Project Background and Objectives
Wycombe Marsh Substation, located on wrights Meadow Road, High Wycombe, required construction of a new 11kV and 33kV switch house within an operational electrical substation. The objective was to deliver a robust piled foundation solution to support the new structure while maintaining safe operation of live electrical infrastructure throughout the works.
The scheme demanded strict control of vibration, sequencing, and access due to the presence of live assets and ongoing network operations.
Project Scope and SPI Involvement
SPI Piling Ltd, was appointed by Sienna Construction Ltd to design, supply and install 20No steel tubular bearing piles, 324mm diameter CHS, approximately 15m long.
The piles were designed to support switch room service loads including vertical dead and imposed loads, and horizontal wind loads. The works incuded:
- Mobilisation and set-up within a live substation.
- Pitching and driving of 20No bearing piles
- Impact driving to achieve required set.
- Dynamic load testing (CAPWAP)
- Welding of pile extensions where required
- Cutting piles to final level.
All works were completed within the 2 week programme window.
Methodology and Execution
Installation was undertaken using a 35T excavator fitted with a side-grip vibratory hammer for primary driving, followed by a DX25 impact hammer to achieve final set and facilitate dynamic load testing.
Works were carefully sequenced to accommodate two separate electrical bays, with one bay remaining live at all times. Piling was undertaken in controlled phases, with formal permit-to-work systems implemented for each zone change.
Dynamic load testing was carried out on selected piles to verify performance against the 180kN design load, with re-driving and welded extensions undertaken where required to achieve compliance.
Safety, Quality & Risk Management
Operating within a live SSEN substation required stringent control measures. SPI Piling Ltd, worked under a daily permit-to-work system, with physical segregation between live and isolated bays.
Key controls included:
- Controlled piling platform certification.
- Vibration monitoring requirements.
- Exclusion zones and lift planning.
- Hot works permits for cutting and welding.
- Detailed RAMS and lift plans.
All personnel were inducted and briefed on live asset boundaries and emergency procedures prior to commencement.
Challenges & Adaptive Collaboration
The primary challenge was installing bearing piles within an operational substation while maintaining continuous power in one bay. Close coordination with Sienna Construction Ltd and the on-site SSEN representative ensured safe isolation sequencing and strict adherence to working limits.
Where dynamic testing indicated additional capacity was required, SPI Piling Ltd, implemented welded extensions and re-testing without impacting the overall programme.
Outcomes & Value Delivered
SPI Piling Ltd, successfully delivered 20nr compliant bearing piles, verified through dynamic testing, within the agreed programme and budget (£68,154.83 excl. VAT).
The foundation works provided a structurally sound platform for the new switch house while maintaining operational integrity of the substation.
Lessons Learned & Strategic Strengths
This project reinforced SPI Piling’s capability in:
- Live substation working environments.
- Controlled vibration piling adjacent to sensitive assets.
- Adaptive sequencing within restricted footprints.
- Integrated safety and permit-led delivery.
The scheme demonstrated SPI Piling’s, ability to combine technical expertise with disciplined operational control.
Summary
The Wycombe Marsh Substation project highlights SPI Piling’s expertise in delivering steel bearing pile solutions within live electrical infrastructure. Through meticulous planning, strict safety management, and collaborative working, SPI Piling Ltd, completed the works safely, on programme, and to the required quality standards—reinforcing its position as a trusted specialist contractor for critical infrastructure projects.
