The City of Arroyo Grande (City) proposed to rehabilitate the historic, 112-year-old Bridge Street Bridge over Arroyo Grande Creek. The bridge is a primary thoroughfare and provides vehicular access over Arroyo Grande Creek, which runs through the City approximately parallel to State Route 227. The need for improvements was to provide improvements for public safety and address some age-related deficiencies that included an increase of the load carrying capacity. The rehabilitated bridge will look much the same as the existing bridge as no structural changes are being made to the existing historic green trusses, shown in the photo. The overall project costs are $9.1M and is being funded through the Federal Highway Bridge Program (HBP).
WRECO is providing hydrologic and hydraulic services for the City of Arroyo Grande. Lopez Lake is located within the bridge’s watershed, approximately 9 miles upstream of the mouth to the Pacific Ocean. For the project, WRECO performed a hydrologic study, a hydraulic analysis to determine the design water surface elevations and flow velocities for the existing and proposed bridge, a scour analysis to estimate potential scour depths for the proposed bridge, and scour countermeasure analyses and recommendations for the proposed bridge. WRECO documented these results in the Location Hydraulic Study and Bridge Design Hydraulic Study reports.
This project also includes habitat mitigation which will offset any adverse impacts to the riparian and wetland habitats surrounding the bridge. WRECO is responsible for developing the plant palette, planting plan, and specification sheets for the revegetation plan to restore the areas of the project site that were temporarily and permanently impacted. The planting will take place in early 2021 and will be monitored and maintained over a 5-year window.