Queenstown Airport Runway Extension – DuraGrid X and Drainage Composite

As part of a major project to increase flight safety, Queenstown Airport is extending each end of their runway. Nestled tightly between the main arterial SH6 route leading into Queenstown along Kawarau Road and a steep drop toward Hawthorne Drive, there is minimal land available for further extension, so to increase the current runway end safety area (RESA) of 90m at each end, Queenstown Airport will install Australasia’s first engineered materials arresting system (EMAS), effectively increasing the margin of safety to 240m RESA.

EMAS beds are a prefabricated cellular cement block system, designed to crush whilst embedding the aircraft’s wheels, safely bringing the aircraft to a controlled stop with minimal damage. Water management and ground stabilisation was also required to create suitable ground conditions beneath the system, so project engineers sought a solution using the Drainage Composite and DuraGrid X stabilisation geogrid.

DESIGN

Extending beyond the 45m width of the runway, the 70m and 73m long extensions required a full dig out. Both the Drainage Composite and DuraGrid were placed between the levelled subgrade and a 400mm AP40 basecourse layer. A 60mm AC14 Asphalt layer was then placed on a layer of ChipSeal before the EMAS beds were installed. The existing runway and EMASMAX beds were tied together using a concrete anchor beam designed by Runway Safe.

The Drainage Composite’s ability to passively relieve water pressure makes it ideal for drainage under buried structures, while DuraGrid X geogrids provided stabilisation to the runway pavement, making both products ideal for this project.

INSTALLATION

During construction, access to the runway was only allowed once the last plane had landed or taken off, preventing disruption to flight schedules at Queenstown Airport. Installation was done in 20m wide strips across the runway to make sure Downer had enough time to bring each strip up to the full height each night.

Once levelled, the Drainage Composite and DuraGrid were rolled out and covered, keeping the ends exposed so they could be overlapped the following day by the adjoining layer. Downer was required to install all levels within each strip by a certain time during the night to make sure the EMAS system was placed before the first flight, otherwise the exposed asphalt or base course layers could have become a safety hazard.

By extending the effective runway end safety area using EMASMAX beds, Drainage Composite and DuraGrid, Queenstown Airport have gained maximum use from limited land space.

The DuraGrid and Drainage Composite used provided the following benefits to the project:

• DuraGrid X provided critical pavement stabilisation, ensuring a strong and durable foundation beneath the EMAS system.
• The Drainage Composite enabled efficient sub-surface drainage, relieving hydrostatic pressure and protecting structural integrity.
• Both products supported fast, staged night-time installation, helping meet tight construction windows without disrupting airport operations