What is the proper construction material for causeways and coffer dams near live watercourses?

The selection of non-erodible materials for causeways and coffer dams near live watercourses is crucial for ensuring stability, durability, and minimal environmental impact. Non-erodible materials, such as certain types of rock, concrete, or specially designed geotextiles, are resistant to water flow and wave action. This quality helps maintain the integrity of the structure during periods of high water flow, preventing collapse or failure that could lead to sedimentation, erosion, or flooding downstream.

Using non-erodible materials also helps to minimize environmental disturbances that could affect aquatic habitats. Unlike earthen materials, which can erode and wash away, or wooden planks that can decompose or be undermined by flowing water, non-erodible options ensure longevity and stability during construction and post-project phases.

Other materials listed, such as solely earthen materials, may not provide the necessary support and could lead to erosion, while wooden planks may not withstand prolonged exposure to water. A mixture of sand and gravel, while useful for some applications, does not provide the structural integrity required for transient structures like causeways and coffer dams as effectively as non-erodible materials. Using non-erodible materials aligns with best practices for stormwater management and ensures