The tidal location of the river created a significant flood risk and required careful environmental planning. Complex signal structures on constrained bridge crossings introduced additional engineering and approval challenges, while the proximity to a dual carriageway demanded strict traffic management. The site’s ecological sensitivity, including nesting birds and protected wildlife, limited construction activities, alongside the need to account for structural load and thermal expansion. The exposed installation also presented risks of vandalism and unauthorised access.

• Special Engineering Difficulties (SED) included constrained bridge crossings requiring Horizontal Directional Drilling (HDD) beneath roads
• Potential for flooding due to the river’s tidal nature necessitated placing the pipe bridge above the bridge soffit and within the protection of the Thames Estuary flood defences. Polytetrafluoroethylene (PTFE) sliding bearings and expansion joints were used to accommodate thermal and structural movement without compromising flood resilience

Construction couldn’t be completed in one phase due to early commissioning requirements, so works were staggered and required complex sequencing from temporary to permanent systems. The project involved specialist 132kV equipment and precise coordination with existing infrastructure, alongside significant site constraints including water ingress, depth limits, pipeline crossings, and a congested industrial route.

• JSM constructed a dedicated 11kV substation, a 132kV dual transformer bund area, and an iDNO-adoptable 132kV switchgear compound
• Temporary power was required during substation works, resulting in 1.6km of 11kV cables being installed. This prevented delays to the client’s energisation requirements
• The Special Engineering Difficulties included bypassing a bridge. Horizontal Directional Drilling (HDD) was used to ensure no disruption to traffic