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Thursday, July 14, 2016

Flooding in Moose Lake area results in sewage release to local waterbodies

Tuesday night, after heavy rains and flooding in west-central Minnesota, the Moose Lake wastewater treatment plant began discharging untreated sewage into Moosehead Lake and Moose Horn River. Sewage was still being discharged as of Wednesday evening. The MPCA Duluth Office has activated a temporary incident command center to monitor the situation and provide assistance to City of Moose Lake and Pine County.  The MPCA estimates 450 gallons per minute gallons have been released from the wastewater treatment plant. 

Discharging untreated or partially-treated sewage can occasionally be necessary to prevent sewage from backing up into homes or damaging wastewater infrastructure during emergencies such as extremely heavy rain events. 
The Moose Lake wastewater treatment plant staff are actively monitoring the lift station pump system's capacity to determine when they can stop the overflow and return to treating all the water coming into the plant. 
The plant operator notified the state Duty Officer at approximately 5:30 p.m. Tuesday night that one of its lift stations was releasing untreated wastewater into Moose Horn Lake. A second call at 8:30 a.m. Wednesday morning disclosed that a second lift station was discharging to the Moosehead River.
People with concerns about how to protect themselves after possible exposure to contaminated lake or recreational  waters should visit  www.mnbeaches.org. This site offers a variety of precautions and actions people can take after contact with water possibly contaminated by bacteria from untreated sewage. 
More information about minimizing flood-related pollution and health risks is available on the MPCA's website.  The page includes assistance for managing household hazardous materials, preparing heating oil tanks for flooding, drinking water well contamination and what to do after the flood.
Sometimes, weather events such as heavy rains and flooding can overload nearby wastewater collection or treatment systems. In some places,  stormwater and wastewater share the same system, which means that large volumes of stormwater will go through the treatment facility. 
In other places, water in saturated ground leaks through aging pipes into the wastewater system. Sump pumps and tile systems discharging to the wastewater system also contribute to the problem.
When something goes wrong, or sewage treatment or collection systems are overloaded, the wastewater must go somewhere. Usually, it either escapes from the collection system or the system operators need to release it, untreated or partially treated. This situation is called a sewage overflow.
Sewage overflows are a "safety valve" to keep sewage from backing up into homes. Municipal wastewater is typically at least 97 percent water. When excess stormwater is added to the system, the sewage becomes even more diluted, but can still contain high levels of disease-causing organisms and harmful chemicals. Sewage overflows should be prevented if at all possible, but when they do occur they can be managed to minimize potential impacts. Things such as the volume and strength (concentration) of the sewage overflow and the volume, flow rate and sensitivity of the water body into which the sewage is sent are taken into account when determining whether an overflow is necessary. 

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