2011-06-06_REVISION - M1984014 ‎(7)‎

• Permit No: M1984014
• IBM Index Class Name: Revision
• Doc Date: 6/6/2011
• Doc Name: Amendment App. ‎(AM-01)‎ Attachment A Drainage Plan, Rule 6.5 & Spill Prevention
• From: Cotter Corporation
• To: DRMS
• Type & Sequence: AM1
• Email Name: GRM
• Media Type: D
• Archive: No

JD-8 Mine - Drainage Design Plan i
0 TABLE OF CONTENTS
1. INTRODUCTION .................................................................................................................................... 1
2. EXISTING DRAINAGE CONDITIONS ................................................................................................. 1
2.1 Runoff Areas ......................................................................................................................... 1
2.2 Design Criteria and Design Storms ....................................................................................... 5
2.3 Peak Discharge Estimates for Mine Runoff Areas ................................................................ 5
2.4 Existing Stormwater Retention and Routing Capacity .......................................................... 7
3. OPERATIONAL AND POST-MINING DRAINAGE CONDITIONS ................................................... 7
3.1 Runoff Areas ......................................................................................................................... 8
3.2 Stormwater Retention and Routing Capacity ........................................................................ 9
4. REFERENCES ....................................................................................................................................... 11
LIST OF TABLES
Table 1. Upland Non-Contributing Drainage Areas ....................................................................................... 1
Table 2. Drainage Basin Areas at the JD-8 Mine under Current Conditions ................................................ 3
• Table 3. Recurrence Interval for Design Storms ............................................................................................ 5
Table 4. Runoff from Site Basins for 10-yr 24-hour Storm Calculated Using SCS method for Design
Storms ........................................................................................................................................... 6
Table 5. Runoff from Site Basins for 100-yr 24-hour Storm Calculated Using SCS method for Design
Storms ........................................................................................................................................... 6
Table 6. Planned Dimensions for the Expanded East Stormwater Retention Pond ....................................... 7
Table 7. Planned Dimensions for the West Stormwater Retention Pond ....................................................... 7
Table 8. Calculated Runoff from the 10-year 24-hour and 100-year 24-hour Storms based on Planned Final
Topography ................................................................................................................................... 8
Table 9. Preliminary Dimensions for the Operational and Post-Mining Stormwater Retention Pond........... 9
LIST OF FIGURES
Figure 1. Upland Non-Contributing Drainage Areas ..................................................................................... 2
Figure 2. Stormwater Drainage Areas at the JD-8 Mine ................................................................................ 4
Figure 3. Post-Mining Stormwater Routing Plan ......................................................................................... 10
LIST OF PHOTOS
Photo 1. Photo of Berm and Cutoff Ditch on Access Road Southeast of JD-8 Mine Site
Photo 2. Eastern Portion of Waste Rock Pile Showing Constructed Catchment and Perimeter Berms for
Drainage Control
• Photo 3. Western Portion of Waste Rock Pile Showing Former Rivulet and Small Gully that was Mitigated
by Repairing the Crest Berm
4122A.110601 Whetstone Associates 4