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1 <br /> <br />I~ <br /> <br /> <br /> <br /> <br />t <br /> <br /> <br /> <br /> <br />1 <br /> <br /> <br /> <br />BATTLE MOUNTAIN RESOURCES, SAN LUIS PROJECT <br />CMLRD ADEQUACY LETTER RESPONSES <br />Page 25 of 28 <br />The velocity in the revegetated section of the reclamation <br />spillway is 3.1 fps during the 100-yr, 24-hr storm event. The <br />spillway will be excavated within the cemented gravels of the <br />Santa Fe formation. Stabilization of the spillway by <br />revegetation will be sufficient to control erosion during the <br />100-yr event. <br />e. Revegetation will be using the grass species outlined in <br />Exhibit E, Section E.2.5 of the approved permit. <br />44. The collection pond is proposed to be filled with riprap to act as <br />an energy dissipation structure for the engineered spillway upon <br />reclamation. What size riprap and thickness of riprap will be used? <br />What depth of overburden, if any, will be placed over the folded-in <br />liner? What size and thickness of riprap bedding material is <br />proposed? <br />RESPONSE: The collection pond embankment will be breached during reclamation <br />to provide for reestablishment of drainage. It is anticipated that <br />a 160-ft wide section of the embankment will be removed resulting <br />in an outlet at an elevation of 8450 ft. This material can then be <br />used to bury the folded pond liner resulting in a burial depth of <br />four ft before riprap is placed. <br />Several riprap sizes will be required to stabilize the reclaimed <br />collection pond. <br />At the outlet from the 100-yr channel into the collection pond, a <br />hydraulic jump basin is required. Grouted riprap similar to the 100- <br />yr storm channel is anticipated to be required. This area extends <br />for a length of 35 ft from the 100-yr channel, flaring at 5.5° to a <br />final width of 11 ft within the collection pond. Flow velocities will <br />be less than three fps and a nominal riprap DSO will be required. <br />At the collection pond outlet, flow velocities during the 100-yr <br />storm event will be approximately 5.2 fps. A DSO of 0.2 ft is <br />required. <br />Calculations for the hydraulic jump and riprap sizing are contained <br />in Attachment 16. Bedding material gradation is as recommended in <br />Item 43. <br />45. Has consideration been given to grouted riprap versus the concrete <br />proposed for the spillway entrance and control section? This may <br />alter the hydraulics somewhat but may improve the post-mine <br />appearance upon reclamation. <br />RESPONSE: Grouted riprap will be used far the spillway entrance and control <br />section. For channel design see response to Question 43. <br /> <br />