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<br />' BATTLE MOUNTAIN RESOURCES, SAN LUIS PROJECT <br /> CMLRD ADEQUACY LETTER RESPONSES <br /> Page 19 of 28 <br />1 <br /> b. The current ditch design calls for a minimum ditch depth of <br /> 2 ft. The design flow would result in a flow depth of 1.5 ft <br />' for ditches constructed at a grade of 1.5 percent. <br /> c. The diversion ditch design should be amended to a 2.5 ft <br />' minimum depth to allow for one-ft of freeboard during the <br /> design storm event. The redesigned ditch has a maximum capacity <br /> of 70 cfs at a flow depth of 2.5 ft. Detail 2 of Figure C-8 <br /> has been revised. <br /> d. Under conditions of design discharge, flow in the diversion <br /> ditches is subcritical in nature with a maximum velocity of <br />3.9 fps (feet per seconds). Reseeding of the ditches is <br /> expected to provide sufficient erosion protection. <br /> 35. A small area without upland runoff control exists between the east <br />' and south diversions. How will runoff from this small ridge area <br /> above the tailings be handled? <br />i RESPONSE: Runoff from this small area will be routed into the south and east <br /> diversions and have been included in the drainage area designs. A <br /> small V ditch (approximately two ft in depth) will extend along the <br />' upper tailings road/berm which will carry these flows into the <br /> respective diversions. These ditches were not included in the design <br /> since the area and associated are very small. <br /> In addition, should the ditch breach, the flows can be easily handled <br /> within the tailings disposal area (and have been included in the PMF <br /> inflow calculations). <br />1 <br /> 36. On page D-61 of the original permit application, the statement is <br /> made that details of the erosion protection/runoff control for the <br /> mill site area wiil be provided upon completion of the mill design. <br />' Have these been developed and, if net, what is the expected timing <br /> of this submittal? <br />' RESPONSE: Detailed designs for runoff at the mill site area are currently being <br /> completed. These designs will be completed following firwal approval <br /> of the pending amendment and will be submitted prior to commencing <br /> mill construction. <br /> <br />IJ <br /> <br />