Abstract: Mining usually causes severe anthropogenic changes by which the ground- or surface water might be significantly polluted. One of the main problems in the mining industry are acid mine drainage, the drainage of heavy metals, and the prediction of mine water rebound after mine closure. Therefore, the knowledge about the hydraulic behaviour of the mine water within the flooded mine might significantly reduce the costs of mine closure and remediation. In the literature, the difficulties in evaluating the hydrodynamics of flooded mines are well described, but only few tracer tests in flooded mines have been published so far. Most tracer tests linked to mine water problems were related to either pollution of the aquifer or radioactive waste disposal and not the mine water itself. Applying the results of the test provides possibilities f or optimizing the outcome of the source-path-target methodology and therefore diminishes the costs of remediation strategies. Consequently, prior to planning of remediation strategies or numerical simulations, relatively cheap and reliable results for decision making can be obtained via a well conducted tracer test. < copyright > 2005 Elsevier GmbH. All rights reserved.

Abstract: In 1991, LTV Steel Mining decided to close an open-pit taconite mine in northeastern Minnesota using a passive-treatment approach consisting of limiting infiltration into the stockpiles and wetland treatment to remove metals. More than 50 Mt (55 million st) of sulfide-containing waste had been stockpiled adjacent to the mine during its 30 years of operation. Drainage from the stockpiles contained elevated levels of copper, nickel, cobalt and zinc. Nickel is the major trace metal in the drainages. Before the closure, the annual median concentrations ranged from 1.5 to 50 mg/L. Copper, cobalt and zinc are also present but they are generally less than 5% of the nickel values. Median pH levels range from 5 to 7.5, but most of the stockpile drainages have pH levels greater than 6.5. Based on the chemical composition of each stockpile, a cover material was selected. The higher the potential that a stockpile had to produce acid drainage, the lower the permeability of the capping material required. Covers ranged from overburden soil removed at the mine to a flexible plastic liner. Predictions of the reduction in infiltration ranged from 40% for the native soil to more than 90% for the plastic liner. Five constructed wetlands have been installed since 1992. They have removed 60% to 90% of the nickel in the drainages. Total capital costs for all the infiltration reduction and wetlands exceeded $6.5 million, but maintenance costs are less than 1% of those for an active treatment plant. Because mine-drainage problems can continue for more than 100 years, the lower annual operating costs should pay for the construction of the wetland-treatment systems within seven years.

Abstract: This article provides examples of reclamation and remediation in Colorado watersheds. The projects were undertaken by the US Environmental Protection Agency (EPA) Region 8, in cooperation with the Colorado Division of Minerals and Geology (CDMG), Colorado Department of Public Health and Environment (CDPHE), US Forest Service (USFS), the Bureau of Land Management (BLM), Bureau of Reclamation (BOR) and the US Geological Survey (USGS). These agencies collaborated on the environmental problems at abandoned mines. These samples involved the interaction of surface and ground waters with sulfide-bearing rocks, mine workings and surface mine spoils that produce acid solutions charged with heavy metals that are toxic to organisms. In these examples, acid mine drainage from historic mines in Colorado has been approached cooperatively with stakeholders. Each example emphasizes one aspect of the three-stage process. These stages include characterization and prioritization, hydrologic controls and the evaluation of long-term remediation activities.