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Amended Findings Document for Permit Renewal (1487), and Teckmical Revision AFo. 14 (1984) <br />also include discussions of probable hydrologic consequences. Section 2.04.7 of the PAP and <br />Section VI of the 1982 Findings Document contain extensive discussion of the hydrologic <br />balance of the pertnit azea. <br />1. Potential Effects on Sutface Water Quantity <br />Based bn the hydrologic balance calculations for the drainages in the general area and the fact . <br />that al] runoff from the mine azea is to be either diverted azound the mine or retained in <br />sedimentation ponds for a maximum of 36 hours (Division of Water Resources), no change in <br />the hydrologic balance will occur. Since the azea to be mined is a fraction of the total watershed <br />azeas, the general area will not be affected. <br />The probable hydrologic consequences (PHC) section of the 1982 Findings Document predicted <br />that there would be no.significant effects to the hydrologic balance of Taylor, Wilson or <br />Goodspring Creeks as a result of mining. Monitoring data in the mine's Annual Reclamation <br />Reports (ARR's) to date confirms that there have been no signi£cant impacts on water quantity.of <br />these streams to date due to mining operations at the Colowyo Mine. <br />Estimations of surface water runoffbased on pre-mining and post-mining.conditions aze <br />included. on page2.04:7-89 of the PAP: It is estimated thatsurface runoff from the permit area <br />will decrease by 36 acrefeet per yeardue tb increased i~ltration and evapotranspiration: This. is <br />approximately two percent of the estimated annual flow of Goodspring and Taylor Creeks <br />downstream from the pemrit area. During its adequacy review of Permit Revision No. 1, the <br />Division raised several questions about the modelirg assumgtious used for generating these <br />numhers and sizing surface water control shvctures. The Operator re-evaluated the modeling <br />procedures. All structures built before August 31, 1992 adequately detain and treat alt waters <br />originating from azeas disturbed through December 31, 1992. Structures built after August 31, <br />1992 detain and treat all waters originating from all remaining azeas disturbed. The Division <br />finds ncrsignifieant impacts tv surface water quantity dueta Colotayo-s mining operations_ <br />Mined azeas will be reclaimed to approximate original contour with the exception of three excess <br />spoil fills. The sizes of drainage areas for some ephemeral and intermittent drainages within the <br />mined area will-be changed; however, there will be na changes to drainage sizes, far C,oodsgring, <br />Taylor:or Wilson Creeks. The proposed mine plan projects 4,345 acres of disttutranee during the <br />Life of mine_ As of the fall of I99I, approximately 503 acres of disturbed land in the East Pit and <br />Section I I Pit had been reclaimed. As of the end of 1996, a total of approximately 1,066 acres of <br />disturbed lands had been backfilled and graded, and 1,052 acres seeded. As of 2001, 1,376 acres <br />of disturbed lands had been backfilled, graded and seeded (2001 ARR). <br />Runoff in the permit azea, which is diverted or detained, will continue to reach the historic <br />drainages. A portion of the water rights held by Colowyo on Goodspring Creek maybe <br />consumed in accordance with the augmentation plan discussed in Exhibit 7 of the Permit. <br />October 21, 2002 29 <br />