Project Overview

The project involved constructing an 8.0 m internal diameter, 33 m deep reception shaft and a 7.5 m internal diameter, 45 m deep launch shaft, both formed using an underpinning method well‑suited to the local ground conditions. An 1800 mm precast concrete tunnel was installed between the two shafts to house twin DN700 pipelines rising to the shaft collars. Additional works included the replacement of existing twin pipelines, application of Macropoxy P300 protective coating, installation of new ductile iron pipes with ES1212 coating, pipework connections and joint wrapping, 385 m³ of tunnel grouting, installation and testing of vertical pipes on both the East and West sides, mass‑fill operations, PCC slab construction, and final backfilling of both shafts.

Our Approach

Drawing on extensive experience with complex shaft and tunnel construction, Joseph Gallagher developed a robust methodology tailored to the challenging sandstone geology of the Tees Valley site. Two shafts were constructed - an 8.0 m ID, 31 m deep launch shaft and a 7.5 m ID, 45 m deep reception shaft - both delivered using underpinning techniques that aligned with the ground conditions and project requirements.

Between the shafts, an 1800 mm diameter precast concrete tunnel was installed to accommodate two DN700 pipelines. The pipelines were coated appropriately - existing pipes with Macropoxy P300, and new ductile iron pipes with ES1212 - and all connections and joint protection works were completed to specification.

Grouting was applied between the tunnel lining and the pipes to ensure long‑term stability and prevent water ingress. Vertical pipes on both the East and West shafts were fully installed and tested. Final activities included mass fill, slab installation, and backfilling of both shafts, completing the works safely and successfully.

Project Challenges

The project presented several operational challenges:

Artesian water conditions, identified during construction, required the design to be reviewed and updated.
Load restrictions at the West Shaft affected mobilisation and required careful planning of plant movements.
Access limitations necessitated the use of a smaller crane, resulting in some additional handling of materials.
Adverse weather, including strong winds, impacted lifting operations and required flexible sequencing.

Despite these factors, the works were completed safely and to the required quality through proactive planning and close coordination with the main contractor.

Innovations

Working within artesian water conditions required specific modifications to maintain tunnel stability and ensure safe progress.

A new fibre‑reinforced concrete mix was developed for the base plug to enhance performance and reduce the potential for shrinkage cracking.

Although this mix was ultimately not required on site, the development demonstrated a proactive, value‑focused approach to risk management and engineering refinement

Added Value

We worked with designers to refine the reduced base plug in the West Shaft and agreed on a safe sequence for breakthrough into the West Shaft. An underwater concrete mix was also accepted for use during the works.

Community Involvement

We supported the main contractor with community activities when requested, such as site visits and project updates.

Although our direct involvement was limited and the relationship with the client became challenging following the artesian water issue, we remained professional, focused on delivery, and maintained progress through close coordination with the main contractor.

Community Involvement

We supported the main contractor with community activities when requested, such as site visits and project updates. Although our direct involvement was limited and the relationship with the client became challenging following the artesian water issue, we remained professional, focused on delivery, and maintained progress through close coordination with the main contractor.