During a severe rainstorm on 30 March, a section of partly completed tunnel connecting Tsat Sing Kong and Tai Kong Po in Yuen Long was flooded after soil and debris blocked the surface drains. This damaged the TBM, which now requires substantial repairs, including replacement of its electronic components. An investigation is looking into whether to repair the TBM or to excavate the remaining tunnel by other means. Either way, construction of that part of the project would be prolonged by nine months.
There are two other locations of concern, according to MTR. At the site of the West Kowloon Terminus at the Hong Kong end of the underground link, the rock strata is higher than expected, requiring more time to excavate. Progress has also been hindered by boulders and uncharted utilities.
The second critical challenge involves complex geology at the cross-boundary section of the tunnels. This passes under protected wetlands and marble caverns are known to be present, so boring has to proceed with extreme care.
"The Express Rail Link project is a very large undertaking and immensely complex", said projects director Chew Tai-chong. "Since construction began, we have been presented with numerous challenges which have put pressure on our schedule. We have been very focused on catching up through fine-tuning designs and adjusting the construction works but this latest situation with the TBM makes it clear that completion of the project by 2015 is not achievable."
