The Environment Agency has published a document summarising the project and the progress.
From October to December 2020 our project team of engineers and construction experts worked extremely hard to complete the first phase of works as planned. This work included removing damaged concrete from around the weir and placing new sheet piling. During this phase of the repair works we were unable to operate the Jubilee River.
Now that the first phase is complete we are able to safely operate the Jubilee River. The amount of flow we pass down the Jubilee River is determined by the level of flood risk to people and property and the safety of the weir and railway viaduct.
Repairs to Black Potts weir is a worrying situation in the winter months because it prevents use of the Jubilee flood relief river, a situation which was described in this recent Post.
The Environment Agency says:
"We are very mindful that the timing of the work is not ideal. However, we cannot operate the Jubilee River and risk further deterioration to the weir and the railway viaduct until the maintenance work is completed. As we fully understand your worries, the following points to your questions should help clear up your concerns. We will continue to keep you regularly updated on the details of our contingency arrangements and the progress of our work.
Our plans in case of high flows
Our teams continue to monitor forecast flows and levels in the River Thames and Jubilee River.
If high flows are forecast, we will (have to) increase the amount of flow going down the main River Thames through Maidenhead instead of using the Jubilee River as a flood relief channel.
We will also have a separate support team available to help residents should flooding look like a possibility.
We will continue to operate the other elements of the Maidenhead, Windsor & Eton Flood Alleviation Scheme (MWEFAS), such as the existing flood gates at Cookham and supporting pump plan that reduces flood risk to Cookham and north Maidenhead.
During the recent Storm Alex at the beginning of October, we operated these weirs and there were no reported issues.
The existing flood gates, floodwalls, pumps and bunds are all still operational, and if needed we may also use additional temporary measures like removable barriers. As the repair work to Black Potts Weir progresses, we may also be able to increase the use of the Jubilee River, at a reduced capacity as a flood relief channel.
Why this work isn’t taking place in the summer
We regularly monitor the condition of all our assets to ensure that they continue to protect people and property from the risk of flooding. The Cookham and Maidenhead weir complexes are regularly inspected on a routine schedule and are operating normally.
An underwater survey of Black Potts Weir in 2017 indicated that a specific downstream area of the weir was starting to show signs of deterioration in condition and recommended further investigation be carried out following high flows.
Following the high winter flows in 2019-20, a dive survey happened in August 2020. The underwater survey showed the extent of the scour to the downstream area of the weir. We are doing all we can to accelerate the programme for the repair works aiming so that the Jubilee River can be fully operational by the end of the year.
We cannot risk further deterioration and wait any longer, i.e. till summer. If we experience high flows in the coming months the damage to the weir could significantly increase, reducing the control of water velocity downstream and compromising the structure of the Jubilee River and the viaduct in the long term. For this reason, we must act as soon as possible.
The Jubilee River came into operation 18 years ago in 2002. In 2009 did we do some remedial works including increasing the height of the existing flood barrier in Cookham. This is otherwise the first time we have had to maintenance works to ensure it continues to protect 3000+ homes for the next 20 years.
We want as many people as possible to be aware of the work and what it might mean to them. Thank you for communicating the work via your community group newsletter and website. We have already tweeted the same information as we sent to yourselves from our Twitter @EnvAgencySE. We also issued a press release which has already been picked up and published by local media outlets and we have taken part in radio interviews on BBC Radio Berkshire and Greatest Hits Radio.
We are also organising staff visits to the local communities, businesses and stakeholders, we are putting up a signpost in the area to notify the public of the upcoming work and releasing regular media statements and media posts with the ongoing developments.
In the meantime, we recommend that residents stay aware of the risk of flooding by signing up for flood alerts and warnings. For more information visit www.gov.uk/flood or call Floodline on 0345 988 1188. Residents can check river levels in England on www.gov.uk/flood and visit the Met Office website for local weather forecasts at www.metoffice.gov.uk, and make sure they have a flood plan to protect their property and household using the flood advice and evacuation procedures.
Finally, I wanted to thank you for the information about the areas you consider could be affected. Our teams will continue to carefully monitor forecast flows and levels in the River Thames and the Jubilee River. We are also using river modelling to analyse which areas could be most affected at different levels of flooding so that we can decide if additional local flood protection measures are needed. We have a dedicated team of operational staff that will check local watercourses and clear weed screens should flooding be forecast.
We will be in contact again over the next few weeks with an update for how the work is progressing and with further details of our contingency planning for any local flood measures that may be implemented."
Area Director – Thames