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Llanmaes Flood Alleviation Work

Llanmaes has suffered several recorded flood events dating back to the 1990’s and anecdotal evidence suggests the problems are even older than that.

 

A number of small civil engineering construction schemes have been undertaken in an attempt to alleviate the problems.

 

 Llanmaes-Flooding

 

A Pre Feasibility Study was undertaken in 2004 which outlined some strategic scheme proposals. The issue had become so bad that the residents setup its own group and undertook their own flood appraisal study.

 

Following further flooding in 2007 the Vale of Glamorgan Council undertook a Project Appraisal Report (PAR) to examine the problems and provide a preferred option for design.

 

This option did not initially attract funding from the Welsh Government (WG) and so it was not progressed until the Vale of Glamorgan provided funds to develop the preferred option from the PAR.

 

Mott MacDonald (MM) were appointed to develop the preferred option in February 2012. They then undertook a number of surveys and ecological reports and developed the preferred option to a design stage. Funding for the preferred option was announced by WG in December 2012.

 

Following a review of the scheme hydraulic modelling the need for additional storage capacity in the scheme was identified, and a re-appraisal of potential options undertaken.  

 

During development of the scheme a new road was constructed south west of the village impacting on the potential for upgrading an existing NRW flood storage area.  This resulted in the Council working collaboratively with the Welsh Government road scheme to deliver a new flood attenuation area downstream of Llanmaes Village and just upstream of the Northern Access Road to mitigate against any potential impacts of the village works still in design.

 

The scheme design includes cut-off ditches and low bunds, forming storage areas, in the catchment above to intercept, slow and divert flows from the village.  Within the village the main road through the village will be reprofiled to convey any remaining flows through the village without impacting on properties.

 

Latest Updates

 

04/05/2023

The Minister for Climate Change has allocated funding of £3,090,885 for construction of the Llanmaes FRM Scheme for the 2023-24 financial year.  The project still remains subject to an ongoing scheme reappraisal and approval of the resulting construction business case by Welsh Government to proceed.  Full details of the Welsh Government Flood and Coastal Erosion Risk Management Programme 2023 to 2024 are available here.

 

21/10/2022

A more detailed reappraisal of the scheme economics has been commissioned to reassess the scheme benefit-cost ratio, requiring additional flood modelling work to fully capture all the scheme benefits.  We are anticipating the results of this assessment by early March 2023 and a pre-emptive bid to the Welsh Government capital flood pipeline for 2023-24 has already been submitted for the scheme.

 

20/10/2022

Procurement of the construction phase of the scheme commenced at the end of 2021 but unfortunately the council has been unable to award the contract to date.  After initially poor interest from suitable contractors in tendering for the works, significant increases in construction costs during the procurement phase have now resulted in the benefit-cost ratio (BCR) of the scheme -  a measure of the cost of construction against the damages likely to be averted over the design life of the scheme – falling below parity.  Welsh Government’s standard funding criteria requires a BCR greater than one for flood risk management schemes, i.e. the cost of the scheme is less than the flooding damages likely to be averted.  We are working closely with our design consultants to more accurately assess the impact of the cost increases on the BCR and also assess other options or measures that could be progressed to achieve a BCR of greater than one.  We are anticipating the results of this assessment by the end of November 2022 and we will also be meeting with the contractors who have tendered to date to maintain interest in delivering the scheme.

 

15/07/2022

Enabling works to divert a rising main successfully completed by DCWW’s contractors.

 

30/05/2022

Enabling works to divert a DCWW rising main on Sigingstone Lane are planned from early June 2022 for approximately four weeks.

 

07/04/2022

Formal approval of the scheme Flood Consequence Assessment has been received.  Full details are available via the planning register (2021/01082/1/CD)

 

27/01/2022

Planning approval has been granted for the scheme.  Full details are available via the planning register (2021/01082/RG3).

 

12/01/2022

The monthly checks of the highway drainage / gullies in Llanmaes village, including ditch alongside The Green, were completed on 1 November 2021, 30 November 2021 and most recently on 7 January 2022.


08/11/2021

The latest check of the highway drainage / gullies in Llanmaes village, including ditch alongside The Green was completed on 1 November 2021.


07/10/2021

The latest check of the highway drainage / gullies in Llanmaes village, including ditch alongside The Green was completed on 1 October 2021.


07/09/2021

The latest check of the highway drainage / gullies in Llanmaes village, including ditch alongside the Green was completed on 27 August 2021.


05/05/2021

The latest check of the highway drainage / gullies in Llanmaes village, including the ditch alongside The Green was completed on 28 April 2021.


 

20/04/21

AECOM Ltd., acting as Agent on behalf of Vale of Glamorgan Council, is intending to apply for planning permission for the implementation of the scheme. For more information, please see the letter to local residents and the dedicated website, prepared by AECOM Ltd. If you'd like to respond to the consultation comments must be submitted by 18 May. 

 

13/04/2021

The latest check of the highway drainage/gullies in Llanmaes village, including the drainage ditch along the western side of the Green was completed on the 30 March 2021.


15/03/2021

To assist with ongoing flooding concerns within the village during heavy rainfall, the Council is maintaining a monthly check of the highway drainage / gullies, including the drainage ditch along the western side of the road alongside The Green.

 

This calendar year these assets were checked and cleansed on 05 February 2021 and then again on 26 February 2021. The next scheduled inspection is programmed for the end of March 2021.


15/03/2021

The detailed design has been submitted by the scheme consultants AECOM and is currently being reviewed internally prior to approval - Scheme Proposals.

 

The review of the detailed construction pack has slipped but is now due for completion in March 2021, with the additional details now being relayed to various interested landowners through the Council’s land agent.  

 

The next phase of work includes preparation of a planning application, including public consultation, where the scheme will be presented more widely to the community. Subject to successful landowner negotiations and obtaining all necessary consents and approvals construction is planned for summer 2021.

 

A full update was reported to Cabinet on 25 January 2021 (Minute C456) - Scheme Programme.


08/02/2021

The detailed design has been submitted by the scheme consultants AECOM and is currently being reviewed internally prior to approval - Scheme Proposals. A review of the construction pack commenced in December 2020 and is due for completion in February 2021. The next phase of work includes preparation of a planning application, including public consultation, which will commence once the final design is approved internally. Subject to successful landowner negotiations and obtaining all necessary consents and approvals construction is planned for summer 2021.

 

A full update was reported to Cabinet on 25 January 2021 (Minute C456) - Scheme Programme.

 

 

 

Key facts:

Scheme is promoted by:

Vale of Glamorgan Council

 

Scheme is Financed by:

 - Vale of Glamorgan Council

 - Welsh Government

 

At risk of flooding:

49 Properties

 

Estimated Cost of scheme:

Under review

 

Anticipated timescale:

Design and development 2012 to 2023

 

Construction 2023 to 2024

 

Overall objective:

To significantly reduce the flood risk to the village of Llanmaes

 

Lead officer:

Clive Moon

 

The Vale of Glamorgan Council
The Alps
Wenvoe
CF5 6AA