The Challenge
The principal engineering challenge was installing the new 600 mm gas pipeline beneath the existing cryogenic LNG infrastructure without disrupting or compromising its operation.
Conventional open-cut construction in the vicinity of the LNG pipeline would have introduced significant excavation, ground disturbance and interface risks.
Horizontal Directional Drilling provided a controlled trenchless solution that allowed the new pipeline to pass safely beneath the existing infrastructure while minimising surface disturbance.
The project presented several additional challenges:
- Construction across heavily contaminated former refinery land.
- Working in close proximity to critical operational energy infrastructure.
- Strict environmental controls and monitoring requirements.
- Protection of sensitive habitats, including those associated with water voles and great crested newts.
- Management of both HDD and conventional pipeline construction activities within a single coordinated programme.
- Installation and pullback of a large-diameter, pre-welded pipeline string.
The HDD Solution
Stockton designed and delivered an approximately 1,100 m HDD crossing using a 250-tonne maxi HDD rig.
The crossing enabled the new pipeline to pass beneath the existing cryogenic LNG infrastructure without requiring excavation immediately adjacent to it.
Following completion and preparation of the bore, the 600 mm pipeline string was pre-welded, inspected and pressure tested before being pulled through the completed HDD alignment.
Careful control of drilling parameters, bore geometry and pipeline installation operations was essential throughout the crossing.
The trenchless methodology significantly reduced disturbance to the existing infrastructure and surrounding ground compared with an open-cut solution and minimised the potential for post-construction settlement associated with major excavation.
Project Scope
Stockton's scope included:
- Approximately 2 km of 600 mm welded gas pipeline installation.
- Approximately 1,100 m Horizontal Directional Drill.
- Deployment of a 250-tonne maxi HDD rig.
- Installation of the pre-welded and pressure-tested 600 mm pipeline string.
- Open-cut pipeline construction.
- Construction of an AGI pigging facility.
- Site mobilisation and construction management.
- Health, safety and environmental management.
- Environmental monitoring and mitigation.
- Coordination with the client, designers and other project stakeholders.
Environmental Management
Environmental management was a major consideration throughout the project.
The pipeline route crossed a heavily contaminated brownfield site associated with the area's former refinery operations. This required careful planning and control of excavation, drilling and construction activities.
The site also contained environmentally sensitive habitats, including areas associated with water voles and great crested newts.
Stockton implemented a comprehensive environmental management system that was independently audited throughout the project.
A detailed environmental assessment was undertaken before construction commenced, and a dedicated Stockton environmental advisor remained on site during the works, supported by a specialist ecologist.
Environmental controls were incorporated directly into construction planning rather than treated as a separate activity. This allowed the engineering and environmental teams to work together to manage contaminated ground, sensitive habitats and the requirements of the relevant stakeholders and authorities.
Project Outcome
The project demonstrated Stockton's ability to deliver complex large-diameter pipeline installations in challenging environments where trenchless engineering provides a significant advantage.
The successful HDD crossing enabled the 600 mm gas pipeline to pass beneath critical cryogenic LNG infrastructure over an approximately 1.1 km alignment, while avoiding major excavation around the existing asset.
The project also demonstrated Stockton's capability to integrate specialist HDD operations with conventional pipeline construction, environmental management and overall project delivery.
Specialist Trenchless and Pipeline Delivery
The Isle of Grain project is an example of how Stockton Group combines specialist trenchless engineering with conventional pipeline construction and project management to overcome complex infrastructure, environmental and ground constraints.
From long-distance HDD crossings and critical asset interfaces to complete pipeline installation, Stockton provides the engineering experience, equipment and site capability required to deliver challenging infrastructure projects safely and efficiently.
Planning a challenging HDD, trenchless or pipeline project?
Contact Stockton Group to discuss how we can support your next infrastructure project.
