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as proposed in the original permit application, since no additional mining will take <br />place. <br />Ponds Nos. 1 and 2 are being retained as permanent structures at the mine site, per <br />Technical Revision No. 6, approved by the Division in August, 1991. The <br />O.S.M.R.E. concurred with the Division's on April 15, 1992. Pond Nos. 1 and 2 were <br />reviewed for compliance with the performance standards of Rule 4.05.9. The designs <br />of both ponds were found to meet the requirements of this section. <br />Al] the ditches were reviewed and found to meet the design requiremenu of Rule <br />4.05.3. Culverts associated with the collection ditch system were adequately sized. <br />In the past, the only potential water quality concern related to pumpage of pit water <br />into the ponds and surface water system. This activity will not occur as the <br />development of Pit 2 has been terminated. Runoff amounts from summer storms are <br />limited based on the low annual precipitation occurring in North Park. Surface <br />runoff leaving the site is largely a function of snowmelt events. NPDES reports have <br />shown that these discharges continue to meet water quality effluent standards. <br />A. Probable Hydrologic Consequences <br />1. Effects on Surface Water <br />The surface water effects discussed are related orily to Bolton Draw, since this is the <br />only receiving stream for waters leaving the Canadian Strip Mine site. <br />The probable hydrologic consequences are limited to a change in the timing of <br />stream flow and minor changes in water quality because of the sediment ponds <br />located on the mine site. It is not expected that the total amount of water will be <br />reduced significantly by evaporation of water contained in the ponds. More likely, <br />there will be only a change in the timing of runoff leaving the mine site because of <br />temporary storage and detention of runoff in the two detention ponds. <br />Surface water quality effects due to mining were identified as a potential for <br />increased salt loading. The extent of mining has been decreased from that originally <br />proposed, as Pit 2 will not be developed. The pumpage of pit water with elevated <br />total dissolved solids (TDS) concentrations relative to surface water levels will not <br />occur as originally projected. With the continued establishment of vegetation on <br />pre~~ously reclaimed portions of the mine site the effects on surface water quality are <br />considered negligible. <br />Information on surface water hydrology maybe found in Appendix C, Volumes I and <br />II of the permit renewal application. <br />Canadian Strip Mine, C-81-026 lg July 31, 1992 <br />