Reach 4B of the San Joaquin River is a 32.5-mile stretch that begins at the Sand Slough Control Structure and extends to the confluence of the Eastside Bypass and San Joaquin. Reach 4B has been further divided into two subreaches; Reach 4B1 from the Sand Slough Control Structure to the Mariposa Bypass, and Reach 4B2 from the Mariposa Bypass to the confluence of the Eastside Bypass and the San Joaquin River.
Reach 4B and Eastside Bypass project consists of incorporating new floodplain and related riparian habitat to ensure conveyance of at least 4,500 cfs through Reach 4B, modifications to ensure fish passage, and modifications in the Eastside and Mariposa bypass channels to support anadromous fish migration. To date, modifications have only taken place in the Eastside Bypass in order to help achieve these objectives called for in the Settlement.
The Reach O Levee Improvements Project was completed in 2020 and information about that project can be found here. In the future, other work is expected to be conducted at the Eastside Bypass Control Structure to improve fish passage, including construction of a rock ramp which will allow salmon and other native fish passage through the structure.
Fish passage improvements have also been made to portions of the Eastside Bypass adjacent to the Merced National Wildlife Refuge. In close coordination with the US Fish & Wildlife Service, which oversees use of the weirs, the two weirs were removed from the bypass channel. The weirs, which were constructed to create seasonal pools for migratory birds on the Refuge, were a partial barrier to adult Chinook salmon and many other native fish. The Program also has coordinated with the refuge to provide an alternate water supply to Refuge wetlands.
The first weir heading upstream, the lower weir, was removed in September 2019 as part of the San Joaquin River Restoration Program’s Eastside Bypass Improvements Project.
Below, a time-lapse video shows removal of the lower weir.
The upper weir was removed in the summer of 2021. Together, the removals will improve fish passage in the Eastside Bypass. Below are several photos showing the removal.
L to R: Clearing vegetation from the upper weir; saw cutting the weir abutments; removing abutments using the excavator; removal complete.
The Eastside Bypass Improvements Project Initial Study/Final Environmental Assessment consists of the December 2017 Draft IS/EA (Part 1, Part 2, Part 3, Part 4), the Finding of No Significant Impact and Air Quality and Greenhouse Gas Emissions; Biological Resources (Appendices A and B); public comments received (Appendix C); responses to public comments and minor text changes to the EA/IS (Appendix D); Endangered Species Act compliance documentation (Appendix E); and, National Historic Preservation Act Section 106 compliance documentation (Appendix F).
The Draft Technical Summary Report was prepared by the San Joaquin River Restoration Program Team to document technical studies completed as part of the Reach 4B, Eastside Bypass, and Mariposa Bypass Channel and Structural Improvements. Studies in this area started in 2009; this Technical Summary Report documents key technical findings and summarizes the work that led to these findings. The report describes the differences between the routes for high flows through this area and compares these routes. Finally, it identifies potential near-term actions (in addition to the Eastside Bypass Improvements Project) that could provide benefits regardless of the high flow alternative selected. Appendices for this draft technical report include Timing of Flow Analysis (A); Hydraulic and Sediment Studies ( B, Parts 1, 2, 3, 4, 5); Vegetation and Wildlife (C); Soils (D); Wetland Offset (E); Groundwater Analysis (F); Fisheries (G); and, Cultural Resources (H).