PERMFILE117384

• Permit No: C1982057
• IBM Index Class Name: Permit File
• Doc Date: 12/11/2001
• Doc Name: GENERAL HYDROLOGY DESIGN METHODS
• Section_Exhibit Name: TAB 13 ATTACHMENT 13-1
• Media Type: D
• Archive: No

• Introduction
For each sedimentation structure, diversion, culvert, and haul road ditch, the
relationship between rainfall and runoff was determined through a hydrologic analysis of
the tributary drainage area. The following design methodology was used in the design of
these structures.
DESIGN METHODOLOGY
General Hydrology Design
The precipitation runoff (peak flow and volume) was estimated using the Soil Conservation
Service (SCS) triangular hydrograph techniques as described in Design of Small Dams (U.S.
Dept. of Interior, 1977). Computations necessary for this runoff estimating technique
have been computerized by various individuals and agencies.
SEDIMOT II was developed by Research Specialist Bruce N. Wilson, Professor Billy J.
Barfield, and Assistant Professor Ian D. Moore at the Department of Agricultural
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version of the SEDIMOT II computer program. This program was used to estimate runoff peak
flow and volume which are necessary in the design of the ponds, culverts, and ditches. A
copy of the computer program's input and output file information has been included in
Addend ums i and 2!
The input consists of precipitation amount (inches), watershed area (acres), time of
concentration (hours), and runoff curve number (CN) and other pertinent watershed and
structur a-related data.
Precipitation and Storm Type. The precipitation amounts at the Seneca II-W Mine area for
the design storm durations were obtained from the NDAA Precipitation Frequency Atlas
Precipitation - Frequency Atlas of the Western States - Volume 2, Colorado, 1973 and are
listed below.

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