SINGAPORE - A total of 128 contractors were prosecuted and fined in the first 11 months of the year for carrying out construction works that affected the public drainage system.

The contractors were convicted of 203 offences in making unauthorised alterations and interference to the public drainage system or flouting regulations on earth control measures, national water agency PUB said in a statement on Thursday (Dec 27).

The agency said that it uncovered these offences during regular inspections of construction sites and investigations arising from public feedback.

"PUB takes a serious view of construction works that affect our public drainage system, as it may cause flash floods and impact water quality in our catchment and waterways," the statement added.

PUB's director of catchment and waterways Yeo Keng Soon said that silty discharge and unauthorised interference with drains and canals may result in the accumulation of sediment and affect drainage capacity.

So, it is important for the construction industry to maintain high standards in its earth control measures and operations to protect Singapore's public drainage system, he added.

"They need to do their part and ensure that our waterways are always kept clean and free flowing," Mr Yeo said.

Some of the common offences are having inadequate treatment capacity, inadequate holding pond capacity, and the lack of cut-off drains that separate clean water from silty water.

These lapses would result in silty water overflowing from the construction sites to nearby waterways during heavy rainfall.

PUB said that contractors who are found guilty of repeat offences will face punitive measures, such as tightened screening of their drainage and earth control measure plans and more frequent inspection of their sites.