Modeling Application in Evaluating Groundwater-Surface Interactions Due to Mining Activities

Tuesday, April 13, 2010: 3:25 p.m.
Horace Tabor/Molly Brown (Westin Tabor Center, Denver)
Xin Song , ARCADIS, San Francisco, CA
Gaston Leone, PE , ARCADIS US Inc., Highlands Ranch, CO
This paper presents a modeling application to evaluate groundwater-surface interactions due to proposed mining activities.  The proposed project has the potential to impact surface and groundwater resources and release metals and other constituents into the environment. A numerical groundwater flow and contaminant fate and transport model has been developed to support the impact analysis for the environmental impact statement.

 

The project site has very complicated geology and hydrostrategraphy. The proposed mine consists of an open pit that would be mined in three panels and includes various auxiliary mine facilities Mining activities are expected to occur over a 17-year period and include construction of overburden piles and ore stockpiles, pit backfilling, construction of sediment retention structures, and reclamation of impacted areas. Several streams and surface water bodies occur within or near the project area, one of which is a Special Resource Water recognized as needing protection to maintain outstanding characteristics and current beneficial uses. 

 

The objectives of the model application are to simulate the pre-mining groundwater system and its interaction with surface water bodies and evaluate the potential impacts on surface and groundwater resources associated with the proposed mining activities.  Specifically, the developed numerical groundwater flow and solute transport model was used to (1) estimate groundwater inflow and dewatering requirements for the open pits, (2) predict potential changes in groundwater levels and quality during mining operations and after closure, (3) predict potential changes in stream flows and quality in the surface water related to mining activities, (4) predict post-mining water levels in backfilled pits and impacted aquifers, and (5) estimate potential impacts to groundwater and surface water quality associated with leachate from mine facilities, including open pits, backfills, external waste dumps, and ore stockpiles.