This project included aquatic organism passage (AOP) design at three culvert replacement sites near Kettle Falls, Washington on the Colville National Forest. All three sites required open-bottom structural plate arches on precast concrete footings. During the first phase of the project, The DJ&A crew accompanied Forest Service personnel to the sites to evaluate site conditions, discuss the scope of work for the repair design task order, and repair priorities.
The second phase of the project included topographic surveys, hydrologic and geomorphic investigation and analysis, and the creation of a preliminary plan set. This preliminary design submittal allowed the USFS to review the size, span, and location of the structure and comment on the design details.
The third and final phase included two more design submittals; the 95% addressing USFS comments, and the final design. As with most AOP projects, this phase also included a full bid package for the Forest Service to advertise for construction. The bid package was organized into base and option schedules to maximize use of available construction funds. Within the design specifications, DJ&A utilized the Standard Specifications for Construction of Roads and Bridges on Federal Highway Projects, FP-14, as we do with all of our federal road projects.
- Designed three culverts sized to be greater than bank full width, as determined by DJ&A Fluvial Geomorphologist
- Provided hydraulic modeling to determine aquatic passage design criteria
- Determined optimal culvert alignment and burial depth for both the resource and the road from a longitudinal profile analysis
- Used 2015 USDA Forest Service Stream Simulation Methodology to determine class size within the design AOP structures
Two of the sites were located on remote, exceptionally low volume roads and as a result, the DJ&A design team was able to modify the horizontal road design to accommodate the adjoining narrow road tread widths.