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Project: Under-Road Utility Crossing at Wrenhall – Eastern Green Link 2 (EGL2)

Key Project Details

Client:

  • NKT & BAM

Project: EGL2 Under-Road Utility Crossing

Location: Wrenhall

Start date:

  • December 2026

End Date

Duration:

  • Ongoing

Contract Value:

  • £2,500,000

The Challenge

As part of the Eastern Green Link 2 (EGL2) programme, Aaron Engineering was required to design and install a strategic under-road utility crossing (URX) at Wrenhall to support the full HV cable route delivery. The crossing forms a critical interface where a newly installed 400kV cable route intersects new road infrastructure, existing 132kV utilities, and multiple telecom and water services—significant amounts of which were uncharted and had to be safely worked around. The project demanded careful integration of civil, electrical, and utility protection design to ensure compliance with National Grid Technical Specifications (NGTS 3.05.07), ENA-TS-97-1, and manufacturer-specific installation standards whilst maintaining operational safety and long-term maintainability. Works required protection of the 400kV cable circuits, maintenance of safe clearances from existing utilities, and provision of future-proofing through spare ducts for potential 132kV cable relocation.

What We Did

Aaron Engineering was procured to deliver comprehensive URX design and construction works, valued at £2.5 million. As part of our package, we carried out the design to facilitate the works, with key specifications and innovations including:

Key Design Features:

Precast Trough Systems – FLI Precast Troughs Type A (300×1200 internal) and Type B, providing segregated containment for the 400kV circuits with integral lifting points; lids weighing 1500kg for durability and security

Concrete Surround Solutions:

  • Where cover was <685mm, ducts surrounded with C20/25 concrete in accordance with NGTS 3.05.07
  • Where installation was undertaken outside immediate highway parameters, alternative materials used to comply: Cement Bound Sand (CBS) meeting ENA-TS-97-1 for thermal resistivity
  • Centriforce Stokbord Type A, Class 1 protection covers with marked “Danger – Electric Cable Below” warning
  • 150mm wide marker tape installed above protection

Bridging Structure – Where the new cable route crossed shallow-buried existing 132kV circuits, 3-No precast bridging slab system installed to provide mechanical protection and load transfer

Construction Methodology:

  1. Site Preparation – Utilities confirmed using drawings, GPR, CAT & Genny scanning, and trial holes; Permit to Dig issued; topsoil stripped and regraded; geotextile installed; 6F2 stone placed and compacted; track mats, fencing, and traffic management (half-road closure, GS6 controls) installed
  2. Ducting Installation – Utility checks and Permit to Dig completed; vac-ex excavation for safety in live-road environment; temporary works and safe access established; ducts, spacers, and draw ropes installed to design requirements; concrete surround and curing completed; cable tiles, warning tape, and backfill placed and compacted
  3. Bridging Existing 132kV Cables – Vac-ex excavation under strict permit controls; reinforced bridging system constructed including concrete blinding, precast abutments, and bridging slabs; controlled layer backfilling with maintained electrical safety clearances
  4. Concrete Trough Installation – Utility checks and Permit to Dig completed; excavation to formation level; screed bedding installed and approved; precast troughs positioned, interlocked, sealed, and backfilled to match surrounding ground levels

The Outcome

  • Under-road crossing completed successfully, delivering compliant 400kV route
  • Zero utility strikes achieved through rigorous utility detection and protection protocols
  • All precast trough systems installed with 1500kg lids securing containment
  • C20/25 concrete and CBS protection installed to full specification compliance
  • Bridging system successfully protecting existing 132kV circuits with maintained clearances
  • Spare ducts installed for future 132kV cable relocation capability
  • Integrated DTS monitoring capability delivered
  • Programme certainty achieved for EGL2 continuation with duct, troughing, and steel installation to follow
  • Future-proof utility corridor established beneath new road infrastructure

Added Value

This project demonstrates Aaron Engineering’s capability to deliver complex, multi-disciplinary URX works that integrate design and construction delivery. By undertaking the design as well as construction, our teams provided an integrated solution balancing technical compliance with NGTS and ENA standards, protection of existing critical utilities, and future-proofing for potential cable relocations. The innovative use of segregated precast trough systems, combined with graduated protection solutions (concrete surround, CBS, and bridging slabs), ensured robust protection of the 400kV route whilst maintaining safe clearances from existing 132kV, telecom, and water services. The achievement of zero utility strikes across all detection and excavation activities, supported by rigorous vac-ex methodology and permit controls, demonstrates our commitment to safe, compliant delivery on critical infrastructure programmes.