EPA Completes Pump Test at Leadville Mine Drainage Tunnel

The U.S. Environmental Protection Agency has concluded a successful pump test of the relief well at the Leadville Mine Drainage Tunnel in Leadville, Colo. The test helped the agency better understand how the flooded underground mine workings would react to pumping, the optimal rate of pumping, and the appropriate size for the permanent pump, according to a June 4 news release.

Water pumped from the relief well during the test was discharged into a temporary pond. EPA is using the temporary pond because the pipeline designed to convey water from the relief well to the Bureau of Reclamation's water treatment plant has not been completed. The pond is designed to function in a manner similar to that of a farm pond and is not lined. The pond allows the water pumped into it to seep back into the soil. The pond also contains an overflow pipe that discharges water from the pond when the water reaches a certain level to prevent damage to the dam.

EPA received information that there was public concern about water flowing from the overflow pipe and seeping from the toe of the pond's dam. The overflow pipe is working well and doing what it is designed to do —discharge water from the pond when it gets too full. The quality of the water is mildly acidic (pH 6). The water does not pose a threat to health or the environment, because it is a relatively low volume, the discharge was of short duration, and the water mixed with snowmelt flowing down Evans Gulch. As the current water level in the pond is 14 inches below the outlet to the overflow pipe, the pipe is no longer releasing water from the pond.

A small amount of water is seeping from the toe of the dam. Testing of this water found that it was near neutral (pH 6.5) and does not pose a health or environmental threat. The pond is designed to allow water in it to seep back into the soil.

A few cracks have appeared on the surface of the temporary dam. It is not unusual for this to happen. The dam is built of local sandy material that is subject to cracking when it contacts water. EPA does not believe that these cracks impact the structural integrity of the dam. The dam was built to hold the volume of water in the pond and it is performing as designed. The agency is continuing to monitor the dam and the discharge at the relief well site.

EPA is still on schedule to have the relief well operational by mid-June. At that time, water will be pumped from the relief well with the temporary pump and transported via a pipeline to the Bureau of Reclamation's water treatment facility at the mouth of the tunnel where it will be treated and released into the Arkansas River.

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