It’s no secret that Pittsburgh struggles with stormwater management. Public works departments, local organizations and others have grappled with ways to prevent heavy rainstorms from causing flood damage in certain neighborhoods and from contributing to the city’s combined sewer system dumping sewage into rivers. For one flood-prone area, a new green infrastructure project may provide a solution to the problem.
The Highland Park bioswale uses an advanced turf design to divert and manage rain accumulation. Located along Negley Run Boulevard, the 1,100-foot bioswale is expected to intercept between 450-500 thousands gallons of water per year from running into the ALCOSAN sewer shed on Washington Boulevard.
“It has so much water in it all the time that just about any gallon of rainwater that goes into the system causes a gallon of combined sewer discharge,” says David Himes, landscape architect and program associate at the Pittsburgh-based Penn State Center. “Since we’re managing about 500,000 gallons, we’re also reducing combined sewer overflows by that much.”
The Penn State Center took on the bioswale, which was originally part of Project 15206, a now mostly defunct effort to find opportunities for high-impact green infrastructure projects within the 15206 zip code. Spearheaded by former Senator Jim Ferlo in 2014, the initiative took various approaches to stormwater management, such as providing private landowners with 116-gallon rain containers, which were installed by young adults trained through StormWorks and Project 15206 partner organization Pittsburgh Community Services.
Himes says Negley Run Boulevard was chosen because of its susceptibility to chronic, sometimes dangerous flooding (in 2011, a flash flood in the area claimed four lives) and the “sheer volume of motorists and pedestrians moving through that corridor.” They also saw it as an opportunity to reclaim an unused section of Highland Park by having it double as an attractive greenspace.
The effectiveness of the bioswale lies in an accordion-like plastic sheet called a geoweb that, when expanded, reveals cells that can be filled with highly porous soil media (in Highland Park’s case, they used a sandy loam mix).
“What that does is it holds the soil in individual cells so that when water is flowing down it, it prevents displacement or erosion from occurring,” says Himes.
They also placed a woven mesh turf reinforcement mat on top of the geoweb and covered it with a mix of grass hydroseed, mulch and a glue-like tackifier necessary to keep the seed from blowing away.
“What happens is when the seed grows up, the roots are able to go through that mat and through each other and create something that’s highly reinforced,” says Himes. He believes the bioswale grass will be able to withstand powerful water flows, making it less likely to break up and wash away.
While Project 15206 has become less viable, Himes says the Penn State Center is still exploring other projects in places like Larimer and East Liberty, where they’re currently working with groups like the Larimer Consensus Group and the Living Waters of Larimer to educate people about green stormwater management. They’re also looking at ways to deal with a fresh groundwater spring that constantly flows out of a hillside near Meadow Street.
Other plans include daylighting streams that have been culverted into underground pipes and further contribute to the already overwhelmed combined sewer system.
“We’re trying to figure out how we move forward as far as shifting our focus of not building stuff, but helping people build stuff better,” says Himes.
The Highland Park bioswale was made possible by a county infrastructure and tourism fund grant acquired by Ferlo, but, as Himes points out, funding for any future projects remains uncertain. The center plans to look at taking on more partnerships and applying for ALCOSAN’s GROW grant program, which seeks to drastically reduce overflows into the region’s rivers and streams.
Another challenge lies in promoting the understanding that, while so-called grey infrastructure projects, which use pipes, pumps, ditches and detention ponds to manage stormwater, are effective, green infrastructure offers added benefits. Himes points out that they can beautify cities as greenspaces or play spaces, increase habitat for local wildlife, or serve as a place to grow air-cleaning plants.
But while Himes foresees some obstacles down the road, he’s encouraged by the increasing interest in green infrastructure, which the center has been pursuing for almost six years.
“Back in 2010 or 2011, there wasn’t a whole lot of conversation about it,” he says, adding that the approach has gained more momentum with projects like the Pittsburgh Water and Sewer Authority’s City-Wide Green First Plan, as well as work by local advocacy by groups like the Nine Mile Run Watershed Association, 3 Rivers Wet Weather and the Clean Rivers Campaign. “I think there’s a very strong voice for it now.”