RECLAIMING HYDRAULIC GOLD MINE SLUICE TUNNELS

Transcription

1 RECLAIMING HYDRAULIC GOLD MINE SLUICE TUNNELS (BANC PIC :99--ffALB) Authors: HUMPHREYS, Richard D. State Water Resources Control Board 1001 I Street Sacramento, CA Rhumphreys@waterboards.ca.gov WEAVER, Rick United States Forest Service, Tahoe National Forest 631 Coyote St. Nevada City, CA rweaver@fs.fed.us SHIPLEY, Brad United States Forest Service, Tahoe National Forest 631 Coyote St. Nevada City, CA bshipley@fs.fed.us LAWLER, David Bureau of Land Management 2800 Cottage Way, Suite W-1834 Sacramento, CA dlawler@blm.ca.gov WEDEN, Chris United States Environmental Protection Agency, Region 9 75 Hawthorne Street San Francisco, CA, not available at this time

2 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.

3 Hydraulic Gold Mining Develop in several areas starting about Required Capital. Required manpower. Required an industrial base. Cherokee Mine

4 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

5 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.

6 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

7 Why clean up tunnels over 100 years later? Many sluice tunnels are open. Many tunnels are mined for mercury that contains gold. Many tunnels still drain their mine pits. Lakes form in pits over blocked tunnels. Photo by Powell Photo by Powell

8 Polar Star Mine, EPA CERCLA Removal, July 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.

9 Goals Prevent human exposure to mercury. Prevent mercury removal and dispersal. Prevent mercuryimpregnated wood from being removed and reused. Photo by Powell

10 Methods Uses Tunnel mucking High pressure washing. Mercury recovery via gravity separation

11 Stabilizing the entrance Clean up Scenes Tunnel bulkhead Washing the floor Finished product

12 Clean up Scenes Vapor monitoring Press day Mucking

13 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. Summary

14 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.

15 Goals Eliminate Human exposure potential. Eliminate mercury export from site. Address physical safety hazards. Restore site.

16 Tunnel excavation to remove contaminated soil and improve drainage. Tunnel floor sealing to isolate residual contamination. Mine pit grading to promote pit drainage. Revegetation. Methods Used

17 Clean up Scenes Site surveying Concrete/soil mix testing Pit grading Final grade

18 Result Restored mine pit Excavated tunnel Constructed Stream

19 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.

20 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.

21 Goals Remove mercury from the tunnel. Eliminate mercury export from site. Address physical safety hazards. Restore site. Mercury contaminated tunnel sediment

22 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

23 Methods Ditch sealing Trommel Concentrator bowl Spiral concentrator Panning Hg

24 Summary Mercury exposure and export potential have been reduced. Physical safety hazards have been addressed. New drainage scheme is successful.

25 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