Development approval process
A step-by-step guide for development applications within Mine Subsidence Districts.
If you plan to build or subdivide within a district, you must obtain approval from Subsidence Advisory NSW before starting work.
Subsidence Advisory may place conditions on any development within a district to reduce the risk of potential mine subsidence damage.
Conditions may include requirements related to the following:
- nature and class of any development
- the size, height and location of new structures
- the size, location and amount of proposed lots
- use of certain building materials and construction methods
- cost of development.
In most cases, Subsidence Advisory's requirements for standard residential development do not result in increased construction costs and are consistent with the Australian Building Code.
Development applications can be lodged directly with Subsidence Advisory or as an Integrated Development through your local council.
Surface Development guidelines
Guidelines set out the requirements for building on a property based on potential mine subsidence risks.
Different guidelines may apply to neighbouring properties within a district. This is because each property can have differing subsidence risks for example, one property is mined beneath while the neighbouring is not.
Find out the development guideline for your property on the NSW Planning Portal and download a full copy of the guideline.
Subsidence Advisory offers deemed approval for some minor construction works, such as small carports, decks and fences. Read the list of deemed approval items (PDF 105.61KB) that do not require Subsidence Advisory approval.
Search for the property on the NSW Planning Portal to:
- find out if the property is in a Mine Subsidence District
- find out which Subsidence Advisory NSW surface development guideline is assigned the property.
Prepare plans of the proposed development that comply with the applicable surface development guideline for the property. Contact Subsidence Advisory for preliminary advice if the proposal is not likely to comply with the guidelines.
Subsidence Advisory requires a full set of architectural (site, floor, and elevation) plans to assess a development.
If you are applying for a subdivision, you will need to submit a subdivision plan that includes the proposed lot layout, numbering and dimensions. For large or staged subdivisions, a stage breakdown and digital (.dwg/.shp) file should be provided.
Check the list of deemed approval items (PDF 105.61KB) that do not require Subsidence Advisory approval.
Councils and Accredited Certifiers are authorised to approve development applications that comply with the following 5 guidelines without a requirement for referral to Subsidence Advisory.
• Guideline 2
• Guideline 3
• Guideline 5
• Guideline 6
• Guideline 8
Councils and Certifiers will still be required to refer any development applications that do not comply with a property’s guideline or applications for development on properties assigned Guidelines 1, 4 or 7 to Subsidence Advisory for approval.
All other development
All other proposed development within a district requires an application to be lodged directly with Subsidence Advisory through the Subsidence Advisory Portal or as an Integrated Development through council. Council will refer the application to Subsidence Advisory for assessment where required.
Note: If you are planning to subdivide a property, a separate subdivision application is required.
Subsidence Advisory will assess the application to determine if it complies with the Surface Development Guideline allocated to the property.
Guideline compliant applications are approved by Subsidence Advisory within 7 calendar days of receipt. Applications that do not comply, are referred to a merit assessment.
Development applications that exceed the assigned development guideline for the property are assessed on merit under the following policies.
Developments are assessed in accordance with Subsidence Advisory's Merit Assessment Policy.
Subdivisions are assessed in accordance with Subsidence Advisory's Subdivision Policy.
As part of the assessment process for these applications Subsidence Advisory will consider the:
- likelihood that mine subsidence events will occur
- consequence of mine subsidence events on surface infrastructure and public safety
- reliability of information used to determine the above, including mine plans, assumed pillar and extraction dimensions, and assumptions regarding geotechnical modelling
- risks arising from the proposed engineering controls.
All merit based determinations under section 22 of the Act will be determined within 40 calendar days of receipt unless additional information is requested by Subsidence Advisory to progress the application, or if the application is an integrated referral and alternate timeframes apply.
Subsidence Advisory may approve a development or subdivision application with conditions to protect the proposed or future structures from potential mine subsidence damage.
In some situations, you may be required to provide more information to support your application. For example, the results of desktop geotechnical studies and borehole investigations.
Subsidence Advisory can refuse or approve development applications with or without conditions. Subsidence Advisory will provide an approval and any conditions to applicants via the online portal. Approvals for exempt developments can be provided by council or a principal certifying authority.
Designing for mine subsidence
This general advice on designing for different mine subsidence parameters is aimed at developers and technical experts. It is not comprehensive but gives guidance on the issues involved in development on subsidence affected land.
Vertical subsidence by itself is seldom a significant factor in the design of individual buildings.
Structures will be left at a lower level, but this normally has no adverse effect on them except in the case of buildings that are in close proximity to watercourses and waterbodies. Mine subsidence may expose such houses to an increased flooding risk. In these cases, habitable floor levels should be designed to be comfortably above relevant flood level design requirements additional to vertical subsidence requirements.
Subsidence design requirements for strain refer to normal strain, which is the differential horizontal movement of the ground. The design must account for both tensile strains (expressed as positive) and compressive strains (expressed as negative). Strains can be oriented in multiple directions.
Ground strains can be transferred into structures where the foundations do not form a flat plane and are keyed into the ground surface. Foundations that are keyed into the ground include integral retaining walls, drop edged slabs and slabs with thickened edge beams. The greater the depth of the foundation, the greater the likelihood that strain will be transferred into the building structure.
The transfer of strain can be reduced by:
- Making the foundations as shallow as possible or over a slip layer, such as sand bedding and plastic membranes which separate the footing structure from the founding material where improvements are constructed on a level plane, such as a slab on ground.
- Including some form of separation between the foundations (for example piers and ground beams) and the building superstructure where deeper foundations are required, such as piers.
- The excavation of trenches around the structure that extend just below the underside of the foundations which are backfilled with sufficiently compressible material.
Curvature is the rate of change of tilt and is typically expressed as a radius of curvature in units of km or km-1. Curvature can be oriented in multiple directions and unless otherwise specified, the design should be able to accommodate both upward (hogging) and downward (sagging) ground curvatures. Ground curvature results in differential settlement across the building structure.
The effects of ground curvature can be reduced by panelling and articulating walls to move without developing strains or cracks or causing doors and windows to jam.
Vertical articulation joints spaced at appropriate intervals and in areas where the wall stiffness changes such as above windows and doors reduces the likelihood of damage. An additional articulation measure is to eliminate brickwork above windows, doorways and arches. If such details are included, special attention must be paid to the provision of bond seams and strengthening panels that incorporate arches.
A tilt caused by active underground mining refers to a change in the slope of the land surface between two points. Tilt is defined as a change in slope, or difference in vertical subsidence at 2 points, divided by the horizontal distance between them and is typically expressed in units of mm/m.
Whilst ground tilts will introduce additional bending moments in structures, the additional loads due to tilt rarely result in significant impacts on the structure. Tilt impacts are more often noticed to adversely affect the serviceability of structures.
Small tilts generally do not affect the usage of a building and can be catered for by providing such things as generous falls for services. Construction tolerances are typically in the order of 3 to 4 mm/m and drainage structures are usually built with grades that are greater than 10 mm/m.
Sinkholes or potholes occur in areas that have been undermined by shallow historical mine workings. Potholes are holes in the ground surface resulting from subsidence and usually occur in areas where old inactive mine workings are very shallow. The majority of potholes that occur in previously developed areas are less than 5m in diameter.
Properties that have been assessed as being subject to a sinkhole risk have been assigned a Surface Development Guideline 1. Some properties that have been assigned a Guideline 7 may also be subject to a sinkhole risk.
Guideline 1 allows for a single storey brick veneer or 2 storey lightweight residential building. The guideline describes a standard sinkhole foundation design.
Alternatively, Guideline 1 also allows for a design made to engineering principles by a qualified structural engineer that can accommodate a pothole of maximum diameter of 5m forming at any point beneath the structure.
Specific design and performance requirements and restrictions are outlined in the guideline, and it should be read in detail to ensure compliance prior to carrying out the design.
Structures that do not conform with Guideline 1 or have been assigned a Guideline 7 are assessed under Subsidence Advisory NSW’s Merit Assessment Policy.
For applications that exceed the guideline, it is recommended that the engineer consult with Subsidence Advisory prior to undertaking detailed design. Specific design or sinkhole mitigation requirements may vary, dependent upon the building type and the assessed level of geotechnical risk.
Large and complex development
If you are planning a large or significant development, contact Subsidence Advisory for advice in the preliminary planning stages of the project.
If preliminary or concept plans exist, you should submit these with a building and/or subdivision enquiry via the Subsidence Advisory Portal so that formal advice can be issued.
Buildings and other structures can be designed to better respond to ground movement caused by mine subsidence. Our specialist engineers can provide information and advice on mine subsidence design requirements.
Some large and complex developments over old inactive underground mine workings have significant risks. Applicants may be required to eliminate the risk of subsidence by grouting the abandoned mine workings.
Section 4.46 of the Environmental Planning and Assessment Act 1979, specifies that all development within a district (excluding exempt development) is considered ‘integrated development’.
Under Section 4.47(2) of the Environmental Planning and Assessment Act 1979, councils are required to refer all integrated development to Subsidence Advisory for approval.
Newcastle Mines Grouting Fund Maps
These maps have solely been prepared to assist landowners in identifying potential funding from the Newcastle Mines Grouting Fund.
The Newcastle Mines Grouting Fund is a NSW Government Fund that operates in the Newcastle City Centre Area. The fund is administered by the Hunter & Central Coast Development Corporation (HCCDC) within the Department of Planning, Industry and Environment.
The zones detailed in the maps directly correspond to funding category rates and have been prepared based on locations of underground coal mine workings.
Learn more about the Newcastle Mines Grouting Fund, including funding category rates.
It is important to note that the maps do not identify potential subsidence risks, development guidelines or Subsidence Advisory’s approval processes or conditions.
If you are planning to build or subdivide within a mine subsidence district, you must lodge a development application and obtain approval from Subsidence Advisory prior to commencing work.
For questions regarding the Newcastle Mines Grouting Fund, contact HCCDC.
The source data used to compile the maps has been obtained by Subsidence Advisory from records held by:
- Department of Regional NSW – NSW Resources Regulator
- NSW Department of Customer Service – Spatial Services
- Newcastle City Council
- mine operators.
Accordingly, no warranty is expressed or can be implied as to the accuracy of the maps or that the maps are free from any error or omission. The state of NSW, Subsidence Advisory and their servants and agents expressly disclaim any liability whatsoever for the consequences arising from any act done or omission made in reliance on the maps.
The maps and zones are subject to copyright and made available for use subject to the above disclaimer and in accordance with the following conditions:
- The maps and/or zones are not to be used for any purpose other than to obtain an understanding of the funding from the Newcastle Mines Grouting Fund in the Newcastle City Central Area (NCCA).
- The maps are not to be used or relied on for detailed planning or structural design.
- The maps may not be reproduced or otherwise used for commercial gain. In any event, the maps and zones may only be reproduced in full and must include a copy of the above disclaimer and these conditions. It is the responsibility of the user of these maps and zones to ensure that any printed copy is identical to the most recent version of the plans and zones published by Subsidence Advisory.
- Subsidence Advisory reserves the right to refuse the approval of any subdivision or surface development of land in a mine subsidence district. The map and/or zones should not be used or relied upon for development planning, or grout requirements.
- Subsidence Advisory reserves the right to amend the maps and/or zones at any time and for any reason without notice to any user of those maps and/or zones.
For further information, please contact Subsidence Advisory by:
Please refer to the disclaimer prior to accessing the maps and legend.