1999-11-05_REVISION - M1988112 - Laserfiche WebLink

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Slurry Wall Installation: A cost proposal for the installation of a slurry wall has been received from INQUIP Associates, Inc. This cost proposal identifies estimated costs associated with installing approximately a 1,000 foot long and 40 foot high and 3 foot thick slurry wall along the eastern and southern perimeters of the West Pit. Estimated slurry wall installation costs include: Slurry wall installation costs Slurry-till material supply $226,000 30,000 (Extraneous from the cost proposal) 3,000 yd' @ $ ] 0/yd3 Total Slurry Wall Installation Cost Estimate $256,000 Alternative 1, Reduction Phase Active Water Treatment Cost Estimate: Estimated volume of water required to be extracted to reverse the hydrologic groundwater gradients from the Rito Seco Creek to the West Pit at 400 gallons per minute (gpm). 70 days (400 gpm) (1440 minutes/day) = 40,320,000 gallons An active treatment cost proposal received from Environmental Reclamation lnc. during July 1999 identified an estimated cost of $9.43/1,000 gallons treated. This cost estimate includes all labor, operating materials and equipment, and equipment replacement costs associated with the active treatment system. Estimated reduction phase active water treatment system costs: 40,320,000 gallons / 1,000 gallons x ($9.43/1,000 gallons treated) _ $380,218 Alternative 2, Annual Maintenance Phase Water Treatment and Enhanced Evaporation Cost Estimate: Annual management of the West Pit groundwater would be conducted using two operating technologies through the course of the calendar year..During the annual period it is anticipated that the active water treatment system would be operated 7 months of the year (winter months) at approximately 40 to 50 gpm with the installation of the slurry wall. For purposes of the estimate an average Flow rate of 45 gpm was used. Estimated groundwater volume to be treated during 7-month (212 day) period (212 days) (45 gpm) (1440 minutes/day) = 13.737,600 gallons