Replacement required to repair Haweswater Aqueduct 16 Nov 2020

A programme of works to replace more than 50km of water conveyance aqueduct, across six sections on the 109km Haweswater Aqueduct in northwest England, is being prepared by UK water company United Utilities. Procurement on the £750 million to £1 billion project will begin in March 2021 with the publication of the contract notice. According to the company, contract award is expected to be in mid-2022 on a design-build-own-finance basis, with construction work expected to begin in 2023.

The planning application and environmental surveys are also expected to be published in early 2021. The online public consultation documents suggest that TBMs will be used for construction.

More than 50km Haweswater aqueduct to be replaced

The route covers three counties from its northern end in Cumbria, through Lancashire, and to its southern end at the existing Woodgate Hill water treatment works in Bury, Greater Manchester. In a 2019 response to feedback from UK water industry regulator, Ofwat, regarding a cost assessment for the scheme, United Utilities puts the total length of tunnelling at 51.5km, divided into the following sections and provisional lengths:

• Docker: 3.5km
• Swarther: 8.5km
• Bowland: 16.6km
• Marl Hill: 4.3km
• Haslingden & Walmersley: 18.9km

Initial preparatory work is underway with Costain awarded the early contractor involvement contract in September 2019 to advise on preliminary design work, temporary land requirements for construction, and land and environmental surveys and investigations.

The importance of preparatory investigations is being increasingly recognised within the UK, as United Utilities notes in its response to Ofwat concerning the proposed cost of ground investigations. According to the company, the “consequences of poor preparatory work, such as adequate initial investigations accompanied by an appropriate level of geotechnical baseline reporting, are becoming apparent within HS2 where [three] cost overruns, at least in part attributed to geotechnical reporting, are an ever-increasing problem threatening the financial logic of the project.”

The Haweswater Aqueduct programme of works also poses some atypical conditions for ground investigations in the UK with the average depth of more than 200 boreholes along 46km of the proposed route reaching 70m and a maximum depth of 240m on the Bowland section. There is a comparatively low amount of existing ground investigation information available along the project route.

After a series of market engagement events, United Utilities has opted to undertake one procurement exercise to engage a competitively-appointed provider (CAP) to design, build, finance and maintain the project. A second option, to run two parallel procurement exercises, one for the construction contracts and another for the funding of the CAP agreement, was rejected.

Northern connection of new Hallbank pipelines

In an April 2020 notice, United Utilities said it had “considered how both procurement routes would be able to best achieve the key criteria of time, complexity, maximising competition and market appetite.” Based on this assessment, the company “decided to run a single CAP procurement, as this option best meets the criteria.”

Built between 1933 and 1956, the 2.6m i.d. gravity-powered Haweswater Aqueduct supplies up to 570l/day of drinking water to Manchester and to communities in the Pennines, accounting for a third of the supply to the region. Recent investigations have indicated that the condition of the aqueduct is deteriorating and, although some more urgent repair work has already been undertaken, a longer-term solution is required to ensure the future viability of the pipeline.

“We shut the entire pipeline for two weeks in 2013 for its first ever complete inspection” said John Hilton, Project Director for United Utilities. “After detailed analysis and a further inspection in 2016, engineers identified several places where they needed to do some maintenance. A section at Hallbank was the first one.” Work at Hallbank comprised replacing a 2.5km section of the aqueduct with four 1.6 i.d. pipes, the first major upgrade to the aqueduct for more than 65 years. Taking two years to construct, the new section went into operation in November 2020.

“This is only the third time that the aqueduct has ever been drained,” continued Hilton, who has also been present on each of the previous two occasions. “This time we were working during a pandemic and during heavy storm conditions.” Work to connect the new pipes took just under 8 days to complete. At the same time, to take advantage of the opportunity created by the draining of the aqueduct, engineers entered the aqueduct further south to carry out further inspection work.