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C I r1 LJ CONCLUSIONS In the original Findings of Compliance Document for the Golden Fagle Mine (Permit No. C-81-013), Santistevan Canyon was conservatively determined to be an AVF because the areal extent of unconsolidated stream-laid deposits met the minimum size requirements. The Division made this finding because sufficient information was not provided concerning the presence or absence of subirrigation. In addition, the above referenced stipulations were placed on the permit to gather appropriate information for an assessment of potential impacts associated with secondary or retreat mining. The following sections present AVF characteristics of Santistevan Canyon and the probable hydrologic consequence of longwall mining under the area. AVF Determination Geomorphic Criteria Santistevan Canyon has been mapped to meet the minimum AVF size requirements for stream- laid deposits (see Exhibit 6, Hydrology and Geology Information). Verifying this mapping during the May 1989 field activities revealed significant inclusions of bedrock material in and adjacent to the channel bottom. In fact, the channel bottom itself was primarily bedrock. The road following the channel is placed on the terrace material and in areas is directly on the bedrock of the channel bottom. There was no evidence of reworked alluvium in and adjacent to the channel bottom. These observations suggest that although areas in these canyons may contain stream-laid deposits, it is doubtful that those deposits form a contiguous unit to meet the geomorphic criteria. Water level data collected from the six monitoring piezometers installed in the canyon also confirm this assumption. Water Availability Characteristics lands meeting the geomorphic characteristics, but which are not identified as flood irrigated, Moor irrigable, or subirrigated can be released from further AVF study. Santistevan Canyon has not been historically flood irrigated az evidenced by the lack of irrigation structures. The lower portion of the canyon does contain a flood irrigation ditch with water being diverted from the Purgatoire River. The irrigated area is approximately two aces in size and can be considered pan of the Purgatoire AVF since it is at the same elevation and utilizes the same water. Santistevan Canyon cannot be economically flood irrigated a[ an elevation above the 7,200 Coot level (the current level of irrigation) because of the expense of constructing extensive diversion ditches from the Purgatoire River. In addition, the Purgatoire has been over-appropriated and obtaining new surface diversion rights is not possible. The canyon does not contain sufficient subirrigation to sustain agriculturally useful vegetation communities. The dominant vegetation community in the canyon bottom is a native cool season and warm season grass mixture. As such, this community is not dependent upon subirrigation. Indicator species of subirrigation include cottonwood, willow and sedges/rushes. When present, these species are found in very small areas only in the drainage bottom. If a significant source of subsurface water was available, these species would have a greater geographic range in the canyon. Utilizing the vegetation species area concept and limited slug test results from the monitoring piezometers, it is likely that no significant subsurface aquifer is present in the canyon. Therefore, the potential Cor irrigation by pumping alluvial material would be severely limited. In addition, bedrock aquifers have not been identified which may supply economic water for irrigation. Summary With the information collected during this azsessment, WFC requests that the Division find that Santistevan Canyon is not an AVF Cor the following reasons: there is no regional past or present precedence for irrigation of small side canyon drainages; Santistevan Canyon is not 7