Screening Techniques for Legacy Mine Land (LML) Sites Using Data Mining and Site-specific Studies in the Western U.S. Completed

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Science Issue and Relevance

There are tens of thousands of abandoned mines and prospects in the western U.S., many of which have continuing harmful effects on the environment. Currently, prioritization of these LML sites for receiving the limited funds available for remediation is often driven by geopolitical factors, with little or no systematic evaluation of the scientific factors dictating the probability of meeting desired clean-up goals.

Applying an integrated science-based approach in decision-making process about where and how to remediate mine sites may increase chances for remediation success, and help avoid investments in watersheds where such efforts are unlikely to succeed due to high natural background or other factors. The USGS has under-utilized datasets that could be valuable for evaluating LML sites and prioritizing sites for future modest restoration efforts.

Methods to Address Issue

This project includes two tasks representing a two-stage approach for screening LML sites for remediation at different scales.

Task 1: GIS-based screening techniques. The objective of this task is to assemble and interpret databases relevant to past mining and current environmental conditions in a GIS model covering central Colorado. Key databases include: (a) the new USGS USMIN database to identify all mine-related features; (b) USGS NWIS database, USEPA Storet database, and USGS Central Colorado Assessment Project database for stream water chemistry; (c) USGS hydrothermal alteration mapping from hyperspectral ASTER satellite data for the abundance of exposed sulfide minerals. The GIS model will be analyzed to identify "yellow-light" sites where stream metal concentrations only moderately exceed regulatory levels and apparent mining-related sources are few and well defined.

Task 2: Field characterization of candidate sites. The objective of this task is to develop straightforward sampling regimes for application at candidate "yellow-light" sites identified through Task 1 to provide more specific information on stream water chemical conditions and potential metal sources. A reconnaissance level sampling program will be initially applied at a set of candidate sites, followed by a more comprehensive sampling program performed at 1-2 priority sites selected based on the reconnaissance data. Field characterization methods will include stream tracer dilution studies, stream habitat quality evaluation, solids sampling for chemistry, and surface water and groundwater sample for chemistry, multiple isotopic tracers, and age.