State Route (SR) 37 Sears Point to Mare Island Improvement Project

The State Route 37 Sears Point to Mare Island Improvement Project, managed by Caltrans District 4, involves extensive infrastructure upgrades across Napa, Sonoma, and Solano counties. The scope of work includes reconfiguring highway lanes from west of the SR 121 intersection to the Walnut Avenue Overcrossing at Mare Island, replacing the Tolay Creek Bridge, and widening the Sonoma Creek Bridge. Key construction elements include adding through lanes to provide two lanes in each direction consisting of tolled general purpose and High Occupancy Vehicle lanes, constructing 8-foot shoulders (with 4-foot shoulders at the Sonoma Creek Bridge), and signalizing the SR 37/Noble Road intersection. Additionally, the project incorporates safety enhancements such as CHP enforcement areas, maintenance vehicle pullouts, traffic control devices, and changeable message signs, while also focusing on the restoration of degraded marsh habitat at Strip Marsh East. The project has undergone rigorous environmental review in compliance with the California Environmental Quality Act, including the preparation of an Environmental Impact Report, an Addendum, and a Supplemental Environmental Impact Report. Official Notices of Determination filed in late 2025 and 2026 confirm that the project will not have a significant effect on the environment, provided that adopted mitigation measures and a monitoring plan are implemented. Administrative oversight is led by Senior Environmental Scientist Skylar Nguyen and Associate Deputy Director Cherry Zamora, with the project's environmental filing fees processed through the California Department of Fish and Wildlife.