USGS Response to Possible Metals Contamination from Legacy Mines in the Patagonia Mountains Region and Adjacent Areas, Southeast Arizona and a Template for Future Mineral Environmental Emergency Response

Science Center Objects

USGS is conducting sampling, monitoring, and modeling in the Patagonia Mountains and nearby regions in Arizona to identify contaminant risk potential of legacy and proposed mine sites and to develop classification criteria for predicting vulnerabilities and targeted sources and sinks of metal contaminants.

Image shows orange, discolored water in a small canyon

Orange, iron-rich precipitate (ochre) from outflow of Lead Queen mine tunnel, after late September 2014 monsoon storm. Photo by Glen E. "Gooch" Goodwin, Photographer - used with permission.

Science Issue and Relevance

In late September, 2014, unusually heavy monsoonal rains were followed by citizen observations of bright orange "sludge" flowing in streams in the vicinity of the Lead Queen and Trench Camp Mines in the Patagonia Mountains. Lead Queen is an abandoned mine located on U.S. Forest Service land, and Trench Camp is a mine site that was remediated in the 1970s and is currently managed by Asarco Multistate Environmental Custodial Trust. At Lead Queen, flushing of adits and shafts by rapid inflow of rainwater apparently led to the mobilization of iron- and aluminum-rich sludge, which has mostly settled in the upper canyons near the mine site. Similar flow occurred at the Trench Camp site due to the failure of a sediment dam and overflow of the wetlands area established as part of the remediation.

Critical issues include how these other contaminants have dispersed through the watershed, the extent to which they have been deposited in sediments that can be remobilized in future events, the potential for future contaminant outflows from these two sites as well as other sites in the selected southeast Arizona mountain regions, and developing a plan for future USGS response to this and similar events in other areas. With the USGS's experience with rapid response, unbiased science, and the nationally and internationally recognized quality of its data and protocols, the USGS is in a unique position to aid with and conduct sampling, monitoring, and modeling to provide a comprehensive perspective on the ongoing environmental hazards posed by the legacy of mining in the Patagonia Mountains and, in general, predict surface and groundwater potential vulnerably in new start-up areas.

Methodology to Address Issue

Project objectives are to:

  1. Identify contaminant risk potential of legacy and proposed mine sites in the Santa Rita, Atascosa, and Patagonia Mountains and develop a classification criteria for predicting vulnerabilities and targeted sources and sinks of metal contaminants.
  2. Leverage existing USGS science activities to facilitate a broad synthesis of regional watershed functional elements that are key interactive components within mineral resource impacted areas.
  3. Synthesize regional watershed information into models describing contaminant sources, pathways, sinks, and their spatial dynamics linked to developed mineral resource areas; understand their fluxes related to seasonal precipitation and regional climate trends.


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