GENERAL39591

• Permit No: M1994117
• IBM Index Class Name: General Documents
• Doc Date: 3/27/1995
• Doc Name: PERMIT APPICATION ADEQUACY REVIEW GOLD HILL MILL FN M-94-117
• From: DMG
• To: COM INC
• Media Type: D
• Archive: No

Gold Hill Mill 10 March 27. 1995
Pertinent operating parameters (those with an environmental
protection function) will become an enforceable part of the permit.
If the upstream face of any dam raises are not going to be lined,
phreatic surface controls for the impoundment would have to be
implemented, e.g., an enforceable set-back from the embankment crest
and the free water pond. The set-back distance would be designed
based upon testing to determine the permeability of the tailing and
modelling to predict the configuration of the phreatic surface that
would develop. Piezometers would have to be installed in the tails
to verify the phreatic surface develops as predicted. COM, Inc. may
wish to install piezometers in the tailing regardless, in order to
avoid the need for cone penetrometer testing for foundation analysis
of any subsequent dam raises. Please address this issue.
(g) If the upstream faces of dam raises are proposed not to be
lined, filter compatibility between the embankment material and the
impounded tailing would have to be demonstrated.
29. Please describe any monitoring instrumentation that will be installed
at the impoundment, and propose a frequency for reading the instrument and
for reporting the readings to the Division. The Division believes that
such instrumentation should include:
(a) Piezometers within the tails to verify any stability analysis
assumptions regarding phreatic surface, to determine degree of
saturation - and thus suitability of tailing as a dam raise
foundation, and to verify that any required free water pond set-back
is sufficient to adequately suppress the phreatic surface within the
tailing.
(b) Movement monuments would have to be installed and monitored on
upstream raises to track settlement.
(c) Pore pressures in the tailing may have to be monitored during
and after construction of upstream embankment raises.
30. Please describe how the decant lines will be dealt with at the time
of reclamation. It is likely that these lines will be grouted closed.
Please include a cost to grout or otherwise decommission the decant lines
in your reclamation cost estimate.
31. Please incorporate a cost to properly abandon the monitoring wells
into your reclamation cost estimate, also, include a cost for the Division
to conduct 4 quarters of the required groundwater monitoring in the event
of permit revocation and bond forfeiture.
32. Include a cost in your bond estimate to seal, safeguard and prevent
access to the Time Mine and the Hazel A adit, also include a cost to
demolish and dispose of the Left Hand Creek pump-house, and a cost to
remove and dispose of the pipeline from Left Hand Creek to the Time Mine.