Draft Environmental Impact Statement for Roca Honda Mine

Chapter 3. Affected Environment and Environmental Consequences
Details on the chemistry of the material and of potential reactions are not known at this time and,
thus, it will be important for RHR to perform testing and to mix the materials with cement prior
to placement. EPA (1975, p. 2) reports that from other mines in the area, conventional
underground mining has caused deterioration of post-mine groundwater quality, most
dramatically from increased dissolved radium and uranium. Increased concentrations of dissolved
metals would also be expected, including arsenic, molybdenum, selenium, and vanadium. For EIS
purposes, the oversight of backfill by NMED—a State regulatory requirement—is expected to
ensure that there is no backfill using materials capable of having an adverse effect on
groundwater quality.
Mine shafts would be grouted during construction, but this is not expected to seal off waterflow
entirely. The shafts would not be backfilled, so that when dewatering ceases, the shaft would
provide a pathway for a small amount of water movement among aquifers, due both to the nature
of the grouting material and its physical breakdown over time. In general the flow would be
expected to be downward (e.g., Gallup to Dakota to Westwater), reflecting the predevelopment
regional gradient and residual drawdown effects. This minor component of the water budget is
not simulated in the Intera model. For the Westwater, the contribution of Dakota water would
degrade water quality; based on Kelly and others (1980), the most noticeable effect would be
increased sulfate.
Impacts of Surface Facilities and Operations
Impacts to groundwater are possible from: (a) seepage related to surface discharge of treated mine
water, (b) construction and operation of mine facilities at the land surface including stockpiles of
excavated materials, and (c) liquids and wastes used by or created by the mine that contain
hazardous constituents. Potential contaminants include especially radionuclides and heavy metals.
The mineralogy and geochemistry of the uranium deposits have not caused acid mine drainage
historically in the Grants Uranium Belt, and no mineralization at the RHR mine indicates that
conditions are different at this location.
The project is designed to eliminate all potentially significant seepage of impacted surface water
to groundwater. The measures to control groundwater pollution will be specifically regulated by
NMED through issuance (or denial) of a groundwater discharge permit for RHR. The NMED
permitting process began with RHR’s application for a permit in 2009, and has progressed
through numerous submittals by RHR to NMED at increasing levels of detail. That process will
ultimately require a public notice of a draft permit. One outcome of the process could be control
measures beyond what is now planned. Such further control or mitigation measures would result
in fewer impacts than those evaluated in the EIS.
The most important control now included in RHR’s plan is that water pumped from the mine,
along with water gathered from surface facilities, will be treated at the wastewater treatment plant
(WTP) with required removal of contaminants to safe levels (see brief discussion above under
surface water). Based on data from other mines, treatment will likely be required for selenium
and may be necessary for other substances, such as radionuclides.
Information now available indicates the WTP would have substantial capacity to deal effectively
with influent of variable quality; 8,000 gpm is the basis for equipment sizing although maximum
dewatering rates are estimated to be 4,500 gpm. Plant design includes one double-lined surge and
two double-lined treated water holding ponds to minimize the potential for discharge of untreated
DEIS for Roca Honda Mine, Cibola National Forest 177