Rock Anchor Installation Project: Calabogie Dam

The Challenge

In 2019, due to many years of service the dam at Calabogie Generating Station, required maintenance to increase its lifespan. To ensure that the dam was secure, rock anchors were installed through each pier down into the bedrock below. The work also had to be completed in close proximity to fish and wildlife.

The Solution

This required coring out the concrete to create a 32” diameter by 48” deep hole. This “pinning cap” helped distribute the load on the existing concrete for after the rock anchor was tensioned.

This was followed by coring an 8-inch diameter hole 25 feet through the concrete dam, and then 20 more feet into competent bedrock.

A crane was then used to hoist the pre-assemble rock anchor and install into the hole. All but the top 3 feet of the hole was grouted to leave room for the base plate and anchor head.

With the anchor in place, it was then tensioned with a load of 264 tonnes and locked off with wedges and wedge plate. This load was the equivalent of almost 8 full dump trucks. The anchor at full tension is what brings the stability to the multiple layers of concrete of the dam. The remaining hole was then encased in concrete.

Given the proximity of our equipment to the river, considerable measures were taken to protect the environment. All of our equipment rested in containment tubs which ensured no fluids leaked into the river. Furthermore, while drilling, a compressed air system was utilized to propel all cuttings so that they could be collected and disposed of.

Another interesting feature of the anchors for this particular project, is that they were designed so that - should the need ever arise - they could be re-tensioned to account for any losses over time.

Ultimately, our rock anchor work for the Calabogie power generating station was completed on time, on budget and without any safety or environmental issues.

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