Ninilchik River Fish Passage Culvert Design
Trihydro worked with the Ninilchik Native Association and the US Fish and Wildlife Service to create a fish passage culvert design that improves aquatic organism passage and habitat in a tributary of the Ninilchik River.
Trihydro worked with the Ninilchik Native Association, Inc. (NNAI), and the US Fish and Wildlife Service (USFWS) to design a culvert to accommodate fish passage for a tributary to the Ninilchik River on NNAI land west of Ninilchik, Alaska. The existing crossing was a 5-foot by 5.5-foot corrugated metal pipe, steep and undersized, preventing fish and other aquatic organisms from accessing upstream spawning areas. The project aimed to identify and design fish passage options that improve aquatic organism habitat and passage.
Surveying and Assessments
Our team completed a site survey, reference reach analysis, pebble counts and stream assessments, hydrologic/hydraulic (H/H) analysis and reporting, plan set preparation, specifications, and a construction cost estimate. We also actively worked with the NNAI and the USFWS to assist with permitting.
Culvert Design
Trihydro designed the culvert to meet USFWS Culvert Design Guidelines for Ecological Function (Revision 6). It also effectively passes stream flows, including 100-year flood levels, without significant damage or erosion, and meets stream simulation objectives and road surface elevation constraints. The final design resulted in the installation of a new 10.5-foot corrugated metal pipe.
