DREDGING a massive marine lake in the Dee Estuary could cost Wirral Council more than £9.1m while carrying out major repairs to the lake’s outer wall and walkway could cost £9.5m.
West Kirby Marine Lake is home to the Wirral Watersports Centre while the walk around it is a popular walking route.
The lake is massively popular for sailing and other watersports with beautiful views over the Dee but a new report said silt built up inside the lake as well as an invasive species of seaweed was being investigated. Wirral Council, which owns the 54-acre man made lake, is looking into what actions can be taken to address issues.
Councillors will be asked next week, on December 3, to approve another survey of the lake bed to better understand how much material has sunk to the bottom and how water depth can be managed. Officers are also expected to be instructed to monitor the impact of invasive seaweed sargassum muticum as well as inspections of the marine lake wall.
At the moment, the council said the seaweed was not impacting sailing activities and monitoring both seaweed levels and the footpath wall’s condition would help avoid massive costs for now. This follows a consultant report by Binnies in 2020.
In 2020, it was estimated about 28,000 metres cubed of mud and sand was on the bottom, the equivalent of around 11.2 Olympic swimming pools. This was found mainly against the outer wall and northwest corner but as this may have changed, the council said another survey was needed before moving ahead with any works.
The 2020 surveys found the invasive seaweed, first reported in 2018, hadn’t spread as predicted and reports from marine lake users said it wasn’t the problem it was feared to be. However the lake’s outer wall continues to have issues.
When building the lake, cost cutting measures in 1987 reduced the thickness of the asphalt used which meant that after ten years the wall was already having issues and left exposed in some areas. Patch repairs were done in 2003 to fix this.
The entire wall was reconstructed between 2009 and 2010 with the lake being emptied and thicker asphalt than originally planned used. However council inspections in 2018 found the wall was exposed in some areas with the refilling of the lake following building works believed to be a factor.
The Wirral Council report said work has to be done to improve the lake or fewer people will use it in the future leading to a drop in income. Income for this year is expected to be around £154,000 but remedial work to the lake could lead to some very high costs.
The 2020 Binnies study found it could cost between £1.976m and £9.127m to clean the lake depending on seaweed contamination and how hazardous the waste is. This would have been between £38 and £325 per cubed metre but a recent dredging of non-hazardous waste from Ashton Park lake cost £111 meaning costs could now be different.
A key reason for the cost is because material from the lake can’t be discharged into the Dee estuary and will have to be taken away. This is because doing this could spread the invasive seaweed that is in the lake.
A management plan approved by the council in 2022 suggests dredging costs would be far from the only cost linked to the lake. Patch repairs were estimated to cost £1m while major works to the outer wall could cost between £3.7m and £9.5m while designs for any new wall could cost between £75,000 and £250,000.
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