Joseph Gallagher Ltd

Kendal Wastewater Treatment Works (WwTW)

Microtunnelling and deep shaft construction beneath the River Kent to provide critical wastewater infrastructure for the upgraded treatment works.

By: Joseph Gallagher Ltd

Published: August 12, 2026

Microtunnelling shaft construction at Kendal Wastewater Treatment Works by JGL.

Project Overview

Joseph Gallagher Ltd (JGL) delivered a complex microtunnelling and shaft construction package as part of the redevelopment of Kendal Wastewater Treatment Works (WwTW). The scheme involved the installation of a new wastewater transfer tunnel beneath challenging geological conditions, including limestone and glacial till, and beneath the fast-flowing River Kent.

The works comprised the construction of two deep shafts, a 112m-long microtunnel and associated open-cut connections to the existing network. Fixed outfall constraints and the proximity of the river required precise control of tunnel alignment and depth throughout the installation. Despite the challenging environmental and ground conditions, the project was delivered successfully and met all client requirements.

Segmentally lined reception shaft constructed by Joseph Gallagher Ltd as part of the microtunnelling works for the Kendal Wastewater Treatment Works redevelopment.

Scope of Works

JGL’s scope included construction of a 5 m diameter, 17 m deep segmental reception shaft and a 6.4 m diameter, 14 m deep drive shaft (secant piled by others). A Herrenknecht AVN1800 MTBM was used to install the 1.8 m ID microtunnel, within which a 900 mm concrete carrier pipe was installed and fully grouted. The package also included around 40 m of open‑cut excavation to tie into existing assets, along with full temporary works design, labour, plant and materials.

Construction Challenges

The project was delivered from two confined work areas, with the drive shaft located adjacent to residential properties and the reception shaft situated within a live treatment works.

Ground conditions varied significantly along the route, ranging from hard limestone to glacial till containing sands, gravels and large boulders. The tunnel alignment beneath the River Kent required careful control of line and level to maintain the required gravity flow gradient while protecting the surrounding environment.

Delivery and Innovation

The microtunnel was installed using closed-face MTBM technology, providing effective ground support and maintaining stability throughout the drive.

During construction, larger-than-anticipated boulders were encountered within the glacial till. JGL utilised its in-house plant fleet to upsize the tunnelling machine, allowing the drive to continue safely and efficiently without impacting the programme.

Close coordination between JGL, the client and the principal contractor ensured safe project delivery and effective management of the site’s operational and logistical constraints.

Outcome

Despite challenging ground conditions, constrained working areas and the requirement to tunnel beneath the River Kent, the works were completed safely and successfully. The completed tunnel and shafts provide critical infrastructure for the redeveloped Kendal WwTW, delivering a durable and resilient wastewater transfer solution for the site.