By Mark Crawford
Development often brings change to natural landscapes that impacts wildlife’s migration patterns. In particular, dams, locks, bridges and culverts can prevent fish from migrating upstream to spawn, reducing their population numbers. Fish passageways – routes specially designed to bypass man-made barriers – allow fish to continue their journey. Passageways are designed so the current flows fast enough to attract the fish, but slow enough to not exhaust them or wash them back downstream.
Precast concrete is often the material of choice for constructing fish passageways because it installs quickly in stream settings, saving time and minimizing surface disturbance when compared to cast-in-place or metal components. It’s also easier to create natural features with precast, such as fish steps with embedded rock-like shapes.
Depending on project needs, there are a variety of passageway configurations to choose from, including fish ladders and culverts with baffles. For two recent fish passageway projects, precast structures played a key role in protecting and restoring fish populations and their natural habitats.
Protecting threatened fish in Colorado
In 2014, Lindsay Precast’s plant in Colorado Springs, Colo., worked with Colorado Springs Utilities to develop straight and bend sections for a local fish passageway on Fountain Creek. CSU’s goal for the project was to help preserve the Arkansas darter and the flathead chub, both species of special concern in Colorado.
“The fish ladder could be bid as precast or cast-in-place,” said Paul Sook, vice president of Wildcat Construction, the project’s general contractor. “We elected to go with precast. We felt we could control quality much more easily than cast-in-place.
“It was also a more cost-effective and faster solution. We were going to be working in the active stream and wanted to get in and out as quickly as possible, to minimize any environmental impacts.”
Another reason for speed was the timing of the project. Construction was scheduled for the fall and winter months, when Colorado weather can be unpredictable. With guidance from CSU, Lindsay Precast designed the precast elements.
“Of critical importance was the simulated streambed and rock features required to help the fish swim through the structure,” said Randy Lindsay-Brisbin, vice president and director of Lindsay Precast. “CSU also consulted a fish expert to design the streambed features for the precast segments.”
Lindsay Precast first manufactured a non-textured section of the fish ladder. Production workers then grouted rocks and streambed features by hand to the section and evaluated the product to ensure fish-friendly flow patterns. Once the layout of the rock features was approved, Lindsay Precast obtained the formliners.
“From a manufacturing perspective, the development and procurement of a cost-effective formliner and forming system was key to this project,” said Lindsay-Brisbin. “Lindsay Fabrication, our in-house form fabrication division, manufactured the form components. Scott System, a concrete formliner firm in Denver, partnered with our project team to develop a random stream bottom/boulder design to meet the ecological requirements of the project.”
Precast elements for the fish ladder consisted of 20 straight-trough sections and nine curved-end sections. Wildcat Construction poured the foundation and piers for the structure in place. The precast segments were then placed on the substructure and tied together with small closure pours. Lindsay Precast also manufactured additional precast rocks it used at the transitions at the top and bottom of the passage. Each straight section is 14 feet, 9 inches long and approximately 4 feet wide, weighing 6,200 pounds. Each bend section is a 100-inch semicircle weighing 3,400 pounds.
The project was completed in November 2014. Monitoring equipment will be installed in early 2016 to track fish traffic and document the effectiveness of the structure over time.
“We are proud to play a role in developing and executing these kinds of environmental projects,” Lindsay-Brisbin said. “The Fountain Creek fish passage is another example of projects that benefit and protect our natural resources.”
Passing the impassable in British Columbia
For the past decade, salmon travelling up Yorkson Creek in Langley Township, B.C., encountered an impassable culvert, preventing them from spawning. Working with the township, McElhanney Engineering designed a fish baffle system for the stream bed, enabling the salmon to continue their migration upstream.
“We chose a precast option because it allowed the precast contractor to be in the creek for a shorter duration of time, reducing the risk of disturbing the sensitive fish habitat,” said Joel Grams, project manager for Mainland Civil Site Services, the general contractor on the project. “A cast-in-place option presented a bigger risk because it would have required us to form, pour, place, finish and cure the slab, walls, baffles and roof.”
Joel Shimozawa, technical marketing engineer for the Langley Concrete Group in Chilliwack, B.C., stressed the importance of moving quickly on the project.
“In British Columbia, there is a fisheries construction window for completing in-stream works,” he said. “The window generally runs between July 15 and Aug. 15, but varies depending on the species of fish and weather.”
Langley Concrete produced the 12-foot-by-7-foot box culvert at Yorkson Creek using dry cast concrete. V-notch baffles were installed as a secondary pour with a wet cast mix.
“If a large number of baffles is required, we use a rapid-setting additive so we can complete up to three weir baffles using one form per day,” Shimozawa said.
A few weeks after completion of the project, wild coho salmon returned to the creek and began swimming through the culvert, which also provides protection from predatory bald eagles.
“The success of the project and the return of spawning salmon make us proud of the positive environmental impacts we can have as precast producers,” Shimozawa said.
Nothing fishy about protecting wildlife
Precast concrete is an excellent building material due to its myriad advantages, including durability and ease of installation. For time-sensitive projects that can have an impact on the environment, these attributes play an even bigger role, allowing project owners and contractors to successfully complete the work and attain maximum impact with minimal site disturbance.
Mark Crawford is a Madison, Wis.-based freelance writer who specializes in science, technology and manufacturing.
Sidebar – Saving the Toadlets
Langley Concrete Group donated a 6-foot-by-3-foot box culvert to create a toad crossing in Chilliwack, B.C., saving thousands of toadlets from heavy vehicle traffic on Elk View Road.
In the spring, western toads mate and lay eggs in the wetlands around Chilliwack. By summer, the baby toads are ready to migrate to the nearby forest – but they must first cross a busy Elk View Road. The Fraser Valley Conservancy, in partnership with Lafarge Construction and the Langley Concrete Group, designed a toad-friendly tunnel under the road.
“The toads do not enter a space that is dark, so we had to let light into it,” explained David Redfern, vice president and general manager for Lafarge Construction in Vancouver. “We had to develop a grate that would be structural and still let enough light in to have the toads accept it as an environment.”
The project cost about $120,000, with most of the materials and labor donated by participating companies – including Langley Concrete Group.
“We are a family-run business and are proud to supply products for communities to build on,” Shimozawa said.
You could say the project has been a hopping success: more than 8,000 toads passed through the tunnel last summer.
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