Strabag to repair Aldenham Reservoir: dam safety and design notes for engineers
Reviewed by Tom Sullivan
First reported on The Construction Index
30 Second Briefing
Strabag UK has secured a two-year contract from Jewel of Hertsmere Limited to rebuild the Aldenham Reservoir dam in Hertfordshire, an earth-fill embankment about 9 m high, 480 m long and impounding roughly 539,000 m³. Works include constructing a new embankment with an 8 m deep slurry wall, butyl liner and rock armour to address performance concerns and reduce downstream flood risk. The scheme also delivers a new reinforced concrete spillway, stilling basin and weir, plus a replacement footbridge and crest-top public footpath.
Technical Brief
- Contract spans a two-year programme of surveys, detailed design and construction starting immediately.
- Client is Jewel of Hertsmere Limited, with Strabag UK acting as main design-and-build contractor.
- Aldenham Reservoir, built circa 1795 for Grand Union Canal compensation flows, is now a leisure amenity.
- Previous remedial works were undertaken but judged insufficient to ensure long-term embankment performance and integrity.
- Safety driver is reduction of downstream flood risk to nearby communities from potential dam performance issues.
Our Take
With a 9 m-high, 480 m-long earthfill embankment dating from around 1795, Aldenham Reservoir falls into the cohort of ageing UK dams where recent safety-driven works in our Infrastructure coverage have often uncovered hidden seepage and internal erosion issues, so Strabag UK should plan for potential scope growth once the slurry wall trench is opened.
The specified 8 m-deep slurry wall implies treatment through much of the embankment section rather than just a shallow cutoff, signalling that Jewel of Hertsmere Limited is opting for a more conservative remediation approach that should help satisfy increasingly stringent UK reservoir safety expectations for assets near urban areas such as Elstree in Hertfordshire.
Among the 723 Infrastructure stories in our database, relatively few involve historic canal-linked reservoirs like Aldenham serving both amenity (Aldenham Country Park) and legacy navigation functions (Grand Union Canal), which tends to complicate outage planning and stakeholder management compared with single-purpose flood or water-supply dams.
Prepared by collating external sources, AI-assisted tools, and Geomechanics.io’s proprietary mining database, then reviewed for technical accuracy & edited by our geotechnical team.
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