Project Overview
In 2023, Electrafence undertook the design and installation of a new perimeter security system for the National Grid substation at Aberthaw Power Station. This comprehensive project involved installing a site perimeter fence to National Grid standards around two separate substations within the power station complex, all before the demolition of the old power station. The site posed several challenges, including numerous buried services with no existing records, potential contaminated ground, and a flood risk to 1.2m at a 1:1000-year event.
Description
- New Compounds: Independent fencing around the 132KV and 275KV substations.
- Control Systems: Installation of new control systems to both sites. Also ensuring that cabinets and were in flood-protected areas.
- Flood Risk Zone: Addressing the flood risk throughout the design and build.
- Contaminated Ground: Consideration of potential ground contamination during installation.
Challenges
- Numerous unknown hazards in the ground, including buried cables and pipes, required the use of previous records and ground radar mapping to locate and avoid them.
- Poor ground conditions - characterised by sandy soil with less than 50kN ground bearing pressure.
- The project site was located in a flood risk zone, requiring careful planning and design.
- There was a potential for contaminated ground, requiring thorough site assessments.
- The terrain was difficult. Land ownership boundaries were also complicated which had to be navigated.
- Reducing carbon use on site was a priority.
Approaches to Overcome Challenges
- Designing the Fence:
- Solution: The fence design incorporated all available data to avoid existing underground services. Given the flood risk, post foundations were subject to a gravity design and manufactured offsite with a lower carbon CIIIA concrete mix instead of traditional Portland cement.
- Outcome: Pre-cast bases were delivered to the site for rapid installation using a just-in-time process, allowing for the avoidance of services by offsetting foundations and post voids. The pre-cast solution enabled installation during winter conditions that would have prohibited wet-cast concrete use, maintaining the installation schedule. Where services couldn't be avoided, rafts were designed to minimise load on cables by reducing foundation depth.
- Adapting to Significant Changes:
- Challenge: During construction, other contractors faced issues with poor ground conditions, unable to drive piles for a fire reserve water tank, necessitating the tank's relocation to the fence line.
- Solution: Construction drawings were altered to divert the fence and electric fence around the new tank location. This required a different approach, constructing a one-piece raft to avoid buried water pipes, French drains, and other services within a reduced working area.
Products
- Palisade fence: Supplied to National Grid standard by Paramount.
- Manual Sliding Gates: Electrified manual gate access control.
- National Grid Standard Fencing: All fencing adopted to meet stringent National Grid standards.
- Electric Fencing: Supplied by Gallaghers ensuring top-level security measures and compliance to National Grid standards and access control.
- Cill-Lock System: Utilised for constructing cill beams efficiently in limited space.
Feedback
The project received positive feedback, highlighting the efficiency and effectiveness of the implemented solutions:
