Prado Road/Hwy. 101 overpass construction could start in 2021

After decades of talk, construction of the Highway 101 freeway overpass and interchange at Prado Road in San Luis Obispo is expected to start in 2021 — and be finished by 2023.

It’s critical to accommodate growth from two major housing developments — San Luis Ranch off Dalidio Road and Avila Ranch off Buckley Road, both in the southern part of the city, city officials say.

“In my mind, it’s the single most important transportation facility project in the city and the highest priority for transportation funding,” said San Luis Obispo City Manager Derek Johnson. It will provide a straight connection between the west and east side of the city and a regional connection between Highway 227 and Highway 101, he added.

The current plan for the interchange project is projected to include an overpass bridge, northbound on-ramps and off-ramps and a northbound auxiliary lane between Prado and Madonna roads.

Southbound ramps, which would add to the cost, aren’t currently part of the project. That’s because the city’s traffic projection models show that increased volumes and backups of cars wouldn’t exceed standards until the city’s population hits 56,686 — close to what the city considers to be its maximum size, or full build out, of 57,000.

That would occur by 2035 based on the city’s 1 percent annual growth limit, according to an estimate in the city’s General Plan. The population was estimated to be 47,536 in 2016, according to the U.S. Census Bureau.

Jake Hudson, the city’s transportation manager, said the project is essential to supporting long-term growth.

“The overpass will allow acceptable levels of congestion and without it, we’ll have too much,” Hudson said.

The funding for the project must be in place by the time the second phase of construction begins for the approved San Luis Ranch development. That project is slated for 580 homes; the first phase includes 86 homes while the second phase would add 196 homes.

The specific plan calls for the first phase to begin construction in 2018 and the second phase in 2019. But those dates are subject to change.

San Luis Ranch will be built on a 131-acre site bordering Madonna Road and Highway 101.

Johnson said the project has yet to secure all of the funding the city will need to pay for the work.

Developer Gary Grossman is being required to pay 28 percent of the cost of the interchange.

Besides Grossman’s approximate one-third share, roughly a third will come from sources administered regionally by the San Luis Obispo Council of Governments, and roughly a third from city fees such as developer impact fees.

SB 1, a 10-year, statewide transportation tax approved this year by the Legislature, will contribute to the transportation fund pool that could be used to help pay for the project, according to city officials. The tax will generate an estimated $10 million per year for road repair and maintenance in San Luis Obispo County when it’s fully implemented.

Johnson said that the planned project’s funding has high priority in the region and wide support from local government leaders, topping the priority list of a recent regional transportation plan.

Existing northbound ramps currently allow a freeway entrance north and the project would maintain that northbound freeway connection, serving commuters, buses, shoppers and visitors who frequent the corridor on a daily basis.

The city is the lead agency in the planning of the project. But approvals will be made by both the city and the California Department of Transportation (Caltrans), which has the final decision authority.

The interchange project is expected to take about 18 months to complete, Johnson said.

Caltrans is closely involved with the planning, working with the city to ensure the project will meet its regulatory and safety requirements.

“We’re reviewing their work to make sure it meets our standards from a safety and operational standpoint,” said Paul Valadao, Caltrans project manager.

This story was originally published November 20, 2017 at 6:02 PM with the headline "Prado Road/Hwy. 101 overpass construction could start in 2021."