Sydney's airport woes A bold new plan to address€¦ · A bold new plan to address Sydney's...

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COVER STORY A bold new plan to address Sydney's airport woes The current thinking behind expanding Sydney's airport capacity is to provide a second airport either in Sydney'swest at Badgerys Creek or in the south near Holsworthy. However, a quite radical proposal has just been launched by the Pacific Airport Group (PAG), to replace Kingsford Smith Airport with a higher capacity airport platform located on piers close to the shore Just north of the entrance to Botany Bay. Bob Jackson reports on the main engineering and planning aspects of PAG's proposal. I or years Sydneysiders have argued and anguished over where to build I a second airport. Since the 1970s suggested sites have included Galston, Richmond, Badgerys Creek and Holsworthy. About six years ago the previous federal government decided to expand the capacity of the existing Kingsford Smith Airport by building a third runway. Since the third runway came into service it has proved unpopular, with many pre- viously unaffected residents complaining about aircraft noise. And because capacity has been increased at Kingsford Smith, a second Sydney airport now has to wait till early next century before it would be commercially viable. A totally new concept, which promises to overcome all the problems associated with the other sites is now being proposed. It is an airport built offshore just north of Botany Bay heads and half a kilometre out from the shoreline. The proposal, called Sydney Offshore, has been put forward by the Pacific Airport Group (PAG), a design consortium representing consulting engineer Tierney & Partners, architect and planner Hassell and geotechnical engineer Douglas Partners. The pre- liminary design for the airport has been undertaken over the past 15 months and PAG is now in a position where it is confident in going public. The proposal is for an airport located offshore on a concrete platform supported by piers, adjacent to the golf courses of Little Bay and the La Perouse peninsula, east of the existing facility at Mascot. "Using the latest construction David Tierney (I) and Ross Speers ofTierney & Partners discuss the Sydney Offshore Airport proposal. methods, the proposal involves the construction of runways, terminals and all the necessary support facilities for an international airport, founded in rock on the sea floor and linked by a bridge to the mainland," says the preamble to the 50- page proposal. The new airport would reduce noise, pollution and other negative environmental effects over the city, enable 24-hour operation and cater for the growing volume of air traffic, the preamble says. It would also bring benefits in improved land use and value across the suburbs that are currently affected by aircraft noise and allow the trans- formation of the present airport site in a way that would significantly enhance Sydney's urban planning, it says. According to David Tierney of Tierney & Partners, the piled structure would be straight- forward because of the solid sandstone base and the reasonable depth which would vary between 20m at the shallowest part of the platform to 60m at the deepest. " I n view of the fact that 150rn deep piled offshore structures are now being undertaken, established construction methods could be used with confidence," he said. "The scale of the project ENGINEERS AUSTRALIA MARCH I997 25

Transcript of Sydney's airport woes A bold new plan to address€¦ · A bold new plan to address Sydney's...

Page 1: Sydney's airport woes A bold new plan to address€¦ · A bold new plan to address Sydney's airport woes The current thinking behind expanding Sydney's airport capacity is to provide

COVER STORY

A bold new plan to addressSydney's airport woes

The current thinking behind expanding Sydney's airport capacity is to provide a second airport eitherin Sydney's west at Badgerys Creek or in the south near Holsworthy. However, a quite radical proposalhas just been launched by the Pacific Airport Group (PAG), to replace Kingsford Smith Airport with ahigher capacity airport platform located on piers close to the shore Just north of the entrance to BotanyBay. Bob Jackson reports on the main engineering and planning aspects of PAG's proposal.

I or years Sydneysiders have arguedand anguished over where to build

I a second airport. Since the 1970ssuggested sites have included Galston,Richmond, Badgerys Creek andHolsworthy.

About six years ago the previousfederal government decided to expandthe capacity of the existing KingsfordSmith Airport by building a third runway.

Since the third runway cameinto service it has provedunpopular, with many pre-viously unaffected residentscomplaining about aircraftnoise. And because capacityhas been increased atKingsford Smith, a secondSydney airport now has to waittill early next century before itwould be commercially viable.

A totally new concept, whichpromises to overcome all theproblems associated with theother sites is now beingproposed. It is an airport builtoffshore just north of BotanyBay heads and half a kilometreout from the shoreline.

The proposal, called SydneyOffshore, has been put forwardby the Pacific Airport Group(PAG), a design consortiumrepresenting consultingengineer Tierney & Partners,architect and planner Hasselland geotechnical engineerDouglas Partners. The pre-

liminary design for the airport has beenundertaken over the past 15 months andPAG is now in a position where it isconfident in going public.

The proposal is for an airport locatedoffshore on a concrete platform supportedby piers, adjacent to the golf courses ofLittle Bay and the La Perouse peninsula,east of the existing facility at Mascot.

"Using the latest construct ion

David Tierney (I) and Ross Speers ofTierney & Partnersdiscuss the Sydney Offshore Airport proposal.

methods, the proposal involves theconstruction of runways, terminals and allthe necessary support facilities for aninternational airport, founded in rock onthe sea floor and linked by a bridge to themainland," says the preamble to the 50-page proposal.

The new airport would reduce noise,pollution and other negative environmentaleffects over the city, enable 24-hour

operation and cater for thegrowing volume of air traffic,the preamble says.

It would also bring benefitsin improved land use and valueacross the suburbs that arecurrently affected by aircraftnoise and allow the trans-formation of the present airportsite in a way that wouldsignificantly enhance Sydney'surban planning, it says.

According to David Tierneyof Tierney & Partners, the piledstructure would be straight-forward because of the solidsandstone base and thereasonable depth which wouldvary between 20m at theshallowest part of the platformto 60m at the deepest.

" I n view of the fact that 150rndeep piled offshore structuresare now being undertaken,established construct ionmethods could be used withconfidence," he said.

"The scale of the project

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would also mean that once part of theplatform is completed, construction couldproceed from a rig operating off thealready completed parts of the deck."

The airport would provide taxiways,runways, passenger terminals andnecessary maintenance facilities.However, some support services such asair catering and airline administrationfunctions could remain at the present siteat Mascot.

A wide arterial road corridor, AnzacParade, already exists connecting the cityto the area. The divided road also has anold tram easement down much of itslength and this could be made use of toprovide modern light rail access to the

6 Once we started

studying the noise

contours we

realised we could

get within 0,5km of

the shore,

airport. A rnultitane bridge with provisionmade for both road and rail transportwould connect the airport to the mainland.Provisions could also be made forextending to Sydney Offshore the NewSouthern Railway, a BOOT projectpresently under construction to serviceSouth Sydney, Mascot and KingsfordSmith Airport,

Fuel storage would be on land andpumped through pipelines across thebridge.

There would be two runways - one4km long and the other 3km long -aligned 20° east of true north makingthem approximately parallel to the-coast.The design also allows for the inclusionof a third cross runway for smaller aircraftif further study found this to be necessary.The international and domestic terminalswould be on the shore side of the runwaysand taxiways, together with hotels andshops. However, a satellite building forembarking and arriving passengerswould be located between the runwaysand would serve 72 aircraft gates.Passengers would move between theterminals and satellite in a shuttle linkbeneath the platform level of the airport.

Alternative configurations have alsobeen considered including:• locating support facilities on the

present Prince Henry Hospital site(subject to closing of the hospital andpurchase of the site from the stategovernment)

• locating the terminals between therunways and integrating them with thesatellite and gates

• separating the international anddomestic terminals by carparkingstructures

• locating part of the terminals on thePrince Henry Hospital site and limitingtraffic access to the platform

• locating the terminals under the decklevel in a deep truss superstructure.

The surface of the offshore platform forthe airport would be 17m above highwater ordinary spring tide (HWOST) withsuperstructure clearance of 10m HWOSTto allow for the predicted 100-yearmaximum extreme wave of 15m(measured between trough and crest).

Tierney said he had originallyconsidered a floating airport but afterdiscussions with Douglas Partners couldsee that founding it on the sea bed wasa better option.

"Once we started studying the noisecontours we also realised we could getwithin 0.5km of the shore (within the70dBA limit).

"It then became one of thoseserendipity situations when we found outthat the area;we were looking at wasbounded by golf courses and open spacewithout surf beaches, thus providing an

; even better noise buffer."However, at 0.5km from the shore,

about 69ha of privately owned mediumdensity houses between Malabar andLittle Bay could fall just inside the 70dBacontour, as would an area of nationalpark and golf course.

The proposal concedes that manySydneysiders might baulk at the visualimpact of a large offshore structure andwould oppose it on these grounds.However, it notes that the visual impactwould be primarily local.

"The extent of the visual impact willdepend on the finished height of thestructure in relation to the cliffs along thecoast and the ultimate distance from thecoastline, although the visual impact ofplanes taking off and landing is likely tobe significant along most of the immediatecoast," it said.

Doubts regarding the project are also

echoed to some extent by the chairmanof the Maritime Panel of EAust's SydneyDivision, Ray Rice, who agrees that, whilethe project is technically feasible, itsenvironmental impacts and economicviability would have to be very closelyexamined.

Although a full environmental impactstatement (EIS) would be prepared if theproposal were taken up, the principalenvironmental impacts have already been

anticipated. None of those yet appearserious enough to challenge the viabilityof the project.

Apart from the environmentalconsiderations dealing with theconstruction phase of the proposedairport a permanent structure could haveimpacts on:• littoral drift from the impact of the piers• waves and surf• shading of the sea floor

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• sediment drift and scour• polluted run-off from aircraft operations• aviation accidents• the marine ecology• recreational and commercial fishing

and shipping movements to and fromPort Botany.

Whatever the final form of the structure, itwould be expensive and would have tobe justified financially.

The proposal points to the opportunity

and the bridge - using conventionalconstruction methods is estimated at thisstage at several billion dollars, much morethan the cost of establishing aconventional airport. However, the gapwould be reduced if the extensiveinfrastructure required to service asecond airport in Sydney's west weretaken into account.

"The next important task is to refineand confirm the cost of founding the

ship collision.Tierney said a lot of work still needs to

be done on such questions as theexpected durability and life of thestructure. But he is confident that with theappropriate concrete mixes and cathodicprotection systems a very durablestructure could be obtained.

One of the biggest challenges wouldbe the sheer size of the civil works.

"The deck would be about 3.3km2 in

to redevelop the 8km2 area of the presentairport, which could generate significantrevenue from the sale of land. Theredevelopment would also substantiallyenhance property values in Sydney's innerwest and southern suburbs and open upmore areas for redevelopment and urbanconsolidation, areas that are already wellprovided with infrastructure support.

However, the cost of the mostexpensive elements - the piers, the deck

structure," said Tierney."For example, piling rigs as used in

the oil industry can cost $200,000 a day,but you would only use a piling rig tofound a small part of the structure. Thenyou could cantilever out using methodssimilar to those for bridgebuilding."

The structure would also becantilevered around its edge so that thepiles would be between 5m and 10m infrom the perimeter to protect them from

A An artist's impression of what a rede-veloped Kingsford Smith site and the Syd-ney Offshore Airport would look like.

area and would use about three millioncubic metres of concrete which is aboutone years concrete production in NSW,"he said.

The federal Ministry for Transport andRegional Development, in response tothe proposal, said it is in favor of a second

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A plan view of the proposed airport design and configuration.

airport rather than a replacement option.it said two second-airport proposals arebeing considered - Badgerys Creek andHolsworthy.

Of these Badgerys Creek is thepreferred option and a draft environmentalimpact study (EIS) relating to bothBadgerys Creek and Holsworthy will bereleased for public comment in May.Consulting engineer Rust PPK is carryingout the EIS for the ministry.

Three federal government back-benchers from the Sydney area - PaulZammit, the member for Lowe; DannaVale, the member for Hughes; and JackieKelly, the member for Lindsay - havepublicly endorsed Sydney Offshore.

"So far no-one has been able toclaim that this airport is not

feasible either from an engineering or aneconomic perspective," Zammit toldEngineers Austral/a.

"Kingsford Smith has a reputation asan inefficient airport to the extent that it iscosting the airlines which use it up to halfa billion dollars a year.

"The new airport would cost about $8billion, a figure similar to that for HongKong's new Chep Lak Kok Airport. Thisis not an impossible amount of money,which would largely be

recouped after a decade of operation."I come from an ethnic background

and admit to being greatly impressedwith the engineering vision and the hardwork of the multiethnic workforce whobuilt the Snowy Mountains Hydro-ElectricScheme.

"I see the Sydney Offshore proposal ina similar way - to those who wish to knockthe idea my answer is why not?" •

A perspectiveview of how theconstruction of

the airportplatform couldbe carried out.

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