Canals, Tunnels and Penstocks

Using lessons learned from penstock cleaning to save time, money

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Using lessons learned from penstock cleaning to save time, money

By Chris Turney

Cleaning the inside of penstocks that supply water to hydroelectric powerhouses can be a time-consuming and labor-intensive process. This case study illustrates how it was possible to cut the time required to perform this work by more than 80% and reduce man-hours by about 75%.

The work to be discussed took place at the Bridge River hydroelectric complex in British Columbia, Canada. Bridge River is a mid-sized stream about 120 km long, flowing southeast from the Coastal Mountains and joining the Fraser River near Lillooet. The 492 MW Bridge River hydroelectric complex consists of three dams and stores water for four generating stations. The system uses Bridge River water three times in succession to supply 6% to 8% of British Columbia’s electrical supply.

In the summer of 2018, BC Hydro contracted Walco Industries to perform high-pressure cleaning of the internal surface of a 10-ft-diameter, 4,400-foot-long steel penstock named BR 2.1 at its Bridge River Power Project. This was needed to prepare for sandblasting and painting, as originally it was coated with lead paint.

The penstock is located on the rock face of the side of a mountain in the Seton Portage area, close to Seton lake. It feeds water to two turbine-generator units. The penstock runs at a slope of about 40 degrees at the beginning and then an average of 11 degrees. At the end, before the bifurcation, it slopes to about 42 degrees before levelling out.

Walco used a robotic system supplying 20,000 psi of water at high flows to clean this penstock. The system moves itself forward as it oscillates and cleans. The job was completed in 108 days, with 484.6 man-hours of work. Uncommon hurdles occurred weekly. Two forest fires, high winds, lightning strikes and thick smoke were among the issues. Unknown heavy metals were also found, such as chromium and lead.

In the spring of 2022, BC Hydro again hired Walco Industries, this time to clean the inside of sister penstock BR 2.2, which had the same angles, a slope of 40 degrees and diameters varying from 9 ft 9 in at the top to 6 ft 6 in at the bifurcation. Using the lessons learned from the first cleaning project, the company completed work on the second penstock in 17 days and cut the in-person time in the penstock to 112 man-hours.

Improving by using lessons learned

The lessons learned from the first cleaning project were used to vastly improve the methodology and efficiency of the task for the second project. For example, Walco used a custom-built reel to hold 3,500 feet of 1-in 20,000 psi hose that ran a variable frequency, remote-controlled drive to pull the hose through the penstock. Using this reel eliminated hundreds of hours of labor assembling, disassembling, dragging, and carrying the heavy hose by hand. Electronic winch systems were upgraded to coordinate with the reel to adjust the speed at which the cleaning system was pulled through the penstock.

Use of a custom-built hose reel allowed Walco to improve efficiency of the penstock cleaning task.

In addition, a closed-circuit television system was upgraded to 8k viewing with significantly more cameras for a more accurate depiction of the quality of the job, hundreds of meters up the penstock, and viewed in multiple locations at the same time in separate crew trailers on the mountain. The screens were 48-in OLED gaming monitors for the best viewing quality. And custom re-directs were built to eliminate hose wear at the entrance points to the penstock.

Hurdles encountered for the work in 2022 were minimal, except for sub-zero temperatures due to the early start in the year, compared to the high heat of 2018.

Weeks of pre-job training, research and development were completed at the Walco Industries Training Center — where a 10-ft-diameter, 180-ft-long penstock at 45 degrees was built — to increase worker confidence. Substantially more investment was made for the training, and improvements were made to boost safety and morale. These costs were much higher than anticipated, but the return on investment when the overall job was completed was significant.

Weeks of pre-job training, research and development were completed at a training center.

Things that were done to improve morale onsite in the remote location involved the company investing in 14-ft crew trailers for the two locations (the top of the hill and 700 ft down) that contained big screen TVs for monitoring the cameras inside the penstock, coffee machines, water coolers, heat, air conditioning and speakers. In addition, special areas were installed so that workers could remove lead and debris from all equipment, to minimize environmental impacts. Vacuum systems picked up water or debris that was contained by spill berms.

Walco Industries was established in 1980 and is a family-owned business in western Canada that serves a diverse array of industries. In recent years, the company has moved from industrial cleaning, hazardous waste hauling and hydro-vac services to hydrodemolition, specialized robotics, and high-risk, high-reward capital projects such as the Bridge River penstock cleaning work.

Chris Turney is safety coordinator with Walco Industries.