Cutting across the northern third of the state, Interstate 40 in Arizona is 360 miles long. In northeast Arizona, Interstate 40 is under a heavy load, serving between 20,750 to 27,600 vehicles per day, according to the Arizona Department of Transportation (ADOT). A high percentage of that traffic is trucks and tractor-trailers.
Under this strain, Interstate 40 has reached the point of needing repair. "We had a serious problem because of bad weather in the winter of 2004," says Ed Wilson, senior resident engineer with the ADOT Holbrook District. "The Department of Public Safety had to close sections of the road because there were so many potholes."
These sections of road are located between McCarroll and Querino, and Querino and Hawthorne. In the fall of 2005, the Querino to Hawthorne project was in design but was accelerated because of the urgent need to fix the road. Spot milling and filling was done on the McCarroll to Querino section of the road that had potholes to allow time to obtain funding and design the corrective project. The Querino to Hawthorne project covered 11 miles of eastbound and westbound traffic.
A second previous mill-and-fill project was a 12-mile stretch between Pinta and McCarroll. Meadow Valley Contractors Inc. has now been contracted by ADOT to mill and fill an 11.7-mile section between McCarroll and Querino, bridging the previous projects together.
Wilson says sections of roadway renovations are scheduled based on need, not years in service. These three sections happened to be in need of repair and connected to each other. "State materials personnel come to the Holbrook district, where these projects are located, every year and go out with the district engineer and drive all of our routes," says Wilson. "They prioritize what roads need to be repaired. There's only so much money allocated every year to pavement preservation and then roads are monitored to see where they can get the best use of that money."
A familiar project
Harry Camptell, project manager with Meadow Valley Contractors, is familiar with the section of Interstate 40 now under reconstruction. "About 20 years ago, I was on the crew that rebuilt this section of road," says Camptell.
Asphalt technology has changed dramatically since then. Camptell says the approach to creating an asphalt mix was much different. "In those days, there was a lot of experimenting with using sand and rounded particulates. We looked for sand and gravel sources. Today, we look for rock sources. The quest now is to find particulates that are angular, and to use less rounded sand particulates," says Camptell. "We know that the round aggregates in the mix didn't make asphalt pavements as stable as they should be. The mixes today are highly stable because of the angular rock."
When the road was last rebuilt, Superpave had not yet been invented. On the current project, when the old asphalt is milled out, it is replaced with a Superpave mix. The current rehabilitation of the road contains two phases. The first phase includes the mill and replacement of the deteriorated asphalt, replacement of 14,000 feet of guardrail and some concrete work on three bridges in each direction. The second phase involves the placement of a rubber friction course on the new asphalt. The second phase will be completed in the summer of 2007.
The crew from Meadow Valley Contractors begins each work day at 2 a.m., with milling operations continuing until 11 a.m. At 8 a.m., the paving crew starts their 9- or 10-hour shift. Asphalt is produced at an asphalt plant on site.
Five inches in the passing lane and six inches in the travel lane are milled and replaced. "We are milling out into the right shoulder because one of the problems we have is the old rolled-in rumble strip on the right shoulder is coming apart," says Wilson. "The project is set up so two-and-a-half inches of that section is replaced, about four-and-a-half feet wide. We mill out the travel lane and shoulder and put a three-and-a-half inch lift into the travel lane. Then, we pave the second two-and-a-half inch lift in the travel lane along with the four-and-a-half foot wide shoulder in one pass."