Southern Strategic Support Main

Southern Strategic Support Main

Southern Strategic Support Main



Primary Client:

Bristol Water


North Somerset


Nov 2016 to April 2018

Key Facts:

  • Collaborative approach.
  • Expected to be the largest single trunk mains project in AMP6.
  • 30.5 Km long – three pipeline contractors working concurrently.
  • Early contractor engagement.
  • Numerous environmental challenges.
  • 5 Km of Great Crested Newt Fencing.


The SSSM was the largest element of Bristol Water’s £27 million Southern Resilience Scheme, an investment to improve security of supply to over 280,000 customers. The scheme had been delayed by 18 months due to numerous environmental challenges realised from an Environmental Impact Assessment in the planning phase. Hence, the construction phase work became time critical and most urgent to meet an OFWAT Compliance Date.

The majority of the 30.5 Km pipeline was laid across agricultural land. 5 Km of ‘Great Crested Newt Fencing’ was erected and maintained and mitigation measures were employed for bats, badgers, dormice, birds and cave spiders.

Hydroline Solutions played a significant role, supporting its regular customer, Kier, in particular with technically challenging elements of the construction works. Hydroline Solutions’ technical expertise enables it to contribute innovative and secure Early Contractor Involvement, helping to reduce time related and financial risks.

The SSSM was split into standalone sections of work:

  • Three main sections of pipeline, mainly 600 and 700mm ductile iron pipework, purposefully awarded by Kier to three separate contractors for security of time delivery. One section, we suggest the most challenging due to topography, was awarded to Hydroline Solutions. Our section was to pass through an arboretum at Backwell House containing many hundreds of protected trees and requiring the felling of twenty. Hydroline Solutions proposed a modestly amended route which was adopted, saving eight of these protected trees. Through the works Hydroline’s team replanted thousands of bulbs.
  • A 1.9 Km section laid along an abandoned railway line called the Strawberry Line. This was not itself awarded to Hydroline Solutions but this special section of work included pipework installation through a 500 metre tunnel and cutting section through hard rock at Shute Shelve Hill. The tunnel is occupied by a colony of bats which had to be carefully considered and protected throughout. Hydroline Solutions contributed to critical Early Contractor Involvement and advised the reduction of the depth of cut into the rock floor by incorporating smaller diameter side by side pipelines, reducing root disturbance and improving ‘dragability’ of the pipes. This element was transferred to Hydroline Solutions. By reducing cut into the rock, environmental impacts, cost and time risks were also reduced.
  • Three sections of large (630mm / twin 500mm) diameter directional drilling at challenging locations, were awarded to Hydroline Solutions in recognition of its technical expertise:
    • Through the ancient protected woodland at Church Wood.
    • Crossing beneath the A370 main road at Rhodyate near Congresbury.
    • Crossing beneath the Congresbury Yeo River.
  • After Kier’s successful completion of the entire project, Hydroline Solutions was selected to undertake clearance of all compounds and associated reinstatement works.