Levee evaluations for the SJRRP identify the need to remediate levees to convey Restoration Flows.
Priority 1 and Priority 2 Levee Geotechnical Evaluations: The San Joaquin Levee Evaluation Project is being implemented by DWR to conduct geotechnical evaluations of the flood control system integrity associated with levee seepage and stability on high-priority levees in the Restoration Area. To limit the risk of levee failure due to the release of Restoration Flows, channel capacities are limited to flow levels that would meet the U.S. Army Corps of Engineers (USACE) factors of safety for levee slope stability and underseepage. If data on the levees is not available to evaluate seepage and stability conditions, flows are limited to those that would remain “in-channel” until adequate data are available. From the initial geotechnical analysis findings, high flood hazards were identified for most San Joaquin River Restoration Program (SJRRP) levees. DWR has prioritized its geotechnical exploration based on current channel capacity limitations and anticipated Restoration Flow routing.
Priority 1 levee evaluations in Reach 2A, the lower portion of Reach 4A, and the middle Eastside Bypass are complete. The results showed that only one levee segment in these reaches — 2 miles of the right back of the Eastside Bypass below Sand Slough — cannot convey at least 2,500 cfs without exceeding USACE criteria. The 2-mile segment of levee was identified for improvements and DWR completed a Basis of Design report for this levee segment in 2017; 95% designs were completed in 2018. The levee improvement project is scheduled for construction in 2019.
Geotechnical evaluations also continued on the Priority 2 levees, which include the Mariposa Bypass and Reach 4B2. Data was collected on these levee segments in 2016. Geotechnical evaluations on the levees were completed in 2018 and a Geotechnical Conditions Report will be released in 2019. The report will include remediation alternatives and cost estimates that will help the SJRRP determine the costs of improving these levees under the Reach 4B, Eastside Bypass, and Mariposa Bypass Channel and Structural Improvements Project.
2019 Channel Capacity Report
2018 Channel Capacity Report