Frequently Asked Questions (FAQs)
The Project is Tahmoor Coking Coal Mine’s proposal to continue mining operations until approximately 2035. It will be situated within a lease which has been held by the mine for 30 years; to the south of the current mining area.
Government approval of the of the Tahmoor South Project will ensure continued employment for another 13 years of close to 400 people; close to half of whom live locally. A total of $784 million will be injected into the region and state economies.
In the Wollondilly region this will include benefits of $122 million to employees; $35 million to local businesses; and $5.2 million to Wollondilly Shire Council in payment of rates. It will also ensure continued support of more than $100,000 a year for local community groups, programs and initiatives.
A Project Amendment Report has been prepared that outlines a number of changes made to the project in response to concerns, including a decrease in longwall dimensions and a revision of the design of the reject emplacement area to reduce impacts to the nearby Shale Sandstone Transition Forest.
‘Longwall mining’ is a widely used method of mining coal from underground. Firstly, underground roadways are cut through solid coal to separate each section of coal to be mined.
These sections are called ‘longwalls’. Each longwall is separated by sections of unmined coal, which provides roof support to the roadways.
The machinery used to mine the coal from the end of each longwall is called a ‘longwall shearer’. The area immediately in front of the shearer is called the coal face. Hydraulic roof supports or ‘chocks’ are used to provide space in front of the coal face for the longwall shearer and the conveyors that transfer the coal to the surface.
Longwall shearers move from side to side across the longwall, cutting slices of coal. After each slice of coal is removed, the longwall shearer is moved forward. As the longwall shearer moves forward, the mined section behind the longwall roof supports is allowed to collapse into the void. This void is referred to as the ‘goaf’. As the roof collapses into the goaf behind the longwall roof supports, the overlaying strata collapses and results in subsidence of the surface area above.
If the Project is approved, the Company must then prepare and submit an Extraction Plan to the NSW Department of Planning Industry and Environment before mining can commence, which is expected to be in 2022. Mining will then progress from the first longwall through to the final longwall over an approximate period of 13 years. (An Extraction Plan outlines in detail the process for management of all aspects of mining including subsidence and its effects on the surface).
Mine subsidence refers to any surface ground movements associated with underground mining. Typically, mine subsidence refers to a vertical movement at a particular point. This occurs when material is removed from an underground mine and the earth above the mine adjusts to the altered landscape.
The amount of subsidence varies across the area mined beneath, with greatest subsidence occurring towards the centre of the mined area, and gradually reducing to outside the mined area.
If subsidence occurs uniformly across an area, it is unlikely that any impacts would be noticed. However, differential subsidence results in tilting and bending of the ground. These differential movements can result in mine subsidence-related impacts to surface features.
Mine subsidence commonly also results in horizontal movements. Differential horizontal movements cause ground strain. Small horizontal movements may be experienced at points on the surface that are some distance away from the mining activity.
The level of effects on the surface will vary, according to a range of elements, including little to no effects at all. The Subsidence Impact Assessment prepared by independent specialists for the project, concluded that potential subsidence effects were consistent with those observed in the current mining area, and that the majority of the houses located within the mining area would be unaffected or would require only minor adjustments due to subsidence.
More specific details will be available in the approved Extraction Plan, which is required by government closer to when mining occurs.
Before mining can start, we will discuss the details with those who live in and/or own property above the future mining area. As we have done in the past with more than 1900 home-owners, we will distribute information packs to residents in advance of mining including relevant information relating to potential subsidence, and how it will be managed.
We also regularly distribute community newsletters like this one, with updated information about our mining activity and host regular community information sessions throughout the year.
If you are not sure about the process for managing properties potentially impacted by future mine subsidence you can find out more by contacting the Tahmoor Coal Community Contact Line – 1800 154 415 or via Subsidence Advisory NSW – www.subsidenceadvisory.nsw.gov.au
There is no mining proposed to take place beneath either the Nepean or Bargo Rivers, or major creeks and streams.