Study of Abandoned Uranium Mining Impacts

On Private Land Surrounding US Forest Service Land In Western South Dakota


                    

 

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Download the Final North Cave Hills Project Report Here

Download the Final North Cave Hills Groundwater Pumping Test Report Here

Download the Preliminary North Cave Hills Windblown Dust Report Here

Download the North Cave Hills Groundwater Pumping Test Manuscript Here

Welcome to the new SDSM&T/USFS abandoned uranium mine study website.  Please note this website is currently under construction, and is continuously being updated.  Also note that this website will provide download capabilities for current and future reports and presentations related to the various project phases.

Dr. James Stone - Principle Investigator

Dr. Larry D. Stetler - Co-Principle Investigator

South Dakota School of Mines and Technology

 

Introduction

This website has been developed as part of the North Cave Hills Area Abandoned Uranium Mines Impact Investigation that is being conducted under a Joint Venture agreement between the United States Department of Agriculture-Forest Service (Forest Service) and the South Dakota School of Mines and Technology (SDSM&T), and a subcontract with Oglala Lakota College (OLC).  Funding for this on-going study has been provided through US-EPA CERCLA.  This website describes both the field and laboratory methods and results to evaluate potential environmental impact of abandoned uranium mining and exploration sites in the North Cave Hills, Harding County, South Dakota.

Research that will be conducted during the course of this project will focus on the extent that contaminated materials may have moved off of the Lands administered by the Forest Service onto private property. Soil samples will be collected in locations that may have received sediment, water samples will be collected in major drainages leading away from abandoned mine sites, and the air quality will be evaluated both upstream and downstream of the mine sites to determine if there is an impact from blowing dust.

Uranium Mining History

The coal geology of the Cave Hills area was described in 1916 by Winchester et al. Coal was mined as several locations for the next several decades and was followed in 1950 by the first uranium prospecting operations. High interest in the mineral resources of the area led Baker to compile a treatise on the general and structural geology in 1952. Using this and other work, uranium mining in coal bed E began in the Riley Pass district in 1954. Soon afterward, mining increased with the discovery of uranium in carbonate and phosphatic rocks and by 1955, uranium mining was occurring on the western margin South Dakota as well. Mining occurred primarily in coal units in the Ludlow member of the Tertiary Fort Union Formation. Overburden was removed and dumped over the side slopes to expose the uraniferous coal which was mined, later burned to ash, and then the uranium was extracted. In the mid 1960s most mining activity ceased and the abandoned mines are today almost like they were at that time. Subsequent erosion of mine waste plies has created gullying, sheetwash, tunneling, and landslides, all creating a potentially hazardous situation immediately around the mine sites.

Only a few coal claims were located in Harding County prior to 1920. Uranium exploration began in 1954 when the Atomic Energy Commission decided to fly airborne surveys over the Slim Buttes (approximately 20 miles to the east of the Cave Hills). According to Curtiss (1955), “Messrs. Ellis and Fiegen, pilots from Spearfish, were scheduled to fly over the buttes, but a high wind precluded their operations. Instead, they flew over the Cave Hills and recorded high anomalies. As a result, they staked the first claims on August 15, 1954. Since that time, activity in this area has been intense.”

Active mining started around 1954. Mine sites are located primarily within an approximately two-mile broad, northwest trending strip crossing the central North Cave Hills (“hot zone”). Mining was permitted under the General Mining Laws and Public Law 357, which required no form of restoration. Most mining and mining prospects are located on U.S. Forest Service land, but at least two actively mined sites and several prospects and exploration cuts and digs are situated on private land surrounding the North Cave Hills. These uranium mines are abandoned coal strip mines located on relatively flat areas along the top of the buttes. Mining consisted of the removal of up to 80 feet of overburden to reach the uranium bearing lignite beds (“ore zone”).

Extensive mining activity occurred in the early 1960s in an effort to supply contracts for uranium. Active mining in the area ceased in 1964. Documented mine sites, spoils, exploration activities and subsequent erosion of spoils cover almost 1,000 acres (see figures below). Some of the spoils were pushed over the edges of buttes onto the steep slopes below the rim rocks during mining. Additional spoils have been deposited on these slopes by subsequent water and/or wind transport.  At these sites, the sandstone cliffs are mostly covered, and the overall slope angles are highly over-steepened. The spoils are also mostly void of vegetation, and their composition is also conducive to water channeling and tunneling. All these conditions contribute to high erosion rates and also make these sites highly prone to sliding and slumping.