Bardsley, D.
Nevada Water Resources Association Annual Conference, 14-16 Feb 2017, Reno NV. 2017

At some historic mine sites, impoundment dewatering is the first step in remediation. At a site in Maine, horizontal wells were directed under, not through, a boulder/rubble tailings dam installed to dewater a tailings pond, remnant of an open-pit zinc/copper mine. Long distances to nearby utilities restricted the dewatering operations to a gravity-fed design, and the remote location and rugged terrain limited equipment access. The impoundment's embankments were constructed of mine waste, including boulder and cobble materials. Several controls were implemented at the Maine site to prevent uncontrolled release from the impoundment. Notably, casing was driven under the embankment, with the drilling going through the length of casing. The casing provided support to the overlying embankment and also focused any potential discharge through this one control point. A plug at the exit of the casing controlled tailings pond outflow. A gravity-fed bioreactor was constructed downgradient of the impoundment to treat the tailings drainage. Slides: https://cese.utulsa.edu/wp-content/uploads/2017/06/2016-IPEC-MINE-TAILING-DRAINAGE-A-BOTTOMS-UP-APPROACH-USING-HDD-DRILLING-AND-INSTALLATION-METHODS.pdf