Fish Kill In Left Hand Creek Was From Superfund Site

BOULDER COUNTY, CO -- Contaminated water from the Captain Jack Mine superfund is believed to be behind the dead fish and discolored water in upper portions of Left Hand Creek earlier this week, according to a determination by the Colorado Department of Public Health and Environment and the U.S. Environmental Protection Agency. The EPA and the state health department have temporarily closed the flow-through valve on the site's Big Five tunnel bulkhead and are planning next steps, according to a press release from the Colorado Department of Public Health and Environment on Friday, Oct. 26.

After a fish kill estimated to number in the low 100s was reported on Oct. 22, field monitoring and water samples from various locations along Left Hand Creek indicated that water discharging from the Big Five tunnel was more acidic and contained more heavy metals than in past testing. Given the seasonal low flows in Left Hand Creek, this significantly impacted water quality approximately five miles below the superfund site, according to the state agency.

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The Captain Jack Mill Superfund site is located east of the Peak to Peak highway along the creek, and was issued its Record of Decision in 2008. The EPA and the state health department have been working together to address possible contamination from historic mining operations in the area. As a part of those operations, a flow-through bulkhead was installed in the Big Five tunnel to control the discharge of mining-influenced water to about 30 gallons per minute.

The agencies will continue to monitor stream water quality while assessing the in-tunnel treatment system performance and implementing changes to the system as necessary.

The Left Hand Water District, which has an intake downstream of the affected area, tests both raw and treated water on a continuous basis. That intake remains open after test results showed no impact in water quality for downstream users.

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