PERMFILE66486

• Permit No: C1981020A
• IBM Index Class Name: Permit File
• Doc Date: 5/13/2002
• Section_Exhibit Name: Volume 6 APPENDIX As TO Cs
• Media Type: D
• Archive: Yes

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REFUSE DISPOSAL AREA - DITCH SIZING CALCULATIONS
• I. BACKGROUND INFORMATION AND ASSUMPTIONS
ALL DITCHES AND DIVERSIONS DIRECTLY EFFECTED BY THE REFUSE PILE
MUST BE DESIGNED TO SAFELY PASS THE FLOW OF A 100 YEAR - 24 HOUR
STORM.
The refuse disposal area is designed so that the bulk of the
Flow in all Four stages of construction will be directed towards
the north collector ditch. In the early phases of the project.
the north ditch will convey the drainage around the pile to an
existing stream channel that will direct the water to the
sediment pond.
Since phase IV of the refuse pile is the largest, the drainage
channels will be designed and constructed to safely convey the
quantities of water from the 100 year storm for that design.
The total area drained by the ditches in Phase 4 of the project
is 30 acres but only about 4 acres will be drained by the south
ditch. To ensure that adequate capacity exists for the north
ditch, it will be designed to handle runoff from the entire 30
acres. The south ditch will be designed to handle the runoff
from the 4 acres that can drain into it.
• 11. PEAK FLOW CALCULATIONS
A. SOUTH COLLECTOR DITCH
1. From Figure S-7 in "Peak Flows in Colorado" P100 = 2.4"
2. For Natural Areas CN = 80 Refuse Pile CN = 85
3. Schematic summarizes the Flow into the channel.
Area l Area 2 Area 3
(1.00 ac) (0.54 ac) (0.37 ac)
Segment 1 Segment 2
------------------------------------------------Sediment Pond
length = 1750' length = 320'
Slope = 7.14% Slope = 15.49.
Undisturbed Undisturbed
Area 4 Area 5
(0.97 ac) (1.42 ac)
4. Area 1 = 1.00 ac Slope = 50% Slope adjustment factor = 1.17
Hyd. length = 520' Equivalent Area = 4.57 ac CN = 85
Runoff = 1.10" Peak Discharge = 4.8 CFS/inch of runoff
Equivalent Discharge = 1.10 X 4.8 X 1.17 = 6.18 CFS
Actual Discharge = 6.18 X 1.00 / 4.57 = 1.35 CFS
. Q100 = 1.35 cfs
2/16/89