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• <br />Alternative 3, Agriculture Beneficial Use: <br />A second alternative discussed and presented to the CDMG and the CDPHE includes the <br />use of the maintenance phase groundwater (45 gpm -includes the installation of the <br />slurry wall) extracted from the West Pit for beneficial use at the Rocky Mountain Farms <br />south of Fort Garland, CO. This alternative would require the construction of a four-inch <br />(4") delivery line from the West Pit [o the Rocky Mountain Farms and the construction of <br />a series of lined holding ponds at the Rocky Mountain Farms to stage West Pit water <br />during the winter (non-irrigation portion of the year). Groundwater from the West Pit <br />would be blended with other irrigation water at an acceptable ratio to meet appropriate <br />water quality standazds for irrigation. Costs associated with this alternative would <br />include initial capital construction costs for the pipeline and the holding ponds. Water <br />delivery to [he farms would be by gravity flow; therefore no pumping equipment would <br />he necessary for delivery of the water [o [he farms. O&M replacement costs would be <br />required for the augmentation system for pump replacement. The useful life for the <br />intermittent use of the augmentation pump would be 15 years at an approximate cost of <br />$20,000. Therefore, an annual O&M accrual cost for the pump replacement would be <br />$1,333/year. The estimated useful life of the pipeline and ponds is expected to be beyond <br />the life of the project. Although, an annual accrual cost of $5,000/year is included for <br />possible periodic repairs. Annual monitoring costs to evaluate salt development and <br />migration associated with soils and vegetation would be conducted. Annual monitoring <br />costs are estimated to be $5,000 per year. <br />Estimated Capital Costs for ponds and pipeline = $2,090,000 <br />Estimated monthly operating costs: <br />Augmentation electrical costs for 45 gpm as given in Alternative 1 = $900 <br />Labor <br />(1 man day/week to augment water system) ($30/hr)(8 hrs/day)(52 weeks) _$ I'_',480 <br />Amtual O&M and replacement costs = $1,333 + $5,000 = $6,333 <br />Annual soils and vegetation monitoring = $5,000 <br />Alternative 3, Total Annual Costs = $34,614 <br />Alternative 4, In-situ Passive Treatment: <br />The third alternative involves the preferred alternative as presented in TR-26, which <br />allows for the treatment of the constituent source within the West Pit. As presented and <br />discussed in TR-26, bench-scale testing of passive organic amendment addition to the <br />West Pit water demonstrated the ability to reduce constituent concentrations in West Pit <br />groundwater. To further evaluate this alternative, BMRI proposed to conduct field <br />studies of the proposed treatment method and follow-up pilot-scale testing executing the <br />