The Mound is to be closed again to complete work that was postponed to allow Princes Street to reopen in time for last year's winter festivities.
The work is set to take five weeks from 1 May – clashing with the nearby General Assembly for the Church of Scotland – though tram chiefs are confident the chaos which ensued the first time The Mound was shut will not be repeated. Part of Hanover Street will also be closed, with traffic diverted along George Street, North St David Street, Waverley Bridge and Market Street.
TIE today defended the decision to bring in the traffic management measures, but critics said it would cause even more misery for beleaguered drivers.
Raymond Davidson, secretary of the Edinburgh Taxi Association, said: "This is just going to bring even more congestion and it's lasting a month. A lot of people have just got used to The Mound being opened because it was closed for so long, and now they're closing it again.
"From the taxi drivers' point of view, there seems to be no end to it all. Just when you think they're finished, along they come and dig up the road again."
It is understood the work to install new pipes is being carried out near the site of the Crawley Tunnel, which dates from the 1820s. A section of the tunnel was unearthed by contractors at the junction of Princes Street and The Mound last year and is believed to have caused problems ever since.
Constructed from around 1821 onwards, the tunnel carried two main water pipes from the Crawley and Comiston springs to help provide supplies for the expanding New Town.
Long-time tram critic John Carson, a former director of maintenance for Network Rail, said that TIE had been unaware of the tunnel when it first started work in Princes Street, a claim denied by the tram company.
He said: "They came across that tunnel by accident, but it has been there for 200 years. The whole project is just a bit of a shambles."
The Mound reopened to traffic, as did Princes Street, at the start of December, having been closed since February. It has now emerged some work was simply postponed.
A trams spokesman said: "The decision was taken with the interests of local businesses in mind to ensure that our works did not impact upon the city's Christmas shopping experience and Winter Festivals, which we successfully achieved."
MOVING PIPES AND CABLES ADDS TO DELAY
NEWS of the latest roadworks came as tram firm TIE advertised for contractors to carry out utility diversions in north Leith, work that will not be completed until the winter.
Last month tram bosses said that all the work to move underground pipes and cables would be completed by September – already more than a year behind schedule. But the further work to move utilities along 300 metres of Baltic Street is likely to push the timescale back even further.
A spokesman for the tram project said: "A redesign for the Baltic Street utilities programme was undertaken after an unexpectedly high volume of material was found when the works began in early 2009.
"A revised technical solution has now been agreed and a separate tendering and procurement process has now started. These works are planned to take place this summer and will last for around four months."
TIE said last month that a total of 46,575m of utilities had been diverted – 97 per cent of the total amount of work on the first phase of the project.