Poynton Pool Spillway Improvements

We are planning to carry out safety improvements works to Poynton Pool.

Background

Poynton Pool is an ornamental lake located within the grounds of Poynton Park.

Due to the volume of water that can be stored in the pool it is classed as a reservoir under the Reservoirs Act 1975 (legislation.gov.uk). Therefore, Poynton Pool must be inspected at least every ten years to review its safety and ensure it continues to comply with current reservoir safety standards.

The most recent inspection required a check on whether the reservoir is resilient against a major flood event. For Poynton Pool, this type of flood is a 1 in 10,000 chance per year flood. This inspection found that compulsory safety improvements are necessary, and the Council is required to take action which will improve the site’s resilience against extreme flooding.

The west side of Poynton Pool has a 900m long bank and footpath. In large floods, water will flow over this bank, meaning it could be considered as an emergency spillway. In the event of extreme flooding, excess water flows over an emergency spillway to control the level of water in the pool.

The Council continues to take a proactive approach to managing reservoir safety, and thus the safety of people living downstream.

What the inspection found

The existing western bank (looking north towards Anglesey Drive).

Studies required by the last inspection of the pool found that the bank along the west side of the reservoir is not at a consistent level, and there are parts that are lower. Currently, in a large flood event, water would not flow over the bank evenly and would cause damage to the bank, leading to an uncontrolled release of water.

This would lead to extensive flooding and impact people and properties in the vicinity.

The existing trees along the bank also pose safety concerns. Flooding could cause trees to fall, increasing the likelihood of further damage to the bank, which would contribute to a further risk of flooding.

As a result of the inspection finding’s the Council is required to carry out safety improvement works and intends to complete these by the end of 2023.

What we are proposing to do

We plan to improve the resilience of the bank. The safety improvement works will affect 480m on the side of the pool next to the A523 London Road North.

To improve reservoir safety, low points along this bank will be raised to ensure that water flowing over the bank is spread out along the whole length, and not concentrated at a few low spots. A low kerb will also be added to ensure a consistent level.

The works will enable us to widen the path to two metres and resurface it with compacted gravel to make it suitable for wheelchair users and pedestrians.

We will also create two 40m wide clearings, which will further increase resilience, so if trees and shrubs block any overflow of water, there are at least two points where floodwater can safely spill across the bank and prevent it from building up in the reservoir.

There will also be a 2m-wide verge which will create a buffer to prevent tree root growth from damaging the new kerb.

Why the Council need to do this work

This is a public safety issue. We want to reduce the risk to the public, especially those living downstream. The works will make the bank on the west side of the reservoir level.

This will spread out the water over a longer distance and reduce the risk of the dam being washed away by the flood water and causing an uncontrolled release of flood water down the valley.

These improvement works are needed, regardless of any developments taking place in Poynton, as they are required by legislation.

We are aiming to complete by December 2023 to avoid the Environment Agency from using their legal powers to enforce works.

Independent engineers have evaluated the proposals

An engineer known as a panel engineer has inspected the pool and found that it does not meet safety standards.

Panel engineers are appointed by the Department for Environment Food and Rural Affairs (DEFRA).

The Council (who are the statutory undertaker for the reservoir) have regulatory responsibilities and have appointed engineer to draw up proposals to address the safety issues.

The council are following the advice of these experts in delivering the scheme.

A panel engineer, who was not involved in the inspection of the pool, has been consulted in the development of the proposed works.

How it will look

When we carry out this work, trees and lower shrubs along the bank will be affected. At least 44 trees will have to be removed and we will also need to remove some of the shrubbery in the area.

A further 37 trees are at risk of removal. Removal will depend on their root structure and depth, and whether they would be affected by the works.

These trees will only be removed if it unsafe for them to remain. We will do all that we can to keep the removal of trees and shrubs to a minimum.

We are applying for planning permission to undertake these works.

The tree loss is a result of the safety improvement works. The path is not intended to be a cycleway or linked to any cycle route.

If budgets allow, the Council intends to resurface the rest of the footpath along the western bank of the pool while it is carrying out the safety improvement works.

An overview of the planned works

Ecological and environmental surveys

In developing our plans to carry out these safety improvement works, the following surveys have been undertaken:

Tree surveys

Of the 86 trees identified in the survey, 2 were categorised as high quality, 62 as moderate quality and 22 as low quality. None of the trees are protected by any Tree Preservation Orders (TPO).  The site contains no veteran trees, Ancient Woodland, or registered ancient trees. The survey has not identified any trees which are legally protected from removal.

Bat surveys

Bat activity surveys were carried out on trees with potential for roosting bats on 8 June, 8  August and 30 August 2022.The bat surveys have not identified any bats roosting in the trees.

Great Crested Newt assessments

Assessments have not identified any evidence of Great Crested Newts at Poynton Pool.

These surveys are helping us to understand the biodiversity of the area. They are also necessary to ensure works can proceed without disturbing protected species.

Biodiversity

Due to the number of trees that need to be removed, we are actively exploring where biodiversity can be improved to mitigate for the loss of woodland habitat.

This may include:

• Lower-level planting
• Installing new bat boxes
• Replanting trees in the local area.

We are currently considering where planting could take place on Council land and deliver the biggest benefit to biodiversity. This will be finalised as part of the planning application.

For practical and environmental reasons, it is not proposed that Poynton Park will be a site considered for this, nor will it be possible to replant the trees on the bank once the works have been completed.

Due to the number of trees the Council would like to replant, it would be harmful to the existing biodiversity in the park to replant the trees here. and it would make it difficult for leisure activities, such as the Poynton Show, to take place in the park if too many trees were planted here.

We are aware that users of the area feel that trees provide some protection from noise and pollution. There is evidence that areas of dense woodland with greenery all year round can help to reduce noise and pollution. However, the trees in Poynton Park form a narrow belt, are quite widely spaced and lose their leaves at some times of the year and therefore only offer limited protection.

The trees must be removed as this work is mandatory and cannot be replanted in the same location due to safety risks.

The Council are trying to reduce the of level disruption the works will cause, by maintaining some level of screening for park users through retention of the lower shrubs through these sections.

Alternative options

The only option that would not see the loss of trees is a ‘do nothing’ option. Choosing this option is against the guidance in the Reservoirs Act and would lead to the Council being mandated to complete the works.

All other options still required the levelling of the embankment therefore the Council would need to do what we are doing whatever option was chosen. Some options would see more tree loss. None of the options would see less tree removal.

Feedback

The survey opened on Monday, 26 September 2022. and closed on Friday 4 November 2022.

This webpage has been updated from questions raised in the feedback we received.

Next Steps

The feedback we collected is now being considered ahead of a planning application for the scheme being submitted. A summary of the comments we receive will be published on this webpage.

It is anticipated that the planning application will be submitted in Spring 2023, with the intention to complete construction by the end of 2023.

More detail on timescales for construction will be provided once we have appointed a contractor.

Contact Highways

 

Page last reviewed: 13 July 2023