2016-08-08_PERMIT FILE - C1981019A ‎(8)‎

• Permit No: C1981019A
• IBM Index Class Name: Permit File
• Doc Date: 8/8/2016
• Doc Name: Table of Contents & Intro
• Section_Exhibit Name: Volume 18 Exhibit 7 Item 23
• Media Type: D
• Archive: Yes

height, vertical distance between spillways, etc.) can be considered accurate. The input pond geometry
parameters are shown on the SEDCAD4 printouts and summarized in Table 5.
TABLE 5
POND GEOMETRY
LCX -IN (SUMP)
LCX -DS POND
Roadside Impoundment
Elevation (ft)
Area
(ac)
Elevation (ft)
Area
(ac)
Elevation (ft)
Area
(ac)
6705
1.22
6621
0.13
7200
1.19
6710
1.68
6625
0.16
7205
1.71
6716
2.28
6630
0.65
7210
2.33
6720
2.72
6635
1.21
7215
3.04
6726
3.42
6640
2.00
7220
3.83
6730
3.92
6642
2.61
7225
7.45
6737
4.91
7230
9.50
7232
10.77
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. Design
for this impoundment is provide in Part C of Exhibit 7, Item 23.
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. Design for this impoundment is
provide in Part B of Exhibit 7, Item 23.
The Roadside Impoundment is an intermittent impoundment formed by the large temporary spoil pile,
which will be emptied by pumping as necessary However, the runoff form a storm as large a 25 year
event only raises the pool 8.7 feet . Design for this impoundment is provide in Part G of Exhibit 7, Item
23.
5.0 RIPRAP SIZING
Unless specifica',ly stated otherwise, riprap sizes were determined using the SEDCAD 4.0 subroutine `or
designing riprap lined channels utilizing the OSM/Simons Method. SEDCAD also provides another
Exh. 7-23-6 Revision Date: 9/23/11
Revision No.: PR -03