Abstract:
Sacramento River East Levee (SREL), part of American River Common Features (ARCF) 2016 Project, is being executed by USACE under four different contracts. The project assumes significance due to its location and important from for public safety and asset protection. Contract 3 involved design and construction of two miles of cutoff wall with design in 2020/2021 and construction in 2022. Contract 3 flood protection features are intended to reduce the flooding risk to critical infrastructure in Sacramento, California. Kleinfelder and Stantec supported USACE Sacramento District (SPK) on the design of SREL Contract 3 and provided engineering during construction services related to civil and geotechnical engineering.
This paper discusses the challenges encountered and solutions adopted during the design and construction of 2,730 feet of deep mixing method (DMM) cutoff wall, 5,900 feet of soil-bentonite (SB) cutoff wall, and 1,100 feet of Slag-Cement-Cement-Bentonite (SCCB) cutoff wall. Each cutoff wall method was selected based on existing site and ground conditions and the goals of the design. Design challenges included selecting reaches for fully penetrating and partially penetrating cutoff walls, avoiding a horizontally drilled utility near the bottom of a cutoff wall, construction through an area of soft soil that had slurry leaks during a previous shallow cutoff wall project, and method selection. During construction, the DMM wall encountered challenges due to use of air pressure through the drill stems, multiple instances of stuck augers in the ground, and the impact on mixing index due to a broken paddle on the auger. The challenges with open trench SB and SCCB walls included confirmation of the tie-in layer, interpretation of trench sounding data, a slurry leak, encountering buried trees, and quality control issues. The paper emphasizes the importance of collaboration during design, construction sequencing, and challenges created by using multiple cutoff wall types including cutoff wall tie-in locations.