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• Using standard reclamation techniques and methods, suitable vegetation communities have been <br />established on reclaimed lands at other mines in the western United States that have climatic <br />regimes and weather patterns similar to the proposed Red Rock Mine. Permanent vegetation <br />capable of supporting the post-mining land uses of rangeland has been established successfully <br />without the use of irrigation in a vaziety of arid and semi-arid locations (Black Mesa/Kayenta <br />Mine, Tuba City, AZ; McKinley Mine, Gallup, NM; San Juan Mine, Farmington, NM, ColoWyo <br />Mine, Craig, CO; Seneca Mine, Hayden, CO, Trapper Mine, Craig, CO, etc.). The Red Rock <br />Mine site does not require irrigation to establish rangeland seed mixtures. <br />Irrigation has limited benefits and significant adverse side effects on rangeland plant <br />establishment and growth. Most mines in the arid and semi-arid region do not use irrigation in <br />their reclamation processes. Irrigation has the following drawbacks: <br />• Seedling Moisture Dependency-When the unnaturally high level of moisture <br />supply is discontinued excessive dieback frequently occurs; <br />• Hydrophyllic Plant Physiology-Genotype and environment combine to create the <br />phenotype. Excessive water can create a dependency upon water that kills the <br />plant when extended periods of low plant available soil moisture occur; <br />• Aggressive Plant Species Establishment-Irrigation favors the development of <br />aggressive plant species such as cool-season grasses and noxious weeds, typically <br />at the expense of warm-season species and desirable forbs; and <br />• Seedling Establishment Failure-Sporadic or ill-timed use of irrigation waters may <br />• result in germination of species at times during their normal growing season that <br />are inappropriate for successful establishment. <br />Irrigation is a costly management practice that provides little or no benefit to the establishment <br />of native rangeland plant species, while representing a potential source of significant vegetation <br />establishment problems. <br />As an example, irrigation has been used to establish vegetation on arid mined lands where annual <br />precipitation is less than nine inches per year (Navajo Mine, Farmington, NM). The operating <br />philosophy supporting irrigation was that first-year irrigation establishes the seeded species and <br />second-year irrigation ensures vegetation stand development and seedling maturity. Irrigation <br />generally was not applied after the second growing season (Porterfield, 1990). Field inspections <br />performed one and two-yeazs after cessation of irrigation typically observed significant decline <br />of seeded grasses, shrubs and forbs, even though the seeded species were genetically adapted to <br />azid conditions. Plants that germinated and developed under irrigated conditions adapted <br />physiologically to this increased moisture regime. "Addiction" to irrigation water resulted in <br />morphological changes to roots, stems and leaves that could not withstand the removal of <br />irrigation. Additionally, seedling density established under irrigated conditions could not be <br />supported under natural conditions (Wertz, G. Personal Communications, 2002). Similar <br />vegetation responses to irrigation and irrigation removal were observed on test plots established <br />in 1998 and 1999 at the Rocky Mountain Arsenal north of Denver, Colorado. <br />• Appendix G 5 06/28/02 <br />