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Show CEA Report Environmental - Ecology Old High 088Srt jWstBf 2; S* m3Sess&__ Blwr SpoBod sandplpor Figure 8 Riparian vegetation zones and associated nesting birds. Riparian vegetation provides important habitat for wildlife ( BOR 1996 EIS). Perceived Benefits of Glen Canyon Dam The cold, clear, regulated flows from the dam create habitat for some species. For the most part, the benefiting species are non- native, and compete with or prey upon native species. The assemblage of native aquatic and terrestrial organisms is necessary for a sustainable, functioning ecosystem. • Cold, clear waters released by Glen Canyon Dam allow algae to thrive, thus altering the riparian food chain to support non- native species. • Control of natural spring flooding has stabilized riparian environment allowing non- native plants such as tamarisk to take hold and expand habitat. 6' 10 • Prior to construction of the dam, 180 species of birds were known to exist in Grand Canyon. In 1987, 303 different species were sighted. 6 • As a result of the 1996 Glen Canyon Dam EIS, the Adaptive Management Work Group and the Grand Canyon Monitoring and Research Center have been established to enact polices which attempt to mitigate impacts of Glen Canyon Dam on the Grand Canyon. Health Issues V EVERAL NATURAL and introduced sources of pollution have ^-^ contaminated the waters of Powell reservoir. These include radioactivity and heavy metals from abandoned uranium mining operations, petroleum pollution from recreational watercraft, and bacteria from human use of the reservoir. • Naturally occurring selenium and mercury from upstream sources are trapped in the sediments in Powell reservoir rather than flowing harmlessly to the sea, as they did prior to the construction of Glen Canyon Dam. 2,15 • Changes in the reservoir are leading to anaerobic conditions near the sediment layer. This results in changes to the chemistry of heavy metals, causing them to migrate up into the water column and into the food chain. • The flooding of Glen Canyon near Hite, Utah covered piles of toxic uranium mill tailings. • Water percolating through tailings also becomes contaminated with radioactivity from Thorium- 230, Radium- 226 and Radon- 222 left behind in the milling process. 14 Uranium mill tailings contain high concentrations of heavy metals including arsenic, barium, cadmium, lead, selenium and vanadium. These metals pose a significant health risk. n> 12 Water percolating through these sediments extract the toxic heavy metals, which become incorporated into fish flesh. 13 Flushing of sediments will cause the release of heavy metals downstream. Therefore, water and sediment quality should be monitored during draining. 2 Draining the reservoir will expose tailings piles, which will need to be capped or removed. Recreational use of the reservoir has added lead and other toxic pollutants to the water and underlying sediment. Introduction of human waste into the reservoir increases bacteria levels, thereby requiring occasional closure of some swimming areas. page 11 |