The Combustion Engineering site in Windsor, after demolition was underway.

On a 600-acre property in Windsor — formerly an isolated private hunting preserve — a Connecticut company called Combustion Engineering triggered the first nuclear chain reaction to take place in the state in the late 1950s, according to Ron Kurtz, communications director for ABB, the Swiss conglomerate that owns the land today.

Now ABB, which bought CE in 1990, is spending tens of millions of dollars to clean the Windsor property of radioactive and chemical contamination in order to sell it for what it envisions as a mixed-use development of businesses, office buildings, some manufacturing, retail and residential.

"We're hoping for a higher density, pedestrian-friendly, bicycle-friendly site," says R. Keith Knauerhase, ABB's director of environmental engineering.

Town Manager Peter Souza says the plan is promising.

"We've had some real early discussions with [ABB] about what mixed-use might be and how it might match up with the town's overall long-term desires," Souza said.

Knauerhase says ABB does not expect to make back the money it will spend to clean the property to the standard of "free release," meaning suitable for any use. The multi-billion-dollar company has spent about $45 million so far and expects to spend as much as $125 million before the job is finished, it hopes by 2012.

"Once we're finished the federal government will send their teams in," said Knauerhase. "There will be three levels of review. We will perform our final status surveys, the state will perform its final status surveys and the fed will perform its final status surveys."

State and federal authorities have already released 365 of the 600 acres for any use, according to Knauerhase.

Combustion Engineering, whose roots go back to the mid-19th century when it began making boilers for steam locomotives, was enlisted by the U.S. Navy to work on its nuclear submarine program, just getting started in the 1950s.

The company designed and built a prototype naval nuclear reactor at the Windsor site in a nondescript industrial building with concrete walls four feet thick, reinforced by one-inch-diameter steel rebar. The Navy used the site to train about 14,000 sailors to operate the nuclear reactors that would power America's submarine fleet.

"They didn't know necessarily what the consequences were going to be so they designed the building for the worst-case scenario," said Knauerhase.

The clean-up of the nuclear contamination is straightforward, according to Knauerhase, consisting of digging up the contaminated soils and shipping them off to storage facilities in the West.

"The safeguards are high-tech but the work itself is very low-tech," said Knauerhase. "It's a shovel and dump-truck job."

A more complex challenge is presented by a stream on the property that was used to discharge filtered and diluted radioactive waste into the Farmington River.

"It's a natural stream and we're looking for the least disruptive way to remediate it," said Knauerhase. "What we don't want to do is run up and down it with bulldozers."

Both the sediments and the fish in the Farmington River have been sampled extensively, Knauerhase says, and any residual uranium was found to be "well below any remedial requirements" by both state and federal officials.