PERMFILE66655

• Permit No: C1981010
• IBM Index Class Name: Permit File
• Doc Date: 12/11/2001
• Doc Name: EAST FLUME GULCH HYDROLOGIC MODEL
• Section_Exhibit Name: APPENDIX Q SECTION XXXIV
• Media Type: D
• Archive: No

2. Slope Stability
The :slope stability for the East Flume Pond Embankment Dam wa
dimensic•nal slope stability program SLOPE/VV ®(Version 2.41). The
the Bishop's Method to determine the factor of safety for a circular fai
during a search routine for the critical surface. To address concerns re!
embankment dam after the pond was filled and the water level in the d
steady state, the slope was analyzed with the water level at the spillwa
above the tce of the embankment). The water level through the dam ur
estimated using Casagrande's Tangent Method (see attached calculatic
available information, can be used to conservatively estimate the heigl
steady-state seepage exits the toe of the dam. Utilizing the above ment
estimated line of seepage though the dam; the stability of the embanks
the groundwater level downstream from the embankment at the grounc
embankment cross-section incorporating upstream slopes of approxim
downstream slopes of approximately 3H:1 V was analyzed.
Soil strength parameters utilized are shown in Table 1.
3. Results
a~m~yccd with the two-
iLOPE/W model utilizes
tre surface that is found
trding the stability of the
m had reached a peak
(approximately 7.2 feet
ler these conditions was
t sheet), which, with the
at which the line of
med soils data and the
:nt was calculated with
surface. The as-built
rely 2H:1V, and
Through modeling it was determined that the embankment has a tactor of safety greater than
1.3 for the analyzed modes of failure.
The SLOPE/W stability analysis is attached. The factor of safety resulting from this analysis
is 1.68. ~
4. Conclusions
Utilizing the available information to model the East Flume Embankment Dam resulted in a
factor of safety of 1.68 for the downstream slope of the embankment. These analyses were based
on average strength parameters obtained from indicated tests, and conservative seepage
conditions. Therefore, the East Flume Embankment will be stable (under static conditions) as
long as construction practices used were consistent with those detailedin the approved permit
document.
5. References are attached.
As always, should you have any questions please contact Tom Leidichor me at [phone].
Best Regards,
Montgorr~ry Watso
i
onald outgo e
Associate Engineer
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Thomas E Leidich PE
Supervising Engrneer
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