Draft Environmental Impact Statement for Roca Honda Mine

Chapter 3. Affected Environment and Environmental Consequences
plan revision 1 describes an extensive storm water control infrastructure that is expected to keep
storm water and potential contaminants onsite. In the event of failure of one or more storm water
controls, there could be storm water with entrained pollutants released to the ephemeral arroyos
draining the site and potentially into San Mateo Creek, which is also ephemeral in this segment.
The effect of one or a small number of releases is not anticipated to be measurable in the
ephemeral stream system.
While the proposed action anticipates the permitted discharge of treated mine water to the natural
drainage system within the permit area, there is a potential for pipeline leaks that would cause the
release of untreated mine water to surrounding soil. Both the treated and untreated water would
be pumped via HDPE pipelines within the permit area. All water requiring treatment would be
conveyed to retention ponds where it will be piped to the mine water treatment facility. The
anticipated quality of the mine water flowing into the water treatment facility is shown in table
15. All treated water would be conveyed to private land outside the permit area. In the unlikely
event a leak occurred in any pipeline, a specifically designed leak proof 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. The water produced at each dewatering well
would be tested to establish its water quality and determine if treatment is necessary prior to
discharge. The effect on surface water quality is dependent upon the water quality of the untreated
and treated water.
The RHR mine site would also contain sanitary wastewater treatment facilities to treat wastewater
produced from toilets, sinks, showers, and laundry. The water would be collected in a series of
buried septic tanks which are designed to treat approximately 10,000 gallons per day (gpd). The
effluent from the tanks would be pumped to the water treatment facility and combined with mine
water for additional treatment as necessary. As with the untreated and treated wastewater, there is
potential for the septic tank effluent to enter the natural drainage system within the permit area,
therefore potentially affecting the water quality of a downstream surface water system.
During operations, runoff to the detention basins will not come in contact with the mine site but
would be monitored accordingly. The two detention basins would be sampled at the outlets after a
storm event, when practical, to provide background sediment and water quality data. Samples
would also be collected at predetermined locations below the operational areas in the arroyos.
Analyses will include major cations, major anions, other water quality parameters, and targeted
constituents for ephemeral, intermittent, and perennial receiving drainages.
Transportation of hazardous or toxic materials to and from the site has the potential to affect
surface water quality in the event of an accident that releases the materials near drainages. Trucks
hauling ore would be inspected and cleaned of any detritus materials at the washing station prior
to leaving the site. The amount of ore to be hauled offsite has not yet been established. The water
from the truck wash station would also be collected in a retention pond, reused/recirculated and
ultimately pumped to the water treatment facility.
Effects of Treated Water Discharge
The potential effects of disposing of treated water by land application include buildup of minerals
in the soil and groundwater impacts. The impact of this disposal practice occurs over a period of
time, so there is no significant effect over the short 18-year operational period of mining.
156 DEIS for Roca Honda Mine, Cibola National Forest