Llyn y Parc
North Wales • 12/12/2023
All projects
Llyn Bran Discontinuance Scheme
Project background
Llyn Bran, once a natural lake, was raised in 1899 by a concrete dam to provide water to the North Wales Hospital in Denbigh. The hospital closed in 1995 and Llyn Bran became redundant for provision of drinking water. Llyn Bran was identified as a compensatory site for loss of habitat resulting from another Welsh Water scheme.
Date
2023
Worth
£1.1m
Pre Construction
With no formal access track to the dam, and the surrounding land being designated as Annex 1 Habitat due to the presence of peat, access was one of the main challenges. With 140 peat depths probes taken along the route of the proposed access track, and working closely with NRW, a methodology was developed for installing over 280m of bogmats to the dam without the need to excavate and remove the top layer of peat. This minimised the potential damage to the peat and made site reinstatement far easier.
Construction
Create temporary construction access using bog mats & draw down the reservoir by means of siphon pipes and pumps. Remove silt from the area immediately upstream of the dam before demolishing the dam and removing arisings. Restore the watercourse channel, incorporating silt management measures & create new water vole habitat along the shore using coir matting. Demolish outbuildings and associated structures and dispose off-site. Seal & fill buried pipework. Install new roadside fencing & rip-rap protection around the upstream end of the B4501 culvert.
Post Construction
The discontinuance will give significant biodiversity opportunities in relation to the marginal areas around the retained natural lake and with the restored connectivity to the watercourse. The retained lake will also be used as a receptor site for aquatic plants translocated from Llyn Anafon.
With no formal access track to the dam, and the surrounding land being designated as Annex 1 Habitat due to the presence of peat, access was one of the main challenges. With 140 peat depths probes taken along the route of the proposed access track, and working closely with NRW, a methodology was developed for installing over 280m of bogmats to the dam without the need to excavate and remove the top layer of peat. This minimised the potential damage to the peat and made site reinstatement far easier.
Create temporary construction access using bog mats & draw down the reservoir by means of siphon pipes and pumps. Remove silt from the area immediately upstream of the dam before demolishing the dam and removing arisings. Restore the watercourse channel, incorporating silt management measures & create new water vole habitat along the shore using coir matting. Demolish outbuildings and associated structures and dispose off-site. Seal & fill buried pipework. Install new roadside fencing & rip-rap protection around the upstream end of the B4501 culvert.
The discontinuance will give significant biodiversity opportunities in relation to the marginal areas around the retained natural lake and with the restored connectivity to the watercourse. The retained lake will also be used as a receptor site for aquatic plants translocated from Llyn Anafon.
About the client
Dŵr Cymru Welsh Water is a not-for-profit utility company. The company manages an extensive network, including over 26,500 km of water mains, more than 36,000 km of sewers, and 92 reservoirs. It delivers approximately 800 million litres of drinking water daily and operates nearly 830 wastewater treatment works.
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