Cosumnes River Boulevard Extension and I-5 Interchange


City of Sacramento




Sacramento, CA


2010 – 2014


The Cosumnes River Boulevard Extension and I-5 Interchange project was the City of Sacramento’s largest transportation project in the last 25 years. First envisioned over 50 years ago, the project:

  • extended Cosumnes River Boulevard by 3.2 miles,
  • constructed a new interchange and 420-foot long overcrossing bridge at Interstate 5, and
  • constructed a 945-foot long bridge spanning Morrison Creek and the UPRR tracks.


Blackburn Consulting provided geotechnical consulting services during this multi-year design project. Blackburn prepared geotechnical design and materials reports for the interchange and roadway extension, and foundation reports for both bridge structures. We evaluated and provided recommendations for pavement section alternatives, sidewalks, sound walls, flood walls, culverts, bridge foundations, and protection of existing sewer pipelines that could not be relocated. Blackburn also provided geotechnical support during construction.


During PS&E design, the local sanitation district expressed concerns that construction of the planned roadway and interchange ramp embankments would damage their existing large gravity sewers and force mains. To solve this problem, Blackburn Consulting evaluated many options and recommended use of innovative lightweight cellular concrete to mitigate additional loading on the pipelines. Since this construction technique was new to the Sacramento area, Blackburn quickly coordinated a presentation given to the project stakeholders. Blackburn Consulting’s ability organize a team and clearly communicate complex technical issues culminated in approval of the pipe protection alternative. Cost estimates at the time showed the lightweight cellular concrete alternative was about half the cost of other solutions.


The Cosumnes River Boulevard Extension & I-5 Interchange project opened in December 2015.


Winner of ACEC Sierra Chapter 2016-2017 “Best Geotechnical Engineering” Project Award


Honorable Mention for CalGeo’s 2016-2017 Outstanding Project Award