The City of Northfield has concluded its internal investigation into the Wastewater Treatment Plant discharge from July 22, 2019 in which a maximum of 5,500 gallons of wastewater was released into the Cannon River. The investigation revealed that the discharge was due primarily to the City of Northfield’s scum pipe at its wastewater plant being turned allowing more wastewaster to fill tanks and failure of an automated equipment alarm notification.
Director of Public Works David Bennett has indicated “unfortunately we had a series of events at the plant that lead to the ultimate discharge, but such events can be prevented in the future.”
As a result of the internal investigation findings, the City has corrected settings to alarm monitoring systems that failed, ensured that the scum pipe will be sufficiently turned, and established updated procedures related to regular maintenance and monitoring of certain wastewater plant components.
Staff notified Minnesota Pollution Control Agency immediately and took water samples. The results show higher levels upstream of the plant than below where the release occurred. The release was immediately stopped that morning and tests confirmed there were no public health concerns related to the release into the Cannon River. There were not any public health concerns as a result of the release. According to Utilities Manager Wagner, “The river, at the time, was in flood stage flowing at a rate of about 48,000 gallons every second. The discharge occurred over about a 2 1/2 hour period (.6 gallons per second) so there was approximately 80,000 times more other river water flowing through the Cannon River every second than the discharge as it actually was flowing out.” Public Works Director Bennett commented that “the wastewater, at the time, was extremely diluted due to the total river water flow that really minimized any potential environmental or public impacts from this discharge event.”
The incident comes approximately one year after a series of three unrelated incidents including a damages related to a temporary maintenance pipe plug failure, a fire in a biosolids building, and a pipe break ultimately leading to plant damages and a related plant discharge. City Administrator Martig indicated that “although these are unrelated incidents, we have been proactive to explore a full operational and facility analysis for the wastewater treatment plant to ensure we have best practices and procedures in place related to our operations and that the facility is operating as they should.”
The City will also be completing a new multi-year facility improvement plan study in the coming months. “The City has completed millions of dollars of repairs over the last year and a half as a result of the damages which fortunately are heavily being covered by our insurance,” said Martig. The improvements have accelerated other replacements that had been scheduled and the new facility improvement plan study expected to be completed in early 2020 will identify new priorities for plant maintenance as well as upgrades.
Today, at the August 5, 2019 regular City Council meeting, the City Council will consider approval of a contract with Jacobs Engineering. Jacobs Engineering is a nationally recognized independent engineering company that specializes in wastewater treatment services, to complete a study of the Plant.