PERMFILE108040

• Permit No: C1981019
• IBM Index Class Name: Permit File
• Doc Date: 12/11/2001
• Doc Name: Sections 10 - 16
• Section_Exhibit Name: Exhibit 12 Experimental Part 3
• Media Type: D
• Archive: No

Donald A. Crane
Page 4
"3. Reconstructing the existing fill in accordance with current federal •
regulations will not significantly influence the stability of the
spoil pile.
"4. In our opinion, the underground workings are not a significant
influence on the stability of the spoil pile." (Page 1 of
Contractor's Report.)
OSM finds that the "as built" pile does not comply caith all the requirements
of the regulations of Sections 715.15, 816.71, and 816.72 of Title 30, Code ~:f
Federal Regulations but that the pile does comply with static factor of safely
requirement of Paragraph 817.72(a) (i.e., 1.5). The applicant has not made a
demonstration of durability of the fill material. Therefore, Section 817.;4
of Title 30 does not apply.
Noncompliance is principally related to the fact that no subdrainage system
was employed, that surface drainage has not been diverted away from the top of
;-ti. the fill, that the lifts were in e:ccess of 50 feet, and that the distances
' between terraces are in excess of 50 feet and that the terraces are wider than
20 feet.*
The effect of the lack of diversions and a subdrainage system has been
indirectly analyzed by [he Contractor's use of theoretical zones of saturation
in the stability analysis. That is, the analyses have taken into account the
Contractor's best estimate of the effect of surface water seepage into the
pile. The Contractor states (page 17), "In our opinion, the only probable •
water table condition is that represented by water table condition No. 4."
OSM has no information to refute this conclusion. Post-construction
monitoring should be required to further the accuracy of the assumption.
Noncompliance with respect to the lack of a subdrainage system is not now
considered critical but_if water had~been diverted away and a subdrainage i
system_installed,_the pile would likely be more stable.
The other non-compliance issues related to items that are addressed in an all
encompassing manner by the Contractor's report. These Issues are the size of
lifts and the terraces. The total fill, as constructed, is shown in the
Contractor's report, to be slightly more stable Chan if the Eill were
constructed to meet OSi4 requirements assuming placement of additional fill on
the lv:3h face in the OSM design. However, the difference is principally due
to the Contractor's assumption that a pile built to meet OSM's requirements
would have more material placed higher above and upstream of the current apex
of the fill face. This difference may be examined by comparing Figures 4 and
5 of the Contractor's report. OSM assumes that a pile built to meet OSM's -~~
requirements will have equal overall stability since OSP1's regulations allow
utilizing a grade lower than lv:3h above the 6,900 foot evaluation just as
ColoWyo has proposed. The only difference would be that the OSM design would
require a terrace at 50 foot elevations or three additional terraces as
opposed to none shown on the ColoWyo design.
The ColoWyo design of individual-terraces differs From the OSM design in that
ColoWyo's terraces are 30 feet wide and 100 feet apart in elevation while
terraces built to meet OSM's requirements* would be 20 feet or less wide and
*OSM assumes for this analysis, a combination of applicable regulations --
namely Sections 816.71(h), 816.102(b), and 816.72(e) and (g).