London Mine Extension Tunnel and Leach Well
TZA Water Engineers has been working with the London Mine facilities outside Alma, Colorado, supporting the Leach Well operations and reporting since 2009. In 2011, TZA staff began working closely with the District’s ownership, management and operations personnel to address compliance issues with the London Mine Extension Tunnel industrial wastewater treatment facility treating acid mine drainage. Through a series of planning documents reviewed by the Water Quality Control Division, improvements to reduce metals concentrations discharged to No Name Creek were constructed in the summer/fall of 2013.
While the 2013 improvements reduced the levels of metals discharged to No Name Creek, the effluent concentrations would still exceed stringent permit limits on most occasions. In 2015, TZA supported the District’s efforts to select a new operator of the London Mine Extension Tunnel industrial wastewater treatment facility in advance of the 2015 operating season (i.e. May to September). At the end of the 2015 operating season, TZA worked with the new operator to identify additional enhancements to the treatment process, including the addition of an inclined plat clarifier and the addition of an alternate chemical to benefit the flocculation/sedimentation process.
The District sold its interests in the tunnel and treatment assets in late 2016. TZA continues to provide water accounting support, consultation for the Leach Well operations, and recommendations for replacing the instrumentation and control aspects of the flow measurement and Leach Well.