Tank Farm Road and Orcutt Road Roundabout

The City of San Luis Obispo is pleased to nominate the Tank Farm Road and Orcutt Road Roundabout for a Save California Streets Award, Efficient and Sustainable Road Maintenance, Construction and Reconstruction Projects category. As a complex effort at the gateway of San Luis Obispo, this project benefitted from an exemplary alliance between the City, designer, construction manager, and contractor—presenting one unified team to meet and mitigate challenges throughout the project lifecycle.

This high-priority transportation project constructed a roundabout at the heavily travelled intersection of Tank Farm Road and Orcutt Road, reconfiguring the intersection from side-street stop-control to a four-legged roundabout. The project relieves lengthy delays and vehicle queues during peak commute periods, improves safety, reduces long-term maintenance costs and reduced greenhouse gas (GHG) emissions.

Construction for the project began in September 2021 and was completed in August 2022. Final construction costs were $4.1M, and the project was completed within budget.

The project overcame several challenges before and during construction, with GHD’s design team, Cannon’s construction management team, Souza Construction as the contractor, and the City collaborating to implement innovative solutions throughout the project.

Existing Utilities
The project required the preservation of various utilities, including a PG&E high voltage utility vault and AT&T cabinet, and relocation/undergrounding of exiting PG&E power poles. This required an iterative design to preserve certain elements within the project area, as well as leveraging existing relationships during construction with the Utility companies to foster quick, mutually beneficial solutions.

Project Footprint Constraints
The project area and its approaches had various features requiring adaptation of the roundabout’s footprint and design. Right of way dedication was only feasible on one corner of the intersection partially dictating where the central island could be located.

The project site also has two stream channels running through it, as well as two existing culverts, all requiring modification. Jurisdictional permits were required for alterations to the creeks, and minimizing environmental impacts was a priority.

Construction Phasing
The intersection of Tank Farm and Orcutt Roads is heavily travelled, particularly by commuters to and from San Luis Obispo to southern cities including Arroyo Grande and Pismo Beach. To minimize disruptions, construction included implementation of a temporary two-way bypass route to continue accommodating the heaviest volume movement during certain stages of construction.

Stormwater Capture
The impervious surface area of the new roundabout increases the peak run-off from the site compared to the previous existing condition. To mitigate this increase, a new biofiltration basin provides treatment and detention of runoff.