Graniterock's completion of the SR 156/25 Turbo Roundabout Project in San Benito County enhanced safety and traffic flow at a critical intersection, reducing collisions and improving efficiency. Despite challenges such as traffic management and weather delays, collaboration with Caltrans ensured successful project completion. The roundabout design and additional safety features have led to improved commuter experience and reduced accidents at the intersection.
Photo courtesy of Graniterock
This intersection serves commuters and important goods movement for the region and has been experiencing a pattern of broadside and rear end collisions — more than twice the number of collisions as similar intersections in California.
At the eastern end of the ongoing San Benito Route 156 Project that will be completed in fall 2025, Graniterock completed the building of the SR 156/25 Turbo Roundabout Project.
Crews began work on this project in San Benito County in June 2022.
"This was a critical safety project that immediately reduced the number and severity of collisions, while maintaining traffic flow and efficiency at the intersection," said Jim Shivers, a Caltrans District 5 public information officer. "A turbo roundabout is an innovative, new facility design that operates similar to a regular roundabout, but has additional features that reduce the potential for collisions."
Some of those additional features include:
- A second circulatory lane is inserted opposite of at least one entry lane;
- Each segment of the roundabout includes one circulatory lane from which drivers can choose whether to exit or continue around the roundabout;
- The diameter of the roundabout is kept small to encourage lower speeds through the roundabout.
- Approach legs and entry are typically at right angles to the roundabout.
Contractor Challenges
Traffic was a construction challenge in more ways than one.
"One was constructing and completing our work while also maintaining traffic on 25 and 156," said Graniterock Project Manager Mark Hurley Jr. "We weren't allowed to close any lanes during the day. We had to let all traffic through and provide at least one thru lane in each direction."
The work was divided into five stages.
"Constructing a project with that many stages is somewhat difficult, making sure that we took up from where we left off on the previous days and we're not missing any sections of our work," said Hurley.
Photo courtesy of Graniterock
Impediments also prevented the work from starting as originally scheduled.
"We had to go through a couple of winter suspensions in 2021 and when we got some clear weather in the spring of 2022," said Hurley, "we started and then realized the temporary signal plan that was provided really wasn't a way to construct that and not close or keep traffic flowing. We had to work with Caltrans and our electrical subcontractor to revise the temporary signal plans and ended up putting forward a value engineering proposal. This took the entire summer and by the time we figured all that out, we didn't get started until the beginning of winter that year and then we had some weather and the winter suspension."
This portion of work began in spring 2023 and it was continuous and on schedule. The project was delivered in February 2024 and final acceptance/completion was confirmed in April.
The majority of the work was done during day with crews protected from live traffic by K-rail.
"Towards the end of the project," said Hurley, "a lot of our paving was done at night. While there was plenty of room, it was tight for all five stages in the sense that our work butted up right against the traffic. There was only so much extra room."
As the project was beset with several challenges, cooperation between Graniterock and Caltrans was a necessity.
"Relations with Caltrans were pretty good," said Hurley. "I've worked with Baljinder Brar, the resident engineer on the project, on three previous projects and Luis Jimenez, the Caltrans inspector, was easy to work with. We all wanted to do a good job. The three of us live in Hollister — we shared that common living area and just worked together to build this project.
"The critical path for each stage had us moving the existing area — asphalt and base rock out and building a new section,"said Hurley. "That required grinding off eight to 12 inches of asphalt and removing four inches of base rock beneath, The majority of that material was reused on-site. We had a PEP screen about 1,000 feet away from the job site. We hauled the material there, screened it, and brought it back to re-use as our subbase. The excavation operations went fairly well. It was a little slower than we anticipated, but that's standard ‘not everything goes according to plan.'"
For each phase, crews excavated an area, prepped the site and paved the sections of the roundabout.
Paving operations took place at night. Graniterock supplied the asphalt.
The center circular section consists of coble and concrete.
The new lanes are 13 to 21 ft. wide, with the majority being 14 ft. wide.
"It was difficult to piece mill the paving," said Hurley "With the turns and different sections, it was like paving a parking lot."
Equipment operators used a variety of pieces of iron, including a 210 skip, 10-ft. track paver, 79-in. DD roller, 67-in. DD roller, 772 GP motor grader and an 84-in. padfoot compactor.
Hurley was assisted by an excellent team, with Foreman Brandon Cole overseeing most of the work and Foreman Ray Espino handling operations toward the end. Nick De La Torre and Marco Lopez served as the paving foremen. Also on the team were Project Engineer Todd Benson and Jeannie O'Donnell, a contract administrator who handled the paperwork.
Photo courtesy of Graniterock
"We worked well together," said Hurley. "That is just standard here at Graniterock — it's just the framework and the employees. The crews gave a 100-percent effort. They did everything that was asked of them and then some. It was a tough project, but those guys worked through the heat of summers and some of the rain of winter. Those guys went above and beyond."
Busy days required 15 people on the paving crew, five electricians and five traffic flaggers. The subcontractors were ABSL, APCO Dike, Austin Enterprises, Bear Electric, Central Striping Service, Coral Construction Company, Farwest Safety, KCI Environmental and KRC Safety.
Excavation operations generated 23,242 yds. of asphalt and subbase, New materials included Class 1 subbase and class 2 base and Asphalt.
Graniterock has a sizable fleet and takes good care of it.
"We really didn't run into any wear and tear issues on this project," said Hurley. "There weren't any issues with the work and equipment. We did have an on-site mechanic for the paving operations. It's a requirement for the field guys to inspect the equipment. Our fuel trucks make the rounds and they are on-call."
The company purchases and rents equipment from Quinn Company (Cat equipment) and Cresco Equipment Rentals
"Anytime we needed a piece of equipment, whether it was Graniterock owned or rented, our equipment department handles that for us," said Hurley. "Equipment was delivered on time and we never had any issues with our pieces or those from our vendors. The equipment department has a good relationship with the vendors."
Project Need
"This intersection serves commuters and important goods movement for the region and has been experiencing a pattern of broadside and rear end collisions — more than twice the number of collisions as similar intersections in California," he added. "Improving Highway 25 and constructing a new interchange at Highways 25 and 156 is part of Caltrans' and the Council of San Benito County Governments' [SBtCOG] vision for the region."
Planning for the project began in April 2017
Motorists are pleased with the new roundabout, said Brar.
Photo courtesy of Graniterock
"Per my office's outreach to local residents, friends and family," he said.
The three-lane roundabout with three exits replaced a standard two-lane in each direction intersection with traffic lights.
The project is fully funded through State Highway Operation & Protection Program funds (SHOPP). Construction and right-of-way costs were $11.1 million and support costs were $3.8 million.
The roundabout was designed by Caltrans, which completed its work in May 2021.
"The traffic situation has vastly improved after the opening of the turbo roundabout," said Brar. "The capacity increase has been demonstrated by the absence of commute time queues and the relative emptiness compared with the earlier signalized intersection at most times. The vehicles arrive and get flushed out of the intersection quickly. Assuming no more T-bone accidents caused by the last-minute vehicles trying to clear the intersection before it gets red has improved the safety as well. The future CHP accident data will hopefully prove it.
"The project has improved safety by increasing the highway lighting by a factor of five," he pointed out, "added lane separation curbs and median dividers, OH signs upstream to help choose lanes well in advance, dedicated right turn lanes, solved the issue of signal power outage under PG&E's PSPS program. No maintenance is needed due to power outage/faulty signal equipment/loop detector damage."
The traffic management plan was based on temporary lane closures. Construction started after the utility work was completed.
"Traffic was an issue before the project started, and somewhat of an issue during construction as far as getting materials to the job site," said Hurley, "that wasn't too big of an issue. It was just dealing with standard day-to-day commute traffic, — people coming in and out of Hollister. Some of the work was performed at night to avoid some of the traffic. Hauling asphalt at night was more ideal for us, so we didn't have trucks sitting in traffic, and now that the project has been completed, traffic is flowing much better to what it used to be with the signals." CEG
Irwin Rapoport
A journalist who started his career at a weekly community newspaper, Irwin Rapoport has written about construction and architecture for more than 15 years, as well as a variety of other subjects, such as recycling, environmental issues, business supply chains, property development, pulp and paper, agriculture, solar power and energy, and education. Getting the story right and illustrating the hard work and professionalism that goes into completing road, bridge, and building projects is important to him. A key element of his construction articles is to provide readers with an opportunity to see how general contractors and departments of transportation complete their projects and address challenges so that lessons learned can be shared with a wider audience.
Rapoport has a BA in History and a Minor in Political Science from Concordia University. His hobbies include hiking, birding, cycling, reading, going to concerts and plays, hanging out with friends and family, and architecture. He is keen to one day write an MA thesis on military and economic planning by the Great Powers prior to the start of the First World War.
Read more from Irwin Rapoport here.
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