Hong Kong’s Highways Department admitted late on Tuesday that there had been problems with flooding and smoke in power supply rooms of the immigration building for the Hong Kong-Zhuhai-Macau bridge but said they had been fixed. Its assurances came after video footage emerged on Monday showing serious water leaks in a basement inside the passenger clearance building – built on an artificial island – on the Hong Kong side of the multibillion-dollar mega bridge, including the transformer and switch rooms. The clips were reportedly filmed between February and June, with images showing black smoke coming from a pillar box in the switch room taken in late June. Experts said a design flaw in the power supply rooms in the basement was potentially deadly as it was prone to water seepage that could cause short circuits and the equipment to explode. In a statement, the department admitted its resident site staff and the contractor had discovered leaks in the building early this year and had “swiftly followed up the issue and arranged rectification works”. It attached photos showing the plant rooms as being clean and dry. Design flaws in mega bridge building could be deadly, experts warn Some underground ducts had not been sealed after cables were installed which led to the leakage of rainwater on April 15, the department added. The HK$8.4 billion (US$1.1 billion) building contract was undertaken by a joint venture between Leighton Contractors (Asia) and Chun Wo Development Holdings. Leighton has recently been embroiled in a series of construction scandals involving the HK$97.1 billion Sha Tin-Central link, Hong Kong’s costliest rail project. The department said the contractor had fixed the problem by properly sealing the ducts. “After recent rainstorms, including the amber rainstorm [on Monday], the department has not observed any noticeable water leakage during site inspections at the basement of the building.” It insisted that placing the plant room in the basement was “a reasonable arrangement” as it also housed a cooling system for the bridge’s Hong Kong Port, which supplied chilled seawater via underground conduits to air conditioning systems to achieve energy-saving objectives. On the pillar box emitting smoke, the department said the incident occurred on June 20 from the air conditioning system during testing and commissioning. “The incident was believed to have been caused by the malfunctioning of a component, leading to equipment overheating and subsequently smoke emission,” it added. The contractor fixed the problem and the system was working normally, the department continued, adding that the smoke had nothing to do with the earlier water leakage incident. It said the building was undergoing testing and commissioning, and that the “works would only pass the acceptance procedures if quality meets the required standards”. The government has spent nearly HK$120 billion on the local section of the bridge, which has been hit by construction delays and cost overruns. The bridge is expected to open sometime this year but so far the central government has not announced a date.