Storm Drainage & Master Planning

State Route 12/Jameson Canyon Widening Project | Napa and Solano Counties, California

State Route 12
State Route 12
Solano Transportation Authority
Project Description:
The project proposes to widen State Route 12/Jameson Canyon Road from a two-lane to a four-lane rural highway. As part of the project team, WRECO is responsible for analyzing the existing and proposed on- and off-site hydrology and hydraulics and designing on-site drainage systems to adhere to current drainage design criteria. Analyses of the existing off-site drainage were performed to determine the locations where cross culverts would require extension or replacement due to capacity or condition. WRECO proposes to extend, upsize, and replace many existing cross culverts throughout the project to meet current Caltrans design criteria.

WRECO is also incorporating the use of treatment Best Management Practices (BMPs) for stormwater treatment and to address potential hydromodification issues from the project. These measures are proposed to minimize the impacts of potential increase of sediment and pollutants and to help control the flow resulting from the increase of impervious area from the project.

In addition, biofiltration swales, strips and underground detention in pipes with water quality weirs are proposed for the project. These treatment devices allow for stormwater treatment through filtration of pollutants, while also promoting infiltration of runoff. To maximize the effectiveness of these devices, off-site flows are separated from the treated on-site runoff through the incorporation of ditches placed upstream of the device in areas of cut. Biofiltration swales include underdrain systems, and biofiltration strips include a layer of compost to promote infiltration as a hydromodification mitigation measure.

The project will maintain the overall existing drainage pattern of the area.

Key Tasks:
Drainage PS&E, Drainage Report, Stormwater BMP Design, Storm Water Data Report, Hydromodification Analysis and Mitigation Design
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