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of the permit application. The original findings document (1982), an Amended Findings Document for Permit Renewal (1987), and Technical Revision No. 14 (1989) also include discussions of probable hydrologic consequences. Section 2.04.7 of the permit application and Section VI of the 1982 Findings Document contain extensive discussion of the hydrologic balance of the permit area. Potential Effects on Surface Water Quantity General Area Based on the hydrologic balance calculations for the drainages in the general area and the fact that all runoff from the mine area is to be either diverted around the mine or retained in sedimentation ponds for a maximum of 36 hours, no change in the hydrologic balance will occur. Since the area to be mined is a fraction of the total watershed areas, the general area will not be affected. Permit Area The probable hydrologic consequences (PHC) section of the 1982 Findings Document predicted that there would be no significant effects to the hydrologic balance of Taylor, Wilson or Goodspring Creeks as a result of mining. Monitoring data in the mine's Annual Reclamation Reports (ARR's) through 1991 confirms that there have been no significant impacts on water quantity of these streams to date due to mining operations at the Colowyo Mine. Estimations of surface water runoff based on pre-mining and post- mining conditions are included on page 2.04.7-89 of the permit application. It is estimated that surface runoff from the permit area will decrease by 36 acre-feet per year due to increased infiltration and evapotranspiration. This is approximately two percent of the estimated annual flow of Goodspring and Taylor Creeks downstream from the permit area. During its adequacy review of Permit Revision No. 1, the Division raised several questions about the modeling assumptions used for generating these numbers and sizing surface water control structures. The operator has committed to re-evaluating the modeling procedures by August 31, 1992. All structures built before August 31, 1992 will adequately detain and treat all waters originating from areas to be disturbed through December 31, 1992. Structures built after August 31, 1992 will detain and treat all waters originating from all remaining areas proposed to be disturbed as a consequence of this permit revision (PR-01>. Regardless of possible refinements in the modeling, the Division finds that there will be no significant impacts to surface water quantity due to Colowyo's mining operations. Mined areas will be reclaimed to approximate original contour with the exception of three excess spoil fills. The sizes of drainage areas for some ephemeral and intermittent drainages within the mined area will be changed; however, there will be no changes to -20-