Arroyo Grande considers changes to Brisco Road interchange

The Brisco Road and Highway 101 interchange in Arroyo Grande.
The Brisco Road and Highway 101 interchange in Arroyo Grande. jjohnston@thetribunenews.com

Arroyo Grande is once again eyeing changes to the Brisco Road interchange at Highway 101, after more than 15 years of setbacks on the project.

The latest alternatives would either close the Brisco Road on- and off-ramps permanently or relocate them to West Branch Street and Grace Lane. The latter alternative would also add the city's first roundabout at the intersection of West Branch and Rodeo Drive to help curb traffic speeds.

If one of the alternatives is chosen and makes it through a lengthy planning process, construction could start by late 2016, city officials say.

The city has examined alternatives for the interchange since 1999, when it identified a need to fix traffic congestion at the highly used interchange. The project has faced delay after delay as the city and Caltrans attempt to reach an agreement on how best to update the interchange while still maintaining the city's existing traffic patterns.

The Arroyo Grande City Council took a step forward at its March 10 meeting, when it unanimously agreed to send two possible options for the interchange through the public review process. One option would close the northbound on- and off-ramps at Brisco Road and widen the Grand Avenue bridge and road to alleviate traffic, while the other would relocate the ramps to West Branch Street and Rodeo Drive.

Historically, Caltrans has preferred the first option (called Alternative 1), while the city tends to prefer the latter (Alternative 4C) because it does not change the city's existing traffic patterns, according to a staff report.

Another aspect of the discussion was whether to add a traffic signal or roundabout to control traffic flow at the new on- and off-ramps proposed in Alternative 4C.

Caltrans expressed concerns about the viability of a traffic signal at the intersection because the posted speed limit at West Branch Street would need to be lowered from 45 mph to 35 mph — an option the City Council dismissed at its March 10 meeting.

Instead, the council voted in favor of Alternative 4C featuring a roundabout, in which the suggested speed limit of 40 mph is closer to the existing limit.

Alternative 1 is estimated to cost approximately $8.4 million, while Alternative 4C with the roundabout would cost about $15.7 million. It would be funded by a combination of capital project funds from the city, San Luis Obispo Council of Governments and CalTrans.

Caltrans, city and county staff will now take both alternatives to a project development meeting, where they will determine which option satisfies all parties. The project's environmental documents will also be drafted at that time. If approved, the next step would be to circulate the plans for public review.