORC in concrete briquet carrier in fabric sock. <br /> ► Replacement of briquets either once or twice per year,as appropriate, based on seasonal BTEX <br /> fluctuations. <br /> ► Wells 4 feet on center(Note:wells 6 feet on center would reduce first year cost by$7,000). <br /> Installation Costs <br /> Subsequent <br /> First Year <br /> Years <br /> "In and Out"of Site (Driller) $4,000 <br /> Labor 12,000 <br /> Well Materials 12,000 <br /> Total $28,000 $0 <br /> Annual Operating Cost <br /> Subsequent <br /> First Year <br /> Years <br /> Labor for ORC change out, treatment $0 $3,500 <br /> well oxygen reading, miscellaneous, <br /> and contingency <br /> ORC Cost 17,OOQ 8,500 <br /> Total Annual Operating Cost 17,000 12,000 <br /> Total Cost $45,000 $12,000 - <br /> The actual ORC cost from the second year onward is projected to be$8,500.This number is a theoretical <br /> maximum for the hypothetical site.In reality,expenditure would gradually phase down from this level. For <br /> long-term treatment (e.g., 10 years),this number could decrease by 60-90th in a step-wise fashion by the <br /> tenth year.This would be a function of natural attenuation of the source/plume.Also, ORC use will <br /> eventually decrease relative to the highly conservative amounts represented.The weight ratio (6:1) of <br /> oxygen to carbon represents twice the accepted levels for mineralization to CO, and completely ignores <br /> biological incorporation into biomass. For example,some sanitation engineers are completely comfortable <br /> with a 1:1 ratio and use 2:1 as a conservative estimate. <br /> C-4 <br />