Wastewater treatment tech malfunction leads to sewage spill

May 9, 2023  |  By Lisa Scagliotti 

The Waterbury wastewater treatment plant sits between U.S. Route 2 and the Winooski River just west of downtown Waterbury. It's part of the Edward Farrar Utility District. Photo by Gordon Miller

A computer system malfunction was to blame last week for the release of just over 100,000 of partially treated sewage into the Winooski River from the Waterbury wastewater treatment plant. 

Waterbury Public Works Director Bill Woodruff said that the Supervisory Control and Data Acquisition system – referred to SCADA for short – malfunctioned late on the night of April 24. An alarm that should alert the operator of such an incident was not triggered. 

When the operator arrived early on the morning of April 25, the malfunction was discovered and the system was shut down. 

In the interim, approximately 138,000 gallons of partially treated sewage was released, Woodruff said. The system that malfunctioned has since been repaired, he noted. 

An alert from the Agency of Natural Resources noted the spill occurred between 11:23 p.m. on April 24 until 7:20 a.m. on April 25. It was listed as “partly treated undisinfected effluent” in the category of 100,000 to 500,000 gallons. Woodruff said the volume was close to the low end of that range. 

Woodruff did not have a figure on the cost of the system repair yet.