MELBOURNE CITYLINK:Tunnel troubles

Motorists loved it because it cut the travel time from the central business district to the near south-eastern suburbs from 30mins to 10mins.

Then at 8.30am Feb 19 near the deepest point of the tunnel – down about 50m (160') – a section of wall cracked, the waterproofing membrane broke and water rushed in. Pumps handled the water and no one was hurt, but the owner Transurban (Transurban City Link Ltd) had to close the tunnel immediately. About 6m (20') of one wall had moved inward, about 30mm to 50mm (1.3" to 2") at the floor level. The tunnel was kept closed for a week while engineers, geologists and other tunnel specialists inspected and consulted on the problem.

At the end of their inquiries they seemed to all agree that there was no danger of this section of wall moving any further and threatening a catastrophic collapse. Wooden wedges were found that should have been removed before shotcreting, suggesting shoddy construction work.

For now the lane alongside the damaged wall is closed off, and repair work is beginning. They hope to schedule major work requiring a full tunnel closure for the early AM hours, Sundays etc.

There is concern of course about other surprises, given the further evidence of mistakes in construction.

The Burnley tunnel was built by the New Austrian tunneling method in which rather simple roadheaders grind out the tunnel in separate layers, and the supporting structure is, hopefully, sized to fit the different conditions as construction proceeds. The tunnel goes underneath the city’s Botanical Gardens, the Yarra River, a sports complex and an inner residential suburb. It was built from each end and also in two directions from an exhaust shaft about midway.

It is one of the longest 3-lane tunnels built by this method. It traverses a variety of ground conditions from solid granite through silt and very varied fractured rock. Parts are quite dry, others very wet. In retrospect it is clear the builders knew far too little about the ground conditions. One official told us the surprise death by heart attack of a senior tunnel engineer early in construction was a setback the project never really recovered from. He was described as the key repository and integrator of tunneling data, but he was not conscientious in keeping records.

The shorter (1.6km or 1mi) Domain Tunnel, also 3-lanes, for westbound traffic was built with no comparable problems, and nearly on-time and on-budget. It was built by the same construction company, a joint venture of the Australian Transfield and Obayashi, the international Japanese builder. The Domain tunnel was built with one shallower mined section using NATM but also used a coffer-dam and poured in place construction under the river Yarra.

Water water

The most serious problems in construction of the Burnley tunnel occurred when the acquifer through which it runs was recharged after initial construction was done. When water pressure was nearly back to normal it lifted several heavy floor slabs and caused cracks in others. A number of the slabs had to be broken up and replaced and others repaired, and some 5,000 extra steel anchors were driven into the rock underneath to anchor floor slabs. Water leakage was well above specifications for a long time and required a large amount of tricky reworking, extra grouting, membrane repair and the like. Most of the mechanical systems already installed had to be removed for the rework, and then re-installed later.

The Burnley tunnel ran over contract time by 8 months. The extra cost cited is $170m, including the cost of lost toll revenue (about $8m/month). The toll road owner Transurban – a traded company – had a fixed price construction contract with the South Link builder Transfield Obayashi Joint Venture, but there are differences over what extra costs are covered by the contract and which are attributable to the owner.

Report candid

Transurban’s annual report is very blunt about its problems and ascribes its difficulties to construction delays plus “inefficient work flow processes in the initial customer service center..., underestimation of the peak levels of customer service demand..., delays in delivery of functionality of the Central Toll Computer System.” It lays how much each of these problems cost shareholders. Toll revenue in the first six months of partial operation ran at an annual rate of $34m (A$=54c) with operating expenses of $60m, concession fees payable to the state of $13m, depreciation $35m and net interest $45m for an overall loss of about $120m.

It said traffic on the Western Link at 210k toll transactions/average weekday was lower than investor prospectus forecasts, due in part to delays in opening the Southern Link. Traffic on the partial Southern Link was just under 140k tolls/day. Since the tolling uses the barrier or point toll principle, many trips involve more than one toll. There are nine toll points in the system, located over mainline lanes, including a spur to the CBD from the south.

Transurban says traffic as of mid-2000 was 87% of forecast on the Western Link and 96% on the partial Southern Link.

In the January 2001, the first month with everything open, toll transactions were 529k/day av weekdays and 473k/all days. Transurban says Western Link transactions still appear to be about 80% of forecast levels but that traffic on the Southern link was already about at forecast levels. Toll revenue for January was $9m. Average toll was 60c. A 10% federal goods and services tax (GST) is levied on every toll.

The company introduced a new ’24 Hour Pass’ and ‘Weekend Pass’ each about $4.00 for unlimited use of the system by motorists without transponders. There are stated limits to the number of such passes than can be obtained per year, but enforcement of such limits has proved difficult. This is due in part to a proliferation of modes for obtaining passes. As well as telephone operators, a website and machines at gas stations handle day passes.

Violations

An apparent huge success of MCL – though not claimed as such by Transurban – is the low violation rate on Melbourne CityLink. This started at 2.1% of vehicles, they report, already a low rate by international standards and by mid-year was down to 0.7%. This is well below the rates achieved on any electronic toll express or dedicated lanes in the US or Canada where 3% to 7% is common and rates over 10% are not unknown especially in early days such as those of MCL. For example the North Texas Tollway system is currently running 7% violations in ungated ET-only and ETX lanes combined.

MCL’s system allows motorists who have driven the system without a transponder until noon the next day to pay by telephone and credit card/bank account debit without being regarded as a violator, so that helps reduce violations numbers a bit. In addition there is very little interstate traffic, Melbourne being far from any border, so they have the advantage of working mostly with a single motor registry list.

The low rate may be in part a product of broader law enforcement. Road rules are in general more sensibly designed and then more energetically enforced in Australia than in America. Urban speed limits are so absurdly low in the US, and central double no-crossing lines and ‘stop’ signs are so promiscuously applied, that all these are routinely disregarded by most motorists. Maybe that encourages the thought that you’ll have a good chance of getting with it, blowing by the toll point? But 0.7% is impressive!

BACKGROUND: Melbourne is the second city of Australia with a metropolitan population of about 3.2m and close to 2m motor vehicles. MCL links up three major radial motorways two of which fell short by several miles of the central business district and forms an L-shape, enclosing the central business district on its western and southern sides. It is the only toll facility in the state of Victoria.

The Western Link involves a 6km (4mi) widening of the airport Tullamarine Freeway (2x2 to 2x4), then construction of 4.4km (3mi) of new 2x3-lane elevated highway(concrete box girder) including the Bolte bridge over the Yarra River to an IC with the Westgate Fwy. This Western Link is a new Gateway to the city – somewhat akin to the great Skyway in Chicago – and has two ICs for connections to city streets and some spectacular efforts at civic sculpture consisting of large angled beams and light effects, and a long oval section tube spanning 6-lanes divided that does double duty as a noise attenuator. (TRnl#36 Feb 99 p14) The Bolte bridge of balanced cantilever concrete box girder design has a pair of towering 140m high pillars of purely artistic value.

Beyond the bridge the existing elevated Westgate Fwy petered out 1.8km (1.2mi) east of the new IC with the Western Link. The second or Southern Link is a 4.5km (3mi) extension eastward to the Southeastern now renamed Monash Freeway. Within that 4.5km are (1) an eastbound 3-lane tunnel 3.4km long driven under inner city parks, the river and the inner suburb of Burnley (Burnley tunnel) and (2) a 1.6km (1mi) 3-lane driven and cut and cover tunnel for westbound traffic under the inner city parks (Domain Tunnel) and a widening of an existing riverbank roadway. Then follows 3km (2mi) of widening (2x2 to 2x3) of the elevated part of the Monash Fwy. Total project cost for 73 lane-km (45 lane-mi) of new construction was budgeted for $1.3b but the Burnley tunnel troubles will put the construction cost up at least $100m.

MCL has a toll system based on open road tolling with no facilities for onsite collection. Most motorists have eletronic toll transponders (called e-TAGs) and those without them have their license plate photographed. They call an ‘800’ number to pay by credit card for a ‘daily pass.’ Those who travel without making some arrangement to pay the toll are classified as violators.

In terms of transponders deployed (about 500k) MCL is by far the largest European CEN-standard electronic toll system in the world using 5.8Ghz backscatter tags manufactured by NEC in a local factory. The system was designed by Translink, a joint venture of Transfield and the French Egis. Equipment is mounted on large gantries over the mainlanes in a ‘barrier’ like arrangement, rather than on the ramps as on Canada’s 407-ETR where trips are computed. The front end of the toll system has worked quite well from the beginning but the central toll computer system was behind and over a third of a year of tolling was lost on opening. (see transurban.com.au, macquarie.com.au)

Dates

5/6/99 W Link due for completion, delayed

8/15/99 Western Link opened to traffic

9/99 Builder reports major problems in Burnley Tunnel

1/3/00 tolling started on Western Link

1/19/00 Southern link due for completion, delayed

4/16/00 Domain tunnel and partial opening of Southern Link