Laserfiche WebLink
<br />ORCHARD .\IES..t WILDLIFE AREA (cm'lilJuedfrmn page I) <br /> <br />Problem Setting <br />The OMWA. which extends about 1.5 miles along the south bank of the Colorado River, <br />contains several old abandoned channels of the river. These old channels are filled with water <br />which contains high concentrations of selenium that originates in Orchard Mesa irrigation <br />drainage. Beavers inhabit the area, building their dams in the old channels, and ponding this <br />drainage water. In this situation, selenium from water is more readily incorporated into <br />sediment and into plants, which are ingested by various living creatures. As the bigger <br />creatures consume many smaller ones, bioaccumulation occurs. This is how selenium <br />concentrations in fish and aquatic birds, higher up the food chain, increase to levels that impact <br />reproduction and cause deformities. There are 2 channel areas of concern -- the "Eastlt <br />backwater involves about 1 acre of water surface and the ItWest"' backwater, about 2.5 acres. <br /> <br />What are the Alternatives? , <br />1. NO ACTION -, nothing would be done about the problem I <br />and selenium bioaccumulation would continue at the OMWA. <br />Associated effects to fish and aquatic birds would also continue. <br /> <br /> <br />2. CONSTRUCT NEW WETLANDS and DILUTE - a new <br />wetland area would be excavated near the East backwater area <br />which would be designed to fill with "clean" water infiltrating <br />from the Colorado River. This area would then serve as <br />replacement habitat when beavers and their dams in the East <br />backwater are removed to prevent ponding of irrigation <br />drainage (and the resulting selenium bioaccumulation). The <br />contaminated drainage would be routed directly to the Colorado <br />River where it would be mixed and diluted in the much larger ... <br />river volume. Also, a channel to route clean river water would <br />be cut to dilute selenium concentrations in West backwater. <br />The estimated construction cost of Alternative 2 would be <br />approximately $83,000 and annual expenditures for operation & East backwater at OMWA <br />maintenance would be about $6,000. <br /> <br />3. REPLACE HABITA T OFF-SITE -- clean habitat (currently unaccessible to endangered <br />fish) would be acquired at another location along the Colorado River to replace the <br />contaminated habitat at the OMWA. This property would be developed for use by <br />endangered fish and other wildlife. The estimated acquisition and development cost would <br />be approximately $395,000 and annual operation & maintenance costs would be $6.000. This <br />off-site mitigation would not fix the selenium problem at the OMWA. <br /> <br />4. 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; <br />the remaining drainage and seep water flowing into the East backwater would be diluted by <br />pumping from the Colorado River for 6 months prior to the reproductive season of <br />endangered razorback suckers. A channel to divert Itclean" river water would be cut to dilute <br />selenium concentrations in West backwater. The estimated implementation cost would be <br />approximately $65,000 and annual operation & maintenance costs would be $13,000. <br /> <br />Don't forget to send your comments on the enclosed card by January 7. Thank you. <br /> <br />p...2 <br />