Because the original road was constructed with continuous reinforced concrete, there were no transverse/expansion joint issues to deal with before placing the asphalt overlay.
According to Larson, there were some areas that had structurally failed and required a full-depth repair before placing the new asphalt overlay. A 2-inch scratch course (leveling course) of ODOT ½-inch (aggregate) dense mix was used to fill the rutted concrete surface, with pneumatic rollers employed to achieve density while working the mix into the rutted areas.
Larson says a 2-inch wearing course of the same ODOT ½-inch dense mix design was then placed over the entire roadway.
"We also milled out the inside (4-foot) shoulder and used the millings to fill in the concrete median barrier before capping it with concrete," he says.
Knife River's paving attack
For Jim Jackson, metro construction manager for Knife River's Western Oregon Division, the I-405 was the busiest place his company could have picked to tackle a paving project of this magnitude.
With the heavy traffic volume I-405 supports, ODOT's decision to execute the work during a directional lane closure approach was definitely the right decision for Jackson and Knife River, but it also meant that all eyes were on the contractors selected to see if they were up to the task. Hitting the specs and completing the work on time were paramount. While there was the potential for bonus to be earned, penalties of $500 for every quarter hour the interstate was closed beyond the required 5 a.m. Monday morning reopening also loomed.
Knife River proved it was up to the task. The paving contractor placed 24,000 tons of hot-mix asphalt across six total lanes (two main travel lanes and a third transition lane in each direction of the approximate 5-mile project) over the course of two weekend closures, as well as inlaying shoulders and nine on-off ramps.
While milling work on ramps was being performed at the beginning of the first weekend closure, two Knife River mainline paving crews worked on placing the leveling course designed to address the rutting problems.
On Saturday morning, three additional Knife River paving crews began working on the milled ramps and shoulder inlays. By Saturday night, the mainline paving crews began placing the wearing course.
Mainline paving continued through Sunday, with two separate paving crews finishing up ramp and shoulder work. At the end of the weekend closure, Knife River had completed its work on one direction of the project and the interstate was opened to traffic at 5 a.m. The entire process was repeated the next weekend on the opposite side of the median barrier.
According to Bill Wilson, Knife River's metro superintendent, end-dump trucks delivered mix to crews working on ramps, while belly dumps and windrow elevators were used on the mainline paving operation.
Knife River used over 45 trucks each weekend to haul mix the 18 miles from its Coffee Lake 500-tph Gencor production facility in Sherwood, OR.
Coordinating the supply of mix to the paving crew's production rate was critical.
Mix dumped in windrows had to be monitored constantly to maintain proper temperature and the length of the windrows had to be carefully controlled to prevent the temperature from dropping before the paving crew could process it.
Production and quality were definitely a delicate balancing act to maintain, but mainline paving crews managed to achieve a production rate of over 400 tph. And the paving contractor achieved the density and smoothness specs required while maintaining that rigorous production rate.
Knife River's equipment arsenal used to tackle the I-405 project included: Cat AP1055 paver, Cat AP655 paver, Volvo Blaw-Knox PF6110 track paver (used for pre-level scratch course and some off-ramp work), Cat CB-534D XW rollers, Cat CB-224E utility rollers, and Hypac pneumatic rollers.