A defunct uranium mine in Jefferson County is contaminating groundwater near a reservoir, but government regulators and mine executives have yet to settle on a plan for cleanup.

Uranium concentrations in groundwater 30 feet beneath the brim of the Schwartzwalder Mine exceed the human health standard for uranium by more than 1,000 times, according to state records reviewed Thursday.

Unhealthy concentrations also were detected in Ralston Creek, which eventually enters Denver Water's Ralston Reservoir. The reservoir supplies water to Denver and Arvada.

Denver Water managers say no uranium contamination has entered the drinking-water supply.

State officials said they want the mine's owner — Greenwood Village- based Cotter Corp., a subsidiary of General Atomics — to submit by Monday a plan for dealing with the contamination at the mine.

Colorado mining regulators warned Cotter in July "that water quality degradation at the Schwartz- walder Mine is critical and may be approaching conditions requiring emergency response." Three months later, state officials rejected an initial Cotter protection plan as inadequate, declaring "a potential hazard to human health, property and the environment."

Neither Cotter nor the Colorado Department of Public Health and Environment, which is responsible for water quality, notified Denver Water.

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"It would have been nice to know," said Brian Good, Denver Water's manager of operations and maintenance.

Denver Water now will increase testing for uranium, Good said, calling on Cotter to clean it up.

Because Denver's Moffat water- treatment plant is closed for maintenance, no Ralston Reservoir water currently enters Denver's drinking-water system, Good said.

"Our water is safe," he said, "but it's a little bit troubling that (uranium) is coming into our reservoir in those concentrations."

Jefferson County residents closest to the mine face "no imminent health threat" but swift action is crucial, Jefferson County Commissioner Kathy Hartman said.

"I want an appropriate plan with all reasonable haste," she said. "The fastest plan may not be the best. But the best plan could be too slow."

Once the nation's largest underground uranium mine, Schwartz- walder — 7 miles northwest of Golden — ceased production in 2000.

Colorado's Division of Reclamation, Mining and Safety "does not believe conditions requiring an emergency response currently exist. If they should arise, (the state) can require Cotter to pump and treat mine water to bring down levels and ensure groundwater is not jeopardized," state spokesman Theo Stein said.

Uranium contamination of mine water far breaches health standards, "but we believe it is isolated from the creek," Cotter vice president John Hamrick said.

Cotter is unlikely to pump out and treat contaminated water, Hamrick said. The company is investigating "several different methods," including creation of a wetland.

Environment Colorado activists said this shows the dirty side of uranium activities needed for nuclear energy.

"The mess at Schwartzwalder shows that Colorado isn't ready for a new uranium boom," spokesman Matt Garrington said. "We have abandoned and inactive uranium mines littered across the state that haven't been cleaned up and are still causing environmental problems."