Hundreds of millions of gallons of stormwater flow into Pittsburgh’s sewer system during hard rains, which results in chronic flooding and sewage backups. A massive green infrastructure project slated for Four Mile Run could significantly reduce those problems, Pittsburgh Water and Sewer Authority officials said.

The multiyear initiative will evaluate and manage stormwater across several neighborhoods—Greenfield, Hazelwood, Oakland, Squirrel Hill—and Schenley Park. At a community meeting Monday night PWSA’s executive director Bob Weimar introduced the project by starting with the big picture.

“Most of you already know that we’ve got a stormwater problem. How many people know we have a storm water problem?”

Almost every hand in the room went up.

“It’s fair to say that this is a systemic problem.”

Pittsburgh has a combined sewer system. That means when it rains hard, stormwater overwhelms the system. Sewage winds up going to ALCOSAN’s treatment plant, into the rivers and backing up in people’s basements. It’s expensive and unhealthy.

The Four Mile Run project will capture stormwater to bypass the combined sewer system. The work is expected to mitigate chronic flooding in the Run, a low-lying part of Greenfield.

That water can be an asset instead of a liability, said James Stitt, PWSA’s sustainability manager.

“Rather than fighting with the water to put it somewhere that it doesn’t want to be, let’s work with the water,” he said. “Utilize the fact that gravity’s going to put it down there whether we want it there or not.”

The project will direct the water to the Monongahela River, either underground through a tunnel or above ground through an open channel.

More detailed plans are expected at the next meeting on November 15, and work is expected to begin in 2020.

The project is separate from plans for transit facilities proposed by Pittsburgh’s Department of Mobility and Infrastructure.

The Mon-Oakland Mobility Plan envisions on-demand shuttles that would run between Oakland, Greenfield and Hazelwood by way of Junction Hollow and Schenley Park. The project remains in the planning stages.

PWSA’s Weimar said the authority’s work is being coordinated with all city agencies, but the green infrastructure project is the main priority.

“The intention for us is to make the stormwater components the most important,” he said. “Once we’re done developing our plan, then they’ll come back and determine how they can fit in whatever needs they have.”