Modeled Versus Observed Filling Rates of the Historical Getchell Pit Lakes, Nevada

Within the next few decades, Nevada will have over 35
pit lakes resulting from open-pit mining below the water
table. Operational and regulatory decisions are based, in part,
on results of numerical groundwater flow models used to predict
future pit-lake filling rates. Few studies have been completed
that demonstrate modeled rates of pit filling reasonably
reflect actual rates, and, at this time, none of these
studies has been published. In this work, we select one type
of modeling approach that has been used by previous workers
in predicting pit-lake filling rates. A typical modeling
method was selected so that we could determine how accurately
a standard method might predict water-level increases
through time as a pit lake fills following cessation of dewatering
activities. Data from the Getchell Mine (Humboldt
County) were selected for use in testing the model because
(1) there were historical water level and chemical monitoring
data from the pit lakes and numerous surrounding wells useful
in constructing, calibrating and testing the model, and (2)
the water levels in the pit lakes during the 15 years of filling
attained nearly steady-state conditions.
During a period of inactivity between 1968 and 1983,
three pits filled with water as the groundwater table recovered
from previous mine dewatering (Fig. 1). There are over 50
wells at the mine with water level measurements having been