Intro

The Lake George Mine is situated at Captains Flat, approximately 50km south east of Canberra.  The mine operated from 1892 until 1962, producing lead, zinc, copper, pyrite, silver and gold.

Extensive rehabilitation work has been conducted since closure to control erosion, improve safety and to control tailings pollution leaving the site. Current and ongoing issues include Acid Mine Drainage (AMD) seepage and heavy metal contaminants leaving the site, with zinc being the primary contaminant of concern.

Although previous rehabilitation has been undertaken, AMD issues persist.

Current Site Description

The mine covers approximately 100 ha with the main mine workings extending underground to a depth of 619m,  Numerous shafts and adits are present at the surface. Derelict structures for ore storage, processing, loading and transport remain at the site. There are two large mine tailings dump areas (northern and southern).

Rehabilitation Works

Initial rehabilitation works to reduce pollution were undertaken in 1966 and 1968 by the NSW Department of Mines but were only partially successful.

Subsequently, significant works were undertaken in 1976 to a value of $2.5M.  These included stabilisation of mine waste dumps to prevent ongoing erosion and leaching and to minimise the risk of major collapse.  Works here also included drainage modifications to Forsters Creek to minimise the inflow of water into the mine.

The 1976 works were aimed at protecting and upgrading the quality of the waters of the Molonglo River as a supply of water for drinking and agricultural uses.  They also aimed to protect and improve the biological and aesthetic quality of the waters of the river and ensure the maintenance of water quality in Lake Burley Griffin.

Due to the large area covered by the site, a further $1.01M has been spent by the Derelict Mines Program on various sections of the site since the early 1990’s, including:

  • 1993 erosion control works,
  • 1999-2002 survey and Remediation Action Plan (RAP),
  • 2000/01  works-contaminated materials removal,
  • 2002/03 relocation of waste slag,
  • 2004 RAP preparation,
  • 2005/06 works-erosion control/structure safety,
  • 2005/06 Heritage assessment,
  • 2007/08 works - sediment control and de-silting,
  • 2009/10 works - drainage mill/load out site, safety fencing,
  • 2011 works-revegetation works-load out area,
  • 2012 consultancy – design for stabilisation of the northern face of the South Tailings Dump,
  • 2012 works-erosion control – north face of the south tailings dump
  • 2013 works-site safety works to rectify subsidence issues.

The DMP is currently undertaking a review of the available information within the various studies that have been undertaken to see if further works are warranted at the site.

Mine History and Heritage Value

Even though the mine operated from 1892 until 1962, operations were carried out in two main phases: from 1882 to1889 and1937 to 1962.  The site closed due to the depletion of economic grade ore.

Prior to 1937 production at the mine was relatively minor, processing approximately 205,000 tonne of ore to produce 3800t of Copper, 26t of silver and 16000oz of gold.

The second phase of operation (1939-62) processed over 4 million tonnes of complex copper-lead-zinc ore, producing approximately 243,000t of Lead, 406,000t of Zinc, 27,000t of Copper, 7.4million ounces of Silver and 220,000 ounces of Gold.

All of the workings were underground with the lowest levels reached being 619m.  At this level, drives were extended a number of times to locate the ore bodies, but 1960 saw the diamond drilling at the end of the drives failing to locate any ore of economic importance.

Cross section of part of Captains Flat mine

The importance of the Captain’s Flat mine during the post 1937 phase requires elaboration.  While dwarfed by the mighty Broken Hill field (which was one of the largest in the world), it was one of the largest base metal mining fields in NSW, if not Australia. The Mt Isa and Mt Lyell fields were larger, but primarily copper producers.  For example, in 1943 8,579 and 8,633 tons of lead concentrates were extracted from Mt Isa and Mt Lyell respectively compared to 11,850 tons from Captains Flat.

The Captains Flat mining field is significant for its contribution to base metal mining in Australia, and in particular, New South Wales, over a period of 80 years. It was the major mining site in southern NSW in the 1890’s and again in a period 1937-62.  In the 1930’s to 1960’s period, Captains Flat was one of the most important mining sites in Australia, as producer of lead, silver, zinc and sulphur and to a lesser extent copper and gold.  Its production was particularly valuable during World War 2. The highly complex mineralogy of the ore body and consequently the varied and changing processing technology was a unique aspect of mining of Captains Flat.

During both periods Captains Flat was one of the largest towns in the southern mining region, having a considerable impact on the development and settlement of the area.