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MAY-20-1999 17:11 DWR DIVISION 3 719 589 6685 P.02 <br />• • <br />Preliminary review: Battle Mountain Gold (BMG) proposal to use mine pit <br />dewateting effluent for agricultural use on Rocky Mountain Farms (RMF). <br />Synopsis: <br />BMG has verbally proposed pumping water to a pit on the minesite, then running the <br />water to pits at Rocky Mountain Farm (RMF). At RMF the water will be diluted into one <br />of the center pivot sprinklers and the water used for irrigation of crops. The initial plan <br />called for 100 gpm of water, extracted from the mine site, be transported via pipeline to <br />the RMF to a pit. The RMF pit would be sized to hold water extracted doting the non- <br />irrigation season in addition to summer pumping. <br />Issues: <br />I . The memo notes that the RMF pits aze designed to hold 102.9 acre-feet which is <br />sufficient to hold 9 months of 100 gpm pumping. The 102.9 AF is only sufcient to <br />hold 7.7 months of 100gpm pumping. This tray effect the feed flows to the sprinkler <br />required to dewater the RMF pit for winter. <br />2. The RMF pit requires a minimum discharge of 250 gpm into the sprittkler to 'empty' <br />the RMF pit for the next winter. This would make the effluent dilution 4:1 not 10:1, <br />as initially discussed, if it is run to one sprinkler. <br />3. Retum water from the farm would be run up the same pipeline and dumpedi to Rito <br />Seco. The proposal implies that this return water would be batched to the cheek. <br />Batching will severely impact the water users on Rito Seco. Clean water would need <br />to be released to Rito Seco, at the same time and amount as the depletions to Rito <br />Seco occur, to prevent injury to water user. Ibis issue has not been addressed. <br />4. Depletions to Rito Seco will occur in the winter potentially injuring downstream <br />senior water rights (Eastdale, Sanchez, etc). No mechanism is proposed to replace <br />winter depletions in the same time and amount to Rito Seco. <br />5. The data used to size the 100 gpm extraction rate is suspect. Pumping tests in the pit <br />last winter yielded 95 gpm with little discernable drawdown (TR-26 appendix A5.0 <br />pg. A-9). During minting Rito Seco inflows were noted at 125 to 200 gpm artesian <br />flow. The plan calls for dewatering the pit to reverse the hydraulic gradient causing <br />Rito Seco to flow into the pit area. Given the transmissivity of the Rito Seco alluvium <br />and the backfill material what mechanism will keep the inflow from Rito Seco to 30 <br />or 40 gpm? Will the flow from Rito Seco vary with the season? <br />6. Is there a backup plan if the volume pumped from the pit (steady state) is greater than <br />assumed in the proposal? <br />7. Does moving the problem out of the mine permit azea cause Water Quality Control <br />Commission to be involved? <br />BMG proposal preliminary review <br />05/20/99 <br />DNR/DWRJDIV3 <br />1 of 2 <br />