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WQ.29/2023
WRITTEN QUESTION TO THE MINISTER FOR INFRASTRUCTURE BY DEPUTY C.D . CURTIS OF ST. HELIER CENTRAL
QUESTION SUBMITTED ON MONDAY 30th JANUARY 2023 ANSWER TO BE TABLED ON MONDAY 6th FEBRUARY 2023
Question
“In relation to the recent floodings, will the Minister advise –
- whether he is satisfied that the existing public drainage system is sufficient to prevent flooding in wet weather; and
- whether surface water is getting mixed with sewage in many parts of the Island, and, if so, is this due to damaged pipes?”
Answer
- I am satisfied that the existing public drainage system is sufficient to prevent flooding in wet weather, however the drainage system is not sufficient to cope with extreme wet weather, which due to climate change is likely to happen more frequently in the future.
The public surface water drainage systems did reach full capacity in certain areas during the recent flooding on 17 January. The current focus is on Grands Vaux and working closely with Jersey Water investigating means to attenuate the flows to reduce the risk of flooding to residents. IHE are also collecting data from installed flow monitors on all significant catchments. This data will be used by modellers to determine key flood risk areas for the Island where we may need to invest in further flood defences. This study will inform future business cases to fund required infrastructure investment for the island in order to become more resilient to future climate change related rainfall events.
- During the extreme rainfall events of 17 January surface water did enter a number of foul sewers causing them to become overloaded and spill to surrounding water courses. Whilst some of the ingress will be from faults in the sewer network the predominant ingress will be from the town combined sewer network and in rural areas down to illegal ingress into the system by private properties connecting their surface water systems into the foul network. Most of the time this is done inadvertently, however as surface water flows are significantly greater than foul sewer flows the foul sewers easily become inundated. IHE undertake annual private property investigations targeting catchments identifying surface water connections to the foul network. To remedy this situation IHE work with property owners to segregate and dispose of their surface water in the correct manner. IHE also carry out annual sewer repairs to the network to repair defects. Unfortunately, these overflows will occur in extreme events, this will be the same for recent flood events in the Uk and New Zealand.