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Imagine you are charged with this task: Accurately survey the interior of a limestone mine cut into the base of a bluffa cave with vast expanses, irregular surfaces and no light. Collect data on enough individual points to create a meaningful model of the space so that it can be designed and built for warehousing and storage. The challenge would be almost impossible using conventional surveying methods.
The team at Thouvenot, Wade & Moerchen, Inc. (TWM), a St. Louis area engineering and land surveying firm, was not fazed. The company used innovative 3D laser scanning to meet the challenge, garnering the firm a 2011 Honor Award and the top prize in Surveying & Mapping Technology from the Illinois Chapter of the American Council of Engineering Companies, along with a 2011 National Recognition Award from the ACEC parent organization.
A course of events nearly two decades earlier, in the summer of 1993, explains why TWM was tasked with mapping the interior of an abandoned limestone mine. That summer, torrential rains brought the Mississippi River well above flood stage. On August 1, the levee protecting the rural town of Valmeyer, Illinois, just 25 miles south of St. Louis, Missouri, could no longer contain the swollen river. A catastrophic flood swept through tiny Valmeyer, thrusting the town of 900 onto the map and into the national spotlight. With 90 percent of the homes, schools and businesses destroyed by up to 16 feet of river water and mud, Valmeyer officials and residents boldly decided to move out of the floodplain and build an entirely new town atop the adjacent river bluff, 400 feet above its water-logged past.
As part of the land acquisition for its relocation, the village was required to also purchase a 6,000,000 square foot abandoned limestone mine, carved into the face of the Mississippi River bluffs beneath the new community. While the space was considered an unusable white elephant by some, local developer Joe Koppeis of Admiral Parkway, Inc. has turned the old mine into a new source of jobs and revenue for the village. TWM had engineered Valmeyer’s relocation after the historic flood, and now, led by project manager Craig Brauer, the company helped Koppeis engineer the conversion of the mine into the Rock City Business Complex.
The naturally cool, dark environment of the mine is ideal for historic document preservation, and by October 2008, the National Archives and Records Administration (NARA) had developed and opened a 398,862 square foot National Personnel Records Center (NPRC) within the complex. When the Archives needed additional space, TWM suggested using 3D scanning to illustrate how they could expand at Rock City. Comparing one warehouse to another is fairly simple. However, comparing an underground space of these proportions with very few straight lines—and with 1,500 square foot columns of rock in the way—is a real challenge. TWM’s team felt that 3D laser scanning technology was the right tool for the job.
Using a Trimble GX 3D Scanner from Seiler Instrument of St. Louis resulted in higher accuracy, quicker surveying, and lower cost to the client than traditional surveying methods would ever allow. In just five days of field work at Rock City and 52 instrument set-ups, Andy Joost, TWM’s technician, used the scanner to locate nearly 80 million points in an approximately 700,000 square foot (16acre) area of the mine. Using a laptop with Pointscape in the field, he captured enough data to model 68 pillars and two long walls, all in a space where the elevation difference between the floor and ceiling ranged from 10 to 45 feet. Back at the office, he created a digital model of the space in Trimble RealWorks.
"Ease of use in the field is one of the benefits of the technology," Joost said. The set-up of the instrument and workflow of the field software is similar to what a surveyor would expect when using a traditional total station: the technician sets the instrument on a known point and then back sights. Once the equipment is set up, the actual scanning process is fairly self-sufficient. "Surveying in the dark was maybe the biggest adjustment I had to make," Joost said. But since the points ranged from 200 to 300 feet away, and the scanner did the work of locating those points, Joost did not need all areas of the mine to be well lit. Task lighting was sufficient. While the scanner was collecting data, Joost set additional control stations in the stone floor and traversed them with a Trimble S6.
One of the biggest differences between 3D scanning and traditional surveying is how points are selected. While a surveyor traditionally uses judgment in the field to select and survey only what is most relevant, the 3D scanner collects millions of points. So the job of choosing which points to use in modeling happens in the office after the data is downloaded. "The office work is extremely different from your typical topographic survey," TWM’s survey manager J.R. Landeck, PLS, EI, said. Since not all office staffs will have experience with RealWorks software, firms should expect some learning time. For this project, data processing took approximately three days. In other applications, however, data processing could be three or four times the hours spent on fieldwork.
While Trimble specifies a computer with at least 2 GB of RAM and a 256 MB 3D Open GL graphics board, based on past experience and the amount of data collected, TWM currently uses a 64-bit system with 8 GB of RAM, an Intel I7 processor, and a 512 MB Nvidia Quadro FX 580 graphics board to help expedite the process.
TWM’s approach involved creating a grid of the floor, ceiling and pillars of the former mine. Technicians assigned a "weeding factor" inside the software so that only a certain percentage of the collected points would be visible. The software can also correct for objects like boulders on the floor of the mine that will eventually be moved and may create false data. From that grid, the software created a mesh, which became a virtual 3D object on the screen. "Features then appeared as if we had thrown a cloth over the rock surfaces to show their outlines," Landeck explained.
To further facilitate the design of the mine’s new interior infrastructure, the scanner data is exportable to traditional CAD software applications. However, AutoCAD does not recognize vertical inverted cones, and the program therefore cannot process all the data collected by the scanner and downloaded to the software. So instead, TWM’s team exported to AutoCAD only the cross sections where the walls would be placed. These profiles could then be sent to the wall manufacturer to be built in factory and delivered to Rock City ready to install.
Using the computer based model, a design team led by TWM engineer Craig Brauer and architect Mike Schneider of Quadrant Design, Inc. considered the relative locations of the stone pillars and walls of the mine to determine the best placement of the man-made walls. The National Archives hoped to achieve the highest possible density for storage, so Brauer and Schneider created a grid layout of the shelving units. They could then slide that grid in multiple directions while verifying that the walls would fit along one of the grid lines.
The engineers also considered the floor and ceiling elevations to ensure that the finished space would maintain at least 22.5 feet of headroom—enough to accommodate the 20-foot high shelving and the sprinkler system above it. To further complicate the design, the unfinished area of the mine included an eleven foot change in existing floor elevation, presen
ting additional challenges to shelving layout due to restrictions on maximum floor slope. The floor obviously needed to be flat for shelving to be installed, so parts of the irregular surface had to be milled. By configuring the space to minimize required milling, the team helped control project costs. Without the highly accurate 3D survey of the floor, columns and ceiling, these design decisions would have been much more difficult or even impossible. But because of the detailed data, the team could maximize usable space.
Other consultants and contractors also benefited from TWM’s survey. "The 3D scanning data TWM provided was invaluable to our firm when designing the sprinkler system," said Larry Howell, President of L & K Fire Protection, Inc. The HVAC consultant used TWM’s survey data to lay out piping runs. As a result, all systems and fire exit routes were easily designed in compliance with appropriate codes.
Ultimately, TWM’s 3D scanning helped meet Rock City’s needs, budget and schedule and assisted in the configuration of the space so that it could hold 33% more storage per square foot of floor area than the previous Archives space. "Having this highly detailed survey prior to construction allowed us to meet what we thought would be an impossible timeline, and we did so with minimal construction change orders," owner Joe Koppeis said. "Not only did TWM’s use of scanning technology allow us to develop Annex II, but it also allowed us to scan an area big enough to build three times the space we actually needed for this addition. So we already have a large amount of data for future build-outs."
Developing a former mine into storage space is not something most surveyors will face. But the benefits of 3D scanning could prove useful with other innovative applications of the technology. For example, when the city of Belleville, Illinois, needed to run a new sanitary sewer interceptor from its downtown area to its wastewater treatment plant, the conventional approach would have been to dig up the streets for that entire distance, disrupting traffic, residents and businesses. Instead, TWM looked to an existing storm water tunnel running along the same alignment. Using 3D scanning, the firm modeled the inside of the tunnel. Engineers then used that data to design the new sanitary interceptor horizontally and vertically within the tunnel, avoiding costly and disruptive street excavation.
TWM used 3D scanning to model the dense network of pipes and valves in an existing wastewater treatment facility and to three-dimensionally design the expansion of that system and the integration of the new and current infrastructure. The company has also used 3D scanning to survey a busy intersection from the right-of-way without affecting traffic flow or compromising safety. The scanning equipment can help TWM easily survey complex refineries and manufacturing facilities, determine the volume of a gravel pile or detention basin, or even collect data from a neighboring property without having to enter it. With 3D scanning, a technician can gather large amounts of data without working directly in a roadway, crossing difficult terrain, or accessing other dangerous areas.
While the innovative technology is expensive to purchase, surveying firms also have the option to rent the equipment. The efficiency of 3D scanning and its ease of use in the field clearly make it a safe and effective alternative when traditional surveying methods are not the most practical approach.
Jennifer Wolkiewicz is a graduate of the University of Notre Dame where she minored in Journalism while pursuing a Business Administration Management-Consulting degree. Her subsequent work experience has been within the professional services industry, which includes managing both Marketing and Human Resources departments.
Dianna Graveman has a Master of Fine Arts in Writing from Lindenwood University where she is also an adjunct professor. She is a freelance writer/journalist in St. Louis, Missouri.
A 2.268Mb PDF of this article as it appeared in the magazine—complete with images—is available by clicking HERE