"Today, emergency crews will pump more than 350 cubic metres of cement into the hole. They have already pumped 700 cubic metres into the pit.The NSW government said yesterday that the residents, who have been given hotel accommodation by the tunnel operators, are entitled to compensation."

"The operator, a Thiess John Holland joint venture, said it was covered by insurance." Well here the news report falters - the actual venture is called the "Lane Cove Tunnel Consortium" (LCTC) and Thiess John Holland is the principal subcontractor in the design and construction of the tunnel for LCTC.

Jasmine Lau gets another mention today - the poor university student who can't get to her precious text books. Uni students! (or any other students) when your apartment block starts collapsing... what item should you grab first when evacuating?
a. Your collection of seashells from Hawaii;
b. The bible;
c. Your most expensive clothes and accessories; or
d. Your textbooks and notes.

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Living on burrowed time

Sydney sits on sandstone, a foundation that has always tempted engineers to build below ground, writes John Huxley.

Shortly after 10am yesterday a Sydneysider posted on the internet a spoof advertisement for a unit in the collapsed Kerslake housing block in Longueville Road, Lane Cove. "For sale," it read. "Apartment with underground car park. Oops, sorry, underground apartment with above ground car park."

At least someone could see the funny side of yet another incident which suggested that, in places at least, Sydney is literally falling apart at the seams.

For Kerslake residents, for constructors of the nearby tunnel, for commuters stranded by road closures and most of all for politicians desperately seeking to restore the city's crumbling faith in big public projects, the timing could hardly have been worse. It coincided with further embarrassing revelations about the costing and construction of the Cross City Tunnel, whose opening has so far aggravated rather than alleviated traffic chaos throughout Sydney.

And, as Sydneysiders began rushing onto talkback radio and newspaper websites yesterday morning, the collapse followed other tunnelling accidents and mishaps. They include the death of a worker in the Cross City Tunnel and the subsidence caused to nearby homes during excavations for the Eastern Distributor.

Yesterday, as engineers and geotechnical experts investigated the Lane Cove incident - initially blamed by the contractors on an "unforeseen geological event" - the local MP, Anthony Roberts, was seeking answers.

Had the construction company, Leighton Holdings, been properly monitoring soil and rock? Had it been "cutting corners" to complete a project that is running months ahead of schedule? How can similar incidents be avoided in future?

"My understanding is that there is allegedly three engineers who have resigned in the past two weeks from the tunnel operations," Roberts said. "Do we have enough qualified people managing the tunnel?"

He said resident of the Kerslake block had told him they did not feel they were being properly informed by the tunnel operator.

"My first concern is for the people who will probably lose their homes now," Roberts said. "What do we do with them? How can we look after them? That's my major concern, and the second one is that this one doesn't occur again."

His questions reflect growing public dismay, anger and fear over the competence of contractors, the honesty of politicians and the terrors lurking within an underground Sydney that seems increasingly to resemble Swiss cheese. Crumbling Swiss cheese.

Brian and Barbara Kennedy, authors of Sydney Tunnels, say the city is a honeycomb of man-made excavations. The earliest date back to the first days of European settlement, and if coastal cave dwellings are included, beyond.

As the Kennedys say: "Few people walking along Sydney streets are aware of the complex network of historical tunnels beneath their feet."

Apart from the familiar roads, there are thousands of kilometres of tunnels intended for carrying water, sewage, power cables, gas mains, telephone lines and railways, some of which are in use, some of which have been abandoned.

Then there are the numerous cellars, crypts, vaults, defence installations and secret escape passages and shelters built, appropriately, for endangered politicians.

There are compelling reasons for such subterranean activity in Sydney, explains Simon Knight, of the Australian Underground Construction and Tunnelling Association, whose members include contractors, consultants and public utilities, such as the Roads and Traffic Authority and Sydney Water.

"The city does lend itself to tunnelling. The topography is quite rugged so the shortest route from A to B may be underground,' Knight says. "It also sits on rock - typically, sandstone with some seams of shale - that is beautiful to excavate. It's easy to cut out and it is very stable, almost self-supporting - though we wouldn't allow it to stand like that, but would use bolts."

Moreover, Sydney's underground is not rearranged periodically by earthquakes. Indeed, according to engineers, so encouraging are the conditions and so advantageous are the long-term cost and convenience benefits of going underground in Sydney, the surprise is that it has not been done more often.

Underground logjams do occur: earlier this year it was reported that the route for a proposed underground rail line through the CBD could be blocked by existing infrastructure, including basements and a main sewer line.

But far from being the Swiss cheese imagined by residents, Sydney looks more like a piece of uneaten cake - especially compared to American cities such as New York and Chicago, and European cities such as London.

"To talk of Swiss cheese is a gross exaggeration. We don't really have many tunnels at all," says Knight, whose association is working on a new industry code of conduct prompted by the Cross City Tunnel accident. "In London, they don't even know where half their tunnels are."

By contrast, he insists, Sydney knows basically where its tunnels are, has them verified by service searchers before construction work and - despite yesterday's "unforeseen geological event" - can anticipate most potential problems.

"Sydney sandstone does not subside, but you can go through a blocky area where there are lots of joints and faults. And there you would have to design for the potential of blocks to fall out. Sandstone tends to collapse in sizeable blocks and you can design for that. It should not be an issue.

"The shales that overlie the sandstone are a bit more difficult to excavate, and they may progressively fail because they are not strong. But that's a problem that can be managed."

Inevitably, though, accidents can and do happen. They are nothing new, according to Jon Breen, a former engineer and historian of Sydney's infrastructure.

He relates how, in the 1930s, a section of Busby's Bore, an early water supply, collapsed and part of Oxford Street subsided, reportedly due to prolonged vibrations through surrounding wet sand caused by trams. In the 1970s, contractors putting a telephone cable through Dalley Street, near Circular Quay, encountered stiff resistance from petrified timbers associated with a long-abandoned wharf.

More recently, work on the Sydney Conservatorium of Music was slowed when contractors came across a section of early colonial road not far from the surface.

An invaluable piece of heritage? Or just an "old drain", as one archaeologist put it? The ensuing debate is likely to be dwarfed by that now unwinding over the Lane Cove collapse.

As homebound motorists fumed at the continuing road closures, the State Government fielded more demands for inquiries and Telstra redirected calls from the site, the Kerslake residents were moved to accommodation in North Ryde.

Grant Philipp, a 37-year-old mobile phone company director, was already counting the cost. He bought one of the two-bedroom ground-floor units more than two years ago on the birth of his daughter, Charlotte, to give to her on her 21st birthday.

"It looks like I'll be giving her the deeds to a huge hole," he said.

He said a unit upstairs had been sold recently for $270,000 but he believed his - which he rents out - would have been worth between $300,000 and $350,000.

Although his real estate agent had told him that his insurers wouldn't cover the loss in rent, he felt sure the RTA would see the owners properly compensated.

"It's a bit of a disaster for the RTA. They won't want more bad publicity on top of the Cross City Tunnel," he said.

Philipp wouldn't get a fight with the Minister for Roads, Joe Tripodi, over that comment.

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Stability of rock hard to predict

Sydney's sandstone has some big cracks in it, but shale presents additional problems for tunnel builders because of its instability, geologists and engineers say.

And while many precautions are routinely taken during tunnelling to prevent subsidence, not all problems during big excavations can be predicted.

Robin Offler, a University of Newcastle geologist, said shale was a very weak rock and often required additional structural reinforcement. "You have to make sure it doesn't cave in or peel off," Associate Professor Offler said.

John Small, director of the Centre for Geotechnical Research at the University of Sydney, said tunnelling was a relatively safe enterprise. "But when you're dealing with the ground there are a lot of unexpected things you come across. Accidents do happen in tunnelling. We have to accept that."

The Herald raised the issue last month of fault zones in the rocks under the city posing a growing problem as the amount of commercial and household excavations increases.

A new geological map of Sydney identified four major faults running up to 45 kilometres across Sydney, that, if hit upon during excavations, could involve additional costs to shore up a site. The Woolloomooloo Fault Zone, for example, was encountered in both the Eastern Distributor and the Cross City Tunnel.

None of the four faults are close to the site where the Lane Cove Tunnel collapse occurred, but it is not known how many smaller faults lie between these big ones.

Scientists contacted by the Herald would not comment specifically on yesterday's collapse at Lane Cove.

Professor Small, however, said that while tunnel builders drilled boreholes to predict the type of rock they would encounter, there could be surprises in between. "There is always a little bit of uncertainty. You need to take care as you tunnel."

It was standard practice to monitor the relative position of rocks in a tunnel and on the surface to detect unusual movements beyond the normal release of stress in the rock after excavation that would suggest a problem.

Decisions on the amount of structural reinforcement that was needed depended on the pattern of any tiny faults, or joints, that were identified in the rock or measurements on its strength.

Particular care had to be taken with shale, which deteriorated more than sandstone, Professor Small said.

"It is very prone to weathering. Some shales can turn to mud. Or there could be faults that tend to be unsafe," he said.

Scott Sloan, a professor of engineering at the University of Newcastle, said that geotechnical engineers had a difficult job, and tended to take many precautions because the consequences of a mistake could be huge. "When you think of the amount of tunnelling they have done their record is pretty good."

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Rush to save Lane Cove flats

Emergency crews will continue today to try to secure the foundations of a partially collapsed Sydney block of flats.

A total of 47 residents of the units in Sydney's north, were evacuated yesterday when a section of tunnel in the Lane Cove tunnel project collapsed, creating a large hole in front of it.

One corner of the three storey building is perched over the massive hole near the Pacific Highway exit ramp on Longueville Road.

The hole grew overnight and more bricks from the building fell into it, Macquarie Radio reported today.

Today, emergency crews will pump more than 350 cubic metres of cement into the hole.

They have already pumped 700 cubic metres into the pit.

Engineers would also continue their inspection of the site, police said.

The NSW government said yesterday that the residents, who have been given hotel accommodation by the tunnel operators, are entitled to compensation.

The operator, a Thiess John Holland joint venture, said it was covered by insurance.

Both eastbound lanes of Epping Road would be closed until at least this afternoon, police said.

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Tunnel takes its toll on mortar

It was meant to fix Sydney's traffic problems. But the $1.1 billion Lane Cove Tunnel created the city's worst congestion in years as it undermined a three-storey block of flats, leaving dozens of people homeless.

The entire block looked certain to be condemned last night when part of one flat fell into the 10-metre deep hole created when the tunnel punctured the road at 2am yesterday.

Firefighters had to bash down doors to alert sleeping tenants who were unaware of the danger. Some of the 47 evacuees heard a loud noise before seeing a massive gash in a water main.

The Premier, Morris Iemma, ordered an inquiry into the collapse and promised the evacuees would receive fair compensation. "We want to get to the bottom of what has happened," he said. "But the important thing is to ensure the welfare of the residents."

Most of the evacuees had to spend last night in emergency accommodation at a conference centre at North Ryde, paid for by the tunnel's builders, Thiess John Holland. It is not known how long they will be there or when they will be allowed to return to their homes to collect personal effects.

Grant Philipp, 37, a mobile phone firm director who bought one of the ground floor flats to give to his two-year-old daughter, Charlotte, on her 21st birthday, said: "It looks like I'll be giving her the deeds to a huge hole." He said he understood one occupant's budgie was still in the block.

Jasmine Lau, 24, a law student who lives in one of the back flats, said she was concerned because she could not get back to retrieve text books for her final exams.

The collapse on Longueville Road, near the Pacific Highway, caused lengthy traffic delays yesterday and commuters face another gruelling peak hour this morning as police warn of continued citybound road closures.

Excavators had been trying to tunnel through an unusual section of shale - the site of an tunnel ramp which intersects with a ventilation shaft which is below another exit ramp for Longueville Road - when the collapse occurred. They said they had been taking extra precautions in the section.

Residents reported a large grating sound. Tenants Karen Bruce and Rob Colquhoun were first to raise the alarm.

Moments later, a water mains burst. A spokesman for Sydney Water, Colin Judge, said it was most likely caused by the subsidence. However, the release of water exacerbated the collapse, making the hole bigger and tearing at the foundations of the front of the Kerslake block.

A spokesman for Thiess John Holland, David Saxelby, insisted all appropriate geological testing had been conducted on the site and said the collapse was an "unforeseen incident".

Mr Saxelby apologised to "the souls who had been relocated out of their homes", and pledged "indefinite" support to them, even if their building was later condemned.

"Obviously, there will be issues of compensation involved and we don't resile from that," he said.

"But this is no rush job … this is a major project that has gone extremely well, and we have not been taking any short cuts."

The Opposition Leader, Peter Debnam, called for an indefinite stop to all work on the tunnel, pending the results of a full safety audit. The Government rejected his calls.

After an initial WorkCover inspection, work resumed on the tunnel yesterday afternoon - albeit in sections not directly affected by the collapse.

The NSW Assistant Police Commissioner, Mark Goodwin, said 1000 cubic metres of fast-setting concrete were poured into the hole to stabilise the area. The pumping process was not expected to finish until later this morning.

Lane Cove's Mayor, Ian Longbottom, said it was clear part of the building was unsafe and he was seeking a thorough explanation.

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Suffering drivers face days of delays

Motorists face days of traffic chaos as both city-bound lanes on Longueville Road at Lane Cove remain closed until this afternoon and a major link to the Pacific Highway is blocked indefinitely.

Police are pleading with drivers to avoid the area around the site of the road collapse above the Lane Cove Tunnel, after traffic in both directions was gridlocked for most of yesterday.

The Roads and Traffic Authority is waiting for the results of an engineering and structural assessment of the site from the builders, Thiess John Holland, before deciding when the city-bound lanes can reopen.

The RTA is working also with the Ministry of Transport to minimise disruption to public transport along busy Epping Road, which is one of Sydney's busiest roads during the morning peak period.

A link to the Pacific Highway from Longueville Road will remain closed for many days while emergency teams work to stabilise the area and block the large hole. Motorists are being diverted to Centennial Avenue.

Police Superintendent Doreen Cruickshank, the North Shore local area commander, said police were asking motorists to avoid the area today and use other routes for their own safety.

"I'm very mindful that a lot of people do use this road. However, I would stress to them if you could just bear with us, it is for your own safety," Superintendent Cruikshank said. "Please, if you can avoid the area, we would appreciate that."

She said clearways would be extended during peak hour this morning on alternative routes along the Pacific Highway, Mowbray Road, Centennial Avenue and Victoria Road. Commuters will also be allowed to use transit lanes in a bid to ease the expected congestion.

Despite the diversions, the RTA has warned motorists to expect lengthy delays this morning.

Yesterday, traffic was diverted from Epping Road and Longueville Road to Centennial Avenue and Mowbray Road, but the effects were felt across the city, including on the Anzac Bridge.

A spokesman for the RTA, Ken Boys, said Epping Road was partrially opened about 6am - four hours after the collapse was reported - but it did not take long for traffic flow to slow and become a crawl.

"The westbound lanes [of Epping Road] remain open but what happens in a case like this, when you lose a road as big in the system as Epping Road, is the knock-on effect right round is pretty amazing," Mr Boys said.

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