Yuba River North Training Wall
The Yuba Goldfields North Training Wall (NTW) is located on the right bank of the Yuba River, approximately six miles northeast of the city of Marysville. The NTW is approximately 12,000 feet in length, it was contructed by the California Debris Commission in 1899 to confine the Yuba River and to facilitate the migraton of mining debris within the floodway. The use of mining tailings were used to construct the NTW and although not an authorized flood control project, it does provide limited flood protection for the community of Hallwood. However, there have been changes over time, changes both in heighth and width due to mining operations in the area and erosion due to high-water events, such as in 2017 and 2018 when Hallwood experienced localized shallow flooding.
The Yuba Water Agency employed MBK Engineers to conduct an analysis, determined the potential flood risk and how a failure of the NTW would impact the community of Hallwood. As a result, Yuba County and Yuba Water Agency (YWA) recommended immediate action should be taken, which was done in 2019, but a long term solution is still needed so that 100-year flood protection can be achieved.
TRLIA has undertaken the lead role for this endeavor, assembling a team to perform preliminary engineering, design and environmental analysis for this future flood control work. An initial Flood Risk Evaluation Analysis was completed in June 2019 by Wood Rogers, Inc and MHM Engineering. The YWA has provided $1 million in grants for the initial costs and recently approved an additional $ 1 million in April 2021 so that Phase 1 work could begin (see video below for current work project footage).
The project will be constructed in two phases (Phase Map). Phase I work, in red on the map, includes the re-grading of the existing North Training Wall to provide long-term stability. The project design is now nearing completion and environmental permitting will begin in early 2021. TRLIA is seeking out additional funding sources, such as State and Federal grants to complete construction by the end of 2021. A funding source will also be needed to pay for ongoing operations and maintenance of the improved levee once completed. Phase II work, indicated in blue on the map, will "tie-in" the improved levee to the existing high-ground near the Hallwood-Cordua Canal. Design and permitting for this phase of the work is both more complicated and costly than Phase I, therefore, it will begin when additional grant funding has been secured.