APPCOR13031

• Permit No: C1982057
• IBM Index Class Name: Application Correspondence
• Doc Date: 3/5/1985
• Doc Name: SENECA II W MINE FN C-82-057 PRELIMINARY ADEQUACY REVIEW
• From: MLRD
• To: PEABODY COAL CO
• Media Type: D
• Archive: No

Seneca II-W Prelim. Adequacy - 10 - March 5,
1985
10. Some justification of curve numbers used in the haul road culvert
designs should be presented. Within the mine site, a CN of 80 appears
low, but not unacceptable with justification. The tie-across haul road
culvert designs use a CN value of 88 which seems high.
11. The following culverts do not have enough minimum cover to ensure
ppassage of design flows without overtopping the haul roads based upon
HW/D values: MEI, HR-1, HR-3, HR-4, HR-5, HR-6, HR-10, HR-11.
12. According to Rule 4.03.1(4)(e)(i), culverts with an end area greater
than 35 square feet must be designed to pass the 20-year, 24-hour storm
event. The cut-off is a culvert of approximately 80 inches in
diamater. Culvert HR-6 and the combined culverts at HR-9 fall into
this category and should be redesigned.
13. On page 12-26, all culverts were listed as being type 3 - projecting,
however, in the culvert designs presented in Appendices 12-1 and 12-2,
all three types, headwall, mitered to conform to slope, and projecting
were used. Please clarify.
14. Rule 2.05.3(4)(a)(i)(E) as referenced on page 7-198h requires a time
schedule for submitting a detailed plan for these channels. Peabody
should submit a time schedule for these design submittals.
15. The value for channel slope for post-mining stream channel DP-5 appears
incorrect based upon Exhibit 12-6LP.
16. The channel design should be checked using Manning's equation to ensure
the design assumptions used. In the case of DP-5, actual depth of flow
is less than 0.81 ft. and velocities are higher than 6.0 fps.
17. From Appendix 12-3, the formula for "p" for a "v" ditch with 2H:1V side
slopes should be p=z(4d2+d2)0.5 or p=4.47d and then R=0.447d.
There appears to be something missing since the formula for "d" as it
appears later on the page is correct.
18. Several of the haul road culverts have velocities greater than 6 fps.
This is allowable without riprapping as long as Peabody commits to to
other measures to slow flows and prevent erosion (i.e., check dams).
If peabody plans to use riprap, designs should be submitted. For
excessive velocities (i.e., HR-10), riprap will be necessary.
Topsoil Performance Standards - Rule 4.06
1. Please refer to comments under 2.04.0 and 2.05.4(2)(d) above.