Contact

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

Key Project Details

Client:

  • NKT & BAM

Start date:

  • December 2025

End date:

  • Ongoing

Duration:

  • TBC

Value:

  • £2.5m

The Challenge

As part of the Eastern Green Link 2 (EGL2) programme, Aaron Engineering Group was required to install a strategic under-road utility crossing (URX) at Wrenhall to support the full HV cable route delivery by BAM. The crossing formed a critical interface where the 400kV cable route intersected new road infrastructure, existing 132kV utilities, and multiple telecoms and water services—significant amounts of which were uncharted and had to be safely worked around. The project required careful integration of civil, electrical, and utility protection design to ensure compliance with National Grid Technical Specifications (NGTS) and manufacturer-specific installation standards whilst maintaining operational safety and long-term maintainability. The under-road crossing needed to protect newly installed 400kV HVAC cable circuits as they passed beneath a busy carriageway, maintaining safe clearances from existing utilities whilst providing future-proofing through spare ducts for potential 132kV cable relocation.

What We Did

Aaron Engineering Group delivered comprehensive design and construction works for this £2.5 million project between December 2026 and ongoing completion. As part of our package, we carried out the design to facilitate the works, with key design features including:

Precast Trough Systems – designed and adopted 17 precast troughs Type A (300×1200 internal) and Type B, providing segregated containment for the 400kV circuits with integral lifting points, with lids weighing 1500kg, ensuring durability and security

Concrete Surround – where cover was ≤685mm, ducts were surrounded with C20/25 concrete in accordance with NGTS 3.06.07; where installation was undertaken outside highway parameters, Cement Bound Sand (CBS) meeting ENA-TS-87-1 was used, offering thermal resistivity with protection covers and marker tape

Bridging Structure – where the new cable route crossed shallow-buried existing 132kV circuits, a 3-tonne reinforced bridging slab system was installed to provide mechanical protection and load transfer

Our construction methodology included:

  1. Site Preparation – utilities confirmed using drawings, GPR, CAT & Genny scanning; Permit to Dig obtained; excavation completed and regraded; geotextile installed; 6F2 stone placed and compacted; track mats and fencing erected; traffic management measures on New Road
  2. Ducting Installation – utility checks and Permit to Dig completed; trenches excavated using vac-ex for safety; temporary works established; ducts, spacers, and draw ropes installed to design requirements; concrete surround and curing completed; cable tiles, warning tape, and backfill placed
  3. Bridging Existing 132kV Cables – vac-ex excavation under strict permit controls; reinforced bridging system installed including concrete binding and bridging slabs; backfilling completed in controlled layers
  4. Concrete Trough Installation – utility checks and Permit to Dig completed; excavation reached formation level; screed bedding installed; precast troughs positioned, interlocked, sealed, and backfilled to match surrounding ground levels

The Outcome

  • Strategic under-road crossing completed successfully, delivering a compliant 400kV route
  • Zero utility strikes achieved through rigorous detection and protection measures
  • Spare ducts delivered for 132kV works, providing future-proofing capability
  • Robust structural protection integrated including 3-tonne bridging slab system
  • Integrated DTS monitoring and programme certainty maintained for EGL2
  • Operational safety and long-term maintainability ensured
  • Full compliance with NGTS specifications and manufacturer requirements
  • Safe clearances maintained from 132kV circuits, BT and CCTV telecom assets, and water supply

Added Value

This project demonstrates Aaron Engineering Group’s capability to deliver complex, multi-disciplinary infrastructure works that integrate civil engineering, electrical design, and utility protection expertise. By undertaking the design as well as construction, our teams provided an integrated solution that balanced technical compliance with NGTS standards, protection of existing critical utilities, and future-proofing for potential cable relocations. The successful delivery of this critical crossing supports the wider EGL2 programme’s objectives whilst ensuring zero utility strikes and maintaining the operational integrity of existing 132kV networks and essential services.