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Bonnanza Mine
1986
1996
Baker
Oregon
N 44° 59'
W 117° 05' 12" |
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| Mining
in the background and reclamation in the foreground |
|
Nearest Town and Distance: Approximately 10 road miles northwest
of Halfway, Oregon.
Estimated Cost: Not Applicable.
Project Sponsor(s): Bonnanza Mining Company
Oversight Agency: Oregon Department of Geology and Mineral
Industries (DOG AMI)
Project Partners: Oregon Department of Fish and Wildlife
Reasons for Action: To profitably recover gold and successfully
reclaim the site while meeting all water quality discharge requirements.
Objectives: To return the entire site to a safe and useable
condition after completion of placer mining.
History of Site: Bonnanza Mining Company began mine development
in 1986 on patented land adjacent to Pine Creek. Approximately 10
of the 45 acres mined by Bonnanza had been mined prior to 1940 and
left unreclaimed. Bonnanza moved approximately 1.3 million yards
of overburden consisting of glacial till, landslide deposits, and
stream gravels and about 335,000 cubic yards of gold bearing gravel.
Early mining efforts had been partially thwarted by huge boulders
scattered through the glacial gravels. Historic surface and drift
mining left considerable reserves in the ground.
The site is located on the floor of a very steep-sided valley vegetated
with mixed conifers. Snow accumulations of over 100Ó per
year are not unusual. Maintaining water quality in Pine Creek and
tributaries that crossed the site presented major hurdles to successful
mining. Due to the heavy snowfall, mining was restricted to summer
and early fall.
Permitting Narrative: The lead permitting agency was DOGAMI
which issued on operating permit for gold mining after approval
of a reclamation plan and acceptance of an appropriate reclamation
bond. Storm water and process water discharges to Pine Creek were
monitored under a National Pollution Discharge Elimination System
(NPDES) permit issued by the Oregon Department of Environmental
Quality (DEQ). The US Army Corps of Engineers and the Oregon Department
of State Lands issued permits for the relocation of Pine Creek.
Mining operations are an allowed use on patented mining claims in
Baker County so a Conditional Use Permit was not required.
Design Narrative: Mining began in the center of this long
but narrow valley floor since that was the location of the previously
mined but not reclaimed area where much of the overburden had already
been removed. The mine plan called for concurrent reclamation. As
mining progressed upstream, the mined-out areas were backfilled
first with the largest rocks and then with progressive smaller material.
Next, sand and silt-laden wash water from the processing plant was
allowed to flow into the backfilled area to fill the voids between
the larger rocks. Using this method, in conjunction with hydrocyclones
to separate silt from the waste stream, a much smaller than normal
system of settling ponds was required.
Even in areas that were not previously mined salvageable topsoil
was insufficient for covering the entire site. Therefore a topsoil
substitute was created from sand and silt from the processing plant
discharge which was mixed with straw and manure. The straw and manure
were obtained from local farmers and ranchers in exchange for truckloads
of washed gravels. A local nursery was hired to establish native
species on the site.
Stream diversions were designed and constructed by Bonnanza in
close cooperation with the Oregon Department of Fish and Wildlife
and the advice of a stream geomorphologist. The post-mining stream
channels are stable and at a gradient equal to or less than that
found prior to the start of the Bonnanza mining.
Upon completion of mining, 41 acres were reclaimed to forestland,
2 acres were wetlands, and 2 acres were stream banks and riparian
lands.
Construction and Post-Mining Narrative: Reclamation began shortly
after mining began, was continuous during mining and continued after
mining was completed. Each area covered with soil material during
the summer was mulched and seeded prior to arrival of the autumn
snow. Large woody debris was placed perpendicular to the slopes
to control runoff and create mirco-habitat for plants and animals.
Over 5,000 mixed conifers were planted. In addition, dogwood, black
cottonwood, chokecherry, wild rose, snowberry, willows and alders
were propagated on-site. Two wetland areas were created by exposing
shallow depressions in the underlying bedrock and allowing water
to pond there.
Construction Photos? Yes
 |
| The
mobile dredge used for gold recovery is in the background while
the foreground shows reclamation in progress |
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| Bonnanza
Mine under reclamation construction |
Services/Contractors Used: Lidstone and Associates from
Ft. Collins Colorado supplied consulting services on stream geomorphology
issues.
Was this project successful?: Yes
How was success determined?: Visual observation suggests
that the timber productivity and wildlife habitat are both greater
than before mining began. The success of the erosion control was
demonstrated by the clarity of water in Pine Creek during periods
of storm water runoff from the site. The success of the ponderosa
pine revegetation is shown in the accompanying photograph of trees
taken about 5 years after planting. Great Blue Herons have been
observed feeding on the abundant tadpoles growing in the wetland
areas.
Post-construction photographs: Yes
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| Deep
Creek after relocation |
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| Ponderosa
Pine on reclaimed ground |
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| Slopes
before reclamation |
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| Slopes
after reclamation |
Supplementary Narrative: The National Association of State
Land Reclamationist issued their annual reclamation award to Bonnanza
Mining for their work on the site. Tom Bonn was president of Bonnanza
Mining and directed the on-site operations; Terry Drever-Gee was
the Environmental Coordinator for Bonnanza. E. Frank Schnitzer was
the responsible reclamationist for DOGAMI throughout most of the
mining and reclamation phases. Bonnanza Mining Company has subsequently
been dissolved.
For more information on this project, contact:
Dawn Marshall
Oregon Department of Geology and Mineral Industries
1536 SE Queen Av.
Albany, OR 97321
Phone: (541) 753-1804
E-mail: dawn.m.marshall@state.or.us
Available Documentation: Numerous inspection reports are in DOGAMI
file 01-0146
Submitted by: Allen Throop,
Consultant
Date: January 2001 |
