Captain Jack Mill - Lefthand Canyon

This is a National Priorities List (NPL), or "Superfund," hazardous waste site. While we’re the lead agency for remediation of the site, the EPA Superfund Program provides technical support and input on all remediation-related activities to ensure the objectives of the Superfund program are met.

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Community involvement

​Site summary


  • At the headwaters of the Lefthand Creek Watershed in a narrow valley about 1.5 miles south of Ward in Boulder County.


  • Mining for gold and silver began in this region in 1861 and continued intermittently until 1992. Camp Frances, near Ward, was started in the early 1890s.
  • Combined ores from several mines, including the Big Five Group’s Adit, Ni-Wot, Columbia and Dew Drop, came down to the camp by way of the side entrance tunnel.
  • Processing was carried out in the Dew Drop Mill or the larger Big Five Mill, located on the side of the gulch below the camp.
  • The Colorado and Northwestern Railroad was built through the Big Five/Camp Frances area to the town of Ward to service the mining area.
  • The Captain Jack Mine (also known as the Black Jack Mine) operated intermittently as an underground mine following its patent approval in 1917.
  • The Big Five Mine is located about 500 feet upstream from the mill and operated without a permit, so there is no way to track its official history. It is unknown how long it originally operated before it was shut down.
  • The Big Five Mine consists of an adit (side tunnel), a large waste rock pile and a settling pond.
  • The Mill Works area includes several lagoons previously used for settling tailings from the mill. The lower portal consists of the Black Jack adit and the contents of a shed.
  • Other mine wastes include waste material in Lefthand Creek and waste rock from the mine tunnels.
  • The EPA added the Captain Jack site to the National Priorities List (NPL) on Sept. 29, 2003.

Environmental concerns


Contaminants include:

  • Lead, arsenic, thallium, zinc, manganese, copper, magnesium, cadmium, aluminum, calcium and iron.
  • Site contaminants of highest concern are lead, arsenic and thallium.


  • Elevated levels of metals and other contaminants have been found in surface water and sediment samples from Lefthand Creek and its tributaries and from wetlands fronting along the creek.
  • Lefthand Creek is one of the sources supplying drinking water to approximately 15,000 water users.
  • Groundwater samples from two nearby wells show elevated levels of metals.
  • Uncovered tailings, ore concentrates and surface soil contaminants could pose a threat of dust emissions, especially to nearby residences.
  • Elevated metal concentrations in sediments and water entering Lefthand Creek affect aquatic life.

Site remediation

  • The selected remedy controls both surface and subsurface contamination sources.
    • The subsurface contamination remedy included installation of a bulkhead, mine pool mitigation and long-term monitoring.
      • The concrete bulkhead plugged the draining mine adit, impounding the mine water.
      • The mine pool environment has reduced oxygen levels, which, when coupled with an injected caustic chemical, increased the pH of the water to a neutral condition.
      • The monitoring system ensures effectiveness of the remedy to determine whether additional action is needed.
    • The surface contamination remedy involved excavating all site material containing the contaminants of concern in concentrations above the remedial action levels and placing it in two onsite consolidation cells.
  • Remedy construction was completed in November 2012.

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