Protecting Public Health and the Environment.

Former Bayhorse Mining District - Custer County

The Idaho Department of Parks and Recreation (Parks) purchased former mine properties in the Historic Bayhorse Mining District in Custer County, Idaho, to develop as Idaho’s newest state park.

Looking down-valley at Bayhorse town site.

Site Background

The properties consist of approximately 500 acres, distributed over several square miles in Custer County, Idaho, approximately eight miles southwest of Challis, Idaho. The site is included in the Idaho Historic Society's register of historic places.

The Bayhorse mining area deposits were first noted in 1864 by a prospector traveling (with two bay horses) through the mountains along the Salmon River. In 1873, the first lode claim was located, and in 1877, a major lead-silver vein was discovered at the Ramshorn Mine. By 1878, a considerable rush to the area had begun, and the Beardsley Mine had gone into production. In 1880, a 30-ton smelter was constructed, and within two years charcoal kilns were constructed to provide the smelter with a local fuel source. By this time, the town of Bayhorse had a population of about 300 and a complex of substantial, permanent buildings.

In 1883, an aerial tramway was constructed at the Ramshorn mine to transport ore down to wagons that served the smelter. The smelter was closed in 1889, reopened briefly in 1893 and 1894, but by 1897 was permanently closed and later dismantled (Idaho State Historical Society 1980). Production continued from the Bayhorse mines until 1925, with ore being transported to the smelter in Clayton, Idaho. A mill was constructed and limited operation began in 1951.

Total production for the area has been estimated at more than $10 million (Alt et al. 1989), including approximately 200 oz of gold, 6.3 million oz of silver, 6.6 million lb of copper, 37 million lb of lead, and 39,000 lb of zinc. Environmental concerns at the site are related to the historic mining activities.

Charcoal kilns near Bayhorse town site
Mill at Bayhorse town site

Regulatory History

There is no regulatory history at this site beyond the assessment activities discussed below.

Site Activities

In November 2003, DEQ provided technical support to EPA Region 10 by conducting Preliminary Assessment (PA) activities at five properties within the site (Town site, Beardsley-Excelsior Mine, Skylark Mine, Ramshorn Mine, Pacific Mine, and the Mill and Smelter). Based on the PA results, DEQ recommended more detailed site investigations prior to Parks' purchase of the site. At Parks' request, DEQ's Brownfields Program agreed to fund assessment activities at the five properties. DEQ contracted to have Maxim Technologies perform the assessment activities. In June 2004, Maxim provided Parks and DEQ with an assessment report.

Parks and DEQ conducted a number of meetings to discuss developing Parks' reuse plans with the aim of minimizing environmental risks identified in the report. Parks and DEQ then agreed additional risk evaluation efforts were needed to make a final determination regarding the risks associated with the site. Accordingly, DEQ's Brownfields Program committed to contract with Terragraphics Environmental Engineers, Inc. to conduct remaining assessment and risk evaluation activities. The extensive due diligence on the part of Parks and DEQ led to the purchase of these five former mining properties with Parks able to assert the Bona Fide Prospective Purchaser defense to CERCLA liability. Parks subsequently applied for and received nearly $800,000 worth of cleanup grants from EPA to complete cleanups at these properties in support of proposed reuse as an addition to Idaho state parks.

Ramshorn Mine tram
Ramshorn Mine ore loading shed

Redevelopment Plans

Parks has or is in the process of preserving and restoring historic features within each property to provide recreational and educational opportunities to the citizens of Idaho and other users. This area already attracts tourism by offering the public the opportunity to visit the historic mining operations along the Yankee Fork of the Salmon River—Bonanza and Sunshine Mines. By establishing Bayhorse as state park, Parks will provide an additional destination for this area's tourism base, providing economic benefits to the City of Challis and Custer County.  The Townsite, Beardsley, and Pacific mine sites have been cleaned up and redeveloped and are open for use to the public.  The Ramshorn and Skylark mine sites will begin cleanup during the 2012 field season.

Parks and DEQ worked closely with the Idaho State Historic Preservation Office to ensure that relics, buildings, and fencing were restored, maintained, and installed in a manner consistent with Section 106 of the National Historic Preservation Act.

Staff Contacts

Brownfields Program Coordinator
Eric Traynor
DEQ State Office
Waste Management and Remediation Division
1410 N. Hilton
Boise, ID 83706
(208) 373-0565

Related Pages

Brownfields Assessment Program

Brownfields Grants

Voluntary Cleanup Program