US Forest Service

United States Department of Agriculture Forest Service Enterprise Program

Enterprise Technical Services


Aquatic Organism Passage (AOP) Help

Rivers and streams are more than mere conduits for water and fish. They are long, linear ecosystems made up of the physical environment, communities of organisms, and a variety of ecological processes that shape and maintain these ecosystems over time. The long-term conservation of important aquatic resources (such as fish) requires the maintenance of healthy and ecologically viable ecosystems. Road crossings have the potential to undermine the ecological integrity of roaded river and stream systems in a number of ways. To ensure the productivity and viability of river and stream ecosystems, we must protect and restore the quality of the physical environment (habitat), maintain intact communities of aquatic organisms, and take care not to disrupt critical ecological processes.
Stream simulation is an approach to designing crossing structures (usually culverts), that creates a structure that is as similar as possible to the natural channel. When channel dimensions, slope, and streambed structure are similar, water velocities and depths also will be similar. Thus simulated channel should present no more of an odstacle to aquatic animals than the natural channel.

Enterprise Technical Services (ETS) provides turn-key services in aquatic organism passage project design and construction. We can help identify critical barriers within your transportation system; provide National Environmental Policy Act (NEPA), wetland delineation, permitting and other environmental compliance services; site (stream) surveys; site designs for a variety of AOP solutions; contract preparation; and contract administration.

ETS Project Lead Dennis Vogan at Scout Creek on the La Grande Ranger District of the Wallowa-Whitman National Forest. The corrguated steel pipe culvert (left) was replaced by a prefabricated concrete, grade control structure (right) which restored the natural stream flow and connectivity.


Surveys on the Shawnee National Forest

ETS civil engineer Thomas Laurent, P.E. has been on the Shawnee conducting topographic surveys for future replacement of existing AOP structures. The staff of ETS are experts in locating, designing and constructing stream crossing structures that provide free and unrestricted movement for all swimming or crawling aquatic species. ETS offers comprehensive AOP services.

Surveys on the Shawnee National Forest
Apache-Sitgreaves National Forest

On the Apache-Sitgreaves National Forest, civil engineer Eleanor Oman and retiree Dennis Vogan are working with the Forest fish biologist, hydrologist, and engineers to replace a culvert installation at Beaver Creek. The existing twin culvert installation does not meet aquatic organism passage requirements, and 2011’s Wallow fire and subsequent rain events highlighted the crossing’s inadequacy to carry flood flows. Dennis and our land surveyor gathered site specific data to create a topographic model of the site. Eleanor is using the data to design a new crossing structure and assemble a contract package. John Slown is conducting the NEPA analysis and permitting for the site.

Beaver Creek Culvert


US Forest Service - ETS Enterprise Unit
Last Modified: Wednesday, 23 April 2014 at 14:54:54 CDT

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