Dig for Solutions to Retain Operations While Replacing Pipes
Dig for Solutions to Retain Operations While Replacing Pipes
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Dig for Solutions to Retain Operations While Replacing Pipes
By: Dan Eekhoff 2 minute read

Plans to extend a runway and lengthen taxiways at Philadelphia International Airport arrived with a heavy burden: The pavement paths would pass over existing pipelines used for transferring fuel.

Plans to extend a runway and lengthen taxiways at Philadelphia International Airport arrived with a heavy burden: The pavement paths would pass over existing pipelines used for transferring fuel.

Such new construction would result in loads producing unacceptable pipe deflections on the existing 40-year-old fuel transfer lines. Mitigating these new loads on old pipelines, in place, would also be cost prohibitive. The design team recommended relocating newly constructed fuel transfer pipelines, taking into consideration the long-term development from the Airport's Master Plan, which also included relocation of the aviation fuel storage facility along with a host of electrical upgrades.

And, of course, all of this work could not affect airport operations, making sure the airport remained fully functional during construction. Taking the smart approach made the difference. To relocate fuel lines around and under existing runways, taxiways and other airport objects and equipment, the smart approach considered:

  • "Right sizing" the new pipelines. Calculations taking into account the airport's current and future needs revealed that existing pipes were significantly oversized, so much so that the system could not clean itself. The new plan called for new dual 20-inch diameter transmission lines to maintain a peak fluid velocity in the desirable range of 7-8 feet per second.
  • Establishing the most efficient route. Taking into consideration various design parameters, the design team identified routes that would avoid existing structures, maximize open-cut pipe placement to minimize construction costs, and align with service roads to minimize long-term maintenance costs.
  • Avoiding potential trouble spots. Trenchless methods selected would incorporate transitions that did not require any runway or taxiway closures during the installation period.

Underground Answers

A key component of any solution involves trenchless technologies: when, where and which method to use.

The project team consulted numerous experienced contractors and considered three trenchless approaches: auger boring; horizontal directional drilling (HDD); and microtunneling. Here's a closer look at the tunneling options and how they compared:

  • Auger boring was deemed infeasible for two main reasons: spatial requirements made it impossible to avoid entering safety areas or otherwise disrupting airport operations. The soft soil raised accuracy concerns and would have limited runs to no more than 400 feet.
  • HDD was determined to be feasible only for shorter runs. On the plus side, the method generally is the least expensive for trenchless installations and would not intrude into safety areas and other potential trouble spots. But several negatives could not be overcome, including those related to constant grade requirements and an inability to move accurately through the soft soils. Such complications could result in dips in the fuel lines when passing under runways.
  • Microtunneling, the most expensive of the three options, proved to be the only feasible alternative for the project's longer runs. While its spatial needs were significant, tunneling activities could be moved outside safety areas to prevent disrupting airport operations. Also advantageous: Fuel lines and electrical conduit could be carried in a single, large casing; and pipes could follow a precise, laser-guided path through the soft soils, even spanning long distances.

Dan Eekhoff is a project manager in the Aviation Group at Burns & McDonnell.


Fuel for Thought

Facts and figures from project work scheduled to start this fall at Philadelphia International Airport:

  • Client: PHL Fuel Facilities LLC and the PHL DOA
  • Scheduled completion: Dec. 31, 2016
  • Pipeline size: 10,000 linear feet
  • Cost (design): $500,000
  • Cost (construction): $20 million
  • Value engineering savings (est.): more than $5 million
  • Trenchless solutions: 2,500 linear feet
  • Microtunneling: 1,200 linear feet, the longest continuous section dedicated to airport fuel transfer lines in the U.S.
  • Hours of airport operation lost (est.): 0

 

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