Introduction
In Queensland the Department of Employment Economic Development and Innovation (DEEDI) through its Tenure Branch administers mining tenures including the issuing of production leases and exploration tenures and the registration of the various plans and documents associated with these tenures. DEEDI also has a Mines Inspectorate which is responsible for mine safety and is also responsible for the collection and preservation of the various statutory mining and petroleum plans produced each year by the Mining and Petroleum companies granted tenures by DEEDI’s Tenure Branch.
The Department of Environment and Resource Management (DERM) is responsible for the issuing of land titles across Queensland and the registration of the various associated plans. This paper suggests there is a need to improve linkages between the various registering authorities to ensure that information collected is easily obtainable by all perspective users of the information.
Mines both surface and underground, mine shafts including capped mine shafts and petroleum wells all have significant impacts on the land and will continue to affect the land long after mining operations have ceased. It is extremely important that all mining activities that continue to affect the land after mining has ceased are drawn to the attention of all future land users.
This paper will discuss some of the problems that have arisen or may arise when subsequent land users have not been made aware of the impacts of past mining activities on the future development of the land. This paper will also suggest some relatively simple ways in which the current systems may be improved.
Underground Mines - Collingwood Park
Underground Mines can continue to affect land long after mining operations have ceased. A clear illustration of this fact is Collingwood Park.
Collingwood Park is a residential housing area located in Ipswich South East Queensland over a number of old coal mines. The New Redbank Colliery mined the Bluff-Four Feet seam (the seam thickness was 15.2m) from the 1920’s through into the 1930’s.
In 1959 the then Department of Development and Mines advised the Queensland Housing Commission that there was no danger of subsidence in the area now known as Collingwood Park. The Queensland Housing Commission purchased the land and began to develop it. The Redbank Plaza Shopping Centre is now located on the site of the old Redbank Colliery.
Coal exploration and drilling programs commenced in 1965 and continued until 1969 over areas of Collingwood Park that were at that time predominately bushland. A significant economic seam was discovered and Westfallen No. 3 Colliery was subsequently developed and mined using continuous miners utilizing a multi-slice bord and pillar method.
Mining in this area continued through to 1987 and as the mine retreated pillars may have been split; tops taken and floors stripped leaving roadways possibly up to 11 meters high and roadways up to 7 meters wide. The Mine varied in depth between 115 and 155 meters and extended under existing roads and built up areas.
In 1988 a significant subsidence event occurred in the vicinity of Lawrie Drive over a section of the Westfallen No. 3 Colliery. In April 2008 another significant subsidence event occurred this time in the vicinity of Duncan Street. As of August 2008 the total surface subsidence in the Laurie Drive Area was 2.2 m and in the Duncan Street area was 1.3 meters.
There have been a number of studies that have been commissioned which have considered pillar stability of the underground coal mines below Collingwood Park. All studies have in essence concluded that future pillar failure is likely and similar subsidence events will continue to occur unless practical mitigation works can be identified and undertaken.
The subsidence at Collingwood Park has forced many families to leave their homes and caused concern to many other residents. The State Government has spent tens of millions of dollars buying or repairing houses, commissioning reports and investigations and assisting the community and affected property owners. The costs are ongoing as steps are continuing to be taken to identify potential solutions to stabilise the underground mine workings.
In hindsight it is clear that mistakes were made in allowing coal mining operations to extend under an existing residential area. It is imperative that the problems that have occurred at Collingwood Park are not repeated elsewhere in Queensland.
There are hundreds of underground Mines (both operating and abandoned) in Queensland many of which are coal. All these mines present potential subsidence hazards for any subsequent land developments.
Subsidence above coal mines is not a new issue, in fact it has been known about since well before the Welsh Miners first lead ponies into the pits. As outlined under the Coal Mining Safety and Health Act 1999 (CMS&H) and associated regulations extensive mine plans (statutory plans) must be lodged with the DEEDI Inspectorate each year and also at the completion of the mines life.
Unfortunately, the vast majority of these detailed plans which are prepared under the supervision of highly qualified and skilled surveyors are not incorporated into either DEEDI’s graphical database IRTM (Interactive Tenure Maps) or DERM’s graphical database the DCDB (Digital Cadastral Database).
The enormous costs involved to correct the Collingwood Park experience make it clear that the information on statutory mine plans should be urgently incorporated into a publicly searchable graphical database.
The next subsidence event at Collingwood Park may not occur for many years by which time the current subsidence reports and media releases will be a tiny dot of data filed away in a forgotten archive. The issue is much wider than Collingwood Park and steps need to be taken to ensure all future land owners, planners and developers are advised that the land they may wish to purchase is located over an underground mine.
Capped Mine Shafts
Queensland has a number of old mining areas where open mine shafts are a permanent reminder of mining activities of a past era. These old mine shafts are an eye sore and potential hazard. In 1997 the then Department of Mines (now DEEDI) began a shaft capping program to safely cap shafts in residential areas. Predominately, the abandoned shafts capped since 1997 have been in either Gympie or Charters Towers.
The capping process involves removing all loose soil from around the shaft until a solid base is uncovered. Often a large amount of material is removed to reach solid bedrock which involves the construction of ramps to get the necessary equipment (i.e. trucks, excavators, cranes etc.) to the open shaft. Once a solid pad has been established reinforced concrete (generally five meters square and 300mm thick) is then laid over the shaft and the site back filled. To reduce the build-up of gases within the shaft cavity a breather (vent) pipe is also installed, however the breather may not be in the centre of the shaft or even necessarily over the shaft. The whole site is then back filled.
The capping program has been an excellent program which has been let down somewhat by DEEDI’s somewhat disjointed approach to locating the shafts once they have been capped. A number of different approaches were taken to locate capped shafts including
- Officers in DEEDI surveying the cap and preparing fieldnotes.
- DEEDI engaged Consulting Surveyors to survey the caps and prepare a plan.
- Handing the responsibility over to the local authority. In some instances we understand the local authority may have connected the capped shaft to points of interest in the area (i.e. the kerb). Many of the shafts may not have been connected to either the existing cadastral boundaries or existing permanent survey marks.
- Officers in DEEDI Abandoned Mines Unit (AMU) located the capped shafts with GPS and incorporated the results into databases held in the relevant district offices.
- In some instances capped shafts were not located and their location is now unknown.
Where plans have been prepared of shaft investigations or locations the DEEDI Survey and Mapping Section has commenced having the plans captured by DERM and linked through CISP. The Surveying and Mapping section has also commenced the task of preparing plans from the fieldnotes produced by the Department Officers.
As the majority of shafts are now capped and buried below what may be 5 meters of fill it is not possible to locate a shaft without an accurate survey record. Breather pipes are a guide, however with the passage of time these may also disappear.
The caps are strong however they do remain a potential hazard that all land holders need to be aware of. In the future caps may fail or shafts may subside as the voids below the shafts collapse. Land owners installing swimming pools, bores or developers building underground parking areas may find these buried treasures.
All future owners and users of land need to know that a shaft has been capped on the land and the exact location of the shaft. We are aware that subdivisions have proceeded on some capped shaft sites and no easements, covenants or other boundary adjustments have been made to in any way accommodate the capped shaft. There is also no notification on the title of the potential hazard that lurks beneath the surface. Has the State allowed a series of future Collingwood Park type situations to arise in Gympie and Charters Towers?
Coal Seam Gas
Queensland is currently in the midst of a booming coal seam gas industry which involves drilling tens of thousands of wells across Queensland’s coal fields. The industry has the potential to be massive with tens of billions of dollars being proposed to be spent on projects currently approved in Queensland.
Methane gas is released from the coal seam by drilling wells into the coal seam and then dewatering the coal seam to allow the gas to escape. In many instances hydraulic fracturing or “fracking” is required to open cracks in the coal seam and so allow the gas to escape. Fracking involves injecting a high pressure mixture of sand, water and chemicals into the coal seam to open cracks in the coal.
As you may be aware there are a number of environmental concerns related to coal seam gas extraction including pollution and disruption of water aquifers, spills and leakage of hazardous substances. There is significant community concern about the effects the development of the Coal Seam Gas industry may have on the farmlands and local communities in the coal gas areas.
Our interests do not relate directly to possible environmental problems but rather to ensuring all wells are located accurately both above and below the ground. Once the wells are accurately located we are then concerned to ensure well information is then presented in a manner which alerts people with interests in the land or the underlying coal seam that a well is present.
We imagine that the community concerns regarding Coal Seam Gas will not quickly disappear and extensive monitoring programs around wells and the surrounding environment shall be required. It would also appear research will be required on some of the community concerns raised. Accurate locations of all sections of the wells and clear presentation of the information will be critical to future research and monitoring in this area.
Currently each wellhead is accurately located horizontally and vertically. The wells are also connected to the nearest property boundaries. Plans are then prepared of each well head and lodged in the Survey and Mapping section of DEEDI.
Over the past year the survey and mapping section of DEEDI has commenced a program of having these plans imaged by DERM and linked through CISP. The well heads are also plotted on DEEDI’s IRTM.
As outlined under the Petroleum and Gas (Production and Safety) Regulations 2004 petroleum companies must prepare reports which include details of the down the hole surveys. These reports should be lodged with DEEDI. Unfortunately DEEDI does not map the below ground section of the wells and the information is currently only available in the written well reports. Without accurate maps it is very difficult to understand the full extent of the wells and the areas of related influence. It will be very difficult for subsequent land users, planners, owners or future underground coal miners to fully grasp the impacts and implications of coal seam gas wells on land unless they
- Complete searches in the appropriate section of DEEDI
- Analysis and map the information which is available in the various lodged reports.
As we understand there are potentially 40,000 coal seam gas wells to be drilled in Queensland in the next five years there will be major implications for all land users in the regions affected. Improvements in the way DEEDI catalogues archives and presents graphical information may greatly assist many of the current and future users of the land.
Open Cut Mines – Environmental Concerns
In Australia many mines both metalliferous and coal expose rocks containing sulphide minerals to the atmosphere. Once exposed to oxygen and water the sulphides react and form acidic water or what is commonly referred to as acid mine drainage (an alternative name is acid rock drainage). It is a major environmental problem not just in Australia but worldwide.
Processes can be developed to reduce the acidity of water draining from mine sites, unfortunately the better the process the higher the price. In old abandoned mine sites one common practice is to cap waste rock (i.e. slow oxidation) and use lime trenches. It is important in any future use or development of old mine sites that acid mine drainage and associated remedial works are considered and preserved or improved.
Apart from acid mine drainage old mine sites may have significant other environmental dangers that need to be recognised and evaluated prior to any future development of the site.
While operating statutory plans are prepared each year of all mine workings, plant areas and remediated areas by the mine operator. These plans should be lodged with the Inspectorate in DEEDI each year and also at the completion of the mines operations. As with the underground mines plans most of these plans show information which is critical for future land users. Unfortunately these plans are not incorporated into DEEDI’s graphical database (IRTM).
Recommendations
Mines, boreholes and shafts do not disappear they remain as an integral part of the land and significantly affect all future land owners and users. It is important that State Government systems and processes draw future land owners and users attention to
1) The fact that a significant mining event has occurred on or below the land
2) The scale and type of activity that has occurred on the land
3) A simple means to retrieve all the plans and reports that describe the mine activities that have been performed on the land.
DERM maintains the States titling system which grants and administers land titles. Land titles are uniquely powerful documents that do not disappear with companies or generations. An administrative advice could be added to titles which would alert owners and potential owners to any previous mine workings on the land (i.e. underground workings, open cut workings, shafts capped or open and petroleum/gas wells). The advice would not halt sales or developments however it would alert purchasers to a potential risk.
An administrative advice on the title stating the fact and directing any potential owners to DEEDI where the statutory mine plans, reports, shaft details or well details can be searched may save the potential land owner much heartache and the State millions of dollars.
In DEEDI the importance of the statutory plans which should be lodged by the mining companies with the inspectorate each year seems to have been overlooked. A reference to the vast majority of the plans is not included in DEEDI’s graphical database and the plans are not available in a digital form.
It’s perplexing that in Queensland we have DERM that can operate a digital plan archival and retrieval system over the entire state catering for hundreds of thousands of plans and yet DEEDI who are responsible for plans of equal importance and significance to land basically have no well-defined archival, filing or retrieval plan system. To overcome this short coming the surveying and mapping section of DEEDI have had tenure plans, capped shaft survey plans and petroleum well head location plans imaged and archived into the DERM system. We suggest that consideration be given to having all statutory mines plans likewise incorporated into the DERM systems.
Most, if not all, of the larger mining and petroleum companies in Queensland operate Geographical Information Systems (GIS) which can accurately show three dimensional data (i.e. underground mines and borehole locations). We suggest that DEEDI should not only continue to develop its GIS capabilities but also allow for digital lodgement of statutory plans and borehole data that can be incorporated directly into a State system.
Planning, developing and efficiently using land are critical to the future prosperity of Queensland. Mining and petroleum activities on the land have significant impacts on the land that extend well past the completion of mining or gas extraction. It is important that all mine and gas production areas (past or present) are identified and accurately mapped and incorporated into the land systems and processes which provide ready access to important information.
Rex Hutchison
August 2011
About the Author
Rex Hutchison has been a consultant to the Mining and Development industries for over twenty-five years and has had experience in Open Cut and Underground mines (both metalliferous and coal). Recently he worked part time for DEEDI (Mines) and is now back consulting. He spends his spare time climbing mountains and sailing an old wooden boat.
References
Parsons Brinckerhoff Australia Pty Limited, Scoping study for Collingwood Park subsidence 2009
Available at: http://mines.industry.qld.gov.au/safety-and-health/collingwood-park-subsidence.htm
Rex Hutchison, Lessons from Gretley – Mapping for Today and Tomorrow Spatial Science Queensland April 2011
Available at: http://www.sssi.org.au/details/region/4/cat/276/sub/278.html
Details relating to DEEDI’s Coal Seam Gas program
available at: http://www.derm.qld.gov.au/environmental_management/coal-seam-gas/about.html
Details relating to DEEDI’s shaft capping program
available at: http://mines.industry.qld.gov.au/safety-and-health/abandoned-mine-lands-program.htm
Details relating to Statutory Mines plans refer to
“Recognised Standard 10 Mine Surveying and Drafting - Coal Mining Safety and Health Act 1999. ” available at:
http://mines.industry.qld.gov.au/assets/safety-and-health/rec_stand_10_mine_surveying.pdf
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Related Web Sites
Coal seam gas - how is it mined? http://www.abc.net.au/news/specials/coal-seam-gas-by-the-numbers/drilling/
Subsidence Maps of Collingwood Park - http://mines.industry.qld.gov.au/safety-and-health/collingwood-park-subsidence.htm
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Shaft pics
 Excavation for shaft capping |
 Shaft preparation |
 Residential capped shaft |
 Completed shaft |