Diggers rip up roadway on the intersection of George, Bridge and Grosvenor streets in Sydney's CBD on Saturday. Credit:Dominic Lorrimer The ripping up of roadway less than a week after it has been laid will seem odd to many Sydneysiders but is needed to ensure east-west traffic flow is maintained in the city on weekdays. The intersection is one of the busiest in the CBD, and most complex for workers on the light rail. The area is too large to simply lay steel plates for vehicles to drive over on weekdays. Last weekend, construction crews took it in turns to ensure work was continuous for 56 hours. Glenn Bentley, the chief executive of the light rail project consortium ALTRAC, said the work on the intersection highlighted the complexity of building the light rail line along the spine of Australia's busiest CBD.

Workers prepare the road surface on Sunday for resealing at the busy intersection on George Street. Credit:James Alcock "It is one of the most complex intersections we have on the project and it's also one of the longest," he said. "We always knew it was going to be complex and delicate. This is probably one of the most important phases – clearing the way so we can put down the slabs for the light rail line." While boasting one of the "most comprehensive mapping of utilities anywhere", the project team is still discovering a large number of unexpected ducts and cables, and other redundant pieces of infrastructure such as rail sleepers under the road. The tram line along George Street was decommissioned in the 1960s.

So far, more than 250 unknown utility services have been found. Gas mains, water pipes, fibre-optic telecommunication cables and high-voltage electrical wires create a spider's web of utilities beneath the light rail route. The first weekends over the next five months will involve mapping and excavating the area, and removing items such as rail sleepers before major work on underground utilities can begin.

"There is a predetermined time [on the Sundays] when we say this is the time we have to stop and start the back filling [for the laying of the asphalt and painting of road markings]," Mr Bentley said. One of the biggest jobs will be work on five major banks of utility ducts, which will be boosted to ensure the area does not have to be dug up when the light rail is operating from 2019. By mid-July, the area under construction will stretch from Circular Quay to Liverpool Street at the southern end of the CBD. Work crews are expected to be working in 19 of the 31 zones along the entire route of the line by the end of the year. Another complex part of the project – building the line through the inner city suburb of Surry Hills – will begin in August. It will be challenging because of the narrow nature of Devonshire Street along which trams will run.

At the end of July, traffic will also begin to use a temporary six-lane detour on Anzac Parade to allow for the construction of a tunnel for the tram line. "As we expected, building light rail down one of the oldest streets in Australia's biggest city has presented some challenges, and will continue to do so throughout construction, but Transport for NSW remains satisfied with ALTRAC's progress given this challenging environment," a Transport for NSW spokesman said. Transport for NSW and the light rail consortium had investigated the feasibility of laying grass between tram tracks. However, Mr Bentley said they had decided against laying grass on sections closer to Moore Park, Randwick and Kensington because of the maintenance required and the fact that it could not withstand large volumes of traffic. Laying grass between the tracks in the CBD was not regarded as practical because of the shadows from tall buildings.

Loading Construction of the 12-kilometre line from the CBD to Randwick and Kensington in the city's south-east has been controversial because of the felling of a large number of trees, notably some Morton Bay figs along Anzac Parade. Transport for NSW said the project's design standards required clearance of tree branches of 2.5 metres and tree trunks of 2m from overhead wires and the area the vehicles will occupy when they run along the line.