Draft Environmental Impact Statement for Roca Honda Mine

Chapter 3. Affected Environment and Environmental Consequences
• San Mateo Reservoir
• Flowing in San Mateo Creek above the community of San Mateo
When these locations were revisited during different seasons, surface water was found only in the
San Mateo Reservoir, as irrigation releases from the reservoir, and at Bridge spring. Based on
these recent observations, RHR concluded that from the town of San Mateo downstream to a
pond on the Lee Ranch, San Mateo Creek is an intermittent stream that has flow when water is
being released from the reservoir for irrigation purposes and during high rainfall events.
Downstream of the pond, San Mateo Creek is ephemeral. This conclusion is consistent with the
historical data and conclusions presented by NMEI (1974).
San Mateo Creek Surface Water Quality
The 1974 NMEI baseline study collected data on surface water chemistry within the San Mateo
Creek watershed. Surface water samples were collected from the perennial upper reach of San
Mateo Creek and from ephemeral tributaries to San Mateo Creek during rain or spring runoff
events. The historical study provides general information on water quality. Surface water
collected from higher elevations tended to be lower in total dissolved solids (TDS), but more
acidic and higher in sulfate than water from lower elevations. Samples from some locations, for
example, near the community of San Mateo, exhibited high levels of sodium. High levels of
suspended solids were associated with high flow rates (NMEI 1974).
NMEI collected surface water samples from upper San Mateo Creek and the Marquez Canyon
drainages within the upper San Mateo Creek watershed, above the RHR permit area. Table 4
tabulates chemistry data for two locations along San Mateo Creek south of and closest to the
permit area (locations 29 and 30 on figure 33) and two locations (numbers 37 and 40 on figure
34) in Marquez Canyon.
Permit Area Surface Water Hydrology
The permit area is drained by a number of ephemeral arroyos which drain south to San Mateo
Creek and north to Canada de las Vacas (figure 33). RHR field investigations between 2008 and
2010 included observations of surface water. No perennial or intermittent surface water systems,
lakes, wetlands, reservoirs, or springs were observed within the permit area, with the exception of
a stock reservoir in Section 16 and seasonal tinajas (seasonal water pockets in bedrock) in Section
10. The stock reservoir over this period was not observed to have standing water. The tinajas were
located within small, eastward draining arroyos on the east side of Section 10. They contained
water in September 2009 and water samples were later collected from the two largest tinajas.
During the following summer the tinajas were dry.
122 DEIS for Roca Honda Mine, Cibola National Forest