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STRABAG UK secures contract to deliver essential improvement works at Aldenham Reservoir

13 Mar 2026
STRABAG workers in PPE © John Zammit at Absolute Photography Ltd/STRABAG
© John Zammit at Absolute Photography Ltd/STRABAG

The project includes the replacement of an existing dam embankment and delivery of a reinforced concrete spillway, stilling basin and weir, along with a replacement pedestrian footbridge and a new public access footpath along the crest of the dam.

Located near Elstree within Aldenham Country Park, Aldenham Reservoir is one of the oldest impounding dams in the country, originally constructed in around 1795 to provide water compensation for mill owners following the development of the Grand Union Canal.

Retained by an earth fill embankment approximately nine metres in height and 480 metres in length, the reservoir has a capacity of around 539,000 cubic metres and is an important local amenity for visitors to the surrounding parkland.

While some remedial works have been undertaken previously, further improvements are required to address ongoing concerns regarding the performance of the embankment dam and ensure the long-term structural integrity of the asset, reducing the potential risk of flooding to nearby communities.

Working on the site of the existing reservoir, STRABAG UK will construct a new dam embankment incorporating an 8-metre-deep slurry wall, butyl liner and rock armour to enhance the structural stability and long-term integrity of the reservoir. The project will also deliver a new spillway, stilling basin and weir, along with a replacement pedestrian footbridge and a new public access footpath along the crest of the dam.

The contract will see STRABAG UK undertake a comprehensive programme of surveys, design and construction works over a two-year period commencing in March 2026.

  • We look forward to working closely with Jewel of Hertsmere Limited and our delivery partners to successfully deliver these essential improvement works. This appointment reflects the strength of our collaborative approach and technical expertise, and we are proud to support the restoration of one of the country’s oldest impounding dams for future generations.

    Ian Burford
    Build Subdivision Technical Director at STRABAG UK

  • STRABAG UK come highly recommended to carry out the Dam Repair Works as per the planning permission. We look forward to working collaboratively with the STRABAG team to bring Aldenham Reservoir back to its former glory.