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<br />Orchard Mesa Selenium Remediation Environment Assessment <br /> <br />5 <br /> <br />The estimated acquisition and development cost would be approximately $395,000 and annual <br />operation & maintenance costs would be $6,000. This off-site mitigation would not fix the <br />selenium problem at the OMW A. <br /> <br />Alternative 5. Divert and Dilute - contaminated water from a major irrigation drain would be <br />conveyed via an open channel directly to the Colorado River bypassing the East backwater; the <br />remaining drainage and seep water flowing into the East backwater would be diluted by pumping <br />from the Colorado River for 6 months prior to the reproductive season of endangered razorback <br />suckers. A channel would be cut to divert "clean" river water to dilute selenium concentrations in <br />the West backwater. The estimated implementation cost would be approximately $65,000 and <br />annual operation & maintenance costs would be $13,000. <br /> <br />Each of these alternatives were evaluated using an estimated lO-year life to correspond to the <br />estimated life of the East and West backwater channels. These channels, which prior to large <br />floods in the early 1980's were the mainstem of the Colorado River, are now rapidly filling with <br />sediment and will eventually change from depressions retaining water year round to bottomlands <br />that flood only during runoff. <br /> <br />Evaluation of Alternatives <br /> <br />The alternatives were evaluated and compared. Some ofthe conclusions were: <br />- Alternative 2 appeared to be the best fit for Recovery Program needs <br />Alternative 3 was discouraged by the Recovery Program <br />Alternative 4 doesn't satisfY the needs statement <br />Alternatives 2 & 3 had the lowest estimated annual cost (for an anticipated 10 year life) <br />Alternative 5 would involve more traffic which would disrupt wildlife and have more <br />extensive operation and maintenance needs. <br />It is important to adopt a plan that minimizes environmental impacts. <br /> <br />. Preferred Alternative <br /> <br />Because it appears to be the best fit for the Recovery Program needs and favorably compared to <br />other alternatives for lowest estimated annual cost, Alternative 2 was chosen as the Preferred <br />Alternative (See Figure I). <br /> <br />Environmental Commitments <br /> <br />The following environmental commitments would be included as part of any alternative selected. <br />Environmental commitments are designed to reduce impacts to natural and other resources and <br />would be completed concurrently with other project features. <br /> <br />1. All permits and contracts would have a "stop work" clause in the event that cultural or <br />paleontological resources are found during construction. <br />