LAND REHABILITATION at GOLDEN CROSS MINE, 8 YEARS AFTER MINE CLOSURE

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LAND REHABILITATION at GOLDEN CROSS MINE,8 YEARS
AFTER MINE CLOSURE

• Craig Ross
• Dennis Crequer (Environment Waikato)

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Mining History

• Gold first mined in Waitekauri Valley in 1875
• Gold discovered at Golden Cross in 1892
• Underground mining with a stamping battery and
  cyanide extraction until 1905
• Sporadic mining continued until 1917

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Golden Cross Mining Camp, 1890s (Bert McAra, Gold
Mining at Waihi)
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Some site factors

• Mining area 130 ha (total area 400 ha)
• Altitude 270 to 460 m a.s.l.
• Rainfall gt2000 pa, high intensity storms
• Allophanic (volcanic ash) soils
• Andesitic rhyolitic rocks, tuffs and sediments
• Adjacent land uses DoC Forest Park pastoral
  farming

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Some Mining Information

• Mine development started 1990
• Open Pit Underground Mining(11 km tunnels to
  300m below surface)
• Employed 120 243 staff
• Mine closed December 1998
• Gold production 584,000 ozSilver 1,675,000 oz
  Worth NZD 430M (2001 prices)

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A visual journey of Golden Cross Mine from 1990
to 2006

• Focusing on land rehabilitation

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Sept. 1990 Mine development
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1993
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1994
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1996
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1997
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1998 partially capped
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1999/2000 capping nearly completed
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2002/03
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2005
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1994
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1997
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2000
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2005
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AMR
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Natural revegetation of exposed AMR 2005
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AMR by Underground Portal
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Capped grassed AMR 2005
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Oldest native plantings, 2 years old
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1990 plantings in 2005
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1992 native plantings
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1996
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1992 plantings in 2005
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Direct vegetation transfer
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Direct transfer of vegetation 2005
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Tailings Lake wetland plantings
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Wetland plantings around the tailings lake
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Conservation of Swamp Maire
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Conservation of frogs Hochstetters frog
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Natural revegetation of 1910-20 mullock heap
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Riparian enhancement plantings Waitekauri V.
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Riparian enhancement
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Wetland enhancement
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Wetland enhancement 2005
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Conceptual rehabilitation (after 5 years)
Closure Plan
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During closure rehabilitation
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Actual rehabilitated site,4 years after closure
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Concluding Summary

• Land rehabilitation at Golden Cross Mine set a
  new standard for closure of large scale opencast
  mines in New Zealand

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• On-going site management issues are(i) weed
  (grazing management) pest control(ii) earth
  slips (erosion)(iii) underground mine water
  treatment(iv) maintenance of drainage
  systems(v) impacts of public access (for
  recreation tourism)

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Acknowledgments

• Weve appreciated working with Cyprus AMAX/Coeur
  Golds mine managers, staff, consultants, and
  other peer reviewers during the 16 years of
  activities with the Golden Cross Mine site,
  particularly the environmental staff and
  post-closure site managers
• We also acknowledge the aerial photographs by
  Mark Sampson