The COVID-19 pandemic hasn’t stopped construction activities on the Corra Linn Dam, though some unexpected delays have forced owner and operator FortisBC to restructure its timetable.
The Corra Linn Dam was first commissioned in 1932 to generate electricity and hold water back from the Kootenay River onto Kootenay Lake. Over the years, the dam has received upgrades to its power generators and general maintenance and repair work to keep the structure operating reliably and safely. This current upgrade-and-repair effort got underway in 2018 and is a comprehensive project focused on replacing spillway gates to meet dam safety legislation and adding additional safety monitoring measures.
The project was originally planned to end in September 2021, though unexpected issues with some of the repairs have affected that timeline, according to Brad Stykel, a project manager in the major projects division at FortisBC.
The concealed components (known as the sill beam and side guides) supporting three of the 14 spillway gates that were worked on for this project – gates 9, 10 and 11 – had corrosion issues that exceeded what was considered acceptable in the project’s technical specification. As a result, the gate guides had to be replaced on those gates, which increased costs and required more time to complete than the company had initially planned.
Crews are working on spillway gates 6, 7 and 8, where the same issues with the gate guides are being seen, so replacement work on those is underway as of early August 2020.
The crews also began work on gate 5 this month, and Stykel said they expect to find the same gate guide issues there as well. Depending on how many of the remaining gates will need similar work, project completion could be pushed into late 2022, with a final cost between CDN$75-82 million (up to US$62 million). As a result, work crews have had to adjust their timeline, which was initially designed around the spring freshet – the point in time the most water tends to be coming through the dam.
Stykel said that in addition, there has been a delay in refurbishing what’s known as gantry 2.
These gantries are used to hoist up the dam gates. Ensuring that the rebuild of gantry 2 is done properly is important to the long-term safety and health of the dam. Additional safety monitoring mechanisms to be installed during the work are still being discussed but have not yet been finalized as of early August, Stykel added. The gantry 2 refurbishment must be done outside of the spring freshet because having the additional gate operation available is important for managing flows at that time.
Stykel said the company is planning work on four gates at a time instead of three. This will not impact water flows, he said, as the dam was built with redundancy in mind. With five gates out of service, the dam would still be able to pass through the equivalent amount of water seen in the worst flood observed in the past century along the Kootenay River.
“Hopefully this will mitigate some of these delays,” Stykel said.
FortisBC has experienced minimal delays due to additional safety protocols for construction workers due to the COVID-19 pandemic, such as adjusted work procedures, additional handwashing stations, a ban on external visitors and new cleaning measures. These seem to have paid off, however, as Stykel said they haven’t reported any cases of the disease as of July 9 and work has otherwise continued without an issue. While this has increased costs, it has not halted work on the project.
Other work being completed as part of the reconstruction effort includes reinforcing and rebuilding the dam superstructure and ensuring all the gates have sufficient redundancies to meet British Columbia’s dam safety regulations that were updated in 2009. These upgrades also will ensure the gates do not age outside of the US Army Corp of Engineers’ safety guidelines, which say that well-maintained gates on a dam have a 100-year service life; the gates were 85 years old at the start of the project.
