Package deal

May 10, 2010

Fast-track construction is a common phrase. It means either speeding up the construction phase, and/or overlapping segments of planning, design and construction to achieve a shorter delivery time.

At the Memphis International Airport (MEM), we have been running fast-track projects for over 10 years, but even before that we were building runways and taxiways using the older and more conservative process.

Fast-track construction is a common phrase. It means either speeding up the construction phase, and/or overlapping segments of planning, design and construction to achieve a shorter delivery time.

At the Memphis International Airport (MEM), we have been running fast-track projects for over 10 years, but even before that we were building runways and taxiways using the older and more conservative process.

The pavement construction began in 1995 with new Runway 18L-36R and continues today. After dozens of individual projects, including four primary runways and a temporary runway, all costing $40-50 million each, numerous associated taxiways, a cargo building and apron, and a new base for the 164th Airlift Wing of Tennessee Air National Guard, 90% of the airside pavements at MEM are now less than 15 years old. All the work has been either new construction or full-depth demolition and reconstruction, including subgrade, subsurface drainage, lighting and signage with new concrete pavement above.

Booming Aerotropolis

Memphis is known as America’s Aerotropolis. An Aerotropolis is a city or an economic hub that extends out from a large airport into a surrounding area that consists mostly of distribution centers, office buildings, light manufacturing firms, convention centers and hotels all linked to the airport via roads, expressways and rail lines. MEM is a CAT D-V airport capable of handling the largest aircraft currently flying. It continues to maintain the position as the No. 1 cargo airport in the world thanks to the cargo handled by the airlines operating at MEM, especially FedEx Express. Nighttime and daytime operations are equally intense, and the airport does not experience the slow night operations of many airports.

Reconstruction of Runway 9-27, MEM’s only asphalt runway, was forced on the airport several years ahead of expectation by early deterioration of a 2004 asphalt mill-and-replace project. Officials had planned for seven to 10 years of life, but the new surface began deteriorating in less than three years.

Faced with early deterioration and the need to get this last primary runway into a low-maintenance-cost condition, the airport carried out a study in 2007 to determine whether another asphalt mill-and-replace operation or full demolition and reconstruction in concrete was the long-term solution. The study results, plus operational impact discussion with FedEx Express and with Delta (then Northwest) Airlines, indicated that full demolition and reconstruction in one construction season was the best near- and long-term solution. The decision to proceed was made in early 2008, and 2009 was set as the year of reconstruction.

Compressed competence

With that very constrained timeline, MEM had to develop another effective way to manage the project beyond merely fast-tracking the construction effort.

Compressed-schedule delivery means to maintain the traditional design-bid-build linear segmentation, but to deliberately compress each segment down to the bare-minimum necessary time. This is not easy, but it does leave project control squarely in the owner’s hands.

The most successful fast-track project MEM has undertaken was the reconstruction of Runway 18R-36L in only eight months in 2002. It set the standard for fast-track construction work and gave MEM a wealth of innovative ways of doing things. MEM took the practical lessons learned from it and other projects and modified them into a compressed-schedule format to take on the even more aggressive reconstruction of Runway 9-27.

There are three segments to developing and implementing a project. They are planning, design and project management. MEM has over the years steadily reduced the time allocated to these, but has maintained inviolate certain aspects as being vital to success. Compressed-schedule delivery required MEM to examine each segment and to determine which aspects were truly vital and which could be eliminated, on a single-project basis, without extreme risk.

MEM revised its planning segment by shortening it dramatically. In less than three months the project moved to full design. On previous projects MEM had studied in detail operational and construction constraints, developed an advertising campaign, conducted pavement workshops, established a significant contractor mobilization/procurement phase and used a definitive bonus structure. Of those elements MEM retained only the pavement workshop and the bonus structure. MEM decided to rely on its own experience and expertise to handle operational and construction constraints during the construction itself.

The airport eliminated advertising as too time consuming, even though it has proved valuable in developing common purpose among participants and in securing community support, and cut mobilization/procurement down to less than a month after researching material and resource availability. MEM conducted an early pavement workshop because the FAA mandated changes to concrete mix design procedures that needed explanation.

Large fast-track projects benefit dramatically from a definitive bonus structure. Using prior history, MEM established two key milestones within the project and made them date and time certain with no exceptions and no bonus at all if the dates were not met. The total available bonus was set at $2.5 million.

Familiar feel

MEM selected Kimley-Horn and Associates Inc., a design firm familiar with the airport, and mandated a mere six months for complete design. This was possible only because MEM and the designer had years of experience using established design methodologies, and no learning curve was expected. MEM eliminated only one segment from those established methodologies. That segment was a separate plan review by an independent design firm. Instead, the airport again relied on its in-house expertise to supplement the internal review team required under Kimley-Horn’s contract.

The final plan set consisted of 294 sheets . . . a production rate of 1.6 sheets per design day, not including specification preparation.

MEM’s assumption of no learning curve turned out to be inaccurate. After design started, the FAA ruled that the master specifications, successfully in use for many projects, were not acceptable for this project without a complete review and resubmittal. The airport lost significant design momentum and was forced to implement a separate track of revision and resubmitting. Those associated adjustments did result in a new learning curve . . . and that was time expensive. Extra man-hours were expended, but the compressed-schedule design time held.

Project management, while focusing on construction, is actually an all-encompassing process, melding planning, design and construction into a viable whole. MEM felt that it had a very good handle on all that and proceeded to make those project-specific modifications that did ultimately work out, but not without some pain and suffering.

Done for the holidays

Construction time was dictated by the absolute need to be done before FedEx Express entered the full flow of holiday operations. MEM stretched it as far as possible by beginning March 1, 2009, and mandating an end on Nov. 30, 2009. Because of the runway’s location, it affected Federal Express operations even more than any of the other projects the airport had undertaken because it in fact cut the airfield in half and required the preparation of strict access/egress taxiing plans to reduce the impact as much as possible.

Extensive modeling by Federal Express determined that maintaining three active crossing points for aircraft throughout the life of the project was absolutely vital. That requirement split the project into three primary phases with each being arbitrarily assigned 100 construction days.

AJAX Paving Industries, a large general contractor with extensive experience, but none at Memphis International, was the ultimately successful low bidder. The compressed-schedule reconstruction of Runway 9-27 began at 4 a.m. on March 1 in a snowstorm. MEM reopened the runway at noon on Nov. 30—exactly on schedule—and the contractor earned the full $2.5 million bonus.

Runway 9-27 is 8,946 ft long x 150 ft wide with 35-ft-wide asphalt shoulders. The concrete pavement covered 213,000 sq yd, including the runway and all crossing taxiways at varying distances depending on actual grade requirements. Asphalt shoulder construction encompassed 94,000 sq yd.

The entire paving section, which is 52 in. thick, consisted of four segments:

  • A 20-in. P-501 concrete pavement (with 650 psi minimum 28-day flexural strength);
  • 4 in. of porous drainable asphalt;
  • 8 in. of cement-treated aggregate base (with 750 psi minimum 7-day compressive strength); and
  • 20 in. of soil cement (with 300 psi minimum 7-day compressive strength).

The sections are on top of a processed subgrade that was compacted to 95% of modified proctor.

The mix design, in accord with recently approved FAA P-501 standards, is based on the Shilstone method, and in this case required the blending of three different limestone aggregates plus sand to achieve acceptable gradation. In practice, the mix proved to be quite consistent overall and produced some of the most uniform edges the airport has ever observed. There was minimal edge slump. The minimum required cementitious material (cement + fly ash) was set at 500 lb per cu yd with water-cement ratio maximum at 0.50 and entrained air content of 5 ½ to 6 %.

Construction traffic was allowed on the pavement once 450-psi flexural strength was achieved, with a minimum cure time of three days. There were no instances where the pavement failed to achieve 450-psi flex in that length of time. Maturity meters were allowed by specification, but the contractor did not exercise that option.

Also in accord with FAA P-501 standards, stringent pre-testing was required to assure that the potential for alkali-silica reactivity was reduced to practically zero. Among other constraints, Class F fly ash was specified for that express purpose.

The first runway concrete pavement placement day was April 27, 2009, and the last runway concrete pavement placement day was Sept. 30, 2009.

Fast learning

This project can only be classified as a dramatic success. The compressed-schedule methodology worked, and MEM will no doubt use it again. However, it should not be undertaken at facilities where large construction happens only occasionally. The owner absolutely must have the experience and expertise to manage all parts of the process. It cannot be left to consultants or contractors.

Over the years, MEM has learned hard lessons that are worth sharing. One of the most important is that fast-track construction does not cost any more than nomal-time construction, and in fact a good case can be made that, on a program basis, it is actually less expensive. The efforts are intense, but the payoff from both up-front dollar costing and revenues generated from time gain are dramatic.

Other things that MEM has learned are that the owner must be directly and aggressively involved in all three segments of project development and construction. Quality of work is never sacrificed to speed, and in fact there is no need to. With capable management, strict standards, stringent monitoring and competent contractors, high quality is easy to achieve. MEM has, however, found it necessary to be aggressively involved in day-to-day project scheduling, materials testing and operations liaison rather than leaving those things to designers, project managers, testing agencies and contractors.

MEM did implement one thing that proved to be quite valuable. It wirelessly linked in with Federal Express’ proprietary aircraft monitoring system. The airport’s field personnel were able to directly monitor aircraft movements and to read exact location, direction, in-bound or out-bound destination and what taxi route would be used. That, of course, was most valuable in adjusting construction traffic flow at the crossings without lost construction time and with no aircraft delays.

One process has become of high value in expediting MEM construction projects. That is the use of hydrated lime or Code-L lime to process wet materials. At MEM the clays are usually wet and often of an expansive nature. Lime treatment improves material quality and produces a workable material almost instantaneously.

Crews can encounter a muddy underground mess several feet deep, and within 24 hours turn it into a stable, strong, compacted subgrade. That saves days of construction time and cost.

There is always one mistake that otherwise well-meaning people make over and over . . . change for the sake of change. On any new project, the temptation is to place a personal stamp on it by implementing changes that may in the long run be of value but are disruptive to fast-track methodology. MEM’s procedures are well-established, but even they are under constant attack. A proven methodology may indeed benefit from adjustment, but that adjustment should never be made until the entire impact has been vetted.

On this project, MEM did make changes, but had a defined goal and knew what the consequences could be. Additionally, it applied them only to this project so that the airport could go back to “normal.”

About The Author: Polk is manager of construction administration for the Memphis-Shelby County Airport Authority.

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