Draft Environmental Impact Statement for Roca Honda Mine

Chapter 3. Affected Environment and Environmental Consequences
Regional Hydrogeology
Sources of Information
The project area is near the southern edge of the San Juan structural basin and has a hydrogeology
consistent with other areas of the basin. The San Juan structural basin has been extensively
studied, because the area contains deposits of recoverable coal, uranium, and hydrocarbons, as
well as valuable groundwater resources. Studies by the U.S. Geological Survey (USGS), the New
Mexico Bureau of Mines and Mineral Resources, the New Mexico State Engineer, and others
have described area aquifers, compiled and analyzed groundwater quality data, and developed
estimates of aquifer properties (Brod and Stone, 1981; Frenzel and Lyford, 1982; Stone et al.,
1983; Craigg et al., 1989; Dam et al., 1990; Dam, 1995; and Craigg, 2001).
As part of the Regional Aquifer System Analysis program, the USGS developed a steady-state
multi-aquifer groundwater flow model of the San Juan basin (Kernodle, 1996). No copy of the
actual model code still exists. However both DBSA (2001, on behalf of Acoma Pueblo) and Intera
(2011, on behalf of RHR) have used reconstructions and modifications of the model to predict
impacts of pumping in the region. Another USGS model is Frenzel (1992), which simulates
impacts from pumping in the San Andres-Glorieta aquifer, including effects on Horace Springs.
DBSA (2001) has also modified and used this model for the same purpose.
Aquifers
Figure 38 is a cross-section of the San Juan Basin which shows the major aquifers and confining
beds (rocks that restrict water movement). Sandstones and limestones are the primary aquifers
within the southeastern part of the San Juan Basin; the confining beds are typically shales. The
aquifers include the following, from shallowest to deepest:
• Cretaceous Formations including the Menefee; Point Lookout Sandstone; Crevasse
Canyon Formation, and Gallup Sandstone; and the Dakota Sandstone.
• The Jurassic Westwater Canyon Member of the Morrison Formation, and the deeper
Entrada sandstone.
• Permian Glorieta Sandstone and San Andres Limestone.
The line of this cross-section lies considerably to the west of the Roca Honda permit area. On the
figure, the location north of Crownpoint where the Mesaverde group outcrops is where the
geologic sequence most closely resembles the Roca Honda permit area, although some
thicknesses of units in the permit area are different than shown on figure 38. See Stone et al.,
1983 for an expanded discussion of the stratigraphy shown in figure 38. A version of figure 38
that contains information on water quality and aquifer transmissivity is published in Wilson and
Holland (1979).
Groundwater can occur in other geologic settings. For example, within topographic valleys,
Quaternary alluvium can be a local aquifer. Also, while low permeability confining beds separate
the major aquifers on a regional scale, in specific areas they can yield small quantities of water to
wells from localized sandstone lenses. Formations older than the San Andres Limestone may
contain groundwater; however, their depths generally preclude groundwater exploration or
development except along the margins of the basin where they are close to the surface.
124 DEIS for Roca Honda Mine, Cibola National Forest