Buried Steel Bridge Reconnects Aquatic Habitat for Alabama County

Article provided by Contech Engineered Solutions and the National Corrugated Steel Pipe Association

In Alabama, several organizations have collaborated to improve habitats for endangered species. The Cawaco Resource Conservation & Development Council, U.S. Fish and Wildlife Service and other partners have been working together on projects that replace culverts.

These culvert replacement projects in Alabama aim to restore the natural flow of streams, helping aquatic species move freely through their habitats.

Funded primarily by the National Fish and Wildlife Foundation’s Southeast Aquatics Fund, the project used steel to replace two high-density polyethylene (HDPE) pipe culverts that had become perched, impeding fish passage.

Replacing Culverts for Better Fish Passage

The goal of the project is to reconnect fragmented aquatic habitats. This is done by replacing deteriorating or improperly sized culverts with structures that are more “fish-friendly.” The new designs help restore the natural hydrological conditions, allowing aquatic species to migrate more easily.

Additionally, the open-bottom culverts used in these projects tend to last longer. Without an invert in contact with water, they experience less wear and tear. In this context, culvert replacement in Alabama has proven to be an effective measure.

This particular project, funded primarily by the National Fish and Wildlife Foundation’s Southeast Aquatics Fund, replaced two culverts made of high-density polyethylene (HDPE) pipe. The original culverts had become perched, which made it difficult for fish to pass through.

Location and Importance of the Project

The St. Clair County Road Department Crew led the construction of the project in St. Clair County, Alabama. They installed a new culvert that now spans a stream, providing seasonal spawning habitat for the federally threatened Trispot Darter. The previous culvert design had blocked the darter’s migration route, disrupting its natural movement.

Native to streams in northern Georgia and southern Tennessee, the Trispot Darter was thought to be extinct for seven years until its rediscovery in 1967. Once common in the Alabama River system, its population has sharply declined due to human development. Efforts like culvert replacements in Alabama aim to reverse this trend. Now, the species primarily lives in Alabama’s Big Canoe Creek and the Conasauga River system. The survival of its eggs depends heavily on water quality, particularly silt levels and temperature.

The project used Contech’s advanced deep-corrugated, galvanized structural plate arch and Steel Express Foundations. The prefabricated steel foundations eliminated the need for on-site formwork and reinforcing steel, significantly accelerating the installation process.

Construction Process and Materials

The project utilized advanced technology from Contech, featuring a deep-corrugated, galvanized structural plate arch. The bottomless culvert measured 56.5 feet long, with an 18-foot 5-inch span and an 8-foot 4-inch rise. This approach demonstrates the cutting-edge culvert replacement techniques being applied in Alabama.

The team used Contech’s Steel Express Foundations to accelerate installation. These prefabricated steel foundations, measuring 2 feet 9 inches wide by 2 feet deep, eliminated the need for on-site formwork and reinforcing steel, which significantly sped up the construction. They also installed aluminum structural plate headwalls and wingwalls as end treatments for the culvert.

Conclusion and Collaboration

Specialist contractor Platinum Erectors assembled the arch, foundations, and end treatments. The St. Clair County Road Department Crew then completed the backfilling and other installation tasks. This collaborative effort has not only improved fish passage but also restored an important habitat for the Trispot Darter and other aquatic species. The success of this project underscores the importance of culvert replacement initiatives in Alabama.

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