The Schwartzwalder mine, owned by Cotter Corp., is upstream from the reservoir. Inspectors for a state regulatory agency say the water level in the mine is rising and could soon hit the rim, The Denver Post reported.
"It's the drinking water supply. We're very concerned about it. We're doing everything we can," Tony Waldron of Colorado's Department of Natural Resources said.
The state has fined Cotter, a subsidiary of General Atomics based in San Diego, $55,000 and ordered the company to pump water from the mine, saying it would suspend most of the fine. State officials say Cotter has refused to pay or pump.
The mine, northwest of Golden, is near Ralston Creek. The creek flows into Ralston Reservoir and inspectors say the water in the creek has uranium levels about 10 times the federal standard, while water in the mine is 1,000 times as contaminated.
Cotter says the water in the mine is not seeping into groundwater.