2010-12-17_REVISION - C1981019 ‎(122)‎

• Permit No: C1981019
• IBM Index Class Name: REVISION
• Doc Date: 12/17/2010
• Doc Name: Exhibit 7 Item 23 Erosion and Sedimentation Control Plan
• Type & Sequence: PR3
• Email Name: JRS
• Media Type: D
• Archive: No

i TABLE 5
POND GEOMETRY
LCX -IN (SUMP)
LCX -DS POND
Elevation (ft)
Area
(ac)
Elevation ft
Area
(ac)
6705
1.29
6625
0.13
6710
1.83
6630
0.61
6715
2.05
6635
1.21
6720
3.02
6640
2.04
6725
3.68
6642
2.54
6735
5.11
6645
3.39
6737
5.36
6646
3.81
6740
1 5.70
6650
1 5.69
4.0 POND CLASSIFICATIONS AND SPILLWAY EVALUATIONS
The site is located in a rural, agricultural area and meets Class A criteria for dams in the U.S. Department
of Agriculture, Soil Conservation Service Technical Release No. 60 (210- VI -TR60, October, 1985). All
proposed structures will be either constructed below existing grade or will have an above -grade storage
volume of 20 acre -feet or less, with a dam height of 20 feet or less (measured from the upstream toe to the
emergency spillway crest) and are therefore exempt from Mine Safety and Health Administration
regulations under 30 CFR § 77.216.
The proposed above -grade structures will not be designed or operated for the purpose of impounding
water above the natural surface of the ground other than flood detention and are therefore exempt under
Rule 17 of the State of Colorado, Rules and Regulations for Dam Safety and Dam Construction.
The Little Collom (LCX -D /S) Pond facility will provide adequate capacity to contain or treat the runoff or
inflow entering the pond as a result of 10 -year, 24 -hour precipitation event, provide a nonclogging
dewatering device or conduit spillway to remove water storage resulting from inflow, and an emergency
spillway design to safely pass the 25 -year, 24 -hour precipitation event. The Little Collom Sump (LCX -
IN in -pit sump) facility will be operated as an enclosed sump within the Little Collom X pit, and pumped
into LCX -DS for polishing as water quality and pond drawdown allows.
5.0 REFERENCES
Agricultural Handbook No. 703, "Predicting Soil Erosion by Water: A Guide to Conservation Planning
with the Revised Universal Soil Loss Equation (RUSLE) ", U.S. Department of Agriculture, Agricultural
Research Service, July 1996, 404 pp.
Barfield, Warner, & Haan (1981). "Applied Hydrology and Sedimentology for Disturbed Areas".
Oklahoma Technical Press, Stillwater, OK.
Haan, C.T., Barfield, B.J., and Hayes, J.C., 1994, 1981. "Design Hydrology and Sedimentology for Small
Catchments ". Academic Press — Harcourt Brace & Company, San Diego.
Schwab and Warner (1998). "SEDCAD4 Users Manual'. Civil Software Design. Lexington, KY.
Natural Resources Conservation Service (1986). "Urban Hydrology for Small Watersheds (TR -.SS) ". Soil
Conservation Service. Washington, DC.
Exh. 7 -23 -6 Revision Date: 12/15/10
Revision No.: PR -03