Dodgy construction causing flash floods in Singapore – is it worth it?

This year, 128 contractors have been prosecuted and fined by Public Ultilities Board (PUB) for 203 offences involving unauthorised alterations and interference to the public drainage system or flouting Earth Control Measures (ECM) regulations.

In a statement, PUB said that some common offences include inadequate treatment capacity and lack of cut-off drainage to separate silty water from clean water. This results in silty water overflowing into waterways from nearby construction sites during heavy rain.

The PUB discovered these offences during their regular inspection of construction sites and via feedback from the public.

“Silty discharge and unauthorised interference with drains and canals will result in accumulation of sediments and affect drainage capacity,” said Mr Yeo Keng Soon, PUB’s Director of Catchment and Waterways. “This in turn may cause flooding. It is important that the construction industry maintains high standards in its ECM and operations to protect our public drainage system. They need to do their part and ensure that our waterways are always kept clean and free flowing.”

To mitigate these offences, PUB is increasing the frequency of site inspections and tightening the screening of their draining and ECM plans for repeat offenders. Those who continue to offend will also have to pay heavier penalties.

According to PUB, proactive measures have been take to share and encourage best practices about good ECM at construction sites. This includes joint seminars, sharing sessions on erosion and sediment control, providing tools for contractors to use and implement ECM effectively throughout various stages of the construction work.

One of the companies that flouted the Sewerage and Drainage Act this year was Welltech Construction Pte Ltd which was fined $11,200 for discharging silty water into roadside drains on two occasions, November 2017 and Januar 2018. Last year, the same company received four convictions for the same offence.

On their part, PUB said they have contacted repeat offenders to remind them to comply with drainage and ECM regulations. PUB added that 17 contractors identified as repeat offender were given advisory letters to urge them to improve site supervision.

“The contractors are also strongly encouraged to share their drainage and ECM mitigation plans with PUB,” said the statement. It continued, “In light of the Monsoon season, PUB reminds contractors to keep their construction materials and debris clear of the public drain, and carry out regular checks to ensure that drains in the vicinity are free flowing and are not affected by their construction works.”

Now, while it’s great that PUB is being proactive in trying to keep construction companies in line, it seems to be doing very little to dissuade these offending companies from repeatedly flouting regulation.

This year has seen number of flooding incidents around the island. While heavier than usual rainfall is attributed to the increased flooding, construction is also a major factor causing these flash floods as mismanagement of drainage and ECM at construction sites are causing the waterways to clog up.

Early in the year, PUB had noted that they were carrying out drainage improvement works slated to be completed by the first quarter of 2019. Director of PUB’s Catchment and Waterways Department Mr Yeo Keng Soon said, “You can be very sure that when drainage improvement works are completed, the situation will definitely be improved”.

That’s great news, surely. But another concern that should be noted, is Singapore simply building too much? The island is small and land is scarce. Naturally, the more trees and land are cleared out for development, the worse flash floods can get as rainwater just has nowhere to go.

So the drainage system is upgraded to handle a higher volume of water – but what happens when those upgrade aren’t enough anymore?

In the expert report which was produced after the Orchard flooding in 2010 and 2011, the review panel noted:

“URA (Urban Redevelopment Authority)’s Land Use Master Plan is regularly updated and, as such, over the years, the projected run-off coefficient for a specific catchment is also likely to change over time. For example, it was shared that the Stamford Canal was designed for the ultimate run-off coefficient of 0.65 back in the 1980s. As at 2010, the actual weighted run-off coefficient was found to be 0.62. However, based on URA’s Master Plan 2008, this is expected to go up to 0.718.

t is recognised that the Rational Method is only suitable for site-level design of drainage in smaller catchments (in the order of up to 100ha). For larger catchments, there is a tendency for the Rational Method to underestimate the peak runoff, thus resulting in undersized drains.”

Considering that construction is one of the major causes for flash flooding on the island, the question stands: is Singapore simply building too much?