PERMFILE139435

• Permit No: C1981019
• IBM Index Class Name: Permit File
• Doc Date: 6/14/1985
• From: MLRD
• To: COLOWYO COAL CO
• Section_Exhibit Name: Gulch A sed pond
• Media Type: D
• Archive: No

~_ .TABLE 1
GULCH A POND DATA
1981 Prmit 1981 Response 1985 Technical
Application Volume 8 P.evision

Watershed ?.rea: ~
Pre-t~tini ~g 419 ac. 419 ac. 419 ac.
Post-tdining Disturbed 650 ac. 650 ac. 650 ac.
Past-Mining-undisturbed 17 ac. 17 ac. 17 ac.
Post-Mining Total 667 ac. 667 ac. 667 ac.
Precipitation (10 Yr, 24 Hr.) 1.8 in. 1,8 in. 1.8 in.
Runoff CPJ 67 67 67
ZO Yr. Runoff Depth .055 in. .055 in. .055 in.
10 Yr. Runoff Volume 3.06 ac. ft. 3,06 ac. ft. 3.06 ac. ft.
3 Yr, Sediment Yield 0.58 ac. ft. 1,17 ac. ft. 1.17 ac. ft.
• 3 Yr. Sediment and 10 Yr. P.unoff 3.64 ac. ft. 4,23 ac. ft. 4.23 ac. ft.
Volume Below Emergency Spillway 5.01 ac. ft. 5.01 ac. ft. 5.01 ac. ft.
Volw~~e Below Principal Spillway 1.26 ac. ft. 3.76 ac. ft.(a)
Elevations:
Im~ert 6611 6c_1 6613.8
•
Principal Spill~,vay 6614 ^cs5 6619
Emergency Spillway 6620 - E620 6620
_' 'Top Of Dam ~ 6622 6cZ2 6622
- Bottom of Dam ~ 6611 boil 6611
Principal Spillway:
Type 12" CMP 12" CMP 12" CMP
Entrance Restriction 4" cap 4" cap 4" cap
10 Yr. Water Surface Elevation 6617,9 6617.9 6618.6 (b)
,: 10 Yr. Fl;od Detention Time 23.0 23.0 Contained
Emergency Spillway:
25 Yr. Runoff Volume 11,1 ac. ft. 11.1 ac. ft. 11.1 ac. ft.
Spillway Outflow 25 cfs 25 cfs 25 cfs (c)
Width 15 ft. 15 ft. 15 ft.
25 Yr. Water Surface Elevation
I 6620.42 6620.42 6620.42
(a) Provides for containment of 10 Yr. 24 Hr. event and 600 3 Yr. sediment.
(b) Includes 60e 3 Yr. sediment.
(c) Note that peak flov+ is estimated at 24.03 cfs.