Ten thousand gallons of raw sewage flowed from a manhole in Shelburne and eventually into the LaPlatte River on Thursday night and Friday morning, according to a report from city officials.
The LaPlatte River flows into Lake Champlain's Shelburne Bay.
The overflow was caused by a failure in the power supply of a computer in the pump station that’s supposed to monitor the station’s systems and turn the pump on and off as necessary, according to Shelburne wastewater superintendent Chris Robinson.
The failure took place in the battery backup for the computer, which also serves as a power strip for the computer when the electricity is working. When it failed around 9 p.m. Thursday night, the computer turned off and could no longer monitor the pump or send alarms to operators.
“It’s not able to send out any alarms to say that you lost power at the facility, it’s not able to send alarms to say you’re in high wet well, it can’t do anything,” Robinson said.
Robinson said each of Shelburne’s 19 pump stations are checked three times a week, and operators also conduct a daily inspection of computer communications between pump stations and the central office. He said a check Friday morning showed errors with the station that experienced the failure, so an employee went to the station and fixed the problem by 7 a.m.
In the past month, there have been 14 releases of water that hasn’t been fully treated and disinfected, according to state records. Seven of those were authorized releases that regulators allow when a combined sewer system – one that treats sewage and stormwater – is overwhelmed due to wet weather.
So far in 2015, there have been 24 releases of water that wasn’t fully treated and disinfected.