Feather River West Levee Rehabilitation

SBFCA initiated the FRWL project to rehabilitate approximately 44 miles of levee to reduce flood risk and eventually remove more than 34,000 properties from FEMA’s Special Flood Hazard Areas between Thermolito Afterbay and the Feather River’s confluence with the Sutter Bypass. Engineers identified that west bank levees were susceptible to under-seepage and through-seepage, which caused major levee failures in Yuba City and County. To repair and strengthen the levees, the project included: correction of levee slope geometry, installation of shallow and deep cutoff walls, reconstruction of pump stations and canals, embankment construction, levee patrol roads, and access ramps.

 

Blackburn Consulting provided geotechnical services for project area A. We completed subsurface exploration, laboratory tests, and engineering analysis to prepare geotechnical recommendations for project design. Our reports included recommendations for potential borrow sites and mitigation of seepage, slope stability, and settlement. To determine design parameters, Blackburn reviewed mountains of data (over a hundred existing boring logs and a thousand laboratory test results) and performed statistical analysis.

 

For project areas B, C, D, Gaps, and Laurel Avenue, Blackburn provided materials testing and inspection services. Blackburn supported the construction management team through quality assurance testing. Blackburn performed all aspects of quality assurance testing related to:

• embankment fill,
• clay core,
• pipe removal and realignments,
• pump station realignments,
• open trench soil bentonite and deep mix method cutoff walls,
• borrow site analysis,
• relief well repair, and
• levee road reconstruction.

Blackburn set up a fully functioning USACE-certified laboratory at the project site to expedite laboratory analysis and turnaround time of results.

 

SBFCA assembled an experienced team to construct the project on an aggressive schedule. During construction, quality control (QC) lab test results indicated soils from valuable borrow sites were not meeting specification and may need to be rejected. Our QA lab results showed the borrow site material met specification, so we determined to discover the cause of the discrepancy. We evaluated the testing procedures between the two labs and concluded that differing sample preparation methods were the cause of the discrepancies. After standardization of sample preparation methods, the test discrepancies were negligible. Our quick response and thorough investigation resulted in the acceptance of borrow site soils and avoidance of a major construction delay.

“BCI has been a very valuable part of SBFCA’s Construction Management team on the Feather River West Levee Project (FRWLP).  The extensive Materials Testing work performed by Blackburn was an instrumental component of the FRWLP Quality Assurance program.  Blackburn also assisted in resolving some very difficult issues during construction and provided valuable problem-solving skills to help keep the project running smoothly.” – Michael Bessette, PE, Interim Executive Director of SBFCA