A failure to perform routine maintenance and a surge of poor-quality raw water entering Richmond’s treatment plant triggered the city’s second boil water advisory this year, city officials said Thursday. 

Multiple neighborhoods and businesses were affected by the advisory, which was lifted just hours before a press conference at City Hall revealed early findings from a joint review by the Department of Public Utilities and the Virginia Department of Health.

The issue stemmed in part from alum sludge, a byproduct of the water treatment process in which aluminum sulfate binds with impurities in the water and settles in tanks. If not cleaned out regularly, this sludge can break loose, clogging filters and compromising water quality—as it did in this case.

“Maintenance activity has to occur on a reoccurring basis, in a timely fashion, otherwise there's a high potential that alum sludge could release and get put back into the water,” DPU Director Scott Morris said, speaking alongside Mayor Danny Avula during the press conference. “That's what happened during this time period: the alum was released, and then subsequently in conjunction with some poor raw water quality, that clogged the filters.”

Adjustments to plant operations have already been made, according to Morris, including changes to how the plate settlers in the sedimentation basins are cleaned. The buildup in those basins contributed to clogged filters, water production issues, and ultimately the boil water advisory.

Maintenance procedures are also under review for possible updates or additions to help prevent similar issues in the future. Officials said they are also exploring ways to improve filter performance and speed up response times within the plant.

Morris confirmed that the basin that led to the boil advisory hadn't been cleaned since March when responding to questions from reporters, but declined to identify who was responsible for deferring maintenance, saying that individuals at fault would be held accountable.

Other water issues have emerged since the boil advisory was lifted. A water main break on Canal Street hours after the press conference has caused challenges for Henrico County, leading to the opening of its emergency operations center and a water distribution center at the former Best Products location at 1400 Best Plaza Drive.

During a Friday press conference, Henrico officials said it could take until the evening of Monday, June 2 to resolve the issue, in an effort to avoid impacting water service for residents.