At around 6:00 a.m., just as employees were arriving at their work stations, water was found to be leaking from a manhole on the raw water inlet at a non-hazardous waste treatment and disposal facility. The water shut-off valve was inaccessible as it was located in the leaking manhole. The maintenance manager did not have the information needed to deal with the situation. He called the water utility, which cut off the water supply via an off-site isolation valve at around 8:00 a.m. The leaking manhole was drained. According to the reading on the meter fitted on the outlet, 450 m³ of water had leaked from the facility’s water network. The cut-off in the water supply meant that the facility was deprived of the use of its main fire-suppression equipment.

The leak was caused by a faulty flange connection due to three possibilities:

• the flange had not been adequately fitted onto the pipe;
• the assembly was not supported;
• water hammer on the network.

After the incident, the operator implemented the following corrective measures:

• the isolation valve/valve/meter assembly is now connected to the pipe along its alignment;
• the fitting of the flanges is now checked;
• a system supporting the isolation valve/valve/meter assembly has been fitted to reduce forces exerted on the flanges;
• a file with the numbers to be called and the network map will be compiled and made available to supervisors.