Using Balloons to Shift Broken Concrete Slabs at Glen Canyon Dam
June 14, 2022
When Bob Martin, the deputy power manager at the Bureau of Reclamation’s Upper Colorado Basin Power Office, needed to repair a damaged concrete apron at Glen Canyon Dam, he called on Reclamation’s power team, which includes certified divers and ropes-access technicians. The team came up with the idea of using balloons to lift and shift a large concrete slab. Mr. Martin spoke with Hydro Leader about the creative solution his team came up with to solve this unusual problem.
Hydro Leader: Please tell us about your background and how you came to be in your current position.
Bob Martin: I started out with the U.S. Army Corps of Engineers in 2001 as an electrician apprentice. When I finished the program as a journeyman electrician, I moved up to become a crew supervisor and then the manager at Glen Canyon Dam. Last fall, I became the deputy power manager for Reclamation’s Upper Colorado Basin Power Office.
Hydro Leader: What facilities do you work with in your role as deputy power manager for the Upper Colorado Basin Region?
Bob Martin: I work directly with the managers of the Glen Canyon Field Division in Page, Arizona; the Curecanti Field Division in Montrose, Colorado; and the Flaming Gorge Field Division in Dutch John, Utah. Our employees operate and maintain the Colorado River Storage Project hydroelectric power plants and dams, which include Flaming Gorge in Utah; Blue Mesa, Morrow Point, and Crystal in Colorado; and Glen Canyon near Page, Arizona. We also operate and maintain facilities at other Reclamation projects, including Fontenelle Dam and Power Plant in Wyoming and the Upper and Lower Molina Power Plants in Colorado.
Hydro Leader: Please introduce the Glen Canyon Dam.
Bob Martin: Glen Canyon was commissioned in 1964. It has eight units and a capacity of around 1,300 megawatts. With the low water we’ve had for the last 22 years, we’ve seen a reduction of about 30 percent in power capacity due to the low head.
Hydro Leader: Please tell us about the concrete apron component of the dam and explain how it got damaged.
Bob Martin: The apron was built at the tailrace to basically diffuse the water as it’s being released. In 1963, the operators were doing a big release through the outlet works, which is on the left side of the dam facing downstream. There was more water coming out of the outlet works than from the plant itself. That created a back eddy, for lack of a better word, in the area of the apron, causing the apron to fail. The operators decided to just leave the damaged apron in place— basically, several large slabs of broken concrete. A few years ago, we started to notice that bigger chunks of the concrete apron were creeping toward the draft tube area of unit 2. We continued to watch them, and after a few inspections, we noticed that one slab was moving into a place where it could potentially impede or completely inhibit our ability to put down the draft tube stop logs. That’s when we decided to remove the slab. Had we not done anything, it was likely just a matter of time before the slab slid into and covered that slot.
Hydro Leader: Please describe the different methods of repair you considered and what you ended up choosing.
Bob Martin: Initially, we thought that given the location, we could get our mobile crane in there, send divers 40 feet down to attach anchors to the block, and use the crane to lift the slab up and out. After the divers arrived on site and assessed the situation, the flows, and the location, we decided that the best approach would be to put anchors on the slab, attach salvage balloons to it, and float it to a new location. That seemed like a safer method than trying to pick the slab up out of the water. The divers attached four big salvage balloons to the four corners of the slab and then slowly inflated them as a diver down below watched. Once the block was lifted enough, winch lines were used to help guide it into a new location: a big hole further downstream that was created by the 1963 event and subsequent erosion.
Hydro Leader: Now that you have moved the slab to a different resting place, is further action needed, or is it just going to stay there?
Bob Martin: We don’t anticipate needing to move it out of that location. Overall, it was a successful operation.
Hydro Leader: Have you considered doing a repair to patch the concrete between the slabs or to replace the apron entirely?
Bob Martin: I don’t believe that would even be feasible. Essentially, the apron has been broken for over 50 years, and the only problem that we’ve noticed was that the big slab was moving toward unit 2.
Hydro Leader: The process you selected sounds quite innovative. Does this repair provide a model for any other concrete work you need to do?
Bob Martin: We’re fortunate that Reclamation has a dive team made up of members from various Reclamation facilities. One of those divers had experience with underwater salvage work, such as recovering cars from bodies of water. They knew how to rig the flotation balloons. Had we tried the mobile crane approach, it probably would have been successful, but it would have involved greater risks.
It’s valuable to have an in-house team to tackle a problem like this. In addition to Reclamation’s dive team, the Upper Colorado Power Office has a ropes team qualified by the Society of Professional Rope Access Technicians. The team does inspections, looks for loose rock, tests rock bolts, and so on. Having the operational flexibility to do work like this without having to go through the contracting process is huge for us.
Hydro Leader: Are there any other big maintenance projects coming down the line for Glen Canyon Dam?
Bob Martin: We’re currently halfway through our generator step-up transformer replacement. We’re replacing the original mineral oil–filled transformers with new transformers filled with a natural ester oil. My understanding is that these are the first natural ester oil–filled transformers in the 345‑kilovolt class put into operation. They were manufactured by ABB in Austria and are being installed by Yellowstone Electric from Billings, Montana.
Bob Martin is the deputy power manager for the Bureau of Reclamation’s Upper Colorado Basin Power Office. He can be contacted at email@example.com.