When the Oregon Department of Transportation decided to fast-track the Interstate 405 preservation project this past summer to complete a much-needed upgrade, the road agency was well aware of the pain it would cause the daily 83,000 to 125,000 motorists who use this vital 5-mile spur that runs from the Freemont Bridge to the Marquam Bridge, but ODOT also knew it was the best solution to minimizing traffic disruptions.
For almost 40 years the original concrete road structure had served the Portland area well, but severe rutting posed safety issues and there was no way to avoid the major undertaking required to support the heavy traffic load this major thoroughfare needs to accommodate.
The project involved filling the rutted surface with a hot-mix leveling course and then placing a final wearing course of asphalt over the entire travel lane sections of the road, along with inlaying the on- and off-ramps servicing the interstate to improve the overall safety and ride smoothness of the road structure.
Pavement grinding under four over-crossings of the freeway also had to be coordinated to maintain federal clearance requirements. New lighting and signs along the corridor were also included in the rehabilitation project.
As one of the busiest sections of freeway in the Portland metro area, serving freight and commuter traffic, the preservation project was a top priority for ODOT during the 2009 construction season.
The high traffic volumes during weekday daytime hours required that the travel lanes remain open. It was determined that any closures during that time would only result in significant backups on I-405, I-5 and local streets. Consequently, it was decided that four weekends of full directional (northbound and southbound) closures would accommodate the milling and asphalt overlay work required and eliminate months of nighttime construction that would normally be required for this type of project.
The milling and asphalt work was completed during three weekend single-directional (north or south) closures in August and one weekend single-directional closure in September, with additional nighttime lane closures required to complete some ramp paving, lighting and sign work. The weekend directional closures were limited from 10 p.m. Friday to 5 a.m. Monday.
Kerr Contractors Inc. of Woodburn, OR, served as the primary contractor on the $11.6 million project, with Knife River Corp. performing all of the paving work, placing 25,000 tons of asphalt.
The project also called for 150,000 feet of striping, 11,000 cubic yards of backfill, 15,000 square feet of concrete surfacing to cover the concrete median barrier, approximately 40 manholes and 90 storm water inlets raised to grade, 220 new light poles, as well as new lighting within tunnel structures, and two new sign bridges to be installed. Approximately 30% of the project cost was covered by stimulus funds through the American Recovery and Reinvestment Act.
Orchestrating the symphony
Ron Larson, ODOT Region 1 project manager overseeing the I-405, says while the directional closures did allow for an all-out construction effort during four 55-hour intensive work weekends, it required a well-orchestrated effort on the part of everyone involved.
"We had milling and paving going on at the same time, as well as other subcontractors (electrical, striping, etc.) working on their specific parts of the project," Larson explains. "While we didn't have to deal with motorists during the closures, we still had a lot of traffic and activity in the construction zone and safety was primary concern with all the moving parts of this project."
With severe rutting (1/2 to 3/4 in. deep) throughout the entire project, diamond grinding was required on some of the worst rutted areas as well as under four critical over-crossings.
"We would set up paving operations in an area that didn't require grinding in order to maximize progress during the closures," Larson explains.
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.
From flurry to finish
On Larson's end of the project, it was a flurry of activity with 21 ODOT Region 1 employees handling everything from complex traffic detours during the closures, to maintenance, to assisting motorists.
"We also had QA/QC on the project monitoring density and ride smoothness requirements," he notes.
With four paving crews from Knife River spread out over the construction zones, Larson says the truck traffic moving in and out project to keep the crews supplied with asphalt being hauled from the contractor's Coffee Lake plant south of Portland was another example of how organization and communication played such a crucial role in executing the work required during the closures.
"There were belly-dumps coming in to supply the mainline paving operations and regular dump trucks to supply ramp paving operations, and everyone needed to know where to go, and get there when they were needed in order to keep this project on schedule," Larson states. "In a conventional approach to paving this type of project during nighttime closures only, it would have taken months to do what we did in four weekends.
"We (ODOT) learned that you can shut down a direction of traffic to complete the work a lot quicker," Larson adds. "This was a very cost-effective way for ODOT, the contractors and the traveling public (taxpayers) to address a much-needed improvement to a road we all depend on."