Draft Environmental Impact Statement for Roca Honda Mine

Chapter 3. Affected Environment and Environmental Consequences
It is clear from the limited available data that compared to the high elevation volcanic springs,
Bridge Spring, South Bridge Spring, and 605 Spring have water that is slightly more basic, and
with higher levels of all constituents except potassium. Generally, water from high elevation
springs was of the calcium-sulfate bicarbonate type, and water from low elevation areas was of
the calcium bicarbonate type. The data are consistent with the fact that the springs near the permit
area have a source of water that is distinct from both El Rito and La Mosca Springs. The water in
the lower elevation springs probably has had a longer residence time within siltstones and
sandstones, whereas the source of La Mosca and El Rito Springs is probably water which entered
the Mt. Taylor volcanics as precipitation and moved quickly through the rocks.
Springs That Supply Acoma and Laguna Pueblos
Since before European settlement, the Rio San José has been the primary source of water supply
for Acoma and Laguna Pueblos. Risser (1982) quantified this supply as it existed prior to non-
Indian development, and considered the following sources: (1) Horace Springs and other
groundwater discharges within the pueblos; (2) the spring known as Ojo del Gallo; and (3)
surface supplies from Bluewater Creek and local runoff. In the scoping process, impacts to this
supply—and especially to Horace and related springs—received extensive attention.
Consequently, the components of the existing supply are discussed below as a foundation for
evaluating whether the Roca Honda project might affect any such supply. See figure 33 for
locations of features mentioned.
A portion of the Horace Springs discharge and all of that at Ojo del Gallo originates from the San
Andres Limestone-Glorieta Sandstone aquifer. This aquifer is Permian in age and, thus, lower in
the stratigraphic column than the formations discussed above with respect to the Roca Honda
permit area. In the permit area, the San Andres-Glorieta is separated from the Westwater Canyon
by the Chinle Formation, which is dominated by siltstones and mudstones, and which Hagan and
others (2001) consider to be a regional confining unit. Frenzel (1992, figure 4) indicates 1,000
feet or more thickness of the Chinle in the general area and (in figure 9 in Frenzel, 1992) a water
level that is probably below the pre-development Westwater Canyon level, but similar to or
higher than levels during times of mine dewatering..
On the northeastern flanks of the Zuni Mountains and in the Grants-Bluewater area, the San
Andres-Glorieta aquifer occurs at or near the land surface. It receives recharge in the mountains
and along Bluewater Creek. The groundwater in this unit generally flows east toward the Rio
Grande. Its flow is substantially impacted by faults and other structures, which in some places
force water toward the surface, and elsewhere put the aquifer so deep that it is unused. Near
Grants, the aquifer has been substantially developed using large capacity wells for municipal,
irrigation, industrial, and power plant supplies; irrigation also provides recharge to the aquifer.
Relatively recent basalt lava flows occur at the land surface between Grants and Acoma Pueblo
and are incised by Rio San José. Alluvium occupies the stream valley. Just west of the western
boundary of Acoma Pueblo, the basalt constricts the stream valley and the alluvium and causes
groundwater to surface at Horace Springs; there also may be faults at this location that impact
groundwater flow. A significant amount of groundwater passes underground along the stream
alluvium, and is discharged at springs (such as Anzac Springs) and as baseflow for several miles
downstream (shown as gaining reach on figure 41).
DEIS for Roca Honda Mine, Cibola National Forest 143