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North Star Mill Tailings - Iron Springs Mining District

 
Site Contact:
Steven Merritt
On-Scene Coordinator

(merritt.steven@epa.gov)

Site Location:
Ophir, CO 81426
 response.epa.gov/NorthStarMill

The North Star Mill Tailings Site is a time-critical removal action to mitigate the hazards associated with historical mining activities at the site. The site is a 5-acre parcel that was patented as a mill claim in the 1920s. The North Star Mill was a 50-ton-per-day ore mill constructed on the claim in 1924 to service the nearby Carbonero Mine. It operated heavily through the 1930s, processing ore and shipping tailings via wooden flume to the Carbonero Tailings Pile along Howards Fork, just east of Ophir. It was partially demolished in the 1950s by the Silver Bell Mining Company. During operations, a significant quantity of rejected ore and waste rock accumulated next to the mill and processed tailings were spread and spilled on the site. These stockpiles and associated tailings contain potentially hazardous concentrations of lead and arsenic, along with other lower concentration non-toxic metals. The time-critical removal action will consolidate and cap these waste materials under a vegetated cover and manage surface water to prevent infiltration into the pile, thereby significantly reducing the hazards present at the site.


Collecting samples from eroded toe of lower mill tailings pile. Furthest extent of contaminated toe approximately 150' from lower mill tailings pile. Lower mill tailings pile and distressed vegetaion downslope due to eroded tails. Lower mill tailings pile 'crater' where milled material flushed through a defective sluice. Rental yurt on property adjacent to upper mill tailings pile, similar to the one used year-round by the property owner and his family just above the mill site. Surface flow channel in the middle of the upper mill tailings pile shows evidence of heavy metal precipitation and low pH flow. The waste rock pile, adjacent to the old mill, sits just uphill from a crushed rock pile. Panoramic photo of the upper mill tailings pile from the old mill. Photo shows the rental yurt and the original sluice location used to transport milled material down to the valley. Crushed rock still in the hoppers of the old mill building. View down the slope of the mill and upper tailings pile. Image shows some of the mill debris and the waste rock pile. Geotechnical investigation of North Star Mill Site. Excavating test pits in the lower mill tailings pile. Depth of tailings in lower mill tailings pile, where repository will be built. Test pit development at the toe of the migrated tailings downslope from the lower pile. Test pit of migrated tailings, showing only a thin veneer of tailings over otherwise good topsoil and fill material. View of the repository location from the southwest corner of the property following most of the tree clearing and grubbing. Initial excavation of the Lower Mill Tailings to create a clean access road for the haul truck. Overview of Lower Mill Tailings area following grubbing and clearing of trees to make room for the repository. Excavation of the migrated tailings on the southwest end of the Lower Mill Tailings Pile and a view of the repository site. In-situ X-Ray Fluorescence (XRF) of excavated areas of the Lower Mill Tailings Pile to ensure residual soils are below the action level for lead and arsenic. Excavation of the Lower Mill Tailings Pile and the installation of secondary silt fences to prevent re-contamination of clean soil due to precipitation runoff. Depth of tailings across the Lower Mill Tailings Pile southwest of the Repository during excavation work on site. Panoramic photo of the excavation site and the edge of the migrated tailings in the Lower Mill Tailings Pile. Installing silt fence to prevent erosion of tailings into excavated clean area at the southern end of the Lower Mill Tailings Pile Conducting in-situ XRF analysis on native soils beneath excavated tailings to ensure that all metals have been removed to the action levels. Excavation of the bench at the toe of the repository to provide additional storage volume and reduce the amount of cover required. Pulling back the tailings on the Lower Mill Tailings Pile to safely excavate additional clean fill from the bench. Panoramic view of the repository area, the excavated bench, the stockpile of clean cover and fill material, and the Lower Mill Tailings Pile. Excavation of the southwest corner of the North Star Mill reveals two wooden pipes that presumably were used to transport tailings to the flume. Both contained high concentrations of metals. View of the North Star Mill ruins following tree clearing and extensive excavation of material around the southern foundation. Carbonero Mine can be seen through the trees in the distance. Dumping first loads from Upper Mill Tailings Pile and area around North Star Mill foundation. Loading excavated materials from around the mill foundation into the dump truck bound for the repository. Collapsed wall of mill foundation following removal of wood debris. Some tailings behind the collapsed wall and under cracked floor. Removing the tailings from the decaying flocculation basins on the second tier of the North Star Mill. Demolishing the last remaining wall of the ore bin on the uppermost tier of the North Star Mill. Mechanical difficulties with the off-road dump truck required a trained mechanic visit the site. Segregating contaminated and uncontaminated wooden debris around the upper tier of the North Star Mill. Excavating the waste rock stockpiles adjacent to the mill and hauling it to the repository. Compacting the toe of the repository with the loaded dump truck to improve stability. Mechanical issues plague the bulldozer, leaving it stranded, without hydraulic pressure, on the toe of the repository at the end of the day. Continuing to excavate and haul contaminated mill debris and waste rock from the ore bins and stockpiles adjacent to the mill. START Bosco holding a large and high-grade chunk of galena, a lead mineral, from the stockpiles adjacent to the mill. Filling the excavated bench at the toe of the final repository footprint. Note the pile of tailings in the background before shaping. More loads added to the bench and in the process of compaction. In the background, much of the initial shaping for the repository has been completed. Excavating and hauling the final stockpile adjacent to the former mill. View of the former mill from the bottom, including the concrete debris pile and some of the wood debris from the structure. Area west of the foundation that contained two wooden pipes that were used to drain tailings from the mill. Trench and pipes were excavated. View of the repository, almost at full design capacity for the first phase. An extension will be built near the toe to handle any additional material excavated. Panoramic view of the repository and clean fill stockpile from the north and west. Dump access road is in the center of the photo. Excavating the east side of the former North Star Mill. A view of the top of the repository through the access road cut into the trees where tailings have migrated over the years. Creative solutions to ensure that the haul truck only traverses contaminated soil between the excavation and the repository. Areas on the north, south, and west sides of the former mill have been excavated. Screening equipment brought to the Chapman Gulch Borrow Site. Excavation of a second bench at the toe of the repository to make room for additional volume. Panoramic photo of repository and second bench looking west across the slope. Excavation of soils contaminated by site runoff down slope of mill in forested area. Developing Chapman Gulch borrow site and screening excavated soils. Removing final debris from mill, placing concrete rubble at base of foundation, and rebuilding road using clean fill at the top of the mill. Recovering dump truck from haul road when it slid downhill in the mud after a heavy rainstorm. START surveying the borrow site and the screened rock that will be used to construct drainage channels around repository. ERRS hauling the excavated soil from the Upper Mill Tailings area and hand-digging the contaminated material from around the base of the solar panels. Placing the contaminated material into the repository is nearing completion. Contaminated material extending six feet deep was excavated from this area where a historic mine tramway anchoring system was buried. Placement and compaction of the contaminated material has been completed and clean cap material (brown material near dozer) is being installed on top of the contaminated material. Placing rock in the repository ditches and the lower unvegetated area where mill tailings have been removed. Rocked drainage feature located at the toe of the repository. Some of the aspen trees removed to access contaminated areas were reused as water diversions to mitigate slope soil erosion. Condition of the borrow site following completion of excavation and screening. Footprint was surrounded by large rock and will be used by USFS next summer. Constructed repository before revegetation effort, including rocked channels and the cross-slope channel to prevent soil loss. Panoramic photo of the constructed repository and drainage features. Seed mix used in revegetation effort includes several native grasses and forbs. Beginning seeding and chipping some of the smaller diameter slash for mulch. Rolls of erosion prevention matting arrive at the site to cover disturbed areas and prevent soil loss until vegetation takes hold. ERRS spreading lime on cap and other disturbed areas to ensure that soil pH is adequate to support revegetation effort. ERRS chipping aspen trees into mulch that would be spread very thinly over the erosion prevention matting to buffer pH, add organic matter, and maintain soil moisture. ERRS spreading chipped aspen mulch over erosion prevention matting south of the repository, which has been covered with lime. Adding lime to the upper slope, just south of the former mill location, where soil pH was low beneath where the excavated tailings were. Unloading a truck of imported topsoil that would be spread over the lime-amended site soils to provide fertile ground for seeds. Mixing lime into the uppermost site soils with the excavator in an effort to increase the pH and neutralize the acidity caused by the excavated tailings. ERRS rolling out erosion prevention matting over the repository and the cross-slope channel designed to mitigate soil loss from the cap. ERRS beginning to water in seeded, fertilized, and amended soils that had been covered with erosion matting and aspen mulch. ERRS spreading imported topsoil over a second layer of lime to prevent any pH reduction due to capillary action during precipitation or snowmelt. ERRS spreading seed and fertilizer on imported topsoil just prior to placement of erosion prevention matting. ERRS continuing to water areas of the site to ensure seeds will germinate properly and lime is worked into site soils. View of constructed runoff channels designed to carry water from the slopes above the repository into the channel that flows east of the site. Panoramic view of the road leading down to the repository as ERRS continued watering seeded areas. This road was mulched and logs were placed across it to capture soils and facilitate revegetation. Panoramic view looking west from the top of the repository at the final condition of the site following watering and all revegetation efforts. ERRS seeding and fertilizing the imported topsoil just south of the former mill site. The second addition of lime is visible near the log placed across the slope. ERRS replacing a culvert that carries adit drainage from the New Dominion Mine across Ophir Pass Road. The old culvert was further damaged by hauling material from Chapman Gulch. Finished culvert carrying adit drainage into the wetland just east of Ophir. Panoramic view of the final condition of the upper slope following all revegetation efforts, including placement of logs to reduce runoff velocity and soil loss. Final condition of the area around the former mill following all revegetation efforts.
For additional information, visit the Pollution/Situation Report (Pol/Sitreps) and the Notices sections.