A gas leak at the intersection of 55th Street and Dorchester Avenue interrupted heat service for more than 300 residents Thursday, causing traffic problems and forcing some residents to flee their homes.

Both towers on the island formed by the division at 1400 East 55th Street were affected, but only the north one was evacuated. A few units north of 55th Street were also affected.

Rod Sierra, a spokesman for People’s Energy, said the leak was caused by the extreme change in temperature on the antiquated pipes in the Hyde Park area.

“In an older neighborhood such as this, we are using older ductile pipes,” he said. “Given that they are made of chrome, they are susceptible to extreme hot and cold temperatures. We are in the process of replacing these pipes, but there are 6,000 pipes in the system.”

Sierra said the leak was four to five inches wide and occurred in an eight-inch pipe. These ductile pipes are generally used to transport water.

The Chicago Transit Authority sent buses to the site to keep the evacuated residents warm, said Larry Langford, spokesman for the city’s office of Emergency Management (OEM).

Red Cross members also arrived to serve hot food to the displaced residents. People’s Energy, the gas supplier of the affected buildings, discovered the leak after the company received a call about the smell of gas in the area, according to Elizabeth Castro, another spokesman for People’s Energy.

After discovering the leak, People’s Energy tried several ways to stop it. First, they tried to simply turn off the valves that controlled that pipe—six in all—but were unsuccessful.

The company then decided to shut off an outer ring, a set of values that affect a wider region, in an attempt to slow the flow of gas.

Asked if the company had a map that showed all the pipes and valves, Sierra again referred to the age of the system in this area.

“Often there are older, abandoned mains that the system has bypassed that were never fully bled out when they were bypassed. The gas coming out might simply be the gas bleeding from these pipes,” Sierra said.

He said the workmen then tried to stop the gas flow further up the pipe—about 40 feet south of the original leak—to try to fix it safely.

“They have fixed these things with the gas flowing,” Sierra said. “I wouldn’t, but those guys do. They just slowly put a sleeve over the leak. However, with the people around they decided it would be safer to stop the gas first.”

Later that night, when other alternatives had failed, Castro said the company decided to try put a sleeve over the pipe. “There is a rubber gasket under the sleeve and they just screw it shut,” she said.

When this article went to press, the leak had not yet been fixed. After People’s Energy fixes the leak, they said they will likely go door-to-door to relight pilot lights in people’s homes.

City departments involved in the effort to manage the leak included the OEM; the Department of Human Services, which was directing the affected resident services; the combined CPD and UCPD, who secured the area and prevented passers-by from getting too close; the fire department, who would handle any accidental fires; and the Department of the Environment, which enforces the City’s environmental regulations.

“The fire department is in charge of ensuring all of our safety,” said CPD Sergeant James Cummings, who was securing the area on 55th Street, west of Lake Park Avenue.

Brothers Evan Sosin, 13, and Dominick Dujur, 12, came home from school to find that they could not go upstairs due to the gas leak. They went up to get their dog, Daisy, and went to a friend’s house on Blackstone Avenue. From there, the two called their mother, who told them to hang on until she called them back. By 6:30 p.m., they were skulking around the south tower with their friend Justin Callahan, also 12.

By nightfall, with everyone just trying to stay warm, Brian Duncan, a resident of the south tower that was outside helping residents, said the severity of the accident was intensified by the age of the residents. “The building has a lot of senior citizens, people that have been living there for 20 years.”