2020

Sub-Surface Remediation Continued

What to know:

After the emergency release and resulting fish kill, the sub-surface remediation activities were paused as the EPA, CDPHE, and contractors were hired to revisit the approach. While the original goals of the remedy remained the same, new methods and techniques were tested in Summer 2020 and implementation continues today. These updated activities include: (1.) again, fill the inner mine workings with mine pool water in order to reduce toxic acid mine generation and prevent fresh surrounding ground water from entering the mine workings and becoming toxic, and (2.) opposed to treating and circulating water with crushed limestone, use a combination of Sodium Hydroxide injections and biological remediation to lower the pH and promote bacterial productivity, respectively. The biological remediation uses existing bacteria to biologically drive precipitation of toxic metals and improve water quality.

This photo shows the most recent sub-surface remedy set up at the Big Five Tunnel. From Left to Right shows the standby treatment facility and two large tanks of Sodium Hydroxide to be used in the current mine pool treatment activities. November 2020.

Sulfate Reducing Bacteria (SRB) and their role in treating Acid Mine Drainage (AMD)

  • SRBs are a group of anaerobic (no oxygen) bacteria. Instead of breathing with oxygen, they breathe with sulfur. A great source of sulfur can be found in AMD!
  • With a little food (organic material), these bacteria will start reducing sulfates in AMD and eventually precipitate out metals with sulphides.
  • Bonus: this whole process generates alkalinity, which neutralizes the water.

If the new remediation efforts can feed these bacteria enough to kick start SRB productivity, then the biological water treatment will continue on with very little future operations!

CDPHE and EPA and their contractor intend to use Sulfate Reducing Bacteria in their sub-surface bioremediation technique to improve water quality at the mine. Read CDPHE’s most recent sub-surface remediation face sheet here.

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