2011-08-15_REVISION - C1981008 - Laserfiche WebLink

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C- 1981 -008 TR -60 Preliminary Adequacy Review 15- Aug -2011 Page 3 of 4 Please revise the index of Maps for Section 2.05.3(3) to include each of the items listed above. 2.05.3(3) Text a) Page 2.05.3(3) -2, last paragraph the rule referenced is incorrect — please change to 4.05.2(7) b) Page 2.05.3(3) -7, second paragraph — please replace this paragraph with the following sentence: "Updates and modifications to the mine pit dewatering plan are described in Section 2.05.3(3), subsection 6." c) On page 2.05.3(3) -12, the first sentence should read, "...WFC will use Ponds 008 through 015 ", rather than 014; d) In the table on page 2.05.3(3) -12, please revise to show that Pond 007 is shown on Maps 2.05.3(3) -2 -1 and -2 -2, and that Pond 008 is shown on Maps 2.05.3(3) -4 -1 and -4 -2; e) In the last paragraph on page 2.05.3(3) -12, the second sentence should read, "Pond 011 and Pond 013 will have..." f) Page 2.05.3(3) -14, fifth paragraph — please replace the last two sentences with the following: "Mine pit dewatering was transferred from Pond 011 to Pond 013 in June 2011. These changes are reflected in the amended NPDES permit. g) On page 2.05.3(3) -19, last paragraph, please add that Pond 012 was excavated in Spring 2005, and revise the third sentence to state that Ponds 011 and 013 were constructed in late 2008. Please add that Pond 014 was constructed in Spring 2004, and reclaimed in Fall 2009. 4. Attachment 2.05.3(3) -1 Collection Ditches and Culverts a) The As -Built Drainage Area for Ditch C27, which flows to Pond 015, is given as 6.163 acres, which is less than half the 12.6 acres used in the design. Please provide an explanation of the reduction in area. b) The runoff curve number, CN, for Ditch C27 has been reduced from 79 to 76. Please provide a rationale for the curve number selected, including the assumed Hydrologic Soil Group and any other factors considered. c) For Ditch C27 channel design, the as -built Bed Slope is given as 2.04 %, while the Design slope was given as 6.50 %. During an earlier field inspection of the site, prior to construction, Ross Gubka indicated that the ditch gradient would be approximately 0.5 %. Please verify that the value used is consistent with the ditch as constructed. d) The Channel Lining is now described as "Sandy loam noncolloidal ". During a site inspection, the channel was observed to be lined with materials of varying characteristics, including fractured rock. Please verify that accurate materials and values have been considered and selected for incorporation into the analysis. e) For Ditch D 1 W, which diverts "clean" water from the as- yet - unmined western area of the permit, the Drainage area has been reduced — from 12.6050 acres to 6.7800 acres. The text explains that this is due to the contributions of several different sub - watersheds. (No response is needed.) Attachment 2.05.3(3) -18 - NPDES Permit With TR -60, amended Discharge Permit No. CO- 0000213 has been provided for inclusion in the permit as Attachment 2.05.3(3) -18. The permit, issued by the Colorado Department of