6-acre meadow on top of Vancouver, BC, building
By KATIE ZEMTSEFF
THE SEATTLE DAILY JOURNAL OF COMMERCE
SEATTLE -- Vancouver, B.C., is home to one of the largest green roofs in North America: a 6-acre behemoth bigger than four football fields on the edge of a busy metropolis. But when you're up on the roof, it's like you are in a quiet meadow surrounded by urban land.
Few people get up onto the Vancouver Convention Centre West roof. Bruce Hemstock, a partner at the landscape architecture firm PWL Partnership, said it is closed to protect the new habitat and creatures that live there. The roof is home to four beehives, other insects, birds and rodents.
It is big as green roofs go, but not as a habitat. Visitors, even in controlled areas, would have destroyed living spaces, he said.
"We looked at it long and hard, and thought we can exist as humans on streets and enjoy it," he said. "Here's one spot where if we didn't go up there, we'd really be creating something special for the birds and the insects."
When we develop cities, Hemstock said, habitat is lost for organisms we don't often think about, like insects and bees. The green roof gives some land back to animals in the urban core, while also addressing issues like the heat island effect and stormwater runoff.
Closing the roof presented a challenge: how to demonstrate these grand ideas if people can't see them?
First, the team placed the beehives in a visible place. When visitors reach the top level of the center, they can look outside and see part of the roof with the hives.
Second, the team built an identical but smaller green roof on another building on the west side of the convention center plaza where visitors can experience the way the roof feels while seeing the larger roof nearby. Visitors can take an elevator up three stories and touch that 20,000-square-foot roof. The center also plans to put a restaurant in the building.
Vancouver Convention Centre West received LEED Canada platinum certification, the first convention center in the world to do so, and won a number of awards.
The convention center roof is watered in June, July and August when soil sensors show moisture below 20 percent. It is irrigated using treated blackwater from the building. Waste from toilets flows to a treatment center on the lowest level where it is cleaned by a series of filters. The cleaned blackwater runs to the roof in warm months, or is reused to flush the toilets again, moving in a continuous loop. Hemstock said he encourages people to use the restroom often at the convention centre.
Last summer, the roof went through its first warm season. Though it was one of the driest summers on record, the roof flourished. LEED rules allow for watering roofs in their first season. Hemstock said grasses got to be 30 inches high and everything went to flower faster than the team had anticipated.
"It looks like its been there for 30 years," he said. "It was pretty amazing."
The roof has 400,000 indigenous plants, 120 kilograms of seed and 80,000 planted bulbs. Grass gets cut once a year in the fall.
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http://www.seattlepi.com/local/6420ap_wa_big_green_roof.html
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