The City of Milwaukee recently received a $1 million grant from the EPA to build rainwater absorbing streets.
Starting in May, workers will begin replacing a few blocks of sideways, driveway skirts and alleys near downtown and a stretch of North 72nd Street with porous pavement.
Ghassan Korbun, Commissioner of Milwaukee's Department of Public Works, oversees the city's 14,000 miles of road and 4,000 alleyways. "Not to mentioned the square yards of sidewalk,” he adds.
Korbun says Milwaukee began exploring green storm water management options years ago. “The city received its first storm water discharge grant through the EPA in 1987. The initial approach was to build ponds,” Korbun says.
Storm water retention systems work well, Korbun says, but the city doesn't have much space available to build more. So the city began approaching sidewalk and curb projects strategically.
“When it’s time to replace a street, walkway or alley, we’re adding the storm water management element to it at a lesser cost and being efficient and smart about it," Korbun says.
“When it rains, all the water sheets over the driveway and sidewalk, makes it’s way to the gutter and eventually to the catch basin and it goes into then storm water main. What we’re trying to do is slow down that process,” Korbun says.
To slow down the rainwater, DPW plans to replace the sidewalk between the driveway and its skirt with a porous pavement system.
“There will be a layer of stone underneath the new porous pavement, and that stores water. A similar layer will placed underneath the concrete approach. And then at the curb and gutter we will add another layer of stone,” Korbun says. This new pavements will also store and filter the water.
“And whatever water that makes it to the catch basin will be cleaner and there’s much less of it,” the commissioner adds.
When a light rain falls, Korbun says practically all the water can be absorbed into the earth through the porous system.
“If, however, you have a two-inch rain in one hour, some of it will not be stored. In that case, more will make its way into the storm water catchment system,” he says.
Korbun says the city is also taking a unique approach to create green alleys.
“We will use porous pavement for the middle four-foot strip and under the entire width of the alley we would have a layer of stone, anywhere from 1 to 2 feet deep, depending on the condition of the soil. Whatever that can not be contained will make its way into the basin through a pipe installed underneath the pavement,” Korbun says.
Korbun has studied, and says he has learned from other cities’ green storm water management strategies.
“Chicago has done a lot of green alleys at a much larger scale, pouring the entire width with porous, which I think is very inefficient and expensive. We’re sticking with the four-foot middle section to limit our costs,” Korbun says.
He predicts costs will gradually come down and green infrastructure will become more common. Korbun hopes Milwaukee will prove to be a poster child of “green” and will attract more EPA and other infrastructure grants.
“Other cities, as far as I know, don’t have a porous sidewalk program like we do, so hopefully we’re pioneering this effort,” Korbun says.