1988-04-11_PERMIT FILE - C1981008A ‎(20)‎

• Permit No: C1981008A
• IBM Index Class Name: PERMIT FILE
• Doc Date: 4/11/1988
• Doc Name: Facilities
• Section_Exhibit Name: Tab 13
• Media Type: D
• Archive: Yes

culvert and final configuration of the exit channel slope area. The sizing shall be based
on the Federal Highway Administration's HEC No. 11 "Use of Riprap for Bank Protection" or
other standard methods. All pipes will have a minimum cover of 12 inches. Culverts and
drainage ditches will be maintained periodically to prevent accumulation of debris on the
culverts inlets and outlets.
The following is an outline of the general design procedures used in the design of
culverts:
1. Identify the need for a structure from topographic maps, and a visit to the
site;
2. Determine the size and hydrology of the watershed in question (Exhibits 13-4 and
13-5);
3. Perform SEDIMOT II computer run to determine the peak runoff from a 10-year,
24-hour precipitation event. Attachment I contains the typical inputs used for
these SEDIMOT II calculations.
4. Using the peak flow rate from SEDIMOT II, the tailwater depth downstream is
calculated using the Manning's Equation. The Manning's Equation calculations
are generally performed on a personal computer utilizing a program written by
Dodson and Associates entitled TRAP. Another program written by Dodson and
Associates entitled PIPE is then used to perform the culvert design analysis.
Basically this program determines the capacity of the culvert using two
procedures, inlet control and outlet control. The procedure resulting in the
higher headwater is the value that the culvert design is based. Attachment J
contains a complete description of both the PIPE and TRAP programs.
Table 13-3 contains an inventory of existing and proposed culverts at the Nucla Mine. All
existing culverts are adequate. Figure 13-4 and Figure 13-5 show typical installation of
culverts. Other applicable methods include the use of charts developed by the Federal
Highway Administration, published in Hydrologic Engineering Circular HEC-5 (FHA, 1980),
and Hydrologic Design Series HDS-3 (FHA, 1980).
Charts published in HEC-10 (FHA, 1978) are also used; however, exit velocities must then
be determined by other methods. Headwater conditions are typically examined by using
HEC-5 inlet control nomographs. To be conservative and to allow for adequate freeboard,
Peabody usually uses "projecting" conditions.
13-18 Revised 04/11/88