2013-09-27_REVISION - M1979094HR ‎(3)‎

• Permit No: M1979094HR
• IBM Index Class Name: Revision
• Doc Date: 9/27/2013
• Doc Name: AM01 Drainage Design
• From: Cotter Corp
• To: DRMS
• Type & Sequence: AM1
• Email Name: DMC
• Email Name: TC1
• Media Type: D
• Archive: No

JD -7 Mine - Drainage Design Plan
TABLE OF CONTENTS
1. INTRODUCTION ..................................................................................................... ............................... 1
1.1 Purpose ................................................................................................... ............................... 1
1.2 Overview - Runoff Areas and Routing ................................................... ............................... 1
1.3 List of Abbreviations .............................................................................. ............................... 3
2. DESIGN CRITERIA & METHODOLOGY ............................................................. ............................... 6
2.1 Design Storms ........................................................................................ ............................... 6
2.2 Runoff Estimates .................................................................................... ............................... 6
2.2.1
Volume ....................................................................................... ..............................6
Sub - Basins and Stormwater Routing on the JD -7 Mine Site ............... ...............................
2.2.2
Peak Discharge .......................................................................... ............................... 7
2.2.3
Computational Methods ............................................................ ............................... 9
4.4
2.2.3.1 Spreadsheet Simulation ................................................ ............................... 9
29
2.2.3.2 NRCS WinTR- 55 .......................................................... ..............................9
4.4.1 Pit Diversion Ditch — West ...................................................... ...............................
2.2.3.3 Regression Analysis ................................................... ...............................
10
4.4.2 Pit Diversion Ditch — East ....................................................... ...............................
2.2.3.4 HydroCAD ................................................................. ...............................
12
2.3 Structure Design ................................................................................... ...............................
12
2.3.1
Channel Capacity .................................................................... ...............................
12
2.3.2
Channel Stability ..................................................................... ...............................
13
2.3.3
Culverts ................................................................................... ...............................
15
2.3.4
Retention Ponds and Spillways ............................................... ...............................
15
2.3.5
Riprap / Granular Bedding / Gravel Mulch ............................. ...............................
15
3. HYDROLOGIC CHARACTERISTICS OF SITE SOILS ...................................... ............................... 17
4. STORMWATER ROUTING (CURRENT CONDITION) ..................................... ............................... 20
4.1
Sub - Basins Contributing Stormwater to Diversion Structures and Valley Floor ................
20
4.2
Sub - Basins and Stormwater Routing on the JD -7 Mine Site ............... ...............................
23
4.3
Sub - Basins Receiving Stormwater Downstream of the JD -7 Mine Site .............................
29
4.4
Reach Definition ................................................................................... ...............................
29
4.4.1 Pit Diversion Ditch — West ...................................................... ...............................
32
4.4.2 Pit Diversion Ditch — East ....................................................... ...............................
33
4.4.3 Open Pit Waste Rock Pile Diversion ...................................... ...............................
33
4.4.4 Stormwater Collection Ditches for the Underground - waste -rock Pile ...................
34
4.5
Storage Structures ................................................................................. ...............................
34
4.5.1 Existing Stormwater and Sediment Retention Ponds .............. ...............................
35
4.5.2 Upstream Storage Ponds ( USPs) ............................................. ...............................
36
4.6
Model Implementation of Stormwater Routing ................................... ...............................
37
4.7
Transmission Losses, Channel Infiltration ........................................... ...............................
41
5. MODEL RESULTS (CURRENT CONDITION) .................................................... ............................... 42
5.1 Runoff Results — Peak Flow and Total Volume ................................... ............................... 42
5.2 Peak Flow Regression Analysis ........................................................... ............................... 46
4149A.130926 Whetstone Associates