Groundwater and Drainage Issues

Managing Subsurface Water Risks

Groundwater and poor drainage pose significant risks in Sydney, including basement flooding, soil liquefaction, and slope instability. Proactive management is essential in flood-prone regions (e.g., Hawkesbury-Nepean Valley) and coastal suburbs where tidal fluctuations influence water tables.

Assessment and Solutions

Effective site assessment and drainage solutions are essential for managing groundwater challenges.

Groundwater Evaluation
- Installing piezometers to monitor seasonal water table variations.
- Conducting infiltration tests to determine aquifer permeability (hydraulic conductivity).
Drainage Design
- Subsurface Drains: Drainage to divert groundwater from foundations.
- Stormwater Integration: Compliant with NSW BASIX requirements for sustainable water management.
Dewatering Systems
- Drainage systems for shallow excavations in sandy soils (e.g., Botany).
- Dewatering for basements in high-water-table zones (e.g., Parramatta).

Sydney-Specific Challenges

Sydney’s diverse terrain presents unique construction challenges.

Coastal Aquifers

Saltwater intrusion in areas like Cronulla requires corrosion-resistant materials.
Expansive Clays

Seasonal moisture changes in Western Sydney demand subsoil drainage to mitigate heave.
Urban Infill

Limited permeability in paved areas increases runoff, requiring infiltration trenches or raingardens.

Compliance

Strict regulations govern groundwater management in Sydney.

NSW Aquifer Interference Policy

Licensing for large-scale groundwater extraction.
AS 2870 (Residential Slabs and Footings)

Requires drainage plans for reactive soil sites.

Deliverables

Comprehensive documentation ensures compliance and quality assurance.

Hydrogeological reports with contour maps of water tables.
Council-approved drainage and dewatering plans.

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