More regular checks at work sites to prevent silty water discharge ahead of monsoon season
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Silty water is temporarily stored in a holding pond before it is channelled to the silty water treatment plant.
ST PHOTO: GIN TAY
SINGAPORE – As part of efforts to prevent floods, national water agency PUB is increasing the frequency of inspections at construction sites to ensure they employ measures to prevent silty discharge from flowing into waterways.
This comes ahead of the north-east monsoon, which runs from December to March and typically brings more frequent and intense rainfall.
Rainwater mixed with exposed earth materials and soil creates silty water, PUB said on Nov 8.
“If it’s discharged without treatment, it will lead to silt accumulation over time and reduce the conveyance capacity of waterways. This could increase the risk of flood during heavy rain,” said senior principal engineer Gao Ruoming of PUB’s catchment and waterways department.
Ms Gao urged construction sites to comply with earth control measures (ECM) and adopt best practices to minimise the risk of silty discharge in the light of the upcoming north-east monsoon.
Under PUB’s code of practice on surface water drainage, contractors are required to plan and implement adequate measures to contain and treat silty water before it is discharged into public drains.
Such measures include the use of drains to collect and channel the discharge from the site, and treatment plants that use flocculants and polymers to separate the silt from the water. The chemicals clump suspended particles together so that they can be removed more easily.
Additionally, all construction sites measuring 0.2ha or larger must install CCTV cameras as part of a system to monitor the treated water which is discharged into public drains.
The visual feed from these cameras is analysed in real time, and if silty discharge is detected, automatic alerts will be sent to the project manager, earth control measures officer and other relevant parties.
PUB encourages the installation of treatment systems with a feature that stops operations once the total suspended solids in the treated water discharge exceeds 50 milligrams per litre.
PUB also encourages the installation of treatment systems with a feature that stops operations once the total suspended solids in the treated water discharge exceeds 50mg a litre. This reduces the need for manpower to monitor the outflow and helps prevent silty discharge.
The agency added that it continually reviews the available technologies and will incorporate them as part of ECM requirements where applicable.
Such measures are especially necessary as two-thirds of Singapore’s land area is made up of water catchment areas, PUB noted.
Before undertaking works such as excavation, firms must also engage a qualified erosion control professional to design a comprehensive plan for the measures, to be approved by PUB.
The professional is an engineer registered under the Institution of Engineers, Singapore (IES).
PUB can impose financial penalties and stop work orders on errant contractors, who are liable for prosecution under the Sewerage and Drainage Act and may be fined up to $50,000.
“In the past three years, PUB has taken enforcement action against 226 contractors – of which around half are repeat offenders – for failing to comply with ECM requirements,” the agency said.
The offenders include Trust-Build Engineering and Construction, which was appointed by the Education Ministry to carry out works for Pioneer Primary School’s future site in Tengah.
In late 2023, the Singapore firm was found to have commenced earthworks without obtaining the necessary approvals from PUB, and subsequently in January 2024 failed to comply with ECM requirements to monitor the treatment process. It was fined $17,000 for these offences.
The public can report sightings of silty discharge in drains and canals to PUB’s 24-hour call centre on 1800-CALL-PUB (1800-2255-782), together with details of the location, as well as photos and videos.
Treated water is subsequently discharged into public drains, while the residual sludge will be dried and disposed.
Meanwhile, three projects received the inaugural ECM Project Award on Nov 8, presented by IES and the Association of Consulting Engineers Singapore, in recognition of their “exceptional ECM standards”.
One of them is a Housing Board project in Kallang Airport Drive built by Welltech Construction.
The other two winners were Land Transport Authority projects on the upcoming Cross Island MRT Line. They are the upcoming Riviera interchange station and its tunnels, built by a joint venture between Taisei Corporation and China State Construction Engineering Corporation, and the future Clementi interchange station and its associated works, built by the China Communications Construction Company-Sinohydro joint venture.
Each winner won $2,000 in prize money, in addition to a plaque and a certificate.
The winners were selected from 34 nominations submitted by the construction industry, based on the design, implementation and maintenance of ECMs at their respective work sites. The awards were given out during the annual ECM Night held at HDB Hub.