In the news: Restoration of the Blenheim Dam
Over the past 6 months a major project has been underway to repair the Blenheim Dam.
The Dam was built in the 1760s by ‘Capability’ Brown and was due for essential repairs under the 1975 Reservoir Act. The Dam was constructed between 1760 and 1774 by Lancelot ‘Capability’ Brown to hold back the waters of the River Glyme and create the centre of his landscape, the Blenheim Lake. The project was completed in October and the Cascade is now fully open to visitors. The work on the dam has created many additional benefits for visitors to Blenheim Palace. A walkway has been created around the dam creating a viewing stand which overlooks the Cascade from above, which is also fully accessible to wheelchair users. Over 36,000 daffodil bulbs have been planted in the area surrounding the dam to ensure the Cascade provides a wonderful attraction and destination point for visitors to enjoy in the spring of 2010.
The completed works of the Blenheim Palace Dam
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BLENHEIM DAM WORKS REQUIRED IN THE INTEREST OF SAFETY RESERVOIR ACT 1975
The Blenheim Dam was constructed between 1760 and 1774 by Lancelot “Capability” Brown to hold back the waters of the River Glyme and create the centre of his landscape, the Blenheim Lake. The Lake covers an area of 45 hectares, is up to 7m deep and holds approximately 570,000cu m of water.
Unfortunately due to the age of the dam and the requirements of the Reservoirs Act we have carried out the repairs and strengthening works to the dam itself. These works are now completed.
The work fell into 2 categories:
1. Essential repairs to the core along the length of the crest of the dam to stop a number of significant leaks.
2. Upgrading and strengthening works as required under the Reservoirs’ Act. The core of the dam is formed from boulders and clay, over the year’s water has gradually found its way through and eroded small pathways through the core. If these are allowed to continue, the pathways will increase in size creating areas of weakness that could ultimately, in a severe flood situation, lead to the failure of the Dam. The Reservoirs Act became statute in 1975 and it is enforced by the Environment Agency. Under its provisions all retained bodies of water are classified A to C, dependant upon the consequence of a major failure. The bodies of water are inspected every 10 years by an engineer appointed by the Institute of Civil Engineers on behalf of the Environment Agency. Depending upon the classification, the dam retaining the water is required to be structurally designed to withstand certain flood events, in the case of the Blenheim Dam, it is a category B body of water and the Act therefore states that the dam must be of a design to hold back the water levels that would result in a 1 in 1,000 year flood and withstand over-topping in a 1 in 10,000 year flood event (to put this in context, 10,000 years ago we were in the ice ages). This may sound an extreme engineering requirement but who is to say that the 1 in 10,000 year flood event won’t happen next week, or next year or in 9,999 years time. Summarised below are the works required:
- Remediate the clay core by digging a 1m wide trench to remove eroded and breached sections of the clay core and back filling with bentonite (a form of clay) slurry.
- Create a new 80m wide spillway on the downstream face of the Blenheim Dam. This will involve the removal of all planting, stripping off the top soil, laying a bed of Armorloc concrete blocks, replacing the top soil and reseeding.
- Reinforcing the sides of the cascades with concrete and limestone boulders.
- Carry out repairs to the “penstock” or underground sluice gates Despite Blenheim Palace and Park being one of the first World Heritage Sites designated in the UK, it is the only one that does not attract any form of public or Heritage Lottery Fund funding, this is due to it effectively being in private ownership. The Estate believes this position is inequitable and is lobbying hard to try change this position but without success to date.
The Palace and Park are generally in good repair and condition as the Duke and Trustees take their roles as custodians of apart of the countries heritage very seriously, however, the current project placed severe strains on the Estates’ ability to continue with its ongoing program of conservation works and maintenance, many of which may now have to be delayed for 3 to 5 years.
Finally, we apologise for any inconvenience caused by the works.
