Southern Gas Networks (SGN) – Lower Thames Crossing (LTC)

 Project Outline

The Dartford Crossing is one of the UKs most vital roads, but also one of its most unreliable. The Lower Thames Crossing (LTC) will ease congestion, improving journeys for millions of people every year and will open up new opportunities and economic growth for business.

Long O Donnell (LOD) were commissioned to support this development by providing detailed design services in order to lay a new gas main (800mm diameter HDPE) as the existing gas main needed diverting to accommodate the route of the new carriageway. A two phased approach to laying the gas main was initially taken subject to further ground investigation works conducted by LTC. The detailed design, encompassed electrical/ instrumentation, mechanical, and civil specifications.

LOD were tasked with activities throughout the project lifecycle, from diversion to abandonment, adhering to current design and construction regulations. Key responsibilities included creating a comprehensive design for asset diversion, generating a material take-off list, considering new connections, and ensuring compliance with IGEM and SGN standards.

LOD successfully produced all necessary designs, drawings, documentation, specifications, and calculations, including gas main routing drawings and protection measures. Additionally, they created a works information package for the main works contract tender document and demonstrated appropriate resources for timely design completion. The detailed design aligned with LTC’s then-current Detailed Design Scope of Works document and met Highways England’s requirements.

key statistics


Southern Gas Networks (SGN)
Project Value

Project Value

£9 million
Project Duration

Project Duration

18 Months