LGW Rapid Exit Taxiway

Project summary

Gatwick Airport issued a tender for the construction of an additional Rapid Exit Taxiway (RET) to 06R-26L to facilitate additional movements per hour on the main runway. The design called for a fully flexible construction with pavement thicknesses in excess of 1m; the provision of slot drains to the pavement edge and land drains to capture ponding water and attenuate flow. Flow control hydrobrakes were also specified to ensure water entering the existing storm water network was sufficiently restricted. The design also called for the full integration of the RET with the existing Aeronautical Ground Lighting (AGL) system and the provision of associated pit and duct infrastructure.

Scope of services

The value engineering assessment looked at challenging the existing pavement design by contrasting it with both the Defence Estates DMG27 guide and the FAA FAARFIELD methodology. The assessment also sought to propose flexural-composite construction derived for use at BAA airports in the late 1990s to facilitate shallower pavement constructions in limited-possession windows. The review also examined rationalising the proposed drainage layout, which consisted of a substantial number of new manholes, to simplify attenuation and to reduce the AGL pit infrastructure associated with the requirements of the new RET.

General arrangement of new RET

Proposed alternative drainage solution

The results showed adopting alternative design methodologies could result in at least a 25% reduction in pavement thicknesses and the potential to remove approximately 7no. manholes and over 100m of pipework subject to model verification. Additionally, the number of AGL pits was found to be above the minimum quantity required and further savings were proposed in this area.

Benefit

The value engineering assessment allowed the tendering contractor to propose budgetary savings on alternative proposals enabling further discussions to take place on design refinement with the employer. The alternatives also provided an opportunity to re-examine the contract programme and explore ways and means to accelerate construction activities and mitigate the risks associated with extended possession works on a live airfield.