Mott MacDonald Bentley (MMB) were contracted by United Utilities (UU) to design and build a scheme to meet a DWI objective to facilitate the isolation of the existing Malpas SR1, a key asset on the Vyrnwy aqueduct, to allow inspection, cleaning and maintenance. The three lines of the aqueduct were constructed in the late 19th century and each is approximately 1000mm diameter, supplying up to 360Ml/d of treated water to Cheshire, Merseyside and the surrounding areas.
The designed solution required construction of manifolds to cross-connect the three lines of the aqueduct upstream and downstream of the SR. Through consideration of constructability, Client impact for outages and construction programme, and working with the supply chain, the team developed an innovative solution to hot-tap onto the aqueducts for the connections.
The solution removed the need for drain-down and re-charge of the aqueducts and the consequent water loss and service disruption, as well as removing the risk of ingress and contamination through an open-cut connection. The quicker construction programme also significantly reduced the customer impact, which was a key factor as the site is in close proximity to residential properties and with a history of customer complaints.
The project was completed and commissioned ahead of the regulatory output date of 31 March 2020.