Woh Hup and Horti-Flora have become the latest two contractors to be fined for letting muddy water flow out from their construction sites.
At Upper Thomson's Windsor Park, cloudy water from the estate's drainage upgrading project by Horti-Flora ended up filling a clear freshwater stream next to a nature reserve with silt.
Meanwhile, a part of Pasir Ris Drive 3 next to Woh Hup's construction site of the future Overseas Family School was hit by a tea-coloured flood three times last month, leading to traffic jams.
Under Singapore's Sewerage and Drainage Act, contractors who cause silty discharges can be fined up to $5,000 for each offence. Those who fail to comply with notices to shore up their protective measures can be fined up to $50,000. Water agency PUB told The Straits Times Wednesday it would fine the contractors this month after inadequate measures led to public complaints last month.
Miss Chloe Tan, a 24-year-old volunteer with nature group Toddycats, which has been conducting guided nature walks, said she had first noticed silt in the Upper Thomson stream early last month. The stream is home to 12 species of native frogs, including several endangered ones, as well as fish and dragonflies, and siltation would affect these creatures, she said.
At Pasir Ris, resident Oliver Foo, 49, said the flooding occurred thrice in mid-October. Others made the same complaint on social media website Stomp.
The contractors have now taken measures to prevent the silting.
At Pasir Ris, Woh Hup has covered the bare earth with canvases and soil mats made of coconut husks, while at Windsor Park, Horti-Flora has done the same and strengthened a silt fence to prevent silt from flowing into the stream.
Woh Hup also deepened its detention ponds to hold 4,540 cubic metres of water, up from 2,100 cubic metres, adding almost an Olympic swimming pool's worth of capacity.
Last month, the contractor discovered water flowing into the Pasir Ris site from a hilltop further uphill, said project director Ng Yew Hung. This has since been channelled into a side drain, and the flooding has not occurred since, he added.
In the first 10 months of the year, PUB issued 94 fines for causing silty discharge and six fines for failing to comply with its notices to review earth-control measures.
Last year, it issued 153 and four fines respectively.
Mr Quah Hock Lai, its senior assistant director of catchment and waterways, said silt from various sources, including construction and bald spots along road verges, can build up in waterways and stop water from flowing smoothly.
PUB spends $5 million to $6 million each year just dredging canals where silt builds up.
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