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Protect Sydney's Water
Transcript of Protect Sydney's Water
The Special Areas
Dharawal National Park
These areas south of Sydney supply about 20% of Sydney's water. However, this supply is crucial; unlike Warragamba to the west, this is an area of high and reliable rainfall.
Sydney's water supply is sourced from a vast area extending all the way to Goulburn.
What is longwall mining?
Longwall mining is the current most economic method of underground coal mining.
It's used when the coal seam is too deep to do open cut mining (as in the Hunter Valley).
Although the impacts are not as obvious as open cut mining, they are still significant, especially to river systems.
The longwall works by having
a massive shearer carve across
the face of a coal seam 2 to 3
metres high, up to 400m wide
and several kilometres long.
As the longwall advances through the coal seam, the roof above the void created by extracting the coal (the goaf) collapses behind the machine.
The collapse of the mined out section causes impacts all the way to the surface. This is manifested in the ground dropping, typically up to 2m. This is called subsidence.
Any natural features in the subsidence zone (or "bowl"), especially sandstone-based rivers, will be cracked.
Streambed cracking and loss of surface flows
Contamination of water
These 4 photos illustrate a worst case scenario which was Waratah Rivulet as it appeared in November 2006. Waratah Rivulet flows into the Woronora Dam.
This is the expansion for Metropolitan Colliery which was approved in 2009, after all the previous damage that was exposed in 2006.A tokenistic “no go zone” has been created (purple area) but then longwalls are projected to undermine the storage of Lake Woronora itself.
No lessons have been learnt. This is the most recent damage (Feb 2014). A 1.5km long pool (Pool N) has been completely drained.
The state of the water in Waratah Rivulet in 2011, 5 years after the original damage upstream. Water has re-emerged downstream of the earlier damaged section, bringing with it contaminants such as iron, manganese and zinc. These chemicals are leached from the freshly-cracked faces of the broken up rock strata through which the water travels underground. There is no proof that all the diverted water re-emerges, although the mining companies like to say that’s what happens.
Where some water remains, it is highly contaminated, especially by iron, which oxidises, causing the bright orange colour. Iron-feeding bacteria then cause rafts of floating orange scum which clings to everything.
Here the streambed has cracked and compressive forces have caused upsidence where the creek bed bulges. All surface flow has been lost.
Extensive cracking across a rockbar
Subsidence-induced Impacts on Upland Swamps
Image courtesy of
A huge chunk from what was once a waterfall has broken away.
What was once a beautiful, long, crystal-clear pool has drained like a bathtub once the bedrock underlying the sandy bottom was cracked.
Upland swamps are the key to the integrity of the rivers which rise on the Woronora Plateau. They are nature’s “leaky storages”, capturing rainfall and holding it like vast sponges, releasing water gradually to the river system for months after rain, forming the baseflow for the rivers. This why rivers continue to flow even when there’s been no rain for months.
A healthy upland swamp in the Dendrobium mine lease area.
A key indicator species is Banksia robur, the swamp banksia, seen here in the foreground.
This swamp has since been undermined.
The upland swamps of the Woronora Plateau have been listed as Endangered at State and Federal level. This has not protected them from mining.
A typical outflow from a healthy swamp. Crystal-clear, filtered water is being released to a minor creek which will join other creeks from other swamps to feed the storage dams.
The exploration phase of mining involves seismic testing to see where the coal seams are and to map the geology of the area. Straight lines are cleared through bushland for this purpose. This one is regenerating slowly.
An exploration borehole has required a large cleared area.
Vent shaft construction:
As the mining area moves further away from the pit top (Mt Kembla) vent shafts have to be built to expel stale air and draw in fresh air.
The no. 3 vent shafts at Dendrobium.
Surface disturbance for infrastructure
The only remediation that has been done in the Special Area has been to 2 rockbars on Waratah Rivulet. Polyurethane resin (PUR) has been used in an attempt to restore the water holding capacity of the rockbars to retain water in the pools behind them.
PUR is just like the expanding foam you can buy in an aerosol can at Bunnings. Millions of litres of it were pumped, at vast expense, into the cracks and it has oozed out everywhere with these unsightly results.
We have no confidence in the durability of this material. Cracks could open up again with the slightest earth tremor.
Hundreds of holes were drilled in the river bed for injection of PUR to form a “grout curtain” behind the rockbar. Results, according to the Sydney Catchment Authority, have only been partially successful with about 50% of the water being retained.
Gas venting due to fractures opening up in the bedrock. This fugitive gas emission is not quantified nor factored into the calculation of greenhouse gas emissions from the mine.
In 2012, the water was
carrying a heavy load of iron contamination
which exceeds Australian Drinking Water guidelines
To do this in the Special Area requires massive disturbance for: road construction, power supply, construction equipment, site offices and facilities for workers etc. over many months.
A typical larger creek (Sandy Creek) which flows into Lake Cordeaux.
When the swamp is undermined (green line) the underlying bedrock is cracked and the water level plummets immediately, then flatlines. There is no longer any response to rainfall as the swamp cannot hold water.
A monitoring graph showing piezometer readings of the groundwater level (blue) in a swamp as it fluctuates in response to rainfall (red).
LONGWALL MINE 7
LONGWALL MINE 8
An exposed bedrock section in a swamp, showing cracking due to subsidence.
The cracking extends across the swamp through the sediments which are now bone dry.
The Banksia robur are the first plants to show signs of stress and then die.
Another smaller swamp (Swamp 15b), showing the healthy, lush vegetation growing in a wet environment.
Walking through such an area involves squelching and wet feet......
Highly stressed Banksia roburs in Swamp 15b which is no longer so healthy and lush after undermining. There is no known method of remediating a cracked swamp, as in order to fix the cracked bedrock you’d have to remove the swamp sediments and so destroy the swamp anyway.
This swamp was undermined in 2003 and then suffered a very intense fire. A healthy swamp will not be destroyed by fire, as only the surface will burn, not the wet sediments and plant roots. A desiccated swamp affected by undermining is highly vulnerable to fire, as even the sediment will burn. If fire is followed by heavy rain, massive erosion then occurs as there is nothing to hold the sediments together. Here, vast canyons have been scoured out, leaving walls of rock-hard, dry sediment.
Vegetation changes then occur as the dry sclerophyll species such as wattles and eucalypts invade once the swamp dries out.
This shows total swamp collapse.
Despite what we know will happen, approval was given for the first 5 longwalls here, which will undermine and destroy 4 major upland swamps. All the reasons given for this approval were economic.
The most recent (Feb. 2013) approved expansion in the Metropolitan Special Area, Dendrobium Area 3B, shows that lessons from past mining are still being ignored.
Parallel lines of these fissures opened up at BHP Billiton's Dendrobium mine in Area 2. They extend for hundreds of metres across a slope. Remediation of these cracks is not undertaken unless they are across a road or in an open area like this which was in a power line easement. It is considered that attempts to fill the cracks in bushland would be too damaging to the area, so they remain as massive pitfall traps for animals but this is not even monitored.
The fissures here were up to 1m wide at the top. Rainfall which should run off to the storages will instead infiltrate deep into these cracks and very likely be lost to the storage.
Massive rock outcrops like this can split asunder due to subsidence.
Where clifflines are undermined, cliff falls can occur. Here in Dendrobium Area 1 there were 11 cliff falls, but only 6 were originally reported, due to a less than comprehensive monitoring regime
Massive rocks dislodged from the cliffline tumble down into the valley – Dendrobium Area 1.
A cleared wasteland now remains at the worksite for the injection process. This was pristine bushland before.
Sydney's water -
Number of people who rely on Sydney's water supply
2,581,850 Mega Litres
Capacity of Sydney's dams
Cities and regions that rely on Sydney's water supply
Number of major dams supplying water to Greater Sydney region
Amount of land set aside around the water storage and infrastructure as the Special Areas
Some supporters of this mining say that mining has been occurring here beneath the water catchment since the 1800's.
And therefore it's not a problem...
From the collections of the Wollongong City Library and the Illawarra Historical Society
This is how they mined in the 1800's.
By Dr-Victor-von-Doom (Own work) [CC BY-SA 3.0 (http://creativecommons.org/licenses/by-sa/3.0)], via Wikimedia Commons
This is how they mine now....
Longwall with hydraulic chocks, conveyor and shearer
Unfortunately, deep beneath the Special Areas south of Sydney a number of coal mines are currrently operating.
They are extracting high quality metallurgical (coking) coal, used to make steel, and a smaller quantity of thermal coal for domestic power and heating.
After longwall mining
Before longwall mining
The Sydney Catchment Authority (SCA) manages this area which includes the outer catchments and the inner catchments (cross-hatched).
The inner catchments are called Special Areas; they are no-go zones for the general public.
It is because these large areas of bushland have been set aside for water supply that Sydney has such excellent water, requiring minimal treatment.
Woronora Dam supplies a large part of Sutherland Shire as well as areas down to and including Helensburgh
These are the coal mining leases in relation to the Special Areas south of Sydney
Four dams of the Upper Nepean system
built in the early part of the 20th century
Person of average adult height.
Image courtesy of BHP Billiton
Undermining can cause surface fissures like this to open up across the landscape. These can be up to 15m deep.
What does the future hold for Sydney's water catchment?
The Sydney Catchment Authority estimates that by 2030, 91% of the Special Areas will have been undermined.
Not only are broader areas being mined, the depth of mining in the Special Areas is also increasing.
Wollongong Coal’s Underground Expansion Project seeks to mine a third seam of coal beneath two previously mined seams.
Next to be mined
“The prediction of the impacts of subsidence on swamps, creeks, groundwater and infrastructure depends on the accuracy of the subsidence predictions themselves. However, it is a fact that these predictions of subsidence, and in particular tilts and ground surface strains, is fraught with uncertainty. The main reason for this is the impact of geological structures, often unknown, and, in the case of multi-seam mining is exacerbated by limited precedent.”
Ref: Pells P.J.N. & Pells S.E. 2011 Review of subsidence and related facets of the NRE No. 1 Colliery - underground expansion project draft environmental assessment Consultants report by Pells Consulting for Gujarat NRE. Ref P043.R2 (Final draft) Oct 2011.
There is little precedent for three tier mining. This is the first time a third seam of coal has been mined in the Southern Coalfields.
This is taking place close to the Cataract Reservoir.
Major Project Assessment:
Russell Vale Colliery Underground Expansion Project (MP 09_0013),
Secretary's Environmental Assessment Report to the Planning Assessment Commission
Furthermore, despite widespread opposition to Coal Seam Gas, the NSW State government refuses to rule out CSG extraction wells in the Special Areas.
The Report of the NSW Chief Scientist and Engineer, "On measuring the cumulative impacts on activities which affect ground and surface water in the Sydney Water Catchment", May 2014 concludes that the current approach to protecting the water catchment by Government agencies "seems to be preventing development that could cause obvious, disastrous cumulative impacts" (p. 33). However, the Report acknowledges that the data that informs the assessment of cumulative impacts is inadequate and fragmented.
Longwall mining may cause a range of impacts both above and below the surface....
What can I do?
Incredibly, Sydney is the only city in the world that allows longwall mining beneath a publicly owned water catchment.
And yet in this, the largest city of the driest inhabited continent on earth, the government appears to lack the will to act to protect our drinking water supply.....
Cataract Dam, Source: http://www.sca.nsw.gov.au/
1. Contact your local member of State parliament and tell them about your concerns. Ask them what their position is on protecting Sydney's water from destructive coal mining. (Don't let them get away with just talking about CSG.) Ask them to support mining no-go zones around Sydney's water catchments.
2. Support a broad community alliance to Protect Sydney's Water. See http://www.nature.org.au/campaigns/coal-and-gas/protect-sydney-s-water/
3. Share this prezi
Coal mines in Sydney’s special catchment areas already drain about 3 billion litres a year from the water supply — enough water to fill 1,200 Olympic-sized swimming pools – and the problem is only getting worse.
Source: Coal Seam Gas Impacts on Water Resources, Sydney Catchment Authority, 2012
We need mining no-go zones around water catchments
There should be no new mining approvals in our water catchments
There should be a plan to ensure the phasing out of active mines with appropriate transitional arrangements for existing operations in our water catchments
A zooming presentation about the impacts of coal mining on Sydney Water Catchment Special areas.
Illawarra Residents for Responsible Mining (irrm.org.au)
This is what we need:
Can you help?
These areas are the sole supply of water for the Illawarra (280,000 people) and Macarthur (264,000 people) regions, as well as the Sutherland Shire.