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

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eb adversely affect the waters of an alluvial valley floor. At this stage in our understanding of the hydrologic impacts of mining shallow coals in the West, there is dependence upon site - specific investigations, such as those at the Decker, Belle Ayr, Big Horn, Wyodak, Gascoyne, and Rosebud (MT) mines. It is hoped that some im- proved assessment of regional impacts on water quality as a result of increased coal mining will be developed in the near future. In addition, much uncertainty remains regarding the role of the alluvial valley floor in the regional economic system. As yet, no land use and productivity analyses have adequately evaluated the alluvial valley floor's contribution to the agricultural and recreational economic sectors. Since this analysis of subirrigated alluvial valley floors was preci by proposed legislation, it is appropriate to use the findings of this r- _n iss ,ce investigation to evaluate technical aspects of the proposed 1 ; i o .; l- �s, including alluvial valley floors, should be mined unless prop essential functions can be restored. Such planning would be he applicant's demonstration that the procedures proposed will ad.. estore, or improve upon, those characteristics of the natural system that rently dictate existing environmental equilbrium. Information in this paper su ests that selected areas of subirrigated alluvial valley floors could be mined an t e ong -term agricultural productivity reestab- lished in time, Thus, instead of addressing only a ban on mining in alluvial val- ley floors, this paper also reports on an alternative procedure - that of requiring an applicant to submit a detailed environmental analysis, the content of which is proposed. The detailed environmental analysis would involve extensive requirements for both baseline information and demonstration that proposed reclamation techniques are likely to be successful. There must be sufficient data to permit regulatory agencies to make the judgement that the essential functions of the alluvial valley floor will be successfully restored and /or protected. The reclamation methods pro- posed must have been demonstrated under similar circumstances. Though a ban would • directly involve only three percent of the strippable coal reserves, it would pro- bably make uneconomic the mining of an additional amount of coal due to the need to leave coal in place for pit wall stability and due to the difficulty in creating . logical mining units. Alluvial valley floors which have sufficient subirrigation to support agricul- tural use (harvesting of hay, for example) are, conceptually, important to the eco- nomy of the western United States. They must be protected. In view of the uncer- tainties caused by the few mining plans submitted to mine alluvial valley floors, it may be appropriate to temporarily defer surface mining of coal in subirrigated allu- vial valley floors until a well- defined and comprehensive research program has pro- vided additional information concerning the effects of mining under complex hydrolo- gic conditions. Acknowledgements The authors are indebted to Dr. Harold E. Malde and Mr. Richard Keefer (USGS) who kindly made available the results of their field work and also Mr. Richard Hadley who made available his expertise in the area of hydrology and erosional stability of stream channels. The efforts of an advisory group set up to assist with and review the findings are also appreciated. This group consisted of, in addition to Mr. Malde and Mr. Kee- fer, 3. Herrmann (EPA), J. Mayberry (USGS), J. Ferry (EPA), R. Holmes (EPA), E. Ar- thur (EPA), and A. Lees (FEA). There are, of course', differences of opinion between the authors and the advisory group, and the opinions offered in this report are those of the authors, and thus do not necessarily reflect the positions of members of the advisory group.