“We chopped 50 percent off the contract schedule,” says Jim Swenson, licensed professional land surveyor for Oregon Mainline Paving based in McMinnville, OR.
That’s 50 percent less worker hours, 50 percent less machine time, 50 percent less costs.
“The project was completed a year ahead of the two-year schedule,” Swenson says. “We finished the project so quickly due to long hours of hard work and our use of machine control technology.”
The project: Milling and repaving 19 miles of I-84, Baldock Slough — South Baker Interchange section located in Baker City, OR. The Oregon Department of Transportation (ODOT) project had a $17,949,200 contract value and Oregon Mainline Paving was the general contractor on the project.
The I-84 project involves two eastbound and two westbound lanes. When completed, it is expected to improve travel on a stretch that was originally part of the Oregon Trail, which was the 2,000-mile historic east-west wagon route and emigrant trail that connected the Missouri River to valleys in Oregon and locations in between.
The I-84, Baldock Slough — South Baker Interchange project came with challenges.
“ODOT has implemented different surfaces for the fast and slow lanes on two-lane interstates,” says Swenson. “The fast lane has an asphalt finished surface while the right-hand lane is concrete, plus there are asphalt shoulder lanes flanking both lanes.”
ODOT took the existing road surface profile but didn’t mimic that surface exactly. Instead of going all the way down to subgrade and building it back, they are requiring Oregon Mainline Paving to grind off the existing asphalt to establish the bottom for the new road surfaces.
“In the concrete lane, we were milling eight to 10 inches, and then there were some short bridge sections, where we actually went down a foot,” Swenson states. “For the fast lane surface we were milling two to four inches, the fast lane shoulder we milled zero to two inches, and the slow lane shoulder called for a three-inch grind. So, there were four different depths of asphalt ground across the road section.”
To handle this complex milling project, Oregon Mainline Paving purchased a new Wirtgen W2100 cold milling machine and then contacted SITECH Oregon, located in Portland for assistance in selecting the right Trimble machine control system.
“We’ve worked with Trimble systems before, so we knew the quality of the systems and that the dealer could help,” says Swenson. “We outfitted the new Wirtgen with Trimble 3D milling which is the GCS900 Grade Control System with a SPS930 Universal Total Station, so we could mill surfaces at variable depths and slopes without stringlines.”
The technology on a mill machine is designed to control the cutting depth of the mill to minimize over-cutting, create a smoother surface, and reduce the need for additional asphalt or concrete material in the ensuing re-paving process.
Technology places project ahead of schedule
Oregon Mainline Paving received a site model and design information from ODOT, which SITECH Oregon converted for them into a 3D model using Business Center-HCE. Business Center-HCE completed the data preparation for the Trimble machine control and site positioning systems.
“We were confident that the technology would save us a year of production,” Swenson states. “When we met with the ODOT officials at the beginning of the project, they said: ‘We were hoping someone would bring in machine control but we’re looking at your timetable, and there’s no way you’re going to get this done in a year’ and we said, ‘Yeah, we are.’”
The ODOT officials’ response was that they wanted all Stage I work completed by July 4 before commencing on Stage II work.
Stage I was to construct crossovers at the ends of the projects and the three interchanges that cross the 100 foot wide earthen median. This placed traffic traveling both directions temporarily on the eastbound side. At the incline at the south end of the project, an additional temporary passing lane was also constructed.