The Metropolitan Council of Environmental Services (MCES) is planning an expansion of its metro plant — the largest wastewater treatment plant in Minnesota — located in St. Paul along the Mississippi River. MCES proposes the addition of a fourth wastewater incinerator which requires an amendment to the facility’s current air emissions permit. MPCA is currently reviewing MCES’ request for a revised air permit and considering the potential environmental impacts.
Our role
MCES is conducting a voluntary environmental assessment worksheet (EAW) through the MPCA. The EAW is a process that evaluates the impacts of the proposed expansion. After the EAW is finalized, MCES must obtain an air emissions permit amendment.
MCES has completed dispersion modeling and an air emissions risk assessment as a part of the permit amendment and EAW. Dispersion modeling estimates how far and in what direction pollutants from the facility will travel and how they contribute to pollutant levels that people are exposed to. The risk assessment predicts how this will impact people’s health.
MPCA staff are currently reviewing the application materials to prepare a draft EAW and air permit. The MPCA is meeting with community groups to better explain the proposal, process, and impacts of the expansion.
Project information
The metro plant accepts more than 180 million gallons of wastewater per day, generated by 1.8 million Twin Cities area residents when they flush toilets, use sinks or showers, or run washing machines. The wastewater processing generates 850 wet tons of solids per day that include sludge and other solid objects, which are separated from the liquid wastewater and incinerated. The incineration process eliminates bacteria, generates heat and electricity, and reduces the need for other types of solids disposal. The additional incinerator would accommodate increased wastewater management from population growth in the Twin Cities. There are currently three incinerators on site and the additional incinerator would provide renewal of existing incinerators now and create capacity for the plant in the future when needed in 2035.
After waste solids are incinerated, the air is treated with carbon injection, a baghouse, a scrubber, and an electrostatic precipitator before being released. This equipment reduces pollutants such as mercury, dioxins, furans, particulate matter, heavy metals, and acid gases in the emissions. Pollutants levels in emissions released from this facility are regulated by an air emissions permit.
Next steps and timeline
Individuals can share their concerns, suggestions, and perspectives regarding the proposed fourth incinerator project and its potential impacts. All comments received will be thoroughly reviewed and considered as part of the decision-making process. These comment periods run through August 25. Follow the links to learn more.
The MPCA is also hosting an open house for the community to learn more about the project, draft air permit, and environmental review. The event will be on August 14 from 5:30 – 7:30 p.m. at the Dayton's Bluff Recreation Center (800 Conway St., Saint Paul).
More information
To learn more about how the facility works, visit the Metropolitan Council's website.