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<br />39. In accordance with our comments for Item 38.a., above, please revise the model using a <br />8Y/ curve number of 94 for topsoil stripped, pit, and spoil areas. <br />40. SCC indicated that Pond 11 would be reducing flows from 21.33 cfs to 2.74 cfs, and <br />~~ therefore implied that the performance of the ex~stmg road culvert downstream from the <br />outlet of Pond 11 would not be compromised. The reduction in flow suggested may be <br />Tl D realized. SCC needs to provide information to demonstrate that the existing culvert will <br />handle any increases in flow generated by mining activity. <br />. 43. a. SCC indicated that supporting calculations for weighted curve numbers used in the <br />~, culvert calculations would be included in Attachment 13-8. The information was <br />provided on Table 20-I-1 of Tab 20. Please include this table in Attachment 13-8. <br />SCC also noted that culvert YA-6 had been sized to convey a 25-year event. If <br />a'~'the culvert size is now based on more conservative assumptions, why has the size <br />gone from 2-72" culverts to 2-60" culverts? <br />A review of the design inputs for all of the Road A culverts indicates that SCC <br />assumed an entrance loss coefficient of .5, which implies the culvert inlets will <br />„have headwalls and/or wingwalls. If SCC does not intend to employ these types <br />of structures, the proposed diameter of culverts YA-1, YA-7, and YA-8 will not <br />be adequate for the predicted flows. <br />~ b. The sizes of YB-4, YB-5, YB-6, YB-7, and YB-8 culverts may still need to be <br />revised after the watersheds are remodelled using a curve number of 94 for <br />disturbed areas (see comments 38 and 39 above). Please reevaluate these designs <br />after remodelling of the Pond ]0 watershed is complete. <br />qt, 44. SCC's response, that rip rap will be placed against the Road A fill, is acceptable. Please <br />incorporate the plan in the permit application package. <br />45. SCC's proposal for the Road A and "dirt road" intersection is likely acceptable. We <br />originally requested that SCC include any plans for an intersection in the permit <br />ew~ applicatton Package. This was not provided. Please include details of the plan m the <br />permit apphcation package. <br />STIP i°~ CDMG had also inquired as to whether SCC had consulted with the owner of this dirt <br />l~~ °~ i`¢^"`~ r'road. SCC did not respond. Please inform us as to whether the owner was contacted, <br />and if so, what resulted from this contact. <br />~ti 46. CDMG currently reviewing. <br />Tab ]5 <br />~ 49. SCC's monitoring plan for YTC32 and YTC33 is acceptable. SCC should be advised, <br />however, that the Division will not likely approve a technical revision which eliminates <br />monitoring of the Trout Creek Sandstone Aquifer, because the requirement for <br />monitoring the aquifer is intended to verify the operator's prediction of no impact or <br />minimal impact to the aquifer. Without monitoring data, this prediction cannot be <br />verified. <br />~~~~--~ 51.6 16SCC indicated that an application for water rights, to be used for dust suppression, has <br />been submitted. Please provide CDMG with documentation of its approval as soon as <br />it is available. <br />(,Q~ 53. Response provided by SCC on 3/30/95, DMG still reviewing. <br />