Llyn Tegid safety works
What’s the work being undertaken at Llyn Tegid?
The embankments are being strengthened to improve their ability to withstand extreme flood events.
The embankments included in the project run along the lake shore from the Bala Adventure and Watersports Centre, around the Enterprise Park bordering the River Dee as far as its confluence with the Tryweryn. Works include replacing the stone wave protection along the lakeshore and adding a small berm (raising existing ground levels beyond the landward side of the toe of the embankments). Trees, mainly self-seeded ash, growing in the embankments and weakening them will have to be removed. A new retaining wall near Bala Rugby club will enable possible future expansion of the Bala Lake Railway into the town.
A number of environmental and community mitigation and enhancements will also be delivered such as tree and hedgerow planting; re-organising and landscaping the lake foreshore overflow car park and Penllyn leisure centre outside seating area; and making associated footpaths more accessible.
When did the works start on site?
Works have started on site in mid-November 2021 when our contractor setup their main compound into December. During January and February 2022 we’ve completed the removal of self-seeded trees, mostly ash, which are growing in and weakening the lakeshore embankment. We have also removed specific trees along the back of the Dee embankment whilst keeping the public footpath open during this period.
Why is the work necessary?
To ensure Llyn Tegid continues to meet the requirements of the Reservoirs Act 1975 and remains safe in the long term. Llyn Tegid is regulated under the Act which requires regular inspections by qualified reservoir Inspecting Engineers. At inspections in 2014 and 2019 some statutory recommendations were made to which this scheme relates.
Who is doing the work?
The construction work is being undertaken by William Hughes Civil Engineering Ltd, one of our north Wales based framework contractors. The landscape works are being delivered by a landscape contractor, Ground Control. Consultancy firm Binnies are providing specialist design and environmental support and Arcadis are providing supervision services.
When will the work be completed?
The works are expected to be completed by Spring 2023 after which landscape maintenance will continue. Footpath closures will be necessary throughout 2022 including the summer months, to keep the public safe and to ensure we reach this date.
Will the project affect the risk of flooding in Bala?
This project will not increase the risk of flooding in Bala. Furthermore, reservoir safety procedures and careful phasing of the works shall ensure that the safety of the reservoir embankments are upheld at all times, 24hrs per day, during the construction phase.
When works are completed, we are better managing the risk of flooding to Bala in the long term and improving the safety of the embankments. These help provide flood protection to the town in conjunction with the Dee Operating Rules (see How does water regulation work at Llyn Tegid?), which has not flooded since the 1960’s.
Will trees be removed?
Regrettably yes. The works include strengthening the embankments and replacing the lake shore stone wave protection. Throughout January and February 2022, we have removed approximately 290 trees (mainly self-seeded ash) which have established themselves in the embankments, weakening them. We have protected the healthiest and most valuable trees where it is possible to work around them. As part of the works, the first phase of planting in March 2022 we will be planting more trees than we remove as part of our mitigation and enhancement plans at a ratio of approximately 3:1.
How much disruption can we expect?
Due to the major engineering works, sections of footpaths will remain temporarily closed to keep the public safe throughout 2022. Alternative footpaths have been clearly waymarked. There will also be construction traffic related to the works and some of the operations could involve noisy activities. The contractor’s compound has been established in the community helping to control movements. One-way traffic management will be situated along Tegid Street during the summer months.
Construction is being managed to minimise disruption to the local community. Where possible, work is being phased and affected stakeholders are being updated in advance. The Contractor is responsible for securing their sites at all times including weekends and this will mean fencing and contractors vehicles may be visible and may temporarily affect the natural visual aesthetics of the area.
How are you considering the exceptional environmental quality of the lake and its surroundings?
Llyn Tegid is situated in the Snowdonia National Park and the embankments are within environmentally sensitive areas of international importance. Sympathetic solutions have been developed that aim to enhance the environment in line with the requirements under the Environment (Wales) Act 2016 and Well-being of Future Generations (Wales) Act 2015. During the works, we will continue to work closely with Snowdonia National Park Authority, our own natural resources team responsible for the protected sites affected, and other key stakeholders to ensure that the works are delivered in an appropriate manner, minimising impact on the community and the environment.
What about the impact on people’s recreational use of the lake and shore?
The majority of recreational use of the lake is unlikely to be affected during the works. Annual sporting events hosted by the town, such as Bala Big Bash will be able to continue throughout the construction window. We will continue to work closely with the organisers to ensure that suitable arrangements are made. There will be disruption to sections of footpaths which will be temporarily diverted and the length of diversion minimised as far as possible. Footpaths will be fully restored to their current or better condition following construction. We are also proposing improvements to gradients and barriers along lake shore footpaths which will improve access for people of all-abilities.
What about the impact on tourism?
The works are required to ensure the embankments continue to withstand extreme flood events. The works will be managed sensitively to minimise any potential impacts on tourism such as the contractors being prevented from using the High Street for haulage deliveries. We will continue to work closely with the local community and key stakeholders to ensure everyone’s views are heard and the scheme is delivered in a sensitive way.
In the long term, we hope the scheme will have a positive impact on tourism and the local economy. Maintaining the access along the lake shore and its magnificent views have been a key consideration during design development.
How have you listened to our views?
Summarised feedback from our pre-planning application consultation, our previous drop-in events in July 2018 and December 2019 and discussions since with local groups and individuals. These have included:
- The importance of local community engagement in developing the mitigation and enhancement plans associated with the scheme.
- The desire to retain some mature trees within the proposals where possible.
- Concern over construction impact on Bala over summer and effect on local traffic.
- The potential to improve existing public rights of way.
- The opportunity to establish wildflower areas along the Dee and Tryweryn
Following planning submission in November 2021 and positive determination in May 2021, we have continued to work closely with key stakeholders to address these points. These have included Bala Town Council, Snowdonia National Park Authority, Gwynedd Council, Councillor Dilwyn Morgan, the lake warden and local businesses to name a few.
We have received ideas including footpath and access improvements (all abilities access improvements on paths such as reducing barriers, surfacing upgrades and reducing ramp gradients and targeted improvements around Penllyn Leisure Centre), new public seating areas, car park upgrades, habitat restoration and new tree and hedgerow planting.
Why have trees been allowed to grow in the embankments?
Whilst some of the more mature trees pre-date the 1950’s scheme, a large number (mainly ash) have self-seeded within the stone wave protection and on the crest of the embankments. Their growth might ideally have been controlled more strictly in the past through frequent clearance to avoid the need for the maintenance now required. The tree management we have done up to now has been focussed on monitoring their health and form, and any tree surgery or tree removal work has been prioritised around public safety.
We do know that some of the ash trees are infected with ash dieback (‘chalara’); this, and their sub-optimal rooting and growing environment within embankments and between slate stone slabs, does mean they are generally not in good health. Future maintenance regimes of the embankments will control sapling growth and ensure that the same situation is not allowed to develop.
Does this affect the potential future Railway project?
We have been working closely with Bala Lake Railway and localised enabling works have been incorporated into the scheme. Our scheme includes for future proofing the embankments so that they are ready for the new tracks should a future scheme receive the necessary permissions. The railway operator is progressing the necessary permissions required.
Will the capacity of the lake be increased?
No, the capacity of the lake will not be increased.
Will the embankments be raised?
The embankments will not be raised – but they will be strengthened and the lakeshore stone wave protection will be improved.
What will the new scheme look like?
The most notable change will be due to the vegetation and tree clearance with unrestricted views of the lake. Whilst the combination of tree loss on the embankment face and improving the stone wave protection will result in a change in appearance, it constitutes a return to something more similar to how the embankment would have looked following the Bala Lake Scheme in the 1950’s.
Llyn Tegid, Wales’ largest natural lake, first became a reservoir in the 19th Century. To guarantee a supply of water to the Shropshire Union Canal, Thomas Telford built sluices at the outlet of Llyn Tegid. Water released through these sluices was abstracted into the canal at Horseshoe Falls, Llangollen.
Then, in the 1950's, the Dee and Clwyd River Board built the Bala Lake Scheme. The lake’s natural outlet was lowered (bypassing Telford's original sluices), and new sluice gates were built downstream of the confluence with the Afon Tryweryn. Embankments were built to contain water stored behind the sluice gates and to provide flood protection to the town of Bala.
This provided around 21,000,000 m3 (cubic metres) of controllable, stored water in Llyn Tegid. This storage capability means that Llyn Tegid is considered a reservoir under the Reservoirs Act 1975.
Today this reservoir is operated, alongside Llyn Celyn and Llyn Brenig, to ensure a continuous supply of water for abstraction from the River Dee. This can reach up to around 800 Ml/d (Megalitres per day), by three water companies and the Canal and Rivers Trust. Releases also maintain minimum flows at key locations on the Dee to protect the environment.
In addition, flood water run-off is detained in Llyn Tegid, in a short-term and controlled way, to greatly reduce the frequency and extent of flooding in the Dee Valley downstream of Bala.
Will the Dee operating rules be changed as part of the scheme?
No, the operating rules will remain unchanged.
How can I get in touch with NRW?
To get in touch with the project team, please email LlynTegid@naturalresources.wales
To watch our new video about the project and for the latest information please visit naturalresources/llyntegid