Challenge. Develop a tool, requiring acceptance as part of a federal Environmental Impact Statement (EIS) process and a state mine dewatering permit process, capable of assessing proposed mine dewatering impacts on operations, costs, and scarce water resources
Solution. INTERA used the MODFLOW SURFACT code to develop a basin-scale (>54,000 km2) model that spanned portions of the states of New Mexico, Colorado, Utah, and Arizona. The model consisted of 10 layers that defined the complex sedimentary geology and the three aquifers that required to be dewatered as part of mining operations. We built the model to simulate the 50-year period of historical mine dewatering that re moved 100 billion gallons from the system and demonstrated good agreement between observed and simulated groundwater flow. The predictive model demonstrated the limited effects of the proposed dewatering operations on existing wells used for public water supplies and other water rights holders, especially perennial river reaches. Our model was accepted by the regulators as an appropriate tool for the federal EIS process. As a result of INTERA’s modeling efforts, the New Mexico State Engineer issued this project the first mine dewatering permit since the state Mine Dewatering Act was passed in 1980. Showing that the dewatering operations will have no adverse impacts on other water users enabled the demonstration of the project’s viability to both stakeholders and investors.
