Draft Environmental Impact Statement for Roca Honda Mine

Treated Water Discharge in an Alternative Location
Chapter 2. Alternatives, Including the Proposed Action
This alternative was the original proposed action at the time of scoping in December 2010, under
which the Roca Honda Mine would have discharged treated groundwater from the mine into an
unnamed arroyo on Section 16. It was eliminated because, according to expert opinion, its
potential impacts on water resources would be difficult to ascertain without lengthy, costly, and
possibly inconclusive investigation, and these effects could possibly be moderate to major, as
well as controversial.
This unnamed arroyo (figures 21 and 22) is characterized by ephemeral or intermittent flows (i.e.,
it is dry most of the time), and it is tributary to San Mateo Creek. Discharging up to 4,000 gpm of
treated water into the arroyo would have changed its flow regime from ephemeral to permanent
for the duration of the mine.
This alternative, in other respects identical to the current proposed action, was complicated by the
presence of legacy environmental effects from previous eras of uranium mining and milling in the
San Mateo Creek watershed. These legacy effects made evaluation of potential environmental
effects of the proposed Roca Honda Mine discharge much more difficult (Nelson, 2011).
Groundwater pumped from the mine would have been treated as necessary to meet an NPDES
permit prior to discharge into a tributary to San Mateo Creek. However, legacy mine water
discharges from historic uranium mining and milling operations are suspected of causing
contamination in sediments and alluvium in the San Mateo Creek watershed downstream of the
proposed Roca Honda Mine discharge. Discharge of treated water meeting NPDES standards
could potentially “rinse” these potential legacy contaminants from sediments and unconsolidated
alluvial sediments within the San Mateo Creek watershed, and transport these contaminants into
surface water or groundwater.
Figure 21. Arroyo originally intended to receive treated water from Roca
Honda Mine at approximate point of discharge
DEIS for Roca Honda Mine, Cibola National Forest 59