PERMFILE130754

• Permit No: C1980005
• IBM Index Class Name: Permit File
• Doc Date: 12/11/2001
• Section_Exhibit Name: TAB 15 PR1
• Media Type: D
• Archive: No

Mr. Tom Wainwright -2- September 25, 1984
The proposed mining in the Wolf Creek permit revision area will generate •
excess spoi] as demonstrated in Table 12. Calculations indicate that between
1,855,000 yd3 to 2,380,000 yd3 of excess spoil will be generated. The
applicant uses a swell factor of 19.8 based on actual pre-mining and
post-mining volumes using a computer program called STOCK. The excess spoil
volumes are generated from 148.58 acre area depicted in Figure 12-1x. A fill
has been designed for compliance with Rule 4.09.i(3).
PCC proposes to open a box cut adjacent to an ephemeral drainage. Excess
spoil is proposed to be disposed of in this drainage. The applicant has
submitted slope stability analyses for this fill area on pages 12-13 through
12-17. Cross-sections and diagrams are submitted on Exhibits 12-ESI, 12-ES2
and 12-E53. Computer data are submitted in Appendices of Tab 12. Slake
durability analyses are submitted in Appendix 12-5.
The applicant applied the appropriate slope stability analyses using two
computer programs, the SWASE program (Sliding Wedge Analysis of Sidehill
Embankments) and the REA14E program (Rotational Equilibrium Analyses of
Multilayered Embankments). Computations indicate that the minimum factor of
safety is 1.6 static and 1.27 seismic, which are within the requirements for
long-term stability.
An underdrain and a lateral drain to drain the seeps and springs within the
drainage are proposed. Drainage designs are found in Table 12 and are based
on measured and projected flow rates. PCC states that the drain will be •
constructed of natural sandstone rock no larger than 5 feet in diameter and
that no more than 10 percent of the rock will be less than 12 inches in size..
The applicant further states that the drains will be free of coal, clay or
shale.
The toe of the underdrain is designed to discharge into the coal seam. The
applicant states that during wet periods the coal seam may not absorb all of
the underdrain flow. Ground water levels within the indrain will rise and then
flow into the existing spoils. This may result in base saturation of the
existing spoils. The stability of the existing spoils is not addressed in the
application, therefore any discharge which may result in base saturation
should be alleviated or addressed in terms of geotechnical stability. MLRD
field observations indicate that there is an existing enclosed impoundment,
which exhibits swampiness located where the drainage ends. This impoundment
is located at the toe of the proposed fill. Therefore, the following
stipulation is required:
Stipulation l:
WITHIN 90 DAYS OF 7HE PERMIT APPROUAL THE APPLICANT SHALL SUBMIT AN
ADEQUATE DESIGN FOR A SURFACE DISCHARGING DRAIN TO BE CONSTftUCTEU AT
THE TOE OF THE PROPOSED FILL. SHOULD THIS SURFACE DRAIN FLOIJ INTO AN
EXISTING SURFACE DRAINAGE SYSTEM, THE APPLICANT SHALL DISCUSS THE
EFFECT ADDITIONAL FLOW WILL HAVE ON THE HYDROLOGIC SYSTEM.
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