Travelers along the Rainier Avenue corridor in Renton should still expect lane closures and detours as the latest phase of the 20-year construction project comes to a close.

Late summer will bring major road paving and inevitably closures to Rainier Avenue. Renton Transportation Division Director Jim Seitz said they should be done with phase 4 of the Rainier Avenue Project by the end of the year.

Beginning June 30, the intersection at Rainier Avenue South and South Second Street will temporarily operate as a three-way stop for the next month. Police officers will be stationed during the day to help direct traffic and ensure safety while work is underway on the traffic signal and rebuilding the concrete road over the Seattle Public Utilities waterlines, according to the city. Northbound traffic will be diverted to Lake Avenue South and southbound traffic will be diverted to Shattuck Avenue South.

Seitz said Rainier Avenue is one of the older regional corridors around the Puget Sound and he estimated it was built in the 1920s. He said in the early 2000s, the Renton City Council began looking at ways to improve the corridor for the future.

“It was built for a different time, different type of vehicles,” Seitz said. “We really needed to modernize the corridor.”

Seitz said they were experiencing high accident rates along the corridor at the time because vehicles trying to access businesses along the corridor. He said the five lanes along the corridor were also not enough to accommodate the vehicles and transit on the road.

“Transit has really evolved in the Puget Sound area. We have a lot more buses on the road today and even back then,” Seitz said. “In the future we are going to have a new transit center right there on Rainier Avenue and Grady Way, so we really needed to plan for all that.”

A transportation study conducted by the city in 2005 found the corridor needs seven lines with an outside lane dedicated to transit and better managed access to businesses. Shortly after the study, the city began the multi-phased project.

The current phase, which began construction in March 2023, is focused on the section of Rainier Avenue between South 3rd Street and NW 3rd Place. The phase will include sidewalk widening with streetscaping, pedestrian-scale lighting, extension of the Lake Washington Loop Trail, pedestrian-activated traffic signals, upgrading existing traffic signals, transit improvements, including an extended business access and transit lane, and planted buffer strips and landscaped medians along the stretch of road.

Seitz said because the corridor is old, there are a lot of “surprises” crews find when they start digging into the ground that provide hurdles for construction. He said one of those surprises was finding old gas tanks, which requires examining the soil for contamination.

He said utilities not being able to keep up with construction have also delayed construction.

“At this point we are just doing surface improvements so it will be moving a lot faster,” Seitz said. “It certainly is impactful still because we’re having to pave lanes and we have to close parts of the street down.”

Seitz said phase 5 of the project will continue the road improvements up to the city limits and mainly will deal with airport frontage instead of businesses. He said design work for the next phase may take a few years, along with having to buy property, resulting in the construction not beginning for another five years, possibly.

Seitz said a project like Rainier Avenue is not much different from other projects the city does except for the scale of the work.

“We don’t do a $50 million dollar project that often. It’s one of the bigger projects we’ve done in the city,” Seitz said.