2009-05-12_PERMIT FILE - C1980005 ‎(2)‎

• Permit No: C1980005
• IBM Index Class Name: Permit File
• Doc Date: 5/12/2009
• Section_Exhibit Name: Tab 12 Operation Plan
• Media Type: D
• Archive: No

• installed as neoe_ssaiy to reduce the exit velocity. Zhe
minim im width will be the width of the Natural downstream
channel. ~e riprap will be sized in the field by Peabody's
project engineer based on the "as-built" slope of the culvert
and final configuration of the exit channel slope area. 4he
sizing shall be based on the Federal Highway Administration's
HF7C No. 11 "Use of Riprap for Bank Protec,~tion" or other
standard methods. All pipes will have a m;n;nrt~m cover of 12
inches. Culverts aid drainage ditches will be maintained
periodically to prevent aocwmilation of debris on the culverts
inlets arrl outlets.
The general design pr'ooedtses used in the design of culverts
is contained in P.pperdix 12-2.
Table 12-6 contains an inventory of existing and proposed
culverts at the Seneca II Mine. All existing culverts are
• adequate. Figures 12-6 arri 12-7 shwa typical installation of
culverts. Other applicable methods include the use of charts
developed by the Federal Highway ndm;n;ctration, published in
Hydrologic F7xjineering Circular HDC-5 (FHA, 1980), arri
Hydrologic Design Series HDS-3 (FHA, 1980).
Charts published in HDC-10 (FHA, 1978) are also used; however,
exit velocities must then be determined by other methods.
Headwater conditions are typically a~miTMx9 by using HF7C-5
inlet control Homographs. To be conservative and to allow
far adequate freeboard, Peabody usually uses "projecting"
oorditions.
i+lost of the culverts have free outfalls, inlet control
assumptions can be verified by the "Pipe Flow Charts" in
HDS-3. If flow in the culvert has a free surface, entrance
control exists, and exit velocity can be approximated by using
. the greater of normal or critical velocity determined by the
12-37g Revised 12/10/92