Projects

Trawsfynydd Substation For National Grid.

Overview

Location

Trawsfynydd

Value

£800k

Status

Ongoing

Client

The Challenge.

ACS was appointed by National Grid to deliver critical civil engineering works at Trawsfynydd Substation in North Wales, supporting the installation of new transformer infrastructure. The project formed part of a wider upgrade programme within a live operational environment, requiring careful coordination with ongoing substation activities and fixed outage dates.

The project presented several technical and logistical challenges:

Live substation environment requiring strict adherence to operational constraints
Remote location and restricted access, impacting logistics and sequencing
Adverse weather conditions, affecting productivity and programme certainty
Complex ground conditions, with granite bedrock encountered at shallow depth (~300mm), requiring extensive mechanical breaking
Fixed programme constraints, linked to transformer delivery and outage windows
Environmental restrictions, including working limitations during low temperatures and ecological considerations

Scope of Works

ACS delivered a full turnkey civils package, including:

Establishment of site compound and welfare facilities
Reinforced concrete transformer bunds and plinths
Associated drainage systems and oil interceptor installation
Foundations for lighting columns and ancillary infrastructure
Installation of precast duct troughs, cable ducting and earthing systems
Trough crossing points and final surfacing with chippings

ACS also undertook temporary works design, including platform access solutions and crane formation bases, ensuring safe and efficient delivery.

Our Solution.

ACS adopted a proactive and collaborative delivery approach to mitigate risks and maintain programme certainty:

Early intervention and risk identification, including site investigations to confirm shallow granite formation and enable cost and programme adjustments with the client
Value engineering, relocating ancillary foundations and lighting columns in agreement with National Grid designers to reduce excavation and minimise disruption
Design adaptation, revising ducting layouts where existing fibre optic infrastructure was identified, ensuring protection of critical assets
Bespoke engineering solutions, including the design and manufacture of trough crossings to align with existing infrastructure
Close stakeholder coordination, working alongside National Grid planners, site teams and designers to manage interfaces and live operational constraints

Outcomes & Results

Programme certainty: Transformer bund constructed, tested and handed over within agreed programme
Commercial performance: Delivered within target cost despite challenging ground conditions
Quality: High-quality concrete works achieved, with only minor NCRs recorded
Safety: ~10,300 hours worked with zero reportable incidents
Client satisfaction: Ongoing discussions with National Grid Special Projects team for further works under constrained programmes
Operational readiness: Timely demobilisation enabled seamless transformer installation, with return works planned for the Portable Relay Room (PRR)

Social Value & Environmental Impact

Local engagement: Use of local suppliers, including engagement of a regional contractor for upcoming PRR works
Sustainable practices: Approximately 75% of excavated material diverted from landfill, including recycling of granite off-site
Environmental protection: Implementation of exclusion zones to protect nesting birds identified on site
Local economic contribution: Use of local facilities and services throughout the project duration

Key Metrics

Concrete placed: ~250m³
Excavation: ~600m³ (predominantly rock)
Programme duration: 28 weeks
Average workforce: 8 operatives
Waste diverted from landfill: ~75%
Safety performance: 10,300+ hours, zero reportable incidents

Why This Project Stands Out.

Demonstrates ACS’s ability to deliver complex civils packages within live substation environments
Reinforces a strong track record with National Grid, securing repeat opportunities through performance
Showcases full lifecycle delivery, from early site investigation through to installation readiness
Highlights the strength of in-house expertise and experienced delivery teams in highly regulated infrastructure sectors

The Hinkley Connection Project is a new 57 km high-voltage electricity line that will connect six million homes and businesses to new sources of low carbon energy. It will help the UK to meet ambitious targets to achieve net zero by 2050. The Sandford substation – one of 300 substations throughout England and Wales - is at the heart of the project.