2010-11-19_PERMIT FILE - C1980007 ‎(36)‎

• Permit No: C1980007
• IBM Index Class Name: Permit File
• Doc Date: 11/19/2010
• Doc Name: Surface Facilities Area and Water Tank Site
• Section_Exhibit Name: Exhibit 66 SAE Lone Pine Water Tank
• Media Type: D
• Archive: No

Location
i
SEDCAD + Identifier
Acres
the area between the southeast
1 -2 -1 -2
0.30
quadrant of the development waste
125 (M)
75 (F)
pile and the interceptor ditch D -1
i
the north sloping top of the devel-
i 1 -3 -1 -1
I 0.17
opment waste pile
i
the sideslopes of the north facing
1 -3 -1 -2
0.38
portions of the waste development
pile
4.2 Curve Number (CN)
Curve numbers reflect the runoff potential of an area (a value of 100 represents an impervious area where 100%
of the water would run off), and is a function of soil type (a "C" used in this analysis) and the land use. For this
analysis, the CN value is (reference the SEDCAD+ guide):
1) For undisturbed portions of the watershed, overland flow: 63 (for Arid and Semiarid Rangelands, Oak,
fair cover).
2) For the pile slopes, overland flow: 91 (no vegetation or cover).
4.3 Hydrograph Response Shape and Overland Flow Lengths
is Hydrograph response shapes reflect the rapidity with which water runs off a watershed, rated in SEDCAD+ as fast,
medium, or slow. A slow response s. wo44UPjaeespond to a forested area or an area with a lot of obstructions,
while a fast response shape would correspond to an unvegetated or poorly protected area. These ratings are for
overland flow. Once overland flow is surpassed, a fast rating is assigned.
Lengths of overland flow (sheet and rill drainage) are direct input parameters in SEDCAD+ for sedimentology
analyses, and have an indirect influence on other parameters, such as LUC. The maximum permissible lengths of
overland flow used within this analysis, with corresponding hydrograph response shape parameters, are presented
in the following table.
4.3 -1 Lengths (in feet) of Overland Flow and Hydrograph Response Shapes (Slow, Medium, or Fast)
Vegetative Cover
Slopes less than or equal to 25 %
Slopes over 25 %
Oak Brush, etc.
225(S)
175 (M)
Bare, Unprotected Soil
125 (M)
75 (F)
4.4 Control Practice Factor
The SEDCAD+ Model considers the sediment loss from an area with a given cover and conservation practice, as
compared to that of a field in continuous fallow, by introduction of a Control Practice (CP) Factor. The CP is a
function of Canopy Cover and Percent Ground Cover. The CPs used in this analysis were selected from the
SEDCAD+ guidelines.
(West Elk Lone Pine Gulch Development Waste Pile SAE, 12 October 1995, Page 5 of ')