ROCHESTER, N.H. – A fracture and leak in the city’s 1 million-gallon water tank led officials who feared it would collapse to evacuate homes, a nearby pediatrics practice and a small airport on Tuesday.

The leak is at the base of the water tank, which is on the ground, not atop a tower, Rochester City Manager Daniel Fitzpatrick said. The tank didn’t appear to be at risk of collapsing, but there was a potential that it could, Fitzpatrick said in an email to city employees.

City officials were draining the green cylindrical tank, which appears to be at least six stories tall, and advising the city’s 30,000 residents their water pressure would be reduced.

Skyhaven Airport, which is just southeast of the city’s main business district and has one runway, was evacuated Tuesday morning, an employee said.

“We have to evacuate right now,” Nohea Nichols said by telephone late Tuesday morning. “The fire chief just came in.”

Young patients at the Rochester Pediatrics Association, which is affiliated with Frisbie Memorial Hospital, were removed because it’s within the quarter-mile radius public officials cleared as a safety precaution.

Frisbie Memorial Hospital emergency nursing director John Levitow said he was unsure how many children were taken from the facility. No patients were taken from the hospital, he said.

The hospital remained on standby throughout the day in the event of a disaster, said Joe Shields, its vice president for planning.

State Department of Public Works officials said the tank’s capacity was 1 million gallons. Mayor T.J. Jean later said he thought the capacity was 2 million gallons.

The water was being drained through a large fire hose and nozzle mounted atop a fire truck’s aerial ladder.

Jean said the tank was 90 percent full when the leak was detected Tuesday morning and everyone within a quarter-mile of the tank was ordered to leave.

“We had no way of predicting what would happen to the tank – if it would, in fact, collapse upon itself and spill 2 million gallons of water down Rochester Hill,” Jean said. “As the water continues to drain, the situation becomes safer and safer for local residents.”

The main commuter route where the tank is located, Rochester Hill Road, remained closed to traffic well into the evening.

State Sen. Fenton Groen, a Republican whose district includes Rochester, said Frisbie president Al Felgar left the police barricade where they were seeking information to help with the evacuation of the pediatrics practice. Groen said a police officer at the barricade had told him the tank could burst.

Groen said the tank regulates water pressure and serves as a reserve supply of water for the city’s residents. He said he didn’t expect the city’s water supply would be jeopardized.