Chicago’s Dynasty Group Manages Huge Logistical Challenges to Deliver Survey Data on Schedule
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The Chicago Transit Authority’s (CTA) Red Line is Chicago’s busiest rail line with an average weekday ridership exceeding 250,000. It’s a vital artery of the city, and runs 24 hours a day, 365 days a year. This creates a classic urban commuting conundrum; the Red Line needs continuous renovation and maintenance to keep the city alive… but ideally, should never actually be closed down.
The CTA is currently working on a massive rehabilitation of the Red Line’s Dan Ryan Branch, a 10.5-mile section that runs along the Dan Ryan Expressway. The project got started with the most sophisticated corridor survey in the Authority’s history, a massive logistical effort that ultimately included traditional, GNSS, laser, and ground penetrating radar (GPR) surveys of the entire route, geo-referenced video, and web-based delivery of all field survey data. In addition to the survey and ground-penetrating radar (GPR) work, Dynasty also coordinated the efforts of other subcontractors, including geotechnical, environmental boring operations, and bridge inspections. Managing dozens of crews, all working on two rail lines squeezed into a corridor about 30-feet wide, was tricky according to Dynasty Senior Engineer (and deputy project manager) Jesse Bruning, "Some weeks we requested more than 80 CTA flaggers," he says, "And pushed them to their limits." In fact, everyone was pushing hard–to support the 30% engineering design schedule, most survey work had to be completed in a two-month window.
A Very Thorough Survey
The CTA’s scope of services called for topographic surveying, ballast evaluation by GPR, photo and/or video documentation (including sewer video), buried drainage structure location, and underground utility location. Fieldwork began with static GNSS to set permanent control every mile. Conventional total stations were then used to set intervisible controls at approximately 1,000 feet intervals, as far away from train vibration as possible, with tighter control near train platforms. Digital levels were used to set benchmarks every 600 feet.
This was the CTA’s first official request for scanned data, and it was quite a beginning; the scanner was set up a total of 440 times collecting, on average, 6 million points per setup. "Logistics in the office were intense," says Bruning, "Just keeping point numbers straight was a fight; we had to assign blocks of points to each crew, and we had very strict block and file name conventions."
This wasn’t actually Dynasty Group’s biggest scanning job–they’ve been scanning since 2001–and they have their work flow fine tuned to accurately manage data collection and registration. On the other hand, it was the CTA’s biggest and first scanning job, and the firm took extra measures to reassure their client. "In the beginning, the CTA was looking for different methods," says Dynasty Vice-President Stuart Schultz, "but based on the project requirements, and the short time frames we were working in, we really felt that laser scanning was necessary. So we had to sell that to them." Part of the `sales process’ was substantial data redundancy. Using a Leica C10, scans were taken every 200 feet and the C10’s survey workflow was used to tie each scan to the control network. Scans were registered in groups of four or five, and each group was tied to two or more of the permanent, high accuracy, control points. The project was also redundant in terms of technology used; "We used all the technology we have available," explains Bruning, "Static and RTK GNSS, digital levels, and total stations were used for control and to spot check scanning data, and we also ran multiple cross sections with conventional methods to compare to cross sections extracted from the point cloud. Everything checked in beautifully; we couldn’t have been happier with the scanning accuracy."
"Nothing but laser scanning would have worked," Dynasty Group President Zhong Chen confirms, "Not with the brutal schedule and the amount of data that had to be collected. With scanning, even if we `missed something,’ chances are we can just go back to the point cloud and survey it virtually. That saves us so many field trips."
Working Near Trains
"There were some headaches," Bruning admits, "We only had 20-30 feet between barriers, and with two active lines, it was tight. And very few closures were allowed."
Though outright closures were limited, Dynasty Group crews were allowed on CTA right-of-way with live trains. All crews had to attend CTA safety training, were assigned two to four flaggers per crew while working, and trains slowed to five miles per hour when near crews.
"The most unique thing about this project was setting up near the rails," says Bruning, "We learned right away that we didn’t have as much time for setups as we’d expected." In fact, crews learned to get the scanners setup and gather data in as little as eight minutes. "That ruled out use of the photo feature on the Leica C10, and higher density settings," Bruning points out, "But with close setups and medium density, it worked out well." Close setups, about 200 feet apart (and even closer near platforms) and on alternating sides of the track, provided more than sufficient overlap for accurate registration.
"It wasn’t all that intimidating," says Schultz, "The flagmen would let us know when trains were coming, and we planned things out well. It was a tough routine, and we were on foot for all of it (the CTA prohibited the use of trains for transport), but day by day we got it all done." In fact, Dynasty Group delivered all data on time with no accidents and no unplanned service interruptions.
Meanwhile, GPR crews were also keeping busy; "There were multiple power and signal cables buried in the ballast, often times incased in concrete ducts." says Aldo De La Haza, a Dynasty Group principal and head of non-destructive testing (NDT), "And cutting just one would have shut down 40% of CTA’s ridership." And unfortunately, as-built drawings of the utilities do not exist.
GPR can identify subsurface features quite accurately when calibrated; in this case, De La Haza was able to take readings near drainage manholes and calibrate by periodically opening manhole lids and measuring features. This helped him to estimate depth of utility lines to within about six inches. Using GPR, his crews were able to `clear’ about 200 locations for soil borings.
GPR was also used to analyze the ballast itself. "Because this rail system has been in place for so many years, ballast starts to crush and disintegrate," De La Haza explains, "The resulting fines sift down through the aggregate. This can cause trouble by making the ballast less stable." So GPR crews walked the entire 10.5-mile route, towing a GPR antenna mounted on a calibrated wheel with a built-in distance encoder to keep track of stationing, and checking in at control points. The resulting GPR profiles are used to determine soil and ballast layers and guide rehabilitation efforts.
World Class Data Delivery
The web-based data delivery system is an initiative of Chen, who says, "I couldn’t wait for the day when architects and engineers would have desktop access to point clouds. Now we’re finally able to make that happen."
past couple of decades," he continues, "Surveyors have been delivering data with CDs, DVDs, email, FTP, etc. And that’s faster, but it’s not really different. Web-based delivery has the capacity to be really different."
The system that Dynasty Group used for the CTA project is an access-controlled website that aggregates all data collected for the rail survey, overlaid on relevant, publicly accessible layers like aerial photography and CORS stations. "Making the website interesting and easy to use is what I find challenging," says developer Lei Han (who developed the web site along with Qi Zhao) says, "Zhong wanted a simple interface that replaced paper for most users; I think we achieved that."
Han works with project managers to determine what website elements are needed for a particular project; he then creates forms and protocols that work for that project. In this case, several sophisticated features were included for the CTA, designers, and lead contractors.
• Leica’s TruView was used to create accessible point clouds that can be used by designers for measurements, and by management to make decisions regarding the impact of improvements. "Giving clients desktop access to the actual point clouds is important," says Chen, "It really helps them to see the value of scanning data."
• Geo-referenced, high-definition videos of the corridor, taken from the front and back of north- and south-bound trains, were included, along with a sophisticated graphic interface. Basically, as the video shows in one window, an icon moves along the route in another window, showing the video location. Thus, the route window can be used to snap to video locations, and vice-versa. "We had to figure out how to do this," says Han, "This time, surveyors kept a table as they filmed, with time and latitude and longitude, which we used to index the video to the route. We’re working on making it more automatic."
• Topographic, GPR/NDT, environmental, drainage, geotechnical, and other data are all readily available and easily located by the spatial interface, along with task data and org charts.
• All the data you would expect to find in Google Map, or a good municipal GIS is also available, making the project website the first place to look for project data of any kind.
Really, the website resembles a projectscale GIS, optimized for spatial data. It’s impressive… but do clients really use it? Chen says yes, emphatically; "Everything we agreed to do is on the page, which minimizes the loss of data from surveyor to designer and, later, from designer to contractor. And this gives management a good way to look at field conditions, so they can make better decisions. I know for a fact that the video was used to make choices during the 30% design."
Of course, the website is also important internally; Dynasty Group crews rarely return to the office. Instead, they upload and download data via the website, using laptops or even smartphones. Given Chicago’s traffic congestion issues, this saves many hours each week.
Typical American Dream
"Dynasty Group is just my second job out of college," says Chen, laughing, "Typical American dream, right?"
Well, not exactly typical. Chen is actually a first generation Chinese-American, the son of two engineers; his mother, at 75, is still active as a government consultant and his father, at 79, is now a professor after a career with Beijing’s largest municipal engineering firm. With a pedigree like that, it’s no surprise that he came to Chicago, on a full scholarship, to study engineering at the Illinois Institute of Technology.
But it’s at least a little surprising that less than ten years later he was starting his own firm, in a city that can be hard on newcomers. Dynasty Group has thrived in a tough market, and now employs more than 50 people with offices in Chicago and China–in fact the firm was the first to provide laser scanning for China’s Mogao Grottoes, home of some the world’s oldest and most important Buddhist art.
"We focus on very basic services that can be applied in a lot of areas," says Chen, "That lets us take on different types of work, including lots of high profile Chicago area infrastructure projects." Currently, Dynasty Group works in five sectors: Design Engineering, Construction Engineering, Surveying (40-50% of revenue), Non-Destructive Testing, and GIS and BIM Support.
So it’s not a typical American dream, but it’s certainly a resounding success story. It’s good to know that engineering talent, and a gift for getting the most out of people is still a prescription for success in America, and Chicago is lucky to have a progressive firm attending to its vital infrastructure.
Angus W. Stocking, P.S. is a land surveyor and full time writer on infrastructure. He can be reached at www.InfrastructureWriting.com.