Inifed States
hvirermental Protection
Historic Hardroclg Mining
The West's Toxic Legacy
The Critical Link between Water Quality and Abandons
Mine Sites
"Drainage from hardrock
major water
quality prbMem in our state.
This is true fir mam Western
states. We need Uk-stay focused
on dijiiuf) of .flMMW of
scirrc water amtammtion—
fin rr\lot0oti 4>f our natural
systems, and maintenance of
our environment."
«*0«H«rwT
senior Surface W^rr Analy*
Idaho Division at tovirimmattK^aliry
-------
The Trouble with
Historic Mine Sites
Investigate,
Investigate:
The Importance of
Detective Work
Far L»tt: Gathering dati on water from a mine pond.
Top Right: Collecting ground muter from a until for
sampling purposes. SoftomR&M; Water quality analysis
can sometimes be performed on site, from the back of a
truck equipped wtth laboratory equipment
This metata
deposit on the
wall ofa mine
shaft is nearly
pureztne.
"If we don't understand what is
going on and how the water moves
through the earth, well end up
spending a lot more money and
getting a lot less done."
BniceStem
Senior Geologist and Project Director
Division of Minerals and Geofogy
Colorado Department of Natural Resources
Historic hardrock mining activities in the West
have created hundreds of thousands of geological
disturbances. Drainage and runoff from mine
sites impact water quality in streams throughout
the Rocky Mountain states. While cleanup of
mine site is a high priority, the sheer number
and geographic distribution of these disturbed
areas make addressing them a formidable task.
Traditional metals mining usually involves
digging tunnels and adits to teach lodes of
mineral-rich ore. Rock Is removed from
deep within the earth, and milled to
extract desired minerals. When the ore is
exhausted, miners move on leaving behind
finely-ground tailings and waste rock above
ground, and tunnels underground.
Such mining activities expose part of the
earth's crust to water, oxygen, and bacteria.
Layers of metals-rich rock that have been
underground become oxidized and chemically
altered. When water flows through and over
the newly-disturbed material, metals that were
once locked within rock can dissolve in the
water. Zinc, iron, cadmium, copper, lead-
metals that are toxic to aquatic life and can
damage human health—end up contaminating
surface waters and ground water.
The activities that created the mine workings,
residual wastes, and other impacts to the envi-
ronment at inactive and abandoned mine sites
are generally poorly documented. Consequently,
little or no useful information Is available as
the reclamation specialist steps onto the site to
determine specific water quality impacts, their
origins, and remediation strategies.
Top.The eerie effects of windblown tailings near the former Mary Murphy
Mine and Mil! In Colorado. Bottom Left; Tailings and the remains of
historic mint workings exhibit the characteristic reddish-brown cofor of
iron oxide leaching. Bottom Right Blocked by mine waste dumped in the
stream channel, the flow In French Creek was reduced to ponding near
the former Wellington-Oro Mine near Breckenridge, Colorado.
Since every mine site is unique, using "off-the-
shelf" characterization strategies can lead to an
improper or Incomplete understanding. Remedial
actions based on a partial picture of a site may
overlook important contaminant sources or
pathways, resulting in no improvement to
water quality. With limited financial resources
available to address mine sites, failure of remedi-
ation will only be tolerated to a limited extent.
Adequate resources and time must be dedicated
to extensive site characterization before remedial
activities are proposed and undertaken. Charac-
terization includes five steps; 1) reconstructing
pre-mining conditions, 2) inventorying what
has been deposited above ground, 3) mapping
what has occurred underground, 4) monitoring
the movement of water, and S) estimating the
Impacts of mining disturbances.
-------
I
these two sites have been extremely valuable lab-
oratories for agendes and reclamation specialists
involved in characterization and remediation
efforts. Ongoing work will help to better under-
stand and solve the impacts to water quality at
the sites.
Chalk Creek and
French Gulch:
Two Colorado Test Sites
Fm Right: Water draining from a mine tunnel in the Chalk
Crack area runs bright rad with dissolved ratal*.
Top Lift: Just upstream from a fish hatchery intake gate,
the stream bottom reveals the tail-tale whitish-gray coloring
of tailings. Bottom Left; A moonscape caused by mine
tailings contrasts starkly with the natural dpirst vegetation.
Chalk Creek and French Gulch are typical of
the many inactive and abandoned mining and
ore processing sites in the Rocky Mountain West.
Neither site has produced the catastrophic
environmental damage that might place it on the
Superfund priority list. Yet from the perspective
of the Colorado Department of Public Health
and Environment, these two sites—like hundreds
of others across the state—pose definite threats.
As such, these sites were recognized as possible
test cases for using experimental characterization
techniques at mine sites.
To tackle the task of characterization at these
two sites, specialists from several complementary
disciplines came together to combine
their expertise. The teams approached
Chalk Creek and French Gulch with
few preconceptions about the
geologic, hydrologic, and physical
systems operating at each site.
Water quality improvement goals
at Chalk Creek and French Gulch
have not yet been achieved. Yet
Cross Section
through French Gulch
at Wellington-Oro Mine,
High Flow Conditions
Potential Sources of
Heavy Metals Contamination
Q Mill tailings in alluvium,
saturated by French Creek
© Precipitation leaches metals
from mine and mill waste to
water table
© Mine pool from Wellington-
Oro complex drains to
French Creek alluvium
KEY
[ J Alluvium
I Porphyry Bedrock
H Shale Bedrock
Waste Rock
MNH Roaster Fines
H Dredge Tails
Flooded Workings
Precipitation
Direction of Seepage
-------
Lessons Learned
from Chalk Creek
and French Gulch
The Road Map:
Steps for Understanding
Effective Site
Characterization
and Cleanup
for use in mine site characterization
feels like conducting an autopiy
with a butter knife. We need more
sophisticated, more reliable tools.
Experience together with better tools
Is the winning combination."
CmlRisdl
Environmental Scientist
Environmental Protection Agany, Segtos 8
Into the Future
COLORADO
DEPARTMEhfT OF
NATURAL
RESOURCES
Produced by the U.£ Environmental
Protection Agency, Regan 8, with
the Cotoodo Department of Natural
Jtesou
------- |