SR 70 Corridor Improvements

Mark Thomas led the preliminary design and environmental clearance phases for the SR 70 Corridor Improvement Project, the highest priority for Caltrans District 3 and the Butte County Association of Governments (BCAG). The 24-mile corridor between Marysville and Oroville in Yuba and Butte counties experienced a high rate of accidents, including 11 fatalities within two years, prompting the need to widen SR 70 from two to four lanes.

Mark Thomas collaborated closely with Caltrans to complete the PA&ED phase and identify priority segments for construction, using a phased approach that defined independent, fundable, and NEPA-clearable highway segments. The PID provided a detailed cost breakdown to support long-term funding, with Caltrans and BCAG co-sponsoring the effort. While the PID covered the full corridor, PA&ED was developed segment by segment, beginning in Butte County and progressing south. The approach required consistent coordination with Caltrans staff, who completed final design.