As a result, at least 21 of the state's currently operating and closed municipal landfills are now leaking dangerous chemicals, such as nitrates, chlorides, pesticides and dry-cleaning solvents, into groundwater. The number could be even higher; many of the closed dumps aren't monitored.
The landfill that poses the biggest threat is in Cheyenne. Records show it's been leaking since 1996, contaminating shallow groundwater zones and an aquifer 170 feet down. The confined aquifer the city uses for drinking water has yet to be affected, but only a layer of sediment separates it from the contaminated groundwater above it.
City officials began capping parts of the dump in 1996 to keep rain and snow from making the leak worse. They plan to stop using the dump when it reaches capacity, within a few years.
To fix the dump problems around the state, Gov. Dave Freudenthal has appointed a citizens' advisory group to come up with new solid-waste policies. Goals include new emphasis on recycling, helping local governments speed cleanups, and building safer regional landfills.
The Department of Environmental Quality is also working on new guidelines to make it tougher for communities to build landfills without liners. Officials estimate that fixing and cleaning up after the leaks will cost at least $50 million.
"That's a big expensive 'oops,' " says Bob Doctor of the DEQ.