2012-06-20_PERMIT FILE - C2010089 (87)

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from ground water aquifers. Nonetheless, such monitoring is required. Only with the results of measurements at existing mines can projections be made for future mines. Considering then the probable importance of subirrigated alluvial valley-floore, and the potential for disrupting the hydrologic and biologic functions thereof, it was considered appropriate to evaluate the amount of land that would be classified as subirrigated alluvial valley floors. This paper reports efforts directed at the identification of alluvial valley floors as those areas are defined in •posed national legislation. Appendix 2 provides quotations from legislat "•.posals and Committee Conference Reports that have addressed mining in all a `val _ floors. These proposals may be summarized as indicating that an al j- oor is: - A geologic unit comprised of several parts: A hydrologic unit in which the natural surface water and ground water is adequate to support agricultural activities such as hay production, by virtue of sufficient moisture held available to enable continued growth of suitable vegetation during the dryer summer and fall months; - A topographically - defined area in which the floor plain and adjacent low terraces may be irrigated by simple spreading of ephemeral waters and /or by simple diversion of natural flow*, and - An area of land used for farming. This report includes both a reconnaissance identification of subirrigated allu- vial valley floors, through analysis of - surface features, and a preliminary analysis of hypothetical subsurface conditions that appear representative of actual condi- tions. It was not possible to investigate the actual uses or productivity of those areas mapped as alluvial valley floors. In the context of proposed legislation, it is therefore inappropriate to directly transfer the areas of alluvial valley floors presented herein to an impact on surface - mineable coal since the proposed legisla- tion applies to farmed areas (and to water quantity and quality) and "farmed areas" are not identified. It is similarly inappropriate to conclude that this study has adequately documented the hydrologic and biological systems that exist in alluvial valley floors, We have, however, attempted to provide an analysis of specific im- pacts on the hydrologic system that may result from surface methods of mining shal- low coals. This study draws upon research performed by others to initiate an analysis of whether those functions of alluvial valley floors deemed critical in the study can be reestablished during mining and reclamation. Research to Date The concept of alluvial valley floors utilized recently is new to those not directly associated with western agriculture. Little research has been initiated on the geohydrologie and biologic inter - relationships within alluvial valley floors or on land nee activities conducted therein. This section discusses pertinent investi- gations reported to date. * We assume that the practice of spreading flood waters includes simple furrows and temporary stream diversions, but excludes extensive grading of land and /or construc- tion of canals. These latter efforts may be used to convey water from streams and impoundments to high terraces covered with thin alluvium and colluvium and lying • outside the subirrigated alluvial valleys.