Route 12 Widening Project

Jameson Canyon, Route 12 Widening Project,
Solano County

Project Dates: 1999 – 2012

Client: Solano Transportation Authority

Cost: $115 Million

Project Description: Project widened a 5.8-mile stretch of State Route 12 through Jameson Canyon Road from a two-lane highway to a four-lane highway. The project extends from Highway Route 12 from the Highway 29 and Highway 12 junction in Napa County to Red Top Road and Highway 12 in Solano County. The project improved the safety and travel times throughout the region.

Services: PARIKH Consultants, Inc. provided a Geotechnical Engineering Report, a Geologic and Seismic Report during Plan, Specification, and Estimate (PS&E) Phase. The firm prepared a detailed report including rock-slope stability analysis and design recommendations for retaining walls, embankments, and slope cuts up to 100’ in height. The firm instrumented the slope for ground water and slope stability using inclinometers with a remote sensing system and an around-the-clock monitoring program during construction.

The project utilized multi-tiered wall-systems to support the roadway realignment cuts as high as 100’, new roadways, culverts, landslide mitigation systems, drainage measures, and a bridge structure. Proximity of the cut to the existing North Bay Aqueduct (NBA) line owned by the State Department of Water Resources (DWR) required special design measures. Several major debris flow and historic landslides required tie-back walls using rock fences and soil-nail wall systems.

The site has seven deep inclinometers that are continuously monitored using a web-based remote system. This 24/7 system provided the comfort level required by DWR for the monitoring of the ground downhill of the NBA line, a major water link to Napa County area. All work was completed on time, within budget, and according to Caltrans standards.

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