Special design to address stormwater runoff issues
While newer areas of Calgary are equipped to contain and improve the quality of stormwater, many older neighbourhoods simply don’t have the space to host large wet ponds and constructed wetlands.
In an effort to retrofit older inner-city neighbourhoods, the City of Calgary is piloting a rain garden program to improve stormwater quality as part of its Stormwater Management Strategy.
How a rain garden works
Photo by Katherine CamartaA rain garden is a depression which has layers of specially chosen soils that mimic
the soils of areas where water naturally filters slowly through the ground. Vegetation planted in the depression will absorb nutrients and other elements that would otherwise end up polluting the end water source.
Krista Vopicka, the environmental engineer for the City of Calgary who is responsible for the rain garden pilot program, describes a rain garden as similar to a “pot and kettle” landscape and strive to reproduce the natural water seen in clusters of bushes and trees.
Vopicka noted that the choice of plants and soil will be closely monitored for success over a three-year period. The challenge will be to find plants that can withstand Chinooks. New plants may have to be chosen if the original plants don’t work out. “It’s an art,” she said, referring to gardening in Calgary.
Vopicka said the gardens include metering technology that will show whether the pilot gardens are reducing water volume or improving water quality.
Winston Heights Mountview pilot gardens
The northeast community of Winston Heights Mountview is the site of the first two rain garden pilot projects. Stormwater from this community enters Nose Creek, which is a priority watershed and the City wants to reduce the amount of run-off that enters the creek, as well as improve its quality.
The Winston Heights Mountview Community Hall was in the process of completing a new garden to celebrate its centennial when the community was approached by the City about constructing the experimental garden.
Lifelong resident Linda Sharp, who was active in the development of the rain gardens in 2012, described the community’s experience as very positive.
She said that the avid gardeners are eagerly waiting for spring to see how well the garden has wintered and how it will manage the increased water challenges that come with springtime.
One of the main goals of the Stormwater Management Strategy is to reduce the amount of sediment entering the Bow and Elbow Rivers from the stormwater system.
Polluted runoff carries heavy metals and oil compounds from motor vehicles, loose dirt, nitrogen and phosphorous from construction sites, fertilizers and other materials.
The City of Calgary reports that 75-80 per cent of its stormwater outfall system has no treatment facilities, allowing significant volumes of untreated polluted runoff to directly enter the waterways. The goal is to be at 2005 sediment levels by 2015 despite the fact the city is continuing to grow.
The Winston Heights Mountview garden, which is located in the northeast corner of 520 – 27th Ave. N.E., includes a variety of plants designed to both treat and remove water that would otherwise flow freely into the storm system. The community bore no cost for the garden and, with the proper choice of plants, the garden should become self-sustaining, according to Sharp.
City spokesperson Octavia Malinowski said that the City would not release its costs because the tendering process for construction of the next two pilot gardens is set to close on April 8th. The new pilot gardens are both located in Bridgeland/Riverside.
They also declined to provide the budget used to build the two completed gardens in Winston Heights Mountview, and stated in an email that “making budget costs public during a request for proposal process can lead to the bidders skewing their bids.”
The Capital Regional District, which is the regional government for the southern tip of Vancouver Island, notes on its website that the “costs of building rain gardens compare favourably with conventional stormwater management facilities.”
Bridgeland/Riverside rain gardens
One of the Bridgeland/Riverside gardens will be located in Murdoch Park immediately south of the parking lot of the existing community centre. The other will be in the northeast corner of Riverside Park, directly across from the Bridgeland Seniors Health Clinic at the corner of McDougall Road and 11th Street N.E. Construction did not occur in 2012 as originally planned, when the City elected not to proceed after having received only one bid in its tendering process.
Mark Stout, a Bridgeland resident and volunteer director of planning for the community association said that the City approached the community with the rain garden initiative in late 2011.
Vopicka explained that the consultation process for the Riverside Park garden focused on the senior citizens in the immediate area. Feedback showed that many senior citizens missed having the opportunity to garden, having moved to smaller homes or apartments.
As a result, the garden planning took into account the desire to create not only a functional water quality device, but also a neighbourhood amenity -a garden for all residents.
Stout said the open houses and consultation processes included input from all the demographic groups in the community. He noted that most residents viewed the initiative positively.
“We see it as a gift from the City,” he said. He thinks it will enhance land value and is an innovative way to address the problems arising from polluted stormwater.
Pros and cons of rain gardens
Rain gardens are popular in other cities, particularly in areas with greater rainfall. But they are not without their critics.
Sightline Daily’s Lisa Stiffler said a small but vocal group in the Seattle area had petitioned the municipality to stop the use of rain gardens, claiming that:
- children would drown in the standing water
- mosquitos would successfully reproduce in this new breeding ground
- property values would drop
- the rain gardens would ruin the beauty and quality of life in the neighbourhood
- elderly, young and disabled people would be confronted with the hazards of a steeply sided garden
However, the Canada Mortgage and Housing Corporation encourages Canadians to embrace the gardens to reduce runoff, ensure proper drainage and improved water quality. Without rain gardens, water quality and habitats for aquatic species could deteriorate while shorelines and riverbanks could become unstable.