Fire access tracks and asset protection zones (APZs) are practical fire safety infrastructure, and in the Blue Mountains they are increasingly relevant as development edges meet the bush. Creating a fire access track or clearing an APZ on a steep slope almost inevitably involves earthworks, cutting into the slope to create a level or manageable gradient, and earthworks on a slope require retaining walls to keep the cut face stable.
Understanding the intersection of bushfire planning requirements, retaining wall engineering, and BMCC consent is essential for any Blue Mountains property owner undertaking fire access or APZ works.
Quick answer (BLUF)
Fire access track retaining walls must be non-combustible in all but low-BAL areas, must handle the structural loads of fire appliance vehicles, and must be maintained clear of vegetation on and around them. The NSW RFS specifies minimum track widths, grades and turning radius standards. BMCC consent is required for access tracks and APZ clearing that meets development thresholds, with RFS concurrence forming part of the approval process.
What is a fire access track?
A fire access track is a cleared pathway providing vehicle access to a property (or through a property) for fire-fighting appliances. The NSW RFS specifies minimum standards:
- Width: 3.5-4.0m cleared width for single-lane access; 6.0m for two-way access
- Grade: Maximum 1:4 (25%) for formed tracks; steeper grades require all-weather sealed surfaces or additional engineering
- Turning circle: Minimum 12m internal turning circle or a T-intersection for turnaround
- Overhead clearance: Minimum 4.0m
On a Blue Mountains slope, meeting these standards while managing the significant grade changes typical of Mountain properties requires cut-and-fill earthworks and retaining walls at every significant grade change.
Structural requirements: fire appliance loads
Fire trucks are heavy vehicles, Class 3 fire appliances commonly weigh 15-22 tonnes. Retaining walls adjacent to fire access tracks must be designed for the wheel loads of these vehicles, which are significantly higher than standard residential traffic loading. A retaining wall on the downslope side of a fire access track with a fire truck potentially stopping or turning alongside it may need to be engineered for a surcharge load of 10-15 kPa or more, substantially more than a standard residential driveway surcharge.
This load requirement often pushes fire track retaining walls to besser block (core-filled concrete masonry), reinforced concrete or significant mass concrete construction. Timber sleepers and lightweight dry-stone walls are generally inappropriate for vehicle-loaded fire track applications.
Non-combustible material requirements in BAL zones
In bushfire prone areas, which covers most bush-edge properties throughout the Blue Mountains, retaining walls adjacent to fire access tracks should be of non-combustible materials:
- Concrete sleepers: Acceptable
- Besser block / concrete masonry: Strongly preferred, excellent thermal mass, non-combustible, structural
- Sandstone: Non-combustible, acceptable; ensure no combustible mortar or backing material
- Timber sleepers: Not recommended within or adjacent to the APZ, particularly in BAL-29, 40 and FZ areas
The NSW RFS and BMCC both prefer non-combustible materials for structures within the APZ. Materials that contribute to fire intensity or ignition risk during a fire event reduce the effectiveness of the APZ as a protective buffer.
Asset protection zones: what retaining walls are involved
An APZ (formerly termed a “hazard management area”) is a zone of managed vegetation around a building where fuel is reduced to limit the intensity of a fire approaching the structure. On a steeply sloped Blue Mountains lot, creating the APZ to the required width on a downslope side can involve:
- Clearing vegetation on the slope (subject to BMCC vegetation removal consent)
- Grading or terracing the slope to create a manageable slope angle within the APZ
- Retaining walls at the lower boundary of terraced sections
- Ongoing maintenance to keep the APZ clear of regrowth
Retaining walls in the APZ must themselves be non-combustible and should not create zones where leaf litter or debris accumulates that could become fuel. Open-jointed masonry (besser block, sandstone) is preferable to closed concrete surfaces that hide debris accumulation behind them.
BMCC consent and the RFS referral process
Any earthworks for fire access track construction that exceed the Codes SEPP exempt thresholds require a development application. Given that fire track construction typically involves significant grading, vegetation clearing and retaining walls, a DA is almost always required.
The DA process for bushfire prone land automatically triggers a referral to the NSW Rural Fire Service. The RFS assesses whether the proposed works comply with Planning for Bushfire Protection (PBP 2019) requirements and issues a bushfire safety authority or concurrence with conditions.
BMCC’s DCP also has specific provisions for access and egress, vegetation management and earthworks in bushfire prone areas. The conditions of DA consent may include requirements for:
- Minimum all-weather pavement standard on the access track
- Barrier rails on exposed track edges
- Passing bays at intervals on single-lane tracks
- Maintenance obligations to keep the track and APZ clear
FAQs
Do I need an engineer for a fire access track retaining wall?
Yes, if the wall exceeds 600mm and is subject to a DA (which fire track construction almost always is). The engineer must specify the wall for the fire appliance vehicle load, which requires specific structural design input.
Can I create a fire access track and APZ without council consent?
Only if the earthworks fall within exempt development thresholds, extremely unlikely for a fire access track of meaningful length on a slope. The vegetation clearing component alone is likely to require BMCC consent. Contact BMCC’s development assessment team before commencing any works.
What width does the retaining wall need to be from the edge of the access track?
The RFS specifies the minimum track width and the required clearance to obstacles. Retaining walls on the downslope side of the track should typically be set back at least 600mm to 1.0m from the track edge to allow for vehicle overhang and to prevent damage to vehicles using the track. Confirm the specific setback with the RFS through the DA referral process.
Is vegetation clearing for an APZ subject to biodiversity assessment in the Blue Mountains?
Potentially yes. Clearing of native vegetation in the Blue Mountains, even within an APZ, may trigger the Biodiversity Conservation Act 2016 if the clearing exceeds the relevant area threshold or affects threatened species habitat. The DA for fire track and APZ works should include a biodiversity assessment to confirm whether this applies.