EPA/600/R-05/060
July 2005
Prevention of Acid Mine Drainage
Generation from Open-pit
Highwalls—Final Report
Mine Waste Technology Program
Activity III, Project 26
by:
A. Lynn McCloskey
MSB Technology Applications, Inc.
Mike Mansfield Advanced Technology Center
Butte, Montana 59702
Contract No. DE-AC09-96EW96405
Through EPA IAG No. DW89938870-01-1
Diana Bless, Project Officer
U.S. Environmental Protection Agency
Office of Research and Development
National Risk Management Research Laboratory
Cincinnati, Ohio 45268
and
U.S. Department of Energy
Savannah River Operations Office
Aiken, South Carolina 29802
National Risk Management Research Laboratory
Office of Research and Development
U.S. Environmental Protection Agency
Cincinnati, Ohio 45268
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Disclaimer
The information in this document has been funded wholly or in part by the U.S. Environmental Protec-
tion Agency (EPA) under an Interagency Agreement (IAG) between EPA and the U.S. Department of Energy,
IAG No. DW89-938870-01-0, with implementation provided by MSB Technology Applications, Inc. Men-
tion of trade names or commercial products does not constitute endorsement or recommendation for use by
either of these agencies.
11
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Notice
The U.S. Environmental Protection Agency through its Office of Research and Development funded
the research described here under IAG DW89938870-01-0 through the U.S. Department of Energy (DOE)
Contract DE-AC09-96EW96405. It has been subjected to the Agency's peer and administrative review and
has been cleared for publication as an EPA document. Reference herein to any specific commercial product,
process, or service by trade name, trademark, manufacturer, or otherwise, does not necessarily constitute
or imply its endorsement or recommendation. The views and opinions of authors expressed herein do not
necessarily state or reflect those of the EPA or DOE, or any agency thereof.
ill
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Foreword
The U.S. Environmental Protection Agency is charged by Congress with protecting the Nation's land,
air, and water resources. Under a mandate of national environmental laws, the Agency strives to formulate
and implement actions leading to a compatible balance between human activities and the ability of natural
systems to support and nurture life. To meet this mandate, EPA's research program is providing data and
technical support for solving environmental problems today and building a science knowledge base necessary
to manage our ecological resources wisely, understand how pollutants affect our health, and prevent or reduce
environmental risks in the future.
The National Risk Management Research Laboratory is the Agency's center for investigation of tech-
nological and management approaches for preventing and reducing risks from pollution that threaten human
health and the environment. The focus of the Laboratory's research program is on methods and their cost
effectiveness for prevention and control of pollution to air, land, water, and subsurface resources; protection
of water quality in public water systems; remediation of contaminated sites, sediments, and groundwater;
prevention and control of indoor air pollution; and restoration of ecosystems. The NRMRL collaborates with
both public and private-sector partners to foster technologies that reduce the cost of compliance and to antici-
pate emerging problems. NRMRL's research provides solutions to environmental problems by developing
and promoting technologies that protect and improve the environment; advancing scientific and engineering
information to support regulatory and policy decisions; and providing the technical support and information
transfer to ensure implementation of environmental regulations and strategies at the national, state, and com-
munity levels.
This publication has been produced as part of the Laboratory's strategic long-term research plan. It is
published and made available by EPA's Office of Research and Development to assist the user community
and to link researchers with their clients.
Sally Gutierrez, Ph.D., Acting Director
National Risk Management Research Laboratory
IV
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Contents
Disclaimer ii
Notice iii
Foreword iv
Acronyms and Abbreviations ix
Abstract xi
Acknowledgments xii
Executive Summary ES-1
1. Introduction 1
1.1 Purpose and Project Description 1
1.2 Project Schedule 2
1.3 Criteria for Success 2
2. Site Characterization and Pretreatment Activities 3
2.1 Demonstration Site Description 3
2.2 GSM Historical Data 4
2.2.1 Geology 4
2.2.2 Tectonic Activity 4
2.3 Pretreatment Core Drilling and Water Injection Testing 6
2.3.1 Water Injection Testing 6
3. Technology Identification Activities 7
3.1 Technology Descriptions 7
3.1.1 EARS 7
3.1.2 EcoBond 8
3.1.3 UNR/MgO Technology 8
3.1.4 UNR/KP Technology 8
3.2 Highwall Technology Evaluation Methods 9
3.2.1 Residual Wash Field Sampling 9
3.2.2 Laboratory Testing - HC Testing 9
4. Field Demonstration 11
4.1 Technology Application Descriptions 11
4.1.1 EARS 11
4.1.2 EcoBond 11
4.1.3 UNR/MgO Technology 12
4.1.4 UNR/KP Technology 12
5. Site and Technology Characterization Results 15
5.1 Core Drilling and Water Injection Testing Results 15
5.1.1 Pretreatment Core Drilling Results 15
5.1.2 Water Injection Testing Results 15
5.2 Mine Wall/Rinsate Sampling Results 16
5.2.1 Summary of Statistical Analysis 17
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Contents (cont'd)
5.2.2 Residual Wash pH Results 17
5.2.3 Residual Wash Metals Analysis 17
5.2.3.1 EARS Plot 20
5.2.3.2 EcoBond 20
5.2.3.3 UNR/MgO 20
5.2.3.4 UNR/KP 23
5.2.4 Percent Reduction of Total Metals Comparison 23
5.3 HC Testing Results 24
5.3.1 ICP Metals Analysis Results for Feed Solids 25
5.3.2 GSM Untreated Rock 25
5.3.3 EARS 25
5.3.4 EcoBond 26
5.3.5 UNR/MgO 36
5.3.6 UNR/KP 36
5.3.7 Summary of the HC Testing Results 36
5.4 Technology Cost Analysis 43
6. Quality Assurance/Quality Control 46
6.1 Project Background 46
6.2 Project Reviews 46
6.2.1 Internal Field Systems Review at the Demonstration Site 46
6.2.2 External Technical Systems Audit 47
6.2.2.1 Summary TSA Procedures, Findings, and Resultant Actions 47
6.3 Data Validation 48
6.4 Program Evaluation 48
6.5 HC Data Evaluation 48
6.6 Recommendations and Conclusions 49
7. Conclusions 51
8. References 53
9. Bibliography 54
Appendix A: Core Logs A-l
Appendix B: Water Injection Results B-l
Appendix C: Residual Wash Field Sampling C-l
Appendix D: Statistical Data Analysis of Residual Wash Field Sampling Data D-l
Appendix E: McClelland Laboratory, Inc., Laboratory Testing Services to Determine the
Effects of Accelerated Weathering of Solid Materials Using a Modified Humidity
Cell E-l
Note: Appendices A through E are available upon request from the MSE MWTP Program Manager. Please
refer to document number MWTP-252. E-mail: mse-ta@mse-ta.com, Phone (406) 494-7100.
VI
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Figures
2-1. GSM location map 3
2-2. GSM open-pit and Activity III, Project 26 site 4
2-3. Landscape 5
2-4. Surncial geology in the area of GSM 6
4-1. PARS being spray applied on the GSM open-pit highwall at Plot B 12
4-2. Spray application of the EcoBond technology onto the GSM highwall at Plot C 13
4-3. Field application of the UNR/MgO technology on the GSM highwall at Plot D 13
4-4. Spray application of theUNR/KP technology on the GSM at Plot E 14
5-1. Average pH from highwall at GSM 18
5-2. pH results for July 22, 2002, residual wash sampling event 18
5-3. pH results for September 19, 2002, residual wash sampling event 19
5-4. pH results for November 9, 2002, residual was sampling event 19
5-5. Total metals loading results for Al from samples taken from the mine wall sampling stations 20
5-6. Total metals loading results for Cu from samples taken from the mine wall sampling stations 21
5-7. Total metals loading results for Mn from samples taken from the mine wall sampling stations 21
5-8. Total metals loading results for Fe from samples taken from the mine wall sampling stations 22
5-9. Total metals loading results for Ni from samples taken from the mine wall sampling stations 22
5-10. Total metals loading results for Zn from samples taken from the mine wall sampling stations 23
5-11. Spray application of the material sent to MLI for HC testing 25
5-12. Weekly and cumulative HC analytical results for sample 1 from GSM background plot (Plot A).... 27
5-13. Weekly and cumulative HC analytical results for sample 2 from GSM background plot (Plot A).... 28
5-14. Weekly and cumulative HC analytical results for sample 3 from GSM background plot (Plot A).... 29
5-15. Weekly and cumulative HC analytical results for sample 1 from EARS plot (Plot B) 30
5-16. Weekly and cumulative HC analytical results for sample 2 from EARS plot (Plot B) 31
5-17. Weekly and cumulative HC analytical results for sample 3 from EARS plot (Plot B) 32
5-18. Weekly and cumulative HC analytical results for sample 1 from EcoBond plot (Plot C) 33
5-19. Weekly and cumulative HC analytical results for sample 2 from EcoBond plot (Plot C) 34
5-20. Weekly and cumulative HC analytical results for sample 3 from EcoBond plot (Plot C) 35
5-21. Weekly and cumulative HC analytical results for sample 1 from UNR/MgO plot (Plot D) 37
5-22. Weekly and cumulative HC analytical results for sample 2 from UNR/MgO plot (Plot D) 38
5-23. Weekly and cumulative HC analytical results for sample 3 from UNR/MgO plot (Plot D) 39
5-24. Weekly and cumulative HC analytical results for sample 1 from UNR/KP plot (Plot E) 40
5-25. Weekly and cumulative HC analytical results for sample 2 from UNR/KP plot (Plot E) 41
5-26. Weekly and cumulative HC analytical results for sample 3 from UNR/KP plot (Plot E) 42
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Tables
2-1. GSM High wall Monitoring Well Data Analytical Parameter Analytical Result (mg/L
Unless Otherwise Indicated) 5
5-1. Summary of the variability of the mean and the sample size both before and after the
application of the technologies on the test plots 16
5-2. Summary of Water Injection Testing 24
5-3. Percent Reduction of Total Metals from the Treated Technology Plots Compared to the
Untreated Plot (Plot A) 24
5-4. ICP Metals Analysis Results on Treated and Untreated Feed Samples for HC Testing 26
5-5. Summary HC Test Data for Untreated and Treated GSM Highwall Samples (data are an
average of respective triplicate HC tests) 43
5-6. Current National Drinking Water MCLs and SMCLs vs. HC Test Extract Composite Data
(mg/L) Untreated and Treated GSM Highwall Samples for Regulated Metals Analyzed 44
5-7. Cost Breakdown for Demonstrated Technologies 45
5-8. Core Cost Elements 45
6-1. Data Quality Indicator Objectives 48
6-2. Summary of QC Checks for Critical Total Metals Analysis 49
6-3. Summary of Flagged Data for Activity III, Project 26 50
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Acronyms and Abbreviations
AGP acid generating potential
Al aluminum
AMD acid mine drainage
ANP acid neutralizing potential
As arsenic
ASTM American Society for Testing and Materials
bgs below ground surface
Cd cadmium
cm/s centimeter per second
cp centipoise
Cu copper
DOE U.S. Department of Energy
EcoBond EcoBond™ ARD
EC electric conductivity
EH oxidation-reduction potential
EPA U.S. Environmental Protection Agency
PARS furfuryl alcohol resin sealant
Fe iron
Fe+2 ferrous iron
Fe+3 ferric iron
ft foot
gal gallon
gpm gallons per minute
GSM Golden Sunlight Mines, Inc.
HC humidity cell
IAG Interagency Agreement
ICP inductively coupled plasma spectrometer
ID inner diameter
K hydraulic conductivity
kg kilogram
KP potassium permanganate
m meter
MCL maximum contaminant level
MEND Mine Environment Neutral Drainage (Canadian)
mg/L milligram per liter
MgO magnesium oxide
mL milliliter
MLI McClelland Laboratories, Inc.
Mn manganese
MSB MSB Technology Applications, Inc.
MT2 Metals Treatment Technologies, LLC
mV millivolt
MWTP Mine Waste Technology Program
Ni nickel
IX
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Acronyms and Abbreviations (Cont'd)
NNP net neutralization potential
P phosphorus
Pb lead
ppm parts per million
QA quality assurance
QAPP quality assurance project plan
QC quality control
RPD relative percent difference
SO4 sulfate
SU standard unit
TSA technical systems audit
UNR University of Nevada-Reno
UNR/KP potassium permanganate technology developed and patented by DuPont Technology, field
applications developed and applied by UNR, the current patent holder
UNR/MgO magnesium oxide passivation technology developed by UNR
Zn zinc
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Abstract
This document summarizes the results of Mine Waste Technology Program Activity III, Project 26, Pre-
vention of Acid Mine Drainage Generation from Open-Pit Highwalls. The intent of this project was to obtain
performance data on the ability of four technologies to prevent the generation of acid mine drainage (AMD)
from an open-pit highwall. The four technologies applied included Ecobond™ ARD developed by Metals
Treatment Technologies, LLC of Denver, Colorado; a magnesium oxide passivation technology developed
by the University of Nevada-Reno (UNR); a potassium permanganate technology developed and patented
by DuPont Technology and applied by UNR (the current patent holder); and a furfuryl alcohol resin sealant
developed by Intermountain Polymers of Idaho Falls, Idaho.
The demonstration was conducted at the Golden Sunlight Mine, an active open-pit gold mine. The four
technology providers spray applied their technologies to a designated 50-foot-high by 50-foot-wide area on
the highwall. The primary objective of this demonstration was to determine the impact of the treatments
on the designated plot areas compared to an untreated area of the highwall. Also, during application of the
technologies, each technology provider was required to apply the technology to a specially prepared sample
that underwent humidity cell (HC) testing.
Each technology inhibited AMD differently, dependent on chemistry of the treatment formulation, sul-
fide content, morphology, pH of the waste material, weather conditions, and the amount of water draining
from the highwall. Overall, each of the technologies applied to the highwall decreased the generation of
acid and the mobility of metals from the highwall. However, the results from the highwall residual wash
sampling indicate that in the field the technologies perform differently in comparison to samples analyzed in
a controlled laboratory environment such as the HC.
XI
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Acknowledgments
This document was prepared by MSB Technology Applications, Inc. (MSB) for the U.S. Environmental
Protection Agency's (EPA) Mine Waste Technology Program (MWTP) and the U.S. Department of Energy's
(DOE) National Energy Technology Laboratory. Ms. Diana Bless is EPA's MWTP Project Officer, while Mr.
Gene Ashby is DOE's Technical Program Officer. Ms. Helen Joyce is MSB's MWTP Program Manager.
xil
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Executive Summary
The primary objective of the Mine Waste Technology Program (MWTP) is to advance the understanding of engineering solu-
tions to national environmental issues resulting from the past practices in mining and smelting of metallic ores. The MWTP is
funded by the U.S. Environmental Protection Agency (EPA) and is jointly administered by EPA and the U.S. Department of Energy.
This final report is for MWTP, Activity III, Project 26, Prevention of Acid Mine Drainage Generation from Open-Pit Highwalls.
This demonstration focused on the identification and development of open-pit highwall technologies that provide engineering
solutions for future applications. The intent of the demonstration project was to obtain performance data on the ability of four
technologies to prevent the generation of acid mine drainage (AMD) from an open-pit highwall. The four technologies applied
included:
• EcoBond™ ARD (EcoBond) developed by Metals Treatment Technologies, LLC (MT2) of Denver, Colorado;
• a magnesium passivation technology (UNR/MgO) developed by the University of Nevada-Reno;
• a potassium permanganate technology (UNR/KP) developed and patented by DuPont Technology with field applications
developed and applied by UNR (the current patent holder); and
• a furfuryl alcohol resin sealant (EARS) developed by Intermountain Polymers of Idaho Falls, Idaho.
The demonstration was conducted at Golden Sunlight Mines, Inc. (GSM) an active open-pit gold mine located near Whitehall,
Montana. The four technology providers spray applied their technologies, which were in a liquid form, to a designated 50-foot-high
by 50-foot-wide area on the highwall. Each of the technologies created an inert layer or coating on the sulfide material, preventing
contact with the atmospheric oxygen/water during the weathering of the sulfide highwall rock and thus preventing sulfuric acid
generation and metals mobilization. A background/control plot of the same size was designated and used to evaluate and compare
to the four treatment technologies.
The primary objective of this demonstration was to determine the impact of the treatments on the designated plot areas com-
pared to the untreated area of the highwall. To achieve this objective, the highwall at the project site was geologically, hydraulically,
and geochemically characterized prior to technology application.
To evaluate and determine if the objectives had been achieved, two test procedures were used: one test method was humidity
cell (HC) testing in the laboratory, and the other procedure was a field mine wall sampling method. NOTE: These two procedures
should not be compared because the data were gathered under distinctively different conditions.
Data from the untreated GSM highwall, for both field monitoring and HC laboratory testing, showed that untreated material
would produce acid in a natural weathering and oxidizing environment. The same background data from the untreated GSM plot
were used for comparison of all the treatment technologies to determine if the technologies were effective in reducing the potential
for AMD.
Humidity Cell Tests
Humidity cell testing is routinely used by the mining industry to predict if rock material has the potential to produce acid and
mobilize metals when exposed to natural weathering. For this demonstration, HC testing was used to provide similar information.
During application of the technologies, each technology provider was required to apply the technology to a specially prepared
sample that was sent to McClelland Laboratories, Inc., (MLI) in Sparks, Nevada, where American Society of Testing Materials
(ASTM) D5744-96 for Accelerated Weathering of Solid Materials using a Modified Humidity Cell (HC) testing method was con-
ES-1
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ducted. For the HC testing, the technology was allowed to contact the full surface area of the sample being treated for an extended
period of time, allowing for the most ideal application conditions. The HC testing results, as with mining applications, allow and
were used to predict whether the untreated and treated samples would produce acid and mobilize metals.
Results from 41 weeks of HC testing indicated and predicted that all technologies were effective in preventing acid production
and the mobility of metals. Each technology was compared with the background sample results. After 21 weeks of testing, testing
was halted, and the samples were allowed to rest for approximately 3 weeks.
When compared to the background plot for EcoBond technology, the pH was neutral; the electric conductivity (EC) was typical
for systems exposed to air and indicated minimal metal mobility; iron (Fe), sulfate (SO4), and acidity production was higher; and
calculated ratios were substantially greater than regulatory guidelines. For the two UNR technologies, the pH was slightly greater
than 6; the EC was typical for systems exposed to air and indicated minimal metal mobility; Fe, SO4, and acidity production was
higher; and calculated ratios were substantially greater than regulatory guidelines. Essentially, no metals were mobilized from
EcoBond, UNR/MgO, and UNR/KP cells. The lack of metals mobility indicates that three treatment technologies prevented acid
production.
For the EARS technology, the pH ranged between 4 and 5, the EC was typical of systems exposed to air and indicated some
metals mobility for Fe and SO4. The EARS treated sample did prevent AMD but not as well as the other three technologies. Because
the EARS technology has binding/stabilizing capabilities, the EARS HC sample had to be broken apart to allow it to fit into the HC
test cells, which exposed rock surfaces that otherwise would have been covered.
Residual Wash Sampling Tests
After the technologies were applied to the GSM highwall, a mine wall/residual wash water sampling test method that was
developed for the Canadian Mine Environment Neutral Drainage Program was implemented where the total metals loading per unit
area and the pH of the highwall in the field were calculated and measured, respectively. This method allowed the technologies to be
evaluated under field conditions and field designed application rates, which can be less than ideal. An example of nonideal condi-
tions would include the loss of several mine wall sampling ports when mine wall movement caused the highwall to become unstable.
The loss of the sampling ports has the potential to affect the overall results, leaving for the final sampling event only one UNR/MgO
and three Ecobond sampling ports. Due to the instability of most highwalls and for future research on open-pit highwalls, it is
recommended that a surplus of sample ports be applied in the event some ports are damaged.
Field results for the mine wall sampling show that for the EcoBond, UNR/MgO, and UNR/KP plots, the pH was as low as the
pH of the background plot. This means that the pH was less than 4 and the range of average percent metals reduction was between
-211% and 82% (see Table ES-1). The EARS recorded pH was steady at pH 4 to 4.5, extending for the full demonstration, and the
percent metals reduction ranged between 75% to 91%, compared to the background results. A large negative number for the percent
metals reduction indicates high metals mobility, and a high positive number indicates a low mobility.
Table ES-1. Percent reduction of total metals from the treated technology plots compared to the untreated plot (Plot A)
Treated Plot vs. Background
% Reduction of Al
%Reduction of Cu
% Reduction of Fe
% Reduction of Mn
% Reduction of Ni
%ReductioofZn
PARS
75
85
85
84
90
91
EcoBond
20
-211
24
49
48
-40
UNR/MgO
38
26
-16
82
50
75
UNR/KP
62
76
30
51
72
76
In the field, physical stabilization of the highwall was only observed on the PARS technology plot. The other three technologies
provided chemical passivation of the wall but not physical stabilization.
Test results, from both the field and the HC tests, indicate that all of the treatment technologies (to some degree) controlled the
acid generation potential of a mine highwall. The results from the highwall residual wash sampling indicate that in the field the
technologies did not perform as well as the samples analyzed in the laboratory (HC testing) in a controlled environment. If these
technologies were to be applied at another site, a small-scale field application should be performed to evaluate the full effectiveness
of the technology before investing in a full-scale technology application.
Upon completion of the demonstration, several question remain unanswered.
ES-2
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• What is the effect of the airborne particulate and runoff on the field results?
• What was the effect of allowing all HC samples that were saturated during the application to sit until testing was initiated
and what was the effect on the samples that were allowed to sit during the time that HC testing was suspended?
• Was the PARS technology performance altered when the sample for HC testing had to be broken into smaller particles to
fit into the HC, thus exposing untreated surfaces to the induced weathering processes?
These questions still exist. However, overall, the technologies reduced the potential for acid production on the GSM highwall
material, whether in the field or in the laboratory.
Each technology inhibits AMD differently, dependent upon chemistry of the treatment formulation, sulfide content, morphol-
ogy, pH of waste material, weather conditions, and the amount of water draining from the highwall. By reducing the potential for
AMD generation from a mine highwall, reclamation costs for mining companies and regulatory agencies could be minimized.
Overall, each of the four technologies applied to the highwall decreased the generation of acid and the mobility of metals from
the highwall. After evaluating the HC testing results using GSM highwall material, it was predicted that materials treated with the
technologies were not acid forming; however, additional testing would need to be performed for the PARS technology to determine
if breaking the sample and exposing fresh rock surfaces caused metals values to be greater than the other technology results. Upon
evaluation of the mine wall sampling results from the GSM highwall test plots, it was predicted that the average percent reduction
of metal from the highwall was reduced. However, Pcobond would require additional testing if the highwall contained increased
amounts of copper and zinc, as would the UNR/MgO technology for rock bearing a high iron content. Since these are fairly new
technologies, a small-scale field application should be considered on future mine highwalls to observe the performance of the
technologies on different highwall material. This would assist with designing a full-scale application of the selected technology.
ES-3
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1. Introduction
Acid mine drainage (AMD) is a significant and costly
environmental concern in the mining industry. This is the fi-
nal report for the Mine Waste Technology Program (MWTP),
Activity III, Project 26, Prevention of Acid Mine Drainage
Generation from Open-Pit Mine Highwalls. The project was
funded by the U.S. Environmental Protection Agency (EPA)
and jointly administered by EPA and the U.S. Department
of Energy (DOE) through an Interagency Agreement (IAG).
EPA, through the DOE, contracted MSB Technology Applica-
tions, Inc. (MSE) to implement the MWTP. The purpose of
this project was to evaluate the ability of four technologies to
reduce acid formation and the mobility of metals from an open-
pit highwall. Golden Sunlight Mines, Inc. (GSM), a wholly
owned subsidiary of Placer Dome America, was selected as the
technology demonstration site.
1.1 Purpose and Project Description
Waste rock dumps have been categorized as a main source
of AMD, although open-pit highwalls, underground workings,
ore stockpiles, and concentrate storage and loadout areas can
contribute significantly, generating volumes of AMD. Exten-
sive research has been conducted to understand and reduce the
AMD produced as a result of mining activity. This research
has focused predominately on using physical, chemical, and
passive treatment options to reduce AMD from surface waste
piles, mine discharging adits, and tailings piles. However, only
a minimal amount of information was available on chemically
or physically passivating an open-pit highwall to reduce the
production of AMD. This is partially due to the difficulty and
danger involved when working on or near the face of a highwall.
The overall objective of this project was to research current and
innovative technologies capable of reducing and/or eliminating
the generation of AMD (i.e., acid generation and mobility of
metals) from an open-pit highwall and then apply and test the
potential technologies under actual field conditions.
Four passivation technologies were selected and spray ap-
plied on the highwall. The technologies either physically or
chemically treated the coated highwall depending on the treat-
ment formulation used.
The major activities of the project were:
- site characterization;
- technology identification;
- technology implementation;
- quality assurance (QA);
- materials testing; and
- long-term monitoring and evaluation.
This final report will address the activities listed above. All
pertinent information pertaining to the project will be addressed
in this document to evaluate the critical measurement and effec-
tiveness of each technology. Each technology was compared to
an untreated plot on the open-pit highwall.
This report addresses the project activities as indicated
below.
• The description and background information, scope
of work, description of the demonstration site, project
organization, project schedule, and determined criteria
for success are presented in Section 1.
• The preapplication site characterization, including all
of the geology, hydrogeology, GSM historic informa-
tion, physical rock properties, water quality, and geo-
chemistry, is presented in Section 2.
• The general description of the identified technologies
and a list of the reasons the technology was selected
are presented in Section 3, along with the descriptions
of the project site and plot preparation and a brief de-
scription of the field sampling and laboratory methods
used to evaluate the technologies.
• The general application of the technology, including
the application materials and methods, equipment,
procedures, and design of the application system, as
well as the verification and monitoring events per-
formed during technology application is presented in
Section 4.
• Review and interpretation of the results from the sam-
pling activities, including evaluation of all results from
the field and laboratory monitoring (i.e., residual wash
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and humidity cell (HC) analysis, respectively) is pre-
sented in Section 5.
• A summary of the QA activities used to determine the
usability of the data generated is provided in Section
6.
• The conclusions derived from the field program, previ-
ous work performed, and recommendations for future
projects are presented in Section 7.
• A list of references is presented in Section 8.
1.2 Project Schedule
This project was highly ranked among several potential
projects presented to the EPA regional offices and to the MWTP
Technical Integration Committee in April 2000. Once the proj-
ect was selected, the project work plan (Ref. 1) was completed
in November 2000, and characterization of the project site was
performed in June 2001. Site characterization, which was per-
formed in June 2001, included core drilling into the high wall
and water injection testing.
The technologies were implemented independently at
scheduled intervals on the highwall between October and De-
cember 2001. Residual wash sampling was performed on the
highwall from April 2001 to November 2002 (Ref. 2). Humid-
ity cell testing was performed for 41 weeks and was finished
in July 2003 with project site closeout in December 2002. In
September 2003, the test panels were mined by GSM during
expansion of the open pit.
Regarding the technology application schedule, the fur-
furyl alcohol resin sealant (PARS) technology and the Metals
Treatment Technologies, LLC (MT2) technology (EcoBond)
were applied in October 2001, the University of Nevada-Reno
(UNR) magnesium oxide (MgO) technology was applied in
November 2001, and the UNR potassium permanganate (KP)
technology was applied in December 2001.
1.3 Criteria for Success
The primary objective of the field demonstration was to
evaluate the technologies applied to the highwall at GSM for
their ability to decrease or eliminate acid generation and mobil-
ity of metals from the treated areas. More specifically, Project
26 objectives included:
- determining any impact on the pH of the treated high-
wall areas compared to the pH of the samples from the
untreated areas; and
- determining the impact of the treatments on the total
metal loading per unit area in the rinsates compared
to the total metals loading in the rinsates from the un-
treated area for aluminum (Al), copper (Cu), iron (Fe),
manganese (Mn), nickel (Ni), and zinc (Zn).
Achievement of the objective was to be determined by
comparing the data from treated areas with data collected from
the untreated control/background area. Data from the residual
wash highwall testing and the HC testing were also analyzed
to compare measurements collected from the same location at
different times. The analysis was performed to provide further
indication of the spatial and temporal variability of parameters
within the treated areas.
Each mine wall station was evaluated to determine the per-
cent reduction in the cumulative metal loading per unit area in
the rinsates over the monitoring period relative to the untreated
control/background area. The concentration of each metal in the
rinsates was converted to a mass loading per unit area based on
the volume of the rinsate and the surface area of the mine wall
station. A cumulative mass of each metal for each mine wall
station was calculated over the duration of the test period. Per-
cent reduction was based on the difference between the average
mass per unit area of each metal generated from treated areas
relative to the mass per unit area of metal from the untreated
control station (Ref. 2). The equations used for this evaluation
are provided in detail in the project quality assurance project
plan (QAPP).
Similarly, the mean pH for each treatment area was com-
pared to the mean pH for the control area to determine if the
treated areas had positively impacted the acid generation of
the highwall (i.e., the pH was higher in the treated areas when
compared to the control).
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2. Site Characterization and Pretreatment Activities
Characterization of the highwall was required for the
demonstration to determine whether the treatment technologies
impacted/passivated the acid generation occurring on the high-
wall. Tasks performed to characterize the highwall included
securing all historical data pertaining to the project site, drill-
ing core holes, and performing water injection tests. Oriented,
horizontal, and vertical cores were collected prior to implemen-
tation of the technologies. The purpose of the cores was to
characterize the site with respect to the geological description
(i.e., fracture orientation, patterns, spacing, and mineralogical
aperture), geochemical description (i.e., visible depth of oxida-
tion, pH in fractures), and hydrogeological description (i.e., wa-
ter injection at select intervals to determine wall permeability
and characteristics).
2.1 Demonstration Site Description
The project site for the field application of the four selected
innovative highwall technologies was GSM, an operating gold
mine located in Jefferson County, 8 miles northeast of White-
hall, Montana (Figure 2-1). The northwest side of the open-pit
highwall at the GSM was selected as the demonstration area
(Figure 2-2).
As well as providing the project site, GSM also provided
the following in-kind support:
- removal of fallen rock below the selected highwall
area;
Figure 2-1. GSM location map.
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Figure 2-2. GSM open-pit and Activity III, Project 26 site.
- cleanup of the highwall to reduce loose rock for safety
purposes;
- a manlift with an operator for field sampling events;
- safety oversight;
- laboratory facilities for sample preparation and analy-
sis; and
- technical assistance with subcontractor oversight.
The open-pit benches at the project site were 50 feet (ft)
high and had near vertical slopes. Each technology was spray
applied to a 50-ft-high by 50-ft-wide area of the highwall by
the technology provider with oversight by MSB (Figure 2-3).
A total of five test plots were located on the highwall, which
included one plot for each of the four technologies (Plots B - E)
and an additional plot designated for background and control
(Plot A).
2.2 GSM Historical Data
Historical data were obtained from GSM prior to initiation
of the field testing. The historical data were water quality data
obtained from a monitoring well in the highwall at GSM to de-
termine the average concentrations for constituents of interest.
The data are summarized in Table 2-1. The acquired data were
compared to the National Primary and Secondary Drinking
Water regulations for pH, Cu, Fe, Mn, Ni, and Zn. The concen-
trations for most metals and sulfate (SO4) were high; however,
there is no a standard for SO4.
2.2.7 Geology
GSM is located on the southern flank of Bull Mountain.
A general map of the surficial geology is shown in Figure 2-4.
Bull Mountain is composed of ancient sedimentary rock that
was deposited in a shallow sea during late Precambrian time.
The Precambrian rock types in the vicinity of the mine include
sandstone, siltstone, and shale. These rock units are known as
the Belt Supergroup and have been referred to as the LaHood,
Greyson, and Newland Formations and the Bull Mountain
Shale.
2.2.2 Tectonic Activity
Approximately 70 to 85 million years ago, a period of
tectonic activity known as the Laramide Orogeny occurred
during Cretaceous time. During this time near GSM, regional
compression of the earth's crust resulted in folded blocks of
rock bounded by high-angle faults. Precambrian rocks were
penetrated by igneous intrusions and overlain by volcanic ma-
terials. Cretaceous-age intrusive rocks in the vicinity of the
mine include latite porphyry intrusions and numerous smaller
lamprophyre dikes (Ref. 3).
After the Laramide Orogeny, the landscape was relatively
stable with residual weathering of the rock surface that became
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Figure 2-3. Landscape.
Table 2-1. GSM Highwall Monitoring Well Data Analytical Pa-
rameter Analytical Result (mg/L Unless Otherwise Indicated)
Analytical
Parameter
pH
so4
Al
Fe
Mn
Ni
Zn
Cu
Analytical Result
(mg/L Unless Other-
wise Indicated)
4.35 s.u.
4,773
Data not available
1,042
18.9
3.15
29.3
Data not available
Primary and Secondary
National Drinking Water
Standards
6.5 to 9
250
0.05-2.0
0.3
0.05
0.1
2.1
1.3
Note: The analytical results listed above are for the dissolved metal
concentrations, and the units for metals concentrations are in parts
per million (ppm)
mg/L = milligrams per liter
the dominant geologic process. During the later Tertiary pe-
riod, tectonic activity resumed with a period of relaxation of
compression or extension of the earth's crust. This formed the
shallow marine basin east of Bull Mountain, which was later
filled with Tertiary- and Quaternary-age sediments. This sedi-
ment-filled valley is presently the site of the GSM mine, mill
buildings, tailings impoundments, and North and East Waste
Rock Dumps.
The Precambrian sedimentary rock near the mine site
is highly mineralized or impregnated with sulflde minerals,
mostly pyrite. When these sulflde minerals become exposed to
water and air, they can produce AMD. However, low levels of
gold are present in the Precambrian sedimentary rocks, and the
primary concentration of gold is a 700-ft-diameter breccia pipe
of late Cretaceous age. The breccia contains a zone of broken,
angular rock fragments cemented together by silica, sulfldes,
barite, and carbonate. The breccia pipe cuts through both the
Precambrian sedimentary and Cretaceous intrusive rock at an
angle plunging west-southwest.
Gold occurs primarily as micron-sized particles of ore
that are disseminated within the breccia pipe and immediately
adjacent rocks. Free gold occurs interstitially as microscopic
particles between pyrite grains. Gold-bearing tellurides are
present in minor amounts. Total reserves at GSM, including
those mined since 1983, include approximately 55 million short
tons grading 0.059 ounce of gold per ton with an average waste
ore stripping ratio of 7.4:1 (Ref. 3).
The average range of pyrite in GSM ore is between 3% and
5%; concentrations of up to 20% can occur but are not typical.
The relatively fine texture of pyrite enhances the surface area
available for AMD generation. Other metallic minerals occur
in minor amounts within waste rock and vary in accordance to
position in the ore body. Metals of potential concern for water
treatment of effluent include Al, cadmium (Cd), Cu, Zn, and
arsenic (As). However, for this demonstration, the metals of
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Figure 2-4. Surficial geology in the area of GSM.
concern were Al, Cu, Zn, Fe, Mn, and Ni. With the exception of
Al, the other metals are predominately associated with sulfide
complexes and minor oxides.
2.3 Pretreatment Core Drilling and Water Injec-
tion Testing
To geologically characterize the highwall, pretreatment
core drilling and water injection testing were performed using a
Hagby 1000 core drill. Five exploration core holes were drilled
to investigate the parameters of the highwall. The cores were
analyzed for fracture frequency; infilling and staining; dip or
orientation of any discontinuity, which was quantified by rock
quality designation; geology; and pH of the exposed fractured
surfaces and the nonfractured rock surface. Approximately ev-
ery 5 ft, pH measurements were taken on the surface of the core
to determine the depth of oxidation and acid formation. De-
tailed core logs and water injection testing results are provided
in Appendix A. The core holes drilled included:
- GS2-H, TD = 50 ft, inclination = -5 degrees;
- GS3-45, TD = 73 ft, inclination = -45 degrees;
- GS3-H, TD = 20 ft, inclination = -5 degrees;
- GS3-V, TD = 20 ft, inclination = -90 degrees; and
- GS4-H, TD = 20 ft, inclination = -5 degrees.
2.3.7 Water Injection Testing
Water injection testing was performed to determine the
hydraulic characteristics (i.e., permeability) of the highwall
(consolidated rock) at predetermined intervals below ground
surface (bgs) and into the highwall. The water injection testing
was performed after the core holes were drilled to a final depth,
cleaned, and blown out. Inflatable, pneumatic packers were
spaced on the drill stem and inflated to isolate the test interval.
Testing started at the bottom of the drill hole, and an upstage
testing method was used as tests were repeated until the entire
hole was hydraulically characterized.
Multiple injection (pressure) tests were performed on GS3-
45 and GS3-H, and (if possible) multiple tests were performed
at each interval. This method involved testing each interval
while increasing the pressure at stepped intervals. Each pres-
sure step was maintained from between 10 to 25 minutes and
water intake readings every 5 minutes on a continuous basis
(see Appendix B).
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3. Technology Identification Activities
Several activities were undertaken by MSB before the
demonstration could be conducted. These activities included
Several activities were undertaken by MSB before the demon-
stration could be conducted. These activities included select-
ing technology providers, selecting a demonstration site and
analytical laboratory, preparing regulatory documents and site
access agreements, and selecting the methods used to evaluate
each technology. The selection of the technologies involved
researching detailed literature in reference to technologies ap-
plicable to the demonstration.
3.1 Technology Descriptions
The ore body at GSM is primarily composed of sulflde
minerals, which when exposed to air and water can cause AMD
generation. The metals concentrations and parameters of con-
cern that were analyzed for this demonstration included pH, Al,
Cu, Be, Mn, Ni, Zn, and SO4. The four innovative technologies
applied to the highwall were:
- BARS technology developed by Intermountain Poly-
mers of Idaho Balls, Idaho;
- EcoBond developed by MT2 of Denver, Colorado;
- UNR/MgO technology developed by the UNR; and
- UNR/KP Passivation technology developed by Dupont
and presently owned by UNR.
3.1.1 PARS
The primary constituent of Intermountain Polymer's BARS
technology is a byproduct of the agricultural and wood industry.
The BARS material is a two-component, acid-catalyzed binder
that produces a resistant, stable polymer when mixed that is
environmentally innocuous. Polymerization of furfuryl alcohol
occurs through a condensation reaction that occurs when mixed
with a strong acid catalyst. Care should be taken to avoid free-
standing catalyzed resin in order to prevent localized excessive
exothermic reactions.
Bor this demonstration, the technology used acid-cured
polymers to seal and encapsulate the highwall material, elimi-
nating the need for repeated future applications due to depleted
effectiveness. Other studies have determined that this product
is very resistant to dissipation or erosion over time (Ref. 4).
The technology has been used for years in the oil industry to
consolidate underground wand formations and is supported by
numerous patents.
Additional work was performed by the Environmental and
Waste Technology Center, Department of Advanced Technol-
ogy, Brookhaven National Laboratory for the DOE under the In
Situ Remediation Integrated Program. Under this program, a
laboratory evaluation was performed to determine durability of
polymer grouts for application as subsurface hydraulic and dif-
fusion barriers. The acid-cured polymer (i.e., modified furfuryl
alcohol) testing included hydraulic conductivity, compressive
strength, flexural strength, splitting tensile strength, water im-
mersion, acid resistance, base resistance, solvent resistance,
wet-dry cycling, chloride diffusivity, thermal cycling, and ir-
radiation stability testing (Ref. 4).
By adding the information obtained from patents used in
the oil industry, further testing was performed by Intermoun-
tain Polymers on several variations of mining waste (i.e., fine
grain mine tailings and waste rock having both acidic and basic
characteristics).
For highwall application, the advantages that assisted with
the selection of the technology were:
- the material provided a permanent layer over the waste
material that was acid, base, and solvent resistant;
- the material was stable and polymerized further during
wet-dry and thermal cycling;
- the material binds to the waste rock and, as a result,
increases the physical stability of the highwall;
- ultraviolet light does not degrade the material;
- the material is inexpensive because it uses a byproduct
from a wastestream;
- the material can be spray applied and has a viscosity of
approximately 8 centipoise (cp), which is close to that
of water (i.e., 1 cp); and
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- hydraulic conductivities reached with a composite
polymer material ranged between 4.5 to 4.8 by 10~9
centimeters per second (cm/s).
3.1.2 EcoBond
EcoBond is a proprietary process able to chemically bind
with metals in contaminated soils and other wastes. The phos-
phate-based AMD treatment process was developed to prevent
the oxidation of pyrite on mine dumps, highwalls, and in un-
derground mine workings. The general technology formulation
consists of a mixture of additives containing oxygen, sulfur,
nitrogen, and phosphorous; each additive has an affinity for a
specific class of metals (Ref. 5). By combining ferrous iron
(Fe+2) from the rock with EcoBond, a stable, insoluble com-
pound is formed that renders the Fe+2 in the pyrite unavailable
for oxidation by permanently coating all surfaces. A second,
equally stable compound that coats all surface areas is formed
by the reaction of EcoBond with the oxidizing ferric iron (Fe+3)
(Ref. 3).
Several sources provided knowledge of the EcoBond tech-
nology and its effectiveness for reducing AMD. These sources
had ongoing demonstrations that used the product; the projects
involved using EcoBond for microencapsulation of unoxidized
waste rock and passivation of AMD in oxidized waste material
(Ref. 6). Also, prior to this demonstration, EcoBond had been
deployed to stabilize lead (Pb)-contaminated soils for EPA at
the DeLatte battery recycling site and at Summitville, Colo-
rado, where a similar product was used to passivate an open-pit
highwall, (Ref. 5).
For highwall application, the advantages that assisted with
the selection of the technology are listed below.
• The process converts each metal contaminant from its
leachable form to an insoluble, stable nonhazardous
metallic complex.
• The process forms a stable, insoluble compound that
coats the pyrite and any other surfaces that it contacts.
• The process was designed to treat soils in situ, thereby
reducing handling, transportation, and disposal costs
associated with secondary wastes generated by many
conventional technologies.
• The treatment technology can be spray applied to sur-
faces.
• The viscosity of EcoBond is comparable to water (i.e.,
1 cp), allowing the treatment to contact all surfaces
contacted by runoff from precipitation events.
• Runoff water from the treated surfaces has an in-
creased pH because of the application of the treatment
technology, thus reducing the toxicity of the receiving
waters.
3.1.3 UNR/MgO Technology
The Mackay School of Mines at UNR has been researching
and developing technologies able to mitigate AMD. The ap-
proach of the UNR technologies was to coat the sulfides present
in the ore. Over the past several years, DuPont developed a
novel coating method known as a passivation technology. The
Dupont Passivation Technology (Refs. 7 and 8) was donated to
UNR for further process development and commercialization
with the intent of using the technology on fresh rock or waste
rock piles without rehandling the mining waste (Ref. 9).
The UNR/MgO technology is a variation of the original
technology donated by DuPont. The basic permanganate so-
lution that produces the inert manganese-iron oxide layer was
eliminated. The UNR/MgO technology was designed to create
an inert coating on the sulfide phase by contacting the sulfide
rock with an MgO solution.
For highwall application, the advantages that supported the
selection of the UNR/MgO technology are listed below.
• The process creates an inert layer on metal-sulfide
minerals when contacting the sulfide with the basic
MgO solution, which produces an insoluble, stable
layer on the sulfide mineral in the highwall rock.
• The process forms stable, insoluble coating on the py-
rite and any other surfaces that it contacts, preventing
contact of atmospheric oxygen/water during weather-
ing, thus preventing sulfuric acid generation.
• The process was designed to treat soil and rock ma-
terial in situ, thereby reducing materials handling,
transportation, and disposal, which reduces the costs
associated with secondary waste generation and man-
agement that occurs when using many conventional
technologies.
• The MgO treatment technology can be spray applied
to surfaces.
• The viscosity of MgO treatment solution is comparable
to water (i.e., 1 cp), allowing the treatment to contact
all surfaces contacted by runoff from precipitation
events.
• Runoff water from the treated surfaces has an in-
creased pH because of the application of the treatment
technology, thus reducing the toxicity of acidic receiv-
ing waters.
3.1.4 UNR/KP Technology
The basic permanganate technology (UNR/KP) was the
original passivation technology developed and donated by
Dupont to UNR. When the UNR/KP technology is applied
and contacts the surface of sulfidic material, it creates an inert
layer on the sulfide phase of the rocks and produces an inert
manganese-iron oxide layer. This layer prevents contact with
atmospheric oxygen/water during weathering of the sulfide
rock, thus preventing sulfuric acid generation. Another critical
element of the process is the addition of trace amounts of MgO
during the initial pH adjustment (Ref. 9). Magnesium oxide
addition enhances the coating strength.
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The UNR/KP was also evaluated in field-scale demonstra-
tions at the Gilt Edge Mine located in South Dakota for an EPA
treatability study and at GSM on the surface waste piles, both
weathered and nonweathered, and on an approximately 100-ft
length of highwall. At the GSM financed field-scale demon-
stration, the bench above the highwall plot was saturated with
the treatment; the solution was then spray applied to the face of
the highwall. Results from the demonstrations cited above are
in the final reporting stages, and the results will not be provided
in this report.
For highwall application, the advantages that supported the
selection of the UNR/KP technology are listed below.
• The process creates an inert layer on the sulfide phase
by contacting the sulfide with a basic permanganate
solution to produce an inert manganese-iron oxide
layer. This layer prevents contact with atmospheric
oxygen/ water during weathering of the sulfide rock,
thus preventing sulfuric acid generation.
• The process was designed to treat soil and rock ma-
terial in situ, thereby reducing materials handling,
transportation, and disposal, which reduces the costs
associated with secondary waste generation and man-
agement that occurs when using many conventional
technologies.
• The UNR/KP treatment technology can be spray ap-
plied to surfaces.
• The viscosity of UNR/KP treatment solution is com-
parable to water (i.e., 1 cp), allowing the treatment to
contact all surfaces contacted by runoff from precipi-
tation events.
• Runoff water from the treated surfaces has an in-
creased pH because of the application of the treatment
technology, thus reducing the toxicity of acidic receiv-
ing waters.
• The costs of the chemicals required in the treatment
technology formulation are inexpensive and are com-
mercially available.
3.2 Highwall Technology Evaluation Methods
Several methods were used to evaluate the applied highwall
technologies. In this demonstration, both field and laboratory
evaluations were performed. The monitoring procedures and
evaluation methods were addressed in the project QAPP (Ref.
2) and are described further in this section.
The QAPP was developed and submitted to the EPA Proj-
ect Manager for review and approval. The QAPP was prepared
according to the EPA publication Preparation Aids for the De-
velopment of Category II Quality Assurance Project Plans (Ref.
10). Additionally, the QAPP served as a standard operating
procedure document for sampling; sample preparation, labora-
tory analysis, and data reduction. A summary of QA related
activities is provided in Section 6.
3.2.1 Residual Wash Field Sampling
To validate the objectives of this project, an experimental
design was created using the Mine Wall Water Sampling Tech-
nique to evaluate the effectiveness of the technologies and to
provide an in situ prediction of the water chemistry from the
highwall. The technique was developed for the Canadian Mine
Environment Neutral Drainage (MEND) Program (Ref. 11).
The initial primary project objective was to determine if
the highwall areas treated by the technologies had an impact
on the total metal loading per unit area (i.e., Al, Cu, Fe, Mn,
Ni, and Zn) in residual wash samples as compared to the total
metal loading in wash residual samples from the untreated/
background area at Plot A (Figure 2-3).
The second primary project objective was to determine if
the highwall areas treated by the technologies were impacted
with respect to pH. Results from the residual wash sampling
compared the pH in residual samples from the untreated areas
to that from the treated areas.
The MEND technique (or the technique developed by
Morin) requires that sample ports be attached below the mine
wall station and covered with plastic to prevent contamination.
However, the mine wall sample stations for this demonstration
were not covered to allow weathering effects to occur. Leaving
the mine wall sample stations exposed allowed for airborne par-
ticulates, erosional material from water flowing from the road
above, and earth movement debris to collect in the sample ports.
As a result, these factors could have affected the variability and
replication of the parameters analyzed.
Mine wall sample stations were installed at five locations
on each of the treated and untreated highwall plots. Prior to
technology emplacement in September 2001, rinsates were col-
lected for background data at each mine wall sample station.
Once all of the technologies had been applied, residual wash
water samples were taken from the mine wall sample ports in
July, September, and November of 2002 to determine acidity
and leachability of metals.
The sampling strategy was included in the experimental
design, and quality control (QC) documents. Sample locations
and time intervals between sampling events were established to
aid in the identification of trends and to produce adequate data
to evaluate the overall performance of the technologies. The
type of laboratory analysis for each sample was established to
ensure there was adequate data. The HKM Laboratory located
in Butte, Montana, was selected to perform the necessary ana-
lytical testing of the sampling events at GSM.
3.2.2 Laboratory Testing - HC Testing
The HC testing was performed to simulate natural weath-
ering procedures and to accelerate sulfide mineral oxidation.
The HC testing procedure is cyclic, during which the sample
is subjected to 3 days of dry air permeation, 3 days of water
saturated air permeation, and 1 day of water washing with a
fixed volume of water. The American Society for Testing and
Materials (ASTM) procedure D5744-96 Standard Test Method
-------
for Accelerated Weathering of Solid Materials Using a Modified
Humidity Cell requires a minimum test duration of 20 weeks;
however, it is recommended that the testing be conducted for at
least 40 weeks (Ref. 12).
Representative samples from each technology plot were
collected from the highwall and screened using a Gilson labo-
ratory-scale vibratory screen at the GSM laboratory to 1/4-inch
by 1/2-inch size fractions. The samples were blended and then
split with a riffle splitter to ensure a representative sample was
given to each technology provider.
The technology providers applied their technologies to
the HC sample at the same time as the field application was
conducted on the highwall. The samples were fully saturated,
making the dosages to the HC samples much different than
from the highwall applications. After the final application of
the technologies to the highwall, the samples were shipped to
McClelland Laboratories, Inc. (MLI) for modified HC testing.
Identical splits of each GSM highwall sample (five in total)
were received; one was untreated and designated GSM, and
the other four (one per technology) were treated using PARS,
EcoBond, UNR/MgO, and UNR/KP. All of the samples were
in good condition; however, the PARS sample had to be broken
to reduce the size fractions to fit into the sampling equipment.
Because the sample was broken, some of the surfaces were ex-
posed and the uncoated surfaces were visible. All untreated
and treated HC samples were conducted in triplicate. An in-
ductively coupled plasma spectrometer (ICP) multielemental
scan was performed on the treated and untreated feed sample
for characterization.
Test durations were originally scheduled for 21 weeks but
were extended to 31 weeks and subsequently to 41 weeks. Test
suspension duration was 43 days after week 21 before reinitia-
tion and 131 days after week 31 before reinitiation. Humidity
cell test solids were left in the cells and stored in a freezer dur-
ing test suspensions.
Humidity cell testing samples were monitored on a weekly
basis at MLI, and the sampling procedures were included in
the sampling plan. The analytical parameters monitored and
recorded by MLI personnel from the effluent samples included
temperature, pH, oxidation-reduction potential (EH), electric
conductivity (PC), SO4, Fe3+ and Fe2+, acidity, and alkalinity
at maximum contaminant level (MCL). The project-specific
QAPP contains a detailed description of the experimental de-
sign (Ref. 2).
10
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4. Field Demonstration
This project field demonstration evaluated the ability of the
four technologies to decrease or eliminate acid generation from
treated areas of the highwall using an untreated highwall area
for comparison of results. The following section provides a
general description of the field application procedures used by
each technology provider. Due to the proprietary nature of some
of the applied technologies, some details were not included in
this report. If further information on the process is needed, the
technology provider should be contacted.
4.1 Technology Application Descriptions
At the GSM project site, each of the four technologies
were spray applied to a designated plot area on the face of the
highwall. Each technology vendor provided the materials, ap-
plication equipment, and expertise for the application of their
technology. Each technology provider used a different formu-
lation and volume of treatment solution during the application
procedure.
Five 50-ft by 50-ft plots were surveyed and cleared of loose
and fallen debris by GSM and used for the field application of
the technologies (Figure 2-3). Plot A was designated as the
background or control plot and was sampled and monitored
identically to the technology plots. Sampling results from the
technologies were compared to the background plot to deter-
mine the effectiveness of each technology. The four innovative
technologies and the plots (Figure 2-3) on which each technol-
ogy was applied were the PARS technology on Plot B, EcoBond
on Plot C, UNR/MgO technology on Plot D, and UNR/KP tech-
nology using potassium permanganate solution on Plot E.
4.1.1 PARS
The Intermountain Polymers EARS technology is com-
prised of byproducts from the agricultural and wood industry
and is a two-component, acid-catalyzed binder that produces a
resistant, stable polymer. For this demonstration, Intermountain
Polymers formulated and spray applied the treatment technol-
ogy to Plot B.
Intermountain Polymers personnel applied a total volume
of 200 gallons (gal) of a low viscosity solution (approximately
1 to 3 cp) in two equal applications. The treatment solution
was spray applied at a rate of 10 gallons per minute (gpm) on
the highwall surface (Plot B). Each 5-gal batch of solution was
mixed with 2% by volume proprietary acid catalyst, and the pH
of the monitored solution was 4.5 (since the solution is acid
catalyzed and the pH of the wall remains slightly acidic). The
solution was applied to the surface of the highwall immediately
because an exothermic reaction occurs when the catalyst is
mixed with the furfuryl alcohol solution. On application, the
PARS coating turned the highwall a dark blackish brown color.
The EARS formulation for this demonstration allowed for a set
time of 20 minutes using 2% catalyst. If the set or cure time
needs to be increased, then the amount of catalyst used would
be reduced.
To reach the full height of the plot, a person in a manlift
sprayed the EARS solution onto the wall using an ordinary, 5-
gal capacity, industrial paint sprayer. A second application (still
using the initial 200 gal of solution) was spray applied after the
initial coat was allowed to set for more than 1 hour. The second
coat was applied to seal, provide additional stabilization, and
ensure comprehensive coverage of the highwall surface. Figure
4-1 shows the EARS solution being applied to the surface of
the highwall.
4.1.2 EcoBond
EcoBond, a phosphate-based AMD treatment process de-
veloped to prevent the oxidation of pyrite on mine dumps, high-
walls, and in underground mine workings was spray applied in
the field by MT2. For this demonstration, 300 gal of EcoBond
was sprayed on the open-pit highwall using a hydromulch spray
cannon. Plot C was coated several times with the PcoBond
solution to allow sufficient coverage of the wall surface. The
proprietary formulation was sprayed at a high pressure and used
a low volume of water. The application method used ensured a
comprehensive coverage of the highwall and sufficient contact
of the treatment solution on the rock surface.
Once applied, EcoBond is designed to react with the pyrite
within 24 to 48 hours. The pH stabilizes at an environmentally
safe level and, as a result, the available Fe+3 in the system de-
creases. The minimum required air and surface area tempera-
11
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Figure 4-1. PARS being spray applied on the GSM open-pit highwall
at PlotB.
ture was 32°F at the time of installation (Ref. 3). A picture of
the spray application of the EcoBond technology is shown in
Figure 4-2.
4.1.3 UNR/MgO Technology
UNR developed the MgO passivation technology to create
an inert coating on the sulfide phase by contacting the sulfide
rock with an MgO solution. Technical personnel from UNR
formulated the MgO treatment solution, and the spray applica-
tion of the treatment solution was performed by UNR's techni-
cal personnel and subcontractor. A Kenworth hauling manlift
was retrofitted with a triple-nozzle spray system that did not
require a person in a manlift basket for application. This equip-
ment allowed the operator to apply the treatment solution from
a metal shielded cab (Figure 4-3).
A total of 2,000 gal of caustic pretreatment wash was spray
applied to Plot D of the highwall to raise the wall pH from ap-
proximately 3 or 4 to a pH greater than 11. The pretreatment
wash was spray applied at a rate of 22 gpm using the spray sys-
tem attached to a manlift. Once the desired pH was achieved,
a final 2,000 gal of MgO solution was sprayed to the highwall.
The viscosity of the solution was between 1 and 2 cp, which
allowed the solution to penetrate the fractures and completely
cover the surface area of the wall. Upon completion of the ap-
plication, there was no visible indication of the treatment solu-
tion application other than the wall rock was clean and washed
in appearance.
4.1.4 UNR/KP Technology
Dupont developed and patented a permanganate passivation
technology that was donated to UNR. UNR has developed field
applications using the passivation technology. UNR's passiv-
ation technology is used to create an inert layer on the sulfide
phase by contacting the sulfide rocks with a basic permanganate
solution to produce an inert manganese-iron oxide layer. This
layer prevents contact with atmospheric oxygen/water during
weathering of the sulfide rock, thus preventing sulfuric acid
generation.
Technical personnel from UNR formulated the permanga-
nate treatment solution, and the spray application of the solu-
tion was performed by UNR's technical personnel and subcon-
tractor. As with the MgO technology, a Kenworth manlift was
retrofitted with a triple-nozzle spray system that did not require
a person in the manlift basket. The equipment allowed the op-
erator to apply the treatment solution from a metal shielded cab
(Figure 4-4).
The initial application of the treatment technology to Plot
E included spray applying 4,000 gal of caustic pretreatment
solution to the highwall to adjust the pH of the wall from ap-
proximately 3 to greater than 12. After the pH of the highwall
was raised to 12, then the permanganate treatment solution was
applied and allowed to cure. Upon initial application of the per-
manganate solution, the surface of the highwall and the snow
in the area were bright pink in color, typical of permanganate
solution. However, after several hours, the pink color had faded
and there was little indication that the treatment solution had
been applied.
12
-------
Figure 4-2. Spray application of the EcoBond technology onto the GSM highwall at Plot C.
Figure 4-3. Field application of the UNR/MgO technology on the GSM highwall at Plot D.
13
-------
Figure 4-4. Spray application of the UNR/KP technology on the GSM at Plot E.
14
-------
5. Site and Technology Characterization Results
The primary objectives of this project were to determine
the impact of the treated area for each technology on the to-
tal metal loading per unit area and to determine the pH of the
rinsates compared to the rinsates from the untreated area. An
actual comparison of the four passivation technologies was not
one of the objectives. The results from the site characterization,
the residual wash field sampling, and the laboratory sampling
performed by MLI are provided and discussed in this section.
5.1 Core Drilling and Water Injection Testing
Results
The core drilling and water injection testing were per-
formed to characterize the highwall and were performed be-
fore the treatment technologies were applied to the wall. The
information acquired during characterization of the site was
provided to the technology providers so they could refine the
technology design, formulations, and application procedures.
The information also provided in-depth information of the wall
characteristics (i.e., depth of oxidation, fracture density, rock
type, hydraulic characteristics). The overall results from the
core drilling and mine wall testing established that the geology
and wall characteristics at each plot location had similar proper-
ties, see Appendix A and C. Thus, all the technologies were
applied to highwall surfaces having similar properties.
5.1.1 Pretreatment Core Drilling Results
In June 2001, Bush Drilling Inc., drilled five core holes into
the highwall at the project site. Cores measuring 5 ft [1.524
meters (m)] using an NQ drill rod [1-7/8 inch inner diameter
(ID)] were drilled and retrieved using a triple-tube core barrel.
The five core holes drilled included:
- 1 - 20-ft (6.096-m) vertical core hole (GS3-V);
- 1 - 70-ft (21.336-m) - 45-degree core hole (GS3-45);
- 1 - 50-ft (15.5-m) - 5-degree, near-horizontal core hole
(GS3-H); and
- 3 - 20-ft (6.096-m) - 5-degree, near-horizontal core
hole (GS2-H and GS4-H).
In general, the Precambrian sedimentary rock drilled and
cored at the project site was highly mineralized and impreg-
nated with sulfide minerals, mainly pyrite. The core extracted
from the highwall was rubble for approximately the first 3 ft
and contained numerous fractures to approximately 10 ft from
the drill face. From analyzing the core, it is apparent that the
fracture apperature becomes narrow after the first 10 ft and the
iron oxide fracture infilling is nonexistent. It could be assumed
that the sulfide minerals between 0 and 10 ft into the highwall
are being exposed to water and air by mining activities produc-
ing AMD (see Appendix A).
The core holes that were drilled before the highwall was
treated provided the following information.
• On average, the majority of the Fe-stained fractures
were observed from 0 to 9 ft into the highwall. Most
of the oxidation of pyrite was associated with fracture
flow, and most of the oxidation occurring in the first 9
ft into the highwall can be attributed to more numer-
ous fractures and wider fracture apertures in the wall.
• The lowest pH (between pH 2.7 and 3.8) taken on the
highwall were on the wall surfaces that are exposed to
fluctuating weather conditions and accelerated oxida-
tion. The pH values corresponded with the depth of
visible iron oxide on the fractures. Between 0 and 9
ft, the pH was 4.0.
• The pH measurements taken in the fractures show that
from a depth of 9 ft to the end or bottom of the core
holes, the pH ranged from 5 to 6 and the pyrite ex-
posed on the fracture surfaces at these depths was not
oxidized (see Appendix A).
5.1.2 Water Injection Testing Results
Overall, the permeability of the highwall followed a simi-
lar pattern as the fracture filling and pH. At the project site, the
permeabilities of the highwall between approximately 5 and 20
ft were hydraulic conductivity (K) = 10~4 cm/s and, at greater
than 20 ft into the wall, the permeability was K = 10'5 to 10'6
cm/s. Appendix B provides a summary of the water injection
15
-------
testing results. Table 5-1 lists the stages or injection intervals,
the average pressure applied during the testing, a description of
the tested interval using the Lugeon method of analysis, and,
finally, the range of permeabilities measured at each interval
tested (see Appendix B for more detailed results and descrip-
tions.)
From the water injection testing performed on the core
holes, it was determined that the permeability of the wall de-
creases directly in relation to the depth drilled. From the injec-
tion testing results, it can be assumed penetration of the spray-
applied, low viscosity, highwall technologies would mainly
occur in the area having the highest permeability (i.e., 0 to 20 ft
bgs). However, the trends of the iron staining indicate that most
of the water movement occurs within 0 to 10 ft into the wall. It
also indicates that the surface was fractured during drilling and
blasting, and the resultant fractures propagate to approximately
50 ft into the wall; past this depth, the fractures are usually as-
sociated with natural occurring fault systems created during
tectonic movement.
5.2 Mine Wall/Rinsate Sampling Results
The mine wall sampling technique was used to determine
the kinetic acid rock drainage characteristics of in situ rock or,
in this instance, the highwall surface at GSM. The residual
wash from the mine wall sampling was analyzed for wall pH,
sulfate, and total and dissolved metals. The data were then
provided to EPA for statistical analysis (see Appendix D). The
three field residual wash sampling events that were evaluated
statistically by EPA occurred on July 22, September 19, and
November 4, 2002.
Table 5-1. Summary of the variability of the mean and the sample size both before and after the application of the technologies on the test plots
Descriptive Statistic for pH for the September 2001 Highwall Sampling Event taken Prior to the Application of the Treatment Tech-
nologies
Pretreatment
Control (GSM)
PARS
EcoBond
UNR/MgO
UNR/KP
Mean
3.4
3.1
2.9
3.2
3.2
Variance
0.0325
0.0099
0.0301
0.2022
0.1403
Sample Size
5
5
5
5
5
Descriptive Statistic for H for the July/August 2002 Highwall Sampling Event
Treatment
Control (GSM)
PARS
PcoBond
UNR/MgO
UNR/KP
Mean
2.9
4.6
4.3
3.2
4.0
Variance
0.5140
0.1135
4.3001
NA
1.1618
Sample Size
4
4
3
1
5
Descriptive Statistic for pH for the September 2002 Highwall Sampling Event
Treatment
Control (GSM)
PARS
PcoBond
UNR/MgO
UNR/KP
Mean
3.0
4.9
3.2
3.2
3.2
Variance
0.0506
0.0245
0.4714
NA
0.0107
Sample Size
2
4
3
1
5
Descriptive Statistic for pH for the November 2002 Highwall Sampling Event
Treatment
Control (GSM)
PARS
PcoBond
UNR/MgO
UNR/KP
Mean
3.4
4.9
3.5
3.4
3.4
Variance
0.0684
0.0511
0.1314
NA
0.0062
Sampling Size
2
4
3
1
5
16
-------
5.2.7 Summary of Statistical Analysis
From the field sampling events, residual wash data were
statistically evaluated by EPA to determine if any significant,
statistical differences were observed when comparing the back-
ground/control plot and the treated plots. The complete data
set from the mine wall sampling can be found in Appendix C,
and the three EPA statistical analyses are located in Appendix
D. The analyzed field parameters included pH, six total metal
loadings, and six dissolved metal loadings.
In the EPA reports, 13 statistical analyses were performed
and included box plots by treatment level, scatter plots, descrip-
tive statistics, and the results of a Kruskal-Wallis test and mul-
tiple comparison procedure. The data were analyzed as a com-
pletely randomized design via a one-way treatment structure
with five levels using the nonparametric Kruskal-Wallis test.
Results from the analysis determined that there were sta-
tistically significant differences between the control (Plot A)
and some of the treatments for all analysis variables except the
dissolved metal loadings for Al. It was also determined that the
EARS treatment technology performed the best; it was statisti-
cally different than the control (p-value < 0.05) for all variables
except sulfate.
The EcoBond technology appeared to be the treatment that
was not statistically different from the control for any variable.
It was not possible to draw any conclusions on technology per-
formance regarding the UNR/MgO technology since it only had
one sampling port. The detailed statistical reports containing
the results are provided in Appendix D. A summary of the vari-
ability of the mean and the sample size are presented in Table
5-1 for the pH of the high wall. For each demonstration plot,
five randomly selected sampling locations were designated.
From the results presented in Table 5-1, it is apparent that the
number of sample ports on most of the plots decreased over
time. This was due to highwall movement, loss of sample ports,
and unsafe conditions in the area of the sample ports.
Because the demonstration involved just one application of
each select treatment on one plot/site, the statistical inferences
and conclusions extend only to this site. There was no guaran-
tee that the treatments would perform in a similar manner at
another site.
5.2.2 Residual Wash pH Results
At the GSM project site, the measured pH of the highwall
prior to technology application ranged from 2.7 to 3.8. Listed
as a critical parameter in the project QAPP, the pH was used
to compare the effectiveness of the technologies. The pH for
each of the three sampling events was graphed and is shown in
Figures 5-1, 5-2, and 5-3. It should be noted that in the figures,
the samples denoted as GSM were taken from the background
(Plot A) sample area, and the MT2 was the EcoBond technology
sample location (Plot C). All other technologies were denoted
as they were throughout the text. The final pH of the residual
wash from the mine wall sample stations for each treated area
averaged were:
- GSM (background), pH = 3.4;
- PARS, pH = 4.9;
- EcoBond, pH = 3.5;
- UNR/MgO, pH = 3.4; and
- UNR/KP, pH = 3.4.
Upon comparison of the data, the average final pH of the
background plot (Plot A) remained within the range of the ini-
tial pH values taken on the highwall prior to the technology
applications.
When comparing the pH values for the PARS technology, it
should be understood that this technology creates an acid-cata-
lyzed coating, (i.e., for EARS to cure properly, an acid solution
is mixed with the alcohol component of the formulation) and,
when all of the components of the sealant are mixed, the pH of
EARS ranges between 4 and 5. Throughout this demonstration,
the pH of the EARS treated highwall remained between 4 and 5
and did not fall below the expected pH for the technology.
The EcoBond, UNR/MgO, and UNR/KP treatment tech-
nologies neutralized the highwall during initial application
to achieve a desired wall pH, which would allow the desired
chemical reactions to occur. The neutralized highwall pH for
the technologies were pH = 9 -10 for EcoBond; pH = 11 for
UNR/MgO; and pH = 12 for UNR/KP. Comparing the pH val-
ues to the average pH of the background plots and the original
pH of the treated plots, the low final average pH values would
indicate that the treatment only controlled the formation of acid
for a limited amount of time in the field (see Figure 5-1). This
statement can be supported by the fact that the average final
pH values listed above for EcoBond, UNR/MgO, and UNR/KP
range between pH 3.4 and pH 3.5. However, other external
factors such as oxidation of airborne particulates from traffic
or particulates transported over the wall during runoff events
could be affecting these results. Since the plots were too large
to be covered and weathering effects on the treatment was part
of the evaluation, the transported foreign particles that landed
on the wall could potentially reduce the pH on the treated high-
wall plots. However, if this were the case, the PARS average
pH would then be similar to that of the other technologies and
the pH from the background (see Figures 5-2, 5-3, and 5-4).
5.2.3 Residual Wash Metals Analysis
Mine wall sampling involved washing the highwall at
specified mine wall stations and analyzing the residual wash
(rinsate). The data acquired during sampling were used to de-
termine the effect of the treatment technologies on each plot.
The six constituents analyzed during the field demonstration
were Al, Cu, Fe, Mn, Zn, and Ni. As noted above, to allow for
weathering of the rock surface during the in situ testing, the
mine wall sample stations were not covered, thus the mine wall
stations were exposed not only to the weather but also to runoff
conditions and airborne particulate accumulation. The metals
loading results from each treated plot were compared graphi-
cally to the GSM/background plot and are shown in Figures 5-5
17
-------
Average pH from Highwall at GSM
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Figure 5-1. Average pH from highwall at GSM.
Residual Wash Sample Event
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Figure 5-2. pH results for July 22, 2002, residual wash sampling event.
18
-------
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Residual Wash Sample Event
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Figure 5-4. pH results for November 9, 2002, residual was sampling event.
19
-------
ALUMINUM
= = = =
SAMPLE PORT
Figure 5-5. Total metals loading results for Al from samples taken from the mine wall sampling stations.
through 5-10. The complete data set used to graph the mine
wall can be found in Appendix C.
The following includes the results and evaluation of each
technology as compared to the background plot (see Figures
5-5 through 5-10) and the raw sulfate data.
5.2.3.1 FARSPlot
• The average sulfate concentration for PARS was re-
duced 89% of the background concentration of 10,779
mg/L.
• On average, when comparing the PARS treatment to
the background, the PARS technology reduced the
total metals loading for all six metal constituents. The
metal loading for Al was reduced by 78% of the back-
ground loading, Cu by 91%, Fe by 89%, Mn by 88%,
Ni by 92%, and Zn by 93%.
5.2.3.2 EcoBond
• The average sulfate concentration for EcoBond was
31% less than the background concentrations of
10,779 mg/L.
On average, when comparing the treatment to the
background, the technology reduced the total metals
loading for four constituents (Al, Fe, Mn, and Ni);
however, the total loading for Cu and Zn was greater
than the total loading for the background plot. This
would indicate that the technology may provide lim-
ited inhibition of these metals, and additional chemical
treatment may be required to reduce the loading for Cu
and Zn. EcoBond reduced Al by 7%, Fe by 26%, Mn
by 55%, and Ni by 64%.
5.2.3.3 UNR/MgO
The average sulfate concentration for UNR/MgO
was reduced 21% of the background concentration of
10,779 mg/L.
On average, when comparing the treatment to the
background, the technology reduced the total metals
loading for five constituents. Iron was not reduced,
and Zn and Mn were reduced to the greatest degree.
The total metals loading reduction for Al was 21% that
of the background loading, Cu by 27%, Mn by 37%,
Ni by 34%, and Zn by 71%.
20
-------
COPPER
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SAMPLE PORT
Figure 5-6. Total metals loading results for Cu from samples taken from the mine wall sampling stations.
MANGANESE
SAMPLE PORT
Figure 5-7. Total metals loading results for Mn from samples taken from the mine wall sampling stations.
21
-------
IRON
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Figure 5-8. Total metals loading results for Fe from samples taken from the mine wall sampling stations.
NICKEL
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Figure 5-9. Total metals loading results for Ni from samples taken from the mine wall sampling stations.
22
-------
ZINC
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Figure 5-10. Total metals loading results for Zn from samples taken from the mine wall sampling stations.
5.2.3.4 UNR/KP
• The average sulfate concentration for UNR/KP was
reduced 34% of the background concentration for sul-
fate which was 10,779 mg/L.
• On average, when comparing the treatment to the
background, the technology reduced the total metals
loading for all six constituents. The total loading for
Al was reduced by 70% that of the background load-
ing, Cu by 87%, Fe by 64%, Mn by 65%, Ni by 78%,
and Zn by 86%.
5.2.4 Percent Reduction of Total Metals Compari-
son
Each mine wall station was evaluated to determine the
percent reduction in the cumulative metal loading per unit area
in the rinsate relative to the untreated control area. The con-
centration of each metal in the rinsates was converted to a mass
loading per unit area based on the volume of rinsate and the
surface area of the mine wall station. The percent reduction
was based on the difference between the average mass per unit
area of each metal generated from treated areas relative to the
mass per unit area of metal generated from the treated areas
relative to the mass per unit area of metal from the untreated
control station. Data were analyzed, and the percent reduction
of cumulative metals loading was calculated for each technol-
ogy. The results are provided in Table 5-2.
The PARS technology reduced all of the metals on the wall
by at least 75% and, in some cases, up to 91% compared to
the untreated plot (see Table 5-3). The PARS not only reduced
the total metals leaching from the highwall, but it physically
appeared to stabilize the wall rock.
The maximum percent reduction of total metals from the
PcoBond treated plot was less than 50%. The PcoBond was not
effective at reducing Zn and Cu on Plot C. This was apparent
from results listed in Table 5-3 that indicate a higher concentra-
tion of Cu and Zn from the treated plot than the background/
control plot. Higher concentrations could result from Plot C
having a higher percentage of Cu in the highwall host rock.
However, from the results, it would indicate that the treatment
does not effectively treat Cu and Zn. Additional testing would
need to be performed to determine why the select metals were
not chemically bound.
The UNR/MgO technology reduced Mn and Zn by more
than 75%; however, with the other metals, only a 50% or less
reduction was observed. The concentration for total Fe was
actually greater in the rinsate from the UNR/MgO treated plot
23
-------
Table 5-2. Summary of Water Injection Testing
Stage Interval
(feet bgs)
Average Pressure
(psig)
Description of the Injection Interval Using a
Lugeon Analysis
Permeability (cm/s)
Core Hole Number: GS-3 Horizontal (-5 degrees)
5- 17
17-35
39-70
22
28
70
Soft, broken material and fracture washout
Fractures filled with soft material that restricts
fracture flow, tight injection interval
No flow in this injection interval
7.8xlO-3tol.2xlO-4
7.9x10 6 to 1.6x10 5
2.0xlO-6
Core Hole Number: GS-4 Horizontal (-5 degrees)
5.5-20
9
Soft material washed out from fractures during
water injection testing
2.4-10 4 to 9.9x10 4
Core Hole Number: GS-3 (-45 degree hole)
14-29
29-70
18-33
15-34
Tight fractures, laminar flow, smooth surfaces on
cracks
Tight fractures, laminar flow, fractures filled with
some loose material
2.4x10 5 to 6.3x10 5
1. 1x10 5 to 9.6x10 6
Core Hole Number: GS-2H Horizontal (-5 degrees)
7-20
17
Material washed out of fractures; broken rock
1.7xlO-4to3.4xlO-4
Table 5-3. Percent Reduction of Total Metals from the Treated Technology Plots Compared to the Untreated Plot (Plot A)
Treated Plot vs. Background
% Reduction of Al
% Reduction of Cu
% Reduction of Fe
% Reduction of Mn
% Reduction of Ni
% Reduction of Zn
PARS
75
85
85
84
90
91
EcoBond
20
-211
24
49
48
-40
UNR/MgO
38
26
-16
82
50
75
UNR/KP
62
76
30
51
72
76
than from the untreated plot. This is apparent from the negative
value in Table 5-3.
For the UNR/KP treatment, Cu and Zn were reduced the
most at 76%, followed by Ni at a 72% reduction. Aluminum
was reduced by 62%, and Fe and Mn were reduced by 30% and
51%, respectively.
From the information obtained during the mine wall (re-
sidual wash) sampling, the technologies that were the most ef-
fective in reducing acid generation and leaching of metals from
the highwall area, listed in an increasing order of overall effec-
tiveness, were EcoBond, UNR/MgO, UNR/KP, and PARS.
5.3 HC Testing Results
The HC testing on the untreated GSM material was con-
ducted to establish baseline AMD potential data. Humidity cell
testing on the treated material was conducted to determine the
effectiveness of the various treatment technologies in prevent-
ing and/or minimizing AMD potential.
Each sample was saturated with the treatment and then
remained in the container until transported to MLI (see Figure
5-11). The timeline for treatment of the samples is as follows:
PARS (September 2001), EcoBond (October 2001), UNR/MgO
(November 2001), and UNR/KP (December 2001). Because
of its binding capabilities, the PARS sample had to be physi-
cally broken apart so that the coated sample could fit into the
HC testing container. Breaking the material coated with PARS
allowed some surfaces to be exposed, creating the potential for
oxidation to occur on those surfaces.
The original test duration was planned for 21 weeks but was
extended to 31 weeks and subsequently 41 weeks. Test suspen-
sion durations were 43 days after week 21 before reinitiation
and 131 days after week 31 before reinitiation. Humidity cell
test solids were left in the cells and frozen during test suspen-
24
-------
feed samples for sample characterization.
shown in Table 5-4.
These results are
Figure 5-11. Spray application of the material sent to MLI for HC
testing.
sions. Several of the technologies responded after the testing
had been reinitiated and are shown in the graphical presentation
of the data for each technology (see each technology subsection
for the relating figure).
Results from the HC testing for each of the treatment
technologies replicated very well. The GSM untreated sample
duplicated well but did exhibit some interim fluctuations that
are believed to be the cause of a sulfide mineral grain "nugget"
effect on the active surface of the rock. However, the treated
rock is coated with an inert layer inhibiting the "nugget" ef-
fect (Ref. 13). The results of the weekly and cumulative HC
testing are graphically shown in Figures 5-12 through 5-26. A
complete set of data and graphs from replicate HC samples can
be found in Appendix E.
5.3.7 ICP Metals Analysis Results for Feed Solids
At the time of the field application to the highwall, the
technology providers applied their technologies to prepared
samples. After the final application of the technologies to the
highwall, the samples were shipped to MLI for testing. An ICP
multielemental scan was performed on the treated and untreated
At MLI, a 1.2-kilogram (kg) composite sample from each
technology provider and the background plot were loaded in a
3.5-inch-ID, 9-inch-high HC and were leached weekly with ap-
proximately 500 mL of deionized water that was percolated in
the cells for 3 hours. The cells were allowed to saturate for an
additional hour and then drained. The effluent was analyzed for
pH, EH, EC, SO4, Fe3+ and Fe2+, acidity, and alkalinity at MCL
and submitted to an accredited EPA laboratory to be analyzed
for Al, Cu, Fe, Pb, Mn, Ni, and Zn.
The above metal analysis on the feed indicates that the
samples provided to the technology providers were similar to
the background samples. The variability in some of the metals
can be attributed to the analysis of the treatment chemicals and
coatings. For example, the EcoBond technology is phosphate
based. This is apparent from the phosphate values for the feed,
EcoBond, phosphorus (P) = 7,540 mg/kg, while for the other
technologies and background, P = 320 to 470 mg/kg.
5.3.2 GSM Untreated Rock
The data collected in the 41 weeks duration of HC testing
indicate that the untreated rock would produce acid in a natural
weathering and oxidizing environment. The final average pH
was 2.81, EH indicated strong oxidizing conditions and likely
bacterial oxidation, and EC was substantially higher than the
treated rock. Ferric and ferrous iron (Fe3+ and Fe2+) mobility
was high after week 15 with bacterial oxidation occurring after
week 21. Sulfate generation was high; however, in comparing
SO4 and acidity, it is indicated that most SO4 was not produced
by oxidation of sulfide minerals but rather from sulfide oxida-
tion of the SO4, and only 11.1% resulted from oxidation of
sulfide minerals (Ac/SO4 x 100). Figures 5-12, 5-13, and 5-14
provide a graphic representation of the biweekly HC tests and
cumulative mass data for the constituents available in the GSM
HC. Also, an immediate increase in SO4 and decreases in pH
were seen on the figures, indicating the effect of the sample
suspension on weeks 21 and 31.
5.3.3 PARS
The PARS treatment was replicated in the three HCs. There
were no spikes observed, and pH and EH increased slightly over
the duration of the testing period with an overall pH range of 4
to 4.5 (see Figures 5-15, 5-16, and 5-17). A decrease was ob-
served in EH, Fe, SO4, and acidity concentrations at the begin-
ning of the testing; however, over the 31 weeks, the SO4 gener-
ated was 2,400 mg/L, with approximately 26% of SO4 resulting
from sulfide oxidation. The mobility of Fe was substantial, but
the ratio of Fe3+ and Fe2+ was less than 1. Acidity was noted
with no alkalinity. The HC results from the PARS treatment is
shown graphically in the figures listed above. From the figures,
it is apparent that the PARS was not affected by the period of
suspension. In fact, upon reinitiation, the pH increased to 4.5.
Mass data for PARS treated tests show that significantly
less acidity and sulfate was produced in 41 weeks of kinetic
25
-------
Table 5-4. ICP Metals Analysis Results on Treated and Untreated Feed Samples for HC Testing
ICP Metals Analysis Results - Feed Solids
Treated and Untreated Highwall Samples
Metal, mg/kg
Ag
Al
As
Ba
Be
Bi
Ca
Cd
Co
Cr
Cu
Fe
K
Mg
Mn
Mo
Na
Ni
P
Pb
S total
Sb
Sr
Ti
V
w
Zn
GSM
0.5
51,000
15
50
1.5
<2
1,200
<0.5
16
105
54
36,700
29,300
7,100
105
5
14,500
34
370
22
28,600
10
189
1,600
63
<10
30
PARS
0.5
61,600
15
60
1.5
14
1,600
<0.5
18
143
72
43,500
39,800
8,900
145
7
14,300
52
440
16
33,500
5
228
2,100
84
<10
38
EcoBond
1.5
64,000
30
50
1.5
16
1,600
<0.5
22
114
94
56,500
62,000
9,500
170
7
17,600
67
7,540
34
47,600
20
218
2,100
100
<10
44
UNR/KP
1
53,100
15
40
1
<2
1,100
<0.5
17
110
71
38,800
36,500
9,100
180
5
13,800
52
470
18
33,100
10
177
1,800
86
<10
34
UNR/MgO
0.5
53,900
15
50
1.5
<2
1,200
<0.5
15
113
71
37,300
38,400
9,000
105
13
13,200
44
320
30
30,300
5
187
1,700
73
<10
28
Average
0.8
56,720
18
50
1.4
6
1,340
<0.5
17.6
117
72.4
42,560
41,200
8,720
141
7.4
14,680
49,8
1,828
24
34,620
10
199.8
1,860
81.2
<10
34.8
testing; however, the percentage of sulfate resulting from oxida-
tion of sulfide minerals was higher (23.5%). Alkalinity produc-
tion for PARS was low.
In summary, HC test data showed that the treatment mini-
mized acid production from the GSM material. Effluent pH
was generally above 4, which is the pH of the original treatment
solution. The redox potential increased slightly during the test
but remained about 300 millivolts (mV); EC values were low;
the iron mobility was minimal and the Fe3+:Fe2+ ratio was less
than 1 (0.3 average); and SO4 and acidity production was much
lower than the untreated material; however, the percentage of
SO4 produced by oxidation of sulndes was higher at 23%. This
generation of acid may be a result of weathering of the surfaces
exposed when the sample was broken to get the sample in the
test container. Essentially no alkalinity was consumed during
the test (0.01% of total).
5.3.4 EcoBond
The three HC tests for EcoBond had comparable replica-
tion. Slight spikes were noted in EH, EC, Fe, and SO4 with a
slight decrease in acidity and alkalinity after the 3-week rest
period (see Figures 5-18, 5-19, and 5-20). The overall results
show that the EcoBond technology prohibits acid production as
the pH decreased slightly at the beginning; however, final pH
readings were greater than 7. The original pH when the tech-
nology was spray applied to the highwall and the test sample
material was 11. Oxidation-reduction potential remained in the
normal range, and EC and Fe mobility was low after 11 weeks.
26
-------
WwMy Humility Cdl An.HyticAl Results
1357 911131517192123252729313335373941
Weeks
- -Suirate -*- Acidity -*-Akaiiniy|
BacknrcHiml - Ciiiiuilrftive Hunidity CeH Analytical Results
i
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1357 911131517192123252729313335373941
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|-*-pH -"-Sufale -*- Acidity -"^Akalirt^1
Figure 5-12. Weekly and cumulative HC analytical results for sample 1 from GSM background plot (Plot A).
27
-------
BiickgioiHKl (GSM-2? -Weekly HmnMity Cell AihTlytic.il Results
0 I • i • i"*~r* 1*1*1*1*1*1*1 *n~* 1*1* i"*'i *i«i*i*i«i*l 0
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Weeks
-*-Acidty -•
Figure 5-13. Weekly and cumulative HC analytical results for sample 2 from GSM background plot (Plot A).
28
-------
B.ickijiouniJ (GSM-31 - Weekly Humidity Cell Ar^ilythcjl Results
111
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-•-pH * Sutfate -*-Acidlt/ -"—Alkali nit1^
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A na(yt ic oJ Results
10-1- —r 3000
1357 9 11 13 15 1? 19 21 23 25 27 29 31 3335 37 3941
Weeks
pH -"--Sutafe -*-Acidity -*-Alkalinity
Figure 5-16. Weekly and cumulative HC analytical results for sample 2 from PARS plot (Plot B).
31
-------
Fmfuiyl Alcoliol Rwiun SfctiLiiT iFARS-JU-YM^kly HiiiimJriy Cell
A nafyttc ill Results
i n
w\
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1357 9 11 1315171921 2325272931 3335373941
Weeks
Figure 5-17. Weekly and cumulative HC analytical results for sample 3 from PARS plot (Plot B).
32
-------
F cohond iMTMl-Weekly Hmmlrty Cell An,ilyUc.il Resiihs
10 T H r 100
1357 9 11 13 15 17 19 21 2325 37 39 31 33 35 37 39 41
Weeks
•pH -*-Sulfete -*-Acidity —Alkalinity
Ecohond iMT2-t)-CiiiwiMive Humidity CeB Analytic*!
5000
4000
3000
1
i
i
2000 I
1000
1357 9 11 1315171921 2325272931 33 3S 37 39 41
Weeks
»-pH • Suirale -*- Acidity -*- Alkatnity |
Figure 5-18. Weekly and cumulative HC analytical results for sample 1 from EcoBond plot (Plot C).
33
-------
Feu hand lMT?-?i- Weekly Humility Cell AmilyTicrtl Results
10-l-f H- —r 400
320
240 *
0 -I—i—i—i—i—i T*T*T*T*rr*TrT*i-i • * i * > * i * . *T*T» I 0
1 3 5 7 9 11 13 15 17 19 21 2325 27 29 31 33 36 37 39 41
Weeks
•pH -*- Sufete -"-Acidity
ECOt»oiiil -Wteehry Huiimlty Cell
10
1357 911131517192123252729313336-373941
Weeks
|-»-pH -•-Suffate -r Acidity -*-Alkalinity I
Figure 5-19. Weekly and cumulative HC analytical results for sample 2 from EcoBond plot (Plot C).
34
-------
-2|-Weekly Humility Cell An.ilyTic.'il Results
100
1 3 5 7 911131517192123252729313336373941
Weeks
pH -*-Sulf3te -^Acidity -^-Alkalinity |
Ecobotid (MT2.3}-Cu imitative Humidity C «ll Analytical Results
10-i- —r 5000
4000
3000
2000
1000
1 3 5 T 911131517192123252729313335373941
Weeks
pH -*- Sulfate ^Acidity —Alkalinity
Figure 5-20. Weekly and cumulative HC analytical results for sample 3 from EcoBond plot (Plot C).
35
-------
The SO4 generation was high with approximately 15% resulting
from sulfide oxidation. Results from the HCs for EcoBond are
shown in Figures 5-18, 5-19, and 5-20.
Mass data for EcoBond treated tests show that significantly
less acidity and sulfate was produced in 41 weeks of kinetic
testing; however, the percentage of sulfate resulting from oxida-
tion of sulfide minerals was higher (15.5%). Alkalinity produc-
tion for EcoBond was 4,263 mg/L (21.2%). It was determined
that if the rate of alkalinity production versus acidity production
were to continue at a constant rate for EcoBond, data indicate
that neutralizing capacity would be consumed before available
acidity would be produced.
Humidity cell test data showed that the EcoBond treated
GSM material would not produce acid in a natural environment.
Effluent was above pH 7.4 during the test but did decrease from
pH 8.58 (week 1) to pH 7.47 (week 41). The original pH of the
treated material was 11. Redox potential varied slightly but re-
mained fairly constant during the test at approximately 200 mV.
The potential is typical for neutral pH systems exposed to air.
Electric conductivity values were high initially but decreased
to low levels the remainder of the test. Iron mobility was low;
however, the Fe3+:Fe2+ratio averaged about 3 after week 11; the
higher ratio may have resulted from the treatment chemistry.
Sulfate and acidity production was highest the first 5 weeks but
steadily decreased thereafter. The overall results indicate that
the EcoBond technology prohibited acid production under HC
testing conditions.
5.3.5 UNR/MgO
During the 41 weeks of kinetic testing, none of the avail-
able acidity was produced for the MgO treatments, indicating
that acid production for oxidation of sulfide minerals was es-
sentially prevented. The percentage of sulfate resulting from
sulfide oxidation was extremely low. The cumulative sulfate
generated averaged 3,075 mg/L and was beginning to rise in
weeks 37 through 41 (see Figures 5-21, 5-22, and 5-23). Alka-
linity production was also low (MgO at 1.27%), indicating that
the neutralizing capacity would be available over a long term,
especially since no acid was produced.
Effluent pH was above 6 throughout the test; however, the
pH tended to decrease with time, and the original pH of the
material was 12. The MgO technology was responsive to the
periods of testing suspension (i.e., the sulfate generation in-
creased and the pH responded by either increasing or decreas-
ing sufficiently). The EH decreased with time; however, it is
typical of an aerated system and did not reach strong oxidizing
conditions. Iron mobility was slight, yet the Fe3+:Fe2+ ratio was
fairly high (0.4 late in the test cycle). Acidity was detected only
late in the test cycle; however, alkalinity concentrations were
3 to 4 times higher during that period. Overall, under the HC
testing conditions, the MgO reduced the acid production and
leaching of metals from the highwall rock sample material.
5.3.6 UNR/KP
Comparable replication was noted with both the UNR/KP
and UNR/MgO cells. A decrease in pH and alkalinity and an
increase in EH, EC, and SO4 were observed at the beginning of
the testing (see Figures 5-24, 5-25, and 5-26). No mobility of
metals was noted with the exception of Mn from the potassium
permanganate. At the end of the 31 weeks, analytical results
showed a pH of greater than 6, EH in the normal range, and a
low EC. The mobility of Fe was low as was the ratio of Fe3+ and
Fe2+. The low SO4 generation (2,379 mg/L) indicates that the
SO4 is nonacidic. The UNR/KP technology was responsive to
the periods of suspension, and sulfate generation increased and
pH decreased upon reinitiation of the HC testing.
During the 41 weeks of kinetic testing, none of the avail-
able acidity was produced for the UNR/KP treatment, indicat-
ing that acid production for oxidation of sulfide minerals was
essentially prevented. The percentage of sulfate resulting
from sulfide oxidation was extremely low at less than 0.2%.
Alkalinity production was also low at 0.9%, indicating that the
neutralizing capacity would be available over a long term, es-
pecially since no acid was produced. From results shown in the
HC tests, GSM material treated with the UNR/KP technology
would not produce acid in a natural environment.
Effluent pH was above 6 throughout the test; however, the
pH tended to decrease with time, and the original pH of the
material was 12. The EH decreased with time, although this is
typical of an aerated system and did not reach strong oxidizing
conditions. Iron mobility was slight, yet the Fe3+:Fe2+ ratio was
fairly high (.4 late in the test cycle). The higher ratio may be
explained by the treatment chemistry (potassium permanganate
is an oxidant) and by the fact that Fe concentrations were ex-
tremely low. Acidity was detected only late in the test cycle;
however, alkalinity concentrations were 3 to 4 times higher
during that period.
5.3.7 Summary of the HC Testing Results
An overall summary of HC test data is provided in Table 5-
5. Oxidation-reduction potential, pH, and EC data are averages
for the week 41 HC test extracts only. All other data in the table
are an average of the triplicate tests conducted on each rinsate
water sample from the HC testing.
In summary, the data show that the untreated GSM high-
wall sample would produce acid in a natural weathering and
oxidizing environment. The final pH was 2.81; EH indicates
strong oxidizing conditions and likely bacterial oxidation;
EC indicates substantial metal mobility; and SO4 and acidity
production was high; however, alkalinity production was low
(0.02% of total). Of the SO4 produced, only 11.1% resulted
from oxidation of sulfide minerals (Ac-rSO4 x 100). The calcu-
lated alkalinity and acidity ratio (Alk 4- Ac) of the rinsate water
from the HC testing was less than 0.001.
It should be noted that the rock from the treated highwall
plots could potentially produce acid. This was apparent from
the solids data evaluated and presented in Appendix E, Table 5.
Results of the static test performed to predict the acid produc-
tion potential of the highwall rock (note: untreated and treated
samples were crushed, allowing untreated surface area to be
exposed) indicated that the difference between the acid neu-
tralization potential (ANP) and the acid generating potential
36
-------
M.itjl
Qxkte (MijQ-1 Weekly Hunidfly Cell AiMOTcAf Results
2
IB
o
I
^
1 3 5 7 911131517192123252729313335373941
Weeks
Suirate -^Acidity ^-Alkillnfly|
-1>-C(ninH.«we HiimWity Cell
10
1357 911131517192123252729313335373341
W«*ks
pH - -3Jfs*e -*-Acidifr -*- Alkalinity
Figure 5-21. Weekly and cumulative HC analytical results for sample 1 from UNR/MgO plot (Plot D).
37
-------
M.njiifiaiiin Oxjile 4MijO.?t -Weekly Hmiiilily C ell Aiuliyiic.ll Re$ul1i
1ft
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1357 911131517192123252729313335373941
Weeks
-*-pH - -Sulfate -*- Acidity — Alkalinity
4 DO
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^
B
160 =
f
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>i .r.iiiinlii1iveHLiiiiii1i1y T
Results
ic.il
10
1 3 5 7 9 11 131517 19 It 232527 2331 33 3537 3941
UtotJti
PH - -smrate
Figure 5-22. Weekly and cumulative HC analytical results for sample 2 from UNR/MgO plot (Plot D).
38
-------
4MyO-3t. VUeekfy HiiiniiliTy Cell AihityTicnil
10
1357 911131517192123252728313335373941
WMka
•pH -*-Sulfate -*-Acidity -+-A!kallnlty
htaijiiesiui in Oxide ffiTuO-3) . c muiiltflve HiiinhlRy Cell AiuiEytical
Resun«
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7 3 11 13 16 17 IS 21 23 25 27 29 31 33 35
Weeks
-»-pH Stlfate -*- Acidity -•— Alkahnity
JJU"-'
1
i
• 1 i riri .c
mtj
w
rt.
I * I * I * I U
37 39 41
Figure 5-23. Weekly and cumulative HC analytical results for sample 3 from UNR/MgO plot (Plot D).
39
-------
IKP- 1* - Weekly Himiiilily C •ell Analytic nl
Results
10
135? 911131517192123252729313335373941
•pH -*-Suirate -*-Acidity -*-Alkalinity
Peimai fc^atule(KP-1h Ciiinulvflv«Hiiiikhllty Cell
10
8
W $
i
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iu
2500
2000
1500
1000
1
f
1
500 u
1357 9 11 13 1517 1S 21 2325272931 3335373941
Weeks
*-SdTatB
Figure 5-24. Weekly and cumulative HC analytical results for sample 1 from UNR/KP plot (Plot E).
40
-------
Potassium
iH P.2>- Weekly Humidity C ell Aiiatyti&il
Results
1357 911131517192123252729313335373941
Weeks
|-«-pH - -Sulfste -^-Acidity -»-Alkalinity
Potassium PeiiTttiHj.iriJ!«
-------
i n -,
5 c -
a?
o.
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•} .
0; .
1(1 -
1U
8,
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Results
v*^J"^Uw"*~ • • * *•
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Weeks
-*-pii -Sulfste ---Acidity — Alkalinity |
PiU.iHuiiiin PenikliMj.iit^ile f^y\^.
^^
^^
^ ^. .
1 3 5 7911131517192123252729313335373941
Weeks
j-^pH - -SUfale -^Aeldi^ -*-AfcaHiH!y |
jflfi
JiCl
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e
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5
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Figure 5-26. Weekly and cumulative HC analytical results for sample 3 from UNR/KP plot (Plot E).
42
-------
Table 5-5. Summary HC Test Data for Untreated and Treated GSM Highwall Samples (data are an average of respective triplicate HC
tests)
Sample
GSM
PARS
EcoBond
UNR/KP
UNR/MgO
Treated
No
Yes
Yes
Yes
Yes
Week 41 Data
pH
2.81
4.52
7.22
6.50
6.57
Eh
515
307
227
275
274
EC
1.21
0.25
0.29
0.44
0.47
Generated, mg/kg
FE
263
199
2.6
2.2
1.3
so4
11,373
2,400
4,206
2,379
3.075
Acidity
1,263
562
651
7.8
2.8
Alkalinity
1.0
2.1
4,263
214
282
% of SCy
from S=
Oxidation
11.1
23.4
15.5
0.3
<0.1
Calculated
Alkalinity /Acidity
Ratio
<0.001
0.004
6.548
27.820
100,714
(AGP) were negative. Consequently, the potential exists for
all the samples (taken from each plot) to form acid. (The net
neutralization potential (NNP) was negative for all samples).
Using the same data comparisons, all treatment technolo-
gies were effective in decreasing potential for AMD. For Eco-
Bond, UNR/MgO, and URN/KP, pH was near neutral; EH was
typical for systems exposed to air; EC indicates minimal metal
mobility; Fe, SO4, and acidity production were lower than the
background sample and the MCL standards; alkalinity produc-
tion was higher than the background samples; and calculated
ratios for alkalinity and acidity were positive and substantially
greater than the background ratio, reflecting a nonacid produc-
ing environment after treatment of the samples.
The EARS technology has a pH of 4.52, which is the pH
of the acid-catalyzed solution sprayed as treatment on the high-
wall. The EH was typical of systems exposed to air. Electric
conductivity indicated minimal mobility; however, it did gener-
ate some iron and acidity (acid catalyzed material); however,
the SO4 production was low. To get the EARS sample into the
HC for testing, the sample had to be broke apart, which exposed
some untreated surface areas. This could account for some of
the higher mobility data values.
Potential for metals mobility increases when acid produc-
tion from oxidation of sulflde minerals occurs. A comparison
of metals mobility in the HC extract, on a concentration basis
from the various HC tests with respect to the National Primary
and Secondary Drinking Water Standards (MCLs and second-
ary MCLs), are provided in Table 5-6. Metal analytical results
are an average of the respective triplicate tests. All treatment
technologies were effective in decreasing the concentration and
mobility of metals from the GSM highwall sample material.
5.4 Technology Cost Analysis
For this demonstration project, each technology vendor
was subcontracted to apply their technology on the highwall at
GSM. All aspects of applying the technology were integrated
into the subcontract (i.e., materials, equipment, labor, technical
expertise, mobilization/travel, etc.). The cost included applying
each technology to the 50-ft by 50-ft test plot to provide optimal
coverage and maximum effectiveness of the technology.
The costs that are presented in Table 5-7 reflect the cost to
apply the technologies on the open-pit highwall at GSM for this
MWTP demonstration only. Application of these technologies
at a different location or mine would require the technology
vendor be contacted for an appropriate price quotation. From
the costs listed, EARS was the most cost-effective treatment
technology for this demonstration. However, under different
situations, the other technologies may be more cost effective.
The costs associated for each technology tested are de-
lineated in Table 5-7. Note that in Table 5-7, Intermountain
Polymers did not report any oversight charges. Also, UNR
combined the costs for its two technologies. For purpose of this
discussion, it is assumed that the cost of each UNR technology
was half of the total for each cost element except mobilization.
The mobilization cost will remain the same, no matter which
technology is applied.
The core cost elements for the four different technologies
demonstrated appear to be materials, installation, and oversight.
Mobilization and shipping costs appear to be distance driven
and not driven by special equipment or other needs. The core
cost elements are listed in Table 5-8. The percentage of the
total cost of each cost element, as well as the total unit cost per
square foot of area treated for each technology, is also listed.
As can be seen in Table 5-8, material costs contribute from
one-half to two-thirds of the total cost of using these technolo-
gies. Approximately one-third of the cost will be in installation,
and the remainder (from 15% to 25%) will be in oversight. Unit
costs will vary from $2.00 to $8.00 per square foot treated.
EcoBond's unit cost is more than double that of the other
vendors. This higher cost may be justified if EcoBond's treat-
ment lasts upwards of three times as long as the treatments of
the other vendors. However, life-cycle costs for each of these
technologies cannot be calculated at this time since determining
the effective longevity of the respective treatments was beyond
the scope of this study. As an example, the EARS technology
might be the most cost effective, all things considered, because
of its low application cost, and, as a polymer, it may stand up
well to yearly weathering cycles. The life of each technology
application is an area for future research.
The material costs are dependent on the market costs of
the products used in the technology formulations and the cost
43
-------
Table 5-6. Current National Drinking Water MCLs and SMCLs vs. HC Test Extract Composite Data (mg/L) Untreated and Treated GSM Highwall
Samples for Regulated Metals Analyzed
Extract Composite1
Wksl-9
Wks 10-21
Wks 22-31
Wks 32-41
GSM Untreated
Al
Cu
Fe
Pb
Mn
Zn
Ni
0.05-0.2
1.0
0.3
0.05
0.05
5.0
0.1
5.03
0.26
70.33
<0.025
10.46
1.20
0.89
0.86
<0.06
2.28
<0.015
1.30
0.17
0.10
4.73
0.14
29.67
<0.010
2.57
0.34
0.28
3.37
0.11
29.00
<0.010
2.03
0.26
0.24
PARS Treated
Al
Cu
Fe
Pb
Mn
Zn
Ni
0.05-0.2
1.0
0.3
0.05
0.05
5.0
0.1
0.56
<0.10
71.00
<0.020
2.77
1.17
0.24
0.079
<0.050
14.00
<0.010
0.93
0.18
0.076
<0.045
<0.050
3.13
<0.010
0.39
0.11
<0.017
<0.045
<0.050
3.73
<0.010
0.54
0.21
0.028
EcoBond Treated
Al
Cu
Fe
Pb
Mn
Zn
Ni
0.05-0.2
1.0
0.3
0.05
0.05
5.0
0.1
<0.090
<0.10
<0.10
<0.020
0.022
0.025
<0.020
<0.045
<0.050
<0.027
<0.010
0.011
<0.010
<0.010
<0.045
<0.050
<0.010
<0.010
<0.005
<0.010
<0.010
<0.045
<0.050
<0.015
<0.010
<0.005
<0.010
<0.010
UNR/KP Treated
Al
Cu
Fe
Pb
Mn
Zn
Ni
0.05-0.2
1.0
0.3
0.05
0.05
5.0
0.1
<0.045
<0.050
0.069
<0.010
0.013
<0.010
<0.010
<0.045
<0.050
<0.020
<0.010
0.026
<0.010
<0.010
<0.045
<0.050
<0.010
<0.010
0.068
<0.039
<0.010
<0.045
<0.050
<0.010
<0.010
0.180
<0.010
<0.010
UNR/MgO Treated
Al
Cu
Fe
Pb
Mn
Zn
Ni
0.05-0.2
1.0
0.3
0.05
0.05
5.0
0.1
<0.045
<0.050
<0.010
<0.010
<0.005
<0.010
<0.010
<0.045
<0.050
<0.010
<0.010
0.010
<0.010
<0.010
<0.045
<0.050
<0.010
<0.010
0.009
<0.017
<0.010
<0.045
<0.050
<0.010
<0.010
0.020
<0.010
<0.010
1 Metal concentrations are an average of the triplicate tests.
44
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Table 5-7. Cost Breakdown for Demonstrated Technologies
Technology
EARS
UNR/MgO
UNR/KP
EcoBond
Vendor
Intermountain Polymers
- Idaho Falls, ID
UNR - Reno, NV
UNR- Reno, NV
MT2 - Wheat Ridge, CO
Mobilize
$2,200
$3,780
$3,780
$5,723
Materials
$3,600
$1,890
$1,890
$10,250
Install
$1,695
$2,948
$2,948
$5,844
Shipping
$300
$630
$630
$1,000
Oversight
(1)
$2,394
$2,390
$2,910
Total
$7,795
$11,642
$11,642
$25,727
(1) Oversight assumed to be part of the installation cost.
Table 5-8. Core Cost Elements
Technology
EARS
UNR/MgO
UNR/KP
EcoBond
Material
$3,600
$3,780
$3,780
$10,250
% of Total
68%
41%
41%
54%
Install
$1,695
$2,948
$2,948
$5,884
% of Total
32%
33%
33%
31%
Oversight
(1)
$2,394
$2,394
$2,910
% of Total
0%
26%
26%
15%
Total
$5,295
$9,155
$9,122
$19,044
Unit Cost*
$2.12
$3.65
$3.65
$7.63
* Basis, 2,500 square feet
(1) Oversight assumed to be part of the installation cost.
to transport those products. Fluctuations in the market are de-
pendent on the conditions of the economy and the demand for
the products.
Another factor that affects the cost of applying these tech-
nologies includes the size of the plots. The cost to implement a
technology on a small test plot is usually higher than applying
the technology to a large area. Some of the reasons are noted
below.
• The cost for mobilization and demobilization of the
application equipment is the same whether it is a large
or small technology application. With a large applica-
tion, the cost is a small percentage of the total cost,
whereas for a small application (like this demonstra-
tion), the mobilization and demobilization cost could
be almost 10% of the total cost.
When purchasing the chemicals or other materials used
for the technology formulations, the cost of a small
quantity of material is usually higher than a larger or
bulk quantity purchase (i.e., the more product ordered,
the less the cost per container).
In this demonstration, the technology vendors applied
the technologies. However, in certain applications
or for large applications, it would be cost effective
to train company personnel to apply the technology,
which would reduce the equipment mobilization/de-
mobilization, labor, travel, and procurement costs,
thus reducing application cost.
45
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6. Quality Assurance/Quality Control
A QAPP was prepared specifically for the MWTP, Activity
III, Project 26 (Ref. 2). The QAPP met the requirements of an
applied research QAPP and was developed using the EPA docu-
ments QAPP Requirements for Applied Research Projects (Ref.
14) and Preparation Aids for the Development of Category II
Quality Assurance Project Plans (Ref. 10) as guides.
6.1 Project Background
Following is a summary of QA activities associated with
MWTP, Activity III, Project 26, Prevention of Acid Mine Drain-
age from Open-Pit Highwalls. This section summarizes the ac-
tivities used to determine the usability of the data generated for
this project. The intent of the project was to obtain performance
data on the ability of four technologies to prevent the generation
of AMD from the open-pit highwall at GSM.
To be able to evaluate the technologies, the project site was
characterized prior to the technology application. During the
site characterization activities, water injection test data, core
logs, and preapplication mine wall data were evaluated to de-
termine the usability of the data and provide additional baseline
data. The data were collected according to the schedule out-
lined in the approved project-specific QAPP.
The technologies that were applied to the highwall included
the four listed below.
• EcoBond developed by MT2 of Denver, Colorado
• UNR/MgO developed by UNR
• UNR/KP Passivation technology developed by Dupont
and presently owned by UNR
• PARS developed by Intermountain Polymers of Idaho
Falls, Idaho
To determine the effectiveness of the highwall treatment
technologies, two evaluation methods were used. The mine
wall sampling method was used in the field, and the HC testing
method was performed in the laboratory.
Background data were collected at each mine wall station
prior to technology emplacement in September 2001. Per-
formance data were collected during four planned sampling
events; the events were scheduled for April, July, September,
and November 2002. All field and laboratory data available for
the critical analyses were evaluated to determine the usability
of the data. The area of the mine wall stations, volume of re-
sidual mine wall wash, field pH, and total metals (Al, Cu, Fe,
Mn, Ni, and Zn) analyses were classified as critical analyses for
this project. The HC testing data were classified as a critical
analysis for the project in July 2002. A critical analysis is an
analysis that must be performed in order to determine if project
objectives were achieved.
6.2 Project Reviews
During the project, the evaluations performed were:
- internal field systems review at the demonstration site;
and
- external technical systems audit (TSA) at the demon-
stration site and the HKM Laboratory.
6.2.1 Internal Field Systems Review at the Dem-
onstration Site
A field systems review was performed on April 23 and 24,
2002, at GSM. The field systems review included a review of:
- personnel, facilities, and equipment;
- calibration of equipment; and
- sampling procedures.
The following findings were identified during the internal
audit.
• The QAPP referenced the removal of plastic sheets on
each sample station. No such plastic sheets existed.
• One sample in Plot E contained some headspace in
each of the two 500-mL sample bottles; the shortfall
in each subject bottle was estimated at 20 mL.
The following observations were identified during the in-
ternal audit.
46
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• There was difficulty in calibrating the pH meter on
day 2 as written instructions were not available. After
some time, the meter responded favorably (within the
0.1 accuracy requirement) when tested against known
pH buffer solutions.
• The physical conditions of the highwall sample sta-
tions were documented. Plots A, B, and C contained
significant sediment and fines with fewer visible frac-
tures while plots D and E were comprised of hard rock
surfaces that contributed to low fines but significant
surface fractures.
• Five sample stations were either partially damaged
beyond use or torn off by rock falling over the course
of the winter (one on each of the five plots), in which
case the station was not sampled. Two sample stations
were slightly damaged (one each on plots D and E) but
not beyond use for sampling.
The results of the audit were discussed with the Project
Manager. The generation of a QAPP addendum was recom-
mended; however, the addendum development was postponed
pending the outcome of the scheduled external TSA by EPA.
6.2.2 External Technical Systems Audit
In addition to the internal field systems review conducted
by MSB, an external TSA of the project and the HKM Labora-
tory was performed by Science Applications International Cor-
poration under subcontract to Neptune and Co. (subcontractor
to EPA) during the week of July 22, 2002.
6.2.2.1 Summary TSA Procedures, Findings, and Resul-
tant Actions
The field portion of the TSA consisted primarily of ob-
servations and questions during the activities. Observed field
activities included quarterly sampling, field measurements, and
sample delivery. The laboratory portion of the TSA consisted
of reviewing the April sampling event data package, viewing
the applicable laboratory activities, and interviews with HKM
Laboratory personnel. Five findings, seven observations, and
five additional technical comments were identified during the
audit.
The initial corrective action response to the TSA correc-
tive action comments was not considered sufficient by EPA;
therefore, a detailed data evaluation was undertaken by MSE to
determine the validity of the collected data (evaluated were the
April and July 2002 sampling events). The data evaluation was
submitted to EPA, as well as the data from the July 2002 sam-
pling event. EPA performed a statistical analysis on the July
2002 data to evaluate the success of the treatments and recom-
mended that the additional planned sample events (September
and November 2002) proceed (see Appendix D).
Summarized below are the TSA findings and approved cor-
rective actions taken as a result of the findings.
Finding 1 - The collection of samples from the highwall test
plots was performed in the April 2002 and September 2001
sampling events using two 500-mL sample containers instead
of one 1-liter container as specified in the project QAPP. Cor-
rective Action: After evaluation of the data, it was determined
that the results from the April 2002 sampling event could not be
included in the evaluation of the technologies.
Finding 2 - The QAPP required the establishment of five mine
wall sampling stations for each treated and nontreated plot.
Five sampling stations were originally established in each plot.
However, due to operating mine conditions and nature, several
of the sample ports were lost. Corrective Action: A statisti-
cal analysis was performed by EPA to determine the minimum
number of sampling stations required per area and if there was
a significant statistical difference between the treated and non-
treated data generated in July 2002. It was found that there was
some significant difference (see Appendix D). Also, MSE rees-
tablished all sampling stations that could be safely adhered,
and all reestablished stations were sampled (Ref. 15).
Finding 3 - The dimensions of the sample station areas were
a critical measurement and, during the sampling events, were
assumed to be 1 m by 1 m. This was not the case, and the
areas rinsed were not measured. The rinsed area is critical for
the metals loading calculation. Corrective Action: For each
sampling event, the mine wall sample ports were repaired, re-
marked, and measured to obtain the calculated loading values
as specified in the revised QAPP (Ref. 2).
Finding 4 - As required by the QAPP, the samples were re-
quired to be split and preserved in the laboratory on the same
day the samples were received. This was not performed for the
April 2002 sampling event. Corrective Action: All samples
were split, filtered (if necessary), and preserved appropriately
the same day the samples were delivered to the laboratory.
Finding 5 - According to the QAPP, four sampling events were
to be performed on a quarterly basis after the technologies had
been emplaced in January 2002. However, the final sampling
event was scheduled in October 2002, which would not allow
for a fourth sampling event. Corrective Action: As decided
during the TSA debriefing meeting, two sampling events would
be performed during September and November 2002. These
sampling events were reflected in the addendum to the QAPP,
and the data from the events were sent to EPA to determine the
usability of the data (see Appendix D).
The detailed data evaluation was performed to determine
the usability of data from each mine wall sampling event (Sep-
tember 2001, April 2002, July 2002, and August 2002) for
evaluating project objectives. After reviewing the project data
from the mine wall sampling, the following observations were
made.
• The mine wall sampling procedure is difficult to im-
plement and perform because of the instability of the
highwall and the safety aspects involved.
• The area measurements in the procedure assume a
two-dimensional surface while in many instances the
surface is three-dimensional, which can vary from one
location to another.
47
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• Measuring the natural effects on the treated and non-
treated stations is difficult at an operating mine be-
cause factors like airborne particulates and untreated
waste material placed on the bench above the test plots
place another variable into the evaluation of the tech-
nologies.
The above reasons indicate that even if all of the mine wall
samples were collected perfectly, the data may not provide all
the quantitative information required to fully evaluate the per-
formance of the technologies. Since these observations were
noted, all project data were forwarded to the EPA National Risk
Management Research Laboratory for statistical analysis, and
the HC data were elevated in importance and became a critical
parameter.
6.3 Data Validation
An analytical evaluation of all data was performed to de-
termine the usability of the data that were generated by HKM
Laboratory for the project. Laboratory data validation was per-
formed using USEPA Contract Laboratory Program National
Functional Guidelines for Inorganics Data Review (Ref. 17)
as a guide. The QC criteria outlined in the QAPP, which are
summarized in Table 6-1, were also used to identify outlier data
and to determine the usability of the data for each analysis. A
summary of QC checked results for the critical dissolved metals
and pH analyses of all the usable data are presented in Table
6-2. All data requiring flags are summarized in Table 6-3.
6.4 Program Evaluation
In addition to the data validation, a program evaluation was
performed. Program evaluations included an examination of
data generated during the project to determine that:
- all samples, including field QC samples, were col-
lected, sent to the appropriate laboratory for analysis,
and were analyzed and reported by the laboratory for
the appropriate analyses; and
- all field blanks contain no significant contamination.
Field duplicates are typically included in the program
evaluation; however, the nature of the sampling technique pre-
cluded the collection of field duplicates.
While certain analytes were detected in field blank samples,
the sample concentrations were at least 10 times the contamina-
tion concentration; therefore, no data were flagged for out-of-
control field blanks.
6.5 HC Data Evaluation
The data collected by MLI in Sparks, Nevada, were also re-
viewed for usability. The HC data were elevated in importance
due to the difficulties associated with the data collected in the
field. MLI submitted its report including raw data. MSB re-
quested information on QC checks to complete a thorough data
review. MLI responded, and MSB completed the data review.
MLI performed analyses on the HC rinse waters for:
-pH;
-EH;
- conductivity;
- total Fe;
- Fe speciation;
-S04;
Table 6-1. Data Quality Indicator Objectives
Parameter
Area of Mine
Wall Station
Volume of
Residual Wash
pH
Al
Cu
Fe
Mn
Ni
Zn
Matrix
N/A
Aqueous
Aqueous
Aqueous
Aqueous
Aqueous
Aqueous
Aqueous
Aqueous
Unit
m2
mL
sue
Hg/L
Hg/L
Hg/L
Hg/L
Hg/L
Hg/L
Minimum Detection Limit
(Instrument Detection Limit)
N/A
25 mL
1.0
50(18.9)
50(1.3)
50(7)
50(1.3)
50(10.5)
50 (3.5)
Precisiona
O.lm2"
N/A
±0.1"
<20%
<20%
<20%
<20%
<20%
<20%
Accuracy15
N/A
±25 mL
±0.1"
75-125%
75-125$
75-125%
75-125%
75-125%
75-125%
Completeness0
95%
95%
95%
95%
95%
95%
95%
95%
95%
a Relative percent difference (RPD) of analytical duplicates, unless otherwise indicated.
b Percent recovery of matrix spike, unless otherwise indicated.
c Based on the number of valid measurements compared to the total number of samples.
d Absolute difference of sonsecutive measurements.
e SU - standard unit.
48
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Table 6-2. Summary of QC Checks for Critical Total Metals Analy-
sis
Analysis
Al
Cu
Fe
Mn
Ni
Zn
Analysis
Al
Cu
Fe
Mn
Ni
Zn
Mean RPD for Sample
Duplicates
13.0
21.8
29.2
1.2
9.6
7.8
Mean Percent Recovery
for Matrix Spikes
89. la
94.4
NAa
101.9
88.7
82.4
Range of RPD for
Sample Duplicates
4.6-21.9
1.5-44.9
0.6-70.8
0.2-2.6
1.2-18.7
1.7-12.2
Range of Percent
Recovery for Matrix
Sprikes
89.1-89.1
81.1-107.6
NAa
96-107.8
78.3-95.1
65.1-92
32 None of the samples for Fe and only one sample for Al were
evaluated for matrix spike recovery because the sample concentra-
tion exceeded the spike concentration by a factor of 4 or more.
- acidity; and
- alkalinity.
The Western Environmental Testing Laboratory performed
metals analyses on the HC rinsates for metals analysis (Al, Cu,
Fe, Pb, Mn, Zn, and Ni).
Solid samples were analyzed by SVL Analytical, Inc., for:
- total sulfur;
- nonextractable sulfur;
- pyritic sulfur;
- SO4 as sulfur;
- paste pH;
-AGP;
- ANP; and
- calculated ANP/AGP ratio.
ALS Chemex Labs, Inc., performed the following analyses
on the solid samples.
The HCs were monitored for a total of 41 weeks with inter-
mittent freezing of samples. All data reviewed were validated
using the methods described above for the other field and labo-
ratory data associated with the project. All data were deemed
usable for supporting project objectives. MLI requested reanal-
ysis for Ni on one sample set. Some samples required dilutions,
and reporting limits were adjusted accordingly.
6.6 Recommendations and Conclusions
In the future, to avoid the identified difficulties that were
associated with this project, the following recommendations are
made.
• The mine wall sampling procedure should be reviewed
with all personnel, and a simulated sample station
should be established to determine and define the
problems that may occur during sampling.
• Site-specific sample data sheets should be developed
for this project to delineate mine wall station areas,
measurements, pH, and other measured parameters.
Logbooks should be organized numerically with de-
scriptions of all changes that occurred between sam-
pling events and should denote all critical measure-
ments.
• Quality and safety requirements need to be reviewed
and communicated thoroughly to all project person-
nel. The hazardous nature of working and sampling
the highwall using the required mine wall sampling
procedure needs to be understood by participants in
the demonstration.
• Because the mine wall sampling procedure is not a
standardized procedure with which the laboratory and
other sampling personnel are familiar, all sampling
procedures, including the mine wall sampling pro-
cedure, should be reviewed by laboratory and field
personnel. Alternatively, applicable sections of the
QAPP could be attached to the chain-of-custody in the
future.
• The HC tests should be used for quantitative informa-
tion regarding the performance of the technologies
with respect to preventing the formation of AMD.
However, these tests do not fully replicate field condi-
tions.
49
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Table 6-3. Summary of Flagged Data for Activity III, Project 26
Date of
Collection
9/19/02
9/19/02
Sample ID
MWA-509192002
MWA-309192002
MWA-209192002
MWB-109192002
MWB-209192002
MWB-309192002
MWB-509192002
MWC-209192002
MWC -309192002
MWC -409192002
MWD -409192002
MWE-109192002
MWE-209192002
MWE-309192002
MWE-409192002
MWE-509192002
MWA-509192002
MWA-309192002
MWA-209192002
MWB-109192002
MWB-209192002
MWB-309192002
MWB-509192002
MWC-209192002
MWC -309192002
MWC -409192002
MWD -409192002
MWE-109192002
MWE-209192002
MWE-309192002
MWE-409192002
MWE-509192002
Analysis
Total Al
Total Cu
Total Fe
Total Zn
Dissolved Zn
Quality Criteria
Analytical duplicate
(<20&% RPD)
Matrix spike (75-
125% recovery)
Actual
21. 9% RPD
44.9%
70.8% RPD
65.1
68.6
Flag
J
J
J
J
Comment
The analytical dupli-
cate was greated than
5 times the contract
required detection limit
and out of control for
Al, Cu, and Fe. The
associated samples
should be flagged "J"
as estimated.
The matrix spike was
out of control for total
and dissolved Zn. The
associated samples
should be flagged "J"
as estimated.
Data Qualifier Definition:
J - The concentrations are estimated.
50
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7. Conclusions
For the MWTP, Activity III, Project 26, Prevention of AMD
Generation form Open-Pit Highwalls demonstration project,
four treatment technologies were applied and tested in the field
at the GSM. The primary objectives of this project were to
determine the impact of the treated area for each technology
on the total metal loading per unit area and pH of the rinsates
compared to the rinsates from the untreated area. The objec-
tives were not to compare the four passivation technologies
against one another. Achievement of the objectives was not
only evaluated using field mine wall sampling, but HC testing
was performed on treated samples from the highwall also.
In summary, the data from the untreated GSM highwall for
both field monitoring and HC laboratory testing show that the
highwall would produce acid in a natural weathering and oxi-
dizing environment. The same background data from the un-
treated GSM plot were used for comparison of all the treatment
technologies to determine if the technologies were effective in
decreasing potential for AMD.
For the reduction of acid generation, all test results, from
both the field and the laboratory, indicate that the treatment
technologies demonstrated at GSM (to some degree) controlled
the acid generation potential of a mine highwall. Each of the
technologies created an inert layer or coating on the sulfide ma-
terial, preventing contact with atmospheric oxygen/water during
the weathering of the sulfide highwall rock and thus preventing
sulfuric acid generation and metals mobilization.
For the field mine wall sampling, EcoBond, UNR/MgO,
and UNR/KP plots, the recorded pHs were as low as the pH of
the background plot where the pH was less than 4, and the range
of percent metals reduction ranged from 82% to a -211%. The
pH recorded for the PARS technology was steady at 4 to 4.5 for
the full demonstration, and the percent metals reduction ranged
between 75% to 91%, compared to the background results.
In the field, the FARS material also provided visible physical
stabilization of the highwall. Mine wall movement did cause
the highwall to become unstable, and it resulted in the loss of
several sample ports, which could have potentially affected the
overall results. For future research on open-pit highwalls, it is
recommended that a surplus of sample ports be established in
case some ports are damaged.
However, when compared to the background plot for the
HC testing, the EcoBond technology had a pH that was neutral;
the EC was typical for systems exposed to air and indicated
minimal metal mobility; Fe, SO4, and acidity production was
higher; and calculated ratios were substantially greater than
regulatory guidelines. For the two UNR technologies, the pH
was slightly greater than 6; EC was typical for systems exposed
to air and indicated minimal metal mobility; Fe, SO4, and acidity
production was higher; and calculated ratios were substantially
greater than regulatory guidelines. For the FARS technology,
the pH ranged between 4 and 5, which is the pH of the acid
catalyzed solution used to coat the surface of the material. The
EC was typical of a system exposed to air, and some metals
were mobilized. In addition, Fe, SO4, and acidity production
wee higher than for the other three technologies but not close to
background levels.
The mass data generated from the HC testing at MLI dem-
onstrated that larger quantities of metals analyzed were mobi-
lized from the untreated/background plot and the FARS treated
sample than from the other three treated feeds. Essentially,
no metals were mobilized from EcoBond, UNR/MgO, and
UNR/KP treated feeds. The lack of metals mobility indicates
that three treatment technologies prevented acid production.
However, the dosages used to treat the samples were high and
allowed for the sample surfaces to be fully coated and treated
for an extended period of time.
• Upon completion of the demonstration, the following
issues remain for possible future investigation. These
issues include:
determining the effect of the airborne particulat
and runoff on field sampling results;
determining the effect of allowing all HC samples
that were saturated during the application to sit
51
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until testing was initiated and also determining
what effect was there on the samples that were al
lowed to sit during the time that HC testing was
suspended; and
determining if the PARS technology perfor-
mance was altered when the sample for testing had
to be broken to fit into the HC sampling equipment,
thus exposing untreated surfaces to the induced
weathering processes
These issues still remain unresolved; however, overall, the
technologies reduced the potential for acid production on the
GSM highwall material, whether in the field or in the labora-
tory. After evaluating the data generated during the demonstra-
tion, these technologies that have the potential to passivate or
stabilize open-pit highwalls, could limit the environmental im-
pact from mining and processed ore at abandoned mines, active
mines, and newly developed ore reserves.
Each technology inhibits AMD differently, dependent
upon chemistry of the treatment formulation, sulfide content,
morphology, pH of the waste material, weather conditions, and
amount of water draining from the highwall. By reducing the
potential for AMD generation from a mine highwall, reclama-
tion costs for mining companies and regulatory agencies could
be minimized. However, the cost for implementing these tech-
nologies may be prohibitively expensive, and a tradeoff could
be made relative to capturing and treating AMD.
52
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8. References
1. MSB Technology Applications, Inc., Work Plan - Preven-
tion of Acid Mine Drainage Generation from Open-Pit
Highwalls, No. MWTP-181, November 2000.
2. MSB Technology Applications, Inc., Quality Assurance
Project Plan - Prevention of Acid Mine Drainage Gen-
eration from Open-Pit Highwalls, No. MWTP-197R1,
December 2002.
3. Placer Dome Inc., website at http://www.placerdome.com.
4. Heiser, J.H. and L. W. Milian, Brookhaven National Labora-
tory, Laboratory Evaluation of Performance and Durabil-
ity of Polymer Grouts for Subsurface Hydraulic/Diffusion
Barriers, No. BNL-61292, May 1994.
5. U.S. Environmental Protection Agency Superfund Innova-
tive Technology Evaluation, Demonstration Bulletin for
the Environbond™ Process, Rocky Mountain Remediation
Services, EPA/540/MR-99/502, July 1999.
6. Eger, P. and A. Antonson, Use of Microencapsulation to
Prevent Acid Rock Drainage, report to MSB Technology
Applications, Minnesota Department of Natural Resources,
St. Paul, MN, pg. 7-9, September 30, 2002.
7. De Vries, Nadine H.C., Process for Treating Iron-Contain-
ing Sulfide Rocks and Ores, U.S. Patent No. 5,587,001.
8. Marshall, G.P., J.S. Thompson, and R.E. Jenkins, "New
Technology for the Prevention of Acid Rock Drainage,"
Proceedings of the Randol Gold and Silver Forum, p. 203,
1998.
9. Misra, M. and D. Van Zyl, Passivation of Acid Generat-
ing Mining Waste, proposal submitted to the EPA MWTP,
2000.
10. U.S. Environmental Protection Agency, Preparation Aids
for the Development of Category II Quality Assurance
Project Plans, EPA/6008/8-91/005, Washington D.C., Feb-
ruary 1991.
11. Morin, K.A., Environmental Geochemistry of Mine site
Drainage; Appendix D, Mine-wall Methods, January 1996.
12. American Society for Testing and Materials, ASTM Des-
ignation: D5744-96 Standard Test Method for Accelerated
Weathering of Solid Material Using a Modified Humidity
Cell, ASTM, West Conshohocken, PA, 13p, 1996.
13. McClelland Laboratories, Inc., Update on Humidity Cell
Testing, Sparks, Nevada, 2003.
14. U.S. Environmental Protection Agency's National Risk
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16. Metals Treatment Technologies, LLC (MT2), Golden Sun-
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10, 2002.
17. Metals Treatment Technologies, LLC (MT2), Newsletter,
Spring/Summer 03, Edition 05.
53
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9. Bibliography
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54
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