Green Infrastructure Helps Manage Water In Milwaukee's Urban Landscape

May 9, 2019

Rainstorms are a challenge to clean water. They can cause flooding and potentially damaging runoff. But utilities, landscape architects and others are finding solutions — visible everywhere from the county grounds to your neighborhood ice cream shop.

In 2011, MMSD built a large basin on the Milwaukee County Grounds. It's a 17-foot-deep sunken pool with grassy walls that, when full, looks like two connected natural lagoons. The basin can hold up to 315 million gallons of water.

» See More Project Milwaukee: Great Lakes, Troubled Waters Reports

An MMSD floodwater management project at the Milwaukee County Grounds in Wauwatosa.
Credit Maayan Silver

Tom Chapman, project manager for the Milwaukee Metropolitan Sewerage District (MMSD), says the intent of the project is "to store the water upstream so that it’s not in the flood plains, flooding structures downstream."

"Depending on the size of the event, it could take a day or longer to fill up, and then it’s held back here for a number of days and released slowly through an outlet structure on the downstream side of the basin," he says.

The excess water is released gradually into the Menomonee River so it doesn’t flood nearby homes. And capturing the rainwater reduces the probability that MMSD will have to release partially treated sewage into Lake Michigan. That can happen when the sewage system is overburdened and the treatment plant can't keep up.

MMSD has constructed a number of other projects of this scale. The biggest measure to reduce so-called sewage "overflows" into the lake is the Deep Tunnel. It's a nearly 30-mile long structure that began operating in 1994.

The tunnel collects untreated sewage and storm water during heavy rains, storing it until it can be treated. Before the tunnel, the region used to have 50 to 60 overflows every year. Now, with the completion of the Deep Tunnel and other projects, the average is one to two overflows.

But not everything that manages how water flows is so large-scale, says Chapman. Take green infrastructure.

READ: 5 Ways You Can Conserve Water At Home

“Green infrastructures is managing stormwater where it falls by holding it back in small depressed areas called rain gardens or bioswales that are constructed that hold back stormwater from a property," says Chapman. It also includes porous pavement, rain barrels and other creative measures.

There is green infrastructure all over Milwaukee. Chris Carr engineered the rain gardens outside Purple Door Ice Cream in Walker’s Point. Built for the city of Milwaukee, the rain gardens are grassy ditches landscaped into the sidewalk. 

A rain garden next to the Purple Door Ice Cream Building in Walker's Point, built for the city of Milwaukee.
Credit Maayan Silver

“The gutters come down and then get dumped into the rain garden, along with any water that doesn’t go through the porous pavement," he says. "There are specially engineered soils in here that naturally filter the water. So, there's 2-to-3-feet of engineered soil and then a gravel bed underneath there.”

Carr says the rain garden cleans the water and slows it down. Similar to what a wetland would do.

Green infrastructure is meant to reduce water pollution and improve water quality in Lake Michigan and local rivers, says Pam Ritger. She's a staff attorney with Clean Wisconsin. She consults with the sewerage district, and says the utility developed a regional green infrastructure plan in 2013.

“The goal of that plan is by 2035, if we’re able to capture the first half-inch of every rainfall in green infrastructure, that should eliminate combined sewer overflow events and basic back-ups,” she says.

But it’s not just public utilities and governments that are playing a role.

Paul Vandeveld co-owns an apartment building on Milwaukee’s east side. He points out two deep raised wooden boxes in the front yard, with plants, adjacent to two rain gardens at ground level.

Close-up of a StormGUARDen, which is usually planted with native flowers and plants.
Credit Maayan Silver

"Well, we are diverting the water out of the former downspouts which led in to the city’s combined storm and sanitary sewer system and we’re basically storing the water and using it to water plants in these oversized flower boxes," he explains.

Any excess water from the flower boxes flows into the rain gardens. The system can manage 1,000 gallons of water per storm. Vandeveld is aware of the potential for overflows into Lake Michigan.

“We just want to do our small part to help prevent that or at least reduce it a little bit,” he says.

Civil engineer Carrie Bristoll-Groll planned and installed the raised plant beds, called StormGUARDens, and rain gardens on Vandeveld's property.

Laterals on the building usually connect the roof's gutters with the underground sewer/stormwater system. But green infrastructure can absorb the rainwater where it falls.
Credit Maayan Silver

She says replacing the building’s two laterals — they take the water from the roof's gutter into the ground where it enters the sewer system — would have cost $10,000. Instead, she says the StormGUARDens were installed for $2,000 each.

"And the rain gardens are roughly about $250 for the excavation and installing plants," she adds, "so he spent about $5,000 here — half the cost."

But it does take investment to implement green infrastructure at a large-scale, says professor Dick Luthy of Stanford University. He's a professor of civil and environmental engineering.

Historically, he says green infrastructure has been underfunded. But he thinks education works.

"When people understand the advantages of green infrastructure, in terms of providing community amenities, literally greening the city, helping to prevent contaminants from entering the waterways, there’s a lot of support for it," he says.