cofferdam excavation dalmore mill

Double excavation in new residential area

cofferdam-excavation-dalmore-mill-3

Project Overview

Location
Sector Building
Products

Constructing foundations for a vehicle bridge to connect the residents on a new housing development in Midlothian near Edinburgh.

The challenge

Close proximity

One of the cofferdam excavations was located just three metres from an occupied property and in close proximity to underground services. This demanded a highly controlled installation process to prevent ground movement, vibration damage, or service disruption. Mabey Hire designed a temporary works system that maintained excavation stability while minimising impact on surrounding structures.

High water table

The excavations ran alongside the North Esk River, presenting challenges from a high water table and potential water ingress. Effective groundwater management and structural resilience were essential to maintain a safe and dry working area. Mabey Hire’s cofferdam design provided robust containment and stability in these wet ground conditions.

Complex ground conditions

The soil type required the use of an Excavator Mounted Vibrator (EMV) to drive trench sheets into place, adding complexity to the installation process. The equipment had to be carefully managed to avoid excessive vibration near sensitive areas while achieving the necessary sheet depth and interlock. Mabey Hire worked closely with Mulholland Contracts to ensure the shoring system was both practical to install and structurally sound once in position.

Our solution

With an occupied property sitting just three metres away from the second excavation, our customer product specialist worked extremely closely with Mulholland, both on and off site, to assist in the excavation.

Once the first cofferdam was installed, our engineers’ altered the design of the second Cofferdam to avoid existing services and work around the occupied property. Both cofferdams were approximately 20m x 5.0m x 4.5m deep, using 6.0m long M15 interlocking trench sheets, two levels of Multibrace frame with Heavy Duty mechanical bracing struts.

View Multibrace
cofferdam excavation dalmore mill
cofferdam excavation dalmore mill

However, the second cofferdam had to be modified to accommodate existing foundations and services. The sequencing of construction of the cofferdams resulted in over 200 6m M15 piles having to be on site at the one time.

The design was based on pre-driving the trench sheets before installing two levels of frame, the lower of which could be removed once a suitable concrete base had been cast. As the top frame had been positioned at ground level, this allowed Mulholland to construct the bridge abutments, below this frame.

Get in touch

“Our site foreman, Alec Jarret, really appreciated the time spent on site by Mabey Hire to successfully construct the desired cofferdam.”

Raymond Burns
Contracts Manager/Mulholland

Related news and projects

Contact Phone Number

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

action@mabeyhire.co.uk

Get updates
on our latest news,
solutions and projects