A Foothold in Nature

Summer 2015

Concrete pavers a material of choice for Calgary’s 31-acre urban island oasis

Alicia Lasek

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A Foothold in Nature


A once-popular park in the center of Calgary, Alberta, received a reprieve from dereliction when 6,000 residents responded to a Calgary Municipal Land Corporation survey on re-development options. The overwhelming response was to return it to an island park oasis reminiscent of its fondly remembered glory days as a wooded campground and recreation site. Thus began the revitalization of the 31-acre St. Patrick’s Island Park on the Bow River in the heart of Calgary.

Unveiled to the public on July 31, 2015, the $20 million renewal of the regional park features restored natural habitat with native plantings and wetlands accessible by trail, a boardwalk and walking trails. A river channel was dredged and restored to its natural state to allow access for waders, water play and rafting, plus a woodland habitat was re-established for nesting hawks, owls and other birds. With the natural environment being the soul of the project, designers kept the human footprint light while providing an amenity-filled, family-friendly park that encourages year-round use by city dwellers. Amenities include play, picnic and viewing areas; walking, running and bike trails; pavilions surrounding two event spaces and pathways that can accept small (up to 1-ton) utility, maintenance and emergency vehicles.

“The project team took a biophilic approach in terms of development,” says Susan Veres, VP, marketing and communications with project owner Calgary Municipal Land Corporation (CMLC). “Biophilia, literally translated, means a ‘love of life’. The concept is based on the theory that there is an inherent human need to interact with nature. In fact, studies have shown that people’s physical, mental and spiritual well-being is tied to the natural environment. In the context of St. Patrick’s Island Park re-development, that means looking at the island from its natural state, its physical location in the Bow River, and how, from an emotional state, Calgarians wished to experience the park.”

MATERIALS OF CHOICE

The surface materials of choice for this island oasis include 65,000 sf (6,000 m2) of concrete paver ‘planks’ measuring 445 mm long, 100 mm tall and 70 mm wide, set in a running bond pattern with random color distribution in three grays. The pavers are prominently used in two key areas of the island: Confluence Plaza (an event pavilion and amphitheater area named for the island’s location at the confluence of the Bow and Elbow Rivers), and at the Seasonal Breach area near the landing of St. Patrick’s Bridge. St. Patrick’s Bridge opened in October, 2014, as a pedestrian and cyclist access route across the Bow River. Portions of paver pathways meander throughout the island. The design creates unique, seamless transition details in the many, varied edges where the pavers join the park’s other surface materials, including gravel and clay mix on trails and wood decking.

TRIED AND TRUE

When starting on the island design, CMLC and city stakeholders were already familiar and comfortable with the aesthetic and practical benefits of concrete pavers, says Ms. Veres. The island project is part of a larger, 20-year infrastructure improvement program being delivered by CMLC throughout Calgary’s Rivers District Area in the east end of Calgary’s downtown. The lion’s share of CMLC’s work is a master-planned community called East Village, a 50-acre brownfield site reimagined for mixed-use, high-density development that serves 11,500 residents, and is planned in response to exploding city population growth driven by oil and gas development.

A key element of the East Village streetscape is about 31,000 square meters of L-shaped concrete pavers used to establish sidewalks and road carriageways with a cobblestone effect—the first large-scale use of concrete pavers in the city, says Ms. Veres. While the initial installation cost of the pavers was relatively high compared with some of the design team’s other options, that cost has since been more than outweighed by ease of repair and maintenance, and by the fact that the streetscape serves as a unique selling proposition to developers and residential buyers. “They’ve attracted interest, set a standard of quality we were seeking for this community, and helped set the tone for the larger project,” said Ms. Veres. After years of working on the East Village, CMLC’s contractors had a wealth of experience with the materials, she adds. “It was easy for us to imagine how the pavers might add to the experience and aesthetic of St. Patricks’ Island Park. We tested them and had success.”

Chosen in part for their experience with waterways, design firms W Architecture of New York City and Civitas of Denver envisioned a naturalized environment and modern amenities fitting together without too much visual contrast—a challenging design task, says Martin Barry, ASLA, associate with W Architecture. That led to the choice of paver planks for a linear look with texture created by a tricolor scheme, he explains. “It elongates the smaller spaces, while shrinking the scale in others. The result is some places have more of a feeling of expansiveness, where in others, there are big pauses.” While even longer pavers were an option, Mr. Barry says the paver length on the island project was limited to 18 inches to protect against potential cracking under occasional use by light-utility vehicles.

Pavers were also chosen for their ability to withstand Calgary’s climate, including bitterly cold winters and year-round sun. In addition to creating an even visual flow, the paver colors, in natural gray, medium gray and charcoal, were chosen partly for their high reflectivity to minimize heat-island effect, Mr. Barry says. The system is also designed to be entirely permeable, accepting and filtering stormwater just as the surrounding environment will do naturally. Calgary is flood-prone with the Bow and Elbow rivers running through it. While it is unlikely that St. Patrick’s Island will find itself underwater again anytime soon—as it did in a massive 2013 flood caused by a 100-year weather event—the permeable paver system fits neatly into the larger project’s necessarily water-friendly design, say stakeholders.

SEAMLESS TRANSITIONS

The paver design creates appealing, seamless connections to natural materials, such as wooden decking and trail surfaces, Mr. Barry says. “The flush transition from hardwood tropical decking onto the concrete pavers, and the color variation between the two, is really quite beautiful. Where the pavers intersect with trails of decomposed stone, a very nice transition is achieved with the soft material butting up against the hard.”

“The choice of a running bond, random color distribution was a core component of these many, varied transitions when it came to installation,” says Mr. Barry. “We used these pavers [in another project] with a stacked random bond color distribution, and it was tough keeping the pavers in a straight line on a big plaza,” he explains. “When using linear pavers, I recommend being careful of the kind of alignments and patterns, as they can be limiting. Using the running bond on St. Patrick’s Island allowed us much more flexibility.”

Local landscape architecture firm IBI Group collaborated with designers on the choice and placement of native plantings and other softscape materials. They were pleased with how the pavers’ flexibility allowed edges to blend well with the natural environment, says Garth Balls, senior landscape architect, associate, IBI Group. “We wanted the natural vegetation of the island to be the focus for visitors. There is very little manicured grass on the island. Where the pavers end and the landscape touches, the long, narrow paver creates an attractive pattern that is very compatible with the plant material and doesn’t draw too much attention to itself.”

INSTALLATION KNOW-HOW

Experienced with previous paver installation in the East village project, Marmot Concrete created attractive transitional edgings in the park. After excavation of some areas, the base installation was a relatively simple project, says Cameron Smith, project foreman. “There are a lot of underground water systems with drain rock and river stone on the island—all good building material. We just had to strip off silt and loam and away we went, with the base and bedding.”

Then there came a learning curve with hand installation due to the random paver pattern. “We wanted nice straight lines and bisecting angles, while keeping the pattern tied together when we went around obstacles. Working with long, skinny pavers and cutting that with steep angles made that a challenge, but it went well,” he says. On Confluence Plaza, for example, the pavers flow around the amphitheater and stairs, and tie to precast seating. Paver-surfaced finger pathways meander through the park as well as tying into the pedestrian bridge at the island’s west end where they direct visitors in two directions, to an elevated breach walk and a low-water crossing.

The Marmot team experimented a bit with some patterns prior to getting started, Mr. Smith adds, but in the end the designers chose the random pattern, so the logistics were pretty simple: Due to the size of the project, manpower needs were significant. Marmot had 15 workers installing pavers full-time prior to the July grand opening.

“To know the island [before] and to know it now—the change is truly remarkable,” says Ms. Veres. Adds Mr. Barry, “We are calling this project the ‘emerald jewel’ in the Bow River and of downtown Calgary. It’s great to have an environment that provides hard plaza spaces for recreating, and having festivals and fairs. We were able to concentrate those and use more open space for looking at the city views, standing where the water comes through the site, or tobogganing in the winter. It’s remarkable to be involved in a project that gives such a variety of spaces for Calgarians to enjoy year-round.”

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