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-44- Areas of historic flood irrigation have been identified in the Picketwire Valley adjacent to the proposed permit area (Plate 6A, and Map 8 of the permit application). Areas of flood irrigation are-f:.ound along the North Fork of the Purgatoire, the Picketwire Valley, and the Stonewall Valley. In the mine area, flood irrigation is confined to the valley floor deposits found adjacent to the river. The water is directly diverted from the river through ditches. The most common irrigation method is "wild flooding", although border and furrow irrigation are practiced in some areas. The dominant crop is a grass-hay consisting of a mixture of clover, alfalfa, timothy, brome, and other grasses. Downstream of the Maxwell mine site, flood irrigation is practiced on the strath terraces. Based on the information provided in the application, the Picketwire Valley (main stem of the Purgatoire River) is found to be in alluvial valley floor. The valley floor deposits have essential hydrologic functions supporting both flood irrigation and subirrigation, and the strath terrace deposits have the capability for flood irrigation. No information has been provided concerning the significance of the alluvial valley floor to farming operations. The valley floor deposits identified along the Main stem of the Purgatoire River have not been disturbed by past mining activities at the Allen Mine. The Division must make the required findings by assuming that this portion of the alluvial valley floor is significant to fanning. Picketwire Valley Findings 1) The proposed mining operation would not interrupt, discontinue or preclude farming on the alluvial valley floor. No surface disturbance related to the Allen Mine is planned in the Picketwire Valley. The proposed mining operation will not undermine the Picketwire Valley. 2) The proposed mining operation would not cause material damage to the quantity and quality of surface and ground water that supply the alluvial valley floor. The disturbed area at the Allen Mine has been determined to be "grandfathered" from causing material damage to the quantity and quality of water supplying alluvial valley floors. Very little additional disturbance has occurred since August 3, 1977, and the only additional disturbance planned is the addition of coal processing waste in the disposal pile and addition to a "pre-law" coal processing waste pile. These additional disturbances are anticipated to have an insignificant effect on the quality of water flowing in the Middle Fork of the Purgatoire River. Since the proposed operation will not undermine the Picketwire Valley, there will be no effects on the quantity of water supplied to the alluvial valley floor.