The Gilmore Mine Site is in a sparsely populated area of eastern Idaho, approximately 17 miles south of the nearest town of Leadore. Mining operations began in the early 1880s and ceased in 1965, generating mine waste piles over an area of approximately 15 acres and an estimated total volume of over 110,000 cubic yards. The historic mining area had up to 60 patented mine claims, with six major mines. Mines in this district produced primarily lead and silver, along with small amounts of gold, copper, and zinc.
Migration of contaminated mine waste material through aerial dispersion and surface water runoff has impacted approximately 140 acres, including a 90-acre Townsite comprised of 560 lots, some occupied, ranging from roughly 3,300 square feet to 12,000 square feet.
Site sources have resulted in releases of lead, arsenic, and other metals to downgradient and downwind lands impacting approximately 140 acres, with additional impacts to intermittent streams and drainages as well as a perennial stream (Texas Creek). The Idaho Department of Environmental Quality (IDEQ), under a Site Assessment Cooperative Agreement with EPA, conducted two investigations at the Site in 2016 and 2017. Investigations revealed that the highest concentrations of lead and arsenic in source area mine waste are 41,200 milligrams per kilogram (mg/kg) and 818 mg/kg, respectively. The highest lead and arsenic concentrations found in soils within occupied Townsite lots and surrounding lands are 29,500 mg/kg and 484 mg/kg, respectively. The highest concentrations of lead in intermittent streambeds downgradient of the source area is 39,900 mg/kg, while arsenic is 577 mg/kg. Arsenic is present in sediments within the perennial portion of Texas Creek at 8 mg/kg. During the 2017 event, EPA conducted ambient air monitoring which revealed concentrations of lead in the Townsite as high as 0.435 ug/mg3.
Based on observations during the 2016 field event, IDEQ estimates the potential residential population within ½ mile of the Townsite center to be 21, with a potential seasonal population of an additional 22. However, use of the Townsite appears to have increased since 2016. The Townsite is undeveloped and there are no public utilities available. Lodging is primarily off-grid cabins, camping, or recreational vehicles. Other transient populations also pass through the Site while recreating. Outdoor recreation activities are the primary draw to the Site. Activities may include, but are not limited to, all-terrain vehicle (ATV) riding, biking, driving, horseback riding, and walking. Meadow Lake Road – United States Forest Service (USFS) Road #2, which transects the southern portion of the Townsite - is the primary access road to the Meadow Lake Campground, a popular summer destination within the Salmon-Challis National Forest.
In July 2023, the U.S. Agency for Toxic
Substances and Disease Registry (ATSDR) released a Health Consultation summarizing its findings from the
evaluation of heavy metal
contamination in the Gilmore area. ATSDR’s findings identified risks from lead contaminated
soils and made
recommendations for environmental agencies, Site residents, and visitors.
ATSDR’s health consultation report indicates that recreational and
residential users at the
Site face health risks due to physical contact with contaminated soil and the potential for ingestion of
metals. Potential
human exposure routes include direct
contact with and ingestion of contaminated soil. Human receptors include
residents, visitors, and passers
by. The potential for exposure is increases
with the frequency and duration of exposures.
EPA conducted an Emergency Response in August 2023 to preform dust suppression on the roads in the Townsite.
