1. Mine Rehabilitation at Yerranderie
Photo: Silver Peaks Processing area
Note extensive environmental damage caused 80 years ago is still a visible scar on the landscape.

2. Location of Yerranderie
100 km southwest of Sydney
Special Area within Warragamba catchment (Schedule 2 lands) and close to the Kanangra Boyd Wilderness Area
Headwaters of the Tonalli River – water travels 12km through protected bushland into Lake Burragorang
Photo: Colon Peaks capture dam site prior to rehabilitiaion work
Yerranderrie is located within a Special Area nominated to protect Lake Burragorang and near to Kanangra Boyd Wilderness Area. The “private town” and mines are tourist facilities and visited by bushwalkers. It was essential to take these factors into account when developing an appropriate mine rehabilitation strategy.

3. Location of Tonalli River and Yerranderie Derelict Silver Mining Field
Lake Burragorang
Yerranderie Silver Mining Field
Map notes:
Aerial photo taken over Yerranderie Silver Mining Field
Tonalli River discharges into Lake Burragorang
Tonalli River is sinuous and transverses through rugged terrain
Cleared area within Mining area is identifiable from the aerial view
This map also indicates the remoteness of the site
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0 km 1
Scale

4. Yerranderie Timeline 1899-1906 mining 1st grade ore
processing plants: crushing ore
small mines operated
1920s six major mines operated
Labour dispute lead to closure of large scale mining
Warragamba Dam built, access to Yerranderie not available from the East, Yerranderie became a remote site
limited mining and site left as derelict mining field
Photo: Colon Peak Processes Area Pile
Ore discovered in 1871 by Aboriginal labourers
Silver/lead mining area in late 19th and early 20th centuries
1912 – 1915 population peaked at 2000 people in the township

5. Water Quality Issues Large mounds of processed tailings
Minimal run-off controls from processing site
Metal contamination above acceptable levels
Metals of concern include
Copper
Lead
Zinc
Aquatic ecosystems within and immediately downstream potentially compromised
Photos
Top: Colon Peak Processing Area
Bottom:Silver Peaks Processing Area
No measurable impact on water quality at Warragamba Dam offtakes (dilution factor)
Large mounds of processed tailings - high concentration of contaminants mainly heavy metals and sulphides

6. Water Quality Issues
Erosion and lack of vegetation lead directly to environmental problems
Sediments eroding from processing sites and washing into Tonalli River
Photo: Kerry’s shaft
Yerranderie photo prior to any rehabilitation works. Picture shows the lack of vegetation and erosion potential of the site

7. Water Quality Issues
Crushing ore reduced grain size, increasing surface area exposed to air and the potential of erosion
Exposure to air and water – potential for Acid Mine Drainage through oxidisation of sulfur in Pyrites (Sulfuric Acid) and the release of metals in low pH conditions
Photo: Colon Peak Processes Area shows one aspect of the site before any work had taken place. The bare slope of land was highly vulnerable to erosion

8. Who is responsible for rehabilitation works?
Significant collaboration required between stakeholders/partners:
Private landholders
Sydney Catchment Authority
NSW National Parks and Wildlife Service (now Department of Environment and Conservation)
NSW Department of Primary Industries – Mineral Resources
NSW Department of Land and Water Conservation (now Department of Lands)
Containment work completed successfully at the Yerranderrie processing areas in May 2000
Project took four years to reach completion

9. Yerranderie Derelict Silver Mining Field
Over 200 adits, shafts, tunnels and trenches in an area over 10 km square
Underground mining methods used
Ore brought to surface
Most material on surface is 2nd grade ore = high in sulfides
Photo:Silver Peaks Mining Area
Ore characteristics & Mining methods
Ore is oxides of silver and lead in association with zincblende, pyrite and chalcopyrite, copper oxide and arsenopyrite (sulphide rich ore)

10. Rehabilitation Aims
Contain processing tailings and contaminated sediment
Reduce sediment transport to the Tonalli River
Detain runoff and redirect clean waters around the processing sites
Minimum impact on the environment and cultural heritage of the area
Photo: During containment works

11. Understanding the Yerranderie site
Field Studies
Geology, soil, topography, climate, flora, fauna, heritage
Why?
To ascertain potential impacts of remedial work
To consider long term implications of actions and allow for further works later
Field studies to gain a comprehensive understanding of the Yerranderie site took approx. 1 year of work to complete. These studies informed the decisions and prioritising process for rehabilitation works.
Understanding the specific nature of the Yerranderie site meant that the rehabilitation works could take into account potential harm from the rehabilitaion works and take preventive measures to maintain the integrity of the site.
Photos
Top and Bottom: Native vegetation
Right: Kangaroo

12. Minimise Negative Impacts
Yerranderie mine rehabilitation strategy counters potential impacts by including protection measures for:
Soil erosion and water quality
Flora and fauna
Heritage
Photos: Water quality testing
Soil Erosion and Water Quality protection measures:
Minimise disturbance area to reduce erosion
No wet weather works permitted
Erosion control - silt fences / brushmatting
Restore tracks and disturbed areas
Water sampling to ensure water quality changes are detected
Flora and Fauna protection measures:
Minimise vehicle passages
Tag access tracks and important vegetation
Remove only quicker growing common native species
Don’t disturb habitat areas eg fallen logs
Heritage protection measures:
Site surveys with local Aboriginal authorities
Non Aboriginal Heritage assessment undertaken
Works located on periphery to the major heritage sites

13. Rehabilitation Choices for Yerranderie
Alternative actions considered
Onsite burial of processed material
Remove material to another site or a single processing area
Soil conservation works
Reprocessing of tailing material
Complete site remediation
Do nothing: no proactive action – allow tailings to erode ‘naturally’
Photos:
Top: Silver peak processing site
Bottom: Silver Peak dam site (pre containment work)

14. Soil Conservation Works
Aim to divert clean water around contaminated sites and capture contaminated water and tailings
This option chosen as it has
Limited damage to heritage items
Reduced risk of groundwater and surface water contamination
Reduce further pollution potential

15. Four Major Sites Chosen for Rehabilitation
Silver Peaks Processing Area
Colon Peaks Processing Area
West of Wollondilly Mine Processing Area
Kerrys Shaft Processing Area
4 major sites chosen for rehabilitation works. Processing consisted of crushing ore & separating fine and coarse materials by washing to extract the silver, lead and small quantities of gold.
No smelting processes undertaken on the site
Anecdotal evidence of minor arsenic roasting extraction undertaken at Silver Peaks processing site.
Photo: Silver Peaks processing area

16. Silver Peaks Processing Area
What happened?
Built earth diversion bank above processing site and a sediment containment pond below the processing area
Why?
To divert clean water around the contaminated sediments. Water enters a stilling basin to reduce flow velocity and erosion
What did it achieve?
Processing area catchment, water volumes, velocity and overal sediment movement into constructed dam greatly reduced
Mining works had changed the natural drainage lines of the ‘natural’ catchment area, to maximise the water flow into processing areas. This human altered landscape increased the amount of run off towards the contaminated areas.

17. Silver Peaks Works – Lower Dam
Before work
After work
Runoff captured in Dam

18. Silver Peaks Works Clean water diversion bank – before and after works
Photo
Left: Silver Peaks Processing area prior to diversion bank work
Right: Silver Peak Processing area post diversion bank works

19. Kerrys Shaft – Lower Dam
During construction
After work water capture
Water capture constructed area act as a sediment pond. Recent inspections (2004) revealed that the sediment pond was functioning well & almost full of sediment
Before work

20. Outcomes of the Rehabilitation Works
Water quality results from captured water in dams
poor quality
low pH
elevated metal levels especially for Silver Peaks
sediment captured
Detention of tailings runoff in catch ponds is reducing the sediment an poor water quality moving downstream
Rehabilitation works have a positive effect on water quality and ecology downstream

21. Water Quality Monitoring Results: July 2000
Analyte
Kerry Shaft Dam
Silver Peaks Dam
Colon Peaks Dam
ANZECC % Trigger Levels
Total Copper ug/L 12
N/A 62
1.4
Total Lead ug/L
1550
1360
3.4
Total Silver ug/L
<1 3 4
0.05
Total Zinc ug/L
5200
54800
11100 8
Results December 2000
Analyte
Kerry Shaft Dam
Silver Peaks Dam
Colon Peaks Dam
ANZECC % Trigger Levels (for slightly disturbed ecosystems) pH
7.7
2.8
6.3
Electrical Conductivity uS/m
480
1345
680
30-350
Total Copper ug/L 12
5010 8
1.4
Total Lead ug/L 28
1120 32
3.4
Total Silver ug/L 1 16
<1
0.05
Total Zinc ug/L
3060
50700
3990
Water collected in the ponds was found to contain elevated levels of cadmium, lead, zinc, arsenic and nickel in excess of the levels in both 1992 ANZECC and 1999 draft ANZECC guidelines for protection of aquatic ecosystems. Detention of tailings run off in the catch ponds is reducing the heavy metal loads entering the Tonalli River and Lake Burragorang system. The works are then having a positive benefit on the water quality and ecology of the downstream area.
ANZECC = Australian and New Zealand Environment and Conservation Council

22. Ongoing Monitoring and Further Works
Development of a comprehensive Rehabilitation Action Plan for the Yerranderie Mine Area
Awarded Environmental Trust Grant: $631,000 provided by NSW Government for 3 years of work
Longer term studies of mines
Water quality monitoring program on Tonalli River
Flora/Fauna studies, especially of bat habitat in mine shafts
Metallurgical Study on feasibility of reprocessed tailings
Aboriginal/Non-Aboriginal Heritage Study
Risk assessment of all mine sites for public safety

23. Photography Credits
All photographs in this presentation are reproduced with kind permission of the copyright owner: Sydney Catchment Authority.