To ensure flight safety, airports across the globe use large quantities of propylene glycol and ethylene glycol—better known as deicing fluid—to prevent ice forming on commercial aircraft during harsh winter weather. As with many airports, managing stormwater contaminated by aircraft deicing fluid has become a priority for T.F. Green International Airport (PVD). Needing to achieve compliance with Rhode Island Pollutant Discharge Elimination System permit conditions, the Rhode Island Airport Corporation (RIAC) solicited GS&P to design a new deicer and stormwater management system that would effectively collect and treat stormwater contaminated by aircraft deicing chemicals.
“The airport required a system that was capable of meeting strict pollution minimization requirements, and there were several challenges involved in designing a solution that met those conditions,” says senior environmental engineer and project designer Timothy Arendt. “For example, the design would require traversing 3 miles of stormwater piping across much of a 1,200-acre site that contained buried and surface structures. And that had to be achieved without excessive disruption to airport operations.”
As the project team considered the site’s complexity as well as the cost of construction—a significant concern to the client because of decreasing airport revenues—it soon became apparent that traditional approaches to creating a design for the new system would be far too restrictive.
“A typical process requires multiple steps of drafting, CAD [computer-aided design] entry, checking for errors, making corrections, and then repeating that process,” explains Arendt. “So there’s a lot of back and forth. Also, once construction starts, that traditional approach can result in frustrating, time-consuming and potentially expensive change orders. For instance, a section of piping may have been left out, or perhaps there’s an electrical line in the way and the CAD software didn’t tell us where the models clashed. For a project as complex as T.F. Green, with miles of piping that I referred to as ‘a spaghetti warehouse,’ that approach would be incredibly cumbersome.”
Looking beyond conventional methods, the GS&P team elected to take a new approach to the design, even though it would mean a steep learning curve for some of the team members, as well as a significant commitment of time and a dedication to working together in new ways. The potential benefits, however, for RIAC—and for other GS&P clients in the future—were far too great to do otherwise.
A More Streamlined Design Process
Taking a new direction, the project team adopted a design process using 3-D BIM (building information modeling) software for the implementation of the new system. Architects on the team were already familiar with BIM, but for others it would be a new experience. And even for those accustomed to BIM, the project marked the first time they would be using it in a multidisciplinary setting.
Employing the BIM software would require GS&P’s designers and engineers to interact directly with the CAD software to create the designs, removing CAD entry and back-check steps completely, and significantly streamlining the design process by eliminating the chance for errors in transferring the design into CAD.
“Back in the day, designers understood the significance when CAD software replaced pencils and paper, and 3-D BIM is just as huge an advance over two-dimensional CAD,” says Arendt. “It represents a sea of change in our industry, and it’s a new wave that’s becoming increasingly commonplace for many professionals and clients.
“Our team was truly excited about this change and was ready to learn something new. However, not only did we have to learn the new software systems, but we had to create an entirely new design flow that would ultimately cut out the back and forth between architects, engineers and CAD technicians.”
As a part of this new process, GS&P designers from many different disciplines learned new ways of working together as they became more dependent on one another than ever before.
“3-D BIM made it much easier to coordinate the review process among team members who were in different locations,” says Arendt. “In essence, it allowed us to ‘gather around the campfire’ and share information.”
A Coordinated, Multidisciplinary Effort
Utilizing the latest BIM technology, five different software tools would be applied to the project, integrating all major design disciplines. The design team would employ Revit BIM software for the architectural, building mechanical, plumbing and structural design; SSA and Civil 3D for the stormwater modeling and civil design; AutoCAD Plant 3D for the process mechanical design and process and instrumentation diagrams; and finally, Navisworks to visualize the integrated results from all of the models.
“Typically, a building is designed first and then the equipment is placed inside,” says Arendt. “With BIM, the team did that in reverse. The Plant 3D model of the process equipment was designed and then loaded into the Revit architecture model, and the building was designed around the plant. This form-follows-function design process ultimately helped us create a far more effective and user-friendly workspace for the plant operators at the airport’s stormwater treatment facility.”
In the past, because each drawing view was created separately, components such as pipe size and location would have to be painstakingly entered into CAD for each view. With this new process, changes in location or orientation of the pipes entered into the model were automatically updated in all views, reducing the time required for updates, and eliminating the possibility for errors from missed entry in one or more views. This was especially useful when multiple treatment plant sites were being considered at the beginning of the project.
Because the site for the airport’s new deicer treatment system was on the opposite side of the airfield from the airline and cargo ramps where stormwater is collected, routing of the stormwater conveyance piping (between the point of collection and the point of storage) was a major design undertaking that involved at least four potential options. And each option involved different yet significant constraints and risks that included wetland crossings, construction in public roadways, runway crossings, and routing force main piping through existing stormwater piping. Because of these elements, the project team had to determine the best pipe routes through buried stormwater piping, commun-ications conduits, live FAA wiring, natural gas lines and sanitary sewers in order to minimize costs as well as hydraulic impacts to the site.
“We used the inherent capabilities in the design tools—along with the plan for sequencing the design activities—to create a vision of the different force main routing concepts,” says Arendt. “This allowed us to understand the benefits and disadvantages of each option, and to respond quickly to new design concepts for the routes raised by our client. At an airport especially, there are all kinds of things buried in the ground, and BIM allowed us to quickly see any conflicts and identify alternative routes.”
At key intervals, the project team employed Navisworks clash-detection software to identify conflicts between the various discipline models. The program provided an integrated 3-D view of the models created by all other BIM programs, and enabled architects and engineers to jointly view all aspects of the design together in three dimensions. Any design clashes—such as pipes or valves located in the same space—were easily identified and moved. Change orders and their associated costs and delays were completely avoided.
“There were multiple benefits to utilizing BIM technology for this project,” says Arendt, “from streamlining the overall design process to facilitating clash detection to producing an extremely flexible design. Put simply, BIM is a modern-day version of ‘a picture is worth a thousand words.’”
The Advantages of 3-D
The ability to leverage the different software platforms and view them together in 3-D allowed the designers to see multiple systems in one view, and then analyze how those systems were interconnected. This facilitated discussion of possible design improvements as well as easy constructability reviews. The 3-D visualization also allowed engineers and architects to experience the design from the viewpoint of the plant operator, enabling the designers to better locate controls so they would be easy to access, read and manipulate.
“Being able to view everything in 3-D ended up being a very unifying experience,” says Arendt. “For instance, during construction, the project team took their iPads and laptops into the field to consult with work crews, and the workers really appreciated the clarity of those 3-D representations.
“We were also able to show the contractors the color-coded piping layout, and that’s a unique way to interact with contractors. That particular relationship can end up being adversarial if an unclear instruction on paper results in a change order during the construction process. It can delay the project and cause headaches for the contractor. But this process made that much less likely to occur, and helped the relationship become far more collaborative.”
A Sustainable End Result
Addressing deicing and stormwater best management practices, GS&P’s enhanced deicer and stormwater management system for PVD includes a terminal and cargo collection system, conveyance pump stations and force mains, above-ground storage, and an on-site anaerobic biological treatment system. The design encompasses an 11,000-square-foot treatment facility that can handle 7,700 pounds of chemical oxygen demand per day; above-ground storage of two 2.9-million gallon tanks; two pump stations that perform at 4,000 and 1,100 gallons per minute; and 14,900 feet of 24-inch and 12-inch force main for conveyance from the terminal and cargo aprons.
As the client desired a system that incorporated a number of sustainable elements, GS&P’s design also includes various eco-friendly features that will provide social, environmental and economic benefits to RIAC. These comprise: building conditioning optimization that reduces emissions released into the environment and decreases operating costs; chemical storage tanks sized so that only one to two refills from trucks are required per year, reducing transportation fuel usage and emissions; influent heat exchangers for energy optimization of the treatment process; and pipelines routed to avoid the wetlands.
Additionally, by using methane gas captured during the treatment process, the design team was able to make the new system’s fluidized bed reactor as energy efficient as possible.
“The methane provides free fuel to heat the chemical-laden water, eliminating the costs associated with building a larger facility and purchasing natural gas,” explains Arendt. “As a result, the treatment plant is smaller and less expensive to build and operate.
“Throughout the entire project, we were constantly aware of the need to keep the facility’s footprint as small as possible because space is at a premium in an airport environment. We were also aware of the client’s goal to control costs. So from an operating cost standpoint, you’re actually heating the water with free fuel.”
This innovative design feature also has an environmental benefit. When released into the atmosphere, methane is a powerful greenhouse gas. Burning it as fuel greatly reduces that effect.
“Capturing the methane when it’s released as the deicing chemicals break down is truly the key to the efficient operation of the facility,” notes Arendt.
Looking to the future, the team’s ‘BIM journey’—as Arendt refers to it—will continue, with the project team using BIM tools to facilitate system testing, development of operations and maintenance manuals, and assisting with startup and initial operation, including training the system’s operators and maintenance personnel. The BIM software will enhance that process, and allow for live facility walkthroughs that give operators a hands-on feel for the equipment. It will also enable airport managers to gain a realistic perspective on how the equipment appears, minimizing the need for expensive travel to other locations to observe similar systems.
In addition, a video developed from the BIM drawings will be used to demonstrate how the system works, as well as show the general public how the airport is managing pollution concerns associated with deicing chemicals.
“Because we took this new approach using BIM, we were able to design a cutting-edge deicer and stormwater management system—one that collects, stores and treats millions of gallons of water contaminated with aircraft deicing chemicals—and deliver it on time and on budget,” says Arendt. “And for GS&P, the use of BIM on this project keeps the firm at the forefront of the industry in the use of technology to advance the design process. And that in turn will provide our clients with greatly enhanced services.”