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August 26, 2013

Calgary weir closed to repair flood damage

FILE PHOTO

A detailed inspection of the Harvie Passage is scheduled for Aug. 29, which will allow further decisions to be made about the repairs that need to be undertaken, before it is returned to working condition and re-opened.

The Calgary Weir on the Bow River has been closed to the public to undertake an assessment of flood damage and develop a plan to repair the structure.

“The concrete structure comprising the Harvie Passage experienced significant erosion during the flood,” said Jacalyn Ambler, spokesperson for Alberta Environment and Sustainable Resource Development. “There are significant gravel and silt deposits in all the channels of the passage and upstream of the weir. There is damage to sections that divide the passage into channels for different types of rapids. We also have a new channel, which has formed on the right side of the bank, which changes the overall configuration of the river.”

Crews from the Calgary Fire Department and the Government of Alberta installed a safety boom upstream of the Harvie Passage on Aug. 17, because exposed pipes, loose rocks, and damage from the June flood have made the passage too dangerous for use.

Ambler said an initial visual assessment of the passage was undertaken on July 31, because visibility is still limited due to high levels of water and silt.

This inspection revealed significant gravel deposits in the channels and damage to the structure of the passage, including the island that divides the river into channels for boating.

There is also damage to the access roads that lead to the passage.

Water levels in the passage have decreased since the flood, but it remains extremely dangerous due to obstacles and debris.

The passage is turbulent and difficult to navigate, even under ideal conditions, which means it is only safe for use by experienced boaters.

For this reason, a safety boom or large buoyant barrier was installed across the river at the entrance to the passage.

The safety boom will alert boaters to the closure and cut off access before conditions become unsafe.

A more detailed inspection of the passage is scheduled for Aug. 29, when visibility is expected to improve.

This will allow further decisions to be made about the repairs that need to be undertaken before Harvie Passage is returned to working condition and re-opened.

For example, the new channel that has been created on the right side of the river’s bank may be restored to its original condition or incorporated into a new design.

Ambler said the plan to re-open Harvie Passage is still in the early stages and no information is available about the procurement process for undertaking the repairs.

The Calgary weir, which was built in 1908 to divert water to the Western Irrigation District, is an important source of water for southern Alberta residents, farmers and industry.

The strong undertow of the original design made the area dangerous for boaters and recreation users, which resulted in the structure being known locally as the drowning machine.

For this reason, a $16.6 million contract was awarded to DeGraaf Excavating Ltd. of Lethbridge in late 2008 for the Calgary Bow River Weir Project.

The main purpose of the project was to redevelop the weir and eliminate the extreme drowning hazard that it created, as well as enable river passage for non-motorized boats and fish.

The project also maintained the Western Headwork’s primary function of facilitating diversion from the Bow River to the Western Irrigation District.

The new design created two channels. The larger main channel, rated as a Class III rapid, is suitable only for trained whitewater kayakers and river rafters. A smaller, less turbulent Class II rapid is located on the south side of the river.

The project was privately funded with a significant contribution by the Harvie family, which is why the Calgary Bow River Weir Project is named Harvie Passage.

Financial contributions were also made by the Calgary Foundation, the City of Calgary, the Alberta Lottery Fund, Alberta Environment, and Alberta Transportation.

Klohn Crippen Berger Ltd. (formerly Mack, Slack & Associates Inc.) was retained by Alberta Transportation in 2006 to undertake the final design, contracting services, construction contract administration and resident engineering services.

The project was undertaken by Klohn Crippen Berger Ltd., in association with their hydraulic and ice subconsultant, Northwest Hydraulics Consultants, and their recreational hydraulics subconsultant, Recreation Engineering and Planning.

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