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<br /> <br />0 <br />-3- <br />15. The applicant should clarify the conditions under which irrigation water <br />would be released from Pond A. Federal regulations prohibit ttie dewatering`of <br />the sediment storage through a dewatering device. If irrigation water is <br />released, how would effluent limitations be met? <br />16. Refer to Page 81G-194. Peak flow estimates for road culverts assumes <br />that runoff is decreased from reclaimed areas. Calculations should be redone <br />using a higher curve number. Peak flow estimates should also make slope and <br />basin shape adjustments. <br />17. ,fudging from [he map, culvert spacing is not 1n compliance with Federal <br />Regulations. Clarify or submit revised map. <br />18. For class I roads, the road-surfacing material is to be reinnved rather <br />than covered with topsoil as is acceptable for class II roads (pg. 816-203). <br />(ApplicanC proposed to cover roadsurfacing ma[ert.al wiCh topsoil rather than <br />remove it). <br />19. Page 816-34 reports that no permanent stream diversions are planned. The <br />South Tributary to Foidel Creek meets the Federal definition of an <br />intermittent stream. Ditch 26-2 associated with excess spoil stockpile 26 <br />should be designed in compliance with 816.44, 1E the excess spoil pile is <br />permitted. <br />20. Calculations for ditch 26-2 are based upon 95 acres of watershed. `lap 14 <br />indicates that more than 750 acres drain [o [he ditch. Calculations should be <br />redone using the proper drainage area. <br />21. Curve numbers used to calculate flow for thu permanent diversions appear <br />low. What assumptions went into the selection of curve numbers? Show <br />calculation of average curve numbers. If the runoff from reclni.med surfaces <br />is assumed to be less that from natural surfaces, ditches should he red esi.l;ned <br />using higher curve numbers. <br />22. The "n" values used to determine flow velocities in Che permanent ditches <br />appear high. Demonstrate the applicability of [here values. Provide example <br />calculations of velocity. <br />23. The application proposes to recreate ephemeral drainages crossing the <br />disturbed area. However, no information has been provided on the design of <br />the restored stream channels. Cross-section B, which follows a restored <br />valley at its lower end, suggests that at .least one stream channel gradient <br />oversCeepened. This would likely lead to erosion problems. The applicant <br />should provide a detailed plan for the reconstruction of stream drainages <br />including pre-and postmining longitudinal profiles, stream cross-sections, <br />design flows adequate to demonstrate minimal disturbance to the hydrologic <br />system. The plan should identity any channel reaches where the channel <br />material is other than regraded spoil. <br />is <br />and <br />J <br />U <br />.~....~.:. 1.: J:..d0..~1 :.:. .... _T.CI2SC L^t~:..: .. <br />