Sacramento River East Levee Contract 3 - Design and Construction Challenges and Solutions-PPT Presentation

PPT Presentation

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The Sacramento River East Levee Contract 3 project improved flood protection in Sacramento’s Pocket neighborhood as part of the American River Common Features Project. Completed in 2022, the work installed approximately two miles of cutoff walls: 3,876 feet of deep mixing method (DMM), 7,116 feet of soil-bentonite (SB), and 1,100 feet of slag-cement-cement-bentonite (SCCB).<br /><br />Design took account of urban constraints, residential backyards, existing cutoff walls and utilities, prior construction problems, and a limited seasonal work window. Engineers used data from 124 borings and cone penetration tests, along with seepage and slope-stability analyses, to select wall types and depths. Fully penetrating walls were used where levee criteria or past seepage performance warranted them; partial or “stitch” walls were used where performance had been satisfactory. An existing high-voltage line beneath the alignment was mapped with a gyroscopic tool, and trench excavation was closely tracked and sounded.<br /><br />Construction brought challenges including stuck DMM augers, a broken mixing paddle, connections between different wall types, variable soil conditions, quality-control issues, and an SB slurry leak. Crews addressed stuck augers through removal, grouting, and backfilling procedures, and modified equipment to reduce recurrence. Although the broken paddle lowered calculated mixing indices, the affected elements were accepted after meeting continuity, strength, and permeability criteria. Testing also assessed the effects of constructing SB before overlapping DMM walls. At the slurry leak, excavation was paused, slurry density and viscosity were increased, and SB backfill placement was prioritized.<br /><br />The project’s central lesson was the value of close coordination among USACE, the design team, agencies, and contractors. Timely communication and collaborative problem-solving helped manage unforeseen conditions and meet the tight construction schedule.

Keywords

Sacramento River East Levee

flood protection

Pocket neighborhood

American River Common Features Project

cutoff walls

deep mixing method

soil-bentonite

slag-cement-cement-bentonite

levee construction

construction challenges