OPENING OF TIDAL GATES AT KRANJI RIVER AND RESERVOIR

Assoc. Prof. Chin Tet Yung asked the Minister for the Environment (a) what measures are in place to warn the public about the opening of tidal gates at the Kranji River and Reservoir and (b) whether there are any other areas in Singapore where there are similar situations.

The Minister for the Environment (Mr Lim Swee Say): Mr Speaker, Sir, PUB has put in place the following safety operating procedures at Kranji to warn the public on the opening of the tidal gates:

(i) A siren is sounded for two minutes to warn the public on the opening of the tidal gates.

(ii) A visual check is done to ensure that the channel outside the gates is clear of human activities before operating the gates.

(iii) Both sides of the channel are guarded by high fencing, running for about 80 metres downstream. (iv) Signboards are placed in the park area to warn the public of the potential danger of rapid water flows in the channel in the event that the tidal gates are lifted.

Prof. Chin asked whether there are any other areas in Singapore where there are similar situations. Sir, PUB has tidal gates at four other locations. These are: Lower Seletar Reservoir, Poyan Reservoir, Pandan Canal and Jurong Lake. Safety operating procedures similar to those in Kranji are also observed in these four locations.

Sir, Members may wonder how effective these safety measures have been. These procedures have been in place for 27 years. There has not been any accident or mishap being linked to the operations of the tidal gates.

As for the recent incident on 14th April 2002, I am aware that there has been some speculation, as reported in our local media, that the incident might have been caused by the operations of the tidal gates. So far, PUB has not found any technical evidence suggesting that this may be the case.

Sir, the incident is now under police investigation. While awaiting for the outcome of the police investigation, the PUB has introduced two extra safety measures to address public concern. These are:

(a) Converting the signboards in the park area into four languages, and

(b) PUB staff using a loud-hailer to warn the public to stay clear of the water channel before opening the tidal gates. This is a temporary measure. We will review the need to continue with this measure as well as the need to introduce further measures pending the outcome of police investigation.

Assoc. Prof. Chin Tet Yung (Sembawang): Sir, may I ask the Minister whether the need for all these safety measures does suggest that there are certain dangers involved in the opening of these tidal gates? Could he perhaps elaborate what these dangers are likely to be and whether there will indeed be a proper inquiry into the extra measures, if possible, rather than waiting for the police investigation because I am not sure what the police will come up with? But surely, he has experts in the Ministry who can perhaps do the function better.

Mr Lim Swee Say: Sir, Prof. Chin asked two questions: firstly, what are the likely dangers involved with the opening of the tidal gates? Sir, to be more specific, I will explain using the Kranji tidal gates. For the Kranji tidal gates, there are two types of operations. The first type is when the water level in the reservoir reaches a certain level. To prevent any upstream flooding or overflow of the reservoir, the floodgate will be lowered from the top, ie, the flag gates are declined, so that the water in the reservoir can overflow into the channel. For this kind of operation, the lowering of the flag gates, the danger area is actually very small. It covers only the first 40 metres of the channel. In fact, this is the reason why the first 80 metres of the channel is guarded by this high fencing so that nobody could get access to the first 80 metres of the channel. In other words, the lowering of the flag gates is a fairly safe operation and the danger area involves only the first 40 metres in the channel.

Prof. Chin and the other Members may wonder: if that is the case, why have these signboards to warn the public of the danger of rapid flow? Sir, there is another type of floodgate operation, which is, if the lowering of the flag gate is not enough to contain the rising water level in the reservoir, then in extreme situations, we may have no choice but to lift the floodgate entirely. This vertical lifting of the floodgate will cause the water in the reservoir to rush through the floodgate from the bottom. Obviously, the speed of the flow in the channel will be much higher. In other words, in operating a floodgate, PUB does look at the two different types of operations. In the case of lowering the flag gate, PUB staff will ensure that the immediate area outside of the floodgate is cleared of human activities. On the day of the incident, that was indeed the case where the flag gate was lowered but there was no requirement on that day to lift the floodgate. In other words, the danger posed by the lifting of the floodgate did not happen on that day.

Secondly, Prof. Chin asked whether there would be a proper inquiry conducted to look into the incident. Sir, the main responsibility of PUB is to make a technical assessment on the potential impact of the tidal gate operation on the water surrounding the area. As regards investigating the cause of the incident, this comes under the police under the Ministry of Home Affairs. We will leave MHA to complete its investigations.

Mr Tan Soo Khoon (East Coast): Sir, why is the PUB dumping water into the sea? Is there not a way where we could channel this excess water into some other reservoirs directly to save the water?

Mr Lim Swee Say: Mr Speaker, Sir, Mr Tan raised a very interesting point. Today, in Singapore, our daily water consumption is about 300 million gallons. To make sure that there is enough water stored in the reservoirs in case of drought and so on, we have created as much reservoir capacity as we can. At this moment, the water storage capacity in our reservoirs is about 100 times our daily consumption - 300 million gallons multiply by 100 times will give us about three thousand million gallons of reservoir capacity.

PUB's strategy is to manage our water supply and consumption in such a way that, as far as possible, we would like to keep the water level in the reservoirs as high as possible. In case we run into a situation of shortage in water supply due to drought season, these reservoirs will be able to serve as a buffer. The water level in the reservoirs now is about 90%. During a heavy downpour, we will have to let go some of this water.

I would like to assure Mr Tan and Members here that we are certainly not wasting all our rain water.

On the day of the incident, from 5 pm to 5.30 pm, the opening of the floodgate released about 17 million gallons of excess rainwater. But during the same half an hour period, we managed to capture about 51 million gallons. In other words, three-quarters of the downpour were captured and retained in the reservoir. The other one-quarter, unfortunately, has to flow away because the water level in the reservoir has already reached 90% which is the safety limit. However, Mr Tan may be happy to learn that we are now embarking on a programme to link up all the reservoirs. This is to ensure that in a situation whereby some reservoirs may have reached 90% while there is still spare capacity in the other reservoirs, we will be able, through this reservoir integration scheme, to minimise and reduce the need to lower the floodgate at times of a heavy downpour.

Assoc. Prof. Chin Tet Yung: The Minister just now mentioned that there are four other areas with similar gates. Is his Ministry likely to conduct a survey as to whether these areas will also pose likely dangers to members of the public? Would it be better to make sure that no members of the public use the areas near the floodgate at all to avoid such incidents?

Mr Lim Swee Say: Mr Speaker, Sir, as I mentioned earlier, the same safety operating procedures do apply at all the four locations. Further to that, the PUB has looked at the other four areas and concluded that the only area at this moment where there is mud flat and visitors is at the Lower Seletar Reservoir. PUB is going ahead to change the warning sign there into four languages as well.