Sacramento River East Levee Contract 4 – Seepage Cutoff Wall Construction Challenges and Solutions-Paper

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The Sacramento River East Levee Contract 4 project installed seepage cutoff walls at several high-risk locations to reduce flood threats to Sacramento’s infrastructure. Construction used deep mix method (DMM) and jet grouting, with methods adapted to site constraints and changing field conditions.<br /><br />At Edwards Break, a historic levee breach with loose, debris-rich fill lay beside an operating hotel and restaurant. Triple-fluid jet grouting encountered buried wood, lost grout and drilling returns, grout flow between columns, and sinkholes. The team added single-fluid stabilization columns, adopted staged grouting to limit instability, monitored ground movement, and increased verification coring. Structural inspections and a sound barrier helped protect the nearby facility.<br /><br />At Sump 132, jet grouting was selected so existing drainage pipes could remain in place. Unexpected wood, dense gravel, and cobbles slowed drilling and caused column deviations; achieving the required overlap with an existing DMM wall was also difficult. Air bubbles observed in the river prompted changes to work sequencing and contingency procedures, alongside ongoing monitoring and water-testing protocols. Construction took about 100 days longer than planned.<br /><br />At Cliff’s Marina and downstream of Edwards Break, the contractor proposed DMM in place of planned methods, citing access and schedule benefits. These changes were accepted through contract flexibility. DMM construction also revealed challenges with coring and testing, while shallow cavities found at the top of one wall were repaired with controlled low-strength material.<br /><br />Quality assurance included verticality measurements, overlap reviews, coring, laboratory and in-situ testing, and analysis of jet-grouting data. The project’s successful completion depended on close coordination among the contractor, engineers, and construction oversight teams, enabling timely responses to unforeseen ground conditions and risks.

Keywords

Sacramento River East Levee

Contract 4

seepage cutoff walls

deep mix method

jet grouting

Edwards Break

Sump 132

levee breach

quality assurance

flood protection