If you are subdividing rural land in the Port Macquarie Hastings LGA, whether splitting off one lot or creating a multi-lot rural residential estate, onsite sewage management is one of the key approval issues you need to resolve before the subdivision can be registered. Each new lot that won’t be connected to town sewer must be demonstrated to be capable of supporting an onsite sewage management system within its boundaries.
Failing to plan for this upfront has derailed many rural subdivision applications in the Hastings region. The time to think about it is at the concept stage, not after the lots are designed and plan lodged.
Why Septic Planning Is Part of Subdivision Approval
In NSW, Port Macquarie Hastings Council assesses subdivision development applications against multiple criteria, including the ability of each lot to accommodate adequate infrastructure. For lots not connected to reticulated sewer, this means demonstrating that:
- Each lot has sufficient area for an onsite sewage management system
- The lot can physically accommodate the system within the required setback distances from all boundaries, waterways, bores, and other constraints
- The soil and site conditions support the proposed system type
- The system can be installed without impacting adjacent lots
This is not assessed at the general DA stage in vague terms, Council will require a detailed onsite sewage management report (OSMM report) for each proposed lot, typically prepared by a qualified environmental consultant or hydraulic engineer.
The OSMM Report: What It Must Show
The Onsite Sewage Management Management (OSMM) report is the technical document that supports the subdivision DA. For each new lot, it must contain:
| Required Element | What It Shows |
|---|---|
| Site assessment including soil profile | Soil suitability for each lot |
| Percolation test results | Actual soil hydraulic conductivity on each lot |
| System type recommendation | What type of system is suitable for that lot’s conditions |
| Indicative system layout | Proposed tank location, land application area position |
| Setback compliance | That the system fits within all required setbacks |
| Design wastewater load | Based on proposed dwelling size/bedroom count |
| Reserve area confirmation | That a 100% reserve area is available |
An OSMM report that simply says “each lot appears to be suitable for an onsite sewage system” without site-specific testing will not satisfy Port Macquarie Hastings Council’s requirements. The report must be based on actual field work on each proposed lot.
Lot Size Minimum Requirements
There is no single minimum lot size for rural lots with onsite sewage management in NSW, it depends on the site’s specific conditions. However, practical experience in the Port Macquarie Hastings region suggests:
| System Type | Minimum Practical Lot Size |
|---|---|
| Conventional septic + absorption trench | 2-4 ha (depending on setbacks and soil) |
| AWTS + drip irrigation | 0.5-1 ha (constrained sites, coastal zone) |
| Composting toilet + greywater | 0.4-1 ha (minimal footprint) |
These are guides, not rules. A highly constrained 2 ha lot near a waterway might not be approvable for any conventional system, while a 1 ha lot with excellent basalt soils and no waterway proximity might accommodate a conventional system comfortably.
The minimum lot size in the Mid North Coast LEP applies for planning purposes, but even if the lot size complies with the LEP minimum, onsite sewage management must be demonstrated to be feasible.
Constraints Commonly Affecting Subdivision in the Hastings Region
Waterway Setbacks
The Hastings River and its tributaries, Camden Haven catchment, Lake Cathie inlet, and numerous unnamed seasonal watercourses impose setback constraints on every lot adjacent to or draining toward them. On low-lying rural land near Wauchope or in the Camden Haven catchment, large portions of some proposed lots can be within the 50 m absorption area setback from waterways.
Bore Locations
If the parent property or adjacent properties have groundwater bores, the 100 m setback from conventional absorption areas to bores may constrain where the system can go on each lot. Careful mapping of all bores (using NSW’s groundwater database) is essential early in the subdivision planning process.
Flood Risk
Large areas of rural land in the Hastings valley near Wauchope are within the mapped flood planning area. Onsite sewage systems in flood-affected areas require specific engineering to prevent system damage and effluent release during flood events. Some severely flood-affected lots may not be supportable for onsite sewage.
Topography and Soil
Sites on steep terrain (common in Comboyne and the Hastings ranges) can require pumped systems to get effluent to a dispersal area on a lower slope, or restrict the available land application area to bench-cut flat areas that are difficult and expensive to create.
Sequential Approval Process for Subdivision
Getting a subdivision with onsite sewage management approved through Port Macquarie Hastings Council follows this sequence:
Stage 1: Pre-DA Consultation Meet with Council’s Development and Environment team to confirm what they require for the OSMM report and to flag any known site constraints. This prevents wasted investment in a detailed report that addresses the wrong issues.
Stage 2: Commission the OSMM Report Engage a qualified environmental consultant or hydraulic engineer to carry out the site assessments and percolation tests on each proposed lot and prepare the report.
Stage 3: Subdivision DA Lodgement Lodge the subdivision DA including the OSMM report. Other elements of the DA (infrastructure services, road access, biodiversity assessment, etc.) are assessed in parallel.
Stage 4: DA Determination Council assesses the DA. Conditions of consent for the subdivision may specify that onsite sewage management must be approved separately before development consent for a dwelling on each lot is issued.
Stage 5: Building and System Approval When a buyer intends to build on a lot, they lodge their own DA/CDC for the dwelling plus the onsite sewage management system, supported by the OSMM report.
What Happens If a Lot Fails the Assessment?
If the OSMM assessment determines that one proposed lot in the subdivision cannot support a viable onsite sewage management system within its boundaries, the options are:
- Redesign the lot boundaries to give that lot more area or better site conditions
- Redesign the subdivision to eliminate the lot that cannot be serviced
- Investigate whether a different (more space-efficient) system type can fit within the lot constraints
- Accept a condition that the lot can only be used for purposes that don’t require a wastewater system (e.g., no dwelling)
Option 2 is the most common outcome in practice, it is better to lose one proposed lot during planning than to create a lot that a future buyer discovers cannot be built on.
Costs of Septic Planning for a Rural Subdivision
| Cost Component | Indicative Cost (2026 AUD) |
|---|---|
| OSMM report (per lot assessed) | $800 to $2,000 per lot |
| Percolation tests (per lot) | $400 to $800 per lot |
| OSMM report for 5-lot subdivision | $5,000 to $15,000 |
| Hydraulic engineer’s report (complex sites) | $5,000 to $15,000 |
| Council DA fees (includes OSM component) | $1,500 to $5,000+ |
These costs are in addition to the general subdivision DA costs (survey, road design, infrastructure plans, etc.).
FAQ
Do all new lots in a rural subdivision need their own septic system? Yes, if they are not connected to reticulated sewer. Each lot must be independently serviceable, you cannot have one lot’s wastewater system on another lot’s land (easements for this are possible but unusual and add complexity).
Can we use a shared septic system for multiple lots? Shared systems are possible in principle but create significant ongoing management complications (who is responsible? who pays for maintenance? what happens when one lot’s use exceeds the system’s capacity?). They are rarely approved by Port Macquarie Hastings Council for new rural subdivisions and are not recommended.
The OSMM report shows one lot is marginal, should we proceed? A marginal result needs careful interpretation. If the system that fits is an expensive AWTS on a lot buyers expect to pay conventional-system prices for, this needs to be disclosed clearly. If the lot genuinely cannot support a viable system, don’t create it, a lot that can’t be built on is a liability, not an asset.
Can we do the OSMM report after DA lodgement? No, the OSMM report is a required part of the DA submission. A DA without it will be returned as incomplete.
How long does the rural subdivision approval process take? In the Port Macquarie Hastings LGA, rural subdivision DAs typically take 6-18 months from lodgement to determination, depending on complexity. Add the time for OSMM report preparation (2-6 weeks) and pre-DA consultation (2-4 weeks) to the front end.
Planning a rural subdivision in the Port Macquarie or Hastings region? Send an enquiry about onsite sewage management requirements; the guides here set out what Council expects, and a qualified wastewater consultant prepares the OSMM report.