Plants Versus Pipes

What can Calgary learn from Philadelphia’s visionary green stormwater infrastructure project?

Every city has a plan for managing urban stormwater, which is the water produced by rain or melting snow. In Calgary, as in most cities, plenty of stormwater falls on buildings and paved surfaces, where it can’t be absorbed. To avoid pooling and flooding, we channel this water through stormdrains into a system of underground pipes that convey the water (and whatever debris it picks up along the way) to the river.

As cities grow, stormwater infrastructure grows with them – usually at considerable expense. But is it necessary, or even desirable, to drain away our stormwater? Can we use this water as a resource in our urban environments? Can we find better ways to protect our rivers from pollution and erosion?

An ambitious stormwater management plan in Philadelphia is addressing these questions. In “With a Green Makeover, Philadelphia Is Tackling Its Stormwater Problem,” published in Yale Education 360 in March 2018, science and environment writer Bruce Stutz investigates the project and its results so far.

Philadelphia is in year seven of a 25-year project to reduce the city’s sewer outflows by 85%. These outflows happen when it rains so heavily that untreated water is diverted into the river. The city had the option of spending $9.6 billion on building more stormwater tunnels, but the price, not to mention the disruption such a massive project would cause, was too great. Instead, Philadelphia decided to try something new, and invested $2.4 billion on “green stormwater” infrastructure – the largest program of its kind in the United States.

“Integrated into the city’s green spaces, streetscapes, and public and private buildings, this green infrastructure ranges from simple home rain barrels and downspout planters to complete bioretention swales underlain by drains, filled with sandy soil, and planted with resilient species of grasses, perennials, shrubs, and trees.”

- Bruce Stutz, Writer on Science, Nature, and the Environment

The Philadelphia stormwater program will create about 10,000 “greened acres,” which are urban acres engineered to manage, rather than drain away, their first inch of runoff. “Greening” infrastructure includes:

  • Rain gardens along portions of the I-95 Highway.
  • “Blue” roof developments (which retain runoff in cisterns and release it to surrounding “green roof” areas).
  • Converting vacant lots into stormwater management parks with native plants and engineered soil.

Already, Philadelphia’s completed green infrastructure (about 1,100 greened acres as of March 2018) is exceeding projected targets for stormwater overflow reduction. The changes have had other benefits, too. Adding so much plant life to “grey” urban spaces helps reduce air pollution and cool the urban heat island effect. It also has aesthetic benefits, restoring greenscapes to underserved neighbourhoods and improving spaces like schools, parking lots, parks, and rooftops (one new parkade has a roof that doubles as a public park).

Stutz points to Panati Playground, a park in a low-income neighbourhood, which received an investment to add green stormwater infrastructure. The investment rebuilt the playground and added rain gardens with perennials, grasses, and planters.

“The $227,000 investment not only gave the neighbourhood a revitalized public space where kids could play within a much-needed greened environment, it also stores 2,700 cubic feet of stormwater from a 37,000 square foot drainage area. The result: three quarters of a greened acre.”

- Bruce Stutz

To support the project’s momentum, the Philadelphia Water Department has developed:

  • A GreenSTEM network that involves students in environmental monitoring;
  • A Green Homes project, and;
  • A youth engagement project that has 18- to 26-year-olds helping with litter collection from green infrastructure sites.

The Water Department is also finding ways to engage the private sector in meeting the city’s stormwater goals. It’s offering private owners and developers financial incentives to redevelop or retrofit properties with green stormwater infrastructure.

The current program in Philadelphia dates back to 1987, when the Environmental Protection Agency ordered the city to reduce its combined sewer and stormwater overflows, which was polluting and eroding rivers and endangering the drinking water. Balking at the expense of traditional pipe-based stormwater management, the city began to consider other options. Today, Philadelphia’s achievements are inspiring, but Stutz’s story emphasizes that it hasn’t been an overnight success – finding new approaches to long-standing urban challenges is a long game.

“It’s a slow evolution of a city, that says, ‘Okay, here we are today in 2018. What do we want the city to look like in 2022? What’s the quality of the rivers, how are our communities built, and how are our assets paid for?”

- Howard Neukrug, former Philadelphia Water Department Commissioner, quoted in Yale Environment 360.

Stormwater Management in Calgary

How are these ideas being applied in our city? Calgary doesn’t yet have a plan as ambitious as Philadelphia’s, but the way our city approaches stormwater management is evolving to include more green infrastructure.

The City’s Stormwater Management Strategy acknowledges the vital importance of the Bow and Elbow rivers as sources of drinking water for Calgarians. Rain and snowmelt, channeled directly into the rivers, can carry runoff from buildings, roads, and construction sites into our watersheds. A 2005 study revealed that 90% of sediment that entered the Bow River from Calgary got there via the stormwater system.

The City supports a strategy of Low Impact Development, or LID, which treats rainfall and snowmelt like resources instead of waste products. This type of development works with nature to manage stormwater by preserving natural, water-absorbent features wherever possible and minimizing hard surfaces. When more water is absorbed where it falls, less water flows into our waterways – and the water that does make it to the river is cleaner. LID practices include:

Here are a few sites in Calgary where you can see green stormwater infrastructure at work.

City of Calgary Water Centre: This Ramsay building, which was completed in 2008, is designed to reuse stormwater and grey water. The LEED Gold-certified structure also has a green roof, grass and vegetation placed to limit runoff, and a porous parking lot that allows rainwater and snowmelt through.

University District: When this master-planned northwest community is completed, it will include a stormwater system that incorporates permeable pavements in 75% of hardscaped public spaces, as well as rain gardens, bioswales, and a naturalized wetland.

Quarry Park: This southeast community on the banks of the Bow River worked with Westhoff Engineering Resources to develop a stormwater management system that includes a flood mitigation pump system and a linear stormwater pond and creek system that cleans water before channeling it into the river.

Ralph Klein Park: As a response to water quality concerns in southeast Calgary, the City took its cue from nature. The Shepard Wetland at Ralph Klein Park, which opened in 2011, serves as a stormwater storage facility and a natural filter for rainfall and snowmelt before it flows to the Bow River. It’s the largest constructed stormwater treatment wetland in Canada, and it’s also an environmental education centre and a habitat for waterfowl.

Mahogany Wetland: When this southeast greenfield community was planned, it included a 75-acre constructed wetland. This natural area now serves as a wildlife habitat and as a stormwater retention and filtration system.

Bebo Grove: As part of the Woodland Woodbine Community Drainage Improvements project, launched in 2010, Fish Creek Provincial Park will gain a storm pond in 2020. The pond/wetland will be constructed in the Bebo Grove day use area, and its presence will help prevent flooding in the area and help filter the runoff water the ends up in Fish Creek.

Echo Haven: In this northwest Calgary eco-community, there are no storm sewers. Instead, stormwater is retained and used to contribute to the health of the ecosystem.

One of the seven goals of Calgary’s Municipal Development Plan is to build a greener city. Re-thinking the way we manage stormwater – with inspiration from cities like Philadelphia that are exploring innovative solutions – is a step in the direction of sustainability. The addition of beautiful rain gardens and green roofs will be an added bonus.

June 14th, 2018
Updated: June 25th, 2018

Taking a green approach to stormwater management.