Bathers may have been unknowingly swimming for hours in water polluted with raw sewage after officials and a contractor delayed notifying beach managers of problems at Pillar Point sewage treatment works on Monday.
Under the emergency response plan for the plant, the Leisure and Cultural Services Department, which oversees the city's beaches, should be informed by the contractor within an hour of any sewage discharge. But the first sewage was discharged at 3.30pm and the department was not informed until 6.30pm, a Drainage Services Department official said.
Another government department that should be informed within an hour said yesterday it had still not been notified.
The news emerged yesterday as the 14 beaches in Tuen Mun and Tsuen Wan districts that were closed at about 10pm on Monday night finally reopened. Many swimmers had ignored the beach closure notices and warnings from lifeguards as they swam as usual on Tuesday.
Anthony Tsang Kwok-leung, chief engineer of the Drainage Services Department's harbour area treatment scheme, denied there was any cover-up but acknowledged there was room to "further improve notifications".
Drainage officials have ordered the plant contractor - which was responsible for construction and design as well as the plant's operation - to produce a report on what they called an "extremely rare" incident involving failure of all three silt-screening units and a back-up.
According to the emergency response plan listed in the environmental monitoring and audit documents for the treatment works, the operators must inform the Drainage Services Department, Environmental Protection Department, Water Supplies Department, and Leisure and Cultural Services Department within an hour of a discharge being discovered.
The Water Supplies Department said yesterday that it had still not had official notification of any leak.
Tsang said the environment department was told at 3.30pm and again at 6pm. This was confirmed by the department.
The leisure department was then told. But it took almost four hours to make a public announcement, at around 10pm, Tsang said. The department did not confirm this last night.
The contractor, a joint venture of ATAL-Degremont-China State, would not comment until its investigation was over.
An environment department spokesman said it was investigating whether the contractor had followed the response plan.
Lawmaker Cyd Ho Sau-lan, chairwoman of the Legislative Council's environment panel, said: "It was too late to close the beaches if people were swimming in the water for that many hours. It is always better to overestimate the threat if public health is at stake."