Location and Drainage
The mine is located at 40°40′20″N 122°31′40″W / 40.67222°N 122.52778°W / 40.67222; -122.52778Coordinates: 40°40′20″N 122°31′40″W / 40.67222°N 122.52778°W / 40.67222; -122.52778 in the Klamath Mountains of Shasta County, about 9 miles northwest of Redding. The mine area is drained by several creeks which ultimately enter the Spring Creek Reservoir, formed by the Spring Creek Dam, and finally the Keswick Reservoir formed by a dam across the Sacramento River. This reservoir is a major source of drinking water for Redding.
The drainage water from the Iron Mountain Mine is the most acidic water naturally found on Earth; some samples collected in 1990 and 1991 have been measured to have a pH value of -3.6. The drainage water endangers fish, including winter-run Chinook salmon, a federally listed endangered species that spawns in the Sacramento River. Salmon kills have been noted since 1899.
The mine opening contains huge stalactite-stalagmite structures that span from floor to ceiling and are composed of rhomboclase and other iron sulfate minerals.
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