Building the Sceniscender cable car in New South Wales was a construction challenge for helicopter pilots. David Bennett reports.
For nearly six months of last year there was an added attraction for visitors to Austalia's Scenic World theme park, due west of Sydney in the World Heritage-listed Blue Mountains National Park. Helicopters plied up and down the steep sided hillside, fetching and carrying materials for a major new cable car to serve the development.
The Sceniscender, as it is called, carries 84 visitors at a time down a 220m cliff face of massive weathered sandstone into the rainforests of the Jamison Valley.
Designed and project managed by consultant Sinclair Knight Merz the installation includes new stations at the top and bottom, a machine room, ropeway support towers, plus restaurant, cafÚ and gift shops, which along with upgraded parking facilities are part of an 18 month A$20M (US$10M) refurbishment programme.
With no access up and down the cliff face to the site of the lower cable car station, the fleet of helicopters solved the logistics problem of getting equipment in, says John Buttenshaw, project manager for Sinclair Knight Merz.
For the heaviest steel components - the Bobcat skid steer and mini excavator for foundation work on the station and tower footings - a Russian Kamov twin rotor helicopter with a lift capacity of 4.5t was needed.
A fleet of single rotor Bell helicopters, able to lift 1.5t, managed the 1,500t of reinforcement, formwork, structural steel and roof sheeting. These also helped place some 475m 3ready mixed concrete from a supplier in nearby Katoomba, pouring 0.4m 3kibble (skip) loads into the excavation while the helicopter hovered above.
'Using two helicopters, we were emptying a 5m 3concrete truck in about an hour, ' says Buttenshaw. 'This may seem slow considering it took only a minute to fly a helicopter load down to the bottom of the cliff, but a lot of time was taken up manoeuvring the helicopter over the right spot on the valley floor, ' he adds.
A further factor was the weather. Despite the advance weather forecast from the national weather station, fog would suddenly roll into the valley and envelop the site, or the wind speed would pick up, just when the helicopters were about to make a delivery. A number of missions had to aborted or delayed.
The Bell helicopters also flew in much of the construction material for a second 700m long boardwalk connecting the Sceniscender with the existing station for the park's Scenic Railway.
'By the time the last delivery of materials was flown to the lower station, the six helicopters had made 1,700 trips between them up and down the valley, ' reflects Buttenshaw with amazement.
The concrete pad foundations for the intermediate steel lattice cable support tower, positioned on the edge of the cliff were placed with a concrete pump, using a 100m delivery line.
The top station, which also houses the mechanical and electrical equipment for the cable car, is a conventional concrete box structure with 7m high, 600mm thick reinforced concrete walls, the floor slab keyed into the underlying sandstone.
With the support tower and station complete, the helicopter was used again to string a small diameter drag line between the bottom station and the intermediate tower.
The line was attached to the 57mm track ropes that support the cable car, which were winched from the top station and then tensioned, producing a pulling force on the top and lower stations of 2,500kN.
The Sceniscender, which is 5.5m wide by 4.5m long and weighs 16t fully laden, travels at maximum speed of 5m/s. The cable car, the ropeways, and the steel support towers were all supplied by Swiss company Dopplemayr, which also designed and built the mechanical equipment and control systems.
The upgraded car park, and the associated civil and building work was carried out by Sydneybased contractor ADCO Construction.
Scenic World was kept open throughout, with construction co-ordinated to ensure the park was able to operate at full capacity. The Sceniscender opened to the public on 22 December 2000, in time for the peak Christmas and New Year holiday period.
'Sinclair Knight Merz has done a great job under difficult circumstances, ' says proprietor Philip Hammon.
Work on the bus parking area and boardwalk is due for completion later this year with refurbishment of the existing buildings planned to start in 2002.
Client: Katoomba Scenic World Project manager, civil/structural/M&E engineer: Sinclair Knight Merz Architect: PMDL Architecture + Design Landscape architect: Pittendrigh Shinkfield and Bruce Cost planner: Page Kirkland Parnership Surveyor: Mark Bowler and Associates Main Contractor: ADCO Construction Cable car equipment and control systems: Doppelmayr Tramways of Switzerland Helicopter cranage: McDermott Aviation Project cost: US$10M ($5M on the Sceniscender, $1.5M on the car park structure, $250,000 on the boardwalk, $750,000 on bus parking areas and $1.25M on the refurbishment of the existing buildings).