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Tuba City, AZ; McKinley Mine, Gallup, NM; San Juan Mine, Farmington, NM, <br />ColoWyo Mine, Craig, CO; Seneca Mine, Hayden, CO, Trapper Mine, Craig, CO, etc.). <br />The Red Rock Mine site does not require irrigation to establish rangeland seed <br />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 <br />irrigation in their reclamation processes. Irrigation has the following drawbacks: <br />• Seedling Moisture Dependency -When the unnaturally high level of <br />moisture supply is discontinued excessive dieback frequently occurs; <br />• Hydrophyllic Plant Physiology- Genotype and environment combine to <br />create the phenotype. Excessive water can create a dependency upon <br />water that kills the plant when extended periods of low plant available <br />soil moisture occur; <br />• Aggressive Plant Species Establishment - Irrigation favors the development <br />of aggressive plant species such as cool - season grasses and noxious <br />weeds, typically at the expense of warm - season species and desirable <br />forbs; and <br />• Seedling Establishment Failure- Sporadic or ill-timed use of irrigation <br />waters may result in germination of species at times during their normal <br />growing season that are inappropriate for successful establishment. <br />Irrigation is a costly management practice that provides little or no benefit to the <br />establishment of native rangeland plant species, while representing a potential source of <br />significant vegetation establishment problems. <br />As an example, irrigation has been used to establish vegetation on arid mined lands <br />where annual precipitation is less than nine inches per year (Navajo Mine, Farmington, <br />NM). The operating philosophy supporting irrigation was that first -year irrigation <br />Appendix G 8 07/01/02 <br />