GeoEngineers developed a natural habitat restoration design for a 3,000-foot reach of the Walla Walla River near Milton-Freewater, Oregon for the Confederated Tribes of the Umatilla Indian Reservation.
The Tribes were concerned about the lack of juvenile fish-rearing habitat through a reach of the river where spring Chinook and steelhead spawn each year. The Walla Walla River, through the project site and sur-
rounding reaches, has been unnaturally confined, resulting in river conditions poorly suited for juvenile rearing. The Tribes were looking for a solution that would increase fish-rearing habitat in a more natural river and floodplain setting.
To address these challenges, GeoEngineers first assessed the existing conditions at the project site and watershed. Analytic techniques included habitat assessments, geomorphic assessment, hydraulic modeling, hydrologic modeling and sediment transport analysis.
Next, GeoEngineers worked with the Tribes to develop three conceptual restoration alternatives that the project team presented to local stakeholders and regulatory agencies for comment. From that point, the team applied all the available information into a final design package, consisting of plans, specifications, contractor bid documents and a basis-of-design report. We also prepared a no-rise analysis, which documented that the design would yield a net decrease in base flood elevations throughout the project reach. The local Water Control Board reviewed the no-rise analysis favorably and the County subsequently approved it.
GeoEngineers assisted the Tribes at the pre-bid tour by describing the details of the project and answering the prospective contractors’ technical questions. Project construction occurred in summer 2011, and GeoEngineers provided construction observation and guidance to the contractor throughout the construction period.
Completing this highly technical project required a collaborative, interdisciplinary team of scientists and engineers. GeoEngineers’ interdisciplinary River Team is unique to the industry because we treat individual sites as part of the larger watershed and its processes.
Jed Volkman, Habitat Biologist
Confederated Tribes of the
Umatilla Indian Reservation