6/14/2023
We’ve had a mechanical crew down to Cataract turbine disassembly/reassembly project the past few months, but now they are joined by a civil crew to begin work on the extension of an existing fishway approximately 50 ft into tailrace. To complete this project, we’ll be constructing a cofferdam, drilling and installing rock anchors, placing +/- 500 CY of structural concrete, demolishing other sections of concrete, adding structural steel, and performing a mechanical scope.
The plan is to mobilize once the in-water work window allows (mid-July). Beginning with dive inspections, debris removal and layout of cofferdam frame. Once river bottom is cleaned and ledge subgrade is confirmed, the sheetpile cofferdam will be installed with strict horizontal tolerances as the majority of the cofferdam will be left in place as a form for the new structure. This is the first couple months scope. The second half of the project will include the rock anchors, structural concrete and existing fish passage demo.
A particularly interesting and challenging aspect of this work is that the access is extremely limited. Once you factor in the reality that this limited access has to service both the fish passage project and the ongoing turbine rebuild that the mechanical division has been performing, and the degree of coordination required of our mutual teams becomes abundantly clear.
Project anticipated to go through the winter with a March 2024 target date for completion.
8/25/2023
The loose ledge on the fishway is being removed to help prepare the site for the coming work. The intention is that the removal of this material will allow for the site to be unimpeded in the future when sheet piles are driven in to create the coffer dam. Work has been going smoothly so far with more updates to come in the near future. Stay tuned!
12/22/2023
As mentioned earlier in this portion of the newsletter, project manager Peter Poor and his rugged crew have also been working around the dam, reconstructing the fish passage. Over the last month or so, they have been pounding away at the to do list and have made some incredible progress.
As they worked on the cofferdam, they did so with great care, as much of the sheet-pile will become a stay-in-place form system for the new fishway walls. A quick quote from Pete says it all:
“Kudos to the crew for layout efforts — All within ¼” horizontally and vertically. Very tough to do.”
The next step of the process was to shore up any gaps to make the dewatering process go smoothly. To do so, tremies were placed to ensure the concrete wouldn’t be washed away. With significantly limited access, this proved to be quite a learning curve, but again the seasoned crew’s efforts prevailed with incredible ingenuity and troubleshooting.
It was then turned over to Maine Drilling & Blasting and a team of divers to accurately install 22 rock anchors for the tremies with frames and templates that were fabricated by the Bancroft crew. Once placed, testing took place to ensure everything would hold, and sure enough, it held. With the cofferdam secure and watertight, it was time to bring in the water pumps and dewater this sucker and really start to work on modifying this fish passage.
It’s only appropriate for Pete to point out a few more things about his crew at Cataract:
“Todd and the crew deserve major praise for the work completed to date. Impressive due to the obstacles and compactness of the site, technical and precise nature of the work to date (majority completed over the radio with divers).”
Looking ahead, we will have concrete finally starting up with slab placements scheduled for the week of 12/18, as well as a lot of demo to the existing fishway entrance. Through March 2024, it’s safe to say concrete will be the main focus for these guys.
Be sure to check out the back for some pics!
3/22/2024
In December, the last time we reported on the Cataract Fish Passage, Project Manager Pete Poor was singing the praises of the crew for their determination in getting the coffer dam placed, despite challenges and obstacles that made completing each step tricky. Since then, the crew has been hard at work getting concrete placements in.
Leading up to Wednesday’s 22-cubic-yard placement for the last of the walls, were 3 other placements (the slab and 2 walls) with the largest placement being 48-cubic-yards. Thrown into the mix was the removal of 36 tons of old concrete, which was cut out into 9 blocks weighing approximately 8,000 pounds each. In order to remove these blocks, the crew rigged each block and it was hoisted out by crane 138 (see the pictures to the right for size and scale). With the old concrete coming out and the new placements made, this fish passage seems to be not only in good shape, but on schedule.
The next few weeks of work is going to have the crew getting back into some demolition work to be able to install radial forms on both the top and bottom ends of the passage. In order to make that happen, an excavator is going to be equipped with a hammer to take care of the top side, while a mini-ex will and hand chippers will take care of the bottom section.
Once the concrete is poured and cured, the coffer dam will be removed, the side walls have more concrete added to make them taller, and a 30” water attraction pump pipe will be fabricated in the South Paris fabrication shop and installed. Even though there are plenty of other things beyond, the project is shaping up nicely to be completed by the end of July.
5/3/2024
A lot of things are starting to come together and take shape (literally and figuratively) for the crew at the Brookfield hydroelectric dam. Following the completion of the concrete placement on Tuesday (4/30), the experienced crew is now able to turn their attention to removing sections of the cofferdam frame. As the concrete continues to cure and strengthen, plans are being made to install a temporary frame to ensure the upper section of the frame remains intact while the last 5’ of the lift is installed.
Away from the site, at the Vulcan building in South Paris, Ricky Taylor and Mike Gallant worked to build custom radius forms to give this passage a smooth finishing edge at the turn. The forms were then sent down to the site and installed in preparation for their respective concrete pour.
Into this weekend, the crew is continuing to work to excavate, install foundational forms, and lay rebar for piping. The ongoing work will help to alleviate the congestion in the tiny work area and give the project a little boost forward on the schedule.
In conjunction with the foundations of the piping, are the pipes themselves. Spool pieces of 24- and 30-inch pipes are being fabricated in the South Paris Fabrication Shop for the Attraction Water System, which will then be fit together on site, in Saco. This portion of the project has been a threefold effort by John Metcalf, Dave Grover, and Floyd Balliet. Next up for these guys is the fabrication of supports.
Additional future installations and works will include: the balance of concrete; embedding various metals for supplemental support; installation of the previously mentioned Attraction Water System; a visit from Mastercraft to install the required electrical; and, finally, the gates and operating systems.
For Pete Poor, Todd Leighton, and their steadfast crew, the major push will be through May and June with the installation of the gate, various specialty fishway components, and electrical systems. With everything going smoothly so far, startup looks like it’ll be sometime in July.
6/28/2024
No write up.
1/3/2025 (Completion)
The work at the Cataract Fishway is largely complete as of early December. Next week, we’ll carry out some additional tasks to support the installation of flowmeters and will return in the spring to finalize a few miscellaneous items.
Despite being a long and challenging project, the outcome is something everyone involved can take pride in.
Key achievements include constructing a cofferdam built to precise vertical and horizontal form tolerances, serving as the outer form for the new structure. The project also featured intricate concrete work with radiused forms, suspended walls, and slabs, each placement presenting logistical challenges due to access constraints. We fabricated new 24″ and 30″ piping entirely in-house, spooled it in our fabrication shop, and installed it on-site with our crews.
Most importantly, the crews completed the project safely, logging approximately 30,000 man-hours without any recordable incidents.
June ’23 — Cofferdam Placement Begins
Dec. ’23 — Severe Storm Hits the Dam
April ’24 — Concrete Work Presses On
June ’24 — Attraction Water System is in
Nov. ’24 — Substantial Completion
