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Brief project information:

The location:	Llandrindod Wells Lake, Llandrindod, Powys
The project:	To remove 3,500 m3 of silt from the 16 acre lake which had become shallow and eutrophic due to excessive nutrients in the sediment and water. It had also become subject to algae blooms and the lack of oxygen and poor water quality were causing fish and other wildlife to die.
Timescale:	December 2008 - April 2009
PDF:	Download case study - Llandrindod Wells Lake

The location:

Llandrindod Wells Lake is the ‘jewel in the crown’ of Llandrindod. Originally dug out from a peat bog in the 1870s, the 16 acre lake has over the years been the focal point for a variety of activities, including fishing, model boating and pleasure boating. Llandrindod Wells is home to an abundance of wildlife - ducks and swans, fish (carp and bream in particular), frogs, toads and three kinds of newt including the rare and protected great crested.

The project:

For many years, there has been little or no maintenance budget for the lake and a study by Liverpool University in 1992 concluded that sediment could be accumulating at up to 1cm per year. As a result of past agricultural run-off, unregulated waterfowl feeding and the unmanaged fish population, it had steadily become more eutrophic.

By 2006, the excessive nutrients and warm summer temperatures were causing blooms of blue-green algae to appear and creating a public health risk. When the algae die they sink to the bottom of the lake and decomposition consumes some of the oxygen dissolved in the water. Combined with a heavy thunderstorm (when low pressure enables even more oxygen to be lost), a catastrophic oxygen crash caused 1500 kg of fish to die.

Emergency aeration equipment, water recirculation pumps and even the fire brigade were brought in to help re-oxygenate the lake. Although the crisis was dealt with and several valuable carp were rescued, it was clear that the lake was in dire need of a long term restoration solution.

Why Blue Boar?

Cost was a big issue so the solution had to be both viable and cost-effective. It was prohibitively expensive to take the dredged sediment away, so we worked with the Council to redeploy the sediment and create bunds and embankments which could then be vegetated. Once established, the reeds and other native plants would help balance the nutrient levels in the water.

The challenges:

• The great crested newt comes under European protection, so the restoration work had to be licensed by the Welsh Assembly Government and closely overseen by the Lake Park Steering Group, the Radnorshire Wildlife Trust, the Countryside Council for Wales and the Environment Agency.
• The licence ran from October 2008 to March 2009 so we only had a narrow window of time in which to complete the project. We also had to avoid the toad and newt migration and the start of the bird nesting season.

• The newts had to be prevented from entering the works compound so before dredging could start, our team needed to be instructed by the in-house ecologist on procedures should a newt be discovered.

The outcome:

In total, 3,500 m3 of silt has been redeployed around the lake and vegetated and the water quality is showing real improvements. The lake has been made deeper and the leaks have been sealed making it easier to maintain depth all year round. The edges have been re-contoured and the dredged sediment used to form a lagoon, terrestrial bunds and wetland areas.

The lake can now self-regulate to a greater extent avoiding large swings in BOD, dissolved nutrients
and oxygen.

Commercial and Medium sized contracts

In this section

• Bishop’s Palace Wells
• Arrow Valley Lake
• Llandrindod Wells Lake
• Queen’s Park Lake
• Pittville Park