A £1M PROJECT to restore a dam in the grounds of Blenheim Palace has been finished.

Work to the Blenheim Dam – built between 1760 and 1774 by famous designer Lancelot ‘Capability’ Brown – started in May and was completed on Tuesday.

The restoration will ensure the Woodstock palace complies with the Safety Reservoir Act 1975, which is enforced by the Environment Agency.

Roger File, property director at Blenheim Palace, said: “This project has been a challenging undertaking in our aim to balance the requirements of the Reservoir Act while being sympathetic to the ‘Capability’ Brown designed landscape.

“We feel we have achieved this and in addition opened up the area as a destination location to visitors, allowing them to experience previously unseen views.”

The dam holds back the waters of the River Glyme, creating the central piece of the Blenheim Lake.

Repairs were carried out to the crest of the dam to stop several leaks.

The core of the dam is formed from boulders and clay, and over the years water gradually eroded small pathways through.

If left unchecked, the small leaks would have grown and, in severe floods, could have led to the dam bursting.

The leaks were fixed by workmen who dug a 1m trench to remove eroded parts of the clay core, which were then filled with bentonite slurry, a form of clay.

A new 80m wide spillway was also created on the downstream face of the Blenheim Dam.

This involved removing all the plants, stripping the top soil, laying a bed of concrete blocks and replacing the top soil and reseeding.

The second phase saw the sides of the cascades reinforced with concrete and limestone boulders, and repairs made to the underground sluice gates.

The Safety Reservoir Act means all retained bodies of water are classified A to C, depending on the severity of a major failure.

These bodies of water are inspected every ten years by an engineer on behalf of the Environment Agency.

Depending on its classification, the dam retaining the water is required to be structurally designed to withstand certain flood events.

The Blenheim Dam is classed as category B, which means that the dam must be able to hold back the water levels that would result in a one in 1,000 year flood.