Sanitary sewers. They could be likened to your digestive system. When something’s amiss, they’ll let you know. On those rare occasions, it could be in the form of a backup into basements or a discharge into lakes and other waters. Or, like last summer, the evacuation of residents on and near the University of Minnesota's Minneapolis campus due to an explosion.
Metropolitan Council officials tell residents the only things that should go into the sewer system are the three Ps: poop, pee, and toilet paper. Last summer, however, the discharge of a flammable liquid into the system resulted in a fraternity house fire, a flood of emergency responders, a mass exodus of residents with, fortunately, no injuries, and a series of actions to avoid a repeat occurrence in the future.
Public safety is the top priority
“Public safety has been the driver since Day 1,” said Ned Smith, a director in our Environmental Services division who oversaw the Met Council’s response.
An ongoing partnership with local officials resulted in key measures, Smith said, including:
- Daily monitoring of the sewer for concentrations of gas and vapors
- Suspension of discharges from a company upstream that recycles fuel
- Installation of meters that will alert safety officials if the concentration of a flammable substance reaches a certain level.
The regional sanitary sewer system is a vast network of hundreds of miles of Met Council-owned interceptors that connect to thousands of miles of locally owned sewers in the metro area. Together, and deep underground, they flow hundreds of millions of gallons of wastewater every day to nine metro treatment plants.
Industrial users need discharge permits
Among the residential and business customers that discharge into sanitary sewers are companies that release industrial waste into the system. Their discharges require Met Council permits to ensure the system can safely accommodate the materials. About 900 permits are in effect today in the metro area.
Met Council officials say these industries provide important services and products and are monitored so any inappropriate or illegal discharges are brought into compliance or otherwise remedied.
In the case of the June and August 2022 discharges, staff from multiple agencies fanned out across an area of several hundred acres to help identify a likely source of the discharges. Once identified, the discharge was discontinued until procedures and pretreatment equipment are in place to ensure the discharge complies with the company’s permit.
Out of sight, out of mind
“Sanitary sewers, for all intents and purposes, are out of sight and out of mind,” said Smith. “Day in and day out, this sprawling and nearly invisible infrastructure allows us to flush and drain without worry and helps to protect our water quality and public health.
“An event like last summer’s is a reminder to us all to call 911 if we smell gas or chemical odors. Not only for safety purposes, but to help trace and identify potential sources,” said Smith.