Walco Industries Ltd. was asked to complete a hydrodemolition project at a hydropower dam. The dam is located in western Canada and is one of the largest earthen dams in the world. It’s a crucial supply of power for the province of British Columbia. The tunnels for the dam (as well as the conduits) were built in the mid 1900’s.  The job itself presented us with a unique task of completing a tapered hydrodemolition cut inside six conduit systems to facilitate a decommission plug in each of the three tunnel sections of the dam (There is two conduits per tunnel).

One of the main reasons Walco Industries Ltd was tasked with this project, was due to our expertise in the hydrodemolition world. One of the major difficulties for this, is completing a cut, designed to taper in an 84” conduit system, for only the bottom half of the selected areas to remove. Four cuts were to occur in each conduit, and the cuts were to be 5’6” in length and taper from a 12” depth, to a ½” depth. This cut was also designed to go halfway up the sides, with an angled cut on the sides and chamfered edges to reduce new pour stress on the corners. The rest of the conduit was to be scarified for proper bonding for the decommissioning plug. 

The entrance to each of the six conduit systems is 497 metres long to the end of the tunnel, roughly 9 metres in the air. Emissions were discussed due to all the equipment required and was a priority to control when in the tunnel systems. Scaffolding was assigned to reach the entrance to each of the conduits. Although the work occurring was at the dam, water supply was limited.   Knowing all this information, Walco Industries Ltd. accepted the challenge and utilized their robotic fleet to help complete these cuts. Walco industries Ltd. has over 40 years of high-pressure water jetting experience and expertise, with a training/research and development (R&D) facility on Vancouver Island.

This facility has been used for research and development on complex projects in the past and was used again for this task. Before our company went to site, both a R&D run and a trial run was to occur, with the trial run on the customers site in Hope, B.C. For the R&D test, a mock up of the conduits was built on Walco’s training property to allow testing and methodologies to come to fruition before the,trials were to occur. Major issues, such as depth and cut length control due to lack of visibility, collection of debris and water management was established and created. Walco and their employees spent 3 days completing mock-ups of the conduit cuts and parameter testing for the trial runs.   Due to the success found at the R&D facility, trial runs went as planned. The depths, lengths, spacing and design of the cuts were achieved in a timely fashion. Confidence of the customer for the capability to complete this task was growing. 

The time for the actual job arrived, and our personnel arrived at site. Water management and equipment layout was the first to set up. It was crucial to complete a proper water management circulation to reuse and recycle the water supply. Collection bins were placed underneath the scaffolding at the entrance to each of the two conduits inside the first tunnel to capture the spent water used in the hydrodemolition process. These collection bins then pumped water to a water storage prior to being sent to two floc tanks for settlement. The floc tanks were to settle some of the debris and pH levels were monitored at this point in the process. Once the water reached the final stage in the second floc tank, and the pH was balanced under 8.5, water was then sent to a second storage tank to complete a 5-micron filtration. The water was sent through Walco’s Filtration system, then arriving back to the high-pressure pumps for re-use.

This system managed the water for all three tunnels successfully, requiring only some added water to our system periodically for heat loss.  Once the water and equipment were ready, the cuts began in the first tunnel, east conduit. There was one major difference from the R&D and trial process, the aggregate was +/- 4- inch and the rebar was roughly at 4” spacing. These two items together added time to our process due to the rebar shadowing. Recalculations occurred for the robotics team to ensure the proper methodology and design of the cuts was followed. When the four cuts were completed on the first conduit (east side), the robot used was then transferred to the west conduit.

This conduit had the same aggregate and rebar as previous. With completion of the first tunnel, the equipment and water were transferred to the next tunnel with the use of a vacuum truck. Once the equipment and water were in place, the process for cutting was ready. The aggregate was back to the 2-inch style that was as per designed by our training facility. Although the rebar was the same spacing of 4”, the reduction of aggregate made the process a tad quicker. With each change of any parameter, the Walco robotics team ensure, with a test patch, the perimeters set previously would work for the new conduit or cuts. If not, change to correct the settings needed to occur. 

One of the ways that Walco could provide accuracy of the cuts angles and depths was using their LiDAR (Light Detection and Ranging) system. LiDAR is a remote sensing technology that uses lasers to measure distances and create highly detailed 3D models for the surface scanned. We utilized this system on each cut to ensure our customer and client had the precise measured angles and taper they required for the decommissioning plug. 

The third tunnel system presented the same situation as the previous two. The aggregate was still 2-inch minus, the rebar though had a 6-inch gap. This gapping in the rebar helps improve the speed of which the quality of the cut is easier to manage. With the lessons learn on the previous four conduits (two tunnels), we treated this tunnel as if it was a new, system. Test patch was complete to ensure the strength of the concrete was still the same as pervious ones. 

Throughout this project, problems can arise that complicate the task, that will delay the production and can cause unpredictable quality control. The use of robotic systems with custom engineering, quality control systems such as LiDAR, specific procedures and practices designed with a knowledge base through our training and R&D methods, and with the experience of 40+ years in the field, allows us to “simplify” a complex job and create a successful process in achieving the end result and goals. For further information please contact chris@walcoindustries.ca. 38/25