GSNE Services is pleased to support the proposed development at 21–23 Lexington Drive, Bella Vista NSW — a mixed-use project involving demolition of the existing structures and construction of a new commercial building with one level of basement parking.
The site sits within The Hills Shire Council Local Government Area, approximately 35 km north-west of the Sydney CBD. A key engineering consideration is the North West Link railway tunnel corridor — approximately 33.5 m wide — which traverses diagonally across the western portion of the site.
Project & Site Context
The twin tunnels are approximately 7 m in diameter, with the top of tunnel at about RL 65.5 m — roughly 14 m below the proposed basement level. A Bulk Excavation Level of approximately RL 76.50 m AHD was adopted to allow for basement slab and column footing construction.
GSNE Services Scope
GSNE has provided a broad range of geotechnical and hydrogeological engineering services, from development approval through construction-phase support:
- Geotechnical site investigation and subsurface ground model development.
- Dewatering Management Plan — groundwater monitoring, seepage assessment, water quality, discharge guidance and drawdown.
- Groundwater seepage modelling for the drained basement, including inflow estimation and drawdown effects.
- Engineering Impact Assessment on the Sydney Metro tunnel infrastructure.
- Engineering Risk Assessment covering geotechnical hazards, surcharge loading, ground movement and tunnel lining impacts.
- Geotechnical Monitoring Plan with baseline documentation and early-warning trigger levels.
Numerical Modelling & Impact Assessment
A finite element model was developed to simulate staged excavation, retaining system, dewatering and final building loads above the tunnels. This allowed quantitative assessment of ground movement and stress changes around the tunnel lining, confirming impacts remain within acceptable performance criteria.
Groundwater Seepage Assessment
Seepage modelling around the proposed drained basement provided robust inflow estimates and confirmed that off-site drawdown effects on neighbouring assets — including the metro corridor — would remain negligible. The outputs directly informed the Dewatering Management Plan and discharge guidance.
The Proposed Development
Outcome & Ongoing Support
The project demonstrates GSNE Services’ capability in delivering integrated geotechnical, groundwater, numerical modelling, impact assessment and monitoring services for developments located near sensitive rail infrastructure.
GSNE Services continues to provide construction-phase geotechnical support — monitoring review, hold-point advice, groundwater management and technical input during excavation and basement construction.
Boutique expertise, big-firm experience. If your project sits near sensitive rail, road or utility infrastructure, GSNE can support it from DA stage through to construction.