Tackling depth and groundwater in Scottish Water pipeline upgrade
Saltcoats, Ayrshire
Project Overview
| Location |
|
|---|---|
| Sector | Water |
| Application | |
| Products |
The challenge
When installing a new pipeline for Scottish Water in Saltcoats, Ayrshire, as part of a wider sewer main upgrade project, George Leslie had to directionally drill beneath a watercourse. To facilitate the safe delivery of the enabling works, including the excavation of a 10m deep drive pit, the civil engineering contractor turned to us for support.
Scottish Water is upgrading the rising sewer main between its pumping station in Saltcoats, Ayrshire and the treatment works in Stevenson. This project comes on the back of several pipe bursts and spot repairs since 2022, caused by the aging infrastructure. Contracted to support the delivery of the works on site was George Leslie, the Scottish based civil engineering contractor.
A particularly problematic section of the pipeline was located underneath the Stevenson Burn watercourse, which runs alongside a nature reserve and caravan park.
Speaking about the project, Allan Ralston, Project Manager at George Leslie, said: “To replace the old pipeline at this section, our proposed plan of works involved sinking two cofferdams, one either side of the watercourse and 70m apart (a drive pit and reception pit) and installing a large diameter steel by-pass pipework system. We have directionally drilled underneath the watercourse, using a 914mm diameter steel sleeve. Our teams will then install the new 710 PE pipe and tie-in to the existing network, before decommissioning the old pipeline.”
To facilitate the safe delivery of the project, an extensive series of temporary works was required, including a temporary bridge to provide access across the watercourse for plant, materials and equipment, as well as groundworks for the various cofferdams and excavations. Following recommendations by the drilling contractor, the drive pit had to be excavated to a depth of 10m – a minimum of 2m underneath the riverbed to avoid water ingress.
Our solution
As a result, George Leslie chose to turn to us for support. Allan continued: “We’d actually recently worked with Mabey Hire on a very similar project in nearby Stewarton, which also involved a directional drill and an 8m deep excavation. It was a positive experience working with the team, with great levels of engagement and quality equipment that was easy to work with. As such, we chose to work with them again on this project, with our site team’s familiarity with using Mabey Hire’s groundworks kit at these depths proving useful.”
In addition to the temporary access bridge, designed for vehicles up to 26t and formed out of our flat top BeamBridge, spanning 12m, we also designed and supplied a range of groundworks support equipment for the various cofferdams on site, using a combination of Larsen piles, trench sheets and heavy bracing frames.
With multiple excavations required, including the reception and drive pit for the drilling rig and the two tie-in points, the project required a carefully planned phased approach, while the site location also presented challenging ground conditions.
Jamie McLachlan, Associate Sales Director – Scotland at Mabey Hire explained: “As well as the proximity to the watercourse, we were presented with a high-water table, meaning the team had to consider the resulting groundwater levels in the cofferdams. To counteract this, George Leslie installed a de-watering system in the proposed excavation locations. It involved the installation of small-diameter wells (wellpoints), connected to a header pipe and positioned around the perimeter of each cofferdam, with a vacuum pump system then used to lower the groundwater level.
“We also worked with the pile supplier to provide a sealant pre-delivery, to alleviate groundwater ingress. Through a combination of early engagement and excellent collaboration with George Leslie and the wider team, we were able to ensure that this didn’t cause issues or delays to the project timeline.”
Our kit remains on site, with the directional drilling commencing at the end of April 2026.
Get in touchProject images
Related news and projects
Give us a call
For all project specific design and technical enquiries, please contact your local service team.
Send us an email
If you want to talk to us about your project, send us an email and a brief outline of how we can help and we’ll be in touch.
[email protected]
“We’d actually recently worked with Mabey Hire on a very similar project in nearby Stewarton. It was a positive experience working with the team, with great levels of engagement and quality equipment that was easy to work with. As such, we chose to work with them again on this project, with our site team’s familiarity with using Mabey Hire’s groundworks kit at these depths proving useful.”