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Case Study – AMP5 Upgrade at Walton le Dale WwTW

Case Study- AMP5 Upgrade at Walton le Dale WwTW

Sector: Water and Utilities

Client: United Utilities

Contractor: KMI Plus

Location: Walton-le-Dale, Lancashire

Scheme: AMP5 Programme

MGF Depot: Astley, Manchester

Products hired: MGF 406 UC Brace, MGF 400 Series Strut, Larsen sheet piles, trench boxes, manhole boxes, Vetter pipe stoppers

Drone footage of water utilities excavation in a rural area

Site overview:

United Utilities commissioned a major upgrade to the existing Waste Water Treatment Works in Walton-le-Dale near Preston as part of their AMP5 programme. The works site was partly located on a flood plain with high water tables and the risk of flooding had to be considered from the out-set of planning.

Scope of works and solutions:

The three most notable excavations on the site and the equipment MGF delivered to support these were as follows:

– Humus Tank Excavation: 30m diameter and 6m deep. MGF provided a bespoke, circular, cantilevered, Larsen sheet piled cofferdam.

– Cross Over Weir Excavation: 18m x 10m and 4.5 m deep. MGF provided MGF 400 Series Struts, MGF 406 UC Brace and trench sheets. The shoring of this excavation was complex with changing requirements which MGF were able to accommodate.

– Outfall Pumping Station Excavation: 17m diameter and 8m deep. MGF provided bespoke designed, octagonal shaped MGF 406 UC Brace hydraulic systems complete with inter-locking Larsen sheet piles to help minimise groundwater ingress. The octagonal design was developed to accommodate existing structures on site and keep access roads open. The outfall pumping station was positioned close to another structure and extra care was taken to ensure that neither excavation affected the other.

Above image of workmen inside a water utilities excavation supported by MGF braces


MGF provided KMI Plus with made to measure systems that were easy to install and remove whilst providing a safe working environment and optimum working space. The solutions allowed site access to remain open and reduced the levels and flows of ingress water from the flood plains. MGF conducted site investigations and soil inspections and offered on site training in shoring and safety awareness. The designation of a single design engineer to the scheme ensured that the contractors temporary works design requirements were fulfilled.

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