Jameson Canyon Road SR 12 Widening Project, Solano County, CA

The project realigned and widened the five-mile-long segment of Jameson Canyon Road (Route 12) from two to four lanes between Red Top Road and Route 29 in Napa and Solano Counties, California. To accommodate the new configuration, the project required excavation into rock slope up to 150 feet high, which is supported by multi-tier soil nail walls.

PARIKH is the geotechnical engineer of record who:

  • Conducted the investigation including borings up to 150 feet deep on steep terrain with oriented rock coring and down-hole televiewer,
  • Collaborated with Caltrans’ earth retaining system (ERS) specialist to develop an approach for designing the multi-tier soil nail walls,
  • Performed engineering analyses according to AASHTO LRFD Specifications with Caltrans amendment,
  • Provided geotechnical recommendations for ten retaining walls (multi-tier soil nail walls, tieback walls, and conventional semi-gravity walls), two private access bridges, and pavement, and
  • Installed inclinometers and piezometers to monitor the slope real time during design and construction.

The project received ACEC 2015 Engineering Excellence Award.

Project Details




Solano Transportation Authority (STA)


Mark Thomas & Co., Inc.


Gary Parikh
Frank Wang

Project Gallery

Jameson Canyon Road SR 12 Widening 1
Jameson Canyon Road SR 12 Widening 2
Jameson Canyon Road SR 12 Widening 3