2012-07-11_REVISION - C1981012 (2)

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Zach Trujillo -2- July 9, 2012 4. Please provide a description on how the proposed ventilation shaft will be lined to minimize disturbance to the prevailing hydrologic balance in accordance with Rule 4.07. The Division feels that shotcrete lining may not be adequate enough for long -term protection and suggests that concrete lining be used. NECC - Attached are amended pages 2.05 -54 and 55. Pages 2.05 -54 explains that any water bearing zone(s) in the shaft will be ring grouted from the surface. There should be no concerns with using a shotcrete lining since water inflows will be sealed off by grouting, 5. It appears that ditch D26 flows into ditch D58. Please provide an explanation on how this is accounted for in the design, including the size of the drainage area. NECC - Ditch D26 does not flow into ditch D58. Clean water ditch D26 flows through two culverts located east of pond 7 and into the river. 6. A drainage reaches the valley floor approximately 80 feet west of the proposed Bates Shaft in close proximity to the point where ditches D59 and D60 both begin (the up gradient ends). Please provide an explanation on how the flow down this drainage will be directed to D60 rather than D56. (Based on areas in the SEDCAD model, it is apparent that D60 receives these flows.) NECC - The drainage described above will flow into D60. The drainage currently flows in the direction of D -60 into culvert C80. 7. Please send a revised Table 20, Ditch Data. Some of the values for ditch D59 appear to be incorrect including the peak discharge and the ditch slope; they do not match the values in the SEDCAD printouts. Also, the page number for this table may be incorrect. Should it be 2.05-11b? NECC - The data for ditch D59 located in Table 20 was amended. Attached is revised Table 20 Ditch Data, page 2.05-11 a. 8. In Table 21, culverts C79 and C80 are listed as having a minimum diameter of 36 inches. A field inspection from early May 2012 reveals that C79 will need to be replaced to meet this requirement. If this project is constructed, please make sure this replacement is performed. NECC - Comment noted. 9. It appears that a mistake may have been detected on page EXEI 19(21) -2. The units for the three year sediment volume should be acre -feet, not cubic feet. Please provide an updated page EXH 19(21) -2. NECC - The units for the three year sediment volume were revised. Enclosed is revised page EXH 19(21) -2.