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 4 involved construction of seepage cutoff walls at 4 separate locations in 2023 and 2024 in an urban environment. Contract 4 flood protection features are intended to reduce the flooding risk to critical infrastructure in Sacramento, California. The project was constructed through a USACE Sacramento District contract and were supported by Kleinfelder and Stantec, who provided engineering during construction services related to civil and geotechnical engineering.
This paper discusses the challenges encountered and solutions adopted during jet grout and Deep Mix Method (DMM) cutoff walls. Triple fluid jet grouting was selected to close a 200-foot-long gap beneath a 100-foot-deep existing seepage cutoff wall, which required a vertical and horizontal overlap. Challenges included jet grouting to a depth of 140 feet through gravels, cobbles, and buried trees and verification of the required overlaps. A second triple fluid jet grout cutoff wall was constructed through a 100-year-old levee breach adjacent to a hotel and restaurant facility. Jet grouting through the breach fill was problematic with grout losses, shallow sinkholes, and difficult drilling conditions. Supplemental single fluid jet grout stabilization columns, staged grouting, and extensive monitoring were performed to help prevent damage to the hotel and restaurant. DMM was used to replace a proposed open trench soil-bentonite cutoff wall and to replace a proposed jet grout cutoff wall. In each case, accessibility and reduced schedule were the main driver for the replacement. Contract flexibility was important to allow for these changes. Jet grout cutoff wall verification was done through verticality readings of each column, graphical overlap reports, coring, and in situ testing. The paper emphasizes the importance of collaboration during construction, construction sequencing, challenges created by triple fluid jet grouting in levee breach fill, and the solutions developed to overcome those challenges.
