Draft Environmental Impact Statement for Roca Honda Mine

Best Management
Practices
Chapter 3. Affected Environment and Environmental Consequences
Effectiveness Assessment
Retention ponds Captures and stores potentially contaminated water from the mine site. Constructed
with sumps to collect solids for periodic removal and disposal. Requires treatment
prior to disposal. Used throughout the site.
Stockpile management
procedures and practices
Reduce or eliminate release of materials from stockpiles. Used in conjunction with
ditches and/or wattles throughout the site.
Wind erosion control Prevents or reduces erosion by the forces of wind. Water spray would be applied to
roads and small, temporary soil piles during construction activities. Topdressing and
revegetation would be applied to larger and/or inactive stockpiles.
RHR will be required to submit a notice of intent to comply with the Multi-Sector General Permit
(MSGP) for Storm Water Discharges Associated with Industrial Activity, Sector G2. The MSGP
specifies steps that facility operators must take, including storm water control measures to
minimize pollutants in storm water runoff and developing a SWPPP.
Effects on Streamflow
Untreated mine water discharge is not expected to reach any lakes, streams, springs, reservoirs,
riparian, or wetland areas. Treated mine water pumped from the proposed Roca Honda Mine and
dewatering wells will be discharged via a 20-inch diameter pipeline transporting water to private
land. A local rancher has sought to use the treated water for irrigation purposes. As mentioned
above, the discharge will occur on private property in the vicinity of Laguna Polvadera. At that
location the water will become available for reuse by others or may simply flow down the San
Lucas Arroyo as a permitted discharge. Appropriate permits from the OSE, U.S. Environmental
Protection Agency, and NMED Groundwater Quality Bureau shall be obtained. Conditions of
these permits will include monitoring of discharges to surface water.
RHR estimates that dewatering of the proposed Roca Honda Mine when both shafts are operating
will be a maximum of 8.9 cfs (8,000 gpm) of water, although a lower volume is considered more
likely. The estimate of an average mine water discharge rate of 4,000 gpm is based on experience
at previous uranium mines that dewatered the Westwater Canyon Member of the Morrison
Formation such as the Gulf Mt. Taylor Mine, Kerr McGee’s Ambrosia Lake Mines, and the Nose
Rock Mine. For example, Rio Grande Resources Company (RGRC 1994) discharged
groundwater at a rate of 5.6 to 11.1 cfs (2,500 to 5,000 gpm) from the Mt. Taylor mine when it
was in operation. RHR performed an aquifer test of the Westwater Canyon Member in order to
determine whether the hydrogeologic characteristics in the RHR permit area were similar to those
calculated for that geologic unit in the area of other mines for which discharge rates were known.
The results of that test indicated that the storage properties and transmissivity of the Westwater
Canyon Member are in the middle range of reported values, an indication that volumes of water
similar to those produced by earlier mines can be expected at the RHR mine. The test values were
also used to refine RHR’s groundwater flow model and estimate the volume of mine discharge.
Effects on Water Quality
There is the potential for storm water to transport sediment and potentially other pollutants
associated with an operating facility (e.g., petroleum products) downstream. The mine operations
DEIS for Roca Honda Mine, Cibola National Forest 155