The Leadville Mine Drainage Tunnel Catastrophe: A Case Study of How Isotope Geochemistry Provided Forensic Evidence to Inform Policy Decisions

A state of emergency was declared in February 2008 because of fears that a blocked drainage tunnel in the Leadville mining district of Colorado could cause a catastrophic flood. An estimated 1 billion gallons of metals-laden groundwater poses an eminent threat to the city of Leadville and the headwaters of the Arkansas river. Within days of the declaration of a state of emergency, Governor Ritter and Senator Salazer of Colorado, along with a host of other local and statewide politicians, visited the site and emphasized the need to develop a fast yet safe mitigation plan. Here we provide information from a case study that illustrates how a suite of isotopic and hydrologic tools enables identification of critical, site-specific variables essential in developing a science plan to guide targeted remediation of the Leadville drainage tunnel. The isotopic tools, including both stable and radiogenic isotopes, provided clear and compelling evidence of water sources and flowpaths in an area that has undergone extensive perturbations, including the drilling of more than 2,000 mine shafts. This forensic evidence was the key information in developing a plan to plug the drainage tunnel several hundred feet underground, divert a major source of polluted water from reaching the collapsed tunnel and piping it to an existing treatment plant, and guidance on where to place pumps in additional mine shafts, and the drilling of new wells, to pump water in case the plugging of the tunnel caused water to pool up and raise the water table to dangerous heights.