PERMFILE41923

• Permit No: C1982057A
• IBM Index Class Name: Permit File
• Doc Date: 10/4/2002
• Doc Name: Drainage and Sediment Control Plan
• Section_Exhibit Name: Tab 13 Attachment 13-5B
• Media Type: D
• Archive: Yes

September 2002 Senem IfIY/SonJh E.xpanrion * Drainage anrlSerliment P/an ~ 6
6.0 POST MINING CHANNELS
All post mining channels were designed to safely pass the peak discharge from the 70-year, 24hour .
event. The post mining channels dimensions were determined using Mannings Equation for open
channel flow. All channels will be grassed lined except for the steeper portions of PM-1 and PM-3
which will require 6" xiprap. All channel design inputs and results can be found in Appendix 3, Post
Mining Channel Designs. The design results axe shown on Figure 1, Post Mining Channel Designs.
TABLE 5
SENECA II-W (SOUTH EXPANSION)
SEDIMENTATION POND SUMMARY
Pond 015 Pond 016 Pond 017
WATERSHED AREA lacres):
Disturbed ~ 39.3 ~ 154.0 ~ 80.3
Undisturbed ~ 367.4 I 230.6 ~ 878.3
Total Area 406.7 384.8 958.6
POND PARAMETERS:
Bottom Elevation ~ 7378.0 ~ 7447.0 ~ 7375.0
Principal Spillway Invett Elevation ~ 7390.0 ~ 7463.0 ~ 7391.9
Emergency Spillway Invert Elevation ~ 7391.8 ~ 7467.0 ~ 7393.4
Top of Embankment ~ 7394.0 ~ 7470.0 ~ 7395,0
Storage Volume Below Principal Spillway lac-ftl ~ 3.62 ~ 9.62 ~ 8.12
Storage Volume Below Emergency Spillway lac-frl ~ 4.71 ~ 13.62 ~ 9.74
Principal Spillway Parameters:
Type ~ Drop Inlet ~ Drop Inlet ~ Drop Inlet
Riser Diameter lint ~ 18.0 ~ 24.0 ~ 36
Riser Height Ift1 ~ 5.0 ~ 5.0 ~ 4.9 -
Barrel Diameter lint ~ 18.0 ~ 24.0 ~ 36
Emergency Spillway Parameters:
Type ~ Trapezoidal ~ Trapezoidal I Trapezoidal
Bottom Width Iftl ~ 10.0 ~ 20.0 ~ 20
Length (ftl ~ 60.0 ~ 36.0 ~ 24.6
Side Slopes H:1 V Ift) 2/5 3.0 3.0
HYDROLOGIC/HYDRAULIC PARAMETERS:
10-Year, 24-Hour Storm Event:
Precipitation (in) ~ 1 .7 ~ 1 .7 ~ 1 .7
Runoff Volume lac-ftl ~ 3.65 ~ 11.62 ~ 6.14
Principal Spillway Peak Discharge Icfsl ~ 11 .1 ~ 27.8 ~ 47.4
Emergency Spillway Peak Discharge fcfsl ~ 0.0 ~ 0.0 ~ 0.0
Peak Surface Water Stage Elevation Iftl ~ 7391.7 ~ 7466.4 ~ 7393.4
25-Near, 24-Hour Storm Event:
Precipitation lin) ~ 2.1 ~ 2.1 I 2.1
Runoff Volume lac-ftl ~ 5.80 I 16.08
' 9.46
Principal Spillway Peak Discharge Ictsl ~ 0.0 ~ 0.0 48.6
Emergency Spillway Peak Discharge (cfsl ~ 28.4 ~ 122.7 ~ 6.7
Peak Surface Water Stage Elevation Iftl ~ 7392.95 I 7468.7 I 7393.9
Pond Freeboard Iftl 1 .05 1.3 1.1
SEDIMENT LOADING PARAMETERS:
Storm Predicted Peak Settleable Concentration Iml/II ~ 0.00 I 0.01 ~ 0.00
Predicted Annual Sediment Loading lac-ftl ~ 1.21 ~ 5.42 ~ 2.56
Available Sediment Storage Volume lac-ft) ~ 2.58 ~ 8.30 I 8.12
Maximum Sediment Storage Elevation fitl ~ 7388.0 ~ 7461.5 ~ 7391.9
Predicted Number of Storage Years 2.1 1.5 3.2
TR-41 Revised 09102

f 1
LJ
MIVH * 16SS Union Bou&varrl, Suite 460 * LnkemooA, ColoraAo 80228 * [phone]