PERMFILE50679

• Permit No: C1980004A
• IBM Index Class Name: Permit File
• Doc Date: 5/13/2002
• Section_Exhibit Name: APPENDICES K - P
• Media Type: D
• Archive: Yes

McClane Creek Temporary biversion
• During the midterm review the McClane Canyon Mine permit conducted in
1996, it was determined that McClane Creek had been diverted. The road and mine
facilities were constructed under the authority of a USGS Exploration Permit prior to
the enactment of SMCRA. Review of photography from 1977 shows a newly
constructed road along side of a well vegetated channel. The diversion apparently
occurred prior to mine site construction. None the less, GVC committed to submit
designs for the channel; as well as, to reclaim the original channel after mining.
Since the diversion of the channel occurred over 20 years ago, and no designs for
the channel are known to exist, the channel was surveyed to determine the profile
and channel geometry.
The survey revealed that the diversion is approximately 550 feet long with an
overall slope of 5.9 °~o. The slope of the channel varies from nearly flat to about
25~Jo .The steeper segments are where large boulders or rocky stretches make up
the channel bottom. A profile of the channel, plan view of the location and
calculations of peak flow velocities are shown on the following pages.
The channel was inspected by DMG and GVC during the summer of 1996.
The inspection revealed that the channel was steeply incised into the valley floor and
passed over large boulders and rock outcrop in some areas. These areas of the
channel provide a series of armored steps within the channel bottom. It appeared
that the channel bottom is stable. The channel bottom varies in width from about
three feet wide to over six feet wide. The sides of the diversion vary from nearly
• vertical to approximately 2 to 1 horizontal to vertical.
The calculations contained on the following pages show that the flow from the
2 year 24 hour event, required under 4.05.3 (2) ,will be contained within the existing
channel. Some of the steeper reaches of the diversion exhibit velocities that are
potentially erosive. Notably, those portions of the diversion are those which have
large boulders or rock outcrop armoring the bottom have developed slopes up to
27~/o for short segments.
Reconstruction of this diversion to meet the current standards would be fairly
large project. The depth of the diversion near East Salt Creek is about ten feet. A
channel with 2H : 1V side slopes and a five foot wide channel bottom would be
about 45 feet wide. This amount of additional disturbance seems excessive for a
channel that appears to be stable. Grand Valley proposes to add four wooden
gabions to the channel to ensure that the channel will remain stable. The location
of these gabions is shown on the plan view on Page M • 6. A diagram of gabion
construction is shown on Page M • 8. Using gabions to help armor the channel will
be less disruptive than excavating the channel and installing rip -rap. The gabions
will provide a solid place in the channel bottom to limit any further erosion which
could occur. Grand Valley will also monitor the channel for evidence of erosion. The
results of the survey will be submitted to DMG along with the annual hydrology
report. If monitoring of the channel reveals that unacceptable erosion is occurring,
corrective measures will be approved and implemented.
• When the mine site is reclaimed, the flow from McClane Creek will be returned
to the original channel . Once the main channel has been reclaimed, the diversion
channel will be Claimed. The area will be revegetated with the greasewood
shrubland seed mix.
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