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<br />-44- <br />The Picketwire Valley alluvial valley floor is supplied by surface water and <br />alluvial ground water. The applicant has provided an assessment of the <br />effects of undermining the alluvial valley floor under a limited extraction <br />mine plan upon flow in the stream/alluvial aquifer system (see applicant's <br />discussion of probable hydrologic consequences). The flow depletion from the <br />system is estimated to be 2.3 gpm. This potential effect was demonstrated to <br />be minimal and would not cause material damage. The applicant has also <br />projected the effect of discharging water from the underground workings to the <br />receiving stream. This effect was shown to have a minimal effect upon water <br />quality, and would not cause material damage. These activities are approved <br />by the Division. <br />The applicant has not projected the effects of the proposed coal refuse pile <br />upon water quality in the stream/alluvial aquifer system. Because of its <br />location, any water percolating through the refuse pile would be expected to <br />enter the stream/alluvial aquifer system. Therefore, the Division cannot find <br />that construction of the pile would not cause material damage to the quality <br />of waters that supply the alluvial valley floor (see discussion in Section VI <br />of this document). <br />3.~ The proposed mining operations would preserve or restore the essential <br />hydrologic functions of the Picketwire Palley alluvial valley floor. <br />The valley fill material along the Purgatoire River was assumed to be <br />significant to agriculture. Therefore, its essential hydrologic functions <br />must be preserved throughout the mining operation. Its essential hydrologic <br />functions are those geologic, hydrologic, and topographic characteristics <br />which make surface and ground water usefully available for flood irrigated and <br />subirrigated agriculture. Except for the existing access road and sediment <br />control and water intake systems, the applicant has proposed no surface <br />disturbance in this area. The applicant has proposed to undermine the area <br />under a limited extraction mine plan. Therefore, subsidence is not expected <br />to alter the topography or to significantly effect surface or ground water <br />systems (see Subsidence section, and discussion of probable hydrologic <br />consequences). <br />A portion of the area identified as a strath terrace has been disturbed by <br />previously approved mining activities. This area has been determined to be <br />eligible for a "grandfathering" exemption under Rule 2.06.8(5)(a)(c)(8)(I). <br />Therefore, in this area, the applicant is only required to restore the <br />essential hydrologic functions of the alluvial valley floor. For this area, <br />the essential hydrologic functions are those geologic, hydrologic, and <br />topographic characteristics which make surf ace water usefully available for <br />flood irrigated agricultural activities. The applicant has constructed a coal <br />refuse pile on a portion of the strath terrace. All additional disposal of <br />refuse material will be in Ciruela Canyon. It is not economically feasible <br />that water can be delivered to this site for agricultural purposes. <br />Therefore, this strath terrace does not meet the AVF criteria. <br />