Release Date: Sep 1, 2016
The Coronado National Forest is designing a system to augment environmental cleanup work previously performed at the Lead Queen Mine on the Sierra Vista Ranger District.
An unusually wet summer monsoon season in 2014 contributed to colored runoff in some drainages in the Patagonia Mountains. This included waters tinted white, yellow, orange and red flowing from the Lead Queen Mine adit, indicating release and oxidation of mineralized waters and sediment.
An environmental cleanup was completed in February, 2016 to reduce or eliminate downstream movement of waste rock containing elevated concentrations of arsenic, lead, and other heavy metals, and to prevent acid mine drainage from entering into Harshaw Creek.
Adits and shafts were closed with polyurethane foam or bat-friendly metal gates. Waste rock was placed in a consolidation cell and capped. Wire gabion baskets were installed downstream of the main adit. Burlap bags filled with zeolite were placed inside the baskets to remove heavy metals and trap sediment particles.
On or about August 9, a short-duration, high-intensity precipitation event on the order of a five- year event (based on National Oceanic and Atmospheric Administration point precipitation frequency estimates, and radar data) passed through the area, resulting in damage to the completed work.
Forest engineering, minerals and geology staff and U.S. Geological Survey scientists inspected and evaluated the damage, and determined a more sustainable and robust system was needed to meet project goals.
Coronado National Forest personnel are assembling a team of U.S. Geological Survey scientists and U.S. Forest Service professionals with expertise in remediation of similar conditions. Once in place, the team will design the improved system and identify a timeline to implement the project.
Further developments will be announced through future news releases.
