Faulty valve leads to an ammonia leak in Stanhope

STANHOPE – About 2,600 gallons of anhydrous ammonia leaked at a cooperative in Stanhope Wednesday afternoon, prompting the evacuation of a few homes and killing nearby vegetation.

A man who tried to stop the leak got the corrosive substance on his face and upper body, but he declined medical treatment, according to Capt. Steve Hergenreter of the Fort Dodge Fire Department.

The incident began at about 2:30 p.m. at the Heartland Cooperative, 515 Railway St. Hergenreter said a pressure relief valve for two connected 18,000-gallon tanks of anhydrous ammonia failed and a small leak started.

He said a co-op employee attempted to make repairs, but was unsuccessful because a valve that was believed to be closed was actually open. The leak got worse, and the employee was sprayed by the chemical.

Hergenreter said liquid ammonia was coming out of the valve and turning into clouds of gas.

”It was a substantial leak,” he said Wednesday evening.

The regional hazardous materials team operated by the Fort Dodge Fire Department was called to the scene. Firefighters in special protective suits entered the cloud of ammonia and stopped the leak by closing a valve. They also replaced the failed valve with a new one supplied by the cooperative.

The anhydrous ammonia tanks are a few hundred feet from some houses, which were evacuated.

A larger evacuation wasn’t necessary because the cooperative’s property is on the southwest side of Stanhope and the wind was blowing from the north, pushing the ammonia cloud away from most of the city.

”The wind was in the right direction, or this might have been worse,” said Stanhope Fire Chief Mike Hansen.

Grass and other vegetation within about 300 feet of the downwind side of the tanks was killed, Hergenreter said.

Firefighters from Stanhope and Stratford, Hamilton County sheriff’s deputies and police officers from Stanhope, Ellsworth and Jewell responded.

Hansen said the leak was controlled by about 4:30 p.m.

A hazardous materials response computer program was used by Hergenreter to estimate that about 2,600 gallons leaked.

Anhydrous ammonia is a corrosive substance that attacks the respiratory system, skin and eyes, he said.