Assessing the Influence of Copper-NickelBearing Bedrocks on Baseline Water Quality in
Three Northeastern Minnesota Watersheds
Perry M. Jones
Laurel G. Woodruff
Robert R. Seal
Nadine Piatak
Steven A. Hauck
U.S. Department of the Interior
U.S. Geological Survey
Carrie Jennings
USGS MN Activities Related to Potential Mining
2011 - St. Louis River - streambed sediment sampling/
streamflow gaging – GLIFWC/Fond du Lac/EPA
In 3 watersheds (Filson, Keeley, St. Louis)
2012 - water quality/streambed sediment sampling – USGS
2013-16 - bedrock and soil sampling with additional waterquality sampling/streamflow gaging - LCCMR
2015-16 - additional water-quality analyses (i.e stable
isotopes) - GLRI/EPA
Why these 3 watersheds?
Filson Creek
Ni-Cu-PGE mineralization
Keeley Creek
little/no mineralization
St. Louis River
Fe-Ti-oxide mineralization
USGS – 2013-2016 LCCMR Study
Assessment of Duluth Complex Bedrocks on Water Quality
1) Characterize metal concentrations in
• surface waters
• bedrock
• stream-bed sediments
• soil
across the basal part of the Duluth Complex
2) Determine if metal concentrations are currently
influencing regional water quality
Outcomes
Establish the current regional pre-mining baseline
geochemistry of soils, sediments, rocks and waters.
Create datasets/tools to assess potential impacts of
proposed mining on water quality.
Used by Federal, State, local, tribal entities, and mining
companies as a context for sound public policy decisions.
Study Design
Activity 1: Determine major and trace element contents in
bedrock samples, soil samples, and stream-bed
sediment samples.
Activity 2: Determine temporal flow rates and background
metal and major constituent loads.
Activity 3: Construction of conceptual hydrologic and
water-quality models to assess hydrologic and
water-quality conditions prior to potential mining
2014 – 2015 Sampling Plan
WATER QUALITY – all 3 watersheds
 21 total sites sampled 4 times/year
 18 trace elements
 12 major constituents (ions)
 DOC (total and quality)/TOC
 stable isotopes (O, H)
SOLID MEDIA SAMPLING – in each watershed
 10 bedrock samples
 >30 soil samples (up to 3/site)
 20 stream bed sediments ( 2 size fractions: < 2 mm;
<63 microns)
 44 major and trace elements (near-total digestion)
 10 metals by weak leach (stream bed sediments)
Filson and Keeley Creeks
•
•
•
•
abundant wetlands
several lakes
thin glacial cover (< 50 feet)
topography bedrock-controlled
FILSON
KEELEY
FILSON
Filson/Keeley sample sites
VIRGINIA FORMATION OUTCROP
St. Louis River
•
•
•
•
abundant wetlands
minimal bedrock exposure
thick glacial cover (100 – 150 feet)
topography controlled by glacial
features
GABBRO BOULDERS
St. Louis sample sites
Preliminary Water Quality Assessment, 2012-2014
Comparison of median and range dissolved concentrations
1) temporal changes in all samples relative to flow
2) watersheds
Different Laboratories
USGS Research Laboratory - September 2012, June 2013
USGS National Water-Quality Laboratory - September 2013,
April, June, August, and Sept/Oct 2014
Water Quality Assessment – pH and Specific Conductance
Dilute waters in each watershed
Lower pH values may be associated with mineralization and
contributing waters from wetlands/bogs
Watersheds
Specific Conductance
(µS/cm)
pH
Filson Creek
23 – 51
5.0 – 7.2
Keeley Creek
25 – 105
5.6 – 6.8
St. Louis River
37 – 98
6.4 – 8.3
Conceptual Hydrologic/Water-quality Modeling
Hydrology
Water balances for 3 watersheds
Synthetic hydrographs
Water-quality modeling
Visual MINETEQ – equilibrium model
USGS OTIS – transport model
Tracer test – Filson Creek
What are the important parameters controlling metal
transport at various concentrations?
Do you know what this white stuff is?