The government is claiming HK$320,000 from a contractor on the Central-Wan Chai Bypass whom it blames for causing gaps that appeared in the Island Eastern Corridor expressway in January. The contractor did not take enough care in excavation work near the Tin Hau section of the flyover along the northern shoreline of Hong Kong Island, a consultant says after an investigation. A summary of the investigation report, which does not name the contractor, was submitted to the Legislative Council this week, eight months after a media report that supports for the pillar had moved one to two centimetres sideways. 'The contractor was not cautious in monitoring the excavation work. When its workers drilled underneath the bridge, it failed to carefully control the drilling speed and pressure, wearing away the soil under the sea,' the summary said. The Highways Department said it would claim the maintenance costs from the contractor, including the installation of metal supports to fill the gaps between the bridge surface and the pillars. The department said tests before the excavation had found the soil in the reclaimed land was weak and had an increased risk of erosion. The contractor had been told this and should have handled the digging with extra care, it said. Earlier, officials said the 'abnormal movements' of the joints on the bridge were slight and would not cause structural problems. The department has increased monitoring of the bridge's structure from twice a day to every hour. The contractor was digging to build an underground car park for the Food and Environmental Hygiene Department, to replace one above ground that will be demolished to make way for the bypass. Highways officials say the incident did not affect progress on the project, due to be completed by 2017.