The Parish Council has been in contact with Thames Water to follow up on what is going on with their operation of the foul sewer system in the village. Tankers have been operating at the pumping station in Dry Lane for many weeks causing problems with noise, traffic congestion and damage to the verge.
Thames Water have advised us that the problem in Crawley is due to ground water entering the foul sewer network. The tankers are required because the pumping station cannot cope with the amount of flow – the foul system was not designed to take any surface or ground water so it cannot cope with the volume that is finding its way into the pumping station.
As a solution to the problem, Thames Water arranged for sections of the sewers to be lined. This would stop excess water getting into the sewers and the pumps in the pumping station would then be able to manage without the addition of tankers to take excess foul sewer material away.
The lining process involves inserting a sleeve inside the existing sewer. The sleeve is inserted with what is essentially a heavy duty balloon, the balloon is inflated and this causes the liner to form the shape of the sewer and stop the ingress of water. Once the resin in the sleeve has dried, the balloon is deflated and removed.
However, when TW attempted this work, they found that the pipes were cracking under the internal pressure from the balloon. Ground water has washed away material from around the outside of the pipes which allows the pipes to break.
TW have not had this issue before in any of the locations where they have carried out this type of work. They were forced to stop the lining to prevent a total failure as this would involve an almost impossible task of trying to control the ground water within the excavation and would have meant a long road closure just to fix the one issue.
TW now need to find a different approach to this issue and unfortunately they will need to carry on with the tankering until the levels within the sewer have subsided. We have asked them to limit the tanker operations to daytime as far as possible to minimise the noise and disturbance that is being caused to Crawley residents and they have given us an assurance that they will try to do this.