KGS Group of Winnipeg has won a 2023 Award of Excellence in the Municipal and Water category from the Association of Consulting Engineering Companies – Manitoba (ACEC-MB).
KGS won for its remediation of the low-level outlet conduit of the Lafleche Dam in Saskatchewan.
“We’re excited to have won the award,” said Jon Friesen, KGS senior geotechnical engineer. “It was what we were hoping for. Dam engineering is a risky field, and we’re gratified our work on the project has been recognized by our peers.”
The Lafleche Dam in southwestern Saskatchewan was built 65 years ago, in 1958. The dam’s reservoir, which is known as Thomson Lake, serves the small town of Gravelbourg and the surrounding area.
The lake is, in fact, an impounded reservoir that is part of the Wood River.
“There are more reservoirs like Thomson Lake in the region,” said Friesen. “There are few natural lakes in southern Saskatchewan.”
The lake has a number of uses – water supply, irrigation, fishing and boating, and flood protection.
Friesen said the dam has three parts.
First is the earth-fill embankment dam itself.
The second is a controlled spillway, which has gates to regulate the rate of flow.
This allows nearly the full height of the dam to be used for water storage. Flood waters can be released as required by opening one or more gates.
The third is a low-level conduit (or riparian outlet) that runs underneath the dam. Located near the bottom of the dam, it is used to maintain the flow of water downstream of the dam and, if necessary, to empty the reservoir.
The maximum flows that can be released through a low-level outlet are much less than what can go over a spillway.
Like spillways, the size and type of low-level outlets vary depending on their capacity and function. a pipe that runs under the dam.
“The conduit pipe at the Lafleche Dam is three feet in diameter,” said Friesen.
An inspection of the conduit in 2018 revealed that it had seriously deteriorated, which was a significant safety risk to the dam.
“Low-level outlets used to be made out of metal,” said Friesen. “That makes them vulnerable to corrosion, which can lead to holes and perforations in the pipe, which, in turn, can lead to damage of the dam itself.”
Remediation of the conduit presented many challenges, said Friesen.
“The conduit is located in the foundation of the dam,” he said. “That means the stability of the dam was at risk, so we had to be creative.”
KGS Group’s remediation solution required some innovative conduit replacement and rehabilitation methods, including such trenchless technologies as slip-lining and cured in place pipe replacement.
This involved inserting and running a felt liner into the metal conduit pipe that needed to be repaired.
Next, resin in the liner was exposed to a curing element to make it attach to the inner walls of the pipe.
Once it has been fully cured, the liner acted as a new, watertight conduit.
The work required excavations and other construction at the toe of the dam, which necessitated a dam safety surveillance program.
KGS put advanced telemetry instrumentation into the dam that was able to monitor the performance of the dam during construction and detect any movement.
Although the project had a relatively tight construction schedule (summer and fall 2022), it was completed on budget and on time.
The low level outlet was returned to full service in September 2022, following final commissioning of the new slide gate and the cathodic protection system, which uses an electrical current to prevent or delay metal corrosion in the original pipe.
Including KGS Group’s award for the Lafleche Dam, ACEC-MB was generous with awards in 2023: The Keystone Award, eight Awards of Excellence, six Awards of Merit and three Individual Awards.
The event was held at the new Royal Aviation Museum of Western Canada at the Winnipeg airport.
“We went with a new venue and a new format this year,” said ACEC-MB executive director Kerri Hiebert. “Unlike events in the past, there was no sit-down dinner. The guests enjoyed food stations during networking before the awards.
“And the awards were presented in a theatre-style setting, as opposed to the gala-dinner format.”
Hiebert said the awards event was “a huge success.”
“There were 200 people in attendance, which was a sellout of that venue space,” she said.
Next year’s ACEC-MB awards ceremony takes place April 18, 2024 at the Royal Aviation Museum.
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