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Section 4 <br />St. Jude Mine <br />S = potential maximum retention after runoff begins (in) <br />S is related to the soil and cover conditions of the watershed through the Curve <br />Number (CN). CN has a range of 0 to 100, and S is related to CN by: <br />S _ 1000 _ 10 <br />CN <br />According to the US Department of Agriculture (USDA) TR 55 report (USDA 1986), <br />the CN for bare soil of hydrologic soil group of "D" is 94. For P equal to 3.0 inches and <br />CN equal to 94, S equals 0.64 and Q equals 2.35 inches. Therefore, CDM used 2.35 <br />inches as the design runoff for the berm design calculation. <br />The total runoff volume was divided by available catchment area within the surface <br />facilities area to calculate the minimum required berm elevation of Basin 3. The <br />calculated minimum berm elevation is 1.5 feet, which includes 1-foot of freeboard. An <br />existing berm encloses Basin 3. However, CDM recommends increasing the height of <br />the existing berm, where it is less than 1.5-feet high, to the calculated minimum <br />elevation. CDM also recommends connecting any breached areas along the berm. <br />Details for this calculation are included in Appendix B. <br />The total runoff volume of Basin 4 was calculated to evaluate the sizing for the <br />proposed catchment basin. Assuming that the proposed catchment basin is 40 feet <br />wide and 150 feet long with 1.5:1 (H:V) bank slope, the minimum required depth of <br />the catchment basin is approximately 3.0 feet. Therefore, CDM recommends <br />modifying the existing catchment basin to a depth of 4.0 feet, which includes 1-foot of <br />freeboard, a width of 40 feet, and a length of 150 feet, to contain the 100-year, 24-hour <br />storm event (refer to Exhibits C-1 and C-2). Details for this calculation are included in <br />Appendix B. In addition, the existing berm should be extended to contain the 100- <br />year, 24-hour event within the Basin 4 area (refer to Exhibit C-1). <br />The total runoff volume of Basin 5 was also calculated to evaluate the sizing for the <br />proposed catchment basin. Assuming that the proposed catchment basin is 30 feet <br />wide and 100 feet long with 1.5:1 (H:V) bank slope, the minimum required depth of <br />the catchment basin is approximately 3.0 feet. Therefore, CDM recommends <br />modifying the existing catchment basin to a depth of 4.0 feet, which includes 1-foot of <br />freeboard, a width of 30 feet, and a length of 100 feet, to contain the 100-year, 24-hour <br />storm event (refer to Exhibits C-1 and C-2). Details for this calculation are included in <br />Appendix B. In addition, the existing berm should be extended to contain the <br />100-year, 24-hour event within the Basin 5 area (refer to Exhibit C-1). <br />4.5 Conclusions and Recommendations <br />CDM proposed additional control structures to route offsite surface flow around the <br />surface mine area and contain the 100-year, 24-hr storm event within the onsite berms <br />and catchment. CDM recommends the following for St. Jude Mine storm water <br />drainage control: <br /> <br />4-4 <br />0:164986 - DenisonlTask Order 1 - Sunday Mines Drainage Study\Reporffinal Reporffinal Sunday Mines Drainage Report_052208.dx