North Creek Mill
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The North Creek Mill site is located approximately 24 miles northeast of Arco, Idaho.
North Creek originates on the semi-arid western flank of the Lemhi Range and flows southwest, sinking into the ground long before reaching the Little Lost River Valley. The southern portion of the Lemhi Range consists of Mississippian- and Ordovician-age limestone, dolomite and quartzite units. Lead and zinc mineralization is localized along the contacts between the dolomite and quartzite.
Although most of North Creek is diverted 0.3 miles below the old mine site to irrigate hay pastures to the west, the Lower North Creek channel can still flow during extreme events and maintain low flows for a month or two during high-water years. Below the irrigation diversion, North Creek is an ephemeral stream flowing only during periods of high snowmelt runoff and large rainstorm events. This watershed is susceptible to rain-on-snow events that produce high-flow floods.
Silver and lead ores were initially discovered in the North Creek area in 1882. Upstream from the mill site, the Wilbert Mine produced ore from about 1906 to 1931. While most mining in the area was completed by 1931, continued ore-reprocessing activity occurred intermittently through 1967. Mills on Camp and North Creeks used gravity separation or arsenic/other chemical compounds to separate the metals. During this period, two earlier mills were located upstream, one near the mouth of the North Creek Canyon just below the mine, and one on Upper Camp Creek. These mills resulted in four tailings ponds (shown on the topographic map).
In 1945, a mill was built on Lower North Creek reprocessed tailings from the existing ponds. The reprocessing created extremely fine tailings readily subject to mobilization. An intense rainstorm in 1967 caused already full tailings ponds to overtop, flow downstream, and spread out across the entire floodplain. In 1982, runoff combined with already-saturated ponds, breached the dams and caused another tailings flow.
The primary water quality issue is high lead and arsenic concentrations mobilized by flood events. While the mill was in operation, North Creek's water quality was highly impacted by acid-mine drainage from the mill. The North Creek Mill site consisted of a dilapidated mill, four breached tailings ponds, and tailings high in lead, arsenic, and zinc distributed along a five-mile length of the ephemeral stream channel.
During the past 60 years, tailings have been subject to mobilization with episodic flood events. High flows resulted in deaths of about 160 cows between 1934 and 1982. North Creek is an ephemeral tributary to the Little Lost River, which is a 303(D) listed stream with concerns for threatened bull trout. While this area is remote from human populations and water wells, primary concern has been for the poor surface water quality and effects on livestock and habitat. Fencing efforts prior to 1982 have not been sufficient to isolate the contamination from livestock.
Remediation efforts at North Creek have been aimed at removal of the most contaminated tailings from the channel and floodplain. A secondary purpose was to reconstruct the channel to prevent future channel migration and further downstream distribution of any remaining metals during flood events.
The North Creek Mill was one of BLM’s first mine-waste removal actions done prior to the formal initiation of the AML program in the mid-1990s. Flooding in 1981-1982, prompted BLM to remove some of the tailings (20,000 yd3) and place them in a repository above the floodplain. This mill site has been listed on the CERCLIS with EPA, ID #IDD980726087. Remediation actions in 1999 were prompted through the Clean Water Act.
In 1999, the major cleanup was completed. The mill debris was removed, an additional 4,700 yd3 of contaminated tailings were removed from floodplain, 3,300 ft of stream channel was reconstructed below the mill site to handle a 100-year flood event (300 cfs), and the previous repository was enlarged. XRF sampling was conducted to guide the extent of tailings removal necessary. During the channel reconstruction, an estimated 46,000 yd3 of material was moved. Drop structures and a terminal silt-settling basin were constructed to deposit sediments and prevent further downstream movement of contamination. Further soil and vegetation sampling was conducted downstream to determine the level of metals uptake in vegetation below the project site. This information will be used to guide future grazing allotment management. Re-seeding was completed during 1999-2000.
Tailings subject to erosion and downstream deposition have now been removed from the floodplain immediately downstream from the mill site. Channel reconstruction has been designed to support future 100-year flood events without transporting metal-contaminated tailings further downstream. Cooperators on the project included Idaho Department of Environmental Quality and Butte County.
For additional information regarding this project, contact the Field Office AML specialist or call the Upper Snake Field Office at (208) 524-7500.
- Located 24 miles northeat
- 3 miles north of Howe, Idaho in the Little Lost River Valley
- Mining of silver and lead ores from 1906 to 1931
- Intermittent mill tailings reprocessing from 1945 to 1969
- Episodic flooding events distributed tailings downstream resulting in subsequent cattle deaths
- Significant levels of soil contamination of arsenic, lead and zinc in dispersed tailings
- Poor surface water quality
- Livestock deaths
- Spreading of heavy metals downstream in the Little Lost River Valley
- 1983: Initial removal of some tailings from floodplain and placement in repository
- 1999: Removal of additional tailings; consolidation in expanded repository; channel reconstruction; drop structures and silt-settling basins; revegetation
Upper Snake Field Office | 1405 Hollipark Drive | Idaho Falls, ID 83401
208-524-7500 | Fax: 208-524-7505 | Office hours: 7:45am - 4:30pm, M-F