Integrated Engineering Alternatives for Mine Site Remediation at the Captain Jack National Park Site in Boulder County, Colorado

The Captain Jack (CJ) Superfund Site is located in Boulder County, Colorado, within the Left Hand Creek Watershed.  In the late 1800s through the early 1900s, several mining companies consolidated in the area known as the Big Five with a resulting mine complex/mill considered to be one of the largest gold and silver producers in Colorado.  The resulting mining activity left behind significant volumes of waste rock, tailings and several miles of open and collapsed underground tunnel workings.

 In the 1980s, the Environmental Protection Agency discovered fisheries and wetlands impacts in the Watershed.  These impacts were suspected to be associated with discharges of metal-contaminated water, and the CJ facility was identified as the primary source.

 Based on human health and ecological risk assessments, remedial action objectives were developed to protect from risks associated with highly acidic water and metals contaminants identified in mine waste and surface water.

 Remediation alternatives were developed with close community involvement and strict adhereance to Colorado and Boulder County historic structure preservation.  Several integrated alternatives, specifically focused on mine tailings and acid mine drainage remediation, were developed and evaluated in detail as follows:

- Off-Site Disposal of Principal Threat Waste (PTW) and Capping
-  On-Site Repository for PTW and Capping
-  On-Site Repository for Contaminated Soils
-  Bulkhead in Big Five Adit
-  In-situ mine pool neutralization with phased biochemical reactor
-  Precipitation Water Treatment System for Big Five Adit Drainage and;
-  Biochemical reactor treatment of Big Five Adit Drainage

Based on detailed engineering evaluations, a combination of repository and in-situ mine pool neutralization construction will likely be implemented in order to adequately address the site risks.