Widening project alleviates heavy commuter congestion

For the past three years, Kansas Turnpike Authority engineering crews worked diligently with contractors to keep the I-70 widening project on schedule, while minimizing customer inconvenience. To do this, KTA used rolling road blocks instead of road closures to add a third travel lane in both directions of the 12.6-mile project between the East Topeka Toll Plaza 183 and the Lecompton Toll Plaza 197.

The added travel lanes were needed to alleviate commuter congestion in that corridor of I-70, which is experiencing rapid growth in customer traffic counts.

To accommodate the widening project, 1,140,134 cubic yards of excavation was required to expand the turnpike from two to three lanes. The existing two-lane interstate was built with a barrier wall median, a 10-foot inside shoulder, two 12-foot travel lanes and a 10-foot outside shoulder. The original roadway was constructed with a 1.5 percent cross slope that drained from the median to the outside shoulder. The existing roadway was built with a 10-inch aggregate base, capped with a four-inch asphalt base, followed by a four-inch asphalt drainage course providing drainage to the outside shoulder; and the drainage course was then topped with 10-inches of asphalt pavement placed in several layers as binder and surface courses.

This particular section of roadway was reconstructed in 2000, when the original concrete roadway was pulverized and a new HMA surface was placed. During the current expansion only the top surface course and a portion of the underlying binder course had to be milled off in order to accommodate a new slope and to match the surface of the additional travel lane.

Since the project involved adding another travel lane in each direction, changes were required to achieve proper drainage over the expansive paved surface. The slope of the inside travel lane and the inside shoulder was inverted to allow water to drain toward the median.

To minimize traffic disruptions during the project, excavation and paving of the additional lane was completed first in order to then move traffic to the new lane while the inside lane and shoulder were milled to change the drainage slope. This process allowed the existing two lanes to remain open to traffic while the expanded third lane was constructed. With the third lane constructed, the scheduling process was able to maintain two open lanes to traffic while the inside lane was shut down to correct the drainage slope.

This particular section of roadway carries a lot of commuter traffic, and to accommodate the heavier traffic counts during the morning and evening commute, there were time limits placed on lane closures. Hamm worked nights and weekends, during low traffic volume, to also minimize traffic disruptions. The KTA engineering crews also designed and built four sets of mainline bride and asphalt widening tapers to help maintain uninterrupted traffic flow throughout much of the project.

When the new outside lanes were completed, traffic was shifted to the two outside lanes. This allowed the contractor to remove the existing median, place 100 median drain boxes, construct a new 51-inch-high barrier wall, mill the new inverted cross slope, and place new pavement to maintain the required depth of a standard KTA pavement section. With the inside lane completed, traffic was then moved back to the inside lane to allow for final overlays to be placed on the center and outside lanes, and shoulder.

All existing cross road drainage on the project was replaced with new cross road pipes, along with all new median drainage pipes. The pipes were replaced by jacking pipe under the existing roadway so as not to disrupt traffic.

HMA work
Hamm Inc. of Perry, KS, served as the primary contractor on the project, placing 585,000 tons of Marshall hot mix design asphalt to construct the new lanes and overlay the existing lanes. A PG 64-28 binder was used in all of the base mix designs and a PG 70-28 binder in all surface mixes. A four-inch BM-2 base course was placed over the aggregated base of the newly constructed third travel lane, followed by a four-inch drainage course. With the drainage course in place, Hamm then placed several lifts (a total of 10 inches) of BM-2C base course, and then capped the entire roadway with two inches of BM-1KTA pavement surface course. Hamm subcontracted the milling portion of the project to Dustrol Inc. of Towanda, KS. Dustrol had to mill 329,619 square yards of existing pavement to invert the slope on the inside lane and shoulder, as well as prepare the existing outside lane to match up the overlay of the existing lanes with the new third travel lane and outside shoulder.

Tony Marienau, asphalt engineer for Hamm, says inverting the slope on the inside travel lane and inside shoulder proved to be the most challenging aspect of the project. With the addition of third lane, KTA engineers did not feel an inside to outside slope design would allow water to drain off the road surface fast enough. Consequently, the project was designed so water would drain off in both directions, allowing the surface to dry off quicker for safer travel.

"We basically had to remove the inside shoulder completely to accommodate the new slope design," Marienau says. "And on the banked curves we had to extend the transition going in and coming out of the curves. So, it required a lot of work to accomplish the correct milling depths required to lengthen the transition areas on the curved portions of the roadway. We also had to place some wedge sections to achieve the correct slope of new road."

The other challenge Hamm paving crews faced in executing the project involved meeting the tight smoothness specification KTA required. To maintain the mix quality and avoid material and heat segregation during placement, Hamm used a material transfer vehicle, which is required on KTA projects, to remix the HMA before sending it to the paver. Hamm used a Roadtec paver, a Roadtec Shuttle Buggy; Caterpillar, Ingersoll-Rand and Hamm rollers to place and compact the new road.

"The material transfer vehicle is critical in preventing material and heat segregation of the mix, but it's also critical in maintaining the pavement operation," Marienau says. "To achieve the smoothness requirements of the project, we had to keep the paver moving. Whenever you stop the paving process, or if you're loading directly from the truck to the hopper, there's always the potential of creating a bump in the mat surface."

Hamm received a $41,000 pavement smoothness bonus on the project, with KTA's smoothness requirements allowing for bonus incentives for surface deviations of less than eight inches per mile and penalties assessed at deviation over 12 inches per mile.

KTA at a glance
The Kansas Turnpike Authority broke ground on I-70 in 1954 and opened the turnpike 22 months later. The project cost $147 million, plus $9 million in Capitalized Interest. The original cost translated into $660,000 per mile. Over 20 engineering and construction firms were selected as successful bidders for the projects required for constructing the turnpike system. The turnpike consists of:

  • 236.5 miles
  • 21 interchanges for entry and exist
  • Six service areas located near Lawrence, Topeka, Emporia, Matfield Green, Towanda and Belle Plaine
  • 345 bridges
  • A concrete median barrier that runs the entire length of the road
  • Traffic growth from 3.6 million vehicles in 1957 to 33 million vehicles in 2006
  • 28.2 million passenger cars used the turnpike in 2006
  • 4.4 million commercial vehicles used the turnpike in 2006, but the commercial vehicles account for over 40 percent of the revenue the turnpike generates to operate and improve the system

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