Eight years after the flood, the District of Squamish seems to have finally realized that dike seepage is one of the most pressing public safety issues facing Squamish when it comes to the Squamish River Dike.
At a committee of the whole meeting on Tuesday, Feb.8, Squamish council authorized $900,000 from the 2011 Capital Budget to fix potential seepage issues on the eagle viewing area of the Squamish River dike on Government Road.
"This is a high priority," said Brian Barnett, the district's general manager of engineering and parks.
"We will proceed with this work immediately."
Barnett said he was confident the project would be completed within the year. The staff recommendation to spend close to a million dollars on fixing potential seepage issues came after the council received a 2008 report called "Geotechnical Assessment of the Squamish River Dikes" prepared by Thurber Engineering Limited.
The Thurber report found that the Squamish dike was not built according to provincial standards. The permeable material used to build the dike rendered it susceptible to water seepage and piping during the event of flood. Piping is the next, more ominous stage of seepage: water creates a pipe as it removes the gravel while seeping through the dike, eating away at it until it finally collapses.
Thurber's report narrowed the area of concern of seepage to the eagle viewing area of the dike on Government Road in Brackendale.
Two Squamish geoscientists, Frank Baumann and Pierre Friele, were witness to seepage in that area and had a taste of the potential devastation seepage could have done to the dike around the Eagle Viewing area during the flood of 2003.
"The water was coming out in little volcanoes on the Eagle View and Judd Slough sections of the dike. It was boiling," said Frank Baumann.
"You could see the water was turning muddy and we knew that piping was coming."
Baumann and Friele, too, prepared a report on the flood, which they submitted, to the then Squamish council.
"In our report to the council in 2003, we identified water seepage as one of the highest priority issues that needed to be addressed," Baumann said.
Thurber's report had the same clear warning for Squamish.
"Prevent internal erosion/piping that results in boiling, which is the most critical condition that will lead to imminent dike failure," stated the report.
The Thurber report has three suggestions on how to control future dike seepage: Construct a berm (an extended slope) on the landside of the dike, create the same berm on the river side, and finally, combine a land-side berm with a mid-seepage diking barrier, which involves installing a sheet-pile barrier along the dike crest.
Squamish plans to follow the third suggestion.
In addition to physical upgrades to the Squamish dike, Thurber's report also recommends surveillance of the dykes during all major floods and maintaining stockpiles of pit run gravel and sand bags, which can be used in case of excessive seepage.
In the past few years, the district has spent hundreds of thousands of dollars on dikes: assessment studies, Sea Dike extension on the Mamquam Blind Channel, replacement of aging pumps on the Judd Slough, flood gates upgrade at 3rd Ave., portable pumps and generators for power backup, and drainage work at 4th Ave. and Main Street in downtown Squamish.
It also secured a Building Canada funding grant of $425,000 which it used towards adding riprap (rock used to armour shoreline) on a 350-metre section of dike on the Squamish River upstream of Fisherman's Park.
Recently, the council was also presented with another report on dikes by its primary consultants, Kerr Wood Leidal, which recommended that the district remove sedimentation and raise the height of the dike in some areas.
Despite investing heavily on the dikes, it's unclear how a report on as crucial an issue as dike seepage was ignored for almost three years. If the same report had been presented and acted upon in 2008, it would have saved the taxpayer almost $300,000.Thurber's report estimated the cost or dike upgrades in 2008 to be $630,000.
Concerns have also been raised in the past by residents who live along the dike about the excessive vegetation on the dike. In the event of flood, tress and vegetation tend to uproot and dissolve the dike material.
There is, in fact, excessive vegetation on the eagle viewing area of the dike. Barnett said he was aware of the issue but would wait for the first few preliminary reports by the engineers before giving out any detail plans for the removal of those trees.
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