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Commercial
Diagnostech was engaged to design, manage, and deliver critical remedial works to a deteriorated underground electrical substation.
2025 ACRA Award for Small project under $500,000
Diagnostech was engaged to design, manage, and deliver critical remedial works to a deteriorated underground electrical substation located beneath the driveway of a commercial property at 157 Walker Street, North Sydney.
Diagnostech was engaged to manage all technical investigations, liaise with Ausgrid, design an approved remedial scope, and oversee the works through to completion.
Here’s how the project rolled out.
Situation
The substation’s concrete roof had suffered extensive spalling and corrosion caused by long-term water ingress through a buried steel hatch. The hatch, covered by asphalt, prevented proper drainage and created ongoing leakage into the chamber. Ausgrid, responsible for electrical infrastructure, identified the defects and required the building owner to rectify them under supervision.
Diagnostech was engaged to manage all technical investigations, liaise with Ausgrid, design an approved remedial scope, and oversee the works through to completion.
Goals
The project’s primary objectives were to:
Restore the structural integrity of the substation roof slab
Prevent future water ingress and corrosion through a permanent waterproofing solution
Achieve Ausgrid approval for ongoing access and maintenance
Ensure all works were undertaken safely within a confined space and under live electrical conditions
Engagement included:
Detailed inspections and structural condition assessments
Coordination with Ausgrid for safe access, supervision, and approval of methods
Design and documentation of remedial works including concrete repair, waterproofing, and cathodic protection
Full superintendent services including tendering, cost management, and site supervision
Challenges
The project presented several technical and logistical challenges.
1. Structural Safety During Works
To prevent collapse during roof removal, a temporary timber roof and PVC membrane were installed to protect the chamber while the concrete hob and new hatch were constructed.
2. Live Electrical Environment
All work within the chamber occurred under Ausgrid supervision due to the proximity of live transformers. Conductive materials were prohibited, requiring specialised non-conductive equipment and strict confined-space protocols. Diagnostech coordinated all work sequences and schedules to align with Ausgrid’s attendance.
3. Confined Space Access
The confined chamber required confined-space permits, air quality monitoring, and arc-rated PPE for all personnel. Diagnostech ensured continuous supervision and compliance throughout construction.
Solution
Diagnostech developed a comprehensive remedial strategy that balanced safety, technical requirements, and Ausgrid’s operational needs.
This included:
Structural Remediation
Removal of delaminated concrete and application of repair mortars
Installation of cathodic protection to beams to mitigate future corrosion
Strengthening of the concrete roof slab to restore full load-bearing capacity
Waterproofing and Drainage
Construction of a reinforced concrete hob around the hatch opening
Application of a bitumen-based waterproofing system to the slab surface
Replacement of the steel hatch, waterproofed with a liquid-applied membrane by Ausgrid
Asphalt reinstated to ensure effective surface drainage and long-term durability
Safety and Compliance
All confined-space works were completed under Ausgrid supervision with continuous monitoring
Non-conductive tools and barriers ensured compliance with live electrical safety requirements
Diagnostech managed environmental protection measures to prevent contamination during demolition and reinstatement
Results
The project was successfully completed in May 2024, achieving all safety, technical, and compliance goals.
Diagnostech’s design resolution not only restored the structural integrity of the substation but also resolved a long-standing dispute between the building owner and Ausgrid.
Structural Integrity Restored
Concrete repairs and cathodic protection reinstated the strength of the substation roof and supporting beams, eliminating safety risks.
Waterproofing Performance Improved
The new waterproofing system, combined with redesigned surface drainage, ensures the chamber remains watertight under all conditions.
Operational Compliance Achieved
Ausgrid accepted the final design and certified the chamber as compliant for ongoing maintenance access.
Asset Value Protected
By resolving Ausgrid’s claims and certifying the structure’s compliance, Diagnostech safeguarded the building’s market value and future saleability.
Project Highlights:
Complex confined-space remediation under live electrical conditions
Seamless coordination between Diagnostech, Ausgrid, JLL, and GPT Group
Durable waterproofing design balancing drainage and access requirements
Completion on time despite extensive design negotiations
Delivered improved structural resilience and long-term compliance assurance
