1987-12-01_PERMIT FILE - C1981017 ‎(103)‎

• Permit No: C1981017
• IBM Index Class Name: PERMIT FILE
• Doc Date: 12/1/1987
• Doc Name: Rock Tunnel Project
• Section_Exhibit Name: Chapter II Appendix II-B-3 ‎(Part 1 of 2)‎
• Media Type: D
• Archive: No

F
The final slope , not exceeding 2 (H) l (V) , should be
strictly maintained. Terraces should be included if present in
the original design. The surface of final slopes should be com-
pacted to prevent erosion.
The construction of the outer shell of the pile should be
performed under continuous supervision of an experienced engineer
of Mid-Continent's staff. Periodically, the compaction of the
outer shell should be verified by in situ density measurement
using the sand cone method .
The surface of the pile should be vegetated as specified in
the Permit Application .
5. 2 F,OCK TUNNEL DISPOSAL FACILITIY
The rock tunnel waste was designed to be deposited in a
facility with outer slopes of 2 (H) : 1 (V) , with two intermediate
berms', 10 feet wide. The maximum height of the facility was 50
feet. The reasons for the intermediate benches are not clear.
T;_y apparently are not required for stability purposes as in-
dicated by the high factor of safety, estimated by all stability
analyses. There appears to be no reason to include these benches
(terraces) because of erosion control , as the slopes are rela-
tively very low. The original design recommended to place the
waste systematically in lifts and to eliminate end-dumping. The
thickness of individual lifts is not to exceed 12 inches and com-
paction by the placing equipment were recommended for the outer
shell of the pile.
No specific construction and compaction methods were recom-
mended for the inner part of the waste pile , except that the
thickness of lifts do not exceed 24 inches was recommended .
The original design of the rock tunnel waste disposal
facility does not distinguish the stability conditions of
temporary and final slopes. In our opinion, the difference be-
tween temporary and permanent slopes is important. There is no
reason to maintain slopes to 2 (H) : 1 (V) or flatter on the tem-
porary slopes. Temporary slopes are well stable at slopes equal
to the angle of repose of the waste, or some 30 to 35 degrees.
Our inspection and testing shows that the waste has been
deposited in horizontal lifts, as specifiec, and it was compacted
to an acceptable degree. The only exceptions are locations where
high moisture content of the fill , probably prompted by recent
snowfall , results in less satisfactory compaction. In view of the
good quality of the rockfill and the extremely conservative
20
GEaHYDQO CONSULTING_INC_