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OMW A Selenium Remediation Project-Final Environmental Assessment 4 CHAPTER II -ALTERNATIVJ4:S AND THE PREFERRED ALTERNATIVE Alternatives The Team evaluated the options in terms of cost and implementation ability. The following screening criteria were employed: . provides a long-term fix . is cost effective . acceptable to the public . easy to maintain with low operation and maintenance costs . consistent with wildlife area purposes and objectives; does not cause any degradation to wildlife area functions . adaptable to anticipated long-term Colorado River course changes From this screening, alternatives were dt:veloped for further study and refinement. Following further consultations with geomorphology and endangered fish experts, the following final array of alternatives were developed. Alternative 1. No Action - The No Action alternative would take no action to address high selenium concentrations in the backwater areas and selenium bio-accumulation would continue at the OMW A. Associated affects to fish and aquatic birds would also continue. Alternative 2. Pipe and Dilute - Selenium contaminated return flows from two surface drains would be diverted away from the East backwater directly into the Colorado River through buried pipelines. The water discharged directly into the river would mix and be diluted by the much larger river volume. A flushing channel would be cut to route clean river water to dilute selenium concentrations in the West backwater. Mitigation for lost habitat would involve new habitat improvements within the OMW A or at another location along the Colorado River. The estimated construction cost of the Preferred Alternative would be approximately $83,000 and annual expenditures for operation and maintenance would be about $6,000. This alternative was the ID Team and agencies' Preferred Alternative. Alternative 3. Construct New Wetlaods and Dilute - A new wetland area would be excavated near the East backwater area which would be designed to fill with "clean" water infiltrating from the Colorado River. This area would then serve as replacement habitat when beavers and their dams in the East backwater are removed to prevent ponding of irrigation drainage (and the resulting selenium bio-accumulation). The contaminated drainage would be routed directly to the Colorado River where it would be mixed and diluted in the much larger river volume. Also, a channel to route clean river water would be cut to dilute selenium concentrations in the West backwater. The estimated construction cost would be approximately $83,000 and annual expenditures for operation and maintenance would be about $6,000. "