2022 BACKGROUND
BUNKER HILL MINING CAP Adrian De Kruyf, Steven Knight, Conner Wootton University of Idaho: Department of Chemical & Biological Engineering
ECONOMICS
DESIGNS CONSIDERED
The Bunker Hill mine
Bacterial Intervention
creates 1,400 gpm of acid
▪ Bacteria consume sulfur, which
mine drainage (AMD).
reduce AMD generation.
▪ Rejected due to bacteria’s need for
Treatment of drainage
additional nutrients.
costs approximately $1
Super Absorbent Polymer
million annually.
▪ Potential to absorb precipitation and
90% of AMD load comes
prevent water entering Guy Cave.
from 40 gpm from Guy
▪ Experiments indicate favorable for
Cave region (pH=2).
Total cost estimated to be $1.4 million for capping of entire Guy Caves Area. Item
Amount
Total Price
Bio Ash Geotextile Geomembrane
3,300 (yd3) 131,000 (ft2) 44,000 (ft2)
$ 66,000 $ 13,100 $ 44,000
Drainage Layer Aggregate
3,300 (yd3)
$
72,600
Drainage Pipe Common Fill Material Topsoil Polymer Seed/Fertilizer/Mulch
1,000 (ft) 2,500 (yd3) 900 (yd3) 10,000 (lbs) 5,000 (yd2) Grand Total Cost (per acre)
$ $ $ $ $
25,000 55,000 45,000 14,000 15,000
revegetation.
ACID MINE DRAINAGE
SOLUTION
Electrochemical Capping
▪ Uses cathodic protection to prevent
AMD is a common pollutant
oxidation.
from mining activities.
The team’s proposed solution is a simple layered cap that includes a bio-ash layer and 0.5 wt% polymer in the topsoil.
▪ Rejected due to scale and need for
AMD is created when sulfur
electricity.
containing minerals contact
the vegetation.
▪ Reacts with water to create
Commonly caused by pyrite
impermeable material.
(FeS2) but can be caused by
A bio-ash layer acts as an
▪ Increases pH of permeate.
other metal sulfides
impermeable reactive layer.
SUPPORTING INFRASTRUCTURE reworking the slope and improvement
from rocks that it encounters
of roads to increase access of the
increasing pollution.
Guy Cave area.
AMD Generation has three reaction mechanisms:
▪ Pyrite oxidation from air ▪ Bacterial oxidation of Iron ▪ Pyrite oxidation of ferric iron
Other layers are typical of a common mine cap.
Implementation of the cap requires
AMD leaches heavy metals
A super absorbent polymer layer holds precipitation for
Bio-Ash Capping
oxygen and water.
$ 349,700
Cost to level the area is estimated to be $255,000. Cost for road improvement is estimated to be $95,675.
ACKNOWLEDGEMENTS Special thanks to Dr. Nielsen, Scott Smith, Dr. Langman, Dr. Bernards, Charles Cornwall, and our sponsors at Bunker Hill Mining Corp.