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l <br />4. Manning's n values are input by the software, rather than the user, unless one utilizes the non- <br />erodible channel utility. The SEDCAD+ software appears to give inconsistent Manning's n values <br />between the watershed or peak Oow routines and those generated by the utilities. Greystone has no <br />control over the SEDCAD+ output of this parameter. MCC will utilize the designs shown in the <br />ditch runs for D3-1, D3-2B, D3-3 and D3-lA. <br />5. The unit hydrograph response shape for watershed 15Awas modified to Medium (M) in the pond run, <br />but as you observed, i[ did no[ modify the peak flow calculations. <br />6. The culvert utility is SEDCAD+ is slightly more conservative than the culvert nomograph used to set <br />culvert sizes in MCC's Mine Water Control Plan. To make the permit document consistent, MCC <br />would like to utilize the culverts shown by the culvert Homographs. At times, MCC will install larger <br />culverts. The minimum sizes for culverts C3-lA, C3-1 and C3-3 will be 15", 18" and 12" respectively. <br />Current installation sizes are 24", 24", and 24", respectively. MCC does not intend to utilize 6" <br />culverts as it is a poor engineering practice and it also results in high maintenance costs. Table 44 <br />has been modified to show that the minimum size for C3-3 and C3-4 will be 12" culverts. <br />7. Table 44 has been corrected to show that D3-2 and D3-2A are shotaete-lined ditches. <br />SEPTEMBER 16 AND 27, 1994 SUBMITTALS <br />1. A revised watershed 2 showing a discharge of 2.68 cfs is attached for your review. <br />2. Watershed 2B is being provided for your review. MCC has confirmed that the channel lining on Ditch <br />Dl-SA is shotcrete, and Table 43 has been modified accordingly. <br />3. Figure 15 in Volume 1 of the MCC permit document shows a maximum discharge of 184 gpm or 0.4 <br />cfs (184 gpm /448.8 gpm/cfs). Previous estimates, utilized in the MB-1 run utilized 200 gpm or 0.45 <br />cfs. As the SEDCAD+ model only shows baseflow to the tenth of a cfs, that run shows 0.5 cfs. <br />4. Copies of the watershed runs are attached, with the exception of the 15 series. The values for all the <br />15 watersheds may be pulled out of the drainage system run (or MB-3, except (or watershed 15C. <br />Minor changes of Table 43 were made to correspond with small variations which resulted during re- <br />compiling. Watershed SD may be found in a run entitled Watersheds SA, SB, SC, and SD. Please <br />note that watershed 9BB is in the MB-1 section rather than the MB-2R section. <br />5. The watershed models are enclosed. <br />6. Watersheds 6D and 12 have been eliminated due to re-configurations of the 6 series and the 12 series <br />of watersheds. You may delete them from Exhibit 66. Please remove the watershed run of 15AA <br />from your Exhibit per question 2 of the MB-3 section. It is an artifact of the previous runs. <br />7. You are wrrect in moving watersheds 9BB, 9CC, and 11C to the MB-1 section, in accordance with <br />Table 43. <br />8. Please delete the single run of watershed 14A and retain the 13 series, per Tabte 43. <br />9. The entire run for Watershed 19B is provided for your files. <br />10. Please delete the ditch runs for D1-38, D2-3C and D2-l0A from your Exhibit 66. <br />11. The requested ditch designs are provided (or your perusal. Please note that the D2R-2 (+) and the <br />D2R-3 designs are all currently designed for the 100-year storm. <br />