Ruislip Branch Trunk Sewer Diversion

A diversion of the Ruislip Branch Trunk Sewer is needed as it cannot withstand the weight of the new portal structure at West Ruislip due to being over 90 years old. The sewer manhole will also need to be repositioned away from the new HS2 tracks.

Thames Water will be undertaking the work to divert the sewer to the west and this will involve having to take some land within the Ickenham Green Allotments temporarily. The work will involve sinking shafts in the ground and tunneling underground from the Ickenham Green Allotments to Ruislip Golf Course.

The Ruislip Branch Trunk Sewer serves a population of approximately 50,000. It was built in May 1932 and is made of concrete. The sewer is approximately two meters wide and nine meters deep, it flows down into Mogden sewage treatment works.

It flows approximately half full even in dry weather conditions, with a flow of approximately 300 litres/sec during the day. In storm conditions its flows exceed 800 litres/sec. Due to the level of peak flows there is no possibility of diverting the flow in this sewer into another sewer or catchment.

We will be diverting the sewer to the west and this will involve having to take some land within the Ickenham Green Allotments temporarily. Our work will involve sinking shafts in the ground and tunnelling underground from the Ickenham Green Allotments to the Ruislip Golf Course.

We are working to minimise the temporary land take required and we will carry out a full reinstatement of the area once the work is finished.

Our work is due to be completed in 2023 and the existing sewer will be abandoned and filled with concrete.

To access the allotments, we will need to put in a temporary haul road from Ickenham High Road (next to the Soldiers Return) and construct a compound area for the duration of our work. For further details please see the presentation from the last community meeting .

We have submitted a pre-application to London Borough of Hillingdon. We are in the process of discussing our plans with them. We will then submit a full planning application and publicise the application with details of how to comment on the application.

London Borough of Hillingdon will then decide on whether to grant planning permission for the temporary haul road.

We have carried out several environmental studies which include:

A damage impact assessment was also undertaken to ensure that the final design minimises the impact on the environment and local community as much as possible.

We are in continuous engagement with the Environment Agency and permit consents for the proposed works will be submitted.

Our work in the allotments will be planned to keep tree removal to a minimum and the chosen location of the haul road has minimum impact on trees. Several trees near the haul road entrance will need to be removed but we will replace them after construction.

We have produced a frequently asked questions document that will cover answers to the most asked questions about this scheme. To download a copy, please follow the link here .

Please find a link here to the presentation to residents of The Green on Wednesday 14 July 2021.

Please find a link here to the presentation from the last community meeting held in May 2021.

Please also find a link here to the presentation from the community meeting held in March 2021.