EarthFax has conducted numerous hydrologic investigations at proposed and existing surface and underground coal and mineral mines in the western United States and internationally. This work has included detailed evaluations of existing data as well as the design of long-term, site-specific surface- and groundwater monitoring programs to establish pre-mining baseline conditions and to detect potential impacts to water quality and quantity in the affected areas.
Utilizing site specific and regional data, we have delineated existing condi¬tions and determined the future hydrologic consequences of mining. We accomplished this by assessing trends from historic data and using numerical models to estimate future impacts and the affects of various mitigation measures. In one case, this involved modeling the groundwater impacts of surface coal mining at two adjacent mines in eastern Wyoming. The need for accuracy was increased by the fact that the coal seam being mined also served as a regional aquifer. We performed approximately 40 slug tests and 10 pumping tests on existing monitoring wells to assess local groundwater conditions. We then modeled conditions in the overburden, coal, and underburden using a finite-difference numerical model, performed sensitivity analyses, and estimated the time required for water levels to recover following mining.
EarthFax has also assisted mining companies in evaluating their long-term monitoring data to detect potential impacts from mining activities, including performance of statistical analyses, evaluation of trends in flow and water quality, and determination of seasonal variations. As appropriate, we compared site-specific data with climatic changes utilizing the Palmer Hydrologic Index to separate mine-induced impacts from natural climatic variations. We then recommended changes to long-term monitoring programs to ensure that impacts could be monitored in the most cost-effective manner.
We have also designed several Best Management Practices to minimize the hydrologic impacts of mining during both operational and reclamation periods. These designs have included multiple runoff- and sediment-control structures, including sedimentation basins, channel-stability improvements, regrading and revegetation of disturbed areas, installation of sediment traps, and changes in land-use practices.