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<br /> Monitoring Costs $1,734,000 implemented for 30 years. The estimated costs
<br /> Capital Costs 0 for the 30-year period are:
<br /> Total Operations and Maintenance 0
<br /> (O&M) Costs Monitoring Costs $1,734,000
<br /> Present Worth Cost for 30 years Capital Costs $3,324,000
<br /> $1,734,000 Total O&M Costs $285,000
<br /> 5-year Performance Evaluation
<br /> "Present-worth cost"is the amount of money $70,000
<br /> that,if invested now,would cover all the estimated (performed at end of years 5, 10,
<br /> costs of the proposed alternative. 15, 20, 25, and 30)
<br /> Present Worth Costs for 30 years
<br /> Alternative 2,termed"Institutional Controls," $9,513,000
<br /> consists of no physical cleanup but prohibits the
<br /> drilling of off-base shallow wells downgradient of Alternative 4 is groundwater extraction at
<br /> DDRW-Tracy in the area presently affected by the 1000 gpm with treatment by air stripping and
<br /> contaminant plume or potentially affected in the vapor-phase carbon with in situ biological treat-
<br /> future,imposes deed restrictions on future residen- ment and injection into the aquifer. This is a novel
<br /> tial development adjacent to the site downgradient, approach to treat the extracted groundwater by air
<br /> requires a signed Interagency Management Agree- stripping,as in Alternative 3,then adding nutrients
<br /> ment to control future groundwater use at the site, to a small portion of the treated water as it is
<br /> and requires DDRW-Tracy to provide bottled wa- injected into the underground aquifer. These nutri-
<br /> ter to two families. As with Alternative 1, the ents will cause TCE, PCE, and other organic
<br /> groundwater plume would be monitored using 30 contaminants that are underground to break down
<br /> wells. This alternative would also be implemented into nontoxic compounds.
<br /> for 30 years. The estimated costs are shown below:
<br /> Alternative 4 uses the same number of extrac-
<br /> Monitoring Costs $1,734,000 tion wells and air strippers as Alternative 3. An
<br /> Bottled Water Costs $14,000 additional four wells to inject the nutrient-rich
<br /> Capital Costs 0 treated water have been added to make a total of
<br /> Total O&M Costs 0 about 38 injection wells. Pilot testing would be
<br /> Present Worth Cost for 30 years needed to demonstrate the effectiveness of this
<br /> $1,748,000 alternative. A similar cleanup strategy has been
<br /> accepted at another Superfund site. This alterna-
<br /> Alternative 3(preferred)is groundwater ex- five would include monitoring of the groundwater
<br /> traction at 1000gpmwith treatment by air stripping and would be implemented for 30 years. The
<br /> and vapor-phase carbon and injection into the estimated costs for the 30-year period are:
<br /> aquifer, and is designed to capture and remediate
<br /> the entire OU#1 on-base and off-base contaminant Pilot Tests Cost $200,000
<br /> plume. This alternative would use the current IRM Monitoring Costs $1,734,000
<br /> air stripping system plus one additional similar air Capital Costs $3,869,000
<br /> stripping system to handle up to 1000 gpm of Total O&M Costs $366,000
<br /> extracted groundwater. Groundwater would be 5-year Performance Evaluation
<br /> extracted using about 41 extraction wells, treated $84,000
<br /> by the two air strippers, and injected back into the (performed at end of years 5, 10,
<br /> upper and middle horizons of the aquifer using 15, 20, 25, and 30)
<br /> about 34 injection wells. This alternative includes Present Worth Cost for 30 years
<br /> monitoring of the groundwater and would be $11,313,000
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