An 11,000-ton asphalt paving project normally would not command much attention. However, paving the lanes of the Eisenhower-Johnson Memorial Tunnel, near Denver, isn't your typical paving application. At more than 11,000 ft above sea level, paving the two, 1.7-mi-long lanes of the westbound and eastbound bores - the highest vehicular tunnels in the world - proved to be challenging.
With steep 7% grade approaches and an average annual snowfall of 312 in., the conditions are not ideal for a pavement. "When the snow flies in Colorado the tire chains are put on," said Alan Adams, president of Pavetec Inc., Silverthorne, Colo., the paving contractor. "Abrasion from the chains really affects the service life of the road."
The last complete overlay of the tunnel's surface was in 1997, less than 10 years ago. "We design the surface for a 10-year life, but in this environment - heavy truck traffic, the weather, salt and chains - we are satisfied with a 7- or 8-year life," explained Ina Zisman, resident engineer for CDOT.
To maximize the pavement's service life, CDOT has specified a stone matrix asphalt (SMA) PG 64-28 mix design with a 3/4-in. top aggregate size for the project. This polymerized coarse mix design with high oil content is expected to withstand the abuse of nearly 47,000 vehicles per day. However, paving with the mix proved to be challenging. "You cannot handwork this mix. It has to be put down right the first time," said Adams.
There were few methods for paving the overlay. "This is a very tender mix, so we could not windrow the material," said Zisman. With the state's 0.1-in. blanking band and 16 in. per mile PI required for rural interstates, it is best to establish continuous paving to improve surface smoothness. However the tunnels' low 15-ft clearance (maximum truck height is set at 13 ft 6 in.) not just any material transfer vehicle (MTV) could be used for continuous paving.
Non-stop paving also would help meet one of the most critical challenges on this project--time. There was a strict timeline for lane closures with severe lane rental fees assessed if the work was not finished on time.
The entire project - asphalt and concrete removal, repairs and paving - had to be completed within a few days. The contractors worked on one tunnel at a time with traffic being diverted to the other tunnel, leaving a single lane of traffic in each direction. "We chose September because it has the lowest traffic counts at 25,000 VPD," said Zisman.
Work on the westbound bore had to be completed in less than a two-week period, and those lanes had to be reopened over the weekend. Less time was given for the eastbound bore with work required to be finished within 4 1/2 days. "The general contractor had some additional utility work in the westbound bore, so we had extra time," explained Adams. "We are going to be tight with the other tunnel."
If the deadline was not met, a $70,000 per day, per lane rental fee would be assessed, so all details had to be meticulously planned for the paving operation. The trucking, paving train and plant production had to work in concert to get the job done on time and with a high-quality finish.
Terex Roadbuilding supplied the high-production paving train, which included a Terex Cedarapids CR662RM RoadMix MTV and CR562 paver with Stretch 20 electric screed. The MTV was added to the paving train to establish non-stop paving. "We were able to use the RoadMix because of its low 9 ft 2 in. height," said Vince Egan, district manager for Terex Roadbuilding.
Pavetec paved the two 13-ft-wide tunnel lanes in two passes. Egan worked with the contractor to map and time the truck route to determine the number of trucks required. Sixteen live-bottom trucks were needed to establish continuous paving for the 17-mile trip from the asphalt plant to the jobsite. Due to the tunnel's low clearance, only live-bottom trucks could be used inside the tunnel.
Although Pavetec reserved 16 live-bottom trucks prior to starting the job, on the first day of paving the westbound bore there was an obvious problem. "Only nine live-bottom trucks showed up to deliver mix to the site," said Mitch Olson, project coordinator for Pavetec. Missing seven trucks led to long wait times between loads, poorly utilizing the production capabilities of the paving train.
Worse yet, this put meeting the 9 a.m. Sept. 22 deadline in jeopardy. Something
had to be done quickly to adapt to the trucking shortage and finish the job on time. The solution was to split the paving train to maximize machine utilization and improve paving production.
The CR662RM MTV was moved outside the tunnel and seven end-dump trucks were added to the truck count. "After a live-bottom truck delivered its load from the plant, we staged it by the MTV outside the tunnel," explained Olson. "We then used the RoadMix to transfer material from the end-dump to the live-bottom truck so it could go back and deliver material to the paver."
This creative solution helped to increase tonnage production of the paving train and to save the job. "This really shows the versatility of the RoadMix," said Egan. "Without splitting the paving train,
Pavetec's crews probably would have had to pave 24 hours a day to get the job done on time."
With the paving train's adaptation to the trucking deficiency, Pavetec's crew completed its portion of paving by Wednesday night, Sept. 20, beating the brunt of an early snow storm and allowing the general contractor, American Civil Contractors, to complete the finish work prior to the deadline. "Vince (Egan) and Terex Roadbuilding really bent over backwards to help get the job done," said Adams. "Although splitting the paving train didn't accomplish the original purpose of the demonstration, Vince told me, 'the main priority is getting the job done.' We really appreciate that attitude."
The team effort employed to complete the demanding tunnel paving project on time is paying off for Pavetec in more ways than one. The paving contractor has been nominated for a Colorado Asphalt Pavement Association (CAPA) SMA Award for its work on the Eisenhower-Johnson Memorial Tunnel. CAPA's 2006 "Best in Colorado" Asphalt Pavement awards will be announced on Wednesday evening, Feb. 28, in Denver.