Stormwater Management for New Homes — What Western Sydney Councils Require
Every new home, duplex, and development in Western Sydney must manage stormwater runoff. councils require that the stormwater leaving your property after development is no greater (in peak flow) than before development. Since a new home replaces permeable garden with impervious roof, driveway, and paved areas, you need a stormwater management system to comply.
Buildana (Lic. 487805C) includes stormwater management in every project. Here is what you need to know about requirements, systems, and costs.
Why Stormwater Management Matters on Your Block
Before development, a typical 600 sqm block in Western Sydney absorbs approximately 40–60% of rainfall through garden, lawn, and permeable ground. After a new home is built, impervious surfaces (roof, driveway, paths, patios) typically cover 50–70% of the block. This means significantly more rainwater runs off the block during storms.
This additional runoff causes problems downstream — flooding of neighbouring properties, overloading of council stormwater pipes, erosion of creek banks, and water quality degradation. Councils across Western Sydney — particularly Fairfield, Liverpool, and Canterbury-Bankstown, which have flood-prone waterways — take stormwater compliance seriously.
Every CDC and DA application must include a stormwater management plan prepared by a hydraulic engineer. Without it, your application will not be approved.
On-Site Detention (OSD) Systems
The most common stormwater management solution for residential sites in Western Sydney is an On-Site Detention (OSD) system. An OSD system temporarily stores stormwater on your property and releases it slowly — matching the pre-development flow rate.
Types of OSD systems:
• Below-ground tank: A concrete or polyethylene tank buried in the yard or under the driveway. Water enters during storms and drains out through a restricted outlet over several hours. Size: 2,000–10,000 litres depending on calculation.
• Above-ground detention: A grassed depression or swale that fills during heavy rain and drains slowly. Cheaper to construct but uses garden area.
• Permeable paving: Driveways and paths built with permeable pavers that allow water to infiltrate through the surface and into a gravel base underneath. Acts as both a finished surface and water storage.
• Rainwater tank with detention: A combination rainwater tank that stores water for household use (BASIX requirement) with an additional detention volume that fills during storms and slowly releases. This serves dual purposes — water conservation and stormwater management — in one unit.
OSD sizing is calculated by a hydraulic engineer based on your specific block, the impervious area created by the development, and the council's specific design requirements (typically a 1-in-100-year storm event).
Council-Specific Requirements in Western Sydney
Each council has its own stormwater management policy:
• Fairfield City Council: Requires OSD for all new developments that increase impervious area. Uses a site storage requirement (SSR) of approximately 470 m³/ha — meaning your block needs to store approximately 28 cubic metres (28,000 litres) of stormwater per 600 sqm. Permissible discharge rate is typically limited to the pre-development flow.
• Liverpool City Council: Requires OSD per the Liverpool DCP. More stringent in flood-prone areas near the Georges River. Some areas require additional freeboard above flood planning levels.
• Canterbury-Bankstown: Requires OSD plus water quality treatment (gross pollutant traps) for medium-density developments. Single dwellings require OSD only.
• Cumberland Council: Requires OSD for all new development. Uses the Upper Parramatta River Catchment Trust technical guidelines.
• Blacktown City Council: Requires OSD plus WSUD (Water Sensitive Urban Design) measures for larger developments.
Buildana's hydraulic engineer designs the stormwater system for your specific block and council during the documentation phase — well before construction begins.
Costs and What Is Included in Your Build
Stormwater management costs for a new home or duplex in Western Sydney:
• Hydraulic engineering design: $2,500–$5,000 • Below-ground OSD tank (3,000–8,000L): $4,000–$10,000 supplied and installed • Connection to council stormwater system: $2,000–$5,000 • Permeable paving (driveway alternative): $80–$120/sqm (compared to $60–$80/sqm for standard concrete) • Combination rainwater/detention tank: $5,000–$12,000 • Gross pollutant trap (required for larger developments): $3,000–$6,000
Total stormwater management cost: $8,500–$25,000 depending on block size, development type, and council requirements.
Buildana includes stormwater management in every fixed-price contract. The hydraulic design, OSD system, and all connections are covered — no provisional sums or variations for 'unexpected stormwater requirements.'
For more on what is included in a new home build, visit /homes/custom-homes. For the full construction process, see /construction/site-earthworks. Contact Buildana at /contact for a free site assessment.
