2020-06-16_PERMIT FILE - M2020007 ‎(7)‎

• Permit No: M2020007
• IBM Index Class Name: Permit File
• Doc Date: 6/16/2020
• Doc Name: Adequacy Review Response #2
• From: Environment, Inc.
• To: DRMS
• Email Name: ECS
• Media Type: D
• Archive: No

I
Environment, Inc. Page 5
Adequacy Response#2 June 11, 2020
M-2020-007
this proposal, Phase 1A will be mined and used as a settling pond, and Phase 3 will
be totally stripped and used as the processing plant area, stockpile areas and
office/scale house area for the foreseeable future. Phase 1 will be the primary
mining area initially and no disturbance will occur in Phases 2 or 2A until the bond
can be reevaluated to allow LGE to move into one or both of the new Phases. LGE
will evaluate the bond prior to opening a new stage and adjust the bond if needed
to fit the next phase of mining and reclamation.
The Reclamation activities and bond calculation page shown at the end of Exhibit L
- Reclamation Cost is a recap of the areas needing reclamation as described above.
The first table (blue shaded area) has the various volumes or acreages needing the
reclamation activity list across the top'of the table for each Phase shown in the
left column. The Reservoir armoring has the total length that would be armored
but the calculation uses 1,000 feet since the armoring will be done in increments of
1,000 feet as reclamation progresses. The in-progress activities are those that
will take place as mining progresses. Items like resoiling stripped area, cut/fill
grading on the working face, and the sectional placement of the armoring material.
The yellow area covers the estimated cost for doing the reclamation on the areas
presented in the blue section.
EXHIBIT S - Permanent Man-Made Structures(Rule 6.4.19):
Geotechnical Stability Submittal — DRMS has reviewed the provided Slope Stability Analysis.
DRMS agrees that the pit slopes should be characterized as Critical Features for the reasons
given. However, the Division does not agree that utilizing back-calculated strength parameters
and slope failure data from a site located one mile south of the proposed permit qualifies as
multiple site-specific strength measurements, and therefore the more conservative FoS values
of 1.5 for static conditions and 1.3 for seismic conditions from the DRMS guidance should be
utilized. There also do not appear to be any loads applied to the slope for any topsoil or
overburden stockpiles that are depicted and will be placed adjacent to the excavations.
DRMS notes that the static, and draw-down Fo&provided seem to easily exceed the required
value of 1.5, however the seismic FoS barely exceeds 1.15, even without stockpile loading,
indicating that liquefaction may be a concern at this site. No information was provided regarding
how the seismic FoS was generated, so the Division cannot evaluate the parameters used.
At this time DRMS cannot accept the Stability Analysis provided. Please modify the analysis to
address the issues noted above and/or modify the proposed mining and reclamation plans as
needed to demonstrate that the proposed configuration provides adequate protection for
adjacent structures and long term stability.
Please see comment under"Additional Information:" below regarding providing structure
damage agreements to all structure owners within 200' of the site.
Attached is a response and additional information prepared by Deere & Ault to
address the Divisions concerns.