Road Ecology Center
Design and construction of aquatic organism passage at road-stream crossings: construction challenges and case studies of stream simulation structures for aquatic organism passage
- Author(s): Johansen, David K
- et al.
This paper presents guidance for constructing stream simulation structures capable of passing most aquatic organisms, amphibian and some terrestrial species. Bridges are not addressed specifically in this document but many of the construction details, including the stream simulation bed, apply to bridges. To simulate a stream the structure must have been designed to fit well with and have minimal impact on stream dynamics and processes. Traditional construction methods are used for both embedded pipe and open bottom arch construction. In chronological order, the primary structure construction steps include prework meetings, surveys, traffic controls, dewatering, erosion control, clearing, excavation, foundations, bedding, pipe assembly, backfill and embankments, and rewatering. The single most important and unique detail to stream simulation structures is the simulated streambed inside the embedded pipe or open bottom arch. The bed is typically shaped to have a low water channel, margins, and banks and may include other large rocks added to simulate streambed roughness, stable banks and step pool. Bed construction requires unique effort and a combination of machinery and skilled hand labor to fit and arrange pieces to match the design interlock well and be durable. Protection of the aquatic environment is emphasized through minimizing turbidity and sedimentation. Additional aquatic organism protection can include collection and transport of species from the dewatered area, slow rewatering to avoid stranding, limiting toxic substances and noise, and reducing blasting effects. Communication among designers and contract administrators is emphasized to improve understanding of design objectives, maintaining a feedback loop to address site problems and transferring wisdom gained from the project’s construction.