March 5, 2007

Killer weir to be converted

Suzanne Zwarun

correspondent

Calgary

Normally, a fall on concrete is to be avoided. But after Calgary’s killer weir is remodeled into the Harvie Passage this year “a drunken sailor could fall in, in the middle of the night” says Howard Heffler, “and easily walk or swim out”.

Heffler, a civil engineer and paddler, came up with the idea to turn the 1904 weir, built across the Bow River to divert water for agriculture, from a trap that has claimed a dozen human lives into a safe recreational area for boaters and wildlife.

The weir, a low head dam that causes water to back up and pool behind the structure, creates a powerful recirculating hydraulic wave that emergency rescue workers call a drowning machine.

By constructing concrete and rock structures below the weir, the water level will be backed up to eliminate the deadly recirculation.

Construction of the Harvie Passage means the backed-up water will drop over a series of short swifts followed by calm pools.

Parks Foundation Calgary

The Calgary weir will be converted to the Harvie Passage, providing a safe place for people to paddle down. Additional information and updates on the conversion can be found at www.harviepassage.ca.

Using an existing small island below the weir, the river will be divided into two channels, a gentle south one for average people playing on the river, and a more challenging north one for experienced canoeists and kayakers wanting to practice their skills. Fish, which have had difficulty travelling the river since the weir’s 1975 rebuilding, will enjoy free passage.

Heffler and Harvie Passage project chair Barry Worbets were among the officials who recently presided over the unveiling at the University of Alberta of a $250,000 scale model of Harvie Passage. When constructed, Worbets said, “People will be able to paddle down safely. You’ll have rapids as they looked 100 years ago.”

But not with a century-old price tag. When the project received funding in 2005, the Province of Alberta contributed $3.4 million, the City of Calgary $1 million and the estate of philanthropist Don Harvie donated $2 million through The Calgary Foundation, for a total of $6.4 million.

With all tenders looking to go up 25 per cent, says Worbets, the estimated cost now is $12.5 million. That would buy a lot of concrete but not, it turns out, a lot of rock.

The experts making small replicas of the river and its new passage in a hydraulic slab—the aquatic equivalent of a wind tunnel—evaluated the performance of 19 different designs before deciding the rock and concrete structures needed to be bigger than originally envisioned, says Al Nilson, project manager with Alberta Infrastructure and Transportation. That means more rock and the cost of rock, being transported from 100 km east of Calgary, has soared because of rising fuel costs and drivers’ wages.

Harvie Passage was expected to require 370 cubic metres of standard cast-in-place concrete and 3,000 metres for the grouting.

Project planners are now evaluating whether some of the rock can be replaced with more concrete, which would be cheaper. More expensive coloured concrete has just been ruled out since, as Denver consultant Gary Lacy of Recreational Engineering and Planning pointed out, most of it won’t be visible under the water.

The grouting concrete, however, may have to be steel fiber reinforced since rebar can’t be used amid the rocks.

The Calgary Foundation is still pursuing the extra $6 million needed but Harvie Passage is expected to go to tender in June for an August start on construction.

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