As the metro grows, so does the amount of its poop. And that means a major wastewater plant along the Mississippi River in St. Paul needs to grow as well, to burn heavier volumes of solid waste.

It’s a $150 million proposal that adds up to about half the cost of the alternatives but is potentially politically messier: the Metropolitan Council intends to add a fourth solid-waste incinerator to its plant at 2400 Childs Road, about three miles south of downtown St. Paul.

The Metropolitan Wastewater Treatment Plant, which sits across the river from the St. Paul airport, handles 65 percent of the wastewater in the Twin Cities, or 180 million gallons a day. That’s a lot of dirty water — the equivalent of filling 1.8 million bathtubs daily, or U.S. Bank Stadium every three days.

Adding capacity will be no small effort. In fact, given that planning started in 2015, it will be a 12-year push, with construction of the incinerator projected to wrap up in 2024, and improvements to the existing incinerators rolling out by 2027.

The Met Council, the seven-county metro’s regional planning agency, will bring residents up to speed during an open house from 6:30 to 8 p.m. Wednesday at the Wellstone Center, 179 E. Robie St.

‘GENTLER’ INCINERATORS

The plant treats wastewater for 66 communities, and it processes 850 wet tons of solids every day for 73 communities. Its three incinerators would be hard-pressed to keep up with population growth, anticipated to be 500,000 new residents in the service area by the year 2050.

In addition, the facility needs to absorb the work that would otherwise be done by each of the existing incinerators as they are brought offline for fine-tuning from 2024 to 2027.

The word “incinerator” tends to make neighbors nervous, but the Met Council is urging residents to think of them as the gentler, environmentally friendly variety — the kind that do their job so smoothly, many people don’t realize they’re there. In fact, the Met Council has been incinerating solid waste along the river for 80 years, and the three existing incinerators have been online since 2005.

Thanks to modern technology, the incinerators capture and reuse their own energy, which helps heat and power the plant, reduces costs and controls air pollution.

Met Council officials say the fourth incinerator will not generate additional odors or require land acquisition. It will meet air emissions standards and serve as a backup for the region’s seven other wastewater facilities, improving fail-safes in the system.

Officials say construction and maintenance will amount to half the cost of leading alternatives, such as adding equipment to create heat-dried fertilizer.

A public hearing before the Met Council is likely in late summer, with a final vote on the “Solids Management Facility Plan” in late September. To sign up for project updates, email [email protected] or call the project hotline at 651-691-9124.

The Met Council owns and operates 600 miles of regional sanitary sewers, which connect to 5,000 miles of sewers owned by local municipalities. Those sewers collect about 250 million gallons of wastewater a day from 109 metro-area communities for treatment.

The system is funded by user fees, not taxes.