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Potential mine discharge into Left Hand Creek; EPA and State of Colorado investigate

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Global Mining Review,

The US Environmental Protection Agency and the Colorado Department of Public Health and Environment are investigating a potential mine discharge and a fish kill in the upper portions of Left Hand Creek in Boulder County, Colorado.

On 22 October, Superfund project managers for both EPA and the state health department were notified of discolored water and dead fish in Left Hand Creek downstream from the Captain Jack Mill Superfund site. EPA and the state health department currently are investigating to determine if the fish kill is related to cleanup activities at the site. The number of fish killed is unknown at this time but is estimated to be in the low 100s.

The Left Hand Water District, which has a drinking water intake approximately 15 miles downstream, was notified, as well as the Boulder County Health Department and the Boulder County Office of Emergency Management. Colorado Parks and Wildlife staff already had been notified by a local resident.

The Left Hand Water District tests both raw and treated water on a continuous basis. Out of an abundance of caution, the district shut off the intake from Left Hand Creek when notified. The intake has since been reopened following test results that met water quality standards. The water quality impacts observed in Left Hand Creek were above the confluence with James Creek, which likely further diluted any potential contaminants before reaching the Left Hand Water District intake or downstream waters.

The state health department and EPA have been addressing contamination associated with historic mining operations at the Captain Jack Mill Superfund site since the issuance of the Record of Decision in 2008. The agencies are in the process of implementing an innovative, in-tunnel water treatment process to improve the quality of water discharging from the site. As part of the cleanup, a flow-through bulkhead was installed in the Big Five tunnel. The bulkhead valve is currently controlling the discharge of mining-influenced water to about 30 gal./min., which is much less than historic unrestricted flows.

EPA and the state health department have on-scene co-ordinators and contractors collecting samples to assist with the investigation. More information will be available in a few days.

Left Hand Creek is a tributary of Saint Vrain Creek in Boulder County.

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