2009-09-25_PERMIT FILE - M2009076 ‎(41)‎

• Permit No: M2009076
• IBM Index Class Name: PERMIT FILE
• Doc Date: 9/25/2009
• Doc Name: Big Five Tunnel Discharge
• From: Venture Resources
• To: DRMS
• Media Type: D
• Archive: No

Construction and operation ofthe ARGO Tunnel Water Treatment Facility, design
and construction of the Virginia Canyon Ground Water Collection and
Conveyance system pursuant to the OU 3 ROD, and coordination with other
construction projects in the area have provided a cost effective alternative for
including the Big Five Tunnel discharge in the individual control strategy for the
ARGO Tunnel.
5. The Five Year Review Report for Clear Creek/Central City Superfund Site,
CDPHE September 2004 included a recommendation to make a final decision for
the Big Five Tunnel discharge.
DESCRIPTION OF SIGNIFICANT DIFFERENCES
As previously stated, the primary purpose of the remedy selected in the OU 3 ROD was to prevent
degradation ofdownstream surface water quality and aquatic life resources through the treatment of
the ARGO Tunnel discharge, the metals contaminated flows exiting Virginia Canyon, and other
specific historic mining impacts. Originally, the Big Five Tunnel discharge was not considered for
treatment under the OU 3 selected remedy because computer modeling conducted prior to the OU 3
ROD suggested there was minimal impact. Actual sampling data collected since the OU 3 ROD,
however, demonstrate that there is a significant impact from the Big Five 'flannel discharge. Based
. upon this new information and discussions with stakeholders and the local community, the agencies
decided that it was warranted to consider the collection and the conveyance of the Big Five discharge
as part of the final remedy for the SITE.
The OU 1 ROD specified passive treatment or a combination of active and passive treatment for the
Big Five Tunnel discharge. Passive treatment was pilot tested, but was unable to treat the discharge
sufficiently to meet regulatory requirements. The OU 3 ROD, which superseded the OU 1 ROD,
used an interim waiver of ARARs for the Big Five Tunnel discharge. The OU 3 ROD will be
modified with the Big Five Project, the scope of which includes:
a collection of the Big Five Tunnel discharge at the tunnel portal;
a conveyance of the discharge to the ARGO Water Treatment Facility for treatment to the
discharge limits specified in the discharge control mechanism for the treatment plant;
a draining the pond outside of the Big Five Mine Tunnel;
o placing waste rock adjacent to the pond back in the pond and additional material to form a
stable base;
a capping waste rock and sediments in place in the pond with a suitable cover graded to drain
precipitation away from the pond, and maintaining adequate vegetative cover on the cap; and
a operations and maintenance of the collection and conveyance system and pond closure and
cap.
Treatment of the Big Five discharge at the ARGO Plant is protective of human health and the
environment and will neutralize acidity and remove 99 percent of the metals from the discharge. The
treated discharge will meet the Clear Creek aquatic life standards and satisfy the ARARs related to
the discharge by incorporating it into the individual control strategy for the ARGO Tunnel. Since
this final action for the Big Five Tunnel discharge will meet ARARs, the interim waiver invoked in
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