As heavy rain fell across Worcester Thursday, more than 11.5 million gallons of sewage overflowed into the Blackstone River, according to the Worcester Department of Public Works and Parks.
The spill, which came out of an outfall pipe behind Walmart on Tobias Boland Way, was likely made up of untreated or partially treated sewage and waste, the department said in a notification it sent out Thursday.
- Read more: Worcester officials advise avoiding contact with Blackstone River following a nearly 880,000 gallon sewage overflow
The spill started at 12:30 pm and ended at 2:50 pm, the department said.
City officials are advising residents to avoid contact with the river for 48 hours from the time the spill ended, “due to an increased health risk from bacteria and other pollutants.”
The effect of the sewage spill could potentially impact the river in Millbury, Sutton and Grafton in addition to Worcester.
The spills are weather dependent, according to Phil Guerin, the city’s director of Water & Sewer Operations. On Thursday, Worcester saw heavy rain and thunderstorms throughout the morning and into the afternoon.
Spills like Thursdays are not uncommon with the city’s combined sewer system, according to Guerin. The city began sending out notifications announcing the spills this year after a law went into effect on July 6 requiring it.
As many as 20 overflows happen per year, according to Robert Burgess, a spokesperson for the city.
“This action is designed as a relief point for combined sewer systems that carry both waste water and storm water in the same pipe,” Burgess wrote in a statement. “Without the overflow to provide a relief point during high flows (heavy rains) basement backups and street flooding would occur.”
Anyone interested in receiving notifications regarding the overflows can sign up for them on the department’s website.