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(J1)\hOll OMW A Selenium Remediation Project-Final Environmental Assessment 5 Alternative 4. Replace Habitat Offsite - clean habitat (currently inaccessible to endangered fish) would be acquired at another location along the Colorado River to replace the contaminated habitat at the OMW A. This property would be developed for use by endangered fish and other wildlife. The estimated acquisition and development cost would be approximately $395,000 and annual operation and maintenance costs would be $6,000. This off-site mitigation would not fix the selenium problem at the OMW A. Alternative 5. Divert and Dilute - contaminated water from a major irrigation drain would be conveyed via an open channel directly to the Colorado River bypassing the East backwater; the remaining drainage and seep water flowing into the East backwater would be diluted by pumping from the Colorado River for 6 months prior to the reproductive season of endangered razorback suckers. A channel would be cut to divert "clean" river water to dilute selenium concentrations in the West backwater. The estimated implementation cost would be approximately $65,000 and annual operation and maintenance COSIS would be $13,000. Evaluation of Alternatives Each of these alternatives were evaluated using an estimated lO-year life to correspond to the estimated life of the East and West backwater channels. These channels, which prior to large floods in the early 1980's were the mainstem of the Colorado River, are now rapidly filling with sediment and will eventually change from depressions retaining water to year-round bottomJands that flood only during runoff, The alternatives were evaluated and compared. Some of the conclusions were: Alternative 2 appeared to be the best fit for Recovery Program needs Alternative 3 was discouraged by the Recovery Program Alternative 4 doesn't satisfy the needs state men I Alternatives 2 & 3 had the lowest estimated annual cost (for an anticipated 10 year life) Alternative 5 would involve more traffic which would disrupt wildlife and have more extensive operation and maintenance needs It is important to adopt a plan that minimizes environmental impacts Preferred Alternative Because it appeared to be the best fit for the Recovery Program needs and favorably compared to other alternatives for lowesl estimated annual cost, Alternative 2 was chosen as the Preferred Alternative (See Figure l). On-site meetings with representatives of the Recovery Program, Army Corps of Engineers, Service, Mesa Land Trust (operators of the wildlife area) and Reclamation were held on July 12 and August 17,2000 to discuss exact locations of the improvements and other "specifics" of the plan.