Draft Environmental Impact Statement for Roca Honda Mine

Chapter 3. Affected Environment and Environmental Consequences
that the San Andres-Glorieta is the dominant source of Horace Springs water, and that it mixes
with basalt and alluvial water upstream of the springs. For additional discussions of Horace
Springs, see Risser and Lyford (1984) and Baldwin and Anderholm (1992).
Based on Frenzel (1992), unnamed “Jurassic and Cretaceous” rocks also contribute some flow to
Horace Springs and the gaining reach, although he did not quantify that contribution. Based on
geochemistry data, Wolf (2010) confirmed that the “Cretaceous-Jurassic” units are a source of
water for Horace Springs, contributing between 0 and 10 percent. The available geologic
mapping indicates that the contributing units could include Dakota Sandstone and the Morrison
Formation (e.g. Westwater Canyon Member), and the deeper Entrada Sandstone. In this location,
these units are reported to have low yields (Rapp, 1960, p. 10; Baldwin and Rankin, 1995).
Risser (1982) estimated the total undepleted flow of Horace Springs at 4,000 acre-feet per year
(AFY) (5.5 cfs), and the additional spring and baseflow discharge downstream at 2,200 AFY (3
cfs). Based on the model of DBSA (2001, p.13), the downstream discharge may be closer to 4 cfs.
At one time, wastewater effluent from the city of Grants reached Horace Springs; that supply no
longer exists and, in any event, was not a component of the pre-development flow calculated by
Risser.
Ojo del Gallo is a spring located in San Rafael, south of Grants. Based on Frenzel (1992) and
other studies, it naturally discharged 5 to 7 cfs of San Andres-Glorieta water at a specific location
controlled by a fault. Risser estimated that the entire spring discharge (which he rounded to
3,000–5,000 AFY) would flow down Gallo Creek to the Rio San José and reach Acoma Pueblo.
Other studies (e.g., Petronis, 2010) consider that some portion of this flow would have been lost
to evapotranspiration before reaching Acoma.
Risser indicates that in pre-development times and in some years, snowmelt in late winter or early
spring from the Zuni Mountains could reach the pueblos via Bluewater Creek. He quantified this
supply at an average of 5,000 AFY (7 cfs), recognizing that it would be zero in many years, and
considerably higher in high runoff years. Risser also considered runoff above Laguna Pueblo
from Rio San José tributaries to be part of the pueblo supply and quantified it at 2,000 AFY (2.75
cfs), but highly variable over time.
Risser estimated the total undepleted water flowing to the pueblos of 16,200–18,200 acre-feet per
year (as much as 25 cfs), of which as much as 19 cfs could be observed at the western boundary
of Acoma Pueblo, below Horace Springs. While elements of this estimate have been questioned
(e.g., by Larson, 2009; Wilson, 2009), for EIS purposes it is the current condition that is most
relevant. The flow reaching the west boundary of Acoma Pueblo is measured at USGS gage
08243500. For much of the period of record there were many years with flow in the 5 to 6 cfs
range, which Risser and most others consider comes largely from Horace Springs. In the last 20
years, this flow has declined to 4 cfs or less; it was only 3.38 cfs in 2003, which was entirely from
Horace Springs and about 2 cfs less than Risser’s estimate of the natural flow.
Several factors explain why the current flow at gage 08243500 of 4 cfs is so much less than
Risser’s estimate of as much as 19 cfs:
• Whatever actual supply from Bluewater Creek may have occurred in the past is much
reduced due to storage of winter snowmelt in Bluewater Lake. While the gage data do
DEIS for Roca Honda Mine, Cibola National Forest 145