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<br />-z- <br />or have been irrigated with flow from Rapid Creek. The T, terrace includes a <br />narrow band of subirrigation along the creek, the species present are not <br />agriculturally useful. subirrigated species located on the TZ terrace are deep <br />rooted and do not indicate the general availability of ground water to <br />agriculturally useful species. The T3 terrace does not have any plants indicating <br />subirrigation. The TZ and T3 terraces should be identified as alluvial valley <br />floors because of their ability to support flood irrigated agricultural activities. <br />Since no information has been provided concerning the agriucltural significance <br />of these alluvial valley floors, the areas will be assumed to be significant <br />and all three AVF findings should be made. Since no mining activities would be <br />located in or adjacent to the potential alluvial valley floors it would be <br />relatively easy to determine that the proposed operations would not interrupt, <br />discontinue, or preclude farming on the alluvial valley floors. <br />The applicant should show that the proposed mining operations would not cause <br />material damage to the surface and ground waters that supply the AVF. In this <br />case, water released from upstream reservoirs crosses the permit area by way of <br />Cottowood and Rapid Creeks to be diverted for use on the AVF's. The applicant <br />should describe this flow and provide a technical assessment of the probable <br />hydrologic consequences of mining upon this flow and proposed mitigations if <br />appropriate. <br />A determination that the essential hydrologic functions would be preserved <br />should be possible, provided that the supply of water to the alluvial valley <br />floor is preserved. <br />Other Streams <br />Several minor, ephemeral streams also drain the permit area. These stream <br />valleys are narrow, steep, and contain very little alluvium. None of these valleys <br />contain deposits meeting the AVF size criteria. <br />Colorado River <br />This area has been identified as terrace landforms with existing flood irrigation. <br />The higher terraces are not subirrigated, but the lowest terrace is marginally <br />subirrigated. This portion of the Colorado River should be identified as an <br />alluvial valley floor because of flood irrigation. <br />Since no information has been provided concerning the agricultural significance <br />of this alluvial valley floor, the area will be assumed to be significant and a1Z <br />three AVF findings should be made. <br />As with Rapid Creek, the findings that the operations would not interrupt, <br />discontinue, or preclude farming and that the essential hydrologic functions <br />would be preserved should be relatively easy to make. However, a finding of <br />no material damage will require additional technical analysis. The applicant <br />should provide an assessment of the effects of mine water discharge and coal <br />refuse leachate upon the quality flow of the Colorado River on a monthly basis. <br />Once the additional technical assessments have been performed, the alluvial valley <br />floor findings can be easily completed. Several related topics should also be <br />addressed: <br />