RECLAIMING HYDRAULIC GOLD MINE SLUICE TUNNELS
• Authors: • HUMPHREYS, Richard D. • State Water Resources Control Board • 1001 I Street • Sacramento, CA 95814 • [email protected] • WEAVER, Rick • United States Forest Service, Tahoe National Forest • 631 Coyote St. • Nevada City, CA 95959 • [email protected] • SHIPLEY, Brad • United States Forest Service, Tahoe National Forest • 631 Coyote St. • Nevada City, CA 95959 • [email protected] • LAWLER, David • Bureau of Land Management • 2800 Cottage Way, Suite W-1834 Sacramento, CA 95825-1886 • [email protected] • WEDEN, Chris • United States Environmental Protection Agency, Region 9 • 75 Hawthorne Street San Francisco, CA, 94105 • E-mail not available at this time
(BANC PIC 1905.17175:99--ffALB) Early Gold Mining
• By individuals • Simple technology, little capital needed. • Effective for rich, easily worked placer deposits. • Continued by Chinese as they had few employment options. Hydraulic Gold Mining
• Develop in several areas starting about 1853. • Required Capital. • Required manpower. • Required an industrial base.
Cherokee Mine Hydraulic Mining
Monitors Eastman’s collection G117, T 271, UCD Flumes
Photo by Powell Waste
Society of California Pioneers, LH0808 Society of California Pioneers, LH0801 Sluices The Sawyer Decision
• 1883 Court Decision 1 The [defendant companies – North Bloomfield et al]… are perpetually enjoined and restrained from discharging or dumping into the Yuba river… any of the tailings, bowlders [sic], cobble stones, gravel, sand, debris or refuse matter. • (Supreme Court Judge Lorenzo Sawyer, January 7, 1884) • 1884 Court Decision 2 No person, natural or artificial, has the right, directly or indirectly, to cover his neighbor’s land with mining debris. • (State Supreme Court decision upholding earlier Gold Run case, November, 1884) • 1893 Statute The Civil Code of the State of California is hereby amended by adding thereto a new title, to be known as title nine….The business of hydraulic mining may be carried on within the State of California wherever and whenever the same can be carried on without material injury to the navigable streams, or lands adjacent thereto. Sluices
• Sluices recovered gold. • Mercury was used to “catch” fine gold. • Mercury was lost during slucing. • Mercury is still found in sluices and their foundations today.
Photo by Powell Why clean up tunnels over 100 years later? • Many sluice tunnels are open. • Many tunnels are “mined” for mercury that contains gold. Photo by Powell • Many tunnels still drain their mine pits. • Lakes form in pits over blocked tunnels.
Photo by Powell
Polar Star Mine, EPA CERCLA Removal, July 2000. • Easily accessible. • Historic sluice actively “mined” for mercury. • Mercury-impregnated wood from the sluice was “salvaged” for planters. • Mercury in the sluice discharge threatened water quality. Goals
• Prevent human exposure to mercury. • Prevent mercury removal and dispersal. • Prevent mercury- impregnated wood from being removed and reused. Photo by Powell
Methods Uses
• Tunnel mucking • High pressure washing. • Mercury recovery via gravity separation Clean up Scenes Stabilizing the entrance
Tunnel bulkhead
Washing the floor Finished product Clean up Scenes Vapor monitoring
Press day Mucking Summary
• Human exposure and export potential were reduced substantially. • The remedy is still functioning well. • The method used needed good access for heavy equipment. • Mercury was not recovered effectively.
Sailor Flat (USFS – CERCLA)
• Mercury had been reportedly “mined” from the tunnel. • Mercury could be easily found in the tunnel. • Local biota had elevated mercury. • The site exported mercury. • Physical safety hazards were present. Goals
• Eliminate Human exposure potential. • Eliminate mercury export from site. • Address physical safety hazards. • Restore site. Methods Used
• Tunnel excavation to remove contaminated soil and improve drainage. • Tunnel floor sealing to isolate residual contamination. • Mine pit grading to promote pit drainage. • Revegetation.
Clean up Scenes Site surveying Concrete/soil mix testing
Pit grading Final grade Result Restored mine pit
Excavated tunnel
Constructed “Stream” Summary
• Mercury exposure and export potential have been eliminated. • Physical safety hazards have been addressed. • New drainage and vegetation are successful. • The site provides better habitat than it did prior to clean up. Boston Mine (BLM – CERCLA)
Tunnel Miner • Mercury was mined from the tunnel. • Mercury was spilling from the tunnel. • Local biota had elevated mercury. • The site was easily accessible. • The tunnel was unsafe. Goals
• Remove mercury from the tunnel.
• Eliminate mercury Mercury contaminated tunnel sediment export from site. • Address physical safety hazards. • Restore site.
Methods
• Remover mercury contaminated sediment from tunnel. • Seal tunnel floor. • Recover mercury from contaminated sediment • Grade the mine pit to promote pit drainage. • Revegetation.
Slusher Unit Ditch sealing Methods
Trommel
Concentrator bowl
Panning Hg Spiral concentrator Summary
• Mercury exposure and export potential have been reduced. • Physical safety hazards have been addressed. • New drainage scheme is successful.
Conclusions
• The clean up goals for the tunnels at each were similar. • The methods used to meet those goals differed primarily as a result in differences in access.
Society of California Pioneers, LH0796