Project Description

Rhymney Bridge Dam Spillway Replacement – Case Study

Project Management – Utiligrid Limited
Principle Contractor and Client – Skanska
Asset Owner – Dwr Cymru Welsh Water
Project Value – £2.5 million

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Project History:

Rhymney Bridge 2 reservoir is an earthen embankment serviced by a brick masonry lined spillway channel. The spillway has a history of flood related damage, caused by plucking of the bricks during excessive flow conditions. Due to the size of the catchment and its available basin volume, the reservoir is very fast filling and the spillway is subject to flash flooding.

Project Scope:

Construction of a new reinforced concrete lining for the full spillway length, within the limits of the existing structure. Narrowing the existing footprint and heightening the walls to accommodate the Probable Maximum Flood.
Construction of a new weir slab downstream of the existing spillway.
Removal of silt and debris from within the scour inlet fore-bay and valve tower, installation of new debris screens over the scour inlets, refurbishing of the existing valves in the valve tower and replacement of missing rip-rap adjacent to valve tower.

Our Involvement

Manage the Dwr Cymru Welsh Water(DCWW) project governance process.
Developed the Project Programme (P6) to meet the expected regulatory output dates.
Built the Target Costs, accessed and approved the sub-contract target costs and programme.
Identified and mitigated Project Risk, before and during the Project.
Managed all internal and external stakeholders, DCWWNRW, Caerphilly CC, Atkins, All Reservoirs Panel Engineer.
Completed the Construction Phase Plan (CPP)
Oversaw mobilisation to the site.
Communicated progress and provide reports to the client.


Reservoir subject to flash flooding.
Access to the work areas.
Working on a steep gradient
Poor access via minor roads to the site.
Working within the reservoir to remove debris from the scour inlet tunnel.


The project realised the full scope, ahead of time and in financial gain.

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