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VIII. Alluvial Valley d oors - Rules 2.06.8, 2.07.6(2)(k) and 4.24. The Hay Gulch area has previously been documented (see National King Coal, Inc., findings, February 4, 1982) to be an Alluvial Valley Floor (AYF) and for the purposes of this findings document is considered to be an AVF. Field observations by Division staff and information contained in other permit applications indicate that small areas of unconsolidated stream-laid materials are present in adjacent drainages. However, these areas are not extensive enough to meet the size criteria of AVF's. It has been determined that Hay Gulch meets the criteria for an Alluvial Valley Floor based upon the following: (1) The valley contains unconsolidated stream-laid deposits; (2) The valley contains sufficient water to support agricultural activities as evidenced by (a) The historical use of flood irrigation in the area, (b) The demonstrated capability of the area to be flood irrigated, and; (3) The demonstrated subirrigation of the area. It should be noted that Hay Gulch does not presently contain a stream. It is thought by the Division, however, that this is due to agricultural practices which divert naturally occurring flow into the Hay Gulch Ditch. Furthermore, it is thought that the original channel has been removed by local agricultural activities. The Hay Gulch irrigation ditch, which parallels La Plata County Road 120, is used for flood irrigation purposes in the vicinity of the Blue Flame Coal Mine. Furthermore, it has been demonstrated that the naturally occurring water table of the AVF varies from above ground surface to about three feet below the surface (see Section V of this document). This demonstrates that sufficient water is available for subirrigation purposes. Furthermore, the identified land use on the AVF is primarily pasture land with occasional hay production. The essential hydrologic functions that supply water to the AVF are both flood irrigation and subirrigation as described above. The applicant has not presented any information regarding the significance of the AYF to the individual farming units; therefore, the AYF must be considered significant far purposes of this findings document. The potential for impact to the AVF from the Blue Flame Loal Mine is minimal. Two potential impacts have, however, been identified: 1) It is possible that water which has collected in the sediment pond could infiltrate into the AVF near the mine site. Tne potential for this leachate to adversely affect the AVF is small due to the potential for dilution within the AVF (see Se=tion V of this document). Furthermore, it is much more likely that the Hay Gulch AVF would contribute water to the material in which the pond is to be constructed rather than that material contributing water to the unconfined alluvial aquifer. -11-