USGS Geological Research Activities with the U.S. Bureau of Land Management

Idaho Resource Assessment Projects

These scientific investigations are designed to understand ore deposition and extent, alteration, weathering, ore concentration, and trace element concentration, mobilization, and transport processes.

Large, high-grade phosphate is present in economically mineable quantities in the Permian Phosphoria Formation, which constitutes the Western Phosphate Field. Four active open pit mines in the southeast Idaho phosphate district produce phosphate from the Meade Peak Phosphatic Shale Member. Federal land management agencies, such as the BLM and the USFS, gain income from the development of phosphate resources, which is a leasable commodity.

In a response to a request by BLM in 1998, USGS scientists initiated a multidisciplinary study of the Phosphoria Formation and related rocks (pictured left). The study is being conducted in collaboration with the USFS, University of Idaho, Department of Environmental Quality, and regional phosphate producers. The goals of this cooperative effort have been focused on the characterization of the primary phosphate ore bodies and adjacent rock units. USGS scientists associated with this project are studying the elemental, mineralogical, petrochemical, and stratigraphic character of phosphate mineralization within the Southeast Idaho Phosphate District and in selected portions of the Western Phosphate Field. Impacts on the environment associated with the presence and development of the Phosphoria Formation are also being examined.

Concentrated initially in Southeast Idaho (pictured left), this study is enhancing our ability to evaluate additional phosphate mineralization and to anticipate, assess, and mitigate environmental hazards, such as selenium toxicity, that are spatially associated with the existence and societal use (mining and reclamation) of the phosphate. Department of Justice, at the request of USFS, has used data resulting from these studies, particularly those related to selenium, to recover environmental damage and reclamation costs from the parent company.

The Idaho Department of Environmental quality is also using geochemical data resulting from this work to develop remediation plans for the amelioration of selenium (and other toxic metal) contaminant problems in SE Idaho that have resulted from mining of phosphate. For example, based on data resulting from the project, land management agencies are determining processes for selenium in leachate to be treated and removed by adsorption onto iron oxyhydroxides. Project results have indicated that some plants, especially alfalfa and sedges, are strong accumulators of selenium and other heavy metals. The USFS, based on resulting contaminant element and analyses of plants and soils associated with phosphate mine waste units, has changed seed mixtures required for reclamation of the waste piles and changed the design of waste unit construction.

Associated with these deposits are a range of issues that challenge land management and conservation planning, including estimation of phosphate resources, for long term land use planning and sustained yield of fertilizers and elemental phosphorus. BLM is using phosphate resource calculations and resource mapping information for land-use planning on BLM-managed lands in southeast Idaho.

The Coeur d'Alene mining district in northern Idaho is one of the world's largest producers of silver and one of our Nation's major historical producers of lead and zinc. Environmentally sound mining activities occur within the district today. However, historical ore processing methods and episodic floods have dispersed metal-enriched sediment at least 150 miles downstream from the mining district in Idaho and Washington. Significant human and ecological impacts result from the ingestion of metal-enriched dust, soil, and waters.

Federal, State, and local agencies, along with residents in and near the district, are working to reduce human and wildlife health effects from the contaminated sediments and additional environmental impacts, such as reduced water quality. Remedial efforts over the last decade have significantly reduced the human impacts in the most contaminated part of the drainage basin (Bunker Hill Superfund site), but chronic human and ecological impacts outside that area has seen little improvement.

The USGS has undertaken a number of geologic, hydrologic, and biologic studies in the impacted Coeur d'Alene basin. Research goals are to:

• develop new understanding of the occurrence, quantity, and environmental characteristics of ore deposits and mining wastes in the Coeur d'Alene basin and of the fundamental processes that influence their distribution, mobility, and availability
• quantify metal sources to and metal transport in the streams and groundwater of the basin
• quantify the biologic impacts of the metals and to identify the pathways of metals to the biota.

The Mineral Resources Program's work on the Coeur d'Alene Project is scheduled for completion at the end of FY02. This work has focused on:

• development of models of Coeur d'Alene type mineral deposits that summarize key geologic, genetic, grade-tonnage, and environmental data
• develop baseline data on the spatial and depth dependent distribution of metal-enriched sediments, soils, and waters in the Coeur d'Alene-Spokane River basin
• develop understanding of the processes that control distribution, transport, and fate of metals in the basin
• determine the controls on solid-phase speciation of the metals and its relationship to the availability of metals to biologic uptake during ingestion of particles.

These studies have provided important relevant to the development of remediation strategies for the basin and to the monitoring of the effectiveness of remedial actions. The studies have been conducted in partnerships with Federal and State agencies, including the Environmental Protection Agency, U.S. Fish & Wildlife Service, U.S. Forest Service, BLM, and the States of Idaho and Washington.