Construction
Bewl Water Reservoir
Overview
- Client: CMDP-JV (Costain and MWH Treatment)
- Project Value: £2.8m
- Dates: June 2025 – Present
Bewl Water is a Category A reservoir under the Reservoirs Act 1975. An emergency drawdown facility is to be constructed at Bewl Reservoir that can drawdown the upper 5 m of the reservoir within 5 days. The chosen solution is three siphons over the dam, discharging downstream, in conjunction with the uprating of the existing washout facility.
GPS MACS have been appointed as the marine contractor for installation of all underwater and above water infrastructure.
We were appointed on the project as the marine contractor:
- Installing 3no. 1770mm diameter pipes from marine environment working from marine plant mobilised landside with no waterway access from rivers or canals.
- Managing diving operations for installation and use of Aris survey equipment for quality assurance.
- Mobilisation of a link float pontoon and hydro master engine built and operated by GPS MACS
- Complex fabrication and installation of temporary works in relation to frames and rails used for pipe installation. Installation of the winch frame and seating beam on the sloped concrete revetment All drilling and fixing associated with installation.
- Guide rail installation involved complex sequencing, particularly for the submerged sections. Working on a steep underwater slope, divers will use airbags to carefully control the descent of each rail section from the pontoon. Visibility and underwater positioning will be constant challenges to overcome.
- All water-based operations had to be planned with strict environmental controls due to the reservoir’s protected status. The use of pontoons, dive support boats, fuel management, and access around the water required ongoing coordination with environmental leads. All materials and equipment brought near the water were logged and controlled to avoid contamination risks.
Project delivery
- We were employed as the marine contractor with overall responsibility for the safe and effective delivery of the works delivered from the reservoir.
Engineering
- Stability analysis for the pontoon with deck loading capacities considering mini crane and dive spread.
- Planned, supervised, and carried out all lifting operations on site (landside and marine). Most notable being the 24t lift of a fully welded 1770mm diameter pipe into the reservoir with a minimum 60-meter radius.
- Site wide Temporary Works Coordinators. Completing temporary works designs, inspecting and signing permit to loads and providing support to the project team for implementing solutions to challenges.
- Site engineering including quality assurance, setting out and surveying, drawings, coordinating works and planning of operations
- Roller frame installation was made difficult by uneven ground and the requirement for precise alignment along the guide rail path. Each frame was individually adjusted and fixed to follow the rail angle, and tolerances were checked with survey support before being signed off.
- Installation of winch frame works have to be carefully planned and carried out using specialist equipment under strict exclusion zones underwater. Accurate positioning was maintained using Leica TS16, with anchor setting completed to spec.
- Despite complexity of lifting operations, tight site constraints, and working within a live reservoir, all critical tasks will be delivered safely, with full QA traceability and progressive handover.
Marine Logistics
- Planned, supervised and carried out mobilisation of all marine plant to site. Including link float pontoon and dive spreads.
Commercial diving operations
- MACS Diving carrying out all diving operations.
- Underwater concreting and grouting
- Control of pipe placement and installation of restraint steelwork
- Monitoring Aris surveys and recording information.
Construction
- Installation of 3 no. 1770mm pipes
- Installation of precast slabs and rail
- Connection between landside installed pipes and marine installed pipes.
- Fabrication of temporary works systems
- Welding work had to be carried out in exposed conditions. Temporary weatherproof tenting is to be installed to create a controlled environment for safe, clean welds. Fume extraction and lighting were also installed to ensure the team could operate to high standards regardless of weather.
