California’s Interstate 680 runs north to south in Northern California. Built in the 1920s, the 70-mile I-680 goes from near Fairfield to San Jose. Among the cities I-680 passes are San Ramon and Sunol. The California Department of Transportation (Caltrans) is in the middle of a project on I-680 that will create a smoother ride for drivers.

The I-680 paving project covers an approximately 9-mile stretch of the interstate. The pavement is in poor condition. Cracks and potholes dot this stretch of I-680. The project has been in the works for approximately five years but has been delayed, due in part to the pandemic.

“We’ve been out there patching along route I-680 regularly,” says Lakshmanan Senthil Kumar, a Supervising Transportation Engineer for Caltrans, “but those are temporary fixes.”

Kumar notes that Caltrans has gotten complaints from the public about the pavement. This stretch of highway is approximately 30 miles from Silicon Valley and serves as a corridor to the state’s primary economic engine.

No more temporary fixes, the team is removing and replacing the pavement. According to Kumar, the team will go down and remove approximately 1.5 feet of the existing roadway before replacing the pavement. Along this stretch, there are 6 miles of concrete and 3 miles of asphalt pavement. “The surface is dependent on the subsurface materials,” Kumar says, “the materials team does an analysis and we design the surface based on their findings and suggestions.”

The project will also include minor drainage improvements.

The team is constructing the project in three segments, starting in the south end. The team decided to use precast concrete panels on the route. While precast costs more than cast-in-place concrete, it’s faster. “We’re only allowed five to six hours of lane closures each night,” Kumar says. “When you put down precast panels, you can put traffic on it the next morning.” They’re also simple to lay on site – “like a jigsaw puzzle, just drop it one by one.”

The panels for the project are 12 feet wide by 15 feet long. The state has certain restrictions regarding the size of the panels. The bigger the panel, the greater the cost.

To make the panels and have them ready to be laid takes 20 to 25 days. Before starting the time-consuming process, the team measured the lanes. They found the slow lane, adjacent to the right shoulder, was wider than the other two so they determined that the precast panel would not be a good solution.

The team had to decide how to proceed. “The general contractor, Security Paving, did a great job handling the third lane issue,” Kumar says. Their suggestion was to do a traditional concrete pour, but there was a question of how the team could keep I-680 open as the contract required.

It was decided that there would be four holiday weekend closures of I-680 – Martin Luther King Jr. Day, President’s Day, Memorial Day, and Labor Day. Other than those long weekends, the only lane closures would occur at night as originally stipulated.

Unfortunately, due to bad weather, Martin Luther King Jr. weekend was a washout. Security Paving suggested closing I-680 on a regular weekend, which meant one less day of closures.

Crews were able to lay 6,000 feet of concrete on the third lane over that weekend and stay on schedule.

The next weekend was President’s Day weekend and the team put down 7,500 feet of concrete. The great progress enabled them to open the lane up on Monday afternoon, rather than Tuesday at 5:00 a.m. as planned.

“We decided to lay the final 5,000 feet of concrete on a regular weekend since the process was going so well,” Kumar says. “The contractor and the whole team did a great job to make the process go faster.”

Some have called the weather of winter of 2022-2023 the worst California has ever seen. Volatile weather can be costly in many ways, including construction timelines.

However, the I-680 paving project – which began in December 2022 and is scheduled to run until April 2024 – is currently on schedule. “Even with all the extreme weather, we’re still on schedule which makes us have confidence we can complete the project as scheduled,” Kumar says.

The $71 million project is financed with State Highway Operation and Protection Program (SHOPP) funds, a California financing mechanism for infrastructure projects. As of now, the project is on budget, and Kumar is optimistic it will continue as he doesn’t anticipate serious issues.

Kumar and Caltrans District Four are working with Security Paving, a Southern California company, for the first time. He notes they came highly recommended by others in Caltrans. After working with them on this project, he’s been impressed. “They are easy to work with, they accommodate our requests, focus on safety, and are cooperative,” Kumar says.

When the project is complete, drivers in the area – and those on their way to or from Silicon Valley – will enjoy a smoother ride. “We believe it will make the ride to work more pleasant and allow people to enjoy the scenic route,” Kumar says.