Hardmead Sluice Replacement Project Information Page

Closes 1 Jul 2024

Opened 25 Jun 2021


March 2024 Update

Since January and the storm flows it brought, we have been working to bring the second gate into automatic operation, install the fish pass, build a pumped eel pass and reinstate new surfaces around the site.

The new bridge supporting the drive mechanisms for the two new sluice gates

What we are doing

We are replacing and improving the gate and operating equipment at Hardmead Sluice as the existing one had reached the end of its working life after 45 years of service. A failure of Hardmead Sluice would have resulted in increased flood risk and loss of control of upstream water levels.

During the works, storm flood flows will still flow through the structure to maintain the current level of flood management and the ability to keep upstream water levels for navigation, water supply, amenity and environmental needs.

The previous single sluice gate is being replaced with two smaller gates to give greater flexibility in maintaining them. The existing sluice also acts as a barrier to the free passage of fish and eels. As part of this project new fish and eel passes are being constructed to enable the free passage of fish and eels around the sluice. This will help increase the length of watercourses these species can migrate along. It will also improve the aquatic biodiversity of the watercourses.

The main works started in August 2022 and we expect them to complete in spring 2024.


The waterways in the Lower Lee valley include the River Lee Navigation, Old River Lea, and the Lee Flood Relief Channel (LFRC). The LFRC was built between 1949 and 1977 and is designed to carry flood water to reduce the likelihood of flooding in the Lower Lee valley. A system of weirs, gates and sluices control water levels in the LFRC. These maintain water levels for water supply, navigation, amenity and environmental purposes while allowing flood flows to pass during storm events.

Hardmead Sluice is a major flood control structure within the LFRC and is located at Great Amwell, close to the town of Ware in Hertfordshire. As well as managing flood risk, the sluice assists in sustaining water levels in the River Lee Navigation that also enables flows down the River Lee Amwell Magna Loop from the Tumbling Bay weir.

How will the sluice replacement affect you?

During the main works you may notice additional temporary construction noise during the working week. Construction vehicles will be entering the site from Hollycross Lane via the private access road and across Amwell Bailey Bridge. Public Rights of Way will not be impacted but there will be a minor diversion for pedestrians at the northern extent of the site boundary. Road closures should not be required.

We will need to reinstate parts of the riverside tarmac track between Hardmead Sluice and its junction with the route to Holycross Road. For the safety of the public, while this work is undertaken, we will need to close this part of the track in working hours for a couple of days in early May. We will have signed pedestrian diversions in place, with contractor's marshals in place to advise the public. The pedestrian diversion will be over to the south side of the river by the pedestrian bridges near Tumbling Bay and the track from Holycross Road.

We are planning similar construction works further along the Lee Navigation at Stanstead Sluice in Stanstead Abbotts, though these are likely to start once one new gate at Hardmead Sluice is operating.

Location of Hardmead Sluice

Are you prepared for flooding?

While these works will improve flood defence along the LFRC, it is important to be prepared should the worst happen. Here are some steps you can take to prepare yourself for flooding events:

Sign up to our flood warnings: www.gov.uk/sign-up-for-flood-warnings

If you are visiting the area, sign up to flood warnings or the Met office weather alerts and receive advance warning of potential flood risk: UK weather warnings - Met Office

Prepare a personal flood plan and be assured of what to do if it floods: Personal flood plan - GOV.UK (www.gov.uk)

Thank you for visiting our project information page.

If you would like any further detail about any of the above information please get in touch at PSO-HNL@environment-agency.gov.uk


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