Cracks in a cofferdam have caused flooding, tilted structures and a sinkhole at the construction site of Hong Kong’s West Kowloon Cultural District, a “serious” problem that could add more uncertainty to a multibillion-dollar project plagued by cost overruns and controversy . Photos taken on Thursday showed evidence of leakage from the cracks and signs of subsidence on the building site that sits on land reclaimed from Victoria Harbour. Several cargo containers and buildings leaned at awkward angles and there was a sinkhole 25 metres wide. A cofferdam is a watertight enclosure that allows builders to work below the waterline. The West Kowloon Cultural District Authority , which manages the site, said it was aware of flooding at the construction site of the Lyric Theatre Complex, as well as a large basement area linking several planned performing venues. An authority statement said: “A pipe-pile cofferdam wall sprang a leak at the southeast corner in the early morning of July 25, 2019, leading to flooding to a depth of 1½ to 2 metres into the excavated site. “As a result of this breach to the cofferdam, a shallow sinkhole of around 25 metres in diameter emerged adjacent to the site within the project area.” The group said immediate action was taken by the contractor, Gammon Construction , early Thursday and the leak stopped at around 9.30am. The authority said it had alerted the authorities, including the Buildings Department and the situation was being monitored. The Buildings Department said its officers found the sinking and the flooding in a regular inspection to the construction site on Thursday morning. The department said it did not find any structural safety issues. The department has asked the project’s contractor to submit a report on the sinking and continue to monitor the safety of nearby buildings. It said it had not received any reports of land sinking at the site before the regular Thursday’s inspection. The authority said there were no safety issues or injuries and that construction work in other areas had not been affected. Gammon Construction said it would closely monitor the situation and ensure construction safety. Police said they received a call at 12.35pm on Thursday, reporting signs of land sinking and cracking at a construction site in the cultural district. Ngai Hok-yan, a geotechnical engineer, said the condition was serious, judging from the size of the sinkhole. He said he believed the leakage was caused by deficient welding the cofferdam wall. “It is possible that there were some problems with the construction work and [the wall] was not strong enough,” Ngai said. “Pressure from soil and water led to cracks [in the wall] and so soil and water could come in.” But he said the supporting structure at the flooded site appeared to have remained intact and there should be no problems with the design. “The most pressing issue now is to strengthen areas where there were collapses and fill the sinkhole with concrete,” he said. Construction of the 40-hectare West Kowloon Cultural District started in 2013 with an initial grant of HK$21.6 billion. The plan was to turn a prime piece of harbourfront land into a world-class cultural district, featuring art facilities such as theatres and museums. Critics estimated the total cost of the project would exceed more than HK$70 billion. Among many cost overruns, it emerged in January that taxpayers would need to cough up another $17.5 billion for a huge basement complex. In August 2018, the authority fired the main contractor on the M+ visual culture museum following a protracted financial settlement controversy. Civic Party lawmaker Tanya Chan, a member of a Legislative Council’s committee that monitored the project, described the incident as “very rare and shocking”. She said leakage problems had been reported on the same construction site in September, and questioned whether the authority had rectified the issues. Democratic Party lawmaker Helena Wong Pik-wan, who represents the Kowloon West constituency, met with officers from the authority to discuss the situation. “They [said they] need three to four days to fill the sink hole, repair the dam and reinforce it with metal board,” said Wong. She said she has been told that the construction company would build a 800mm-thick permanent dam to prevent similar problems. Ann Chiang Lai-wan, a pro-establishment lawmaker who also represents the Kowloon West constituency, said she would ask those responsible to explain the situation to the public, especially residents of nearby areas who had expressed concern the problems would spread.