Draft Environmental Impact Statement for Roca Honda Mine

Chapter 2. Alternatives, Including the Proposed Action
The shaft would also be lined to reduce inflow of water from aquifers overlying the underground
mine after construction, and to prevent flow of water between aquifers.
During mine operations, mine depressurizing would be accomplished by drilling “long holes”
into the rock at the working faces of the mine to drain the formation. The water flowing into the
underground mine would be conveyed into underground sumps and would then be pumped out of
the mine to the surface through a vertical pipe located within the shaft. Therefore, all of the
depressurizing wells would be shut down after construction of the production shafts and initial
mine development in the Westwater Canyon Formation is complete.
RHR proposes to plug and abandon most depressurizing wells after shaft construction is
complete. However, some may be maintained as long term water quality monitoring wells. The
wells would be reclaimed in accordance with State requirements for wells constructed in artesian
aquifers.
Water Treatment Plant
Water pumped from the depressurizing wells may produce natural water quality that does not
meet numerical surface water discharge standards. Water quality from these wells would be
monitored to further develop baseline conditions for each aquifer. RHR proposes to treat water
produced from mine depressurization, as necessary, through construction of a water treatment
plant. Construction of this plant would be completed within 180 days (about 6 months) after
permit approval.
The Water Treatment Plant 60 percent Design Revision 1, as revised to address Agency
comments, was submitted in December 2011 (Lyntek, 2011). RHR prepared revision 1 in
response to NMED comments on the initial water treatment plant submittal, in support of the
discharge plan and MMD permit application. The water treatment facility would encompass
approximately 10 acres and would consist of the water treatment process building, an influent
surge pond, and two treated water holding ponds. The effluent flow rate is expected to be 2,500 to
4,500 gpm. The maximum design capacity of the treatment facility is 8,000 gpm, which adds
redundancy for most treatment units. Water generated from mine dewatering activities, water
collected from within the Roca Honda permit area in the retention ponds, and the effluent from
the sanitary wastewater treatment system would be treated onsite at the water treatment facility.
The water from the dewatering wells would be pumped to the water treatment plant in a network
of 18-inch high density polyethylene (HDPE) pipelines with fused joints. Water from dewatering
of the mine proper would be pumped to the water treatment plant in a separate 18-inch HDPE
pipeline. This would allow for different options for treatment within the treatment plant based on
the influent quality. These pipelines would be monitored for change in pressure utilizing pressure
gages throughout the system. In the unlikely event a leak occurred, a specially designed leakproof
saddle would be installed on the damaged area to seal the leak without a pump shutdown. A
redundant plan would involve a system of piping and valves to switch the flow of water from one
dewater pipeline to the other until the leaking portion of a line can be replaced. This system will
be designed as a part of the construction drawings (RHR, 2012).
The water produced from the mine dewatering wells (see the “Water Resources” section) would
be pumped to the water treatment facility for treatment prior to disposal. Water produced by the
mine would be gathered in a sump located within the mine itself to remove sand and grit. The
40 DEIS for Roca Honda Mine, Cibola National Forest