Windy City Renewal

March 1, 2007
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American Consulting Engineer Jim Maurer uses a Trimble R8 GPS rover to shoot laneline profile for final x-sections.

 



As one of the nation’s busiest and most dangerous roadways, Chicago’s Dan Ryan Expressway is in need of a safer, less congested transportation artery. Today, the nine-mile thoroughfare is on the fast track to being completely reconstructed. Project goals include improving driver safety, traffic flow and road appearance.

The largest expressway reconstruction plan in Chicago history, the $975-million Illinois Department of Transportation (IDOT) project is also among the swiftest. With a three-year timeline from start to finish--20 months for actual road construction--the massive project is staying on target by using the latest surveying, 3D data modeling and machine control technology. The project is a model of efficiency, quality control and productivity that’s putting the Windy City on the map for state-of-the-art construction projects.



A Walsh dozer equipped with a Trimble 3D Grade Control system grades out the capping stone prior to bituminous subbase paving.

A Time For Change

Opened in 1962, the Dan Ryan Expressway is Chicago’s main transportation artery from downtown Chicago through the heart of the city’s south side and surrounding suburbs. Designed as an express-local system, the roadway has 14 lanes of traffic, seven in each direction. Four are express lanes and another three provide access to exits.

With nearly 320,000 vehicles daily on the Dan Ryan, traffic jams are common. The road has surpassed its original design life by more than 20 years; pavement in some areas has been falling apart; flooding has become a public safety threat; and between 1998 and 2000, more than 8,200 accidents with 27 fatalities occurred. It was time for major change.



Kapur & Associates survey crews use a Trimble 5600 Total Station to set offset nails for horizontal and vertical control. These points are used to control the concrete paving operation.

"˜Round the Clock Solutions

Using a consortium of designers, IDOT organized the project in five sections, each headed by an IDOT resident engineer working with various consulting groups. According to IDOT Engineer of Project Implementation Jacek Tyszkiewicz, PE, IDOT broke the huge project into 128 contracts to provide business opportunities to more small contractors.

By the end of 2007, the rebuilt road will include several new lanes, reconfigured ramps, a new interchange, and enhanced lighting and sewers, making the new Dan Ryan safer, wider, more durable and easily accessed.

The Dan Ryan’s importance to Chicago leaves no room for delays, says IDOT State Resident Engineer Jeffrey Washington. To minimize traffic impact, IDOT set a 20-month timeline for road construction work, from April 2006 to the end of 2007. IDOT worked closely with the city of Chicago to use city streets as alternate routes during construction. Additionally, IDOT made improvements to those alternate routes and reconstructed some of the frontage roads prior to closing down lanes on the Dan Ryan.

IDOT general contractor Walsh Construction has been instrumental in enabling the project to stay on track. Awarded a majority of the earthwork and construction portion of the project, Chicago’s Walsh Construction and excavation subcontractor Rohar Excavating keep on track by using GPS machine control equipment as well as real-time kinematic (RTK) GPS surveying systems and optical total stations. With grading, slope and actual position information inside the cab, Walsh and Rohar can run machine crews around the clock, greatly increasing productivity, minimizing errors and streamlining costs.

“The sheer pace of the work makes the Dan Ryan not your typical road reconstruction project,” says Jeff Erikson, Walsh Construction project engineer. “The amount of work and timeline requires us to work almost 24/7.”



Setting Up and Setting Out

The roadway’s five sections are connected through a precise control network set in 2004 by Burns & McDonnell Engineering Co. Inc. of Kansas City, Mo., and American Consulting Engineers of Lexington, Ky. The two firms’ Chicago locations are joint venture project management partners on the southbound express lanes section between 31st and 71st streets. Their network was the first task the consultants recommended to IDOT: “We felt it would be worthwhile to validate all design control under one umbrella,” says Burns & McDonnell Project Manager Michael Folta, PE.

American’s lead surveyor, Jim Maurer, PLS, worked with other section consultants to complete a GPS fast-static survey. The four two-person crews took 40-minute observations over three days using the Illinois State Plane East Zone NAD 83 datum for horizontal measurements and the city of Chicago datum for vertical measurements. It took an additional day to process the data and produce a site calibration. In addition, prior to performing the GPS static survey, the crews ran differential leveling through the project to achieve accurate vertical control. With 120 points over the entire nine-mile corridor, the network provides 3/8"-1/2" accuracy and connects all contractors and consultants through a common coordinate system.

“Rather than piece-mealing the jobs together, a common network enables everyone to use the same datum with their equipment,” says Luca DeBellis, CE, resident engineer for American. “It’s certainly made things a lot easier.”



Environmental Design International Inc. (EDI) surveyor uses a Trimble R8 GPS rover to provide cross section as-builts on the expressway project.

Network Connectivity

Maurer calibrated the network to local datum--but an unfortunate thing happened on the way to construction: two of Maurer’s GPS base stations were stolen. Rather than replace the units, he found it more economical to buy two RTK GPS rovers and use the RTK network operated by Precision Midwest (Trimble’s only authorized sales and service partner in Northern Illinois) for correction data. The network, which uses Trimble (Sunnyvale, Calif.) VRS (Virtual Reference Station) technology, covers 15,000 miles2 in the Chicago area to provide 24/7 RTK GPS data. Users get “out-of-the-truck” RTK surveying without setting up a separate base station.

“Using the vertical results from the differential leveling, I recalibrated the site on my own in just one day using the VRS,” Maurer says. “When I checked in on other horizontal and vertical control points throughout the project area not used in the calibration, I found the horizontal and vertical positions to be within three-eighths of an inch to a half-inch.”

After Maurer calibrated the site using the VRS system, other surveyors on the project started using GPS as well. “With the contractor’s fast pace, many surveyors felt they needed the VRS or GPS of some sort,” Maurer says. Currently, many of the consultants use the Precision Midwest RTK network; Walsh uses a separate GPS base station with repeaters for machine control.

“The VRS network has made it a lot easier to coordinate between projects,” Washington says. “Using the same datum system everyone knows precisely where they are--it seems to have made all five sections of the Dan Ryan project more connected.”

With a Trimble VRS system, users simply connect to the network with a rover for authentication and to report an approximate field position. The network technology then sends a correction tailored for the rover’s position. The correction is modeled using data captured at neighboring reference stations up to 31 miles away or more. With corrections received, the user can measure in real time with centimeter accuracy.

“The network has been invaluable,” Folta reports. “It’s reduced the time to maintain control and we can drop in control very accurately for new contractors when they come on to the project. From a coordination standpoint, it was dollars well spent.”

Rohar’s machine control is also connected to the larger project through the network. A GPS rover equipped with a VRS connection and a 900 MHz machine control radio was used to calibrate Walsh’s base. Several observations were taken at various times over the course of two days to get the lat/long datum.



A look at the new Dan Ryan near 51st Street.

Express Work on the Express Lanes

It’s 6 a.m. and the day shift has started. Walsh and Rohar have multiple earthwork crews, five dozers and a motorgrader using GPS grade control on the southbound express lane section. They also have numerous other crews and machines on each of the other four sections.

Earlier, Walsh’s Erikson downloaded updated road files from Associated Professionals Inc. (API, Elgin, Ill.) for the day’s work. API takes the designer’s paper files and creates a “template-based true road model,” says API’s Chris Frederking, EIT. “The model provides an infinite number of cross sections for the roadway--including all vertical curves, slopes and elevations needed by both the machine control equipment and GPS rovers on the job.”

The 3D road model can head off problems by looking at the “what ifs” that can occur prior to grading. Any point in the field can be instantly compared to the road files and grade established.

“The model allows you to check any point in space on the project,” Burns & McDonnell’s Folta explains. “That’s very important when you have a multi-staged construction project like the Dan Ryan. Numerous stages and contracts being constructed by different contractors require significant coordination at the stage and contract interfaces.

“Conventionally, we would only have plan data generated at even stations, but with the model you can confirm vertical and horizontal alignment off even stations and at random offsets,” he continues. “This technology provides a very accurate plan elevation for any point in the project corridor. That means as we move down the line we don’t have to do hand calculations for each point off the even station. This ability to confirm horizontal and vertical at any location was very valuable in complex geometric locations on the project. It really speeds up the overall construction process.”

Because the electronic data transfer is seamless, potential errors are reduced; using digital data connects the road model engineer, surveyor and contractor, enabling a more integrated and efficient workflow while minimizing downtime and reducing rework.

“We’re the link between the designer’s intention and how that’s interpreted in the machine,” API’s Frederking says. “We get a picture of what could go wrong and can get it fixed before they go out into the field. We’re the check on the designer and the surveyor is the check on us. He sees whether our work is working.”

The 3D road model was calibrated to the project through the VRS network. Walsh supplied the road model to American’s Maurer, who brought it in to 3/8" to 1/2" tolerance.

“Once the model is created and calibration [is] done, it’s a matter of allowing the equipment to cut and place it to the current line in the plans,” Maurer says. “With GPS, once you calibrate the road model and alignment you always know where you are and what your elevation is. It’s not nearly as labor intensive as in the past when we used level and tapes--or even total stations.”

API has been producing road models for years--and the Dan Ryan project has been one of the fastest, Frederking reports. Quantifying the pace shows the project’s speed. “Once the contract was initiated to Walsh, we averaged $1.5 to $2 million a week on our southbound express section alone, week in and week out,” Folta says. “We always hit those peaks in crunch times on other projects, but we had to hit that production level every week on the Dan Ryan.”

The fast pace of the Dan Ryan project supports not only the overall project timeline but seasonal requirements as well: they must finish the express lanes prior to Chicago’s heavy winter. To maintain quality, IDOT built in layers of inspection and checks--about 17 inspectors just for the southbound section, according to IDOT’s Washington.



Making the Grade

For the project, API built three different elevations for each road into the 3D model: subgrade bottom, top of rock and finish grade. The fourth layer--the capping aggregate--can be offset in the machine.

Walsh/Rohar had already ripped out the existing pavement and subbase, which they are reusing in the new roadway. After removing and replacing the drainage, they’re now pushing in the new subbase that will carry the 6-inch asphalt and 14-inch pavement; IDOT is using a leading-edge 30-year pavement design for the Dan Ryan.

“Almost every Walsh heavy highway job with any type of dirt work is using machine control and rovers,” Walsh’s Erikson says. “Most jobs I know of have at least one rover and machine with grade control. It accelerates production and minimizes errors.”

As machine control is increasingly used throughout the nation, contractors are benefiting from reduced manpower, seamless data collection and documentation, and improved accuracy and efficiency for construction projects.

“It takes the human error that could occur out of the calculations,” Burns & McDonnell’s Folta says. “The machine is being fed information from proven software packages. But you still have to make sure you keep qualified individuals from construction involved.”

To cut grade, Walsh and Rohar use both dozers and motorgraders equipped with Trimble 3D grade control systems. The 3D systems automatically compute the blade’s exact position many times per second using GPS to control the actual position, elevation and cross slope of the blade to the site design displayed on the in-cab computer screen. In-cab grade information enables in-field changes to be made quickly.

“With machine grade control we can put things on grade faster,” says Pat Goggin, operations manager for Walsh. “We can install the aggregates faster and keep working without having to cut hubs at each layer. We get accuracy to one tenth of a foot without needing as many hubs with grades--they’re already in the machine.”

At project end, Walsh estimates there will have been about a million cubic yards of dirt moved on the entire project.

After the dozers come through, the motorgrader fine grades the capstone, which requires “absolute precision,” Erikson says. Walsh paving crews then set up the string line for the paving machine, which uses hubs set by subcontractor Kapur & Associates Inc. (Milwaukee) to maintain grade.

Kapur surveyors also use the 3D road files to provide stakeout with a GPS rover--then switch to a robotic total station to lay out items requiring greater accuracy, such as mainline concrete pavement. Kapur has provided the initial layout including setting more than 300,000 linear feet of paving hubs, storm sewer setting hubs, layout, ramp work and other miscellaneous surveying.

Due to the “astronomically fast” timeline, Kapur uses four crews with Trimble R8 GPS rovers and Trimble 5603 DR total stations. “Walsh and Rohar grading crews work around the clock and are extremely difficult to keep up with,” says Dan Kucza, RLS, Kapur’s manager for construction layout. “The 3D road files produced in Terramodel give our crews a virtual plan set in their data controllers, allowing them to perform their work quickly and accurately in a very tough environment.”



A Fast-Track Focus

With roadwork on the express lanes on schedule, the focus for the remainder of the year will be the local lanes. Traffic will be diverted to the express lanes, with full restoration of the entire rebuilt Dan Ryan due by the end of 2007.

“I think the project has gone quite smoothly,” says IDOT’s Tyszkiewicz.

By using advanced surveying, 3D modeling and machine control equipment, IDOT contractors have been able to stay on time, on budget on a complex, fast-paced project--and all the while maintaining the highest level of accuracy, quality and production.

“The fast pace and high accuracy required on the Dan Ryan allow you to see how technology has advanced and helped connect the jobsite for greater efficiency,” American’s Maurer says. “It’s remarkable.”

To ready the Dan Ryan Expressway for reconstruction, the existing 15-inch-thick section of asphalt and concrete pavement must be removed, recycled and replaced. To read details about this site prep phase of the project, check out the article "Rebuilding the Dan Ryan" in the Jan/Feb issue of our sister publication, Site Prep, at www.siteprepmag.com.

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