Jersey airport taxiway designers finish on time and within budget with Autodesk Land Desktop.
A Desirable State to Be In
Jersey Airport (located in the state of Jersey) on the busiest day of 1999. Five hundred aircraft movements, an average of one every minute; aircraft ranging in size from small Cessna private aircraft to giant Boeing 767s. In 1999, there were 80,000 movements and 1.7 million passengers. Not bad for an island with an area of only 50 square miles and a population of 85,000. Jersey is not part of the United Kingdom; it is a self-governing state with an allegiance to the Queen and takes great pride in handling its own affairs. The state of Jersey, well known as a desirable holiday spot, is located on an island in the English Channel about 15 miles from the French coast and 90 miles south of England. Holiday-makers from Britain find its character strangely akin yet quite different from the mainland. However, business is overtaking pleasure as the mainstay of the island economy and business needs fast and efficient communications. There are maritime links with England and France for those able to take more time on their trips but the airport is now the main physical communications link with the rest of the world. This is a real airport, an international airport and an airport with a vision. The Jersey Airport 2020 Master Plan, requiring a budget of over (£100 million), is changing the vision into reality through modernizing facilities to meet higher standards demanded by the traveler. An early part of this plan, the Alpha Taxiway, is now coming to fruition thanks to the excellent work carried out within the Jersey Government by the Highways, Traffic and Civil Section of Jersey’s Public Services Department using Autodesk Land Desktop (Autodesk, San Rafael, Calif.).
The Challenges of Success
The growth of traffic at Jersey brought with it a number of problems. While the runway was able to cope with the load imposed by the high level of movements, surveys showed that the existing taxiway was reaching the end of its life. Repairs would be expensive and disruptive and operational failure would always be a possibility, with drastic consequences for business and tourism. If action were not taken, restrictions would have to be placed on taxiway use. Indeed some larger aircraft already had to use the runway as a taxiway to protect the fatigued pavement, with an inevitable reduction in capacity and increase in user dissatisfaction. The only answer was to face the challenges of designing and constructing a new taxiway. For construction, it would be necessary to move existing facilities such as the Jersey Aero Club. The approach road running alongside the airport would also have to be realigned. High capacity drainage would be needed for fast removal of taxiway surface water. The work would have to be carried out with minimal disruption to aircraft operations and since the airport is self-funded, the project must not place a load on the taxpayers of the island.
Ground Modeling in 3D Proves Productive
The States of Jersey Public Services Department (PSD) handled the project from the outset. Quintin Murfin is the principal engineer and Simon Stanley is a design engineer responsible for the alignment and earthworks modelling. Quintin recalls the main issues. “It was,” he said, “a critical project. Dates were fixed and we had to hit them otherwise the financial and operational consequences could have been measured in millions.” The department already made extensive use of CAD. However, if the Alpha Taxiway airfield design was to be completed on time and to the required quality, a fast and easy-to-use design solution was needed. From previous experience, Simon knew that the creation of a 3D ground and taxiway model would provide them with the best chance of designing to the deadline. Using such a model, it should be possible to test concepts, create and check designs and to monitor the effects of changes before committing the design to paper and to contract. Changes at the model stage should be far less expensive than changes at the construction phase. Non-engineering staff would easily understand this model compared to the years of experience it normally took to visualize the finished article from 2D drawings. After detailed investigation, the choice was made to use Autodesk Land Desktop.
Decision Pays Off
According to Stanley, “We needed a very high level of confidence that whatever system we chose would work.” In his view, Land Desktop had the better ground modelling tools and was better able to share information across the design team. “We bought a solution that worked,” he said. “We bought the market-leader we felt we could trust.” But were they right to do so? With over 12 months of mission-critical use to look back on, the answer has to be yes. The decision to purchase three copies of Land Desktop was made in December 1999 and by the end of January the design team had undertaken four days of intensive training. The new taxiway design was completed on time in September 2000. The tender was issued on time in October 2000 and work commenced on time in January 2001. Missing any of these crucial dates would have introduced many months delay through slippage of various approval deadlines. Extra costs would then have been incurred had contractors been required to meet the original completion date. By using Land Desktop, the team has already saved six weeks on the project, now in its construction phase, compared to original programs. There was an estimated 20 percent time savings in the detailed design phase. There was noticeable time savings in achieving the earthworks balance and a substantial cost savings in taxiway base material costs. According to Simon, “We stole a march on the original time estimates. Moving from the survey to the model was quick. Assessment and editing was quick, too.”
Innovation Saves the Day...
That the project was such a success is a testament to the creativity of the project team, including engineers David Simons and Janette Muscroft, and the help they got from using Land Desktop. The taxiway alignments and drainage had to meet CAA regulations. To meet Jerseys’ strict environmental rules, excavated material could not be exported from the island, nor could material to form the taxiway base be imported. In addition, potentially polluted water run-off from the taxiway had to be purified before disposal. The PSD team took a genuinely innovative approach to resolve these conflicts. They decided to use an environmentally attractive and low-cost technique for the treatment of wastewater known as “Constructed Wetlands.” Taxiway rainwater water would be drained to a balancing pond for preliminary treatment by mechanical aeration before passing into a constructed wetland, a planted reed-bed. Here, microbial utilization and plant uptake of nutrients would further purify the wastewater. In this way, the seepage of airport-related toxins such as fuel and glycol from de-icing operations, into the water table, would be prevented. Material excavated from the balancing pond and constructed wetland would be used to create the taxiway base. Thus, a neutral earthworks balance would be obtained and the benefits in terms of noise, pollution and energy use would be considerable. Because material only had to be moved a few hundred meters across the approach road, the cost of disposal, acquisition and transportation would be reduced.
...And Land Desktop Saves the Weeks
The design could only be effectively created and evaluated using 3D ground modelling techniques. The volume of material required for the taxiway base had to be determined by superimposing the taxiway on the ground model of the taxiway base. The balancing pond volume had to meet the drainage requirements. The consultant ecologist had determined that the surface area of the reed-bed should be 13,000 square feet (approx. 1,200 m2). And its base level had to be lower than the base level of the drainage pond. Any changes in the drainage design would have to respect these requirements. Creating the basis design in Land Desktop was straightforward. A rectangle was placed below the surface indicating the maximum elevation of the drainage pond base. Projecting up at a given grade from this new ground level until it intersected with the surface created the drainage volume. The grade angle was determined by the geotechnical consultants from the soil mechanics of the material. Carrying out this work using Land Desktop, it proved possible to evaluate the full range of compliant design options in hours, when previously it would have taken weeks.
A Glitch-Free Process
Teamwork has been important to this project and Land Desktop has been a key enabler. When a project is set up in Land Desktop, all the data is kept in a single multi-access database. This means that the whole of the design team can access the data without waiting for other users to log off. Quintin Murfin estimates that this ability to share information accounted for two weeks out of the total savings of eight weeks on the project. Land Desktop is now reaching the end of what is in effect the live assessment period. It is proving itself in action, on a real project. Making a before and after comparison, Murfin notes, “The chance of manual errors is much lower now. Authorizing drawings for issue is much faster now. Without Land Desktop the process would be much more complex. I don’t recall any numerical glitches at all.”
Success is Assured
The state of Jersey has invested heavily in the Autodesk Land Desktop solution and the team that made it work so well. A return on that investment is already being delivered and the taxiway is well on the way to completion. The next major project will be the North Apron. This presents an entirely different set of problems to the Alpha Taxiway. Scheduled for completion in 2004, the North Apron has to be tied in with a number of existing constraints, including terminal buildings and aprons. Land Desktop will be used to design to new falls to meet CAA requirements and to model each layer of the apron to establish accurate volumes and cut and fill. From the evidence so far, success is assured.
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In the April 2017 issue of POB, find out how 3D tools played a role in the renovation of the Institute of Civil Engineers headquarters in London. Also, POB releases the results of its 2017 3D Surveying Trends Study.