2000-02-24_REVISION - M1988112 - Laserfiche WebLink

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FINANCIAL WARRANTY REQUII2EMENT RE-EVALUATION SAN LUIS PROJECT M-88-112 February 24, 2000 TASKS AND COST ESTIMATES FOR REMAINING RECLAMATION OBLIGATIONS: WEST PIT WATER MANAGEMENT PROGRAM ASSUMPTIONS In order to clean up the Wes[ pit backf711, the operator needs to withdraw, and pro;,ess, 4.91 pore volumes of water from the lower pit area and 5.24 pore volumes of water from the pink gneiss area. 1 pore volume equals 106,831,591 gallons in [he lower pit and 1 1,408,470 gallons in the pink gneiss. 4.91 pore volumes in the lower pit equal 524,543,1 -2 gallons. 5.24 pore volumes in the pink gneiss equal 59,780,383 gallons. Total for both areas is 584,323,495 gallons. 2 processes and l alternative have been evaluated since they are the only approved operations. A) Nano-filtration process -Cost equals $6.90/1000 gallons treated. 12 month operation. B) Evaporation system - $10,810.00/month (backup system). The West pit water level will be pumped down to a msl of 8580 feet (for the lower pit. The pink gneiss water level should equalize at approximately 8604 feet msl) at 400 - 700 gpm. Thereafter, the aquifer will be pumped at the steady state rate which is estimated at l 10 gpm I>lus 70 gpm which BMRI anticipates pumping from the alluvial aquifer and re-injecting into [lie lower pi[ area. So, the total pump rate from the West pit is anticipated to be 180 gpm. It will take approximately 7.0 years to pump and treat the above noted pore volumes of water. WATER MANAGEMENT TREATMENT AND ESTIMATED COSTS 584,323,495 gallons x $6.90/1000 gallons = $4,031,832 Monitor 8 wells at 1 sample/month at $100.00/sample = $9,600/year $9,600/year times 7.0 years = $67,200 CDPS discharge monitoring - 12 months times 4 samples/month times $200.00/sample = $9,600/yeaz $9,600/year times 7.0 yeazs = $67,200 Yearly water loss from the West pit ponds and sludge production is approximatel}' 6 acre -feet.