1993-04-15_REVISION - M1977378 ‎(3)‎

• Permit No: M1977378
• IBM Index Class Name: REVISION
• Doc Date: 4/15/1993
• Doc Name: List of Concerns
• From: DMG
• To: Sunnyside Gold Corp
• Type & Sequence: TR14
• Media Type: D
• Archive: No

term surface expressions of mine pool water that exceed the
actionable flow rate. The actionable flow rate will most likely be
defined by CDOH as the regulatory authority over surface discharges
in the State of Colorado. Sunnyside Gold must have contingency
plans in place to deal with such flows. Contingency plans could
include collection and treatment of contaminated flows, preventing
the flows from reaching the surface by grouting, additional
bulkhead installation or other means, or by drawing-down of the
mine water pool.
It is the Division's view that a plan to draw-down the mine water
pool must be in place in case unforseen difficulties are detected
while the workings are being flooded. Such a plan would include
maintaining the American Tunnel water treatment facilities in a
condition that could handle flows anticipated during draw-down, and
upgrading the bulkhead by-pass pipe and valve to handle a
controlled draw-down in the worst case. Such a plan would preclude
grouting of the by-pass pipe and the water pressure monitoring pipe
until a determination is made that no unforseen leakage of mine
pool water is taking place. Figure 9 of the March 12, 1993 Simon
Hydro-Search report indicates that the mine pool may continue to
rise for more than 20 years. As a result, the corrosion resistance
of piping used in the bulkheads must be sufficient to impound the
mine pool, with a high factor of safety, until such time as the
pipes can be grouted.
4. Construction Performance Plan
The Division will require that quality assurance and quality
control of the bulkhead installation be documented through a
combination of certifications by a professional engineer (PE) , and
point inspections by Division staff. Operations that will require
PE certification include:
(a) Bulkhead location preparation (scaling and washing) .
(b) Laying of the by-pass or diversion pipe (American Tunnel
only) .
(c) Construction of concrete forms and erection of re-bar
cages.
(d) Pumping of concrete and filling of forms as well as seven
and twenty-eight day compression tests for concrete strength.
(e) Low pressure grouting of the concrete-rock interface.
In addition, the operator must notify the Division at some
reasonable time prior to filling the forms so an inspection can be
made of the preparations leading up to the concrete pour.
The Division will also make every effort to schedule an inspection
of the proposed bulkhead locations prior to any decision on
technical revision TR-14, and will inspect the drainages in the
surrounding area discussed in item 2 of this letter once they are
accessible.
5. Monitoring and Reporting Plan
The baseline monitoring data described in item 2 of this letter
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