Thank you for your interest in learning more about the Flexi Baffle and how it can be used to improve fish passage in your culvert. These Frequently Asked Questions are intended to address many questions we routinely receive. The first section below provided information on how the Flexi Baffle works to improve fish passage, what it is made from and some examples of existing installations. The second section provided information on the design and installation of Flexi Baffles. If you have any other questions or comments regarding the Flexi Baffle or its use at your project, just click here to contact us!
1. General Information on the Flexi Baffle
What is a Flexi Baffle?
A Flexi Baffle is a flexible weir placed in culverts to enhance fish passage. It increases water depth, reduces water speed and provides resting spots for fish and other aquatic life. The baffle’s flexible design ensures that debris and water can pass through safely during high flows. This maintains the culvert’s hydraulic capacity and minimizes blockages by allowing debris to move through easily.
Flexi Baffles can turn your culvert into a fish ladder!
How do Flexi Baffles help fish passage?
Flexible baffles help fish and other aquatic organisms pass through culverts by:
- Reducing water velocity, making it easier for aquatic organisms to swim through culverts.
- Creating resting areas, allowing fish to conserve energy.
- Mimicking natural stream conditions, improving habitat quality inside culverts.
What aquatic species would benefit from the Flexi Baffle?
Flexi Baffles improve conditions for aquatic organisms in your culvert. Culverts are usually built to move water efficiently, which can create fast water currents and shallow depths that hinder movement of fish and other aquatic organisms. Flexi Baffles address this by slowing the water flow and adding complexity to the culvert’s interior, promoting more natural flow patterns. By replicating natural stream conditions around the culvert, they enable local aquatic species—like fish, eels, lamprey, amphibians, reptiles, and invertebrates—to navigate through it successfully.
What are the benefits of the Flexi Baffle versus solid baffles?
- Minimal Flow Restrictions: They flex during high flows to preserve culvert capacity, unlike rigid baffles that reduce culvert capacity.
- Reduced Debris Accumulation: Their flexibility allows debris to pass through, avoiding clogs that are common with solid baffles.
- Easier Installation: Flexi Baffles require no major culvert changes, while concrete or metal baffles need extensive retrofitting and dewatering.
- Cost-Effective: Lower costs for materials and transport, and ease of installation make them more affordable than heavy, rigid options.
- Adaptability: They can be cut and shaped to fit various culverts, unlike metal or concrete baffles that need precise pre-fabrication.
- Durability – able to withstand impacts from debris or high flows
What is the cost of Flexi Baffles as compared to other fish passage solutions?
While culvert removal or replacement is the most effective way to enhance fish passage, it’s often impractical due to high costs or disruptions to transportation and infrastructure. Installing Flexi Baffles often costs less than 1% of what it takes to remove or replace a culvert. Disturbance to soils and traffic disruptions are avoided. Flexi Baffles provide a simple, low-cost alternative for improving passage through existing culverts.
How long does it take to install Flexi Baffles?
The time required to install Flexi Baffles depends on the size and composition of the culvert. However, a typical Flexi Baffle only takes a matter of minutes to install. We use common hand tools to affix the Flexi Baffles to the culvert. Our crews can outfit 4 to 8 typical culverts per day with Flexi Baffles. The culvert DOES NOT have to be dewatered to install Flexi Baffles.
Solid baffles require much more labor and cost to install as compared to Flexi Baffles. Concrete baffles are either formed and poured inside the culvert or they are formed and poured outside then transferred into the culvert and attached. Plastic or metal culverts are typically welded in place. The culvert typically has to be dewatered to install solid baffles.
Can Flexi Baffles be installed in existing culverts?
Yes, Flexi Baffles can be installed in existing AND new culverts. Flexi Baffles can also be installed before the culvert is installed. The culvert does not need to be dewatered to install Flexi Baffles.
What are Flexi Baffles made of?
Flex Baffles are made from EPDM (ethylene propylene diene monomer), a durable, non-toxic synthetic rubber known for its excellent resistance to abrasion, temperature extremes, UV exposure, ozone, aging, weathering, acids, and many chemicals. Common uses of EDPM include potable water collection systems, medical devices and automotive door and window seals.
How long are Flexi Baffles designed to last?
Flexi Baffles are a long-term solution for fish passage. We have Flexi Baffles that are performing well after 15 years. We suggest a lifetime of 10-years for planning purposes. Regular inspections ensure continued effectiveness.
Can Flexi Baffles be used in all types of culverts?
Yes, Flexi Baffles are suitable for circular, box, and arch culverts. They can be installed in culverts made of plastic, concrete and metal.
Where have Flexi Baffles been installed?
Originally developed in New Zealand, Flexi Baffles now number in the thousands worldwide, with installations across Australia, Europe, and North America—currently spanning 15 U.S. states and 4 Canadian provinces, with more added regularly.
Where are Flexi Baffles manufactured?
Flexi Baffles are manufactured in the United States using all American-sourced materials.
Can Flexi Baffles withstand extreme temperatures?
Yes, EPDM rubber withstands a wide temperature range, remaining flexible in cold conditions and resistant to heat up to 150°C (302°F).
Do Flexi Baffles create microplastics?
No, Flexi Baffles are made of EPDM, a synthetic rubber, not plastic. This material is non-toxic, 100% recyclable, and highly resistant to degradation.
Do Flexi Baffles contain chemicals toxic to fish, such as 6PPD-quinone?
No, Flex Baffles are made from 100% EPDM, a durable, non-toxic synthetic rubber. They do not contain harmful chemicals like 6PPD-quinone, which has been identified as toxic to fish.
What are the effects of Flexi Baffles on the hydraulic capacity of culverts?
Flexi Baffles installed in a culvert can increase Manning’s “n”-value by about 10% to 30% compared to standard pipe.
- For a 3-foot diameter smooth surface pipe such as concrete or HDPE, a conservative recommendation would be n=0.020 for 8-foot Flexi Baffle spacing to 0.030 for 3-foot Flexi Baffle spacing.
- For a 3-foot diameter corrugated metal pipe, a conservative recommendation would be n=0.030 for 8-foot Flexi Baffle spacing to 00.045 for 3-foot Flexi Baffle spacing.
Do Flexi Baffles catch debris?
The Flexi Baffles are designed to “bend over” in high flows to help preserve the hydraulic capacity of your culvert. The flexible design allows debris to pass through the culvert unimpeded. Once the water flow declines after a freshet, the baffle reorients and creates a fish ladder in your culvert.
What is the experience of others using Flexi Baffles for fish passage?
Many users have successfully installed Flexi Baffles to enhance fish passage. Click on the pictures below to watch videos demonstrating real-world installations.
The Johnson Creek Watershed Council in Portland, Oregon installed the first Flexi Baffles in North America in 2018. They have since installed Flexi Baffles at two more sites. Here is a video they made of their first Flexi Baffle installation
The New York Department of Environmental Conservation installed Flexi Baffles in 2018 in a box culvert in Cook’s Brook located in the Town of Colchester, Delaware County. Here is a YouTube video of the project.
The City of Ketchikan, Alaska installed Flexi Baffles in a large culvert in 2024. Their consultant made a video of the installation
The City of Surrey, British Columbia has installed Flexi Baffles at several sites throughout the City. One Flexi Baffle installation resulted in Pacific salmon returning to a watershed for the first time in over 70 years. Here is a video from the City of Surrey on the Flexi Baffle installation on Bon Accord Creek.
Do I need a permit to install Flexi Baffles?
Permit requirements vary by location and regulatory authority. Check with local environmental agencies for guidelines.
How do I order Flexi Baffles?
Please click here and we can help develop a proposed Flexi Baffle configuration for your fish passage project!
2. Design & Installation of the Flexi Baffle
How are Flexi Baffles installed in culverts?
- In corrugated metal or HDPE plastic culverts, Flexi Baffles are installed using self-tapping screws.
- In concrete culverts, they are installed with wedge anchors.
- We recommend using stainless steel hardware for durability and to reduce corrosion.
- Click here for Flexi Baffle installation instructions.
Does installing Flexi Baffles damage a culvert?
No. For concrete culverts, we recommend you use wedge anchors in that do not completely penetrate through the structure. Self-tapping screws used in metal and plastic culverts make small penetrations that do not affect the culverts. We have no reported damage to culverts in the thousands of Flexi Baffles installations around the world.
Do I have to dewater the culvert to install the Flexi Baffles?
No, you do not need to dewater the culvert. Most often, Flexi Baffles can be installed with water in the culvert using proper tools such as extensions on drills.
What size Flexi Baffles should I use?
The appropriate size depends on culvert dimensions and the target fish species. Click here for Flexi Baffle size and spacing recommendations. We recommend you contact us for guidance if you have any questions or comments.
What Flexi Baffle spacing do you recommend?
Spacing depends on culvert gradient and target fish species. Click here for spacing guidelines or contact us for assistance.
What are the maintenance requirements for Flexi Baffles?
Regular inspections to ensure baffles remain secure.
Need more information or assistance?
For more information, please contact us at:
SSA Environmental
360 601-2391
Also, visit our website at: https://ssaenvironmental.com/flexi-baffle/