2011-09-09_APPLICATION CORRESPONDENCE - C2010089 (2)

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C- 2010 -089 PAR No. 2 New Horizon North Mine 9- Sep -2011 Page 15 of 25 such a demonstration for ponds NHN -002 and NHN -003 or revise the ponds' embankment slopes accordingly. The Division requests that clearer and larger scale figures of plan views and cross sections for the three sediment ponds in Appendix 2.05.3(4) -1 be provided. Also, please provide plan views with a contour interval smaller than the current five feet. The current figures do not show enough detail. h) In the 3 complete paragraph on page 4 of the Arcadis report in Appendix 2.05.3(4) -1, there are two sentences in which it is stated that the primary discharge structure will be a drop inlet. However, the certified pond cross sections in the same report show that the primary discharge structure is a straight, 18 inch or larger diameter pipe with a 6 inch diameter gated valve. Please revise this paragraph accordingly. i) The certified pond cross sections in the Arcadis report in Appendix 2.05.3(4) -1 show that the gates on the primary discharge pipe are on the inside of the pond embankment. How does Western Fuels propose to open the discharge gates if the water level is well above the gated valve? In Appendix 2.05.3(4) -1, "ARCADIS Report on Sediment Control ", it is stated on the cross - sections for the three sediment ponds that 18 inch or larger cmp principle spillways will be installed. However, Rule 4.05.9(14)(b) requires that a professional engineer certify that the pond has been constructed as designed. Therefore, an exact construction design is required. Please revise the three sediment pond cross sections to state the exact diameter of the principle discharge tube. 5. Map 2.05.3(3) -1, "Surface Water Hydrology ", has several depictions that are not explained, either on the map or in the map legend. Such depictions include the black, blue, dark orange and magenta colored lines, as well as the mine plan year numbers 2013 through 2018. Under Rule 2.05.3(3) and (4), please add labels on the map or explanations in the map legend that describe what the depictions represent. DRMS: The Division has no further concerns with this question. Map 2.05.3(3) -1 was revised appropriately in the submittal dated May 26, 2011. However, the Division has one additional request regarding this map. a) On Map 2.05.3(3) -1, please add a line to connect the SW -FA notation with the SW -FA drainage area. 6. Response accepted. 7. Response accepted. 8. Response accepted. 9. In Table 2 of the pond memo in Appendix 2.05.3(3) -1, design capacities of the three sediment ponds are listed. Each pond's listed capacity is the total pond volume up to the emergency spillways. However, since a sediment pond cannot be dewatered below the lowest discharge elevation of the discharge structure, a sediment pond's designed capacity has to be able to contain the runoff from the 10 year -24 hour event as measured from the elevation of the lowest discharge point up to the elevation of the emergency spillway. Please provide demonstrations that the three ponds have sufficient capacity above the lowest g) J )