Wells to Glastonbury Pipeline (2023)

Pipeline spread and ongoing welding activities through the village of Polsham - Courtesy of envolve infrastructure

The  Wells to Glastonbury Pipeline will ensure that approximately 13,000 customers have resilience of water supply by providing a secondary source and route to Windmill Hill Reservoir for the purposes of maintaining a safe supply of water to Glastonbury and Street in the event that the primary main from Cheddar WTW to Cooks Corner is temporarily lost or compromised. The £6m capital investment by Bristol Water will provide an 8km pipeline by March 2023.

Undertakings

Procurement of the scheme was made via Bristol Water’s two existing Network Maintenance Service Contract Strategic Partners. On completion of a thorough value and quality competitive tender process, envolve infrastructure was appointed as the delivery partner for the project in the form of an NEC Term Service Contract (Option C). The existing framework incentive mechanisms were applied, scoring scheme specific and framework performance KPI’s in calculation of any pain/gain on project completion.

The anticipated programme duration of 34 weeks substantially reduced regulatory risk for Bristol Water with significant improvements on the original anticipated programme duration (anticipated completion October 2022), comfortably achieving the regulatory in use date (March 2023).

Ongoing construction works – Courtesy of envolve infrastructure

Early contractor involvement (ECI)

ECI was integral to the delivery model from the outset. Envolve infrastructure’s proven relationship with Bristol Water on ECI holds successes in providing both robust technical solutions, meeting needs of the operational teams and its customers, whilst providing a cost-effective and value driven solution.

Detailed ECI commenced partnering with the Bristol Water in house design team in developing the detailed design. The ECI strategy was investigating and minimising risk whilst extracting and exploring opportunities for an efficient and cost beneficial delivery programme for Bristol Water. This included:

• Development of access and egress routes.
• Consultation with external stakeholders (landowners, EA, Highways).
• Environmental management.
• Value engineering opportunities.
• Engagement with specialist supply chain – for example, horizontal directional drilling (HDD).
• Engaging and developing relationships with local organisations and communities.
• Exploring social value objectives and opportunities.

(top left) 360° view stretching from Glastonbury Torr in the South to Wells in the north, (top right) pipeline easement at Wells and (bottom) the internationally important Somerset Levels and Moors, demanding the utmost of environmental and biodiversity care and attention – Courtesy of envolve infrastructure

Design

The in-house design team was immediately integrated into envolve infrastructure’s ‘One-Team’ model and, in conjunction with the expertise of the design manager and construction team, formed an integral part of the ‘One-Team’ delivery model.

The ‘One-Team’ approach guaranteed a collaborative partnership from the outset and facilitated an efficient and coordinated design process for Bristol Water. Envolve’s responsibility during the design process reviewed suitability and efficiency of the outline design, planned construction methodology, and proposed route to collaboratively develop the final design.

During this stage, envolve infrastructure developed the delivery strategy. HDD would be delivered by GMAC Utilities; a long-term strategic supply chain partner. Open cut sections were being delivered by envolve’s directly employed skilled workforce.

Paramount to the success of the scheme was the ‘One-Team’ approach between the stakeholders, which reinforced the utmost confidence from Bristol Water in the delivery strategy and structure.

Expert review and value engineering proposals identified multiple potential improvements to both installation technique, route and process. Key proposals determined major design decisions and changes, ensuring the most efficient and risk-mitigated product for Bristol Water.

Drone views of works areas – Courtesy of envolve infrastructure

In addition to this, investigations during the design process provided Bristol Water with £240,000 of potential value engineering opportunities:

• Use of excavated material as bed and surround: £100,000.
• Alternative route: £100,000.
• Specification of pipe material: £40,000.

As part of the outline design review, the profile of the pipeline through each section was challenged to ensure it would not only be the most cost-efficient method of delivery but also offered a benefit to the operating cost of the pipeline.

A section of the pipeline passes through a layer of peat. Along each field there are regular drainage ditches that would require drilling, which led to an irregular profile requiring washouts and air valves, reducing the efficiency of pipe and increased energy usage to pump the water. The design solution  proposed a constant gradient below the layer of peat in a band of clay, which increased its efficiency and removed the need for unnecessary apparatus.

Once works commenced on site, envolve infrastructure was appointed as principal contractor with Bristol Water retaining the role of principal designer. Although Bristol Water’s in-house team retained ultimate control of producing the design, envolve’s commitment and appointment through the ECI process and the value engineering proposals were integral to completing the final design as a combined collaborative delivery partnership.

An open cut section of pipeline at Wells – Courtesy of envolve infrastructure

Construction

A review of the route identified the most efficient installation technique and HDD was selected for over 1.5km of the pipeline to mitigate ground and environmental risk through the internationally important Somerset Levels and Moors. Depth, route adjustments and methodology all forming part of the design proposal with a focus on the location of permanent operational apparatus in line with the project brief. During the pre-construction phase, an access/egress plan was agreed with all stakeholders through early engagement by identifying all landowners and agreeing the most efficient routes and locations for compounds. This ensured enabling and reinstatement works were agreed in advance; mitigating third party late changes and future programme risk.

A central main compound location housed the shared project office facility, material storage and waste processing facilities. The yard team operated a quarantine zone for deficient/damaged materials to reinforce envolve’s uncompromised quality standards. Three satellite compounds housed the site-based welfare and material storage, facilitating direct to site deliveries, mitigating double handling, and reducing vehicle movements. A delivery gang structure was created from envolve’s highly experienced directly employed staff and workforce.

Welding activities – Courtesy of envolve infrastructure

The in-house training team facilitated training requirements ahead of commencement. Self-delivery teams were supplemented with specialist subcontractors with whom envolve had long-standing relationships.

Works were constructed offline on up to six work-fronts, varying between site preparation, open cut, directional drilling and reinstatement, simultaneously working across the 5km route.  Construction operations were managed by envolve’s highly experienced, directly employed, site management team supported by the in-house SHEQ department.

The scheme comprised two critical interfaces with Bristol Water live assets and these connections will be undertaken by Bristol Water Operations. Throughout the commissioning stage, assistance from envolve’s expert management and delivery teams will ensure a seamless interface between the specialisms.

Wells to Glastonbury Pipeline: Supply chain – key participants

• Client: Bristol Water
• Delivery partner: envolve infrastructure
• Horizontal directional drilling: Gmac Utilities Ltd
• Pipeline materials: Aliaxis UK
• Chlorination: Suez Water UK
• Fencing & reinstatement: Huw Jones Fencing
• Road surfacing: Walton Civil Engineering
• Traffic management: Renteq Highways Limited

Horizontal directional drilling – Courtesy of GMAC Utilities Ltd

Carbon management

To assist with achieving our net zero carbon commitment by 2040, envolve installed a permanent power supply connection for the main compound with a ‘green’ electricity supplier, removing the need for temporary diesel power generation. The use of hydrotreated vegetable oil (HVO) is key to meeting this target. A trial of HVO fuel and fueling stations conducted on the project achieved a 90% reduction in C02 emissions across the diesel consuming fleet and was regarded as a runaway success.

The design solution to drill at a constant grade across the peat locations enabled the design to remove unnecessary apparatus from the pipeline. In turn, this enabled the pumps operating the network to operate at a more efficient output thereby reducing the energy consumption and carbon emissions in the ongoing running and management of the pipeline.

Construction design management

CDM15 regulations were discharged through the development of a detailed construction phase plan and through collaborative working. The design was approved through a detailed design process review, regular meetings and early engagement, retaining a collaborative relationship with the team. Stakeholders remained at the heart of the delivery, through conducting weekly progress meetings for the duration of the scheme covering design, construction progress, environmental and 3rd party interfaces.

Construction activities – Courtesy of envolve infrastructure

Social value

During the summer of 2022, the team engaged with St Cuthberts Parish Council to work together and deliver a community benefit project. The Parish Council required a stream crossing on a public footpath at Coxley Recreation Ground, which needed to be completed in time for the Platinum Jubilee. With only 4 days notice the team started construction of the river crossing and handed over the crossing ahead of time to the delight of the Parish Council.

Summary

The success of this project will ensure future resilience in the water supply to the residents of Glastonbury for decades to come. Envolve infrastructure’s role through design and construction has reinforced the company’s commitment and expertise as the strategic partner of choice for Bristol Water and is testament to the trust and collaboration forming the foundation of our partnership.

Hannah Milliner, Head of Capital Delivery, Bristol Water commented:

“Envolve’s Collaborative approach to delivery achieved a one team approach. We collectively worked to overcome challenges, delivering a successful project ahead of programme. This approach resulted in project risks either being mitigate or managed by drawing on knowledge from across the team, resulting in the overall project being delivered under budget.”

The delivery team, presenting the ‘Jubilee Bridge’ to St Cuthberts Parish Council - Courtesy of envolve infrastructure