2010-04-26_PERMIT FILE - C1980007A ‎(3)‎

• Permit No: C1980007A
• IBM Index Class Name: Permit File
• Doc Date: 4/26/2010
• Doc Name: Refuse Pile Expansion East
• Section_Exhibit Name: Exhibit 82 Refuse Pile Expansion East
• Media Type: D
• Archive: Yes

Table 2 summarizes model results. Figures 2 -5 (static) and 2 -6 (seismic) illustrate the design and
provide modeling results for Design Case A, while Figures 2 -7 (static) and 2 -8 (seismic) illustrate the
design and provide modeling results for Design Case B.
In addition to Cases A and B described above, the proposed RPE East slope, which includes benches
and haul roads, was analyzed for stability. This geometry is referred to as the Permit Design, and the
slope geometry is considered intermediate between Cases A and B. The static factors of safety for the
90% and 50% exceedence values for the ESSA runs were 1.68 and 2.28, respectively. The seismic
factors of safety for the 90% and 50% exceedence values for the ESSA runs were 1.46 and 1.94,
respectively. Figures 2 -9 and 2 -10 show the 90% exceedence stability model outputs for the static
and seismic cases, respectively.
2.2.3.3 Geotechnical Design
Actual refuse to be placed in the proposed RPE East is not available to sample at this time; therefore,
undrained conditions need to be considered in the analysis, and could control the design depending
on actual refuse characteristics. It is proposed that a sampling, testing and monitoring plan, as
presented in Appendix C, will be implemented as part of RPE East operations to verify the refuse
characteristics and monitor refuse pile conditions.
An initial evaluation will be conducted over the first two years of CPP operations when the refuse
pile is very small and there is no danger of instability and will be performed as described in the
sampling, testing and monitoring plan. Test results will be compared to a minimum failure envelope
for Design Cases A and B as shown on Figures 2 -11 and 2 -12, respectively, and a stability analysis
will be performed using test values from the actual refuse material. These minimum failure
envelopes were back - calculated such that the factors of safety for the given geometry in each case
were adequate as discussed in Section 2.2.3.2 above.
While the modeling results above demonstrate that the RPE East as presented is feasible with the
given design cases, the minimum failure envelopes described above will be used to evaluate the
actual refuse that is placed in the refuse pile. To conduct this evaluation, test results of refuse from
the CPP will be compared to the minimum values provided in Table 2. If friction angle and cohesion
values of the material exceed the values provided for Cases A and B, the RPE East is anticipated to
be constructed to the permitted pile design shown on the drawings with provisions for control of
Revised March 19, 2010
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PA\Mpls \06 CO \26 \06261003 MCC Refuse Pile Site Review & Permit \WorkFiles\Permit Application \Text \2010- 04- 19_RPE East Permit Application.doc 7