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

PPT Presentation

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The Sacramento River East Levee Contract 4 project addressed seepage and breach risks at several locations along the levee. Work included closing a 55-foot gap in an existing cutoff wall near a high-pressure gas line, building a 1,427-foot wall at the historic Edwards Break and Little Pocket area, deepening the cutoff wall at Sump 132, and extending improvements near Cliffs Marina.<br /><br />Deep Mix Method (DMM) walls were used where access or site constraints made open-trench construction impractical. At Little Pocket, the contractor chose DMM over a soil-bentonite trench wall. A required test section was waived in favor of the contractor’s relevant experience, with increased verification testing instead. One in-situ permeability test failed, likely because the corehole deviated and missed the wall; satisfactory laboratory results from core samples supported acceptance. Cavities found at the exposed wall top were excavated and filled with controlled low-strength material. At Cliffs Marina, a DMM wall replaced jet grouting as a value-engineering alternative, reducing cost and schedule while keeping SR160 open during construction.<br /><br />Triple-fluid jet grouting was used at Broadway, Edwards Break, and Sump 132, where utilities, historic breach fill, and existing infrastructure constrained other methods. At Broadway, modified equipment provided clearance from the gas line without reducing cutoff depth. At Edwards Break, sinkholes threatened worker safety, rig stability, and nearby building foundations. Shallow support columns, monitoring, and staged grouting reduced sinkhole formation, though buried debris and voids caused delays and grout loss. At Sump 132, dense gravel, cobbles, and buried wood led to drilling deviation, clogged pumps, and rework.<br /><br />Jet-grout acceptance included geometry, strength, permeability, continuity, and construction parameters. Statistical analysis of recorded jetting and grouting data helped identify outliers and guide coring locations; specific energy had to meet at least 90% of design values. The project’s solutions balanced seepage protection, construction constraints, safety, cost, and schedule.

Keywords

Sacramento River East Levee

Contract 4

seepage control

cutoff wall

Deep Mix Method

jet grouting

levee rehabilitation

sinkhole mitigation

permeability testing

value engineering