In the early hours of Thursday morning about 879,000 gallons of sewage flowed into Blackstone River, according to the Worcester Department of Public Works and Parks.
The spill, which came out of an outfall pipe behind the 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.
The spill started at 4:23 am and ended at 5:03 am, 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 affect of the sewage spill could potentially impact the river in Millbury, Sutton and Grafton in addition to Worcester.
Spills like Thursday morning’s are not uncommon with a combined sewer system, which the city has, according to Phil Guerin, the city’s Director of Water & Sewer Operations.
The spills are weather-dependent and can happen during rainfall events as many as five to 25 times per year, Guerin said. Some spills include hundreds of millions of gallons of sewage.
Thursday morning’s spill was the result of a very intense rainfall that happened overnight, Guerin said.
While the spills are not uncommon, Guerin said the notifications to the public are new and the result of a law that went into effect July 6.
Anyone interested in receiving notifications regarding the overflows can sign up for them on the department’s website.