Mashel River Habitat Designs RM 0-3

This project, completed on 12/31/2023, has provided a preliminary level design for the Lower Mashel River from river mile 0 to 0.8, including the confluence and the Nisqually River. The preliminary designs restoration focuses the construction of 4 different types of engineered log jams and the removal of 2 concrete bridges including piers and abutments. Road prism removal and excavation of a side channel are also included in the preliminary design. A Hydraulic analysis was provided by the consultants and guided decision making during the design phase. A conceptual design was also provided for Mashel RM 0.9-3.5. A habitat and wood assessment was completed by SPSSEG that influenced design choices. SPSSEG staff also conducted a wood and habitat assessment from Mashel RM 0-3.5, documenting habitat features such as pools, runs and riffles, as well as large woody material sizes and locations. A summary of the design alternatives, preferred alternatives, hydraulic analysis and site assessment can be found in the design reports.

Restoration Goal 1: Increase the quantity and quality of accessible off-channel habitat for rearing, juvenile salmon and steelhead. Restoration Goal 2: Improve river channel and habitat diversity for juvenile and adult salmon and steelhead. Restoration Goal 3: Improve floodplain-river connections and functions. Assessment Goal 1: Assess and update metrics for current wood loading rates and habitat features within the lower three miles of the Mashel River. Develop designs for the site specific locations as well as for wood-loading projects in the lower three miles of the Mashel River.