Engineering consultancy Aurecon reports that it has started rebuilding the secondary runway at the Waterkloof air force base to international standards.
The construction contract was awarded to the successful contractor in December 2010, after the completion of the upgrade of the primary runway in October 2010.
Despite geological challenges regarding dolomite in the area, Aurecon project engineer Bruce Morton reports that work on the first contract was completed ahead of schedule.
“The first contract comprised the upgrading of the main runway and some of the taxiways. The second contract will see us completely rebuilding the secondary runway to international standards, although not to the same specifications as those of the primary runway,” he says.
The primary runway is 3 500 m long and can now accommodate some of the heaviest aeroplanes in the world, including the Airbus A380. The secondary runway is 1 800 m long and will be used for smaller aircraft calling at the air force base.
The upgrade of the runways, taxiways and airside facilities to accommodate future aircraft operations is in line with the strategic and national importance of the air base.
Future expected aircraft include the Airbus cargo aircraft, the Ilyushin IL-76, the Antonov An-124, the Boeing 747-400 and the Boeing C-17, as well as other large-bodied military and commercial heavy aircraft.
It is also a proposed diversion airport, as well as providing a strategic airlift and refuelling base for aircraft of the South African Air Force.
The upgrades should ensure the continued future operational status at the base for a period of 30 years, Aurecon states.
The Waterkloof air force base consultants joint venture, a consortium led by Aurecon in conjunction with Ndodana Consulting Engineers and VGI Consult, undertook the redesign for the runways and taxiways.
The design ensures that the base meets International Civil Aviation Organisation standards, as well as the Department of Public Works’ guidelines regarding infrastructure provision on dolomite.
The construction undertaken in phase one included extensive excavation of the existing runway pavement structure to depths varying between 2 m and 3,5 m, which included the full 55 m width of the central section of the runway.
Dynamic compaction was performed over the entire prepared surface over a four-month period to mitigate the risks associated with dolomitic soil conditions and the formation of sinkholes.
During construction, as many as 14 cranes dropping steel masses of 12 t from a height of 18 m were employed to complete the dynamic compaction within the allowable period. Thereafter, fully instrumented concrete raft foundations were constructed under both the thresholds and the landing areas of the runway.
Seventeen raft foundations measuring 55 m × 55 m were constructed, with each raft cast in one continuous operation within a 16-hour period, using more than 400 concrete trucks for each raft foundation. These represent the largest continuous pour raft foundations con- structed to date in South Africa.
Further, major service tunnels were constructed under the main runway and primary taxiways to route all services from the west to the east of the air force base.
The entire airside stormwater drainage system was also upgraded to the Department of Public Works’ prescribed dolomitic standards. All services have been placed within high-density polyethylene piping and ducts have been installed within the pavement structure for the installation of all the airfield lighting.
“The final surfacing of the runway consists of a specifically designed ultrathin friction course, which has the benefits of increased skid resistance and improved drainage,” Morton adds.
Meanwhile, a solar-powered temporary lighting system has been installed along the main runway and the primary taxiways, until such time that the permanent runway lighting contract can be undertaken, before mid-2012, upgrading the lighting system of the base to a category II precision approach, with centre line lighting along the main runway.
“The current construction works at the air force base will focus on the upgrading of the secondary runway and the installation of the permanent airside lighting system. This construction is planned for completion by the middle of 2012,” Morton concludes.
Further infrastructure development at Waterkloof air force base includes the development of a new strategic airlift facility, a new air traffic control tower and a fire station. The new strategic airlift facility will include a new flight lane and hardstands, appropriate hangars to house aircraft and a maintenance hangar and a wash bay, as well as new logistics buildings.