Draft Environmental Impact Statement for Roca Honda Mine

Chapter 3. Affected Environment and Environmental Consequences
Table 20. Predicted change in San Juan Basin water balance from RHR Mine; positive
numbers are inputs and negative numbers are outputs, in total acre-feet
Drawdown in Pumped Units
As expected, the RHR model predicts that mine dewatering would form cones of depression
(areas in which water levels are drawn down) in the pumped aquifers that are centered in the
permit area and that are sized in proportion to the rate and total amount of pumping. Table 21
summarizes the model predictions for scenario 2 (no new pumping except RHR), as determined
from review of Intera (2012) and from model output files. Drawdown values are for the units
within the permit area and indicate the depth of the drawdown cone created. Maximum
drawdown in aquifers shallower than the Gallup sandstone are predicted to total no more than a
few feet and are discussed later in respect to springs.
Table 21. Predicted drawdown caused by dewatering at the Roca Honda Mine
Aquifer
Maximum
Drawdown
Drawdown
at End of
Mining
Drawdown
100 Years
after Mining
Extent of 10 ft
Drawdown at
End of Mining
Extent of 1 ft
Drawdown at
End of Mining
Gallup 366 ft