St. Paul | Metropolitan Council of Environmental Services incinerator expansion

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 includes 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

When the EAW and draft air permit are ready, the MPCA will host formal public comment periods. We'll review any comments received and, if necessary, make changes to the EAW or permit. We'll then decide whether to issue the air permit. We'll only issue the permit if the facility meets all applicable requirements. Dispersion modeling has shown that MCES can meet state and national ambient air quality standards.

More information

To learn more about how the facility works, visit the Metropolitan Council's website.


Kirsten Barta
Environmental review
Bruce Braaten
Air permit