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<br />XVI. Concurrent Surface and Underground Mining <br />No specific approvals have been granted under this section (4.22.2). <br />XVII. Operations on Alluvial Valley Floors <br />A. The Division has determined that an alluvial valley floor exists within the affected <br />or adjacent area. Therefore, the following findings are in order for the portion of <br />the alluvial valley floor known as Purgatoire Rir•er AVF located at the mouth of <br />Lorencito Canyon and flood irrigated by the Chacon ditch. <br />The Division finds that activities proposed by the applicant will not interrupt, <br />discontinue, or preclude farming on the alluvial valley floors that are irrigated or <br />naturally subimgated. Although the coal loadout will be constructed on <br />approximately 7 acres of irrigated pasture, feeder ditches will be constructed as <br />necessary to continue irrigation of the remaining pasture. (4.24.3(1)). <br />The proposed activities will not materially damage the quantity or quality of water <br />in the surface or ground water system described above. Locating the coal loadout <br />on the alluvial valley floor will not cause measurable changes in the water <br />quantity or quality. Local material will be used for the fill, where necessary. This <br />material is not acid-forming or toxic, as demonstrated by geochemical analysis of <br />materials throughout the permit area. Waters that irrigate the pasture are taken out <br />of the Purgatoire River above the confluence with Lorencito Canyon. At a <br />maximum discharge rate of 65 gpm to Cow Canyon and typical mine water <br />discharge quality, changes to water quality in the Purgatoire would be minimal. <br />TDS may increase from 25l mg/1 to 267 mg/1 for the waters that irrigate the <br />Chacon pasture. SAR may increase from 1.02 to 2.72. Neither of these small <br />changes would affect the usability of this water for imgation. (4.24.3(3) and <br />2.06.8(5)(a)(ii)) <br />Surface coal mining and reclamation operations will be conducted to preserve the <br />essential hydrologic functions of alluvial valley floors outside the perniit area and <br />to reestablish the essential hydrologic functions of alluvial valley toors within the <br />affected area throughout the mining and reclamation process. The location of the <br />coal loadout on a small portion of the Purgatoire River AVF will not affect the <br />hydrologic function of the AVF, during operations or after. Upon final mine <br />closure, fill materials will be removed, and the disturbed area ripped, topsoiled, <br />seeded and mulched. This will restore the hydrologic function ofthe immediate <br />disturbed area to pre-mining levels. The disturbed area will be compared to the <br />similar irrigated pasture area for determination of revegetative productivity of the <br />disturbed AVF area.(4.24.2) <br />B. An environmental monitoring system shall be installed, maintained, and operated <br />by the permittee on all alluvial valley floors during surface coal mining and <br />23 <br />