Draft Environmental Impact Statement for Roca Honda Mine

Chapter 3. Affected Environment and Environmental Consequences
drawdown remains. One effect of dewatering is to substantially increase the downward gradient
from the Dakota Sandstone to the Westwater Canyon Member of the Morrison Formation.
Water Quality in the Westwater
As part of the baseline investigations, RHR compiled historical water quality data for the
Westwater Canyon in the study area. Beginning in 2008, RHR collected water quality samples
from 10 area wells completed in the Westwater Canyon, including the three monitoring wells
constructed in Section 16 of the permit area (S-1, S-3, and S-4). Figure 9-15 of the BDR shows
the locations of the wells sampled and those for which there are historical data. Nine Westwater
Canyon wells will be part of the Groundwater Sampling Program in the future, including the three
onsite monitoring wells; see figure 9-16 and table 9-14 in the BDR (RHR, 2011a).
Most wells have been sampled multiple times. The samples were analyzed in the field for
conductivity, pH and temperature; and in the laboratory for general chemical parameters, metals,
radionuclides, volatile organic compounds (VOCs), and synthetic organic compounds (SOCs).
The analytical results for the Westwater Canyon are summarized in tables 9-9 (Major
Constituents) and 9-10 (Minor Constituents) of the Baseline Data Report; Appendices 9-F
(Regional Wells) and 9-G (Permit Area Wells) of the report provide more detailed data. Note that
no VOCs or SOCs were detected in any of the samples analyzed from any of the wells, regardless
of aquifer, so the data for those parameters are not included in the report.
TDS content of the water from the 3 permit area wells was low, ranging from 425 to 532
milligrams per liter (mg/L) in the 15 samples analyzed. Five Westwater Canyon wells
approximately 5-1/2 miles west of the permit area had much higher TDS, ranging from 1,980 to
3,440 mg/L (excluding an apparent outlier value). Much of the higher TDS was in the form of
sulfate, ranging from 1,188 to 2,150 mg/L. That level of sulfate is far above the Federal Safe
Drinking Water Act (SDWA) Secondary Standard of 250 mg/L, and would not be considered
potable. Some of the high TDS wells also exceeded standards for a few metals and radionuclides.
Permit area monitoring well S-4 water was not found to contain any parameters exceeding SDWA
Primary or Secondary Standards, aside from the slight exceedance of the 500 mg/L Secondary
Standard for TDS. Permit area monitoring wells S-1 and S-3, however, produced water that
exceeded the SDWA Primary Standard for one or more radionuclides, though not uranium; see
table 7.
Table 7. Radionuclide data from permit area water monitoring wells
Well
Parameter Gross Beta Gross Alpha Radium-226
Standard ~50 1 15 5 2
Units pCi/L pCi/L pCi/L
S-1 50.1 to 178 135 to 418 27 to 69
S-3 Not exceeded 17.8 to 35.2 Not exceeded
Standard is 4 millirem/year, approximately 50 pCi/L, depending on radionuclide
Standard is 5 pCi/L for Radium-226 and Radium-228 combined
The SDWA standards are based on long-term ingestion of the water as the sole source of drinking
water; different standards could apply to discharge of water of this quality to surface water
drainage, for example.
DEIS for Roca Honda Mine, Cibola National Forest 135