Draft Environmental Impact Statement for Roca Honda Mine

Chapter 3. Affected Environment and Environmental Consequences
The flow pattern also influences water quality, with the best quality water typically closer to the
recharge zone at the aquifer outcrops, and poorer quality water downdip in the aquifers (and also
in the interleaved aquitards). For example, figure 75 in Stone et al. (1983) indicates that water in
the Morrison Formation over a large portion of southern McKinley County (north of the outcrop)
is generally of excellent quality with respect to specific conductance, a measure of the dissolved
minerals content.
Where there is a demand for water, the limited availability of surface water results in widespread
use of groundwater in the San Juan Basin for all purposes.
Hydrogeology of the Permit Area and Surroundings
Introduction
The Roca Honda permit area is located in the southeastern part of the San Juan structural basin,
within the southeast part of the Ambrosia Lake uranium subdistrict. This subdistrict was the site
of uranium mining and associated mine dewatering activities from the 1960s through the 1980s,
and the impacts from such mining are one basis for prediction of impacts at Roca Honda. The
permit area lies within the Bluewater Underground Water Basin as extended by the New Mexico
Office of the State Engineer (OSE) on May 14, 1976. The area discussed below includes the 3section
permit area and surrounding lands for several miles in all directions from the permit area
boundaries.
Sources of Information
RHR compiled groundwater quality data and hydraulic parameter estimates from the Mt. Taylor
mine and various other uranium mines west of the Roca Honda permit area in the Ambrosia Lake
subdistrict (NMEI, 1974; GMRC, 1979a; and Kelley et al., 1980; see compilation in Section 9 of
the Baseline Data Report). The Mt. Taylor Mine is approximately 3 miles southeast of the Roca
Honda permit area; it formerly was operated by Gulf Mineral Resources Company (GMRC) and
others and now is owned by Rio Grande Resources Corporation (RGRC). This mine was
dewatered during the 1970s and early 1980s. Much information on this mine is not publically
available. Although far from the permit area, RHR considered information on the groundwater
quality and hydraulic characteristics of the Westwater Canyon Member of the Morrison
Formation that were considered in site licensing in the Crownpoint and Church Rock areas (HRI,
1988 and 1991; and USNRC, 1997).
Historical data on water quality and aquifer hydraulic characteristics specific to the permit area
and immediate surroundings are sparse. Consequently, RHR compiled the relevant published and
unpublished information near the permit area. This effort included an inventory of wells
previously identified in published and unpublished reports as being present near the Roca Honda
permit area. The inventory of 149 records includes location, completion date, well depth,
producing formation, measured water levels, and availability of chemical data for each well. The
wells were field checked. Selected wells from the inventory were sampled. In addition, RHR
drilled three monitoring wells within Section 16 of the permit area in 2007 and subsequently
sampled them. RHR incorporated a subset of the selected inventory wells and all three monitoring
wells into an ongoing water quality sampling program, termed the Regional Groundwater
Sampling Program.
DEIS for Roca Honda Mine, Cibola National Forest 129