A large portion of the 19th Ward was under a 24-hour boil order for water usage after an incident in which ComEd was performing maintenance at the Roseland water pumping station, according to city officials.

The affected area spanned from east of Kedzie Avenue, west of Interstate 57, north of 119th Street and southwest of Beverly Avenue.

City officials said that on May 6, from 8:30 to 9:30 a.m., the drinking-water pressure at the station was impacted during ComEd maintenance. A boil order was announced at a press conference that afternoon and was lifted the morning of May 7.

Andrea Cheng, the acting commissioner of the Chicago Department of Water Management (CDWM), said at the press conference on May 6 that the station was “fully back online and pressurized.”

She said contaminants could have affected the water supply after the incident occurred, although that was “very unlikely” and the boil order went into effect “out of an abundance of caution.”

“We’re zero-risk people,” Cheng said.

Cheng said that a power outage occurred, but ComEd Vice President of External Affairs Rich Negrin said it was not a power-outage issue. Maintenance work was being performed outside the station, he said, and the four power lines going to the pump never lost power.

“The question is whether some of the maintenance that occurred had an impact on some of the equipment,” Negrin said. “We’re working closely with the city.”

Chicago Office of Emergency Management and Communications Executive Director Rich Guidice also said the situation was not related to a power outage.

Cheng said the city adds chlorine to eliminate bacteria and viruses, and she had concerns that with the pressure reduced, contaminants could enter the supply of drinking water.

Those in the affected area were advised to bring any water they planned to consume to a rolling boil for 5 minutes.

Cheng said it would take 24 hours to analyze water samples, and the city would then update members of the affected communities. 19th Ward Ald. Matt O’Shea, who issued multiple emails to constituents regarding the incident, distributed one on the morning of May 7 saying the order had been lifted and that the CDWM ‘s water purification laboratories verified that the water is safe to drink.

Nonetheless, he said the CDWM advised taking several precautions, including flushing all faucets and running all cold-water faucets for 5 minutes; flushing automatic icemakers, including making three batches of ice and discarding all three batches; draining and refilling hot water tanks; and flushing drinking fountains by continuously running them for 5 minutes.

Cheng said the CDWM was conducting an investigation in order to prevent similar problems.

Questions arose about the station’s age—it’s 110 years old—but Cheng called that issue “irrelevant.”

“We maintain the pumps within the pumping station regularly,” she said, “and have a preventative maintenance program that keeps it running well.”

People with questions can call the city’s water quality surveillance section at (312) 744-8190 or visit chicago.gov/water.