### EP A-600/R-06/008

F ebr uar y 2006 

# Characterization of Mercury-Enriched Coal Combustion Residues from Electric Utilities Using Enhanced Sorbent s for Mercury Control

### EP A-600/R-06/008

F ebr uar y 2006


# Characterization of Mercury-Enriched Coal Combustion Residues from Electric Utilities Using Enhanced Sorbent s for Mercury Control by F

. Sanchez 1 

### , R. Keene y 2 

### , D
. K osson 1 

### , and R. Delapp 1

1 

### V

anderbilt Univ ersity 2 

### ARCADIS G&M, Inc. Depar tment of Civil and En vironmental Engineer ing 4915 Prospectus Dr iv e , Suite F Nashville , TN 37235 Durham, NC 27713
Contr act No
. EP-C-04-023, W o r k Assignment 1-31
EP A Project Off icer : Ms
. Susan Thor neloe Off ice of Research and De v elopment (ORD) National Risk Management Research Labor ator y (NRMRL) Air P ollution Pre v ention and Control Division (APPCD) Research T r iangle P a r k, Nor th Carolina.

U
. S
. En vironmental Protection Agency Off ice of Research and De v elopment W ashingtion, DC 20460Characterization of Coal Combustion Residues



# Abstract
This report evaluates changes that may occur to coal-fired power plant air pollution control residues from the use of activated carbon and other enhanced sorbents for reducing air emissions of mercury and evaluates the poten
tial for captured pollutants leaching during the disposal or use of these residues. Leaching of mercury , arsenic, and selenium during land disposal or beneficial use of coal combustion residues (CCRs) is the environmental impact pathway evaluated in this report. Coal combustion residues refer collectively to fly ash and other air pollution control solid residues generated during the combustion of coal collected through the associated air pollution control system. This research is part of an on-going ef fort by U.S. Environmental Protection Agency (EPA) to use a holistic approach to account for the fate of mercury and other metals in coal throughout the lifecycle stages of CCR management. The specific objectives of the research reported here are to: 1. Evaluate the potential for leaching to groundwater of mercury, arsenic, and selenium removed from coalfired power plant air emissions by air pollution control technology and, as a result, are contained in CCRs; 2. Provide the foundation for assessing the impact of enhanced mercury and multi-pollutant control technol
ogy on leaching of mercury and other constituents of potential concern from CCRs during the lifecycle of CCR management, including storage, beneficial use, and disposal; and 3. Perform these assessments using the most appropriate evaluation methods currently available. Air pollution control residues were obtained from coal combustion electric utility facilities with a representative range of facility configurations (including air pollution controls) and coal types combusted. Each of the residues sampled has been analyzed for selected physical properties, and for total content and leaching characteristics. Results of laboratory leaching tests were used to develop estimates of constituent release under field manage
ment scenarios. Laboratory leaching test results also were compared to field observations of leaching. This report focuses on facilities that use injected sorbents for mercury control. It includes four facilities with activated carbon injection (ACI) and two facilities using brominated ACI. Fly ash has been obtained from each facility with and without operation of the sorbent injection technology for mercury control. Each fly ash sampled was evaluated in the laboratory for leaching as a function of pH and liquid-to-solid ratio. Mercury , arsenic and selenium were the primary constituents of interest; results for these elements are presented here.

iiCharacterization of Coal Combustion Residues



# Foreword

The U
. S
. En vironmental Protection Agency (EP A) is charged b y Cong ress with protecting the Nation’ s land, air , and w ater resources
. Under a mandate of national en vironmental la ws , the Agency str iv es to f o r m ulate and implement actions leading to a compatib le balance betw een human activities and the ability of natural systems to suppor t and n u r ture lif e . T o meet this mandate , EP A ’ s research prog ram is pro viding data and technical suppor t f or solving en vironmental prob lems today and b uilding a science kno wledge base necessar y to manage our ecological resources wisely , understand ho w pollutants aff ect our health, and pre v ent or reduce en vironmental r isks in the future
. The National Risk Management Research Labor ator y (NRMRL) is the Agency’ s center f o r in v estigation of technological and management approaches f or pre v enting and reducing r isks from pollution that threaten human health and the en vironment. The f ocus of the Laborator y’ s research prog ram is on methods and their cost-eff ectiv eness f or pre v ention and control of pollution to air , land, w ater , and subsurf ace resources; protection of w ater quality in pub lic w ater systems; remediation of contaminated sites , sediments and g round w ater ; pre v ention and control of indoor air pollution; and restor ation of ecosystems
. NRMRL collaborates with both pub lic and pr iv ate sector par tners to f oster technologies that reduce the cost of compliance and to anticipate emerging prob lems
. NRMRL ’ s research pro vides solutions to en vironmental prob lems b y : de v eloping and promoting technologies that protect and impro v e the en vironment; adv ancing scientif ic and engineer ing inf or mation to suppor t regulator y and policy decisions; and pro viding the technical suppor t and inf or mation transf er to ensure implementation of en vironmental regulations and strategies at the national, state , and community lev els
. This pub lication has been produced as par t of the Labor ator y’ s str ategic long-ter m research plan. It is pub lished and made a v ailab le b y EP A ’ s Off ice of Research and De v elopment to assist the user comm unity and to link researchers with their clients
.
Sally Gutierrez, Director National Risk Management Research Labor ator y

iiiCharacterization of Coal Combustion Residues



# E P A Review Notice

The U.S. Environmental Protection Agency through its Of fice of Research and Development funded and man
aged the research described here under Contract EP-C-04-023 to ARCADIS Geraghty & MIller , Inc. It has been subjected to Agency review and has been approved for publication as an EP A

document. Mention of trade names or commercial products does not constitute endorsement or recommendation for use. This document is available to the public through the National T echnical Information Service, Springfield, V i r ginia 22161.

ivCharacterization of Coal Combustion Residues



# T

able of Content s
Section Page Abstract
....................................................................................................................... ...................................... ii Foreword
....................................................................................................................... ................................... iii EP A

Review Notice
.............................................................................................................. ........................... iv List of Figures
................................................................................................................ ................................. vii List of T ables
................................................................................................................. ................................ viii Glossary of T erms .............................................................................................................. .............................. ix Acknowledgments
................................................................................................................ ........................... xi Executive Summary
.............................................................................................................. .......................... xii 1 Introduction
.................................................................................................................. .............................. 1 1.1 Regulatory Context
.......................................................................................................... .................... 2 1.1.1 W aste Management ......................................................................................................... ............ 2 1.1.2 Air Pollution Control
.................................................................................................... .............. 3 1.2 Configurations of U.S. Coal Fired Power Plants and Multi-pollutant Control T echnologies
............. 3 1.2.1 Current Air Pollution Control T echnologies
............................................................................... 5 1.2.2 Enhancement of Controls for Mercury Removal: Sorbent Injection
.......................................... 6 1.2.3 Mercury Control by Conventional P AC Injection
...................................................................... 8 1.2.4 Mercury Control by Halogenated P AC Injection
....................................................................... 8 1.3 Coal Combustion Residues
.................................................................................................... .............. 9 1.4 Residue Management Practices
................................................................................................ ........... 9 1.4.1 Beneficial Use
........................................................................................................... ............... 10 1.4.2 Land Disposal
............................................................................................................ ............... 1 1 1.5 Leaching Protocol
........................................................................................................... ................... 1 1 2 Materials and Methods
......................................................................................................... .................... 15 2.1 CCR Materials for Evaluation
................................................................................................ ........... 15 2.1.1 Reference Fly Ash
........................................................................................................ ............ 15 2.1.2 Facilities Using Injection of S tandard Activated Carbon
......................................................... 15 2.1.2.1 Brayton Point
.......................................................................................................... ...... 15 2.1.2.2 Pleasant Prairie
....................................................................................................... ...... 19 2.1.2.3 Salem Harbor
........................................................................................................... ..... 20 2.1.2.4 Facility C
............................................................................................................. ......... 20 2.1.3 Facilities Using Injection of Brominated Activated Carbon
..................................................... 20 2.1.3.1 S t. Clair
.............................................................................................................. ........... 20 2.1.3.2 Facility L
............................................................................................................. ......... 20 2.2 Leaching Assessment Protocols
............................................................................................... .......... 21 2.2.1 Alkalinity , Solubility and Release as a Function of pH (SR002.1)
.......................................... 21 2.2.2 Solubility and Release as a Function of LS Ratio (SR003.1)
................................................... 2 1 2.3 Analytical Methods
.......................................................................................................... ................. 21 2.3.1 Surface Area and Pore Size Distribution
.................................................................................. 21 2.3.2 pH and Conductivity
...................................................................................................... ........... 22 2.3.3 Moisture Content
......................................................................................................... ............. 22 2.3.4 Carbon Content: Organic Carbon/Elemental Carbon Analyzer
................................................ 22 vCharacterization of Coal Combustion Residues 

# Table of Contents (concluded) Section Page 2.3.5 Mercury (CV AA, Method 3052, and Method 7473)
................................................................ 22 2.3.6 Other Metals (ICP-MS, Method 3052 and Method 6020)
........................................................ 22 2.3.6.1 ICP-MS Analysis at V anderbilt
..................................................................................... 23 2.3.6.2 Severn T rent Laboratories, Inc. (STL)
.......................................................................... 23 2.3.7 X-Ray Fluorescence (XRF)
................................................................................................. ..... 23 2.3.8 MDL and ML for Analytical Results
........................................................................................ 23 2.4 Quality Assurance V alidation
................................................................................................ ............ 24 2.4.1 Homogenization of Individual CCR Samples and Aliquots for Analyses
................................ 24 2.4.2 Leaching T est Methods and Analytical QA/QC
....................................................................... 24 2.4.3 Laboratory Mass Balance V erification for Leaching T est Methods
......................................... 24 2.4.4 Improving QA/QC Ef ficiency
................................................................................................ .. 27 2.5 Interpretation and Presentation of Laboratory Leaching Data
.......................................................... 27 2.6 Long-T erm Release Assessment
................................................................................................ ........ 29 3 Results and Discussion
........................................................................................................ ..................... 35 3.1 Leaching Characteristics from Field Observations of CCR Landfills and Impoundments
............... 35 3.2 Quality Assurance for Laboratory Leaching T ests ............................................................................ 3 9 3.2.1 Mass Balance using EP A

Reference Fly Ash
............................................................................ 39 3.2.2 Analytical Quality Control/Quality Assurance
......................................................................... 39 3.3 Laboratory T est Results
..................................................................................................... ................ 40 3.1.1 Mercury Results
........................................................................................................... ............. 43 3.3.2 Arsenic Results
........................................................................................................... .............. 45 3.3.3 Selenium Results
.......................................................................................................... ............ 47 3.4 Long-T erm Release Assessment
................................................................................................ ........ 48 3.3.4 Long-T erm Release Estimates for Mercury
.............................................................................. 49 3.3.4 Long-T erm Release Estimates for Arsenic
............................................................................... 50 3.3.4 Long-term Release Estimates for Selenium
............................................................................. 50 4 Conclusions and Recommendations
............................................................................................... ......... 55 4.1 Assessment of CCRs W ithout and W ith Activated Carbon Injection
................................................ 55 4.2 Implementation of Leaching T est Methods
..................................................................................... .. 56 5 References
.................................................................................................................... ............................ 57 Appendix A U.S. EP A

Science Advisory Board Consultation Summary
....................................................... 59 Appendix B DOE NETL Full-Scale T est Site Flow Diagrams
....................................................................... 73 Appendix C Quality Assurance Project Plan
...................................................................................... ............ 79 Appendix D Brayton Point Fly Ashes
............................................................................................. ............. 1 1 6 Appendix E Pleasant Prairie Fly Ashes
.......................................................................................... .............. 131 Appendix F Salem Harbor Fly Ashes
.............................................................................................. ............. 146

viCharacterization of Coal Combustion Residues


# List of Figures Figure Page 1 Coal-Fired Boiler with Sorbent Injection and Spray Cooling
.................................................................... 7 2 Flow Diagram for Power Plant with a Hot ESP , Carbon Injection, and a COHP AC
................................. 7 3 Life-Cycle Evaluation of Coal Combustion Residues
............................................................................. .. 9 4 Uses of CCRs Based on 2003 Industry S tatistics
................................................................................ ..... 10 5 Mixing Fly Ash Prior to Obtaining Aliquots for Laboratory Analyses
.................................................... 24 6 Flow Diagram for Mass Balance and Quality Control on Laboratory Leaching Procedures
.................. 26 7 Example of Extract Concentrations as a Function of pH from SR002.1
................................................. 28 8 Leachate pH Distribution: Scenario of Disposal in a Combustion W aste Landfill
.................................. 30 9 LS Ratio Distribution: Scenario of Disposal in a Combustion W aste Landfill
........................................ 31 10 Example of V ariability of Hg Concentrations as a Function of pH from SR002.1
.................................. 31 1 1 Example of Regression Fits and Corresponding Equations for Solubility as a Function of pH
.............. 32 12 Example of Cumulative Probability Distribution for Release of Selenium from Brayton Point CCR
.... 32 13 Example of Comparison of 100 Yr Cumulative Release Estimates for Arsenic
...................................... 3 3 14 Range of pH Observed in Field Leachate at Landfills and Impoundments Used for Disposal of CCRs
............................................................................................................... ...................... 36 15 Arsenic Concentrations Observed in Field Leachate at Landfills and Impoundments Used for Disposal of CCRs
............................................................................................................... ...................... 37 16 Selenium Concentrations Observed in Field Leachate at Landfills and Impoundments Used or Disposal of CCRs
............................................................................................................ .................... 38 17 S T L V ersus V anderbilt Analytical Results for Arsenic and Selenium from Sr002.1
................................ 41 18 Example Results from SR002.1
................................................................................................. .............. 42 19 Example Results from SR002.1 and SR003.1 for Selenium in Fly Ashes from Salem Harbor with Enhanced Hg Control
....................................................................................................... ................ 43 20 Comparison of T otal Mercury Content in Baseline Cases and with Sorbent Injection for CCRs from Dif ferent Facilities
................................................................................................. ............... 44 21 Ranges of Laboratory and Field Leachate Mercury Concentrations Compared with the Drinking W ater Maximum Contaminant Level
....................................................................................... . 4 5 22 Comparison of T otal Arsenic Content in Baseline Cases and with Sorbent Injection for CCRs from Dif ferent Facilities
................................................................................................. ............... 46 23 Ranges of Laboratory and Field Leachate Arsenic Concentrations Compared with the Drinking W ater Maximum Contaminant Level
....................................................................................... . 4 7 24 Comparison of T otal Selenium Content in Baseline Cases and with Sorbent Injection for CCRs from Dif ferent Facilities
................................................................................................. ............... 48 25 Ranges of Laboratory and Field Leachate Selenium Concentrations Compared with the Drinking W ater Maximum Contaminant Level
....................................................................................... . 4 9 26 Example Regression Curves of Experimental Data of Arsenic Solubility as a Function of pH for Brayton Point
........................................................................................................ ................... 49 27 Example 100-Y ear Arsenic Release Estimates for Brayton Point as a Function of the Cumulative Probability for the Scenario of Disposal in a Combustion W aste Landfill
........................... 50 28 Upper Bound of 100 yr Mercury Release Estimates for Landfill Scenario W ithout and W ith Activated Carbon Injection
................................................................................................ .............. 51 29 Upper Bound of 100 yr Arsenic Release Estimates for Landfill Scenario W ithout and W ith Activated Carbon Injection
................................................................................................ .............. 52 30 Upper Bound of 100 yr Selenium Release Estimates for Landfill Scenario W ithout and W ith Activated Carbon Injection
................................................................................................ .............. 53 viiCharacterization of Coal Combustion Residues



# List of T ables

T

able Page 1 List of CCRs collected to date for evaluation of under this research program
.......................................... 4 2 General Characteristics of Coals Burned in U.S. Power Plants
................................................................. 5 3 Projected Coal-Fired Capacity by APC Configuration
............................................................................ .. 6 4 Beneficial Uses of CCRs
....................................................................................................... ................... 1 1 5 Characteristics of Coal Combusted and Facilities Sampled and Reported Here
...................................... 16 6 Fly Ashes from Brayton Point, Pleasant Prairie, Salem Harbor, and Facility C: Elemental Composition (by x-ray fluorescence) and Other Characteristics.
............................................................ 16 7 Fly Ashes from S t. Clair and Facility L: Elemental Composition (by x-ray fluorescence) and Other Characteristics
...................................................................................................... ................... 17 8 CCRs from Facilities with Electrostatic Precipitators: T otal Content of Mercury , Arsenic, Cadmium, Lead and Selenium.
.................................................................................................... ............ 18 9 Detection Limits and Quality Control Information for ICP-MS Analysis for As, Pb, and Se at V anderbilt
............................................................................................................... ......................... 23 10 T otal Content Analysis Results for Reference Fly Ash after Mixing
....................................................... 25 1 1 Composition of Combustion W aste Landfill Leachate
............................................................................ 28 12 Distribution of pH and Concentrations of Arsenic and Selenium from Field CCR Management Facilities from the U.S. EP A

Database
............................................................................... 35 13 Distribution of pH and Concentrations of Arsenic, Selenium, and Mercury from Field CCR Management Facilities
...................................................................................................... .............. 39 14 Leaching (Method SR002.1) and Mass Balance Results for the EP A-Reference Fly Ash
...................... 40

viiiCharacterization of Coal Combustion Residues



# Glossary of T erms
T

erm Definition ACAA American Coal Ash Association ACI activated carbon injection A P C air pollution control APPCD Air Pollution Prevention and Control Division ASTM American Society for T esting and Materials B E T Brunauer, Emmett, and T eller (method for quantification of surface area) B-P AC Brominated Powdered Activated Carbon (product name from Sorbent T echnologies Corp, T

winsburg, OH) B P B Brayton Point baseline B P T Brayton Point test (with ACI) BML below method limit CAIR Clean Air Interstate Rule CAMR Clean Air Mercury Rule CCRs coal combustion residues C C V continuous calibration verification COHP AC Compact Hybrid Particulate Collector CS-ESP cold-side electrostatic precipitator CV AA cold vapor atomic adsorption DAFs dilution and attenuation factors D O E U.S. Department of Ener gy D I deionized (i.e., deionized water) D R C dynamic reaction chamber E P A U.S. Environmental Protection Agency EPRI Electric Power Research Institute E S P electrostatic precipitator FF fabric filter (baghouse) F G D flue gas desulfurization FID flame ionization detector G A B Facility C baseline GA T Facility C test (with ACI) HCl hydrogen chloride Hg 0 

### elemental mercury Hg 2+ 

### oxidized or ionic mercury HS-ESP hot-side electrostatic precipitator ICP-MS inductively coupled plasma-mass spectroscopy ICV internal calibration verification J A B S t. Clair facility baseline JA T S t. Clair facility test (with B-P AC) k

d 

### CCR linear partition coef ficient ixCharacterization of Coal Combustion Residues 

# Glossary of Terms (concluded)

T

erm Definition LOI loss on ignition LS liquid-to-solid (LS ratio) M C mechanical collector MCL maximum concentration limit (for drinking water) MDL method detection limit M L minimum quantification limit NETL National Ener g y T echnology Laboratory NO X 

### nitrogen oxides NSPS New Source Performance S tandard OC/EC or ganic carbon/elemental carbon O R D EP A’ s Of fice of Research and Development OSW EP A’ s Of fice of Solid W aste P

A C powdered activated carbon PJFF pulse jet fabric filter P M particulate matter P P B Pleasant Prairie baseline PPT Pleasant Prairie test (with ACI) P RB sub-bituminous coal mined in W yoming’ s Powder River Basin QA/QC quality assurance/quality control RCRA Resource Conservation and Recovery Act RF A reference fly ash PS particulate scrubber S A B EP A’ s Science Advisory Board S C A specific collection area S C R selective catalytic reduction S D A spray dryer absorber SGLP synthetic ground leaching procedure S H B Salem Harbor baseline S H T Salem Harbor test (with ACI) SNCR selective non-catalytic reduction SO X 

### oxides of sulfur SPLS synthetic precipitation leaching procedure S/S stabilization/solidification SWDA Solid W aste Disposal Act TCLP toxicity characteristic leaching procedure T OXECON toxic emissions control W S wet scrubber X R F X-ray fluorescence

xCharacterization of Coal Combustion Residues



# Acknowledgment s
Extensive input on the research program design was provided by G
. Helms, U.S. EP A, Of fice of Solid W aste (W ashington, DC). Additional technical support was provided by B. Ghorishi, formerly of ARCADIS, and J. Kilgroe, formerly of U.S. EP A, National Risk Management Research Laboratory
. Laboratory testing described herein was carried out by ARCADIS with technical support from V anderbilt Uni
versity . R. Delapp was responsible for the chemical analyses carried out at V anderbilt University
. T echnical assistance also was provided by A. Garrabrants and V . Laohom. K. Ladwig and EPRI are gratefully acknowledged for assistance in obtaining coal combustion residue samples and providing information from the EPRI database on coal combustion residues. C. Senior also is gratefully acknowledged for her assistance in obtaining coal combustion residue samples and related background information for this project.

xiCharacterization of Coal Combustion Residues



# Executive Summary
This report evaluates changes that may occur to coal-fired power plant air pollution control residues from the use of activated carbon and other enhanced sorbents for reducing air emissions of mercury and evaluates the poten
tial for captured pollutants leaching during the disposal or use of these residues. Leaching of mercury , arsenic, and selenium during land disposal or beneficial use of coal combustion residues (CCRs) is the environmental impact pathway evaluated in this report. Coal combustion residues refer collectively to fly ash and other air pollution control solid residues generated during the combustion of coal collected through the associated air pollution control system. This research is part of an on-going ef fort by U.S. Environmental Protection Agency (EPA) to use a holistic approach to account for the fate of mercury and other metals in coal throughout the lifecycle stages of CCR management. The specific objectives of the research reported here are to: 1. Evaluate the potential for leaching to groundwater of mercury, arsenic, and selenium removed from coalfired power plant air emissions by air pollution control technology and, as a result, are contained in CCRs; 2. Provide the foundation for assessing the impact of enhanced mercury and multi-pollutant control technol
ogy on leaching of mercury and other constituents of potential concern from CCRs during the lifecycle of CCR management, including storage, beneficial use, and disposal; and 3. Perform these assessments using the most appropriate evaluation methods currently available. This in
volved use of a laboratory leach testing approach developed by Kosson, et al. (2002), which considers the ef

fects of varying environmental conditions on waste constituent leaching. Ef fective use of this approach required technology transfer to the U.S. EP A

National Risk Management Laboratory , and development of a quality assurance/quality control (QA/QC) framework to help evaluate and verify test results. Air pollution control residues were obtained from coal combustion electric utility facilities with a representative range of facility configurations (including air pollution controls) and coal types combusted. Each of the residues sampled has been analyzed for selected physical properties, and for total content and leaching characteristics. Results of laboratory leaching tests were used to develop estimates of constituent release under field manage
ment scenarios. Laboratory leaching test results also were compared to field observations of leaching. This report focuses on facilities that use injected sorbents for mercury control. It includes four facilities with activated carbon injection (ACI) and two facilities using brominated ACI. Fly ash has been obtained from each facility with and without operation of the sorbent injection technology for mercury control. Each fly ash sampled was evaluated in the laboratory for leaching as a function of pH and liquid-to-solid ratio. Mercury , arsenic and selenium were the primary constituents of interest; results for these elements are presented here. This testing approach was chosen for use because it evaluates leaching over a range of values for two key variables (pH and liquid:solid ratio) that both vary in the environment and af fect the rate of constituent release from waste. The range of values used in the laboratory testing encompasses the range of values expected to be found in the environment for these parameters. Because the ef fect of these variables on leaching is evaluated in the laboratory , prediction of leaching from the waste in the field is expected to be done with much greater reliability
. xiiCharacterization of Coal Combustion Residues 

### Application of this leach testing approach to mercury leaching involved an extensive QA/QC program. This included conducting a mass balance of mercury and other metals using a reference fly ash to ensure that unac
ceptable losses of mercury in lab equipment or glassware or due to volatilization did not occur . If mercury was not found to be leaching, it was critical to ensure that this result was real and not due to mercury losses during handing or processing of the samples. In addition, results from laboratory leaching evaluation were compared to field leachate concentrations from CCR management facilities available from a U.S. EP A

database and an Electric Power Research Institute (EPRI) database to determine if laboratory testing results reasonably represented field observations. Constituent release estimates projected to occur over a 100 year period were developed to evaluate the potential cumulative impacts of dif ferent CCR management scenarios. Disposal in a combustion waste landfill was exam
ined using Monte Carlo simulation based on reported field conditions and for three hypothetical default landfill scenarios. 

## Summary of Conclusions Assessment of CCRs with and without Use of Activated Carbon Injection and Br ominated Carbon Injection. Analysis has been completed for CCRs from four coal combustion facilities using powdered activated carbon injection and from two facilities using brominated powdered activated carbon injection to control mercury emis
sions. For each facility , the evaluation included assessments of CCRs generated both with and without use of the activated carbon injection. None of these facilities had scrubbers as part of their air pollution control technology
. The following conclusions are drawn for this class of facilities:


### • Application of activated carbon injection substantially increased the total mercury content in the resulting

CCRs for five of the six facilities evaluated. Substantially increased arsenic and selenium content in the CCRs was observed at the one facility that employed compact hybrid particulate collector (COHP AC 1 

### ) fabric filter particulate control technology
. This may have resulted from additional arsenic and selenium adsorption onto the CCR while retained in the fabric filters. Significant increase in the selenium content of one additional facility was noted.


### • Mercury is strongly retained by the CCR and unlikely to be leached at levels of environmental concern.

Leaching that did occur did not depend on total mercury content in the CCR, leaching pH, or liquid to solid ratio, and mercury concentrations in laboratory extracts appeared to be controlled by non-linear adsorp
tion equilibrium. Laboratory extract concentrations ranged from less than the minimul detection level (0.01 μ g/L) to 0.2 μ g/L.


### • Arsenic and selenium may be leached at levels of potential concern from CCRs generated at some facili
ties both with and without enhanced mercury control technology . Further evaluation of leaching of arsenic and selenium from CCRs that considers site specific conditions is warranted.


### • Leachate concentrations and the potential release of mercury , arsenic and selenium do not correlate with total content. For many cases, leachate concentrations observed are a function of final pH over the range of field conditions, and the observed leaching behavior implies that solubility in the leachate or aqueous extract controls observed liquid concentration rather than linear adsorption equilibrium. For these cases, use of linear partition coef ficients ( K

d

### ) in modeling leaching phenomena does not reflect the underlying processes. In addition, for many cases, the amount of mercury , arsenic, and selenium estimated to be released over a 100 year interval is a small fraction (< 0.1% – 5%) of the total content. For selenium, release from less than 5% up to the total content of selenium can be anticipated over the 100 year period.

1 For the COHP AC air pollution control configuration, combustion gasses pass through an electrostatic precipitator; then activated carbon is injected into the gas stream before it passes through a fabric filter for particulate collection. 

### xiiiCharacterization of Coal Combustion Residues 

### Therefore, it is not recommended to base landfill management decisions on total content of constituents in CCRs since total content does not consistently relate to quantity released.


### • Results of this assessment also suggest management conditions (e.g., by control of infiltration and pH)

that may result in reduction releases of arsenic and selenium by as much as two orders of magnitude in comparison to upper bound estimated releases.


### • Use of the leaching framework facilitated understanding the variations in anticipated leaching behavior

under the anticipated field landfill disposal conditions, including expected ranges of constituent concen
trations in leachate and cumulative release over a defined time interval. In addition, insights into the mechanisms controlling constituent leaching were obtained. This depth of understanding would not have been possible using leaching tests focused on a single extraction condition (e.g., toxicity characteristic leaching procedure, synthetic precipitation leaching procedure, or synthetic groundwater leaching proce
dure).


### • This study provides baseline data which allows using a reduced set of laboratory testing conditions as a

screening leaching assessment for CCRs from coal combustion facilities employing similar air pollution control technology . For mercury , extraction only at the material’ s natural pH at a liquid-to-solid ratio (LS) of 10 is adequate. For arsenic, extraction at four conditions is warranted to define the range of expected leachate concentrations and release: (i) pH 5.5–6.0 at LS=10, (ii) pH 7.5–8.5 at LS=10, (iii) pH 12.0–12.5 at LS=10 and (iv) natural pH at LS=2. For selenium, either the total content or the same conditions as recommended for arsenic can be used. At least duplicate extractions should be used. Results from this more limited testing can be evaluated in comparison with the results presented in this report to determine if more extensive evaluation is warranted. Implementation of Leaching T est Methods The leaching assessment approach published by Kosson et al. (2002) and implemented in this report was se
lected because, after internal EP A

review (Of fice of Research and Development, Of fice of Solid W aste) and consultation with the Environmental Engineering committee of the EP A

Science Advisory Board, it was consid
ered the only available, peer reviewed, and published approach that allowed consideration of the range of poten
tial field management scenarios expected for CCRs and provided a fundamental foundation for extrapolation of laboratory testing to field scenarios. Additional development and validation of the leaching assessment approach through this project provides the following conclusions:


### • Laboratory leaching test results were consistent with observations of ranges of field leachate pH and

mercury , arsenic, and selenium concentrations. Thus, the leaching test methods employed in this study provide an appropriate basis for evaluating leaching under the range of anticipated field management scenarios.


### • Leaching test methods SR002.1 (Solubility and Release as a Function of pH) and SR003.1 (Solubility and

Release as a Function of LS ratio) have been successfully implemented at the EP A

National Risk Manage
ment Research Laboratory
. The use of these methods is now considered near routine methodology for the laboratory
. 

### • QA/QC methodology conforming with EP A

Category 3 requirements has been developed and demon
strated for the leaching test methods SR002.1 and SR003.1.


### • Further ef ficiency in implementation of the QA/QC methodology may be obtained, based on the results from testing the initial set of CCRs, by reducing the number of replicates and control analyses required under the initial QA/QC plan. These improved project ef ficiencies are being implemented for evaluation of additional CCRs under this project.


### • A mass balance around the laboratory leaching test procedures has been completed for mercury and se
lected metals of potential concern. These results indicate that recoveries were between 60% and 91% for mercury during the leaching tests and subsequent analytical procedures, which is within the uncertainty resulting from heterogeneity within the CCR. Additional mass balance verification may be warranted if future samples have significantly dif ferent characteristics that may result in greater volatility of the con
stituents of interest than in the reference sample evaluated. xivCharacterization of Coal Combustion Residues 

### This is the first of a series of reports that will address the potential for leaching of constituents of potential concern from CCRs. Subsequent reports will address:


### • CCRs from coal-fired power plants that use SO 2 

### scrubbers as a part of their air pollution control technol
ogy 

### • CCRs from coal-fired power plants that use air pollution control technologies other than evaluated in

earlier reports necessary to span the range of coal-types and air pollution configurations.


### • Assessment of leaching for constituents of potential concern under additional management scenarios,

including impoundments and beneficial use.


### • Broader correlation of CCR leaching characteristics to coal type, combustion facility characteristics and

geochemical speciation within CCRs supported by information and analysis on additional trace elements and primary constituents.

xvCharacterization of Coal Combustion Residues



### xviCharacterization of Coal Combustion Residues



# 1. Introduction
Congress has directed EP A

to document that the Clean Air Act regulations are not trading one environmental burden for another
. The Air Pollution Prevention and Control Division (APPCD) of EP A

’ s Office of Research and Development (ORD) is conducting the research to help identifyany potential leaching with unacceptable impacts resulting from land disposal or beneficial use of mercury-enriched CCRs. The research results presented in this report are part of that ef fort. The focus of this report is to present an evaluation of changes to air pollution control residues that may resultfrom the use of sorbent injection as enhanced mercury control technology at coal-fired power plants and to document the potential for transfer of pollutants from the resulting residues to water resources or other environmental systems (e.g., soils, sediments). The residues studied for this report were fly ashes generated using activated carbon and other enhanced sorbents for reducing air emissions of mercury from the power plants and fly ashes from the same power plants without use of sorbent injection. The potential for leaching of mercury and other constituents of potential concern during land disposal or beneficial use of the coal combustion residues (CCRs) is the more narrow focus of this assessment. This research is part of an on-going ef fort by EP A

to use a holistic approach to account for the fate of mercury and other metals in coal throughout the life-cycle stages of CCR management. CCRs include bottom ash, boiler slag, fly ash, scrubber sludge, and other miscellaneous solids generated during the combustion of coal. The boiler slag and bottom ash are not of interest in this study because enhanced mercury emission controls will not change their composition. Flyash characteristics are expected to change from implementation of enhanced mercury emission controls. Fly ash includes unburned and inor ganic materials in coal that do not burn, such as oxides of silicon, aluminum, iron, and calcium. Fly ash is light enough to be entrained in the fluegas stream and captured in the air pollution control equipment. Scrubber sludge is the by-product of the SO 2 

### wet scrubbing process resulting from neutralization of acid gases. Air pollution control can concentrate or partition metals to fly ash and scrubber sludge. When coal is burned in an electric utility boiler , the resulting high combustion temperatures vaporize the Hg in the coal to form gaseous elemental mercury (Hg 0 

### ). Subsequentcooling of the combustion gases and interaction of the gaseous Hg 0 

### with other combustion products result in a por
tion of the Hg being converted to gaseous oxidized forms of mercury (Hg 2+ 

### ) and particle-bound mercury
. The specific chemical form—known as the speciation—has a strong impact on the capture of mercury and other metals by boiler air pollution control (APC) equipment. Sorbents, typically finely ground powdered activated car
bon, can be used to capture mercury
. The sorbent is typically injected upstream of the particulate control device, where both the sorbent and adsorbed mercury are collected. Depending upon the type of sorbent, gas conditioning, and other air pollution control technology in use, there may be changes occurring to the fly ash that may affect the stability and mobility of mercury and other metals in the CCRs. In response to increasingly stricter requirements to reduceair emissions of mercury and other pollutants from coalfired power plants, additional advanced air pollution control technology is being introduced. Activated carbon injection (ACI) or brominated powdered activated carbon injection (B-P AC) are two technologies being considered for widespread use. This research is evaluating changes toair pollution control residues as a result of these technologies, and the impacts of land disposal or commercial use of the residues. The specific objectives of the research reported here are to: 1 Evaluate the potential for leaching to groundwater of

mercury , arsenic, and selenium removed from coal1Characterization of Coal Combustion Residues

### fired power plant air emissions by air pollution control technology and, as a result, contained in CCRs; 2 Provide the foundation for assessing the impact of enhanced mercury and multi-pollutant control technology on leaching of mercury and other constituents of potential concern from CCRs during the lifecycle of CCR management, including storage, beneficial use and disposal; and 3 Perform these assessments using the most appropriate

evaluation methods currently available. This has involved use of a laboratory leach testing approach developed by Kosson, et al. (2002), which considers the ef

fects of varying environmental conditions on waste constituent leaching. Ef fective use of this approach required technology transfer to the U.S. EP A

National Risk Management Laboratory and development of a quality assurance/quality control (QA/QC) framework to help evaluate and verify test results. The approach to satisfying these objectives was to obtain samples of air pollution control residues from a variety of coal-fired power plants, each under operating conditionswith and without use of enhanced mercury control technology
. This report focuses on facilities that employ electrostatic precipitators (ESPs) but do not have SO 2 

### scrubbers for air pollution control. Enhanced mercury control technology consisted of activated carbon injection for four facilities (Brayton Point, Pleasant Prairie, Salem Harbor, and Facility C 1 

### ) and injection of brominated activated carbon for two facilities (S t. Clair and Facility L 1 

### ). This is the first ofa series of reports that will address the potential for crossmedia transfer of constituents of potential concern from CCRs. Subsequent reports will address:



### • CCRs from coal-fired power plants that use scrubbers

as a part of their air pollution control technology (report 2);


### • CCRs from coal-fired power plants that use air pollution control technologies other than evaluated in ear
lier reports necessary to span the range of coal-types and air pollution configurations (report 3);


### • Assessment of leaching for constituents of potential

concern under additional management scenarios, including impoundments and beneficial use on the land (report 4); and,


### • Broader correlation of CCR leaching characteristics

to coal type, combustion facility characteristics andgeochemical speciation within CCRs supported by in1 These facilities have requested to remain anonymous. 

### formation and analysis on additional trace elements and primary constituents (report 4). T

able 1 provides a summary of facilities sampled to dateand indicates which of the reports will present an evaluation of which samples.Sampled CCRs were subjected to multiple leaching conditions according to the designated leaching assessment approach. Leaching conditions included batch equilibrium 2 

### extractions at acidic, neutral, and alkaline conditions at a liquid-to-solid ratio (LS) of 10 mL/g, and LS ratio from 0.5 to 10 mL/g using distilled water as the leachant. The results of this testing are being used to evaluate the likely range of leaching characteristics under a variety of CCR management scenarios. Results of the laboratory leaching tests were compared to the range of observed constituent concentrations in field leachates reported in a U.S. EP A database (EPA, 2000) and an Electric Power Research Institute (EPRI) database (EPRI, 2005). Aprobabilistic assessment approach considered leaching estimates over the observed range of field pH and LS from the U.S. EP A

database to develop 100 yr release estimates for constituents of interest from the CCRs tested. As part of this research program, a QA/QC plan consistent with EP A

requirements was developed for the leaching assessment approach. The QA/QC methodology includedverification of acceptable mercury retention during laboratory testing through evaluation of a mass balance aroundtesting procedures. Laboratory testing for leaching assessment was carried out at the EP A

National Risk Management Laboratory (Research T riangle Park, North Carolina) with technical assistance from V anderbilt University
. 

## 1.1. Regulatory Context 1.1.1. W aste Management Management of coal combustion residues is subject to the Resource Conservation and Recovery Act (RCRA), which is the federal law regulating both solid and hazardous wastes. Subtitle C under the RCRA pertains to hazardouswaste; other solid, non-hazardous wastes fall under Subtitle D. Subtitle C wastes are federally regulated while Subtitle D wastes are regulated primarily at the state level. The

2 In the context of leaching tests, the term “equilibrium” is usedto indicate that the test method result is a reasonable approximation of chemical equilibrium conditions even though thermodynamic equilibrium may not be approached for all constituents. 

### 2Characterization of Coal Combustion Residues 

### original version of the RCRA did not specify whether CCRs were Subtitle C or D wastes. In 1980, the Solid Waste Disposal Act (SWDA) amendments to RCRA conditionallyexcluded CCRs from Subtitle C regulation pending completion of a study of CCR hazards. Since that time, CCRs have been regulated at the state level under Subtitle D. The SWDA amendments to RCRA required EP A

to prepare a report to Congress identifying CCR hazards and recommending a regulatory approach for CCRs. In this report (EP A, 1988), EP A

recommended that CCRs generated by electric utilities continue to be regulated under Subtitle D (See 58 FR 42466, August 9, 1993). Other residues generated at coal-fired electric utilities were not included in this 1993 decision. EP A

conducted a follow-up study specifically aimed at low-volume, co-managed wastes 3 

### and issued another Report to Congress (EP A, 1999) with a similar recommendation. In April 2000, EP A issued a regulatory determination exempting these wastes from hazardous waste regulations (See 65 FR 32214, May 22, 2000). However , concern was expressed over the useof CCR as backfill for mining operations, and it was decided that this practice be regulated under a federal Subtitle D rule. It was also decided by EP A

that federal regulations under Subtitle D are needed for CCR when they are disposed in surface impoundments and landfills. Currently , the Agency is in the process of developing these regulations. The results presented in this report, and subsequentreports, will help provide the information needed to identify the release potential of mercury and other metals thathave been removed from stack gases into air pollution control residues, over a range of plausible management options. These data will help identify those conditions that will either reduce or enhance releases to the land so that the ef fects of different management conditions can be factored into any controls developed under the regulations. 

### 1.1.2. Air Pollution Control On March 10, 2005, EP A

announced the Clean Air Inter
state Rule (CAIR; FR 25162, May 2005), which is expected to increase the use of wet scrubbers and selective catalytic reduction (SCR) units to help reduce sulfur dioxide and nitrogen oxides from coal-fired power plants. On March 15, 2005, EP A

announced the Clean Air Mercury Rule(CAMR; FR 28606, May 2005) for reducing mercury emissions through the use of a cap and trade program. Power plants are the lar gest remaining source of anthropogenic

3 Co-managed wastes are low-volume wastes that are co-managed with the high-volume CCRs. 

### mercury emissions in the county
. When fully implemented, a reduction of 70% is projected to occur (from 48 tons to 15 tons annually). The Clean Air Mercury Rule establishes “standards of per
formance” that limit mercury emissions from new— through new source performance standards (NSPS)—and existing (through emission guidelines) coal-fired power plants by creating a market-based cap-and-trade program that will reduce mercury emissions in two phases. The first phase caps national annual mercury emissions at 38 tonsthrough co-benefit reductions achieved by controlling sulfur dioxide (SO 2 

### ) and nitrogen oxides (NO X 

### ) emissions under CAIR. In the second phase, due in 2018, coal-fired power plants will be subject to a second cap, which willreduce emissions to 15 tons per year upon full implementation. Congress has directed EP A

to document that the Clean Air Act regulations are not trading one environmental burden for another
. The Air Pollution Prevention and Control Division (APPCD) of EP A

’ s Office of Research and Development (ORD) is conducting the current research to help identify any potential pollutant transfers resulting from land disposal or beneficial use of mercury-enriched CCRs. Theresearch results presented in this report are part of that effort. In response to the evolving implementation of advanced air pollution control technology for coal-fired power plants, this research is directed towards understanding changes in CCR characteristics that may increase environmental bur
dens from land disposal of CCRs or impact CCR usage in commercial applications. 

## 1.2. Configurations of U.S. Coal Fired P o wer Plants and Multi-pollutant Con tr ol T e c hnologies The approximately 450 coal-fired electricity generating facilities in the United S tates uses a range of coals and plant configurations. The coal type burned and facility design characteristics af fect the ef fectiveness of various mercury control methods that are or could be used at these plants. The U.S. coal-fired power plants typically burn one of three types of fuel: (1) bituminous coal (also referred to as “high rank” coal), (2) subbituminous coal, and (3) and lignite (subbituminous coal and lignite are referred to as “low rank” coals). Some of the characteristics of interest related to the possible environmental impacts of burning these dif ferent coal types are given in T able 2 (EP A, 2005). 3F a c i l i t y C o a l T y p e A P C C o n f i g u r a t i o n C C R / A s h T y p e ( C C R p H a ) R e p o r t 1 : A C I a n d B - P A C ( t h i s r e p o r t ) B r a y t o n P o i n t l o w - s u l f u r b i t u m i n o u s C S - E S P b w i t h a n d w i t h o u t A C I C l a s s F ( 1 2
. 2 , 9
. 5 ) S a l e m H a r b o r l o w - s u l f u r b i t u m i n o u s c C S - E S P w i t h a n d w i t h o u t A C I ; w i t h S N C R / u r e a C l a s s F ( 1 1
. 7 , 1 0
. 3 ) P R B d s u b b i t u m i n o u s P l e a s a n t P r a i r i e C S - E S P w i t h a n d w i t h o u t A C I C l a s s C ( 1 1
. 2 , 1 1
. 9 ) F a c i l i ty C l o w - s u l f u r b i t u m i n o u s H S - E S P e w i t h a n d w i t h o u t A C I ; w i t h C O H P A C f C l a s s F ( 1 1
. 1 , 8
. 4 ) P R B s u b b i t u m i n o u s / l o w - s u l f u r S t
. C l a i r b u t u m i n o u s b l e n d ( 8 5 : 1 5 ) C S - E S P w i t h a n d w i t h o u t B - P A C C l a s s C / F ( 1 2
. 1 , 1 2
. 2 ) g , h F a c i l i ty L l o w - s u l f u r b i t u m i n o u s H S - E S P w i t h a n d w i t h o u t B - P A C ; w i t h S O F A i p o r t s " o n " f o r N O X j c o n t r o l
. C l a s s F ( 5
. 8 , 6
. 0 ) R e p o r t 2 : F a c i l i t i e s w i t h s c r u b b e r s F a c i l i ty A k l o w - s u l f u r b i t u m i n o u s f a b r i c f i l t e r , l i m e s t o n e w e t s c r u b b e r w i t h a n d w i t h o u t S N C R / u r e a C l a s s F ( 1 0
. 3 , 1 0
. 5 ) F a c i l i ty B l o w - s u l f u r b i t u m i n o u s C S - E S P , m a g n e s i u m - e n h a n c e d l i m e s c r u b b e r ; w i t h S C R l / a m m o n i a C l a s s F ( 1 0
. 3 , 9
. 5 )

m F a c i l i ty H h i g h - s u l f u r b i t u m i n o u s C S - E S P , l i m e s t o n e w e t s c r u b b e r C l a s s F ( 8
. 5 )

n F a c i l i ty I h i g h - s u l f u r b i t u m i n o u s C S - E S P , l i m e s t o n e w e t s c r u b b e r w i t h f o r c e d o x i d a t i o n ; S C R n o t i n u s e w h e n s a m p l e t a k e n C l a s s F ( N T o ) F a c i l i ty K p m e d i u m - s u l f u r b i t u m i n o u s C S - E S P , m a g n e s i u m - e n h a n c e d l i m e w e t s c r u b b e r , n a t u r a l o x i d a t i o n C l a s s F ( 9
. 2 ) R e p o r t 3 : M i s c e l l a n e o u s c o n f i g u r a t i o n s F a c i l i ty E ( U n i t 1 ) m e d i u m - s u l f u r b i t u m i n o u s C S - E S P S C R o p e r a t i n g C l a s s F ( 4
. 8 ) F a c i l i ty E ( U n i t 2 ) m e d i u m - s u l f u r b i t u m i n o u s C S - E S P S C R o ff C l a s s F ( 4
. 3 ) F a c i l i ty E ( U n i t 3 ) l o w - s u l f u r b i t u m i n o u s C S - E S P S C R o p e r a t i n g C l a s s F ( 4
. 8 ) F a c i l i ty E ( U n i t 4 ) q l o w - s u l f u r b i t u m i n o u s H S - E S P S C R o p e r a t i n g C l a s s F ( N T o ) F a c i l i ty F l o w - s u l f u r b i t u m i n o u s C S - E S P C l a s s F ( 4
. 2 ) F a c i l i ty G l o w - s u l f u r b i t u m i n o u s C S - E S P , S N C R o p e r a t i n g C l a s s F ( 4
. 3 ) Characterization of Coal Combustion Residues Ta b l e 1 . List of CCRs collected to date f or e v aluation of under this research prog r am. [Some f acilities are identif ied b y code letter only (e .g., “Facility C”) to preser v e the conf identiality of the CCR source
. ]

a T h e p H o f t h e C C R ( w i t h a n d w i t h o u t A C I o r B - P A C i n j e c t i o n , a s a p p l i c a b l e ) w h e n m i x e d i n d i s t i l l e d w a t e r a t a r a t i o o f 1 g C C R p e r 1 0 m L w a t e r . b C S - E S P = c o l d - s i d e e l e c t r o s t a t i c p r e c i p i t a t o r .

S N C R = s e l e c t i v e n o n - c a t a l y t i c r e d u c t i o n . d P R B = P o w d e r R i v e r B a s i n . e H S - E S P = h o t - s i d e e l e c t r o s t a t i c p r e c i p i t a t o r . f C O H P A C = c o m p a c t h y b r i d p a r t i c u l a t e c o l l e c t o r . 

### continued 4 cCharacterization of Coal Combustion Residues Table 1 (concluded). List of CCRs collected to date for evaluation of under this research program. [Some facilities are identified by code letter only (e.g., “Facility C”) to preserve the confidentiality of the CCR source.]
g T h i s f a c i l i ty h a s H S - E S P f o r p a r t i c u l a t e c o n t r o l
. T h e f l y a s h u n d e r g o e s p n e u m a t i c c o n t r o l
. C o l l e c t e d f l y a s h w i t h a n d w i t h o u t

u s e o f B - P A C
. h T w o s a m p l e s w e r e c o l l e c t e d f r o m t h i s f a c i l i ty . T h e o n l y d i ff e r e n c e b e t w e e n t h e t w o s a m p l e s ( R u n # 1 a n d R u n # 2 ) w a s t h e R u n # 1 s a m p l e w a s a l l o w e d t o a c c u m u l a t e i n t h e h o p p e r f o r 4 h o u r s a n d t h e R u n # 2 s a m p l e f o r 3 0 m i n u t e s p r i o r t o c o l l e c t i o n . N o t e n o u g h f l y a s h w a s c o l l e c t e d w i t h 3 0 m i n u t e s o f a c c u m u l a t i o n t o e v a l u a t e l e a c h i n g p o t e n t i a l
. T h e r e f o r e , t h e s a m p l e t h a t w a s a l l o w e d t o a c c u m u l a t e i n h o p p e r f r o m H S - E S P f o r a b o u t 4 h o u r s p r i o r t o c o l l e c t i o n w a s u s e d f o r l e a c h i n g e v a l u a t i o n . A c o n c e r n i s t h a t m e r c u r y m a y h a v e p a r t i a l l y d e s o r p e d f r o m f l y a s h p r i o r t o c o l l e c t i o n b e c a u s e o f t h e h i g h t e m p e r a t u r e i n t h e c o l l e c t i o n h o p p e r . T o t a l m e r c u r y a n a l y s e s w e r e u s e d t o e v a l u a t e t h e c h a n g e i n m e r c u r y c o n t e n t f o r f l y a s h w i t h a n d w i t h o u t b r o m i n a t e d c a r b o n i n j e c t i o n a ft e r b e i n g c o l l e c t e d o v e r 4 h o u r s a n d 3 0 m i n u t e s . i S O F A = s e p a r a t e d o v e r f i r e a i r . j N O X = o x i d e s o f n i t r o g e n . k C C R s a m p l e s o b t a i n e d w h e n S N C R w a s i n u s e ( d u r i n g s u m m e r m o n t h s ) a n d n o t i n u s e . l S C R = s e l e c t i v e c a t a l y t i c r e d u c t i o n . m F o r F a c i l i ty H , s l u d g e i s f i r s t c o l l e c t e d i n t h e a b s o r b e r a t 1 2
– 1 5 % s o l i d s , t h e n g o e s t h r o u g h c y c l o n e t o a c h i e v e 5 0 % s o l i d s , a n d

f i n a l l y i s d e w a t e r e d u s i n g a b e l t p r e s s t o > 9 0 % s o l i d s . W h i l e o n b e l t , g y p s u m i s " s p r a y e d " t o r e m o v e e x c e s s s o l u b l e s a l t s . F o r t h i s f a c i l i ty , s a m p l e s h a v e b e e n o b t a i n e d o f ( 1 ) p r e p a r e d g y p s u m ( w h i c h i s u s e d f o r w a l l b o a r d p r o d u c t i o n ) a n d ( 2 ) f l y a s h f r o m t h e C S - E S P
. n F a c i l i ty I h a s a 5 0 0 M W t a n g e n t i a l - f i r e d b o i l e r . S a m p l e s f r o m t h i s f a c i l i ty i n c l u d e ( 1 ) f l y a s h w h e n t h e S C R w a s o p e r a t i n g , ( 2 ) f l y

a s h w h e n S C R w a s n o t o p e r a t i n g , a n d ( 3 ) r a w F G D s l u d g e w h e n t h e S C R w a s n o t o p e r a t i n g . S c r u b b e r s l u d g e f r o m t h i s f a c i l i ty i s u s e d i n m a k i n g g y p s u m f o r p r o d u c i n g w a l l b o a r d
. T h e s a m p l e s f r o m t h i s f a c i l i ty w e r e g y p s u m a n d F G D s l u d g e . T h e r e w a s n o t e n o u g h s l u d g e t o t e s t f o r l e a c h i n g , s o t h e p H w a s n o t t e s t e d
. o N T = n o t t e s t e d
. p F a c i l i ty K i s a n 8 0 0 M W f a c i l i ty w i t h t w o 4 0 0 M W u n i t s ( t a n g e n t i a l f i r e d )
. A P C i n c l u d e s C S - E S P , m a g n e s i u m - e n h a n c e d l i m e w e t s c r u b b e r w i t h n a t u r a l o x i d a t i o n . T h e r e i s n o S C R
. S a m p l e s r e c e i v e d f r o m F a c i l i ty K , a r e ( 1 ) p a r t i a l l y d e w a t e r e d F G D s l u d g e , ( 2 ) f l y a s h s a m p l e , a n d ( 3 ) f l y a s h s t a b i l i z e d s l u d g e . q F l y a s h f o u n d t o h a v e l o w m e r c u r y a n d s e l e n i u m c o n t e n t a n d , t h e r e f o r e , w a s n o t i n c l u d e d i n t h e l e a c h i n g e v a l u a t i o n . T

a b le 2. Gener al Character istics of Coals Bur ned in U
. S
. P o w er Plants (EP A, 2005). M e r c u r y C h l o r i n e S u l f u r A s h H H V a C o a l p p m ( d r y ) p p m ( d r y ) % ( d r y ) % ( d r y ) B T U / l b ( d r y ) R a n g e A v g R a n g e A v g R a n g e A v g R a n g e A v g R a n g e A v g B i t u m i n o u s 0
. 0 3 6
– 0
. 2 7 9 0
. 1 1 3 4 8
– 2 7 3 0 1 0 3 3 0
. 5 5 – 4
. 1 0 1
. 6 9 5
. 4
– 2 7
. 3 1 1
. 1 8 6 4 6
– 1 4 0 1 4 1 3 2 0 3 S u b b i t u m i n o u s 0
. 0 2 5 – 0
. 1 3 6 0
. 0 1 7 5 1
– 1 1 4 3 1 5 8 0
. 2 2
– 1
. 1 6 0
. 5 0 4
. 7 – 2 6
. 7 8
. 0 8 6 0 6
– 1 3 1 6 8 1 2 0 0 5 L i g n i t e 0
. 0 8 0
– 0
. 1 2 7 0
. 1 0 7 1 3 3
– 2 3 3 1 8 8 0
. 8
– 1
. 4 2 1
. 3 0 1 2
. 2
– 2 4
. 6 1 9
. 4 9 4 8 7 – 1 0 7 0 2 1 0 0 2 8 a H H V = h i g h e r h e a t i n g v a l u e . 

### 1.2.1. Current Air Pollution Control T e ch nologies The current combined capacity of U.S. coal-fired power plants is just over 300 GW and includes a wide range ofcombinations of installed air pollution control (APC) devices. T

able 3 shows the current and projected coal-fired capacity by APC configuration. Several of the air pollution control devices described here will remove some mercury (cobenefit control) from stack gases as they perform their main function. Current APC devices are designed primarily to control particulates, oxides of sulfur (SO X 

### ), and NO X 

### .Post-combustion particulate matter controls used at coalfired utility boilers in the United S tates can include ESPs, fabric filters (FF), particulate scrubbers (PS), or mechanical collectors (MC). Post-combustion SO 2 

### controls can consist of a wet scrubber (WS), spray dryer adsorber (SDA), or duct injection. Post-combustion NO X

### controls can involve SCR or selective noncatalytic reduction (SNCR). In response to current and proposed NO X 

### and SO 2 

### control requirements, additional NO X 

### control and flue gas desulfurization (FGD) systems are expected to be installed andmore widely used in the future. Over half of the U.S. coalfired capacity is projected to be equipped with SCR and/or FGD technology by 2020. The mercury capture ef ficiency of existing ESPs and FFs appears to heavily depend on the partitioning of mercurybetween the particulate and vapor phases and the distribu5T able 3. Projected Coal-Fired Capacity b y APC Conf igur ation (EP A, 2005). C u r r e n t C a p a c i t y b 2 0 1 0 C a p a c i t y c a A P C C o n f i g u r a t i o n ( M W ) ( M W ) c 2 0 2 0 C a p a c i t y ( M W ) C o l d - S i d e E S P 1 1 1 , 6 1 6 7 5 , 7 3 2 4 8 , 9 1 5 C o l d - S i d e E S P + W e t S c r u b b e r 4 1 , 7 4 5 3 4 , 5 7 0 3 3 , 1 1 7 C o l d - S i d e E S P + W e t S c r u b b e r + A C I - - - 3 7 9 3 7 9 C o l d - S i d e E S P + D r y S c r u b b e r 2 , 5 1 5 3 , 1 6 1 5 , 4 0 3 C o l d - S i d e E S P + S C R 4 5 , 9 8 4 3 5 , 3 1 2 2 2 , 5 2 8 C o l d - S i d e E S P + S C R + W e t S c r u b b e r 2 7 , 7 7 5 6 2 , 6 6 3 9 8 , 1 3 8 C o l d - S i d e E S P + S C R + D r y S c r u b b e r - - - 1 1 , 9 7 9 1 3 , 1 5 3 C o l d - S i d e E S P + S N C R 7 , 0 1 9 4 , 5 7 6 2 , 5 3 4 C o l d - S i d e E S P + S N C R + W e t S c r u b b e r 3 1 7 2 , 8 3 0 6 , 0 8 8 F a b r i c F i l t e r 1 1 , 9 6 9 1 0 , 8 8 5 7 , 6 4 6 F a b r i c F i l t e r + D r y S c r u b b e r 8 , 8 3 2 8 , 0 3 7 9 , 1 6 3 F a b r i c F i l t e r + W e t S c r u b b e r 4 , 9 6 0 4 , 9 6 0 4 , 9 6 0 F a b r i c F i l t e r + D r y S c r u b b e r + A C I - - - 1 9 5 1 9 5 F a b r i c F i l t e r + S C R 2 , 2 1 0 2 , 9 5 0 1 , 3 3 0 F a b r i c F i l t e r + S C R + D r y S c r u b b e r 2 , 0 0 2 2 , 6 0 1 4 , 4 2 2 F a b r i c F i l t e r + S C R + W e t S c r u b b e r 8 0 5 8 0 5 2 , 3 6 3 F a b r i c F i l t e r + S N C R 2 6 7 2 6 7 3 4 5 F a b r i c F i l t e r + S N C R + D r y S c r u b b e r 5 5 9 5 5 7 5 5 7 F a b r i c F i l t e r + S N C R + W e t S c r u b b e r 9 3 2 9 3 2 1 , 1 0 8 H o t - S i d e E S P 1 8 , 9 2 9 1 1 , 7 6 3 1 0 , 1 6 0 H o t - S i d e E S P + W e t S c r u b b e r 8 , 7 2 4 1 0 , 5 0 9 1 0 , 3 9 8 H o t - S i d e E S P + D r y S c r u b b e r - - - 5 3 8 5 3 8 H o t - S i d e E S P + S C R 5 , 9 5 2 3 , 2 3 3 1 , 8 4 7 H o t - S i d e E S P + S C R + W e t S c r u b b e r 6 8 8 6 , 8 6 4 9 , 9 1 2 H o t - S i d e E S P + S N C R 6 8 4 1 , 4 9 0 1 , 3 3 4 H o t - S i d e E S P + S N C R + W e t S c r u b b e r 4 7 4 4 7 4 6 2 7 T

o t a l E x i s t i n g U n i t s 3 0 4 , 9 5 5 2 9 8 , 2 6 3 2 9 7 , 1 6 1 N e w B u i l d s o f C o a l S t e a m U n i t s F a b r i c F i l t e r + S C R + W e t S c r u b b e r - - - 2 2 1 1 7 , 2 9 2 T

o t a l A l l U n i t s 3 0 4 , 9 5 5 2 9 8 , 4 8 4 3 1 4 , 4 5 3 a I n t e g r a t e d g a s i f i c a t i o n c o m b i n e d c y c l e u n i t s a r e n o t i n c l u d e d i n t h i s l i s t
. b C u r r e n t c a p a c i ty i n c l u d e s s o m e S C R a n d F G D u n i t s p r o j e c t e d t o b e b u i l t i n 2 0 0 5 a n d 2 0 0 6
. c 2 0 1 0 a n d 2 0 2 0 i s c a p a c i ty p r o j e c t e d f o r f i n a l C A I R r u l e ; I n t e g r a t e d P l a n n i n g M o d e l p r o j e c t s s o m e c o a l r e t i r e m e n t s a n d s o m e

n e w c o a l i n 2 0 1 0 a n d 2 0 2 0
. Characterization of Coal Combustion Residues



### tion of mercury species (e.g., elemental or oxidized) in the vapor phase. In general, ESPs and FFs are quite ef ficient at removing mercury in the particulate phase; however , the overall mercury removal ef ficiency in these devices may be low if most of the mercury entering the device is in the vapor phase (MTI, 2001). Many factors contribute to this range of performance. Dif ferences in mercury contents of U.S. coals result in a range of mercury concentrations in the flue gas from the boiler . In general, it is easier to achieve higher mercury percent removal with higher mercury inlet concentrations (MTI, 2001). The addition of NO X

### controls may improve the mercury capture ef ficiency of particulate collection devices for some cases. 

### 1.2.2. Enhancement of Controls for Mercury Removal: Sorbent Injection Unlike the technologies described earlier , where mercury removal was incidental and achieved as a co-benefit with removal of other pollutants, controls are under develop
ment that tar get mercury removal by injecting sorbent 6Characterization of Coal Combustion Residues

### materials into the gas stream of coal-fired boilers. Injection of dry sorbents, such as powdered activated carbon (P

AC), has been used for control of mercury emissions from waste combustors and has been tested at numerous utility units in the United S tates. However , sorbent injection experience on waste combustors may not be directly transferable to coal-fired electric utility boilers due to dif fer
ences in facility sizes and mercury content and speciation in the combustion gases. Figure 1 presents a coal-fired boiler with sorbent injection and spray cooling. Figure 2 presents a power plant with a hot-side ESP (HS-ESP), carbon injection, and a compact hybrid particle collector . Dry sorbent is typically injected into the ductwork upstream of a particulate matter (PM) control device—normally either an ESPor FF . Usually the sorbent is pneumatically injected as a powder , and the injection location is determined by the existing plant configuration. Another approach, designed to segregate colFigure 1. Coal-Fired Boiler with Sorbent Injection and Spra y Cooling (Senior et al., 2003a).

Figure 2. Flo w Diag r am f or P o w er Plant with a Hot ESP , Carbon Injection, and a COHP A C (Senior et al., 2003a). 

### 7Characterization of Coal Combustion Residues 

### lected fly ash from collected sorbent, would be to retrofit a pulse-jet FF (PJFF) downstream of an existing ESP and inject the sorbent between the ESPand the PJFF
. This type of particulate removal configuration is called a Compact Hybrid Particle Collector (COHP AC) by its manufacturer and, when combined with sorbent injection, is called T oxic Emission Control (T OXECON). The T OXECON configuration can be useful because it avoids commingling the larger flyash stream with mercury recovered on the injected sorbent. Implementation of sorbent injection for mercury control will likely entail either:



### • Injection of powdered sorbent upstream of the existing PM control device (ESP or FF); or


### • Injection of powdered sorbent downstream of the existing ESP and upstream of a retrofit PJFF , the T OXECON option; or


### • Injection of powdered sorbent between ESP fields

( T OXECON-II approach). In general, factors that af fect the performance of sorbent technology for mercury methods include:



### • Injection concentration of the sorbent measured in lb/

MMacf ; 4


### • Flue gas conditions, including temperature and concentrations of hydrogen chloride (HCl) and sulfur trioxide (SO 3 

### );


### • The air pollution control configuration;


### • The characteristics of the sorbent; and


### • The method of injecting the sorbent. 

### 1.2.3. Mercury Control by Conventional P A C InjectionThe most widely tested sorbent for mercury control at utility boilers is P AC. In general, the ef ficacy of mercury capture using standard P

AC increases with the amount of oxidized or ionic mer
cury (Hg 2+ 

### ) in flue gas relative to elemental mercury (Hg 0 

### ), 5 

### the number of active sites in the P AC, 6 

### and lower tempera4 Sorbent injection concentration is expressed in lb/MMacf (i.e., pounds of sorbent used for each million actual cubic feet of gas). For a 500 MW boiler , a sorbent rate of 1.0 lb/MMacf will correspond to approximately 120 lb/hour of sorbent.
5 S tandard P AC binds mercury via physical (i.e., weak) bonds, which are formed more easily with Hg 2+
. There have been results that show a similar removal for both elemental and oxidized mercury . However, the results do not account for surface catalyzed oxidation of Hg 0 followed by sorption on the carbon (EP A, 2005). 

### ture. The amount of Hg 2+ 

### in flue gas is usually directly influenced by the amount of chlorine present in the flue gas, with higher chlorine content enhancing Hg 2+

### formation. Based on these factors, standard PAC injection appears to be generally effective for mercury capture on lowsulfur bituminous coal applications, but less ef fective for the following applications:



### • Low-rank coals with ESP (current capacity of greater

than 150 GW ; the capacity with this configuration is not expected to increase significantly in the future). Lower chlorine and higher calcium contents in coallead to lower levels of chlorine in flue gas, which results in reduced oxidation of mercury and, therefore, lower Hg 2+ 

### in flue gas;


### • Low-rank coals with SDA and FF (current capacity of

greater than 10 GW
. These number of facilities with this configuration is expected to increase significantly in the future). Similar effect as above, except lime reagent from the SDA scavenges even more chlorine from flue gas;


### • High-sulfur coal (current capacity with wet FGD of

approximately 100 GW
. The number of facilities with this configuration is likely to increase to more than 150 GW capacity by 2015). Relatively high levels of SO 3 

### compete for active sites on P AC, which reduces the number of sites available for mercury . Generally , plants will use wet FGD and, in many cases, SCR; P

AC injection may be needed as a trim application; and


### • Hot-side ESPs (current capacity of approximately 30

GW
. The number of facilities with this configuration is not likely to increase.). W eak (physical) bonds getruptured at higher temperatures resulting in lower sorption capacity
. 

### 1.2.4. Mercury Control by Halogenated P A C Injection Some situations, as described above, may not have adequate chlorine present in the flue gas for good mercury capture by standard P AC. Pre-halogenated P AC sorbents have been developed to overcome some of the limitations associated with PAC injection for mercury control in power plant applications (Nelson et al., 2004; Nelson, 2004). Two halogenated P AC sorbents have been tested extensively in the field. They are Sorbent Technologies Corp. brominatedP

AC (B-P AC) and Norit America’ s halogenated P A C (DARCO HG-LH, formerly known as E-3).

6 These are collection of atoms/radicals such as oxygen, chlorine, and hydroxyls that provide binding sites. 

### 8Characterization of Coal Combustion Residues 

### Halogenated P ACs offer several potential benefits. Relative to standard P AC, halogenated P AC use:


### • may expand the usefulness of sorbent injection to many

situations where standard P AC may not be as effective;


### • may avoid the need for installation of downstream FF ,

thereby improving cost-effectiveness of mercury capture; 

### • would, in general, be at lower injection rates, which

potentially will lead to fewer plant impacts and a lower carbon content in the captured fly ash;


### • may result in somewhat better performance with lowsulfur (including low-rank) coals because of less competition from SO 3 

### ; and,


### • may be a relatively inexpensive and attractive control

technology option for technology transfer to developing countries as it does not involve the capital intensive FF installation. Performance of a halogenated sorbent such as B-PAC appears to be relatively consistent regardless of coal type andappears to be mostly determined by whether or not the capture is in-flight

C as in upstream of a cold-side ESP (CSESP)

C or on a fabric filter
. 

## 1.3. Coal Combustion Residues Fossil fuel combustion (burning of coal, natural gas, or oil) is the primary source of ener gy in the United S tates— providing approximately 67% of the total demand in 1997. Coal-fired utilities provide more than 50% of all electric power generated using fossil fuels (EP A, 1999). In 1994 there were approximately 1,250 separate coal-fired boilers in operation at 450 dif ferent utilities throughout the United S tates (EP A, 1999). These boilers used approximately 900million tons of coal and produced approximately 105 million tons of high-volume coal combustion residues—fly ash, bottom ash, boiler slag, and FGD wastes (EP A, 1999).Regulations that require the reduction of mercury air emissions from coal-fired power plants will result in changesto coal combustion residues including increasing the concentration of mercury and other trace metals (Figure 3; EP A, 2002). CCRs result from unburned carbon and inor ganic materials in coal that do not burn, such as oxides of silicon, aluminum, iron, and calcium. Air pollution control can concentrate or partition metals in fly ash and scrubber sludge. Bottom ash and boiler slag are not af fected by air pollution control technology , and therefore, these materials are notexamined in this report. Bottom ash is the unburned material that is too heavy to be entrained in the flue gas stream Figure 3. Lif e-Cycle Ev aluation of Coal Comb ustion Residues (EP A, 2002). 

### and drops out in the furnace. Boiler slag, unburned carbon or inorganic material in coal that does not burn, falls to the bottom of the furnace and melts. Fly ash and scrubber sludge are the two types of CCRs of interest in this report. Fly ash is the unburned material from coal combustion that is light enough to be entrained in the flue gas stream, carried out of the process, and collected asa dry material in the air pollution control equipment. Seventy million tons of fly ash were produced in 2003. FGD wastes (or scrubber sludge) result from a SO 2 

### wetscrubbing process and generally contain 5% to 10% solids. The quantity of FGD material produced depends on the sulfur content of the coal and the amount of coal being combusted. Thirty million tons of FGD wastes were generated in 2003. The properties of fly ash and scrubber residues from many facilities are likely to change as a result of enhanced air pollution controls for reducing mercury stack emissions. Changes in CCR properties will include increased content of mercury and other co-collected metals (e.g., arsenic, selenium) and the presence of injected sorbent or otherchemical modifiers to improve mercury removal. In several prevalent APC configurations, the sorbent will be commingled with either fly ash or other residue streams, modifying both chemical and physical properties of the CCR. 

## 1.4. Residue Management Practices CCRs can be disposed in landfills or surface impoundments or used in commercial applications to produce concrete and gypsum wallboard, among other products. The major pathway of concern for release from land disposal and some beneficial use applications is leaching. Research on theimpact of CCR disposal on the environment has been conducted by many researchers and has been summarized by 9Characterization of Coal Combustion Residues 

### the EP A

(1988, 1999). However , most of the existing CCR data are for CCRs prior to implementation of mercury or multi-pollutant controls. 

### 1.4.1. Beneficial Use In the United S tates, approximately 31% of all CCRs produced are reused in commercial applications or other beneficial uses. Thirty-two percent of fly ash is used in commercial applications such as making concrete/grout, structural fill, and highway construction (ACAA, 2000; Thorneloe, 2003). Six million tons of the scrubber sludge (or 26%) was used in making wall board (ACAA, 2000; Thorneloe, 2003). In Europe, use of CCRs for commercial applications/beneficial uses is much higher (over 50%). T

able 4 ACCA, 2003) and Figure 4 present the primarycommercial uses of CCRs, and a breakdown of U.S. production and usage by CCR type. The primary commercial applications or commercial uses of CCRs are shown.Some of the beneficial uses may have the potential to release mercury from the CCRs, particularly in high-temperature processes. In cement manufacturing, for example, CCRs are inputs to the cement kiln. It is expected that vir
tually all mercury will be volatilized from CCRs in this application. Even where mercury can be captured by thecontrols on cement kilns, approximately two-thirds of cement kiln dust captured by the control devices is reintroduced into the kiln. Therefore, a significant fraction of the mercury in CCRs introduced into cement kilns may be emitted to the air at the cement plant. Some mercury may also be revolatilized when CCRs are used as a filler forasphalt or when FGD material is used in wallboard manufacturing. A separate report will present the results from a study conducted to evaluate the thermal stability of mer
cury and other metals during application of these hightemperature processes. The fate of mercury and other metals is a potential concernwhen CCRs are used on the land (mine reclamation, building highways, soil amendments, agriculture and in making concrete, cement) or to make products that are subsequently disposed (e.g., disposal of wall board in unlined landfill). For several commercial uses, it appears less likely thatmercury in CCRs will be reintroduced into the environment, at least during the lifetime of the product. For example, mercury appears unlikely to be volatilized from confined uses such as concrete, flowable fill, or structural fill. The potential for leaching of mercury in these applications also seems limited, in part due to the relative imper
meability of concrete and flowable fill; however , special applications such as those involving continuous immer
Figure 4. Uses of CCRs Based on 2003 Industr y Statistics (A CAA, 2003). 

### 10a C C P C a t e g o r i e s F l y A s h B o t t o m A s h F G D G y p s u m F G D M a t e r i a l

W e t S c r u b b e r s B o i l e r S l a g b F G D M a t e r i a l

D r y S c r u b b e r s b F G D O t h e r b F B C A s h b , c C C P P r o d u c t i o n C a t e g o r y T o t a l s d 7 0 , 1 5 0 , 0 0 0 1 8 , 1 0 0 , 0 0 0 1 1 , 9 0 0 , 0 0 0 1 7 , 3 5 0 , 0 0 0 1 , 8 3 6 , 2 3 5 1 , 4 4 4 , 2 7 3 1 6 7 , 3 4 5 7 9 6 , 7 1 8 C C P P r o d u c t i o n T o t a l 1 2 1 , 7 4 4 , 5 7 1 e C C P U s e C a t e g o r y T o t a l s 2 7 , 1 3 6 , 5 2 4 8 , 2 4 7 , 2 7 3 8 , 2 9 9 , 0 6 0 4 8 4 , 4 1 2 1 , 7 5 6 , 0 0 4 1 9 7 , 5 0 9 0 2 6 3 , 6 2 3 A l l C C P U s e d T o t a l 4 6 , 3 8 4 , 4 0 5 C C P U s e b y A p p l i c a t i o n f C o n c r e t e / C o n c r e t e P r o d u c t s /G r o u t 1 2 , 2 6 5 , 1 6 9 2 9 8 , 1 8 1 6 5 , 6 9 3 0 1 5 , 9 0 7 3 4 , 2 8 4 0 0 C e m e n t / R a w F e e d f o r C l i n k e r 3 , 0 2 4 , 9 3 0 4 9 3 , 7 6 3 4 2 0 , 0 4 3 0 1 5 , 7 6 6 2 , 4 6 9 0 0 F l o w a b l e F i l l 1 3 6 , 6 1 8 2 0 , 3 2 7 0 0 0 9 , 1 8 4 0 0 S t r u c t u r a l F i l l s / E m b a n k m e n t s 5 , 4 9 6 , 9 4 8 2 , 4 4 3 , 2 0 6 0 2 2 4 , 1 0 0 1 1 , 0 7 4 1 2 , 1 4 1 0 0 R o a d B a s e /S u b - b a s e / P a v e m e n t 4 9 3 , 4 8 7 1 , 1 3 8 , 1 0 1 0 0 2 9 , 8 0 0 0 0 0 S o i l M o d i f i c a t i o n /S t a b i l i z a t i o n 5 1 5 , 5 5 2 6 7 , 9 9 8 0 7 0 4 0 1 1 4 0 1 8 8 , 7 0 8 M i n e r a l F i l l e r i n A s p h a l t 5 2 , 6 0 8 0 0 0 3 1 , 4 0 2 0 0 0 S n o w a n d I c e C o n t r o l 1 , 9 2 8 6 8 3 , 5 5 6 0 0 1 0 2 , 7 0 0 0 0 0 B l a s t i n g G r i t / R o o f i n g G r a n u l e s 0 4 2 , 6 0 4 0 0 1 , 4 5 5 , 1 4 0 0 0 0 M i n i n g A p p l i c a t i o n s 6 8 3 , 9 2 5 1 , 1 8 4 , 9 2 7 0 2 5 9 , 6 0 8 5 9 , 8 0 0 1 3 0 , 7 2 3 0 1 1 , 0 4 9 W

a l l b o a r d 0 0 7 , 7 8 0 , 9 0 6 0 0 0 0 0 W

a s t e S t a b i l i z a t i o n /S o l i d i f i c a t i o n 3 , 9 1 9 , 8 9 8 3 0 , 5 0 8 0 0 0 0 0 4 9 , 2 1 7 A g r i c u l t u r e 1 2 , 1 4 0 3 , 5 3 4 3 2 , 5 1 8 0 0 2 , 2 9 5 0 0 A g g r e g a t e 1 3 7 , 1 7 1 5 1 2 , 7 6 9 0 0 3 1 , 6 0 0 6 , 2 9 9 0 0 M i s c e l l a n e o u s / O t h e r 3 9 6 , 1 5 0 1 , 3 2 7 , 7 9 7 0 0 2 , 8 1 5 0 0 1 4 , 6 4 9 C C P C a t e g o r y U s e T o t a l s 2 7 , 1 3 6 , 5 2 4 8 , 2 4 7 , 2 7 3 8 , 2 9 9 , 0 6 0 4 8 4 , 4 1 2 1 , 7 5 6 , 0 0 4 1 9 7 , 5 0 9 0 2 6 3 , 6 2 3 A p p l i c a t i o n U s e t o P r o d u c t i o n R a t e 3 8
. 6 8 % 4 5
. 5 7 % 6 9
. 7 4 % 2
. 7 9 % 9 5
. 6 3 % 1 3
. 6 8 % 0
. 0 0 % 3 3
. 0 9 % O v e r a l l C C P U t i l i z a t i o n R a t e 3 8
. 1 0 % a T h e A m e r i c a n C o a l A s h A s s o c i a t i o n u s e s C C P ( c o a l c o m b u s t i o n p r o d u c t s ) t o r e f e r t o C C R s . b A s s u b m i t t e d b a s e d o n 6 0 % c o a l b u r n . c F B C = f l u i d i z e d - b e d c o m b u s t i o n . d C C P P r o d u c t i o n t o t a l s f o r F l y A s h , B o t t o m A s h , F G D G y p s u m , a n d W e t F G D a r e e x t r a p o l a t e d e s t i m a t e s r o u n d e d o ff t o t h e

n e a r e s t 5 0 , 0 0 0 t o n s . e C C P U s e d t o t a l s f o r F l y A s h , B o t t o m A s h , F G D G y p s u m , a n d W e t F G D a r e p e r e x t r a p o l a t i o n c a l c u l a t i o n s ( n o t R o u n d e d o ff )
. f C C P U s e s b y a p p l i c a t i o n f o r F l y A s h , B o t t o m A s h , F G D G y p s u m , a n d W e t F G D a r e c a l c u l a t e d p e r p r o p o r t i o n i n g t h e C C P U s e d

C a t e g o r y T o t a l s b y t h e s a m e p e r c e n t a g e a s e a c h o f t h e i n d i v i d u a l ty p e s ' r a w d a t a c o n t r i b u t i o n s t o t h e a s - c u b m i t t e d r a w d a t a s u b m i t t a l t o t a l ( n o t r o u n d e d o ff )
. Characterization of Coal Combustion Residues T

able 4. Benef icial Uses of CCRs (A CAA, 2003).



### sion in water may produce dif ferent results. The impact of ments are almost always located on-site with the combus
advanced mercury emissions control technology (e.g., ACI) tion operations. Although the distribution of units is about on beneficial use applications is uncertain. There is con- equal between landfills and surface impoundments, there cern that the presence of increased concentrations of mer- is a trend toward increased use of landfills as the primary cury, certain other metals, or high carbon content may re- disposal method. duce the suitability of CCRs for use in some applications (e.g., in Portland cement concrete). 

## 1.5. Leaching Protocol One of the major challenges facing this research was iden
- 

### 1.4.2. Land Disposal tification of an appropriate test protocol for evaluating the There are approximately 600 land-based CCR waste dis- leaching potential of CCRs that may have increased levels posal units (landfills or surface impoundments) being used of several metals, particularly mercury. The goal of this by the 450 coal-fired power plants in the United States research is to develop the most accurate estimates of likely (EPA, 1999). About 70% of the 122 million tons of CCRs constituent leaching when CCRs are land disposed. These generated annually are land disposed. Landfills may be estimates of leaching need to be appropriate for assessing located either on-site or off-site while surface impound- at a national level the likely impacts through leaching of 11Characterization of Coal Combustion Residues 

### pollutants from CCRs that is a consequence of installing enhanced mercury and/or multi-pollutant controls. T o achieve this goal requires that U.S. EP A

evaluate leaching potential for CCRs as-managed (to the degree this is known)and that the leach testing results can be appropriately extrapolated to a national assessment. A large part of the approach to achieving this has been to identify and evaluateCCR samples collected from the most prevalent combinations of power plant design (with a focus on air pollution control configurations) and coal type used. U.S. EP A

and EPRI have also examined and collected data on the actual disposal conditions for CCRs because these conditions will af

fect leaching and will also vary over time. When disposed, CCRs are typically monofilled or disposed with other CCRs. However , CCR composition can change over time, due to changes in the source of coal or coal typeburned or due to installation of additional pollution control equipment, so the conditions of leaching created by the CCRs will also change over time. Many leaching tests have been developed by regulatory agencies, researchers, or third-party technical standards or ganizations and are described in the published literature. S tates and others have expressed concern with the variety of leaching protocols in use, the lack of correlation of test results with field conditions and actual leaching, and lack of comparability of available data because of incomplete reporting of test conditions. There is also limited or no quality assurance (QA) information for many of these tests. Leaching tests such as the toxicity characteristic leaching procedure (TCLP), 7 

### which reflects municipal solid wasteco-disposal conditions; the synthetic precipitation leaching procedure (SPLP); or any number of deionized-water based tests may be inappropriate or are at least not optimal for evaluating the leaching potential of CCRs as they are

7 TCLP was not included as part of this study for two reasons. First, EP A

previously made a waste status determination under RCRA that coal combustion residues are non-hazardous (65 FR 32214, May 22, 2000). Therefore, use of TCLP was not required as indicated under the RCRA toxicity characteristic regulationfor determination of whether or not CCRs were hazardous. Second, TCLP was developed to simulate co-disposal of industrial waste with municipal solid waste as a mismanagement scenario and to reflect conditions specific to this scenario. However , thevast majority of CCRs are not being managed through co-disposal with municipal solid waste, and the test conditions for TCLP are dif ferent from the actual management practices formost CCRs. In seeking a tailored, “best-estimate” of CCR leaching, the leaching framework provides the flexibility to consider the ef fects of actual management conditions on these wastes, and so will be more accurate in this case. 

### actually managed. These tests either presume a set of prevailing landfill conditions that may or may not exist at CCR disposal sites (e.g., TCLP), try to account for an environmental factor considered to be important in leaching (e.g., SPLP), or presume that the waste tested will define the disposal conditions—such as deionized (DI) water tests. Most existing leaching tests are empirical in that results are presented simply as the contaminant concentrationsleached when using the test and presented without measuring or reporting values for factors that may af fect waste leaching or that provide insight into the chemistry that is occurring in leaching. Most tests are performed as a single batch test and so do not consider the ef fect of variations in conditions on waste constituent leaching. 8 

### In searching for a leach testing approach that will produce the most reliable results for this waste and that can be used to predict leaching nationally , EP A

sought an approach that (1) considers the range of known CCR chemistry and management conditions (including re-use) and (2) permits development of data that are comparable across U.S. coaland CCR types. Because the data resulting from this research will be used to support regulations, careful scrutiny of the data is expected. Therefore, the use of a published, peer -reviewed protocol is also considered to be an essential element of this work. EP A ’ s Of fice of Research and Development (ORD) has worked closely with EP A

’ s Of fice of Solid W aste (OSW) to identify an appropriate leaching protocol for evaluating CCRs. The protocol that has been adopted is the “Integrated Framework for Evaluating Leaching in Waste Management and Utilization of Secondary Materials” (Kossonet al., 2002) and referred to here as the “Leaching Framework,” or Framework. The Leaching Framework consists of a tiered approach to leaching assessment. The generalapproach under the Leaching Framework is to use laboratory testing to measure intrinsic leaching characteristics of a material (i.e., liquid-solid equilibrium partitioning as a function of pH and LS ratio, mass transfer rates) and then use this information in conjunction with mass transfer models to estimate constituent release by leaching under specific management scenarios (e.g., landfilling). Unlike

8 Many factors are known or may reasonably be expected to af

fect waste constituent leaching. The solubility of many metal salts is well known to vary with pH; adsorption of metals to the waste matrix varies with pH; redox conditions may determine which metal salts are present in wastes; temperature may af fect reaction rates; water infiltration can af fect the leaching rate and also af fect leaching chemistry and equilibrium. 

### 12Characterization of Coal Combustion Residues

### other laboratory leaching tests, under this approach, laboratory testing is not intended to directly simulate or mimicfield conditions. Development work to-date on the Framework has focused on assessing metals leaching, and it includes equilibrium batch testing (over a range of pH and LS ratio values), dif fusion-controlled mass transfer, and percolation-controlled (column) laboratory test methods in conjunction with mass transfer models to estimate release for specific management scenarios based on testing results from a common set of leaching conditions. EP A

’ s OSW and ORD believe that this approach successfully addresses the concerns identified above because it seeks to consider the effect of key disposal conditions on constituent leaching and to understand the leaching chemistry of wastes tested. The following attributes of the Leaching Framework were considered as part of the selection process:



### • It will permit development of data that are comparable

across U.S. coal and CCR types;


### • It will permit comparison with existing laboratory and

field leaching data on CCRs;


### • It was published in the peer -reviewed scientific literature; 

### • On consultation with EP A

’ s OSW , it was recommended as the appropriate protocol based on review of the range of available test methods and assessment approaches; and


### • On consultation with the Environmental Engineering

Committee of the Science Advisory Board (June 2003), the Committee considered the Leaching Framework to be responsive to earlier SAB criticisms of EP A ’ sapproach to leaching evaluation and to be broadly applicable and appropriate for this study
. The complete summary of the SAB consultation is provided as Appendix A. For this study , the primary leaching tests used from the Leaching Framework were Solubility and Release as a Function of pH (SR002.1) and Solubility and Release as a Function of the Liquid-Solid Ratio (LS) (SR003.1). 9 

### These tests represent equilibrium-based leaching characterization.

9 LS refers to liquid to solid ratio (mL water/g CCR or L water/ kg CCR) occurring during laboratory leaching tests or under field conditions. SR002.1 is carried out at LS=10 with several parallel batch extractions over a range of pH, while SR003.1 iscarried out using several parallel batch extractions with deionized water at LS= 0.5, 1, 2, 5 and 10. Under field conditions, LS refers to the cumulative amount of water passing through the total mass of CCR subject to leaching. 

### The range of pH and LS ratio used in the leaching tests includes the range of conditions (pH and LS ratio) observed for current CCR management practices. Results of thesetests provide insights into the physical-chemical mechanisms controlling constituent leaching. When used in conjunction with mass transfer and geochemical speciationmodeling, the results can provide conservative but realistic estimates of constituent leaching under a variety of environmental conditions (pH, redox, salinity , carbonation) and management scenarios. Laboratory testing for leaching assessment was carried out at the U.S. EP A

National Risk Management Laboratory (Research T riangle Park, NC) with technical assistance from V anderbilt University
.

13Characterization of Coal Combustion Residues



### 14Characterization of Coal Combustion Residues



# 2. Materials and Methods
2.1. CCR Materials for Evaluation The CCR materials tested in this study include a reference fly ash and fly ashes collected by ADA-EnvironmentalSolutions from designated coal combustion facilities under contract for the Department of Energy’ s National Ener gy Technology Laboratory (NETL) field evaluation program of sorbent injection upstream of existing particulate control devices. This program represents the first time that P

AC has been injected on a lar ge scale for a period of several weeks as enhanced mercury control technology
. Allsix of the facilities evaluated in this report burn either lowsulfur bituminous coal (Brayton Point, Salem Harbor , Facility C, Facility L), sub-bituminous coal (Pleasant Prairie) or a sub-bituminous/low-sulfur bituminous coal blend ( S t. Clair) and have particulate control devices only (no SO 2 

### scrubbers). This facility configuration is representative of 75% of the coal-fired utilities in the U.S. The same commercial sorbent (Norit Americas FGD Carbon ) 10 

### was used for all of the tests using ACI. This sorbent has a sur
face area of approximately 600 m 2 

### /g and a mass-mean diameter of 18 μ m. The tests using B-PAC used sorbent obtained from Sorbent T echnologies Corp., with a surface area of 700 to 1070 m 2 

### /g and a mass-mean diameter of 19 μ m. Samples of fly ash were collected from each facilityunder conditions with the enhanced mercury control technology turned of f and in use.The facilities and associated CCRs reported here are described below
. Appendix B provides a schematic flow diagram for each facility
. T able 5 provides characteristics of the low-sulfur bituminous coal combusted at Brayton Point, Salem Harbor, Facility C and Facility L, the sub-bituminous coal combusted at Pleasant Prairie and the sub-bituminous/low-sulfur bituminous coal blend combusted at S t . Clair . Elemental composition by x-ray fluorescence and additional characteristics of the fly ashes from baseline

10 DARCO FGD carbon is currently sold under the trade name DARCO-HG
. 

### testing and testing with enhanced mercury control are provided in T able 6 and T able 7. For samples from Salem Harbor , the loss on ignition (LOI) is more than twice the total carbon content because of a relatively high fraction of uncombusted particulate in the CCR. Total content analyses for mercury, arsenic, cadmium, lead and selenium results are provided in T able 8. 

### 2.1.1. Reference Fly Ash The reference fly ash was obtained from the EP A, National Risk Management Research Laboratory (Research T riangle Park, NC). X-Ray Fluorescence (XRF) analysis shown in T

able 6 is typical of a Class F fly ash from an eastern bituminous coal. This fly ash was selected for this program because it was available in large quantities (approximately two 55-gallon drums) and it contained low mercury levels. The large quantity allows for inter -laboratory comparisons at a later date. The low mercury content was important totest the laboratories’ ability to close the mercury mass-balance around the leaching and thermal desorption studies in the limit case of very low mercury content. 

### 2.1.2. Facilities Using Injection of S tandard Activated Carbon 2.1.2.1. Brayton Point Brayton Point S tation (Somerset, MA) is operated by PG&E National Ener gy Group. This facility is composed of four fossil fuel fired units designated as Units 1, 2, 3, and 4. The test unit selected, unit 1, has a tangentially fired boiler rated at 245 MW . Brayton Point Unit 1 was chosenfor this evaluation because of its combination of firing lowsulfur bituminous coal with a cold-side ESP
. This configuration represents a wide range of coal-fired power plants located in the eastern U.S. (Senior et al., 2003a). The primary particulate control equipment consists of twoCS-ESPs in series, with an EPRICON flue gas conditioning system that provides SO 3 

### for fly ash resistivity control. 15R e f e r e n c e B r a y t o n P o i n t P l e a s a n t P r a i r i e S a l e m H a r b o r F a c i l i t y C E l e m e n t F l y ( A

v e r a g e % ) ( A v e r a g e % ) a ( A v e r a g e % ) ( A v e r a g e % ) ( A v e r a g e % ) B a s e l i n e w i t h A C I B a s e l i n e w i t h A C I B a s e l i n e w i t h A C I B a s e l i n e w i t h A C I A l 1 4
. 7 0 0 1 3
. 4 3 0 1 2
. 4 0 0 1 0
. 0 5 0 1 0
. 2 2 0 9
. 5 2 3 7
. 6 2 3 1 2
. 2 5 8
. 9 6 A s 0
. 0 1 0 B M L b B M L B M L B M L B M L B M L B M L B M L B a 0
. 1 1 0 0
. 0 1 0 0
. 0 9 5 0
. 6 9 5 0
. 6 4 7 0
. 0 9 1 0
. 0 9 9 0
. 2 0 6 0
. 1 4 8 B r B M L 0
. 0 0 5 0
. 0 6 5 B M L B M L B M L B M L 0
. 0 0 2 5 0
. 0 0 9 7 C a 0
. 8 6 0 6
. 0 8 0 2
. 0 3 0 1 8
. 4 3 0 1 6
. 6 4 0 1
. 2 9 8 0
. 8 0 3 2
. 0 7 1
. 9 2 C l 0
. 0 2 6 0
. 0 3 0 0
. 4 4 0 B M L
. 0
. 0 4 5 0
. 1 0 1 0
. 2 0 3 0
. 0 3 7 3 0
. 0 7 9 0 C r 0
. 0 1 7 0
. 0 2 2 0
. 0 1 8 0
. 0 1 6 0
. 0 1 3 0
. 0 1 1 0
. 0 1 2 0
. 0 1 7 7 0
. 0 1 3 4 C u 0
. 0 1 8 0
. 0 2 2 0
. 0 2 0 0
. 0 2 2 0
. 0 2 2 0
. 0 0 7 0
. 0 0 8 0
. 0 2 4 7 0
. 0 1 7 9 F e 5
. 1 1 0 4
. 6 5 0 2
. 5 0 0 4
. 3 1 0 4
. 2 8 0 4
. 8 7 0 3
. 6 3 0 7
. 4 3 5
. 9 0 I B M L B M L 0
. 0 1 4 B M L B M L B M L B M L B M L B M L K 2
. 4 6 0 1
. 8 5 3 1
. 5 0 0 0
. 3 7 1 0
. 4 5 5 1
. 2 5 0 0
. 9 7 7 1
. 8 4 1
. 3 4 M g 0
. 6 3 7 0
. 8 0 0 0
. 6 4 1 2
. 8 1 0 2
. 4 6 0 1
. 7 8 5 0
. 4 2 0 1
. 6 7 9 0
. 5 8 6 M n 0
. 0 1 5 0
. 0 4 1 0
. 0 2 0 0
. 0 5 7 0
. 0 2 0 0
. 0 4 5 0
. 0 2 1 0
. 0 1 9 6 0
. 0 1 7 9 P a r a m e t e r B r a y t o n P o i n t P l e a s a n t P r a i r i e S a l e m H a r b o r F a c i l i t y C S t . C l a i r F a c i l i t y L C o a l L o w - s u l f u r B i t u m i n o u s

( 2 0 0 2 ) a P R B b S u b b i t u m i n o u s ( 2 0 0 2 ) L o w - s u l f u r B i t u m i n o u s ( 2 0 0 2 ) L o w - s u l f u r B i t u m i n o u s P R B S u b b i t u m i n o u s / L o w - s u l f u r B i t u m i n o u s ( 8 5 : 1 5 ) B l e n d L o w - s u l f u r b i t u m i n o u s S u l f u r , w t % 0
. 7 0
. 3 0
. 6 7 1
. 2 4 N T c N T A s h , w t % 1 0
. 8 5
. 1 6
. 4 8 1 4
. 7 8 N T N T M o i s t u r e , w t 4
. 7 3 0
. 7 9
. 0 5 6
. 8 5 N T N T H H V d , B t u / l b 1 2 , 7 8 0 8 , 3 8 5 1 2 , 4 2 0 1 1 , 9 0 2 N T N T H g , : g / g 0
. 0 4 4 0
. 1 0 9 0
. 0 6 1 7 0
. 1 3 6 N T N T C l , : g / g 1 4 7 5 8
. 1 6 4
. 3 1 6 9 N T N T A s , : g / g 5
. 6 8 N T 2
. 4 N T N T N T C d , : g / g 0
. 0 5 5 N T 0
. 1 4 N T N T N T P b , : g / g 8
. 9 N T 3
. 8 N T N T N T S e , : g / g 3 N T 4
. 8 N T N T N T P a r t i c u l a t e C o n t r o l D e v i c e 2 C S - E S P s i n s e r i e s C S - E S P C S - E S P H S - E S P + C O H P A C C S - E S P H S - E S P S o r b e n t I n j e c t i o n P o i n t B e t w e e n t h e 2 E S P s B e f o r e E S P B e f o r e E S P B e t w e e n H S - E S P a n d C O H P A C B e f o r e S o u t h S i d e E S P B e f o r e B - S i d e E S P S O X a n d N O X C o n t r o l e N A N A S N C R N A N A S e p a r a t e d O v e r f i r e A i r P o r t s S a m p l i n g L o c a t i o n A s h H o p p e r R o w C E S P H o p p e r 1 a n d 2 C o m p o s i t e E S P H o p p e r A B - S i d e H o p p e r N o r t h a n d S o u t h s i d e H o p p e r s A - a n d B - s i d e H o p p e r s a Y e a r o v e r w h i c h c o a l s a m p l e d t o o b t a i n a v e r a g e v a l u e s . b P R B = P o w d e r R i v e r B a s i n . c N T = n o t t e s t e d
. d H H V = h i g h e r h e a t i n g v a l u e . e N A = n o t a p p l i c a b l e . Characterization of Coal Combustion Residues Ta b l e 5 . Char acter istics of Coal Comb usted and F acilities Sampled and Repor ted Here (Senior et al., 2003a, Senior et al., 2003b , Senior et al., 2004).

­ ­

T

a ble 6. Fly Ashes from Br a yton P oint, Pleasant Prair ie , Salem Harbor , and Facility C: Elemental Composition (b y x-r a y fluorescence) and Other Char acter istics
.



### continued 16Reference Brayton Point Pleasant Prairie Salem Harbor Facility C Element Fly (Average%) a (Average%) (Average%) (Average%) (Average%) Baseline with ACI Baseline with ACI Baseline with ACI Baseline with ACI

R e f e r e n c e S t . C l a i r F a c i l i t y C E l e m e n t F l y ( A

v e r a g e % ) ( A v e r a g e % ) a ( A v e r a g e % ) B a s e l i n e w i t h B P A C B a s e l i n e w i t h B P A C A l 1 4
. 7 0 0 1 0
. 6 3 1 0
. 1 6 1 3
. 1 9 1 3
. 1 5 A s 0
. 0 1 0 B M L b B M L B M L B M L B a 0
. 1 1 0 1
. 2 0 1
. 0 1 0
. 0 6 5 2 0
. 0 6 3 2 B r B M L B M L 0
. 0 9 6 2 B M L 0
. 0 0 6 1 C a 0
. 8 6 0 1 2
. 0 6 1 1
. 3 5 0
. 3 2 8 0
. 3 1 9 C l 0
. 0 2 6 0
. 0 1 5 6 0
. 0 4 1 2 0
. 0 3 8 9 0
. 0 3 3 9 C r 0
. 0 1 7 0
. 0 1 1 6 0
. 0 1 0 9 0
. 0 1 4 7 0
. 0 1 4 7 C u 0
. 0 1 8 0
. 0 1 7 0 0
. 0 1 4 8 0
. 0 1 0 0 0
. 0 0 9 3 F e 5
. 1 1 0 5
. 3 5 5
. 5 2 2
. 3 9 2
. 3 6 I B M L B M L 0
. 0 1 4 B M L B M L K 2
. 4 6 0 0
. 7 9 4 0
. 7 6 8 2
. 2 7 2
. 2 2 Characterization of Coal Combustion Residues Table 6 (concluded). Fly Ashes from Brayton Point, Pleasant Prairie, Salem Harbor, and Facility C: Elemental Composition (by x-ray fluorescence) and Other Characteristics.

N a 0
. 3 4 6 0
. 5 1 1 0
. 2 4 2 1
. 6 6 0 1
. 3 1 0 0
. 2 7 0 0
. 2 9 3 0
. 3 7 4 0
. 2 8 7 N i 0
. 0 1 1 0
. 0 1 5 0
. 0 1 6 0
. 0 0 6 0
. 0 0 6 0
. 0 0 9 0
. 0 0 9 0
. 0 1 7 3 0
. 0 1 4 9 P b 0
. 0 0 8 B M L 0
. 0 1 0 B M L B M L 0
. 0 0 5 B M L 0
. 0 0 6 6 0
. 0 0 3 7 p X c 0
. 0 8 7 0
. 1 6 1 0
. 0 4 2 0
. 0 5 6 0
. 5 0 8 0
. 0 8 6 0
. 0 5 7 0
. 3 0 3 0
. 1 8 4 S e B M L 0
. 0 0 5 0
. 0 2 0 B M L B M L 0
. 0 0 5 0
. 0 0 5 0
. 0 1 5 7 0
. 0 4 8 7 S i 2 6
. 4 0 0 2 3
. 0 8 0 2 3
. 2 4 0 1 6
. 6 0 0 1 6
. 2 5 0 2 1
. 8 9 8 2 3
. 4 6 8 1 7
. 4 8 1 2
. 9 2 S r 0
. 0 8 9 0
. 1 2 4 0
. 0 8 3 0
. 3 6 9 0
. 3 4 1 0
. 0 4 2 0
. 0 3 2 0
. 1 4 3 0
. 1 0 4 S d B M L B M L B M L B M L B M L B M L B M L B M L B M L S X e 0
. 1 7 4 0
. 3 5 1 0
. 5 8 2 0
. 6 3 5 0
. 9 7 1 0
. 3 3 5 0
. 7 6 1 0
. 5 4 4 1
. 1 8 T i 0
. 8 9 7 1
. 0 1 5 0
. 1 0 0 0
. 9 6 4 0
. 9 4 3 0
. 4 5 3 0
. 4 0 7 0
. 7 0 9 0
. 5 7 4 V 0
. 0 3 1 0
. 0 4 3 0
. . 3 2 0
. 0 3 0 0
. 0 3 3 0
. 0 2 9 0
. 0 3 0 0
. 0 4 1 1 0
. 0 3 2 2 Z n 0
. 0 2 3 0
. 0 2 1 0
. 0 1 1 0
. 0 0 9 0
. 0 1 0 0
. 0 1 3 0
. 0 1 3 0
. 0 1 3 9 0
. 0 1 0 5 Z r 0
. 0 5 0 0
. 0 3 1 0
. 0 3 1 0
. 0 3 5 0
. 0 3 5 0
. 0 1 9 0
. 0 1 9 0
. 0 2 4 5 0
. 0 2 0 2 P h y s i c a l P a r a m e t e r s T

o t a l C a r b o n 0
. 7 6 2
. 3 1 3 0
. 2 5 3
. 6 7
. 8 1 1 1 0
. 9 2 4
. 4 4 S u r f a c e A r e a f 1
. 3 6 6
. 5 9 2 1
. 8 2 3 2 8 3 6 1 4
. 1 0 3 6
. 5 5 ( m 2 / g ) L O I ( w t % ) 0
. 8 5 5
. 5 1 2 0
. 6 0 3
. 5 2 1 2 5 1 8
. 0 3 6
. 2 6 a U n l e s s o t h e r w i s e n o t e d
. b B M L = b e l o w m e t h o d l i m i t ( A s < 0
. 0 0 9 % , I < 0
. 0 0 6 % , P b < 0
. 0 0 3 % , S e < 0
. 0 0 3 % )
. c P X = p h o s p h o r u s i n o x i d i z e d f o r m s u c h a s p h o s p h a t e . d S = s u l f u r i n e l e m e n t a l f o r m . e S X = s u l f u r i n o x i d i z e d f o r m s u c h a s s u l f a t e . f B r u n a u e r , E m m e t t , a n d T e l l e r m e t h o d f o r q u a n t i f y i n g s u r f a c e a r e a .
T

a b le 7. Fly Ashes from St. Clair and Facility L: Elemental Composition (b y x-r a y fluorescence) and Other Char acter istics
.



### continued 17Table 7 (concluded). Fly Ashes from St. Clair and Facility L: Elemental Composition (by x-ray fluorescence) and Other Characteristics. Reference St. Clair Facility C a Element Fly (Average%) (Average%) (Average%) Baseline with BPAC Baseline with BPAC

S a m p l e I D M e r c u r y ( n g / g ) M e r c u r y ( t h e r m a l )

( n g / g ) A r s e n i c ( : g / g ) C a d m i u m ( : g / g ) L e a d ( : g / g ) S e l e n i u m ( : g / g ) B r a y t o n P o i n t B a s e l i n e 6 5 0
. 6 ! 6
. 8 5 8 2
. 2 ! 2
. 1 8 0
. 5 ! 1
. 9 B M L a 1 1 7
. 3 ! 4
. 9 5 1
. 4 ! 1
. 7 B r a y t o n P o i n t w i t h A C I 1 5 2 9
. 6 ! 1
. 1 1 4 1 4
. 1 ! 4 3
. 7 2 7
. 9 ! 2
. 1 B M L 8 2
. 9 ! 2
. 3 1 5 1
. 9 ! 6
. 2 P l e a s a n t P r a i r i e B a s e l i n e 1 5 7
. 7 ! 0
. 2 1 4 6
. 9 ! 3
. 9 2 1
. 3 ! 0
. 3 B M L 4 1
. 6 ! 0
. 8 B M L P l e a s a n t P r a i r i e w i t h A C I 1 1 8 0 ! 1
. 2 1 1 7 6
. 8 ! 1 6
. 4 2 4
. 0 ! 0
. 8 B M L 4 7
. 0 ! 0
. 3 B M L S a l e m H a r b o r B a s e l i n e 5 2 8
. 5 ! 5
. 3 5 7 3
. 8 ! 8
. 7 2 5
. 9 ! 0
. 0 N T b 2 4
. 9 ! 1
. 4 4 1
. 9 ! 0
. 1 S a l e m H a r b o r w i t h A C I 4 1 1
. 5 ! 1 2
. 6 4 5 4
. 0 ! 1 2
. 1 2 6
. 0 ! 0
. 0 N T 2 4
. 0 ! 0
. 0 4 4
. 0 ! 0
. 0 F a c i l i ty C B a s e l i n e 1 5
. 8 ! 0
. 9 1 0
. 5 ! 0
. 7 9 3
. 6 ! 5
. 5 N T 5 5
. 8 ! 0
. 7 B M L F a c i l i ty C w i t h A C I 1 1 5 0
. 7 ! 1 4 1 0 9 0
. 1 ! 2 4
. 1 5 0 6
. 3 ! 2 8
. 7 N T 1 1 4
. 4 ! 5
. 8 2 0 6
. 3 ! 0
. 9 Characterization of Coal Combustion Residues

M g 0
. 6 3 7 3
. 0 7 2
. 9 2 0
. 5 8 4 0
. 5 8 0 M n 0
. 0 1 5 0
. 0 3 5 0 0
. 0 3 1 4 0
. 0 0 8 8 0
. 0 0 8 5 N a 0
. 3 4 6 4
. 6 6 4
. 0 9 0
. 1 3 4 0
. 1 3 2 N i 0
. 0 1 1 0
. 0 0 7 4 0
. 0 0 6 4 0
. 0 1 0 9 0
. 0 1 0 9 P b 0
. 0 0 8 0
. 0 0 4 5 0
. 0 0 4 0 0
. 0 0 4 6 0
. 0 0 4 6 p X c 0
. 0 8 7 0
. 2 1 9 0
. 1 6 9 0
. 0 2 6 2 0
. 0 2 4 0 S e B M L B M L 0
. 0 0 2 4 B M L B M L S i 2 6
. 4 0 0 1 6
. 6 5 1 7
. 0 0 2 4
. 7 5 2 4
. 8 S r 0
. 0 8 9 0
. 5 6 5 0
. 5 1 7 0
. 0 3 2 2 0
. 0 3 2 2 S d B M L B M L B M L B M L B M L S X e 0
. 1 7 4 1
. 2 3 1
. 0 3 B M L B M L T i 0
. 8 9 7 0
. 7 5 9 0
. 7 1 3 0
. 8 8 2 0
. 8 7 8 V 0
. 0 3 1 0
. 0 2 9 2 0
. 0 2 5 7 0
. 0 2 3 2 0
. 0 2 3 3 Z n 0
. 0 2 3 0
. 0 1 0 4 0
. 0 0 7 7 0
. 0 0 7 5 0
. 0 0 6 5 Z r 0
. 0 5 0 0
. 0 2 7 4 0
. 0 2 8 3 0
. 0 2 8 4 0
. 0 2 7 7 P h y s i c a l P a r a m e t e r s T

o t a l C a r b o n 0
. 7 6 0
. 1 6 2
. 6 5 5
. 5 6 5
. 9 2 S u r f a c e A r e a f 1
. 3 6 2
. 5 0 2 4
. 8 6 8
. 2 3 2 7
. 0 1 ( m 2 / g ) L O I ( w t % ) 0
. 8 5 0
. 4 1 3
. 1 9 1 2
. 2 8 1 2
. 3 8 a U n l e s s o t h e r w i s e n o t e d
. b B M L = b e l o w m e t h o d l i m i t ( A s < 0
. 0 0 9 % , I < 0
. 0 0 6 % , P b < 0
. 0 0 3 % , S e < 0
. 0 0 3 % )
. c P X = p h o s p h o r u s i n o x i d i z e d f o r m s u c h a s p h o s p h a t e . d S = s u l f u r i n e l e m e n t a l f o r m . e S X = s u l f u r i n o x i d i z e d f o r m s u c h a s s u l f a t e . f B r u n a u e r , E m m e t t , a n d T e l l e r m e t h o d f o r q u a n t i f y i n g s u r f a c e a r e a .
T

a ble 8. CCRs from Facilities with Electrostatic Precipitators: T otal Content of Mercur y , Arsenic , Cadmium, Lead and Selenium. [All analyses are according to EP A Method 3052, e x cept f or mercur y (ther mal), which is b y EP A Method 7473 (EP A, 1998b)].



### continued 18S t
. C l a i r B a s e l i n e 1 1 0
. 9 ! 5
. 8 N T 4 3
. 4 ! 2
. 6 1
. 4 ! 0
. 1 4 6
. 3 ! 1 7
. 9 1 0
. 7 ! 0
. 1 S t
. C l a i r w i t h B - P A C 1 1 6 3
. 0 ! 8
. 9 N T 4 0
. 8 ! 1
. 1 1
. 3 ! 0
. 1 3 4
. 9 ! 1
. 7 1 2
. 6 ! 0
. 9 c F a c i l i ty L ( R u n 1 ) B a s e l i n e 1 3
. 0 ! 0
. 2 N T 2 0
. 0 ! 1
. 1 0
. 4 ! 0
. 0 4 4
. 8 ! 0
. 7 4
. 1 ! 0
. 1 c F a c i l i ty L ( R u n 1 ) w i t h B - P A C 3 7
. 7 ! 1
. 3 N T 1 8
. 7 ! 0
. 7 0
. 3 ! 0
. 0 4 2
. 2 ! 0
. 3 4
. 3 ! 0
. 2 F a c i l i ty L ( R u n 2 ) B a s e l i n e d 2 0
. 3 ! 0
. 1 4 N T 4 4
. 4 ! 1
. 1 0
. 6 ! 0
. 1 6 0
. 2 ! 3
. 8 3
. 0 ! 0
. 3 F a c i l i ty L ( R u n 2 ) w i t h B - P A C d 7 1
. 4 ! 0
. 0 3 N T 4 4
. 3 ! 1
. 4 0
. 9 ! 0
. 2 6 3
. 0 ! 2
. 8 4
. 3 ! 0
. 0 M D L 0
. 2 n g / g 0
. 1 4 5 n g / g 1
. 1 2 1
. 0 0
. 1 8 0
. 7 2 M i n i m u m Q u a n t i f i c a t i o n L i m i t 0
. 7 2 n g / g 1
. 0 n g / g 4
. 0 1 0
. 0 0
. 6 4
. 0 a B M L = b e l o w m e t h o d l i m i t
. b N T = n o t t e s t e d
. c P n e u m a t i c c o n t r o l s w e r e t u r n e d o ff f o r 4 h r t o c o l l e c t f l y a s h
. d P n e u m a t i c c o n t r o l s w e r e t u r n e d o ff f o r 3 0 m i n t o c o l l e c t f l y a s h
. N o t t e s t e d f o r l e a c h i n g . Characterization of Coal Combustion Residues Table 8 (concluded). CCRs from Facilities with Electrostatic Precipitators:Total Content of Mercury, Arsenic, Cadmium, Lead, and Selenium. [All analyses are according to EPA Method 3052, except for mercury (thermal), which is by EPA Method 7473 (EPA, 1998b)]. Sample ID M ( e n

r g c / u g r

) y ( M th

e e r r c m ur

a y l) A ( r : s g e / n g i

) c Ca ( :

d g

m

/g

iu

) m ( L : e

g

a /g

d

) Se ( :

le

g n /g iu

) m (ng/g)



### The EPRICON system is not used continuously , but on an as-needed basis. The first ESP(“Old ESP”) in this particu
lar configuration was designed and manufactured by Koppers. The Koppers ESPhas a weighted wire design and a specific collection area (SCA) of 156 ft 2 

### /1000 acfm. The second ESP (“New ESP”) in the series configuration was designed and manufactured by Research-Cottrell. The second ESP has a rigid electrode design and an SCA of 403 ft 2 

### /1000 acfm. T otal SCA for the unit is 559 ft 2 

### /1000 acfm. The precipitator inlet gas temperature is nominally 280 E F at full load (Senior et al., 2003a). Hopper ash is combined between both precipitators in the dry ash-pull system. The ash is processed by an on-site Separation T echnology Inc. (STI) carbon separation sys
tem, to reduce the carbon content. This processed ash is sold as base for concrete and the remainder of the higher carbon ash is land disposed (Senior et al., 2003a). The injection rate of the P AC was 20 lb of sorbent used for each million actual cubic feet of gas (lb/MMacf) at the time when the CCR with ACI in use was collected from this facility
. The baseline and post-control ashes used for this study were collected as composite samples from the C-row ash hop
pers of the new ESP before processing for carbon separa
tion. 11 

### The baseline ash was collected on 6 June 2002. The post-control fly ash was collected on 21 July 2002. Both

11 Ash for this study was collected before processing for carbon separation because not all facilities do this processing. 

### fly ashes were stored in covered five gallon buckets in the onsite trailer at ambient temperatures. 

### 2.1.2.2. Pleasant Prairie W isconsin Electric Power Company , a subsidiary of W is
consin Energy , owns and operates Pleasant Prairie Power Plant located near Kenosha, WI. The plant has two 600 MW balanced-draft coal-fired boilers designated Units 1 and 2. Unit 2 is the test unit. This site was of key interest because it was the only plant in the NETL program that burns a variety of Powder River Basin (PRB) low sulfur , sub-bituminous coals. In addition, this facility has the abil
ity to isolate one ESP chamber (1/4 of the unit) (S tarns et al., 2002).The primary particulate control equipment consists of CSESPs of weighted wire design with a W ahlco gas condi
tioning system that provides SO 3 

### for fly ash resistivity con
trol. The precipitators were designed and built by ResearchCottrell. The design flue gas flow was 2,610,000 acfm. The precipitator inlet gas temperature is nominally 280 E F at full load (S tarns et al., 2002). Precipitator #2 is comprised of four electrostatic precipita
tors that are arranged piggyback style and designated 2-1, 2-2, 2-3, and 2-4. Each of the four precipitators is two cham
bers wide and four mechanical fields deep with eight elec
trical fields in the direction of gas flow
. The SCA is 468 ft 2 

### /kacfm (S tarns et al., 2002). Hopper ash is combined from all four precipitators in the dry ash-pull system and sold as base for concrete (S tarns et al., 2002). 19Characterization of Coal Combustion Residues 

### The P AC injection rate was 10 lb/MMacf at the time when the CCR with ACI in use was collected from this facility
. The baseline ash was collected as a composite sample from ash hoppers 7-1 and 7-2 of ESP2-4. The post-control ash was collected as a grab sample from ash hopper 7-2 of E S P2-4 (see Appendix B for flow diagram). The baseline ash was collected on 1 1 September 2001, and the postcontrol fly ash was collected on 13 November 2001. Both fly ashes were stored in covered five gallon buckets in the onsite trailer at ambient temperatures. 

### 2.1.2.3. Salem Harbor PG&E National Energy Group owns and operates Salem Harbor S tation located in Salem, MA. There are four fossil fuel fired units at the facility designated as Units 1, 2, 3, and 4. Units 1–3 fire a low sulfur , bituminous coal and use oil for startup. Unit 4 fires #6 fuel oil. Unit 1, the test unit, is a B&W single-wall-fired unit with twelve DB Riley CCV
90 burners. It is rated at 88 gross MW . Salem Harbor Unit 1 was chosen for this evaluation because of its combina
tion of firing low-sulfur bituminous coal with urea-based SNCR, high LOI, and a CS-ESP
. The opportunity to quan
tify the impact of SNCR on mercury removal and sorbent ef

fectiveness is unique in this program. In addition, test results from prior mercury tests have indicated 87% to 94% mercury removal ef ficiency on this unit without sorbent injection (Senior et al., 2003a). However , fly ash from this facility has a relatively high percentage of total carbon without carbon injection (7.8%, see T able 6), which likely serves as a sorbent for mercury
. The particulate control equipment consists of a two-cham
ber CS-ESP (chambers designated 1-1 and 1-2), which pro
vides two separate gas flow paths from the outlet of the tubular air heaters to the ID fan inlets. This Environmental Elements ESP has a rigid electrode design and a SCA of 474 ft 2 

### /1000 acfm. The precipitator inlet gas temperature is nominally 255 E F at full load. T ypical LOI or carbon content of the Unit 1 ash is about 25%. This ash is landfilled. The P AC injection rate was 10 lb/MMacf at the time when the CCR with ACI in use was collected from this facility
. The baseline and post-control ashes used for this study were collected as grab samples from the first ash hopper (hop
per A) of row 1-1 of the ESP
. The baseline ash was col
lected on 6 June 2002, and the post-control fly ash was collected on 7 July 2002. Both fly ashes were stored in covered five gallon buckets in an onsite trailer at ambient temperatures. 

### 2.1.2.4. Facility C This plant has four 270 MW balanced draft coal-fired boil
ers designated as Units 1–4. All of these units fire a variety of low-sulfur , washed, Eastern bituminous coals. Unit #3 was used for the ACI studies. All of the units at this plant employ HS-ESP as the pri
mary particulate control equipment. The HS-ESPof unit #3 is followed by COHP AC. The COHP AC system is a pulse-jet cleaned baghouse designed to treat flue gas vol
umes of 1,070,000 acfm at 290 E F . The COHP AC baghouse consist of two sides, with the A-side being the control and the B-side being the side where activated carbon was in
jected after the HS-ESPbut before the COHP AC. An ESP followed by COHP AC and combined with sorbent injec
tion is referred to as the T OXECON configuration. The injection rate of the P AC was 1.5 lb/MMacf at the time when the CCR with ACI in use was collected from this facility
. 

### 2.1.3. Facilities Using Injection of Brominated Activated Carbon 2.1.3.1. S t. Clair Detroit Energy S t. Clair Power Plant Unit #1 is a 160 MW boiler that typically burns a 85:15 blend of PRB and bitu
minous coals. 12 

### The flue gas from the boiler splits and is directed into two parallel CS-ESPs (designated the “South ESP” and the “North ESP”, each treating half of the flue gas). The flue gas is then recombined before exiting the stack. During testing, B-P AC was injected upstream of the South ESP
. The unit has no NO X

### or SO 2 

### controls. The injection rate of the B-P AC was 5 lb/MMacf at the time when the CCR with B-P AC in use was collected from this facility
. 

### 2.1.3.2. Facility L This facility is configured similarly to S t. Clair except that it used one HS-ESP with two compartments rather than two CS-ESPs, and it uses separated overfired air (SOfA) ports for NO X 

### control. As a result, the fly ash collection temperature is between 300 and 450 E F . Samples were col
lected from hoppers which were evacuated under negative

12 The unit sometimes switches to 100% PRB on the weekends. However , during our flue gas/fly ash sampling, the unit was burning the PRB/bituminous blend. 

### 20Characterization of Coal Combustion Residues 

### pressure. The pneumatic hopper controls were turned of fto allow enough samples to collect for the leaching evaluation. The controls were of f for about 4 hr
. There is concern that because of the high temperature within the fly ash collection hoppers, some mercury may have desorbed prior to sampling. Therefore, the samples obtained for evaluation may have a lower metal content. Because of theconcern about mercury desorbing from the fly ash, additional fly ash was collected by turning of f the pneumatic transfer for 30 min (2 weeks after the original samples were collected). Total metal content determinations were completed for all samples, which includes with and without BP

AC for fly ash collected after accumulation in the hopper for 4 hr (first sampling) and 30 min (second sampling). The leaching evaluation was conducted only on the samples collected over 4 hr intervals since this provided adequate sample size (5 gallons). 

## 2.2. Leac hing Assessment Pr otocols Laboratory testing for this study focused on leaching as a function of pH and LS ratio as defined by the Leaching Framework. This is considered T ier 2 testing (equilibriumbased) for detailed characterization, which was selected to establish baseline CCR characteristics. Mass transfer rate testing (T ier 3, detailed characterization) may be carriedout in the future for specific cases where results from equilibrium-based characterization indicate a need for detailed assessment. 

### 2.2.1. Alkalinity , Solubility and Release as a Function of pH (SR002.1) Alkalinity , solubility , and release as a function of pH were determined according to method SR002.1 (Kosson et al., 2002). This protocol consists of 1 1 parallel extractions of particle size reduced material at a liquid-to-solid ratio of10 mL extractant/g dry sample. Particle size reduction facilitates achieving equilibrium, but minimal size reduction was required for the samples evaluated in this study . Each extraction condition was carried out in triplicate using 40 g of material for each material evaluated. In addition, three method blanks were included, consisting of the deionized water , nitric acid and potassium hydroxide used for extractions. T ypical particle size of the tested materials was less than 300 μ m. An acid or base addition schedule is formulated based on initial screening for eleven extracts with final solution pH values between 3 and 12, through addition of aliquots of nitric acid or potassium hydroxide as needed. The exact schedule was adjusted based on the nature of the material; however , the range of pH values included the natural pH of the matrix that may extend the pH domain (e.g., for very alkaline or acidic materials). The final LS ratio is 10 mL extractant/g dry sample, which includes DI water, the added acid or base, and the amount of moisture that is inherent to the waste matrix as determined by moisture content analysis. The eleven extractions were tumbled in an end-over -end fashion at 28±2 rpm for 24 hr followed by filtration separation of the solid phase from the extract using a 0.45 μ m polypropylene filter . Each extract then was analyzed for constituents of interest. The acid and base neutralization behavior of the materials was evaluated by plotting the pH of each extract as a function of equivalents of acid or base added per gram of dry solid. Concentration of constituents of interest for each extract was plotted as a function of extract final pH to provide liquid-solid partitioning equilibrium as a function of pH. 

### 2.2.2. Solubility and Release as a Function of LS Ratio (SR003.1) Solubility and release as a function of LS ratio was deter
mined according to method SR003.1 (Kosson et al., 2002). This protocol consists of five parallel batch extractions over a range of LS ratios (i.e., 10, 5, 2, 1, and 0.5 mL/g dry material), using DI water as the extractant with aliquots of material that has been particle size reduced. T ypical par
ticle size of the material tested was less than 300 μ m. Between 40 and 200 g of material, based on the desired LS ratio, were used for each extraction. All extractions were conducted at room temperature (20 ± 2 E C) in leak-proof vessels that were tumbled in an end-over -end fashion at 28±2 rpm for 24 hr . Following gross separation of the solid and liquid phases by centrifugation or settling, leachate pH and conductivity measurements were taken, and the phases were separated by pressure filtration using 0.45 μ m polypropylene filter membrane. The five leachates werecollected and preserved, as appropriate, for chemical analysis. Each extraction condition was carried out in triplicate and a method blank consisting of the DI water used for extraction was included. 

## 2.3. Anal ytical Methods 2.3.1. Surface Area and Pore Size Distribu tion A

Quantachrome Autosorb IC-MS was used to perform 5­ point Brunauer , Emmett, and T eller (BET) method surface area, pore volume, and pore size distribution analysis on each as-received and size-reduced CCR. A 200 mg sample was degassed under vacuum at 200 E C for at least 1 hr in the sample preparation manifold prior to analysis with N 2 

### as the analysis gas. S tandard materials with known surface area were routinely run as a QC check. 21Characterization of Coal Combustion Residues 

### 2.3.2. pH and ConductivityConductivity and pH were measured for all aqueous extracts using an Accumet 925 pH/ion meter
. The pH of the leachates was measured using a combined pH electrode accurate to 0.1 pH units. A 3-point calibration was per
formed using pH buf fer solutions at pH 4.0, 7.0, and 10.0.Conductivity of the leachates was measured using a standard conductivity probe. The conductivity probe was calibrated using appropriate standard conductivity solutions for the conductivity range of concern. Conductivity meters typically are accurate to ±1% and have a precision of ±1%. 

### 2.3.3. Moisture Content Moisture content of the “as received” CCRs, was deter
mined using American Society for T esting and Materials (ASTM) method D 2216-92. This method supercedes theone indicated in the published version of the leaching procedure. 

### 2.3.4. Carbon Content: Organic Carbon/ Elemental Carbon Analyzer Organic carbon (OC) and elemental carbon (EC) content of each CCR tested was measured using a Sunset Lab ther
mal-optical EC/OC analyzer using NIOSH Method 5040. The sample, collected on quartz fiber filters, was heated under a completely oxygen-free helium atmosphere in a quartz oven in four increasing temperature steps (375, 540, 670, and 870 E C) at 60 s ramp times for the first threetemperatures and a 90 s ramp time for the final temperature. This removed all or ganic carbon on the filter
. As the or ganic compounds were vaporized, they were immediately oxidized to carbon dioxide in an oxidizer oven that followed the sample oven. The flow of helium containing the produced carbon dioxide then went to a quartz methanator oven where the carbon dioxide was reduced to methane, which was then detected by a flame ionization detector (FID). After the sample oven was cooled to 525 E C, the pure helium eluent was switched to an oxygen/ helium mixture in the sample oven. At that time, the sample oven temperature was stepped up to 850 E C. During this phase, both the original elemental carbon and the residual carbon produced by the pyrolysis of organic compounds during the first phase were oxidized to carbon dioxide by the presence of oxygen in the eluent. The carbon dioxide was then converted to methane and detected by the FID. After all carbon had been oxidized from the sample, a known volume and concentration of methane was injected into the sample oven, so each sample was calibrated to a known quantity of carbon. This also provided a means of checking the operation of the instrument. The calibration range for these analyses was from 10 to 200 μ g/cm 2 

### of carbon using a sucrose solution as the standard. The detection limit of this instrument is approximately 100 ng/cm 2 

### with a linear dynamic range from 100 ng/cm 2 

### to 1 g/cm 2


### . 

### 2.3.5. Mercury (CV AA, Method 3052, and Method 7473) Liquid samples were preserved for mercury analysis by additions of nitric acid and potassium permanganate and then prepared prior to analysis according to the following method. For each 87 mL of sample, 3 mL of concentratednitric acid and 5 mL of 5 wt% aqueous potassium permanganate solution were added prior to storage. Immediately before cold vapor atomic absorption (CV AA) analysis, 5 mL of hydroxylamine were added to clear the sample, and the sample was then digested according to ASTM MethodD6784-02 (Ontario Hydro) as described for the permanganate fraction. On completion of the digestion, the sample was analyzed for mercury by CV AA. Samples with known additions of mercury for matrix analytical spikes also were digested as described above prior to CV AA analysis. Sample preparation of the solids and filters was carried out by HF/HNO 3 

### microwave digestion according to Method 3052 followed by CV AA analysis as indicated above. No additional preservation or digestion was carried out prior to CV AA analysis. Mercury analysis of each digest, extract, and leachate was carried out by CV AA according to EP A

SW846 Method 7470A “Mercury in Liquid W aste (Manual Cold V apor T

echnique).” A Perkin Elmer FIMS 100 Flow Injection Mercury System was used for this analysis. The instrument was calibrated with known standards ranging from 0.025 to 1 μ g/L mercury . Solids also were analyzed by Method 7473 “Mercury in Solids and Solutions by Thermal Decomposition, Amalgamation, and Atomic Absorption Spectrophotometry” (EP A, 1998b). A Nippon MD-1 mercury system was used for this analysis. The instrument was calibrated with known standards ranging from 1 to 20 ng of mercury
. The method detection limit for mercury in solids is 0.145 mg/kg. 

### 2.3.6. Other Metals (ICP-MS, Method 3052 and Method 6020) Inductively coupled plasma-mass spectroscopy (ICP-MS) analyses for other elements of interest were carried out by V

anderbilt and STL laboratories. These two laboratories 22E l e m e n t M o d e I n t e r n a l S t a n d a r d M D L ( : g / L ) M L ( : g / L ) A s D R C 2 0 : g / L I n 0
. 6 4 3
. 0 P b S t a n d a r d 2 0 : g / L H o 0
. 3 1 1
. 0 S e D R C 2 0 : g / L I n 0
. 5 2 2
. 0 Characterization of Coal Combustion Residues 

### were used to provide inter -laboratory comparison for selected analyses. Liquid samples for ICP-MS analysis were preserved by addition of 3 mL of concentrated nitric acid (trace metal grade) per 97 mL of sample. Solid samples were digested by EP A

Method 3052 prior to ICP-MS analysis. Known quantities of arsenic, selenium, cadmium, and lead were also added to sample aliquots for analytical matrix spikes. 

### 2.3.6.1. ICP-MS Analysis at V anderbilt ICP-MS analyses carried out at Vanderbilt University (Department of Civil and Environmental Engineering) were completed using a Perkin Elmer model ELAN DRC II in both standard and dynamic reaction chamber (DRC) modes. S tandard analysis mode was used for Pb, and DRC mode with 0.6 mL/min of methane as the reaction gas was used for As and Se. Nine-point standard curves were used for an analytical range between approximately 0.1 and 500 μ g/L and completed daily
. Analytical blanks and analytical check standards at approximately 50 μ g/L were run every 10 samples and required to be within 10% of thespecified value. Samples for analysis were diluted gravimetrically to within the targeted analytical range using 1% v/v Optima grade nitric acid (Fisher Scientific). T ypically , analysis for As, Pb, and Se required 10:1 dilution. T wenty microliters of a 10 mg/L internal standard consisting of indium (In) (for As and Se) and holmium (Ho) (for Pb) was added to 10 mL of sample aliquot prior to analysis. Analytical matrix spikes were completed for As, Pb, and Se on one of each of the three replicate extracts from SR002.1. For each analytical matrix spike, 20 μ L of a 10mg/L standard solution was added to 10 mL of sample aliquot (ef fective concentration addition of 200 μ g/L). T able9 provides the element analyzed, analytical mode, corresponding internal standard, method detection limit (MDL), and minimum level of quantification (ML). 

### 2.3.6.2. Severn T rent Laboratories, Inc. (STL)STL (Savannah, GA) was selected as a commercial laboratory to carry out some of the ICP-MS analyses for this project. Analyses for As, Cd, Se, and Pb were performed
Ta b l e 9 . Detection Limits and Quality Control Inf or mation f or ICP-MS Analysis f or As , Pb , and Se at V anderbilt. 

### on an Agilent ICP-MS with octopole reaction system (ORS). Mixed calibration standards were prepared for each metal at five levels ranging from 0.5 μ g/L to 100 μ g/L. 

### 2.3.7. X-Ray Fluorescence (XRF)XRF analysis was performed on each CCR to provide additional information on its total elemental composition. For each CCR, two pellets were prepared as follows. Three grams of material was weighed and mixed with 1.5 mL(100 mg dry solids) of liquid binder to give a 32 mm diameter pellet weighing 3150 mg with a material-to-diluent ratio of 0.05. For high carbon content samples, 3.0 ml (100 mg dry solids) of liquid binder was used to give a 32 mm diameter pellet weighting 3300 mg with a material to diluent ratio of 0.1. XRF intensities were collected on each side of each pellet using Philips SuperQ data collection software and evaluated using Omega Data System’ s UniQuant 4 XRF “standardless” data analysis software. The UQ/Flyash calibration was used to analyze the samples. The pellets were evaluated as oxides. Known flyash S tandard Refer
ence Materials (SRMs) were also run to assess the accuracy of the analysis. This information is useful in supplementing CV AA and ICPresults. 

### 2.3.8. MDL and ML for Analytical Results The MDL is defined by 40 CFR Part 136, Appendix B, July 1, 1995, Revision 1.1 1 as “the minimum concentration of a substance that can be measured and reported with 99% confidence that the analyte concentration is greater than zero and is determined from analysis of a sample in a given matrix containing the analyte.” The MDL was determined statistically from data gener
ated by the analysis of seven or more aliquots of a spiked reagent matrix and verified by the analysis of calibration standards near the calculated MDLaccording to EP A (2003). The MDL then was determined by multiplying the standard deviation of the replicate measurements by the appropriate S tudents t value for a 99% confidence level (two tailed) and n -1 (six) degrees of freedom and also multiplying by the minimum dilution factor required for matrix preservation and analysis.The ML is defined by 40 CFR Part 136, 1994 as “the lowest level at which the entire analytical system must give a recognizable signal and acceptable calibration point for the analyte.” According to EP A

(2003), the ML is intended to be the nearest integer value (i.e., 1, 2 or 5×10 n , where n is an integer) to 10 times the standard deviation observed for determination of the MDL. This value is also multiplied by the minimum dilution factor required for preservation 23Characterization of Coal Combustion Residues

### and analysis of the sample matrix to obtain the ML reported here. Mercury , as measured by CV AA, required modification ofthe calculation of the MDL and ML because very consistent replication resulted in calculation of a MDL lower than the instrument detection limit. For this case, the standard deviation of seven replicate analyses of 0.025 μ g/L was 0.00069. Therefore, the MDLwas set equal to the instrument detection limit of 0.001 μ g/L times the minimum dilution factor from sample preparation (3.59) to result in an MDL of 0.0036 μ g/L. The ML was set to 10 times theinstrument detection limit and rounded to the nearest integer value as above. The resulting ML was 0.01 μ g/L. 

## 2.4. Quality Assurance V alidation 2.4.1. Homogenization of Individual CCR Samples and Aliquots for Analyses T

o ensure sample homogeneity the fly ashes were mixed using a Morse single can tumbler model 1-305 (Figure 5). This tumbler is designed to provide aggressive corner-over corner mixing at 23 RPM. Because the sample is tumbledat an angle it yields superior mixing to a conventional tumbler . Briefly , each fly ash was mixed by filling a 5 gal bucket to the half way mark and tumbled for 1 hr
. The bucket was then inverted and tumbled for another hour
.At the beginning of this program a series of test were conducted to ensure that the samples were being adequately

Figure 5. Mixing Fly Ash Pr ior to Obtaining Aliquots f o r Labor ator y Analyses
. 

### mixed. The reference fly ash was mixed as outlined above and 3 sub-samples taken from the top, middle and bottom respectively and XRF pellets prepared. The XRF results showed that the concentrations of 28 elements including calcium and silicon were consistent from sub-sample to sub-sample (T able 10) 

### 2.4.2. Leaching T est Methods and Analytical QA/QC One of the objectives of this project was to establish a QA/QC framework for the leaching assessment approach developed by Kosson et al. (2002). The developed QA/QC framework incorporates the use of blanks, spiked samples, and replicates, and Appendix C provides the complete Quality Assurance Project Plan. For each designated leaching test condition, triplicate leaching test extractions were obtained (i.e., three separate aliquots of CCR were each extracted at the designated test condition). The three types of method blanks were the deionized water case, the mostconcentrated nitric acid addition case, and the most concentrated potassium hydroxide addition case. Each method blank was carried through the entire protocol, including tumbling and filtration, except an aliquot of CCR was not added.During analysis for mercury and elemental species by ICPMS, analytical spikes for the constituents of interest werecarried out for one replicate of each test case to assess analytical recoveries over the complete range of pH and liquid matrix conditions. Using a standard obtained from a source dif ferent from the calibration standards, multipoint calibration curves using at least 7 standards and an initialcalibration verification (ICV) were completed daily or after every 50 samples, whichever was more frequent. Inaddition, instrument blanks and continuing calibration verification (CCV) standards were analyzed after every 10 analytical samples and required to be within 10 percent of the expected value. CCV standards and instrument blanks also were run at the end of each batch of samples. For both ICP-MS and CV AA analyses, each sample was analyzed along with a matrix spike, which is an aliquot ofthe sample plus a known spike concentration of the element of interest. The “spike recovery” should be within 80–120% of the expected value. 

### 2.4.3. Laboratory Mass Balance V erification for Leaching T est Methods Mass balance analysis around the SR002.1 Solubility and Release as a Function of pH leaching test procedure was used to demonstrate retention of Hg, As, Se, Cd, and Pb 24E l e m e n t # 1 ( % ) a # 2 ( % ) a # 3 ( % ) a M e a n ( % ) a S t a n d a r d D e v i a t i o n ( % ) a % R S D S i 2 6
. 4 1 2 6
. 4 1 2 6
. 4 3 2 6
. 4 1 6 7 0
. 0 1 1 5 4 7 0
. 0 4 A l 1 4
. 6 2 1 4
. 6 4 1 4
. 5 2 1 4
. 5 9 3 3 0
. 0 6 4 2 9 1 0
. 4 4 F e 5
. 3 1 5
. 2 9 5
. 3 8 5
. 3 2 6 7 0
. 0 4 7 2 5 8 0
. 8 9 K 2
. 4 3 2
. 4 4 2
. 4 6 2
. 4 4 3 3 0
. 0 1 5 2 7 5 0
. 6 3 T i 0
. 8 7 1 0
. 8 7 1 0
. 8 7 7 0
. 8 7 3 0 0
. 0 0 3 4 6 4 0
. 4 0 C a 0
. 8 3 4 0
. 8 4 7 0
. 8 3 5 0
. 8 3 8 7 0
. 0 0 7 2 3 4 0
. 8 6 M g 0
. 6 3 8 0
. 6 4 5 0
. 6 4 5 0
. 6 4 2 7 0
. 0 0 4 0 4 1 0
. 6 3 N a 0
. 3 5 1 0
. 3 5 2 0
. 3 4 0
. 3 4 7 7 0
. 0 0 6 6 5 8 1
. 9 2

b S X 0
. 1 7 2 0
. 1 6 4 0
. 1 7 2 0
. 1 6 9 3 0
. 0 0 4 6 1 9 2
. 7 3 c P X 0
. 0 8 3 4 0
. 0 8 5 4 0
. 0 8 8 1 0
. 0 8 5 6 0
. 0 0 2 3 5 9 2
. 7 5 B a 0
. 1 0 7 0
. 1 0 6 0
. 1 1 2 0
. 1 0 8 3 0
. 0 0 3 2 1 5 2
. 9 7 S r 0
. 0 8 4 6 0
. 0 8 4 6 0
. 0 8 5 0
. 0 8 4 7 0
. 0 0 0 2 3 1 0
. 2 7 Z r 0
. 0 5 0 9 0
. 0 4 8 6 0
. 0 5 2 0
. 0 5 0 5 0
. 0 0 1 7 3 5 3
. 4 4 V 0
. 0 2 4 3 0
. 0 2 3 6 0
. 0 2 3 4 0
. 0 2 3 8 0
. 0 0 0 4 7 3 1
. 9 9 Z n 0
. 0 2 1 9 0
. 0 2 4 3 0
. 0 2 5 0
. 0 2 3 7 0
. 0 0 1 6 2 6 6
. 8 5 E r 0
. 0 2 2 4 0
. 0 2 4 8 0
. 0 2 4 0
. 0 2 3 7 0
. 0 0 1 2 2 2 5
. 1 5 C u 0
. 0 1 7 3 0
. 0 1 7 3 0
. 0 2 0 5 0
. 0 1 8 4 0
. 0 0 1 8 4 8 1 0
. 0 6 C r 0
. 0 1 4 4 0
. 0 1 2 2 0
. 0 1 2 2 0
. 0 1 2 9 0
. 0 0 1 2 7 9
. 8 2 Y 0
. 0 1 6 2 0
. 0 1 5 3 0
. 0 1 5 4 0
. 0 1 5 6 0
. 0 0 0 4 9 3 3
. 1 6 M n 0
. 0 1 2 5 0
. 0 0 9 9 0
. 0 1 0 8 0
. 0 1 1 1 0
. 0 0 1 3 2 1 1
. 9 3 G a 0
. 0 0 7 3 0
. 0 0 7 3 0
. 0 0 5 7 0
. 0 0 6 8 0
. 0 0 0 9 2 4 1 3
. 6 5 A s 0
. 0 0 7 0
. 0 0 7 2 0
. 0 0 7 2 0
. 0 0 7 1 0
. 0 0 0 1 1 5 1
. 6 2 R b 0
. 0 0 8 0
. 0 0 7 9 0
. 0 0 9 1 0
. 0 0 8 3 0
. 0 0 0 6 6 6 7
. 9 9 C o 0
. 0 0 6 4 0
. 0 0 7 2 0
. 0 0 9 0
. 0 0 7 5 0
. 0 0 1 3 3 2 1 7
. 6 8 N i 0
. 0 0 5 7 0
. 0 0 7 0
. 0 0 8 0
. 0 0 6 9 0
. 0 0 1 1 5 3 1 6
. 7 1 P b 0
. 0 0 5 9 0
. 0 0 4 4 0
. 0 0 7 0
. 0 0 5 8 0
. 0 0 1 3 0 5 2 2
. 6 3 S c 0
. 0 0 3 3 0
. 0 0 2 8 0
. 0 0 2 5 0
. 0 0 2 9 0
. 0 0 0 4 0 4 1 4
. 1 0 H g 5 1 n g / g 6 1 n g / g 6 6 n g / g 5 9
. 3 3 3 3 n g / g 7
. 6 3 7 6 2 6 n g / g 1 2
. 8 7
a U n l e s s o t h e r w i s e n o t e d
. b S u l f u r i n o x i d i z e d f o r m s u c h a s s u l f a t e . c P h o s p h o r u s i n o x i d i z e d f o r m s u c h a s p h o s p h a t e . Characterization of Coal Combustion Residues T

a b le 10. T otal Content Analysis Results f or Ref erence Fly Ash after Mixing (mercur y analysis b y Method 3052 f ollo w e d b y analysis with CV AA).



### during testing through the analysis of the EP A

reference fly ash. Six extraction conditions reflecting six dif ferentextraction pHs were completed in triplicate. Figure 6 provides a flow diagram of the approach used to carry out a mass balance analysis. This flow indicates the steps used for completing the necessary analysis of one leaching testcondition (pH, LS ratio, and CCR) to assess the mass balance for mercury and other species of interest. The steps indicated in solid lines were already incorporated in the leaching assessment approach by Kosson et al. (2002). The steps indicated in dotted lines were added during this project to complete mass balance evaluation. After the samples for each evaluated leaching condition had been tumbled for the appropriate amount of time, they were each filtered and then divided into three fractions: liquid, solid, and filter . In addition, glass containers used in the procedure were rinsed with nitric acid after use, and 25Characterization of Coal Combustion ResiduesLiquid87% Leachate3% HNO35% KMnO4Clear SolutionwithHydroxylamine(5% of totalvolume)SpikeDigest inwith 0.2triplicate byppb HgOH methodfor KMnO4ICPCVAASolid Lines - Standard ProcedureDashed Lines - Additional Analysesfor Mass BalanceOne pH Sample at OneLS Ratio of One CCRSolidFilter97% LeachateThermalDigest byDigest by3% HNOAnalysis forMethodMethod3Hg by3052B3052BMethod7473CVAAICPCVAAICPSpike with 2ppm of As, Se,Pb, CdSpike with0.2 ppb ofHgSpike with 0.2 ppbAs, Se, Pb, CdlevelSpike with 0.2 ppbHg and 2 ppm ofAs, Se, Pb, CdDigest byOH methodDigest byOH methodfor KMnO4for KMno4ICPCVAAICPCVAAICPFigure 6.Flow Diagram for Mass Balance and Quality Control on Laboratory Leaching Procedures.



### 26

### m L 

### + m S 

### + m F 

### % R = × 100 m T Characterization of Coal Combustion Residues 

### the resulting rinse was analyzed to verify that there were no significant constituent losses to container walls. Each fraction was independently analyzed to evaluate the mass balance. Aliquots of each liquid sample were preserved separately for mercury analysis and for analysis by ICP
MS as described earlier . For the solid, an aliquot was sampled for each case and digested according to EP A Method 3052 (EP A, 1996). For the filter , the entire filter with any retained solids was digested according Method 3052. Each digest and liquid sample was then analyzed in triplicate for mercury using CV AA as described earlier
. Each digest and liquid sample also was analyzed in tripli
cate for As, Se, Cd, and Pb by ICP-MS. In addition to each liquid or digest sample analyzed, matrix spikes were used to determine matrix ef fects on the analytes of interest (Hg, As, Se, Cd, and Pb). For mercury spikes, the spiked solu
tion then was digested by ASTM method D6784-02 prior to analysis by CV AA. The mass balance recovery was calculated for each test case according to
where %R is the percent recovery and m L 

### , m S 

### , m F 

### , and m T 

### are the masses of the species of interest in the liquid phase, solid phase, filter, and the total content initially in the sample (based on independent analysis of the “as received” EP A

reference fly ash), respectively
. 

### 2.4.4. Improving QA/QC Ef ficiency Throughout the study , the approach to QA/QC was regu
larly reviewed for opportunities to increase evaluation ef
ficiency without unacceptably degrading precision or ac
curacy in results. Based on evaluation of results from the first several facilities, the number of replicates for Method SR002.1 (solubility as a function of pH) and Method SR003.1 (solubility as a function of LS ratio) were reduced from three to two. S tudy results have shown that the precision between duplicate analyses is acceptable and that a triplicate set does not significantly increase the qual
ity of the data set. This finding follows from (i) the data sets generated by Method SR002.1 and SR003.1 must pro
vide both consistency between replicate extractions and analyses and internal consistency between results at dif
ferent pH and LS ratio and (ii) precision is controlled pri
marily by the degree of homogeneity of the CCR under evaluation and representative sub-sampling, rather than by the intrinsic variability of the leaching test methods. Re
ducing the number of replicates has greatly improved labo
ratory ef ficiency without compromising data quality
. 

## 2.5. Interpret ation and Present ation of Laboratory Leaching Dat a Complete laboratory leaching results for Brayton Point, Pleasant Prairie, Salem Harbor, Facility C, and S t. Clair are presented in Appendices D through H, respectively . For each facility , a common format is used for presenting re
sults. First, a titration curve of pH as a function of milliequivalents of acid or base added is presented, with acid additions considered positive (+) and base additions considered negative (-). The titration figure is then followed by a curve of pH as a function of LS ratio. The pH curves are then followed by a series of figures for each species of interest (i.e., mercury , arsenic, and selenium). The results from Solubility and Release as a Function of pH (SR002.1) are presented first, followed by the results from Solubility and Release as a Function of LS ratio (SR003.1). For Solubility and Release as a Function of pH (SR002.1), results for the baseline case are presented side by side with the results from the case with enhanced mercury control. Results are presented as extract concentrations as a func
tion of pH. T otal content of the species of interest is pro
vided above the first figure for that species. The natural pH 13 

### of the system is indicated as a vertical line to the av
erage pH and a horizontal line to the y -axis indicating the corresponding extract concentration. Included with each figure are horizontal lines at the drinking water maximum concentration level (MCL) and ML and MDL analytical limits to provide a frame of reference for the results. Also included with each figure is the 5 and 95 percentile for pH (vertical lines) and for constituent concentration (horizon
tal lines) from field observations of leachate from landfills for combustion residues (T able 1 1; EP A, 2000 14 

### ; EPRI 2005), forming a rectangular box that encloses the corre
sponding domain of field leachate observations. An anno
tated example of the results is provided as Figure 7. Fig
ures with corresponding analytical recoveries are provided below the concentration results. For Solubility and Release as a Function of LS ratio (SR003.1), results are presented as extract concentrations

13 “Natural pH” of a material refers to the equilibrium pH when the material is placed in deionized water at a ratio of 10 g CCR per 100 mL of water
. 14 The EP A

data represent six ash landfills for which data were available. These data were not collected as nationally represen
tative although they do portray the range of pH values also found in the EPRI data. 

### 27As [μg/L] 5 th %tile for pH 95 th %tile for pH 10000 95 th %tile for As

1000 Concentration 95% at natural pH 100 ML MCL 10 4.8 5%

1 95 th %tile for As concentration 0.1 0.01 MDL SR2-BPT-0001-A

SR2-BPT-0001 - A SR2-BPT-0001 - B SR2-BPT-0001 - C 0.001 SR2=SR002.1 Replicate A 5% 9.5 95% 2 4 6 8 10 12 14 Sample name ML Natural pH pH MDL

P a r a m e t e r 5 % 9 5 % M C L s p H 5
. 8 1 2
. 0 9 - - M e r c u r y ( : g / L ) 0
. 0 0 2 1 0
. 0 4 9 8 2 A r s e n i c ( : g / L ) 2 1 4 0 1 0 S e l e n i u m ( : g / L ) 2
. 4 1 7 0 5 0 Characterization of Coal Combustion Residues

Figure 7. Example of Extr act Concentrations as a Function of pH from SR002.1.
T

a b le 11. Composition of Comb ustion W aste Landf ill Leachate—LEA CH 2000 database f or Arsenic and Selenium (EP A, 2000), EPRI Database f or Mercur y (EPRI, 2005) and MCL V alues
.

­



### as a function of LS ratio. Also indicated are the relevant MCL, ML, and MDL. A separate figure with analytical recoveries corresponding to the figure with concentration results are provided as an indicator of analytical quality assurance. Constituent (e.g., mercury, arsenic, and selenium) concentrations observed in laboratory leach test extracts and infield leachate samples may be the result of several mechanisms and factors. The discussion presented here focuseson constituent leaching and source term modeling approaches. Source term is defined here as the flux or amount released from the waste or secondary material (e.g., CCRs). Factors controlling constituent release and transport in and within the near field of the CCRs are often distinctly different than factors and mechanisms that are important for subsequent vadose zone or groundwater transport outside of the near -field area.In general, constituents are present in the waste or secondary material (e.g., CCR) either as adsorbed species, coprecipitated as amorphous or crystalline solid phases, orincorporated as trace components in solid phases. If chemical equilibrium conditions are approached (as is the approximate case for the laboratory and field sample conditions discussed in this report), then the functional behavior of the aqueous solution concentration reflects the natureof the constituent species in the waste or secondary material, the presence of any co-constituents in the aqueous phase influencing aqueous solution speciation (e.g., ef fectsof high ionic strength, chelating or complexing constituents), and the presence of species in the solution that maycompete for adsorption sites if adsorption is the controlling solid phase mechanism. If the constituent is present in the waste or secondary material as an adsorbed species, many dif ferent adsorption/desorption characteristic patterns are possible (Ruthven, 1984; Duong, 1998). The simplest case is when the constituent of interest ispresent at very low concentration in the waste or second28

### ( ) ⎛ L ⎞ Pore Volum eL 3 

### () 2 . LS site ⎝ ⎜ kg ⎠ ⎟ = ρ 

# ( kg m 

# )

⋅ H m ⋅ A 

## ( ) m fill fill Characterization of Coal Combustion Residues 

### ary material, relatively weakly adsorbed, and the presence of complexing and/or competing species in solution are at a constant concentration. For this case, leaching test re
sults will indicate a constant concentration as a function of pH at a fixed LS ratio and linearly increasing concentra
tion as LS ratio decreases at constant pH. This case is rep
resented mathematically as a linear equilibrium partition
ing function, where the critical constant of proportionality is the partitioning coef ficient, K d 

### . Linear partitioning and use of K d 

### values is a common approach for mathematically modeling contaminant transport at low contaminant con
centrations in soils. It is a valid and useful approach when the necessary conditions (discussed above) are fulfilled. 15 

### For mercury adsorbed on activated carbon, a complex com
bination of adsorption mechanisms is indicated. During laboratory leaching tests, mercury concentrations in the leaching test extracts are relatively constant over the pH range and LS ratio of interest and independent of total mercury content in the CCR. In addition, the total mercury content in the CCR is very low
. These results indicate ad
sorption phenomena where, in the adsorbed state, interac
tions between adsorbed mercury species are stronger (ther
modynamically) than the interactions between the adsorbed mercury species and carbon surface. 16 

### This observation has been supported by the observation of mercury dimmer for
mation during sorption (Munro et al., 2001) and the occur
rence of chemisorption as the dominant adsorption mecha
nism at temperatures above 75 E C (consistent with condi
tions in air pollution control devices; V idic, 2002). In other studies, this phenomenon has been observed as the forma
tion of molecular clusters on the adsorbent surface (Ruthven, 1984; Duong, 1998; Rudzinski et al., 1997). For this case, use of a K d 

### approach would underestimate re
lease because desorption is best represented as a constant aqueous concentration until depletion occurs. A third case is when the constituent of interest is present in the waste or secondary material (e.g., CCR) as a primary

15 Often specific K d values are a function of pH because of com
petition for adsorption sites by hydrogen ions. However, a single K

d or range of K d values are often used in contaminant fate and transport models without specific relationship between pH and K

d . 16 For this case, the first mercury molecule is adsorbed more weakly than subsequent mercury molecules because the adsorbed mercury-mercury interaction is stronger than the adsorbed mer
cury-carbon surface interaction. 

### or trace constituent in either an amorphous or crystalline solid phase and there may be complexing or chelating co
constituents in the aqueous phase. Observed aqueous con
centrations are a non-linear function of pH and LS ratio and reflect aqueous saturation with respect to the species of interest under the given conditions (pH, co-constituents). For these cases, an approximation of field conditions can be made empirically based on laboratory testing and ob
served saturation over the relevant domain (as applied in this report), or geochemical speciation modeling coupled with mass transfer modeling can be used to assess release under specific field scenarios (the subject of a future re
port). Use of a K d 

### approach would not be appropriate for these cases because constituent concentrations will remain relatively constant at a given pH until the controlling solid phase is depleted and control is shifted to a new solid phase or mechanism. 

## 2.6. Long-T erm Release Assessment Long-term constituent release estimates were developed to evaluate the potential cumulative impacts of dif ferent CCR management scenarios. A scenario of disposal in a combustion waste landfill and three default scenarios were examined. These scenarios were selected to provide upper bounding estimates of release considering:



### • the range of field observations (pH and LS ratio 15 

### ) for

analogous impoundments or landfills of combustion wastes, 

### • constituent release if occurring at the material’ s natu ral pH, and,


### • constituent release if occurring at extreme acidic or

alkaline pH. A 100-year time interval was selected as a convenient ref
erence period because it is beyond a lifetime but within a comprehendible period. Cumulative release estimates are provided on the basis of mass of constituent released per

17 For field scenarios, LS is directly a function of time ( t ), infil
tration rate (inf), landfill depth ( H

fill ), and fill density (r) accord
- ⎛ L ⎞ L ⎞ ⎡ inf cm yr t ⎤

⋅ year LS site ⎜ ⎝ kg ⎟ ⎠ = 10 ⎝ ⎜ ⎛ cm ⋅ m ⎠ ⎟ ⎢ ⎢ ⎣ ρ 

# ( kg m 3 

# )

⋅ H fill 

### ( m ⎥ ⎥ ⎦ 

# ( ) ( ) ing to 

### ) . Alter
natively, LS can be related to pore volumes of water passing through the CCRs (where A fill is the fill area) according to



### 29Probability 

### 1 0.8 0.6 0.4 0.2

0 5 6 7 8 9 10 11 12 13 14 pH

(2) (1)

Field data Fitted distribution (Logistic, (1)) Simulated (2) Fitted pH Field data distribution Simulated pH min 5.40 4.74 4.92 pH - 5% 5.80 6.00 5.97 pH - 50% 7.7 7.69 7.63 pH - 95% 12.09 11.62 10.63 pH max 12.80 +infinity 12.50 Characterization of Coal Combustion Residues 

### mass of CCR disposed ( μ g X/kg CCR). 18 

### These estimates are not intended to be absolute predictions of release, but rather, an initial assessment of whether further evaluation is warranted. These estimates for the monofill disposal sce
nario assume local equilibrium, which is a conservative assumption (i.e., estimated release is greater than actual expected release). A more refined assessment can be made using results from column leaching tests or dif fusion con
trolled leaching tests that will allow consideration of re
lease kinetics in developing field release estimates. The mass of constituent (e.g., As) that would be released if all of the leachate percolating through the landfill for the given scenario were at the MCL is provided as a reference value. The estimates presented here are only for constituent re
lease from the waste and do not account for any dilution or attenuation that would occur in the vadose zone or ground
water or for the impact of a landfill liner
. For the scenario of disposal in a combustion waste land
fill, a historical data set of typical leachate generated from this landfill type was taken from the comprehensive data
base of landfill leachate characteristics developed by the EP A ’ s Of fice of Solid W aste (EP A, 2000). Cumulative re
lease estimates were developed according to the method
ology developed by Sanchez and Kosson (2005), and val
ues of leachate pH were used to derive the probability dis
tribution function of the field pH. Annual leachate genera
tion quantities observed for industrial co-disposal landfills were used to derive the probability distribution function LS ratio that may be expected to contact the fill over the estimated time period of 100 years. For each data set (field pH and LS ratio), dif ferent distribution functions were used to fit the data, and the one providing the best data fit based on the chi-square test was selected. The resulting field pH probability distribution then was truncated and normalized to the pH range of the field data (Figure 8). The distribu
tion for field pH was the result of over 158 sample obser
vations from coal combustion residue disposal facilities at six sites. The probability distribution for the LS ratio was the result of over 41 sample observations from Industrial D landfill facilities at 17 sites. (Figure 9). For each CCR tested, results from SR002.1 (Alkalinity , Solubility and Release as a Function of pH) were used to develop an empirical functional relationship between so
lution pH and expected concentration for mercury , arsenic, and selenium. Laboratory results of mercury concentra
18 These release estimates can be converted to the amount re
leased per unit area according to M

t [mg/m 2 ] = M t [mg/kg] C ρ [kg/m 3 ] C H fill

[m]. Figure 8. Leachate pH Distr ib ution: Scenar io of Disposal in a Comb ustion W aste Landf ill. 

### tions typically showed a high degree of variability between measured and non-detected values in the laboratory leach
ing test extracts (Figure 10). This was likely due to microscale sample heterogeneity with respect to carbon distri
bution. However, the values of the measured mercury con
centrations for a specific CCR typically did not vary sig
nificantly as a function of pH. Therefore, as an upper bound
ing approximation for each specific CCR, the expected mercury concentration over the expected field pH range was set to the maximum observed extract concentration over the anticipated field pH range for that CCR. As a re
sult of this approach, all expected release of mercury should be viewed as less than or equal to the indicated value at the indicated percentile. For arsenic and selenium, a polynomial function was re
gressed to the results from SR002.1 (Alkalinity , Solubility and Release as a Function of pH) with each CCR case to provide the expected leachate concentration as a function of solution pH (Figure 1 1). The regression fits and corre
sponding equations for solubility as a function of pH are provided in the appendices for each case examined (i.e., for each constituent in each CCR tested). 301 0.9 0.8 (2) (1)Probability 0.7 0.6 0.5 0.4 0.3 0.2 0.1

0 0 0.5 1 1.5 2 2. Field data Fitted distribution (Gamma, (1)) Simulated (2) LS ratio [L/kg year]

Fitted LS 1 year Field data distribution Simulated LS min 1.0E-05 3.3E-04 3.3E-04 LS - 5% 5.5E-04 4.9E-04 4.4E-04 LS - 50% 0.06 0.08 0.08 LS - 95% 1.50 1.07 1 LS max 2.50 +infinity 1.99

10 MCL

1Hg [μg/L] 0.1 95% 0.01 0.006 5% 0.001 5% 9.5 95% 2 4 6 8 10 12 14 pH ML MDL SR2-BPT-0001 - A SR2-BPT-0001 - B SR2-BPT-0001 - C Characterization of Coal Combustion Residues

### A Monte Carlo simulation was then carried out using randomly selected pH and LS ratio values from the field data set distributions and the expected constituent equilibrium concentration at the designated pH based on laboratory leaching test results as indicated above. Thus, the relative weight of leachate solution concentration at each pH is based on the frequency of that pH occurring in the field observations. Solution concentration values from these equations then were used in conjunction with the randomly selected LS ratio values from the field LS ratio probabilitydistribution as input parameters for the percolation/equilibrium release model. Thus, the final resulting probabilitydistribution for constituent release reflects expected concentration at a given pH from laboratory testing results and weighting from the distributions of field pH, and field LS ratio. 5



### For the three default scenarios, an infiltration rate of 20 cm/yr, a fill depth of 1 m and a fill density of 1.6 g/cm 3 

### were assumed. Three different field pHs were considered: the natural pH of the material (i.e., case of a monofill) and two “extreme” pHs, a pH of 3 and a pH of 12.5. The LSratio that may be expected to contact the fill over the estimated time period of 100 years was estimated from the assumed geometry, infiltration rate, and time frame. The LS ratio obtained for this scenario was 12.5 L/kg over 100 years. Leachate concentration was assumed to be constant over the release interval at the concentration interpolatedfrom laboratory test results (SR002.1) for the corresponding pH. Assuming constant leachate concentration is considered a first order assumption because, for very soluble constituents, leachate concentration is expected to decreasewith increasing LS ratio; but for constituents where solubility increases as pH becomes less alkaline, leachate concentration is expected to increase over time. Using thisapproach, several of the ash samples would be fully depleted of Se over the 100 year leaching period. Figure 9. LS Ratio Distr ib ution: Scenar io of Disposal in a Comb ustion W aste Landf ill.



### Results of the long-term release estimates, based on the Monte Carlo simulation results accounting for both pH and LS ratio as random variables, are presented as cumulative release probability curves and as a bar chart, comparing total content of the constituent evaluated and cumulative release for each case. Annotated example results figures are provided as Figure 12 and Figure 13.

Figure 10. Example of V a r iability of Hg Concentrations as a Function of pH from SR002.1. 

### 31100000 100000 10000 10000

1000 1000

5% 95% 95% 100 95% 100

5% 95%As [μg/L] 10 1 5%As [μg/L] 10 1 5% 0.1 0.1 0.01 0.01 0.001 0.001 2 4 6 8 10 12 14 2 4 6 8 10 12 14 pH pH SR2-BPT-0001-A SR2-BPT-0001-B SR2-BPT-0001-C Fit curve SR2-BPB-0001-A SR2-BPB-0001-B SR2-BPB-0001-C Fit curve B) A) Material log As ( μ g/L) pH range of R 2 Number of validity points BPB 0.0004 pH 5 -0.0135 pH 4 0.1634 pH 3 3-14 0.77 27 -0.8130 pH 2 1.1609 pH 2.7085 BPT 0.0005 pH 5 -0.0207 pH 4 0.3035 pH 3 3-12.5 0.98 33 -2.0113 pH 2 5.4552 pH -2.7126

Selenium

100000 Mt = Cumulative release of selemium 10000 over 100 years 1000 100

10 BPT = Case with

1 enhanced mercury 5% 50% 95% control 0.1 0 20 40 60 80 100100-year Mt [μg/kg] ( : g Se/kg CCR)

BPB = Baseline case Percentile BPB BPT Characterization of Coal Combustion Residues

Figure 11. Example of Reg ression Fits and Corresponding Equations f or Solubility as a Function of pH.

Figure 12. Example of Cumulativ e Probability Distr ib ution f or Release of Selenium from Bra yton P oint CCR.


### 32100 yr cumulative release for default case of leaching at pH 3 80500 μ g/kg BPB - Arsenic (in : g As/kg CCR and as % of 100% total As content in CCR) 100000

2095 μ g/kg 2439 μ g/kg 2.6% 3.0% 105 μ g/kg 83 μ g/kg 0.1% 0.1% Assuming the 95 th percentile LS from field data 10000

1000 MCL = 1000 : g/kg LS 95% MCL LS 12.5 = 125 : g/kg 100

10 Cumulative mass released over 100 years if release occurs at MCL concentration 1 for given LS Total content Combustion Default - pH 3 Default -pH Default ­ Waste Landfill - 12.5 Natural pH 95% confidence 12.2 A) Based on Monte Carlo simulation using field pH and pH dependent leaching results100-year arsenic release [μg/kg] Characterization of Coal Combustion Residues

Figure 13. Example of Compar ison of 100 yr Cum ulativ e Release Estimates f or Arsenic.



### 33Characterization of Coal Combustion Residues



### 34P a r a m e t e r p H ( : g / L ) ( : g / L ) m e d i a n 7
. 7 8
. 1 5 1 9
. 5 5 t h % 5
. 8 2
. 0 2
. 4 9 5 t h % 1 2
. 0 9 1 4 0
. 0 1 7 0
. 0 Characterization of Coal Combustion Residues



# 3. Result s and Discussion
3.1. Leaching Characteristics from Field Observations of CCR Landfills and Impoundment s In response to concerns raised by U.S. EP A

Science Advi
sory Board regarding leaching tests, observations of pH, and concentrations of mercury , arsenic, and selenium from field CCR management facilities were evaluated for com
parison with laboratory results. Landfills and impound
ments were the types of CCR management facilities con
sidered. Information was available from a U.S. EP A

data
base (EP A, 2000) and an EPRI database (EPRI, 2005). The U.S. EP A

database (EP A, 2000) compiled by OSW included data on six CCR monofills. Data included mea
surements of pH, mercury , arsenic, selenium and other constituents as self reported by facilities to Of fice of Solid W

aste (OSW). 19 

### Data in this database was not coded to allow association of dif ferent parameters (e.g., pH, mer
cury , arsenic, selenium) from the same field sample. There
fore, data from this database was evaluated based only on the distribution of measurements for each parameter for the class of CCR monofills (T able 12). Mercury data were carefully reviewed, including re-evaluating the primary T

able 12. Distr ib ution of pH and Concentr ations of Arsenic and Selenium from Field CCR Management F acilities from the U
. S
. EP A Database (EP A, 2000). A s Se 

### source data, and were not considered to be reliable and, therefore, not included. 20 

### The EPRI database (EPRI, 2005) included measurements of samples obtained from CCR landfills and impoundments. Samples were from leachate collection points, lysimeters, and pore water . For some facilities, multiple observations were obtained from dif ferent locations within the facility and over several years. Results from a recent sampling and analysis program were observations from a range of facili
ties (considered representative of management practices, combustion facility configurations, and coal types) but with only one or two samples per facility . Data included mea
surements of pH, mercury , arsenic, selenium, and other constituents. Data on selenium were more limited than data on pH and arsenic. Data on mercury were limited to the recent sampling and analysis program from multiple fa
cilities. Data was coded to allow association of dif ferent parameters. Only CCR management facilities that receive residues from utilities that do not include scrubbers as part of the air pollution control technology are considered here. Information on pH from field observations is presented in Figure 14. For landfills, the range of data in the U.S. EP A database (5 th 

### –95 th

### percentile) was consistent with the data reported in the EPRI database. In addition, the range of pH reported in the EPRI database for individual facilities with multiple observations was similar to the range reported for multiple facilities with limited numbers of observations. Therefore, it is considered reasonable to use the pH range of 5.8 to 12.09 (5 th 

### –95 th 

### percentile) reported in the U.S. EP A

database as the basis for extrapolating from labora
tory leaching test results to field estimates of leaching from landfills.

20 Inconsistent methodologies were used, and most values were 19 As noted previously , data from six coal combustion ash land- either qualified results (e.g., estimated values) or below detec
fills were collected based on their availability and are not neces- tion limits (with relatively high corresponding detection limits sarily representative of all coal combustion ash landfills. reported). 

### 35Characterization of Coal Combustion Residues 

### L a n d f ills

0 1 2 3 4 5 6 7 89 1 0 1 1 1 2 1 3 1 4 Fi el d p H F a c i l i ty 1 ( s u bbi t
. , we s t e r n ) F a c i l i ty 2 ( s u bbi t
. , Wyom i n g) F a c i l i ty 3 ( s u bbi t
. , Wyom i n g) M u lt iple s i t e s (s i n g l e ob s e r v a t ion s ) EP A d a t a ( 5 t h 9 5 th p e r c e n ti l e )



### I m p o u nd m e nt s

0 1 2 3 4 5 6 7 8 9 10 11 1 2 13 14 Fie l d pH F a ci l i t y 4 ( s u bbi t
. , W y om i n g) F a c i lit y 5 ( b it
. , K e nt uc k y ) F a c i lit y 6 ( b it
. , ea s t ern w / py r i t e ) F a c i lit y 7 ( b it
. , K e nt uc k y w e s t e r n) F a ci l i t y 8 ( s u bbi t
. , Wes t e r n ) F a c i lit y 9 ( b it
. , K e nt uc k y e a s t e r n ) F a c i lit y 1 0 ( b i t
. w/ p y r i t e ) M u lt ip le s i t e s ( s i n g l e ob s e rva t i o n s )

Figure 14. Range of pH Obser v ed in Field Leachate at Landf ills and Impoundments Used f or Disposal of CCRs

C from EPRI Database
. Also included is the r ange (5 th –95 th percentile) of pH v alues f or CCR landf ills repor ted in the EP A database (EP A, 2000). F acilities 6 and 10 ha v e co-disposal of p y r ite from mill rejects with CCRs
. Data does not include f acilities with scr u b bers
. Pr imar y data from EPRI (EPRI, 2005). 

### Information on pH in impoundments from the EPRI data- observations of very acidic pH (pH < 3), presumably as a base indicates two general groupings of data—impound- consequence of acid-forming pyrite oxidation. ments without and with co-disposal of pyrite from coal mill tailings. Facilities without co-disposal of pyrite from Information on arsenic from field observations is presented coal mill tailings (Figure 14, all except Facilities 6 and 10) in Figure 15. For landfills, most of the data from the EPRI fall within the same pH range as the landfill data. Facili- database falls within the range (5 th 

### –95 th

### percentile) of pH ties with co-disposal of pyrite (Facilities 6 and 10) include and arsenic concentration reported in the U.S. EPA data36Characterization of Coal Combustion Residues 

### base. However, the uppermost bound of arsenic concentration in the EPRI database exceeds the U.S. EP A

datarange illustrated. In addition, the range of arsenic concentrations reported for individual facilities with multiple observations was similar to the range reported for multiple facilities with limited numbers of observations. The greatest arsenic concentrations are reported in the pH range between 7 and 10. For impoundments, the upper range of arsenic concentrations is substantially greater than reported for landfills. A significant number of reported arsenic concentrations are between 1,000 and 10,000 : g/L for impoundments, whereas all reported concentrations are less than 1,000 : g/L for landfills. Greater observed concentrations may be from leaching of arsenic naturally associated with pyrite in coal mill tailings co-disposed with CCRs rather than from the La n d f i l l s

0. 1

1 10 10 0 100 0 1 000 0

0 1 2 3 4 5 6 7 8 9 1 0 1 1 1 2 1 3 1 4 pHAs(ug/L) F a c i l i ty 1 (s u b b i t., we s t e r n ) F a c i l i ty 2 (s u b b i t., W y om i n g) F a c i l i ty 3 (s u b b i t., W y om i n g) M u l t ip le s i t e s (s i n g l e ob se r v at i o n s )



### I m p o und m e nt s

0. 1

1 10 10 0 100 0 1 000 0

0 1 2 3 4 5 6 7 8 9 1 0 1 1 1 2 1 3 1 4 pHAs(ug/L) F a ci l i t y 4 ( s u b bi t
. , W y om i n g) F a ci l i t y 5 ( b i t
. , Ke n t u c k y ) F a ci l i t y 6 ( b i t
. , e a st er nw / py r i t e ) F a ci l i t y 7 ( b i t
. , K e n t u c ky , w e st e r n ) F a ci l i t y 8 ( s u b bi t
. , we s t e r n ) F a ci l i t y 9 ( b i t
. , K e nt u c k y , e a s t e r n) F a ci l i t y 10 ( b i t
. w/ p y r i t e ) M u lt i p le s i t e s ( s in g l e ob s e r v at i o n s ) Figure 15. Arsenic Concentrations Obser v ed in Field Leachate at Landf ills and Impoundments Used f or Disposal of CCRs—from EPRI database
. Also indicated b y dashed lines is the r ange (5 th –95 th percentile) of pH and arsenic v alues f or CCR landf ills repor ted in the EP A database (EP A, 2000). Fa cilities 6 and 10 ha v e co-disposal of p y r ite from mill rejects with CCRs
. Data does not include f acilities with scr u b bers
. Pr imar y data from EPRI (EPRI, 2005). 

### 37Characterization of Coal Combustion Residues 

### CCRs. Alternatively, the significantly lower pH in the pyrite co-disposal impoundments (Figure 14) may be causing the higher As concentrations (see Figure 13, leaching at pH 3). EPRI has recommended alternative management practices for coal mill tailings containing pyrite, and this practice is diminishing (EPRI, 1999). Information on selenium from field observations is presented in Figure 16. For landfills, the EPRI database includes a wider range (greater than and less than) of reported concentrations than the U.S. EP A

database. Forimpoundments, the reported range of selenium concentrations is within the same range as reported for landfills. For
L a n d f ills

0. 1

1 10 100 1 000 10 000

0 1 2 3 4 5 6 7 8 9 1 0 1 1 1 2 1 3 1 4 pHSe (ug/L) F a c i l i ty 1 (s u b b i t., we s t e r n ) F a c i l i ty 2 (s u b b i t., W y om i n g) F a c i l i ty 3 (s u b b i t., W y om i n g) M u l t ip le s i t e s (s i n g l e ob se r v at i o n s )



### I m p o und m e n t s

0. 1

1 10 100 1 000 10 000

0 1 2 3 4 5 6 7 8 9 1 0 1 1 1 2 1 3 1 4 pHSe (ug/L) F a c i l i ty 4 (s u b b i t., W y om i n g) F a c i li t y 5 ( b it
. , Ke n t u c k y ) F a c i l i ty 8 (s u b b i t., we s t e r n ) F a c i l i ty 1 0 (b i t
. w/p y ri t e ) M u l t ip le s i t e s (si n g l e obs er va t i o n s )
Figure 16. Selenium Concentr ations Obser v ed in Field Leachate at Landf ills and Impoundments Used f or Disposal of CCRs—from EPRI database
. Also indicated b y dashed lines is the r ange (5 th –95 th percentile) of pH and arsenic v alues f or CCR landf ills repor ted in the EP A database (EP A, 2000). Fa cilities 6 and 10 ha v e co-disposal of p y r ite from mill rejects with CCRs
. Data does not include f acilities with scr u b bers
. Pr imar y data from EPRI (EPRI, 2005). 

### 38P a r a m e t e r L a n d f i l l s I m p o u n d m e n t s A s ( : g / L ) S e ( : g / L ) H g ( : g / L ) A s ( : g / L ) S e ( : g / L ) H g ( : g / L ) A

v e r a g e 4 8
. 1 2 6 5
. 9 0
. 0 1 7 9 3 8 1
. 4 5 0
. 6 0
. 0 0 1 9 M e d i a n 2 1
. 2 5 7
. 0 0
. 0 1 0 2 5 5
. 0 1 8
. 5 0
. 0 0 1 4 M i n 2
. 2 0
. 3 0
. 0 0 2 1 4
. 0 0
. 2 0
. 0 0 0 2 5 t h % 3
. 0 1
. 7 0
. 0 0 2 1 4
. 2 0
. 6 0
. 0 0 0 3 9 5 t h % 1 7 9
. 1 1 7 3 3
. 0 0
. 0 4 9 8 8 5 2
. 8 2 7 8
. 6 0
. 0 0 5 6 M a x 2 3 8
. 0 1 7 6 0
. 0 0
. 0 6 0 6 5 2 2 3
. 0 3 1 5
. 0 0
. 0 0 5 9 Characterization of Coal Combustion Residues 

### both landfills and impoundments, the range of data reported for a single facility (Facility 2) is fairly wide. T

o balance the assessment of the EPRI data in comparison with the EP A

data and laboratory leaching test results, thefollowing data reduction steps were taken. For the facilities with more than three observations, the mean value of the observations from the individual facility was taken to be representative of that facility
. The mean value then wasincluded with the data of single observations from multiple facilities. The MDL was used in the data set when the data were reported as less than the MDL. The resulting data set then was evaluated to obtain distribution statistics for the EPRI data evaluated (T able 13). The median, 5 th 

### and 95 th 

### percentiles for arsenic, selenium, and mercury then were used to for comparison with the EP A

data set and laboratory results, as described later in this report. 

## 3.2. Quality Assurance f or Laborator y Leac hing T ests 3.2.1. Mass Balance using EP A

Reference Fly Ash The results of the Reference fly ash analysis are provided in T able 14. These results show that the mass balance was closed reasonably well for mercury , arsenic, cadmium, lead, and selenium with a majority of the mass for each analyte remaining in the solid. The mass balance closure is wellwithin the expected range, especially considering the measurement of very small changes in the analyte mass in the solid phase relative to the total content present. These results also indicate that large losses of mercury do not occur as a consequence of the leaching test methods and subsequent analysis. However , additional mass balance verification may be required for implementation when testing materials with more volatile components or for validation of laboratories newly implementing the procedures. 

### 3.2.2. Analytical Quality Control/Quality Assurance Implementation of the developed QA/QC plan facilitated analysis of data quality and identification of testing uncer
tainties. The coefficient of variation for calibration standards and continuing calibration standards and blanks was within 5% for metals analysis by inductively coupled plasma-mass spectroscopy (ICP-MS) (V anderbilt). Spike recoveries for metals had a mean of 101% with a coefficient of variation within 5%. T ypical inter -laboratory comparisons for arsenic and selenium analyses are presentedin Figure 17. Good agreement generally was obtained between the two laboratories except for cases of arsenic analyses when the concentration was less than 100 : g/L. For this condition, the V anderbilt analysis typically resulted in greater values than the commercial laboratory
. This result was most likely from the dif ferences in analytical ICP-MS technology, where dynamic reaction chamber (DRC) measurements (V anderbilt) are considered more sensitive and less susceptible to interferences. For all of these cases, the spike recoveries for V anderbilt analyses were within ±10% of the expected value, with most cases within ±5% of the expected value. However , the analytical results, including repeating analysis when necessary, demonstrated the importance of including a matrix spike to verify recovery for each test condition. In contrast to the analytical uncertainty , the mean (for different test conditions, i.e., pH values) coef

ficient of variation for replicate tests on each fly ash type (resulting from variation in the subsamples of the solids tested) varied between 5% and 25%. Thus, the primarysource of uncertainty in the leaching test results is a consequence of sampling, homogenization, and inherent heterogeneity of the primary material to be tested.
T

a ble 13. Distr ib ution of pH and Concentrations of Arsenic , Selenium, and Mercur y from Field CCR Management F acilities—from the EPRI database (EPRI, 2005) f or landf ills and impoundments (including impoundments co-disposing mill rejects with CCRs).



### 39

### M e t a l A s R e c e i v e d L e a c h i n g a t p H o f 1 . 9 5 ( p o s i t i o n 1 ) L e a c h i n g a t p H o f 2 . 5 ( p o s i t i o n 2 ) Exposed L e a c h a t e Recovery Filter Solid solution % E x p o s e d Leachate Recovery Filter Solid solution % H g ( n g / g ) 5 9 ! 8 0
. 3 6 9 ! 0
. 2 7 9 ! 4 8 ! 2 7 6

S 9 1 0
. 0 1 1 0
. 2 3 3 0
. 1 0 6 ! 0
. 1 5 5 ! 5 0 ! 1 1 7 6

S 9 2 0
. 1 8 4 0
. 0 8 3 P b ( : g / g ) 8 4 ! 2
. 5 a 

### 8 7 ! 1
. 8 B D 8 ! 1 1
. 2 9 4

S 1 3 2 9 3 ! 1 3
. 5 B D 2 ! 2
. 2 8 4

S 1 3 6 S e ( : g / g ) 2 ! 0
. 3 3 ! 0
. 3 B D B D 1 1 7

S 1 9 4 2 ! 0
. 2 B D B D 7 8

S 1 2 9 C d ( : g / g ) 1 ! 0 1 ! 0 B D B D 1 0 0 1 ! 0 B D B D 1 0 0 A s ( : g / g ) 8 7 ! 2
. 6 8 9 ! 1
. 3 B D 2 ! 0
. 7 9 9

S 1 1 0 9 4 ! 4
. 1 B D 1 ! 0
. 6 1 0 3

S 1 1 5 M e t a l R e c e i v e d L e a c h i n g a t p H o f 4 . 0 ( p o s i t i o n 3 ) L e a c h i n g a t N a t u r a l p H ( p o s i t i o n 4 ) Exposed L e a c h a t e Recovery Filter Solid solution % E x p o s e d Leachate Recovery Filter Solid solution % H g ( n g / g ) 5 9 ! 8 0
. 1 2 4 ! 0
. 0 4 5 ! 3 9 ! 0
. 5 6 0

S 7 5 0
. 2 1 5 0
. 0 1 5 0
. 1 2 2 ! 0
. 0 3 0 ! 4 6 ! 8 7 5

S 8 1 0
. 2 1 2 0
. 0 0 3 P b ( : g / g ) 8 4 ! 2
. 5 8 9 ! 3
. 4 B D 0 ! 0
. 2 9 9

S 1 1 4 8 9 ! 6
. 3 B D 2 ! 1
. 2 9 7

S 1 2 1 S e ( : g / g ) 2 ! 0
. 3 2 ! 0
. 1 B D B D 8 3

S 1 2 4 3 ! 0
. 3 B D B D 1 1 7

S 1 9 4 C d ( : g / g ) 1 ! 0 1 ! 0 B D B D 1 0 0 1 ! 0 B D B D 1 0 0 A s ( : g / g ) 8 7 ! 2
. 6 9 1 ! 2
. 6 B D 1 ! 0
. 1 1 0 6

S 1 1 2 9 0 ! 3
. 4 B D 2 ! 1
. 5 9 7

S 1 1 5 M e t a l R e c e i v e d L e a c h i n g a t p H o f 1 0 . 0 ( p o s i t i o n 5 ) L e a c h i n g a t p H o f 1 2 ( p o s i t i o n 6 ) Exposed L e a c h a t e Recovery Filter Solid solution % E x p o s e d Leachate Recovery Filter Solid solution % H g ( n g / g ) 5 9 ! 8 4 4 ! 2 0
. 1 1 5 ! 0
. 1 9 9 0
. 0 1 9 ! 0
. 0 0 8 7 0

S 8 2 4 2 ! 0
. 4 B D 0
. 0 3 1 ! 0
. 0 1 3 6 3

S 8 2 P b ( : g / g ) 8 4 ! 2
. 5 8 7 ! 2
. 6 B D 2 0 ! 2 8 8 8

S 1 6 9 8 4 ! 1
. 5 B D 6 ! 6
. 6 9 5

S 1 2 0 S e ( : g / g ) 2 ! 0
. 3 2 ! 0
. 4 B D B D 7 0

S 1 4 1 1 ! 0
. 1 B D B D 3 9

S 5 9 C d ( : g / g ) 1 ! 0 1 ! 0 B D B D 1 0 0 1 ! 0 B D B D 1 0 0 A s ( : g / g ) 8 7 ! 2
. 6 9 2 ! 0
. 6 B D 4 ! 3
. 2 1 0 3

S 1 1 8 8 6 ! 0
. 8 B D 4 ! 1
. 2 9 8

S 1 2 1 a B D = b e l o w d e t e c t i o n l i m i t
. Characterization of Coal Combustion Residues Table 14. Leaching (Method SR002.1) and Mass Balance Results for the EPA-Reference Fly Ash.



## 3.3. Laborator y T est Results The constituents of interest in this evaluation, based on input from EP A-OSW and EP A-OAQPS, are mercury (Hg), arsenic (As), cadmium (Cd), lead (Pb), and selenium (Se).Initial screening indicated low content and leaching concentrations below levels of concern for lead and cadmium. As a result, although complete data have been developed for lead and cadmium, the results are not provided in this report. Complete data also have been developed for otherconstituents to facilitate evaluation of geochemical speciation of constituents of concern and to provide more thor
ough evaluation of leaching under alternative management scenarios in the future, if warranted. Screening of leachingresults against drinking water maximum contaminant levels (MCLs) indicates that antimony (Sb) may be a concern for some cases and is being considered for inclusion in future research. Complete results for pH titration, mercury ,arsenic and selenium for each CCR reported here are presented in Appendices D through I. For each CCR evaluated, results of the leaching tests provide the following information:



### • Leachate concentrations for the constituents of inter
est as a function of pH over the range of reported field management conditions (from test method SR002.1; example results provided in Figure 18 and Figure 19A).


### • pH titration curves (from test method SR002.1). This

information is useful in characterizing the CCR and assessing how it will respond to environmental stresses and material aging (e.g., carbon dioxide uptake, acid precipitation, mixing with other materials).


### • Leachate concentrations for the constituents of inter
est, pH and electrical conductivity as a function of LS ratio when contacted with distilled water (from test method SR003.1; example results are in Figure 19B). This information provides insight into the initial leachate concentrations expected during land disposal and the effects of pH and ionic strength at low LS ratios. Often these concentrations can be either greater 40Baseline Fly Ash Fly Ash with Enhanced Hg Control 

### 10000 

### 10000 1000 1000 As

Rep A Rep B Rep C 

### As

Rep A Rep B Rep CSTL Conc. [μg/L] 

### 100 10STL Conc. [μg/L]STL Conc. [μg/L] 

### 100 10

1 1 10 100 1000 10000 

### 1 10 100 1000 10000 VU Conc. [ μ g/L] 

### VU Conc. [ μ g/L] 1 A) 10000 Se

Rep A Rep B Rep C 

### 10000 1000

100

10 Se

Rep A Rep B Rep CSTL Conc. [μg/L] 

### 1000 100

10

1 

### 1 1 10 100 1000 10000 

### 1 10 100 1000 10000 B) VU Conc. [ μ g/L] 

### VU Conc. [ μg/L] Characterization of Coal Combustion Residues

Figure 17. STL V ersus V anderbilt Analytical Results f or Arsenic and Selenium from Sr002.1. Baseline Fly Ash and Fly Ash with Enhanced Hg Control from Br a yton P oint Are Sho wn. 

### than or less than concentrations observed at higher LS ratios (i.e., LS=10 mL/g as used in SR002.1) because of ionic strength and co-constituent concentration ef
fects. The MCL is used as a reference threshold for the constitu
ent of interest. However, releases identified here are esti
mates of concentrations potentially leaching from landfills. Any assessment of the environmental impact of these re
leases needs to consider the dilution and attenuation of these constituents in ground water and the plausibility of drink
ing well-water contamination resulting from the release. Dilution and attenuation factors for metals (DAFs) have been estimated to be potentially as low as 2 to 10 on a national basis or as high as 8,000 at a particular site with hydrogeology that indicates low transport potential. 21 

### Therefore, comparison with thresholds greater than the MCL and developed for specific scenarios may be appro
priate. The following comparisons are included for each CCR in Appendices D through I:



### • Laboratory leachate concentrations as a function of pH

for each CCR are compared to (i) the constituent MCL;

21 See 60 FR 66372, Dec. 21, 1995, for a discussion of model parameters leading to low DAFs, particularly the assumption of a continuous source landfill. Implied DAFs for the metals of interest here can be found at 60 FR 66432-66438 in T able C-2. Site specific high-end DAFs are discussed at 65 FR 55703, Sep
tember 14, 2000. 

### 41Baseline Fly Ash Fly Ash with ACI 

### 10 Total Hg content: 650.6 ! 6.8 ng/g 

### 10 Total Hg content: 1529.6 ! 1.1 ng/g MCL MCL



### 1 1

0.01 0.01 0.006 5% 5% 

### 0.001 0.001 5% 95% 12.2 5% 9.5 95% 

### 10 12 14 2 4 6 8 10 12 14 2 4 6 8 pH pH ML ML MDL 

### SR2-BPB-0001 - A SR2-BPB-0001 - B SR2-BPB-0001 - C MDL 

### SR2-BPT-0001 - A SR2-BPT-0001 - B SR2-BPT-0001 - C 0.1 95%Hg [μg/L]As [μg/L]Hg [μg/L]As [μg/L] 

### 0.1 95% 0.035

Total As content: 27.9 ! 2.1 : g/g 

### 10000 Total As content: 80.5 ! 1.9 : g/g 

### 10000 1000 95% 

### 100 1000 95%



### 100 4.8 5%


### 0.01 0.01 

### 0.001 0.001 95% 12.2 5% 9.5 95% 

### 2 4 6 8 10 12 14 

### 2 4 6 8 5% 

### 10 12 14 pH ML 

### pH ML MDL 

### 10

SR2-BPB-0001 - A SR2-BPB-0001 - B SR2-BPB-0001 - C MDL 

### SR2-BPT-0001 - A SR2-BPT-0001 - B SR2-BPT-0001 - C MCL MCL 

### 10

6.67 5% 

### 1 1 0.1 

### 0.1 Characterization of Coal Combustion Residues

Figure 18. Example Results from SR002.1. Br a yton P oint fly ashes—mercur y (top) and arsenic (bottom) release as a function of pH f or the baseline fly ash and the fly ash with enhanced Hg control. 5 th and 95 th percentiles of mercur y and arsenic concentrations obser v ed in typical CCR monof ill leachate are sho wn f or compar ison. Replicate A f or mercur y results likely reflects sample heterogeneity (i.e., more activ ated carbon in sub-sample). ML=method limit (f or quantif ication); MDL=method detection limit; less than MDL repor ted at 1⁄2 MDL.



### 4210000 5000 1497

1000 95% 4000

100 MCL 3000
0.1 1000 0.01 MCL 0.001 0 5% 10.3 95% 2 4 6 8 10 12 14 0 2 4 6 8 10 12 ML pH ML LS ratio [mL/g] MDL MDL SR2-SHT-0001 - A SR2-SHT-0001 - B SR2-SHT-0001 - C SR3-SHT-0001 - A SR3-SHT-0001 - B SR3-SHT-0001 - C 10 5%

1Se [μg/L]Se [μg/L] 2000

A. SR002.1 B. SR003.1 Characterization of Coal Combustion Residues

Figure 19. Example Results from SR002.1 and SR003.1 f or Selenium in Fly Ashes from Salem Harbor with Enhanced Hg Control. 

### (ii) the observed field leachate concentrations (5 th 

### and 95 th 

### percentiles of reported concentrations) over the observed pH range for field leachates based on the U.S. EP A

database (5 th

### and 95 th

### percentiles of pH), forming a “box” on the results figures (Figure 18); and, (iii) results for CCRs from the same combustion facility with and without the air pollution control technology specifically being evaluated (e.g., with and without activated carbon injection);


### • Laboratory leachate concentrations and pH as a func
tion of LS ratio for each CCR are compared to the leachate concentrations as a function of pH at LS=10 to evaluate whether expected initial leachate concen
trations under land disposal conditions will be the same, less than, or greater than the concentrations used in comparison to field data and for cumulative release estimates. Figure 19 illustrates a case where initial se
lenium concentrations in leachate at low LS ratio (Fig
ure 19B, SR003.1) are expected to be greater than in
dicated by the evaluation of concentration as a func
tion of pH at LS=10 (Figure 19A, SR002.1). 

### 3.3.1. Mercury Results A comparison of total content and range of laboratory ex
tract mercury concentrations as a function of pH and LS ratio for CCRs from dif ferent facilities is provided in Fig
ures 20 and 21, respectively
. T otal content, especially for mercury , has exhibited considerable variability for reported values from the same facility , most likely resulting from sample heterogeneity and variations in operating condi
tions. V alues reported here are those measured as part of this study . For each facility , the baseline case and the case with enhanced air pollution control treatment—either ac
tivated carbon injection or brominated activated carbon in
jection (for the S t. Clair facility and Facility L)—are com
pared. Also, note that Facility C uses COHP AC air pollu
tion control configuration. For each case in Figure 21, the range of laboratory extract concentrations was based on the CCR’ s natural pH at LS=10 from SR002.1, and the minimum and maximum concentrations observed over 5.8 # pH # 12.09 in results from testing over the range of pH (SR002.1) and LS ratio (SR003.1). For most cases, the minimum value indicated is the MDL (0.004 : g/L). As indicated previously , this pH range is based on the 5 th

### and 95 th 

### percentiles of pH in field leachate samples from CCR landfills reported in the EP A

database. The MCL is included to provide a reference basis, but consideration must be given to appropriate dilution and attenuation factors when mak
ing determinations for specific cases. Also included in Fig
ure 21 are the ranges of mercury concentrations observed in field leachates for landfills from the U.S. EP A

database and for landfills and surface impoundments from the EPRI database. For field observations, the symbol with error bars represents the median (50 th

### percentile), 5 th 

### and 95 th

### percen tiles of applicable observations in the respective database. The full range of values was not included to avoid bias from outlier data points. 43Characterization of Coal Combustion Residues

0.01

0.1

1 10Hg (mg/kg)

BPB BPT PPB PPT SHB SHT GAB GAT JAB JAT FLB FLT FLB2 FLT2 Brayton Pleasant Salem Facility C St. Clair Facility L Facility L Point Prairie Harbor (Run #1) (Run #2) Figure 20. Compar ison of T otal Mercur y Content in Baseline Cases and with Sorbent Injection f or CCRs from Diff erent F a cilities
. (F acility code suff ix es B = baseline and T = treated with sorbent injection; f or e xample , PPB = Pleasant Prair ie baseline , and PPT = Pleasant Prair ie treated) 

### Considering the results provided in Appendices D through 

### • Although the use of ACI substantially increases the I, and comparisons in Figure 20 and Figure 21, the follow- total mercury content in the CCRs, the range of laboing observations for mercury are made: ratory leaching extract concentrations in the baseline



### • Use of sorbent injection increased the total mercury cases and cases with sorbent injection are either uncontent for the fly ash to ca. 1–2 mg/kg except for Sa- changed or the maximum leaching concentration is lem Harbor. This value may represent the maximum reduced as a consequence of activated carbon injecpractical capacity for the sorbent entrained with the tion. The exceptions are Facility C and Facility L, fly ash. The total content of mercury in fly ash from which have an increased maximum extract concentraSalem Harbor may be relatively unchanged or slightly tion for the case with sorbent injection. lower because of the high content of uncombusted car- 

### • The expected range of mercury leachate concentrations bon (LOI = 21 wt%) for the baseline case, which acts based on these results is from < 0.004 (below MDL) a sorbent similar to activated carbon; in this case, in- to 0.2 : g/L over the range of pH conditions expected jection of activated carbon serves to dilute the total in coal ash landfill leachate. mercury content in the CCR. 

### • The range of mercury concentrations observed from 

### • For Facility L, accumulation of the fly ash for sam- laboratory extracts is consistent with the range reported

pling for 4 hours (Run #1) resulted in loss of mercury for field leachates from landfills in the EPRI database. from the fly ash when compared to fly ash accumu- Reliable data on mercury concentrations in leachates lated for 30 minutes (Run #2), most likely by volatil- from landfills was not available in the EPA database. ization at the elevated temperatures within the accu- A lower range of field concentrations is reported for mulation hopper. Fly ash obtained from Run #1 was impoundments in the EPRI database, possibly resultused for leaching evaluation because of the limited ing from a combination of dilution or volatilization sample quantity available from Run #2. occurring during management in impoundments. 44Characterization of Coal Combustion Residues
10 MCL

1
0.1
0.01
0.001
0.0001 BPB BPT PPB PPT SHB SHT GAB GAT JAB JAT LAB LAT LF IMP max

min 

### * Natural pH
95 th % 50 th %

5 th % 

### * * * * * * * * * *
* Indicates <MDL

Brayton Pleasant Salem Facility C St. Clair Facility L EPRI Point Prairie Harbor/L)H (Hg (:g/L)

Figure 21. Ranges of Laborator y and Field Leachate Mercur y Concentr ations Compared with the Dr inking W ater Maxim um Contaminant Le v el (MCL). [F or labor ator y data, symbol represents the concentr ations at the natur al pH of the CCR tested, and the error bars represent the minim um and maxim um concentrations within the rele v a nt f ield pH r ange of 5.8 to 12.09, inclusiv e . F or f ield data, symbol and error bars represent the 5 th , 50 th and 95 th percentiles of repor ted v alues (LF = landf ills from EPRI database; IMP = impoundments from EPRI database). Reliab le data f or mercur y w as not a v ailab le in the EP A database
. ]



### • All concentrations observed in laboratory leach test

extracts over 5.8 # pH # 12.09 were at least an order of magnitude less than the MCL.


### • For all cases of laboratory extracts, mercury concentrations in extracts were consistent without any significant effect of total mercury content, pH, or LS ratio observed. Mercury leaching appears to be controlledby adsorption from the aqueous phase with strong interaction between adsorbed mercury molecules, indicating that use of a linear partition coef ficient ( K

d

### ) approach to model source term mercury leaching would not be appropriate. Variability observed in concentrations observed within individual cases is likely the result of sampling and CCR heterogeneity at the particlescale (i.e., resulting from mercury adsorption specifically onto carbon surfaces and relatively more or lesscarbon particles in a specific subsample used for extraction). 

### 3.3.2. Arsenic ResultsA comparison of total content and of the range of laboratory extract arsenic concentrations as a function of pH and LS ratio for CCRs from dif ferent facilities is provided in Figures 22 and 23, respectively
. The approach used and comparisons made in Figure 23 are the same as for mer
cury in Figure 21. For the presentation of field leachateconcentrations from impoundments, facilities co-disposing CCRs with coal mill rejects containing pyrite are presented along with impoundments not receiving pyrite. Considering the results provided in Appendices D through H, and comparisons in Figures 22 and 23, the following observations for arsenic are made:



### • Use of ACI resulted in a substantial increase in total

arsenic content in CCR from Facility C (COHPAC facility), but there was not a corresponding increase in laboratory leaching test extract concentrations. 45Characterization of Coal Combustion ResiduesAs (mg/kg) 1000

100

10 BPB BPT PPB PPT SHB SHT GAB GAT JAB JAT FLB FLT FLB2 FLT2 Brayton Point Pleasant Prairie Salem Harbor Facility C St. Clair Facility L Run #1 Facility L Run #2 Figure 22. Compar ison of T otal Arsenic Content in Baseline Cases and with Sorbent Injection f o r CCRs from Diff erent F a cilities
. (F acility code suff ix es B = baseline and T = treated with sorbent injection; f or e xample , PPB = Pleasant Prair ie baseline , and PPT = Pleasant Prair ie treated)



### • Use of ACI resulted in a substantial decrease in total

arsenic content in CCR for Brayton Point.


### • There was not a consistent pattern with respect to the

ef

fect of ACI on the range of laboratory extract concentrations. For Salem Harbor and slightly for Pleasant Prairie facilities, the cases with ACI had an increase in the upper bound of extract concentrations compared to the same facility without ACI. For Facility C and the Brayton Point and S t. Clair facilities, a corresponding decrease was observed.


### • V ery low extract concentrations were observed for the S t. Clair facility without and with B-P AC, even though the total arsenic content was comparable to several of the other cases. Conversely , relatively high extract concentrations were observed for Facility L without and with B-PAC, even though the total arsenic concentration was low compared to the other cases. Thus, the presence of other constituents in the CCRs or theformation conditions appears to have a strong influence on the release of arsenic.


### • The range of arsenic concentrations observed in the

laboratory extracts is consistent with the range of values reported for field leachates from landfills and impoundments. For some cases, both laboratory (Salem Harbor, Facility C, Facility L) and field concentrations exceeded the MCL by more than a factor of 10. The e x pected range of arsenic concentrations under field conditions is less than 10 : g/L to approximately 1000 : g/L.


### • Arsenic leachate concentrations typically are strongly

a function of pH over the entire pH range examined and within the pH range observed for field conditions(for example, see Figure 18). For some cases (for example, see S t. Clair , Appendix H), measured concentrations of arsenic are strongly a function of LS ratio at the material’ s natural pH, with much greater concentrations observed at low LS ratio. Therefore, testing at a single extraction final pH or LS ratio would not provide suf ficient information to characterize the range of expected leachate concentrations under field conditions. Furthermore, for some of the CCRs a shift from the CCR’ s natural pH within the range of anticipated conditions (e.g., Facility L, Brayton Point with ACI, Salem Harbor baseline, Facility C baseline) can result substantial increases in leachate concentrations.Therefore, co-disposal of these CCRs with other materials should be carefully evaluated. 46* Indicates < MDLAs (:g/L) 10000
1000

100
MCL

10

1
0.1 BPB BPT PPB PPT SHB SHT GAB GAT JAB JAT LAB LAT EPA LF IMP 

### * * min max Natural pH 95 th %

50 th %

5 th %

Brayton Pleasant Salem Facility C St. Clair Facility L EPRI Point Prairie Harbor Characterization of Coal Combustion Residues

Figure 23. Ranges of Labor ator y and Field Leachate Arsenic Concentr ations Compared with the Dr inking W ater Maximum Contaminant Le v el (MCL). [F or labor ator y data, symbol represents the concentr ations at the natur al pH of the CCR tested, and the error bars represent the minim um and maxim um concentrations within the rele v a nt f ield pH r ange of 5.8 to 12.09, inclusiv e . F or f ield data, symbol and error bars represent the 5 th , 50 th and 95 th percentiles of repor ted v alues (EP A = EP A database; LF = landf ills from EPRI database; IMP = impoundments from EPRI database). Reliab le data f o r mercur y w as not a v ailab le in the EP A database
. ]



### • For several cases (Brayton Point, Salem Harbor, Facility C without ACI, Facility L), arsenic concentrations in laboratory extracts appear to be controlled by solid phase solubility , whereas adsorption processes appear to play a more important role for other cases (Pleasant Prairie, Facility C with ACI, S t. Clair). 

### 3.3.3. Selenium ResultsA comparison of total content and of the range of laboratory leach test extract selenium concentrations as a function of pH and LS ratio for CCRs from dif ferent facilities is provided in Figures 24 and 25, respectively
. The approach used and comparisons made in Figure 25 are the same as for mercury in Figure 21. Considering the results provided in Appendices D through I, and comparisons in Figures 24 and 25, the following observations for selenium are made:



### • For two cases (Brayton Point, Facility C), use of ACI

resulted in a substantial increase in the total selenium content of the CCR in comparison to the same case without ACI. For Facility C, this is likely a direct consequence of the COHP AC configuration when ACI isin use. For the other cases, the change in total selenium content resulting from application of ACI or BP

AC was minor but increased in all cases.


### • The range of selenium concentration in laboratory leach

test extracts is not correlated with total selenium content in the CCRs. For example, Brayton Point with ACI had much greater total selenium content than the other cases except Facility C with ACI, but it had only thefifth highest selenium concentration under the laboratory leaching conditions. Conversely , Facility C baseline had one of the lowest selenium total content (less than MDL), but it had second greatest selenium concentration under the laboratory leaching conditions.


### • The range of selenium concentrations observed in laboratory leach test extracts for Facility C are much greater than the concentrations observed for other cases and for field conditions. This is a COHP AC facility , and field leachate composition data for CCRs from this type of facility was not available in the EP A

or EPRI databases. For all other facilities, the range of concentrations observed from laboratory testing is consistent with 47Characterization of Coal Combustion ResiduesSe (mg/kg) 1000

100

10

1 

### * * * * * Indicates < MDL BPB BPT PPB PPT SHB SHT GAB GAT JAB JAT FLB FLT FLB2 FLT2

Brayton Point Pleasant Prairie Salem Harbor Facility C St. Clair Facility L (Run #1) Facility L (Run #2) Figure 24. Compar ison of T otal Selenium Content in Baseline Cases and with Sorbent Injection f or CCRs from Diff erent F a cilities
. (F acility code suff ix es B = baseline and T = treated with sorbent injection; f or e xample , PPB = Pleasant Prair ie baseline , and PPT = Pleasant Prair ie treated) 

### the range reported in the EPRI database for landfills. The concentration range reported in the EP A

database for CCR landfills has a much lower upper bound than reported in the EPRI database.


### • The concentration range for laboratory extracts and

field observations exceeded the MCL for all cases ex
cept Facility L. For 5 out of 12 of the cases used for laboratory evaluation and for some field observations, the MCL is exceeded by more than a factor of 10.


### • Selenium concentrations in laboratory leach test ex
tracts typically are strongly a function of pH over the entire pH range examined and within the pH range observed for field conditions (for example, see Brayton Point, Salem Harbor, Facility C). For some cases (for example, see Figure 19 or Brayton Point, Salem Har
bor, S t. Clair in Appendices D, F , and H, respectively), measured concentrations of selenium are strongly a function of LS ratio at the material’ s natural pH, with much greater concentrations observed at low LS ratio. Therefore, testing at a single extraction final pH or LS ratio would not provide suf ficient information to char
acterize the range of expected leachate concentrations under field conditions. 

### • For several cases (Brayton Point, Salem Harbor, Fa
cility C, Facility L), selenium concentrations in labo
ratory extracts appears to be controlled by solid phase solubility , whereas adsorption processes appear to play a more important role for other cases (Pleasant Prairie, S t. Clair). 

## 3.4. Long-T erm Release Assessment Cumulative release estimates for CCRs from each facility , both for the baseline case and the case with enhanced mer
cury recovery , are presented in Appendices D through I. One hundred year release estimates of mercury , arsenic and selenium are presented. One example of long-term re
lease assessment results for arsenic and selenium is pro
vided in Figures 26 and 27. For each case, first the polyno
mial curve fits for solubility as a function of pH are pre
sented along with the corresponding data from laboratory leaching test results (SR002.1) and the 5 th

### and 95 th 

### percen tile of pH and constituent concentration from the U.S. EP A database. Next, the cumulative probability distribution for cumulative constituent release is provided from the Monte Carlo simulation for both the baseline and test cases. Fi
nally , a bar chart, comparing total content of the constitu
48100000 10000

1000

5% 95% 5% 95%As [μg/L] 100 10

1 0.1 0.01 0.001 2 4 6 8 10 12 14 pH
B) SR2-BPT-0001-A SR2-BPT-0001-B SR2-BPT-0001-C Fit curve Characterization of Coal Combustion Residues

MCLS (/L)

0.1 1 10 100 1000 10000 100000

max Natural pH min 95 th %

50 th %

5 th %Se (:g/L)

BPB BPT PPB PPT SHB SHT GAB GAT JAB JAT LAB LAT EPA LF IMP Brayton Pleasant Salem Facility C St. Clair Facility L EPRI Point Prairie Harbor Figure 25. Ranges of Labor ator y and Field Leachate Selenium Concentr ations Compared with the Dr inking W ater Maximum Contaminant Le v el (MCL). [F or labor ator y data, symbol represents the concentr ations at the natur al pH of the CCR tested, and the error bars represent the minim um and maximum concentr ations within the rele v ant f ield pH r ange of 5.8 to 12.09, inclusiv e . F or f ield data, symbol and error bars represent the 5 th , 50 th and 95 th percentiles of repor ted v alues (EP A = EP A database; LF = landf ills from EPRI database; IMP = impoundments from EPRI database). Reliab le data f or mercur y w as not a v ailab le in the EP A database
. ] 

### ent evaluated, estimated cumulative release over 100 years, and percent of total content released is provided for the baseline and test cases. Similar results are not provided for mercury because of the simplification used for the assess
ment based on results and underlying mechanism (see sec
tion 2.5.1). 

### 3.4.1. Long-term Release Estimates for Mercury A comparison of the long-term (100 yr) mercury release estimates from the Monte Carlo simulation for each case is presented in Figure 28A on a mass basis (micrograms of Hg released per kilogram of CCR) and Figure 28B as a percent of total mercury released. Figure 28A also includes the total mercury content for each case. Considering the results provided in Appendices D through I, and comparisons in Figure 28, the following observa
tions for mercury are made: Figure 26. Example Reg ression Cur v es of Exper imental



### • The estimated mass of mercury released over the as- Data of Arsenic Solubility as a Function of pH f or Bra yton 

### sessment period does not correlate with the total mer
- P oint. 

### 49μ g/kg % μ g/kg % Mt min 0.2 0.0003 0.1 0.0003 Mt - 5% 0.9 0.0011 0.1 0.0005 Mt - 50% 152 0.2 22 0.0772 Mt - 95% 2095 2.6 338 1.2 Mean Mt 468 0.6 90 0.3 Mt max 4693 5.8 10157 36.4 BPB BPT 5% 95% 0.1

1 10 100 1000 10000

0 20 40 60 80 100 Percentile100-year Mt [μg/kg]

BPB BPT Arsenic

50% Characterization of Coal Combustion Residues

Figure 27. Example 100-Y ear Arsenic Release Estimates f or Br a yton P oint as a Function of the Cum ulativ e Probability f or the Scenar io of Disposal in a Comb ustion W aste Landf ill. (Mt ref ers to the cum ulativ e release o v er the 100-y ear inter v al.) 

### cury content of the CCR. This is a consequence of the relatively constant leaching test extract concentrations independent of the total mercury content in the CCR. For all cases, the median expected release over 100 years is less than or equal to 1 : g/kg, with the 5 th

### and 95 th 

### percentiles less than or equal to 0.005 and 15 : g/ kg, respectively
. 

### • The percentage of total mercury estimated to be re
leased over 100 years ranges from a very small per
centage (less than 0.002%) to less than 5% for most cases. From less than a very small percentage (less than 0.03%) to less than 80% of the total mercury may be released from cases Facility C baseline and Facility L. The higher percentages for these three cases reflects the lower total mercury content present in the CCR. 

### 3.4.2. Long-T erm Release Estimates for Arsenic A comparison of the long-term (100 yr) arsenic release estimates from the Monte Carlo simulation for each case is presented in Figure 29A on a mass basis (micrograms As released per kilogram CCR) and Figure 29B as a percent of total arsenic released. Figure 29A also includes the total arsenic content for each case and MCL LS95% 

### for reference. MCL LS95% 

### is the amount of arsenic that would be released (1,000 : g/kg) if the leachate concentration was equal to the MCL for arsenic (10 : g/L) for the entire 100 year pe
riod and if the infiltration rate was at the 95 th 

### percentile of reference cases for landfills in the U.S. EP A

database. For the purposes of this study , values that exceed this thresh
old may warrant further examination as to whether or not additional management controls should be considered. Considering the results provided in Appendices D through I, and comparisons in Figure 29, the following observa
tions for arsenic are made:



### • The estimated mass of arsenic released over the as
sessment period does not correlate with the total ar
senic content of the CCR. For all cases except Salem Harbor, Facility C, and Facility L, less than 0.1% to 5% of the total arsenic content is anticipated to be re
leased.


### • Salem Harbor, Facility C baseline, and Facility L are cases where up to a very high percentage (more than 30%) of the total arsenic content may be released un
der some management conditions.


### • The cases of Salem Harbor, Facility C, and Facility L

are examples of where more detailed release evalua
tion is warranted, considering site specific management practices, infiltration rates, and dilution and attenua
tion factors. 

### 3.4.3. Long-term Release Estimates for Selenium A comparison of the long-term (100 yr) selenium release estimates from the Monte Carlo simulation for each case is presented in Figure 30A on a mass basis (micrograms Se released per kilogram CCR) and Figure 30B as a percent of total arsenic released. The presentation in Figure 30 is analogous to the presentation used for arsenic release esti
mates in Figure 29 and discussed previously
. Considering the results provided in Appendices D through I, and comparisons in Figure 30, the following observa
tions for selenium are made:



### • For all cases except Brayton Point, from 40% up to

the total content of selenium in the CCR is anticipated to be released at the 95 th 

### percentile, with between 3% and 20% for the median case (except Facility C baseline, where the median case is 100% of the total). For Brayton Point, from 1% to 30% of the total con
50H (/k )

0.0001 0.001

0.01

0.1

1 10 100 1000 10000

Median Total Content 95 th %

50 th %

5 th %Hg (:g/kg)

BPB BPT PPB PPT SHB SHT GAB GAT JAB JAT LAB LAT Brayton Pleasant Salem Facility C St. Clair Facility L A) Point Prairie HarborHg (of Total)

0.00001 0.0001

0.001

0.01

0.1

1 10 100

Median 95 th %

50 th %

5 th %Hg (% of Total)

BPB BPT PPB PPT SHB SHT GAB GAT JAB JAT LAB LAT Brayton Pleasant Salem Facility C St. Clair Facility L B) Point Prairie Harbor Characterization of Coal Combustion Residues

Figure 28. Upper Bound of 100 yr Mercur y Release Estimates f or Landf ill Scenar io Without and with Activ ated Carbon Injection. (A) mass released in : g of mercur y released per kg of CCR and total content in : g of mercur y per kg of CCR, (B) percent of total mercur y content released. Symbol with error bars represents 5 th , 50 th and 95 th percentiles from Monte Car lo simulation. (F acility code suff ix es B = baseline and T = treated with sorbent injection; f or e xample , PPB = Pleasant Pr air ie baseline , and PPT = Pleasant Pr air ie treated) 

### 51tAs (:g/kg) 1000000 100000

10000

1000

100

10

1 0.1 0.01 0.001 BPB BPT PPB PPT SHB SHT GAB GAT JAB JAT LAB LAT Brayton Pleasant Salem Facility C St. Clair Facility L A) Point Prairie Harbor/k )A (

BPB BPT PPB PPT SHB SHT GAB GAT JAB JAT LAB LAT Brayton Pleasant Salem Facility C St. Clair Facility L B) Point Prairie Harbor MCL LS 95% =1000 μ g/kg

Median Total Content 5 th % 50 th % 95 th %

5 th %A (% f T l)

0.00001 0.0001

0.001

0.01

0.1

1 10 100

Median 95 th %
50 th %

5 th %As (% of Total) Characterization of Coal Combustion Residues

Figure 29. Upper Bound of 100 yr Arsenic Release Estimates f or Landf ill Scenar io Without and with Activ ated Carbon Injection. (A) mass released in : g of arsenic released per kg of CCR and total content in : g of arsenic per kg of CCR, (B) percent of total arsenic content released. Symbol with error bars represents 5 th , 50 th and 95 th percentiles from Monte Car lo sim ulation. (F acility code suff ix es B = baseline and T = treated with sorbent injection; f or e xample , PPB = Pleasant Prair ie baseline , and PPT = Pleasant Pr air ie treated) 

### 52Se (:g/kg) 1000000 100000

10000

1000

100/k( ) S MCL LS 95% =5000 μ g/kg

Median Total Content 5 th % 50 th % 95 th %

10

1 0.1 BPB BPT PPB PPT SHB SHT GAB GAT JAB JAT LAB LAT Brayton Pleasant Salem Facility C St. Clair Facility L A) Point Prairie Harbor

BPB BPT PPB PPT SHB SHT GAB GAT JAB JAT LAB LAT

Brayton Pleasant Salem Facility C St. Clair Facility L B) Point Prairie HarborS (% f T l)

0.001 0.01

0.1

1 10 100

Median 5th % 50 th % 95th %Se (% of Total) Characterization of Coal Combustion Residues

Figure 30. Upper Bound of 100 yr Selenium Release Estimates f or Landf ill Scenario Without and with Activ ated Carbon Injection. (A) mass released in : g of selenium released per kg of CCR and total content in : g of selenium per kg of CCR, (B) percent of total selenium content released. Symbol with error bars represents 5 th , 50 th and 95 th percentiles from Monte Car lo sim ulation. (F acility code suff ix es B = baseline and T = treated with sorbent injection; f or e xample , PPB = Pleasant Pr air ie baseline , and PPT = Pleasant Pr air ie treated) 

### 53Characterization of Coal Combustion Residues 

### tent is anticipated to be released for more than half of the anticipated conditions.


### • Low fractional releases of selenium (less than 0.1%,

except for Facility C baseline) at the 5 th

### percentile suggest management scenarios where anticipated release can be substantially reduced for each CCR case, either through control of pH or infiltration.


### • All cases are examples of where more detailed release

evaluation is warranted, considering site specific management practices, infiltration rates, and dilution and attenuation factors.

54Characterization of Coal Combustion Residues



# 4. Conclusions and Recommendations
4.1. Assessment of CCRs Without and With Activ ated Carbon InjectionAnalysis has been completed for CCRs from six coal combustion facilities that control mercury emissions by sor
bent injection; four using powdered activated carbon injection and two using brominated powdered activated car
bon injection. For each facility , the evaluation included assessments of CCRs generated both with and without use of the activated carbon injection. None of these facilitieshad scrubbers as part of their air pollution control technology . The following conclusions are drawn for this class of facilities:



### • Application of activated carbon injection substantially

increased the total mercury content in the resultingCCRs for five of the six facilities evaluated. Substantially increased arsenic and selenium content in the CCRs was observed at the one facility that employed COHP AC fabric filter particulate control technology
. This may have resulted from additional arsenic and selenium adsorption onto the CCR while retained in the fabric filters. Significant increase in the selenium content of one additional facility was noted.


### • Mercury is strongly retained by the CCR and unlikely

to be leached at levels of environmental concern. Leaching that did occur did not depend on total mer
cury content in the CCR, leaching pH, nor liquid to solid ratio, and mercury concentrations in laboratoryextracts appeared to be controlled by non-linear adsorption equilibrium. Laboratory extract concentrations ranged between less than the MDL (0.01 : g/L) and 0.2 : g/L.


### • Arsenic and selenium may be leached at levels of potential concern from CCRs generated at some facilities both with and without enhanced mercury control technology . Further evaluation of leaching of arsenic and selenium from CCRs that considers site specific conditions is warranted.


### • Leachate concentrations and the potential release of

mercury , arsenic and selenium do not correlate with total content. For many cases, leachate concentrations observed are a function of final pH over the range of field conditions, and the observed leaching behaviorimplies that solubility in the leachate or aqueous extract controls observed liquid concentration rather than linear adsorption equilibrium. For these cases, use of linear partition coef ficients ( K

d 

### ) in modeling leaching phenomena does not reflect the underlying processes. In addition, for many cases, the amount of mercury , arsenic and/or selenium estimated to be released over a 100 year interval is a small fraction (less than 0.1% to 5%) of the total content. For selenium, release from less than 5% up to the total content of selenium can be anticipated over the 100 year period. Therefore, it isnot recommended to base landfill management decisions on total content of constituents in CCRs since total content does not consistently relate to quantity released.


### • Results of this assessment also suggest management

conditions (e.g., through control of infiltration and pH) that may result in reduction releases of arsenic and selenium by as much as two orders of magnitude in comparison to upper bound estimated releases.


### • Use of the Leaching Framework facilitated understanding the variations in anticipated leaching behavior under the anticipated field landfill disposal conditions, including expected ranges of constituent concentrations in leachate and cumulative release over a defined timeinterval. In addition, insights into the mechanisms controlling constituent leaching were obtained. This depth of understanding would not have been possible using leaching tests focused on a single extraction condition (e.g., TCLP , SPLP , or SGLP).


### • This study provides baseline data which allows using

a reduced set of laboratory testing conditions as a screening leaching assessment for CCRs from coal combustion facilities employing similar air pollution control technology . For mercury , extraction only at the material’ s natural pH at LS=10 is adequate. For ar
senic, extraction at four conditions is warranted to de55Characterization of Coal Combustion Residues 

### fine the range of expected leachate concentrations and release: (i) pH 5.5–6.0 at LS=10, (ii) pH 7.5–8.5 at LS=10, (iii) pH 12.0–12.5 at LS=10 and (iv) natural pH at LS=2. For selenium, either the total content or the same conditions as recommended for arsenic can be used. At least duplicate extractions should be used.Results from this more limited testing can be evaluated in comparison with the results presented in this report to determine if more extensive evaluation is warranted. 

## 4.2. Implementation of Leac hing T est Methods The leaching assessment approach published by Kosson etal. (2002) and implemented in this report was selected because after internal EP A

review (Of fice of Research and Development, Of fice of Solid W aste) and consultation with the Environmental Engineering committee of the EP A

Science Advisory Board, it was considered the only availablepeer reviewed and published approach that allowed consideration of the range of potential field management scenarios expected for CCRs and that provided a fundamental foundation for extrapolation of laboratory testing to field scenarios. Additional development and validation of the leaching assessment approach through this project provides the following conclusions:



### • Laboratory leaching test results were consistent with

observed ranges of field leachate pH and with mer
cury , arsenic, and selenium concentrations. Thus, the leaching test methods employed in this study provide an appropriate basis for evaluating leaching under the range of anticipated field management scenarios.


### • Leaching test methods SR002.1 (Solubility and Release as a Function of pH) and SR003.1 (Solubilityand Release as a Function of LS ratio) have been successfully implemented at the EP A

National Risk Management Research Laboratory
. The use of these methods is now considered near routine methodology for the laboratory
. 

### • QA/QC methodology conforming with EP A T ier 3 requirements has been developed and demonstrated for the leaching test methods SR002.1 and SR003.1.


### • Further ef ficiency in implementation of the QA/QC methodology may be obtained, based on the results from testing the initial set of CCRs, by reducing the number of replicates and control analyses required under the initial QA/QC plan. These improved project ef

ficiencies are being implemented for evaluation of additional CCRs under this project.


### • A mass balance around the laboratory leaching test procedures has been completed for mercury and selected metals of potential concern. These results indicate that recoveries were between 60% and 91% for mercury during the leaching tests and subsequent analytical procedures, which is within the uncertainty resulting from heterogeneity within the CCR. Additional mass balance verification may be warranted if future samples have significantly dif ferent characteristics that may result in greater volatility of the constituents of inter
est than in the reference sample evaluated.

56Characterization of Coal Combustion Residues



# 5. References

ACAA (American Coal Ash Association), 2000. 1999 Coal Combustion Product (CCP) Production and Use (Short T ons), available at http://www .acaa-usa.or g/whatsnew/ccp_surveys.htm(accessed March 2001). ACAA (American Coal Ash Association), 2003. 2003 Coal Combustion Product (CCP) Production and Use Survey , ACAA, Alexandria, V A, available at http://www .acaa-usa.or g/PDF/2003_CCP_Survey( 10-1-04).pdf (accessed January 2006). Clean Air Mercury Rule: 70 FR 28606; May 18, 2005. Clean Air Interstate Rule: 70 FR 25162; May 12, 2005. Duong D. Do., 1998. Adsorption Analysis: Equilibria and Kinetics . Imperial College Press, London, 892 p. EP A, 1988. Report to Congress–W astes from the Combustion of Coal by Electric Utility Power Plants. EP A/530/SW -88/002, U.S. EP A, Of fice of Solid W aste and Emergency Response, W ashington, DC. EP A, 1996. Method 3052 “Microwave Assisted Acid Digestion of Siliceous and Or ganically Based Matrices,” T est Methods for Evaluating Solid W aste, Physical/Chemical Methods (SW-846), available at http://www .epa.gov/sw-846/main.htm(accessed January 2006). EP A, 1998. Method 7473 “Mercury in Solids and Solutions by Thermal Decomposition, Amalgamation, and Atomic Absorption Spectrophotometry ,” T est Methods for Evaluating Solid W aste, Physical/Chemical Methods (SW -846), available at http://www .epa.gov/sw-846/main.htm (accessed January 2006). EP A, 1999. Report to Congress-W astes from the Combustion of Fossil Fuels: V olume 2-Methods, Findings and Recommendations. EP A/530/R-99/010. U.S. EP A, Of fice of Solid W aste and Emergency Response, W ashington, DC. EP A, 2000. Characterization and evaluation of landfill leachate. EP A, Draft Report. 68-W6-0068, September 2000. EP A, 2002. Characterization and Management of Residues from Coal-Fired Power Plants, Interim Report. EP A/600/R-02/083, December
. EP A, 2003. T echnical Support Document for the Assessment of Detection and Quantitation Approaches. EP A/821/R-03/005. U.S EP A, Of fice of W ater , W ashington, DC, available at ( http://epa.gov/waterscience/methods/det/index.html) [Superceded by Revised Assessment of Detection and Quantitation Approaches, EP A/821/B-004/005, available at http://www .epa.gov/waterscience/methods/det/rad/rad.pdf (accessed January 2006)]. EP A, 2005. Control of Mercury Emissions from Coal Fired Electric Utility Boilers: An Update, U.S. EP A, Of fice of Research and Development, Research T riangle Park, NC, Feb 18, available at http://www .epa.gov/ttn/atw/utility/ord_whtpaper_hgcontroltech_oar -2002-0056-6141.pdf accessed January 2006. EPRI, 1999. Guidance for Co-management of Mill Rejects at Coal-Fired Power Plants. Report TR-108994. EPRI, 2005. Personal communication of EPRI leaching database (as of June 2005) summary information from K. Ladwig to D. Kosson. 

### 57Characterization of Coal Combustion Residues Kosson, D.S., van der Sloot, H.A., Sanchez, F ., and Garrabrants, A.C., 2002. An Integrated Framework for Evaluating Leaching in W aste management and Utilization of Secondary Materials, Envir onmental Engineering Science 19 :3, 159–204. MTI (McDermott T echnology , Inc.), 2001. Mercury Emissions Predictions, available at http://www .mtiresearch.com/aecdp/mercury.html#Coal%20Analyses%20and%20Mercury%20Emissions%20Predictions , accessed November 2002. Munro, L.J., Johnson, K.J., and Jordan, K.D., 2001. An Interatomic Potential for Mercury Dimmer , J. of Chemical Physics , 11 4 :13, 5545–5551. Nelson, S., 2004. “Advanced Utility Sorbent Field T esting Program,” DOE/NETL Mercury Control T echnology R&D Program Review , Pittsbur gh, P A, July 14–15, 2004. Nelson, S., Landreth, R., Zhou, Q., Miller , J., 2004. “Accumulated Power -Plant Mercury-Removal Experience with Brominated P

AC Injection”, Joint EPRI DOE EP A

Combined Utility Air Pollution Control Symposium, The Mega Symposium, W ashington, D.C., August 30–September 2. Rudzinski, W ., W .A. S teele, and G
. Zgrablich, 1997. Equilibria and Dynamics of Gas Adsorption on Heter ogeneous Solid Surfaces . Elsevier, Amsterdam. Ruthven, D.M., 1984. Principles of Adsorption and Adsorption Pr ocesses . W iley, New Y ork, 433 p. SAB (EP A

Science Advisory Board, Environmental Engineering Committee), 2003. TCLP Consultation Summary , presented at the SAB Environmental Engineering Committee consultation with EP A, W ashington, D.C., June 17–18. Sanchez, F ., Kosson, D.S., 2005. Probabilistic Approach for Estimating the Release of Contaminants under Field Management Scenarios, W aste Management , 25 :5, 643–472. Senior , C, Bustard, C.J., Baldrey , K., S tarns, T . Durham, M., 2003a. “Characterization of Fly Ash From Full-Scale Demonstration of Sorbent Injection for Mercury Control on Coal-Fired Power Plants,” presented at the Combined Power Plant Air Pollutant Control Mega Symposium, W ashington D.C., May 19–22. Senior , C., Bustard, C.J., Durham, M., S tarns, T ., Baldrey , K, 2003b. “Characterization of Fly Ash From Full-Scale Demonstration of Sorbent Injection for Mercury Control on Coal-Fired Power Plants,” presented at the Air Quality IV Conference and Exhibition, W ashington D.C, September 22–27. Senior , C., Bustard, C.J., Durham, M., Baldrey , K., Michaud, D., 2004. Characterization of Fly Ash From Full-Scale Demonstration of Sorbent Injection For Mercury Control on Coal-Fired Power Plants, Fuel Pr ocessing T echnology , 85 :6–7, 601– 612. S tarns, T ., Bustard, J., Durham, M., Lindsey , C., Martin, C., Schlager , R., Donnelly , B., Sjostrom, S., Harrington, P
. , Haythornthwaite, S., Johnson, R., Morris, E., Change, R., Renninger , S., 2002. “Full-Scale T est of Mercury Control with Sorbent Injection and an ESP at W isconsin Electric’ s Pleasant Prairie Power Plant,” presented at the Air & W aste Management Association 95 th Annual Conference and Exhibition, Baltimore, MD, June 23–27. Thorneloe, S., 2003. Presentation to EP A

Science Advisory Board (Environmental Engineering Committee), W ashington, D.C., June 17 th
. V

idic, R.D., 2002. Combined Theoretical and Experimental Investigation of Mechanisms and Kinetics of V apor -Phase Mercury uptake by Carbonacoues Surfaces. Final Report, Grant No. DE-FG26-98FT401 19 to U.S. DOE, National Ener gy T echnology Laboratory
.



### 58Characterization of Coal Combustion Residues



# Appendix A U.S. EP A Science Advisory Board Consult ation Summary

This summary was prepared at the close of the June 2003 U.S. EP A

OSW and ORD consultation with the Science Advisory Board, Environmental Engineering Committee Review Panel. These comments do not represent formal con
sensus of the panel, and no consensus recommendations to the U.S. EP A

were prepared. These comments do present panel members views, with informal consensus on many points.

59Characterization of Coal Combustion Residues



## TCLP CONSUL T

A

TION SUMMAR Y

En vironmental Engineer ing Committee Science Advisor y Board U
. S
. En vironmantal Protection Agency W ashington, DC

J une 18, 2003

FOCUS

• 

## Alter nativ es to TCLP test f or use in w aste and site situations where TCLP test is not required b y regulation

• 

## F ocus Areas: contaminated site remediation; w aste mater ial reuse; w aste delisting

60Characterization of Coal Combustion Residues



## OVER VIEW

• 

## Fiv e specif ic consultation issues • 

## T w o gener al consultation issues • 

## Ke y f indings and recommendations

SPECIFIC CONSUL T

A

TION ISSUE 1 Laboratory testing conditions should, to the degree possible, anticip ate the plausible range of field conditions affecting waste leaching in disposal and reuse situations. These conditions will be most realistically represented by a distribution of values for factors affecting leaching, and testing should reflect this range of values to the degree possible

61Characterization of Coal Combustion Residues



## COMMENTS SPECIFIC CONSUL T

A

TION ISSUE 1

• Ag ree with statement; comments that f ollo w represent consensus of committee
• Statement should be related to some conte xtual use of leaching test
• Could e xpand probabilistic approach to include distr i b utions f or f ield proper ty par ameters
• Range of conditions considered depends on the intended use of the inf or mation; need conte xt
• Need to def ine what the target prob lems are
. What are we tr ying to f ix? Might be shor t list.
• EP A needs to def ine better what the objectiv es are f or the broader leaching fr ame wor k



## COMMENTS SPECIFIC CONSUL T

A

TION ISSUE 1

• 

## Unclear what is the cost of making no change
. • 

## Unclear to what e xtent o v er ly conser v ativ e classif ication aff ects benef icial reuse

• 

## Also need to consider w aste mater ial proper ties , e .g., ph ysical f o r m, presence of oil, etc.

• 

## Need to consider organics as w ell as metals

• 

## P erhaps can g roup w aste mater ials , consider categor ies

62Characterization of Coal Combustion Residues



## SPECIFIC CONSUL T

A

TION ISSUE 2 Conditions present at the end of a test (rather than initial test conditions) should be the basis for comp arison with field conditions.

COMMENTS SPECIFIC CONSUL T

A

TION ISSUE 2

• Statement indicates application is to dissolution of solids , and to assessment of max aqueous phase conc of released species f or pur poses other than w aste classif ication
• T o the e xtent that the test aims to achie v e equil conditions , end measurement is appropr iate
• Issue motiv ated b y the TCLP test, where f inal solution pH is not measured.
• Conditions in a reactor at equilibr ium or at the end of a f i x e d per iod of time are more rele v ant to the leaching measured in the reactor at the time of sampling than the initial condition.

63Characterization of Coal Combustion Residues



## SPECIFIC CONSUL T

A

TION ISSUE 3 For assessing met als leaching, pH is the strongest predictor of leaching potential in most cases. Other import ant factors include infiltration rate, liquid/solid ratio, redox environment, effect of common ions and ionic strength, effect s of external factors (co-disposed waste, biological activity , etc.), and exposure to ambient air . The relative import ance of these factors is likely to vary for different wastes.

COMMENTS SPECIFIC CONSUL T

A

TION ISSUE 3

• Redo x condition (Eh), organic matter , aging-after disposal are impor tant f actors not in current tests
• Microbes impor tant, b ut not in current tests; biotransf or mation can render solid phase metals solub l e
• Inclusion of microbes diff icult f or standard tests
• pH impor tant; not clear it is “strongest” predictor
• Depends on constituent; pure metals , organics influenced b y diff erent f actors
• R&D needed to be ab le to r ank par ameters
• Again, need to def ine objectiv es better

64Characterization of Coal Combustion Residues



## SPECIFIC CONSUL T

A

TION ISSUE 4 The development of multiple leaching test s, or a flexible testing framework is required. Selection of a suit able leaching test should be made based on a number of factors: anticip ated use of test result s, waste characterization, the range of plausible disposal or reuse conditions, and previously available information on the subject waste or similar wastes.
...

COMMENTS SPECIFIC CONSUL T

A

TION ISSUE 4

• F r ame w o r k of K osson et al. is fle xib le tiered approach that encompasses equilibr ium and kinetics and includes a suite of tests to address both, and allo ws f or site-specif ic and gener ic release estimates using mass tr ansf er modeling
• F r ame w o r k of K osson et al. is broad and potentially applicab le to broad range of wastes and disposal scenarios
• F r ame w o r k is open ended; it is a huge step be y ond a single leach test; the manner in which it will be implemented b y decisionmak ers needs to be clar i f ied
• Estab lishment of the fr ame w o r kf or implementation will be resource intensiv e ; EP A needs to justify the v alue of the inf or mation f or decisionmaking, as balanced against other w aste regulation needs
. • Need systematic approach f or applying fr ame w o r k
• Need w ell-def ined objectiv es f or fr ame wor k in order to de v elop step-b y-step guidance f or use



### 65Characterization of Coal Combustion Residues



## SPECIFIC CONSUL T

A

TION ISSUE 5 Modeling may also play an import ant role in relating laboratory and field conditions to one another , and in using leach test result s to assess the leaching potential of waste.

COMMENTS SPECIFIC CONSUL T

A

TION ISSUE 5

• Concer ned about use of deter ministic models f or prediction of leaching potential; probabilistic modeling will be more appropr iate in some cases , b u t is resource intensiv e
• Concer n about incor por ating modeling into leaching test protocol; connecting model to f ield diff icult
• Modeling of leaching test ma y be useful f or better understanding leach mechanisms , and connection of test with f ield
• F or cer tain w astes , coupling of leach tests with a model should be considered to predict solubilization o v er time , especially f or organics (Multiple equil. states ma y e xist)
• Usefulness of modeling depends on question to be ans wered; goals f o r leach e v al. need to be def ined



### 66Characterization of Coal Combustion Residues



## GENERAL CONSUL T

A

TION ISSUE 1 EP A

request s SAB reaction to current research, and the potential to apply it to improve p articular programs, specifically programs that do not now require the use of TCLP
.

COMMENTS GENERAL CONSUL T

A

TION ISSUE 1

• Capability to address organics , oily w astes , long-ter m reliability need to be incor por ated
• F r ame w o r k of K osson et al. is broadly applicab le; more de v elopment w o r k y e t needed (guidance f or specif ic applications , database f or f ield conditions and w aste types , data quality cr iter ia, data inter pretation/decisionmaking)
• F r ame w o r k of K osson et al. is responsiv e to the 1999 SAB commentar y , b ut to this point is limited to inorganics
• Current research proceeding without clear def inition of prob lem to be addressed b y alter nativ es to TCLP
• EP A should in v est in identifying areas where alter nativ e to TCLP is vitally needed

67Characterization of Coal Combustion Residues



## COMMENTS GENERAL CONSUL T

A

TION ISSUE 1
• Leaching-related research inside/outside EP A could be e xploited more

COMMENTS GENERAL CONSUL T

A

TION ISSUE 1

• Tiered str ucture of fr ame w o r k : enab les tr adeoffs in v alue of inf or mation
• EP A should pr ior itiz e R&D eff or ts based on assessment of the prob lem most in need of alter nativ es to the TCLP , e .g.,

SIf going to do e v aluation of prob lems dr iving TCLP alter nativ e s , tr y to ascer tain v alue of making a change , i.e ., economic analysis of prob lem

S Ev aluate w aste gener ation and management trends an projections as w ell as current situation

S Cost-benef it analysis ma y be diff icult; tr y to assess oppor tunity cost of not pursuing alt. to TCLP

68Characterization of Coal Combustion Residues



## GENERAL CONSUL T

A

TION ISSUE 2 EP A

requests SAB reaction to the direction for longterm research work to further develop fundament a l underst anding of leaching that would improve the predictive cap ability of test suites or testing frameworks.

COMMENTS GENERAL CONSUL T

A

TION ISSUE 2

• Goals f or long-ter m research not w ell def ined
• Increased fundamental kno wledge will yield long-ter m adv ancement in assessment of leaching
• Funding pr ior ity f or leaching research clear ly is lo w . • Long-ter m ORD research should be better coordinated with eff or ts inside/outside EP A, including DOD , FHW A, DOE
• Long-ter m ORD research is responsiv e to 1999 SAB commentar y in science f actors under study , b ut is f ocused on inorganics only and will benef it from clearer objectiv e s

69Characterization of Coal Combustion Residues



## COMMENTS GENERAL CONSUL T

A

TION ISSUE 2

• Prob lem def inition has tw o components

S

deter mine w aste categor ies and f ield situations most in need of TCLP alter nativ es

S

deter mine research pr ior ities f or the most impor tant w aste/f ield situations

COMMENTS GENERAL CONSUL T

A

TION ISSUE 2

• Organics , man uf actur ing process w astes , end-of lif e product w astes need to be considered
• Industr y/go v e r nment/academic research consor tium on leashing issues w ould be useful
• Industr y may be willing to co-fund leaching e v aluation R&D
• EP A should in v estigate collabor ativ e eff o r ts with European, Canadian, and J apanese researchers

70Characterization of Coal Combustion Residues



## KEY FINDINGS AND RECOMMENDA TIONS

• Alter nativ es to TCLP f or e v aluation of leach potential are needed f o r some w aste and site situations
• Not clear if there is large or small n umber of w aste and site situations f or which alter nativ e approach is needed
• F r ame w o r k of K osson et al. is broadly applicab le; more de v elopment w o r k y e t needed (guidance f or specif ic applications , database f or f ield conditions and w aste types , data quality cr iter ia, data inter pretation/decisionmaking)
• F r ame w o r k of K osson et al. is responsiv e to the 1999 SAB commentar y , b ut to this point is limited to inorganics



## KEY FINDINGS AND RECOMMENDA TIONS

• 

## Current research needs clear def inition of prob lem to be addressed b y alter nativ e to TCLP

• 

## EP A should in v est in identifying areas where alter nativ e to TCLP is vitally needed

• 

## The 1999 SAB commentar y f ocused on sciencebased issues in leaching: EP A has been responsiv e within resource limitations
. • 

## Organic w a ste constituents need to be considered, and a broader fr ame w o r k should include assessment or organic constituent leaching

71Characterization of Coal Combustion Residues



## KEY FINDINGS AND RECOMMENDA TIONS

• 

## Research and de v elopment should f ocus on most applicab le w a ste/site situations , and possib l e benef icial reuse scenar ios

• 

## Giv en limited R&D resources , EP A should pr ior itiz e research eff or ts and le v e r age DOD , DOE, FHW A interest in leaching through cross go vt coordination, as w ell as industr ial and inter national collabor ation

• 

## EP A intr a-agency eff or ts should be more closely link ed

72Characterization of Coal Combustion Residues



# Appendix B DOE NETL Full-Scale T est Site Flo w Dia grams

73Characterization of Coal Combustion Residues 

## Bra yton P oint Unit 1

• Carbon injected upstream of second ESP (Research Cottrell). Only 1⁄2 of the unit was treated, or carbon was injected

into one of the two new ESPs (Research Cottrell ESPs).


### • Hopper IDs also shown. Samples from C-row are from the first row of hoppers in the second ESP
.

74Characterization of Coal Combustion Residues


### • Bird’ s eye view of second ESP
. 

### • Samples taken from C-raw hoppers.

75Characterization of Coal Combustion Residues 

## Pleasant Prairie Unit 2 Carbon injected upstream of cold-side ESP . Only 1⁄4 of the unit was treated. T est ESPwas ESP 2-4.

ES P 2-4

S p ra y C o o lin g Ca r bon I n j e c t i o n



### SCEM I n l e t SCEM Out l et o n v e r t i c al dr o p ES P 2-4

S p ra y C o o lin g Ca r bon I n j e c t i o n



### SCEM I n l e t SCEM Out l et o n v e r t i c al dr o p

76Characterization of Coal Combustion Residues 

## Salem Harbor Unit 1 Carbon injected upstream of cold-side ESP . Row-A hoppers were the front hoppers.

Lo n g A i r He a t e r Sh o r t A

i r He a t e r 

### I. D . Fa n F. D . Fa n S t e a m C o ils 

# ES P B o iler

Lo n g A i r He a t e r Sh o r t A

i r He a t e r Lo 

### I. D . Fa n F. D . Fa n S t e a m C o ils 

# ES P B o iler

n g A i r He a t e r Sh o r t A

i r He a t e r 

### I. D . Fa n F. D . Fa n S t e a m C o ils 

# ES P B o iler Carbon Injection P oint



## Facility C Carbon injected upstream of Unit 3B COHP AC baghouse (in between hot-side ESPand baghouse)

77Characterization of Coal Combustion Residues 

## St. Clair

T o tal fl ow fr om b o ile r / e c o n im i z e r 

### To tal Flo w to Sta c k N or th- S i d e CS -ES P ( ESP B)

South- Sid e CS- E S P ( ESP A)


### B
- PAC in je ctio n



## Facility L B- PAC in je ction

T o tal f l o w f r om b o iler / ec o n imize r To B S t ac k B- Si de HS-E SP ( E SP B)



### To A Stac k A- si de HS- E SP ( E SP A)



### 78Characterization of Coal Combustion Residues



# Appendix C Quality Assurance Project Plan

7 9Characterization of Coal Combustion Residues



### 8 0Characterization of Coal Combustion Residues



### 8 1Characterization of Coal Combustion Residues



### 8 2Characterization of Coal Combustion Residues



### 8 3Characterization of Coal Combustion Residues



### 8 4Characterization of Coal Combustion Residues



### 8 5Characterization of Coal Combustion Residues



### 8 6Characterization of Coal Combustion Residues



### 8 7Characterization of Coal Combustion Residues



### 8 8Characterization of Coal Combustion Residues



### 8 9Characterization of Coal Combustion Residues



### 9 0Characterization of Coal Combustion Residues



### 9 1Characterization of Coal Combustion Residues



### 9 2Characterization of Coal Combustion Residues



### 9 3Characterization of Coal Combustion Residues



### 9 4Characterization of Coal Combustion Residues



### 9 5Characterization of Coal Combustion Residues



### 9 6Characterization of Coal Combustion Residues



### 9 7Characterization of Coal Combustion Residues



### 9 8Characterization of Coal Combustion Residues



### 9 9Characterization of Coal Combustion Residues



### 100Characterization of Coal Combustion Residues



### 101Characterization of Coal Combustion Residues



### 102Characterization of Coal Combustion Residues



### 103Characterization of Coal Combustion Residues



### 104Characterization of Coal Combustion Residues



### 105Characterization of Coal Combustion Residues



### 106Characterization of Coal Combustion Residues



### 107Characterization of Coal Combustion Residues



### 108Characterization of Coal Combustion Residues



### 109Characterization of Coal Combustion Residues



### 110Characterization of Coal Combustion Residues



### 111Characterization of Coal Combustion Residues



### 112Characterization of Coal Combustion Residues



### 113Characterization of Coal Combustion Residues



### 114Characterization of Coal Combustion Residues



### 115Characterization of Coal Combustion Residues



# Appendix D Bra yton P oint Fl y Ashes

116Characterization of Coal Combustion Residues



# List of Figures Figure Page D
- 1 pH T itration Curves for the Baseline Fly Ash and the Fly Ash with Enhanced Hg Control
....................................... ........ 1 1 8 D
-

2 pH as a Function of LS Ratio for the Baseline Fly Ash and the Fly Ash with Enhanced Hg Control
.............................. ... 1 1 8 D
- 3 Mercury Release (top) and Spike Recoveries (bottom) as a Function of pH for the Baseline Fly Ash and the Fly Ash with Enhanced Hg Control
............................................................................................... ..................................... 1 1 9 D
-

4 Mercury Release (top) and Spike Recoveries (bottom) as a Function of LS Ratio for the Baseline Fly Ash and the Fly Ash with Enhanced Hg Control
........................................................................................... ................................... 1 2 0 D
- 5 Arsenic Release (top) and Spike Recoveries (bottom) as a Function of pH for the Baseline Fly Ash and the Fly Ash with Enhanced Hg Control
............................................................................................... ..................................... 1 2 1 D
- 6 Arsenic Release (top) and Spike Recoveries (bottom) as a Function of LS Ratio for the Baseline Fly Ash and the Fly Ash with Enhanced Hg Control
....................................................................................... ................................ 1 2 2 D
- 7 Selenium Release (top) and Spike Recoveries (bottom) as a Function of pH for the Baseline Fly Ash and the Fly Ash with Enhanced Hg Control
............................................................................................... ..................................... 1 2 3 D
- 8 Selenium Release (top) and Spike Recoveries (bottom) as a Function of LS Ratio for the Baseline Fly Ash and the Fly Ash with Enhanced Hg Control
....................................................................................... ................................ 1 2 4 D
- 9 Regression Curves of Experimental Data of Arsenic Solubility as a Function of pH.
........................................... .............. 1 2 5 D-10 Regression Curves of Experimental Data of Selenium Solubility as a Function of pH
.............................................. .......... 1 2 6 D-11 100-Y ear Arsenic Release Estimates as a Function of the Cumulative Probability for the Scenario of Disposal ina Combustion W aste Landfill
................................................................................................. ......................................... 1 27 D-12 100-Y ear Selenium Release Estimates as a Function of the Cumulative Probability for the Scenario of Disposal ina Combustion W aste Landfill
................................................................................................. ......................................... 1 27 D-13 100-Y ear Arsenic Release Estimates from A) Baseline Fly Ash and B) Fly Ash with ACI
............................................ ....... 1 2 8 D-14 1 0 0-year Selenium Release Estimates from A) Baseline Fly Ash and B) Fly Ash with ACI
............................................. .... 1 29



### 117

### 6 

## pH Titration Curves Baseline Fly Ash Fly Ash with ACI 14 

### 14 12.2 

### 12 12 9.5 10 

### 10

8 8pHpH 6 4 

### 4 2



### -12 -10 -8 -6 -4 -2 0 2 4 6 8 -2 -1.5 -1 -0.5 0 0.5 1 1.5 

### meq Acid/g dry meq Acid/g dry 

### 2

SR2-BPB-0001 - A SR2-BPB-0001 - B SR2-BPB-0001 - C SR2-BPT-0001 - A SR2-BPT-0001 - B SR2-BPT-0001 - C



### 14 Baseline Fly Ash 

### 14 Fly Ash with ACI


### 12 12 

### 10 10



### 6 6 

### 4 4 

### 2 2 

### 0 2 4 6 8 10 12 0 2 4 6 8 10 12 

### LS ratio [mL/g] LS ratio [mL/g] 

### SR3-BPB- 0001 - A SR3-BPB- 0001 - B SR3-BPB- 0001 - C SR3-BPT-0001 - A SR3-BPT-0001 - B SR3-BPT-0001 - CpHpH 

### 8 8 Characterization of Coal Combustion Residues

Figure D-1. pH Titr ation Cur v es f or the Baseline Fly Ash and the Fly Ash with Enhanced Hg Control. 

## pH as a Function of LS Ratio

Figure D-2. pH as a Function of LS Ratio for the Baseline Fly Ash and the Fly Ash with Enhanced Hg Control. 

### 118

## Mercury Release as a Function of pH Baseline Fly Ash Fly Ash with ACI

*Total content as determined by digestion using method 3052. MDL ML 9.5 0.006

MCL

0.001

0.01 1 10

2 4 6 8 10 12 14 pH SR2-B PT-0001 - A SR2-B PT-0001 - B SR2-B PT-0001 - C 5% 95% 5% Hg total content*: 1529.6 ! 1.1 ng/g

MDL ML 12.2 MCL

0.001

0.01 1 10

2 4 6 8 10 12 14 pH SR2-BP B-0001 - A SR2-BP B-0001 - B SR2-BP B-0001 - C 5% 95% 5% 95% Hg total content*: 650.6 ! 6.8 ng/g



### 140 150 140 150Hg [ μg/ L]Hg [μ g/L]Hg spike recovery [%] 0.1 0.1 95% 0.035Hg spike recovery [%] 

### 130

120 110 100

90 80 70 130 120 110 100

90 80 70 

### 60 60 

### 2 4 6 8 10 12 14 2 4 6 8 10 12 14 

### pH pH 

### SR2-BPB- 0001 - A SR2-BPT-0001 - A Characterization of Coal Combustion Residues

Figure D-3. Mercury Release (top) and Spike Recoveries (bottom) as a Function of pH for the Baseline Fly Ash and the Fly Ash with Enhanced Hg Control. 5 th and 95 th percentiles of mercury concentrations observed in typical combustion waste landfill leachate are shown for comparison.



### 119Baseline Fly Ash Fly Ash with ACI MCL 

### 0.02 MCL 

### 0.02 0.015 0.015Hg spike recovery [%]Hg [μg/L]Hg spike recovery [%]Hg [μg/L]



### 0.01 0.01 0.005 0.005 0 0 ML 

### 0 2 4 6 8 10 12 0 2 4 6 8 10 12 MDL 

### LS ratio [mL/g] SR3-BPB-0001 - A SR3-BPB-0001 - B SR3-BPB-0001 - C
150 140 ML MDL



### 150 140 

### LS ratio [mL/g] SR3-BPT-0001 - A SR3-BPT-0001 - B SR3-BPT-0001 - C

130 120 110 100

90 80 70 

### 130 120 110 100

90 80 70 60 50 60 

### 40 50 

### 30 0 2 4 6 8 10 12 

### 0 2 4 6 8 10 12 LS ratio [mL/g] 

### LS ratio [mL/g] SR3-BPB-0001 - A 

### SR3-BPT-0001 - A Characterization of Coal Combustion Residues 

## Mercury Release as a Function of LS Ratio

Figure D-4. Mercury Release (top) and Spike Recoveries (bottom) as a Function of LS Ratio for the Baseline Fly Ash and the Fly Ash with Enhanced Hg Control.



### 120Baseline Fly Ash Fly Ash with ACI



### 140 150 MDL ML 9.5 MCL



### 0.001

0.01

10 100 1000 10000

2 4 6 8 10 12 14 pH SR2-BPT-0001 - A SR2-BPT-0001 - B SR2-BPT-0001 - C 5% 95% 95% As total content*: 27.9 ! 2.1 : g/g

MDL ML 12.2 MCL



### 0.001

0.01 1 10 100 1000 10000

2 4 6 8 10 12 14 pH SR2-BPB-0001 - A SR2-BPB-0001 - B SR2-BPB-0001 - C 5% 95% 5% 95% As total content*: 80.5 ! 1.9 : g/g

*Total content as determined by digestion using method 3052. 

### 140 150As [μg/L]As [μg/L]As spike recovery [%] 6.67 4.8 5% 

### 1 0.1 

### 0.1As spike recovery [%] 

### 130 120 110 100

90 80 70 

### 130 120 110 100

90 80 70 60 2 4 6 8 10 12 14 

### 2 4 6 8 10 12 14 pH 

### pH 60



### SR2-BPT-0001 - A SR2-BPB-0001 - A Characterization of Coal Combustion Residues 

## Arsenic Release as a Function of pH

Figure D-5. Arsenic Release (top) and Spike Recoveries (bottom) as a Function of pH for the Baseline Fly Ash and the Fly Ash with Enhanced Hg Control. 5 th and 95 th percentiles of arsenic concentrations observed in typical combustion waste landfill leachate are shown for comparison.



### 121Baseline Fly Ash Fly Ash with ACI

MCL


### 0 5 10 15 20 25 30 35 40As [μg/L]

MCL 

### 0 5 10 15 20 25 30 35 40As [μg/L]



### 0 2 4 6 8 10 12 0 2 4 6 8 10 12 ML 

### LS ratio [mL/g] ML 

### LS ratio [mL/g] MDL MDL 

### SR3-BPB-0001 - A SR3-BPB-0001 - B SR3-BPB-0001 - C SR3-BPT-0001 - A SR3-BPT-0001 - B SR3-BPT-0001 - C
150 

### 150 140 

### 140As spike recovery [%] 

### 130 120 110 100

90 80 70As spike recovery [%] 

### 130 120 110 100

90 80 70 60 

### 60 0 2 4 6 8 10 12 

### 0 2 4 6 8 10 12 LS ratio [mL/g] 

### LS ratio [mL/g] SR3-BPB-0001 - A 

### SR3-BPT-0001 - A Characterization of Coal Combustion Residues 

## Arsenic Release as a Function of LS Ratio

Figure D-6. Arsenic Release (top) and Spike Recoveries (bottom) as a Function of LS Ratio for the Baseline Fly Ash and the Fly Ash with Enhanced Hg Control.



### 122Baseline Fly Ash Fly Ash with ACI Se total content*: 51.4 ! 1.7 : g/g Se total content*: 51.4 ! 1.7 : g/g 10000 

### 10000

1000 

### 1000 95% 164.3 95% 100 

### 100 MCL 57 MCL

0.01 

### 0.01 0.001 2 4 5% 6 8 10 95% 12

12.2 14 

### 0.001 5% 9.5 95% 

### 2 4 6 8 10 12 14 ML pH ML 

### pH MDL SR2-BPB-0001 - A SR2-BPB-0001 - B SR2-BPB-0001 - C MDL 

### SR2-BPT-0001 - A SR2-BPT-0001 - B SR2-BPT-0001 - C *Total content as determined by digestion using method 3052. 

### 150 150 140 

### 140

10Se [μg/L] 

### 10Se [μg/L]Se spike recovery [%] 5% 5% 1 

### 1 0.1 

### 0.1



### 130 120 110 100

90 80 70 

### 130 120 110 100

90 80 70Se spike recovery [%]



### 60 

### 2 4 6 8 10 12 14 2 4 6 8 10 12 14 

### pH pH 

### 60

SR2-BPB-0001 - A SR2-BPT-0001 - A Characterization of Coal Combustion Residues 

## Selenium Release as a Function of pH

Figure D-7. Selenium Release (top) and Spike Recoveries (bottom) as a Function of pH for the Baseline Fly Ash and the Fly Ash with Enhanced Hg Control. 5 th and 95 th percentiles of selenium concentrations observed in typical combustion waste landfill leachate are shown for comparison.



### 123Baseline Fly Ash Fly Ash with ACI 

### 600 

### 600 500 

### 500 400 

### 400Se spike recovery [%]Se [μg/L]Se spike recovery [%]Se [μg/L] 

### 300 

### 300 200 

### 200 100 

### 100 MCL MCL 

### 0 

### 0 0 2 4 6 8 10 12 

### 0 2 4 6 8 10 12 ML 

### LS ratio [mL/g] ML 

### LS ratio [mL/g] MDL MDL 

### SR3-BPB-0001 - A SR3-BPB-0001 - B SR3-BPB-0001 - C SR3-BPT-0001 - A SR3-BPT-0001 - B SR3-BPT-0001 - C
150 150 

### 140 140 

### 130 120 110 100

90 80 70 130 120 110 100

90 80 70 

### 60 0 2 4 6 8 10 12 

### 0 2 4 6 8 10 12 LS ratio [mL/g] 

### LS ratio [mL/g] 60

SR3-BPB-0001 - A 

### SR3-BPT-0001 - A Characterization of Coal Combustion Residues 

## Selenium Release as a Function of LS Ratio

Figure D-8. Selenium Release (top) and Spike Recoveries (bottom) as a Function of LS Ratio for the Baseline Fly Ash and the Fly Ash with Enhanced Hg Control.



### 124Baseline Fly Ash Fly Ash with ACI 

### 100000 

### 100000

10000 

### 10000

1000 

### 1000

0.1 

### 0.1 0.01 

### 0.01 5% 95% 

### 5% 95% 95% 

### 95% 5% 100 

### 100As [μg/L]As [μg/L]



### 10 

### 10 5% 1 

### 1

0.001 

### 0.001 2 4 6 8 10 12 14 

### 2 4 6 8 10 12 14 pH 

### pH SR2-BPB-0001-A 

### SR2-BPT-0001-A SR2-BPB-0001-B 

### SR2-BPT-0001-B SR2-BPB-0001-C 

### SR2-BPT-0001-C A) Fit curve 

### B) Fit curve
Material log As ( μ g/L) pH range of R 2 Number of validity points BPB 0.0004 pH 5 -0.0135 pH 4 0.1634 pH 3 3-14 0.77 27 -0.8130 pH 2 1.1609 pH 2.7085 BPT 0.0005 pH 5 -0.0207 pH 4 0.3035 pH 3 3-12.5 0.98 33 -2.0113 pH 2 5.4552 pH -2.7126 Characterization of Coal Combustion Residues 

## Arsenic Solubility

Figure D-9. Regression Curves of Experimental Data of Arsenic Solubility as a Function of pH.



### 125Baseline Fly Ash Fly Ash with ACI 

### 100000 100000

10000 10000

1000 1000 95% 95% 5% 100 100Se [μg/L]Se [μg/L]



### 10 10 5% 1 1 0.1 0.1 0.01 0.01 0.001 0.001 5% 95% 5% 95% 2 4 6 8 10 12 14 2 4 6 8 10 12 14 pH pH SR2-BPB-0001-A SR2-BPB-0001-B SR2-BPB-0001-C Fit curve B) A) SR2-BPT-0001-A SR2-BPT-0001-B SR2-BPT-0001-C Fit curve
Material log Se ( μ g/L) pH range of R 2 Number of validity points BPB -0.0006 pH 5 0.0262 pH 4 -0.4379 pH 3 3-14 0.81 27 3.3856 pH 2 -12.0291 pH 17.7907 BPT -0.0006 pH 5 0.0229 pH 4 -0.3475 pH 3 3-12.5 0.93 33 2.4521 pH 2 -7.9388 pH 11.4439 Characterization of Coal Combustion Residues 

## Selenium Solubility

Figure D-10. Regression Curves of Experimental Data of Selenium Solubility as a Function of pH.



### 126

### 10000 1000 Mt min Mt - 5% Mt - 50% 

### 100

10 Mt - 95% Mean Mt 

### 1 Mt max 

### 0.1 5% 50% 95% 0 20 40 60 80 100 Percentile100-year Mt [μg/kg] BPB BPT μ g/kg % μ g/kg 0.2 0.0003 0.1 0.9 0.0011 0.1 152 0.2 22 2095 2.6 338

468 0.6 90 4693 5.8 10157 % 0.0003 0.0005 0.0772 1.2 0.3 36.4



### BPB BPT

100000 BPB BPT



### 10000100-year Mt [μg/kg] μ g/kg % μ g/kg % Mt min 1.5 0.003 5.9 0.004 

### 1000 Mt - 5% Mt - 50% 

### 100 Mt - 95% Mean Mt 

### 10 Mt max



### 1 0.1 5% 50% 95% 0 20 40 60 80 100 Percentile BPB BPT 7.6 1031 16681

3573 45169 0.015 2.0 32.5

7.0 87.9 10.0 1661 23931

6038 151900 0.007 1.1 15.8

4.0 100.0 Characterization of Coal Combustion Residues 

## 100-Y ear Arsenic Release Estimates

Figure D-11. 100-Y ear Arsenic Release Estimates as a Function of the Cum ulativ e Probability f or the Scenar io of Disposal in a Comb ustion W aste Landf ill.



## 100-Y ear Selenium Release Estimates

Figure D-12. 100-Y ear Selenium Release Estimates as a Function of the Cum ulativ e Probability f o r the Scenar io of Disposal in a Comb ustion W aste Landf ill. 

### 127BPB - Arsenic 80500 μ g/kg 100%

2095 μ g/kg 2.6% 2439 μ g/kg 3.0% 105 μ g/kg 0.1% 83 μ g/kg 0.1%

1 10 100 1000 10000 100000100-year arsenic release [μg/kg]
MCL LS 95% = 1000 : g/kg MCL LS 12.5 = 125 : g/kg

Total content Combustion Default - pH 3 Default -pH Default ­ Waste Landfill - 12.5 Natural pH 95% confidence 12.2 A)

BPT - Arsenic

60 μ g/kg 0.2% 999 μ g/kg

3.6% 1981 μ g/kg 7.1% 338 μ g/kg 1.2% 27900 μ g/kg 100%

1 10 100 1000 10000 100000100-year arsenic release [μg/kg]
MCL LS 95% = 1000 : g/kg MCL LS 12.5 = 125 : g/kg

Total content Combustion Default - pH 3 Default -pH Default ­ Waste Landfill ­ 12.5 Natural pH 95% confidence 9.5 B) Characterization of Coal Combustion Residues 

## 100-Y ear Ar senic Release Estimates

Figure D-13. 100-Y ear Arsenic Release Estimates from A) Baseline Fly Ash and B) Fly Ash with A CI. Release estimates f or percolation controlled scenar io are compared to release estimate based on total content. The amount of the arsenic that would be released if the release concentration was at the MCL is also shown for comparison (LS default scenario = 12.5 L/kg and LS 95% = 100 L/kg). 

### 128BPB - Selenium 51400 μ g/kg

MCL LS 95% = 5000 : g/kg MCL LS 12.5 = 625 : g/kg 713 μ g/kg 1.4% 3226 μ g/kg 6.3% 2667 μ g/kg 5.2% 16681 μ g/kg 32.5% 100%

1 10 100 1000 10000 100000100-year selenium release [μg/kg]

Total content Combustion Default - pH 3 Default -pH Default ­ Waste Landfill ­ 12.5 Natural pH 95% confidence 12.2 A)
BPT - Selenium 151900 μ g/kg

2054 μ g/kg 1.4% 43479 μ g/kg 28.6% 1347 μ g/kg 0.9% 23931 μ g/kg 15.8% 100%

1 10 100 1000 10000 100000 1000000100-year selenium release [μg/kg] MCL LS 95% = 5000 : g/kg MCL LS 12.5 = 625 : g/kg

Total content Combustion Default - pH 3 Default -pH Default ­ Waste Landfill ­ 12.5 Natural pH 95% confidence 9.5 B) Characterization of Coal Combustion Residues 

## 100-Y ear Selenium Release Estimates

Figure D-14. 100-year Selenium Release Estimates from A) Baseline Fly Ash and B) Fly Ash with ACI. Release estimates f or percolation controlled scenar io are compared to release estimate based on total content. The amount of the selenium that would be released if the release concentration was at the MCL is also shown for comparison (LS default scenario = 12.5 L/kg and LS 95% = 100 L/kg). 

### 129Characterization of Coal Combustion Residues 

## Comments Figure D-3:

• The fly ash from the test case had greater total Hg

content than the fly ash from the baseline case (by about 2.5 times).


### • Hg release is low (but poor replication) for both baseline

and test cases. 

### Figure D-5:

• The fly ash from the test case had lower total As con
tent than the fly ash from the baseline case (by about a factor of 3).


### • The laboratory measurements fit within the 5-95% con
fidence intervals of the field observations.


### • As release is most frequently worse in baseline case

than test case and exceeds MCL for many possible conditions. 

### Figure D-7:

• The fly ash from the test case had greater total Se

content than the fly ash from the baseline case (by about a factor of 3).


### • The laboratory measurements fit within the 5% to 95%

confidence intervals of the field observations.


### • Se release substantially exceeds MCL for both baseline

and test cases and is generally worse for test cases.


### • The fly ash from the test case resulted in greater Se

concentration at the natural pH of the material than the baseline case (by about 3 times). 

### Figures D-1 1. and D-12:

• The fly ash from the test case would result in As re
lease less than expected from the baseline case, with a 95% probability to be less than 338 and 2095 : g/kg, respectively
. 

### • No significant difference in Se release is expected from

both baseline and test cases. 

### Figure D-13:

• For the 95% probability scenario, arsenic release from

the baseline case would be greater than the amount that would be released if the release concentration was at the MCL.


### • For the 95% probability scenario, a lower arsenic re
lease would be expected from the test case. However , the fly ash from the test case had lower total As con
tent than the fly ash from the baseline case (by about a factor of 3).


### • For the default scenario corresponding to disposal in a

monofill (leachate pH controlled by the material being disposed), no significant difference in arsenic release between the baseline and the test cases would be ex
pected. Additionally , arsenic release would be less than the amount that would be released if the release con
centration was at the MCL.


### • For the default scenario corresponding to the “extreme”

pH of 3, arsenic release would be greater than the amount that would be released if the release concen
tration was at the MCL, for both the baseline and the test cases. 

### • For the default scenario corresponding to the “extreme”

pH of 12.5, arsenic release is expected to be greater for the test case than the baseline case. 

### Figure D-14:

• For the 95% probability case, selenium release would

be greater than the amount that would be released if the release concentration was at the MCL for both the baseline and the test cases.


### • For the default scenario corresponding to disposal in a

monofill (leachate pH controlled by the material being disposed), a greater selenium release would be ex
pected from the test case.


### • For the default scenario corresponding to the “extreme”

pH of 12.5, selenium release is expected to be greater for the test case than the baseline case. Selenium re
lease from the test case would be greater than the amount that would be released if the release concen
tration was at the MCL.

130Characterization of Coal Combustion Residues



# Appendix E Pleasant Prairie Fl y Ashes

131Characterization of Coal Combustion Residues



# List of Figures Figure Page E

- 1 pH T itration Curves for the Baseline Fly Ash and the Fly Ash with Enhanced Hg Control
....................................... ........ 1 3 3 E

- 2 pH as a Function of LS Ratio for the Baseline Fly Ash and the Fly Ash with Enhanced Hg Control
.............................. ... 1 3 3 E

- 3 Mercury Release (top) and Spike Recoveries (bottom) as a Function of pH for the Baseline Fly Ash and the Fly Ash with Enhanced Hg Control
............................................................................................... ..................................... 1 3 4 E

- 4 Mercury Release (top) and Spike Recoveries (bottom) as a Function of LS Ratio for the Baseline Fly Ash and the Fly Ash with Enhanced Hg Control
........................................................................................... ................................... 1 3 5 E

-5 Arsenic Release (top) and Spike Recoveries (bottom) as a Function of pH for the Baseline Fly Ash and the Fly Ash with Enhanced Hg Control
............................................................................................... ..................................... 1 3 6 E

- 6 Arsenic Release (top) and Spike Recoveries (bottom) as a Function of LS Ratio for the Baseline Fly Ash and the Fly Ash with Enhanced Hg Control
....................................................................................... ................................ 1 3 7 E

- 7 Selenium Release (top) and Spike Recoveries (bottom) as a Function of pH for the Baseline Fly Ash and the Fly Ash with Enhanced Hg Control
............................................................................................... ..................................... 1 3 8 E

- 8 Selenium Release (top) and Spike Recoveries (bottom) as a Function of LS Ratio for the Baseline Fly Ash and the Fly Ash with Enhanced Hg Control
....................................................................................... ................................ 1 3 9 E

- 9 Regression Curves of Experimental Data of Arsenic Solubility as a Function of pH.
........................................... .............. 1 4 0 E

- 1 0 Regression Curves of Experimental Data of Selenium Solubility as a Function of pH
.......................................... .............. 1 4 1 E

- 1 1 100-Y ear Arsenic Release Estimates as a Function of the Cumulative Probability for the Scenario of Disposal ina Combustion W aste Landfill
................................................................................................. ......................................... 1 4 2 E

- 1 2 100-Y ear Selenium Release Estimates as a Function of the Cumulative Probability for the Scenario of Disposal ina Combustion W aste Landfill
................................................................................................. ......................................... 1 4 2 E

- 1 3 100-Y ear Arsenic Release Estimates from A) Baseline Fly Ash and B) Fly Ash with ACI
........................................ ........... 1 4 3 E

- 1 4 100-year Selenium Release Estimates fr om A) Baseline Fly Ash and B) Fly Ash with ACI
....................................... .......... 1 4 4



### 132

## pH Titration Curves Baseline Fly Ash Fly Ash with ACI 14 

### 14 12 12 11.9 11.2



### 10 10



### 8 8pHpH 

### 6 4 2 -2 0 2 4 6 8 10 meq Acid/g dry SR2-PPB-0001 - A SR2-PPB-0001 - B SR2-PPB-0001 - C 6 4 2 -4 -2 0 2 4 6 meq Acid/g dry SR2-PPT-0001 - A SR2-PPT-0001 - B SR2-PPT-0001 - C 8



## pH as a Function of LS Ratio Baseline Fly Ash 

### 14 12 10 Fly Ash with ACI 

### 14 12 10

4 

### 4 2 

### 2 0 2 4 6 8 10 12 

### 0 2 4 6 8 10 12 LS ratio [mL/g] 

### LS ratio [mL/g] SR3-PPB-0001 - A SR3-PPB-0001 - B SR3-PPB-0001 - C 

### SR3-PPT-0001 - A SR3-PPT-0001 - B SR3-PPT-0001 - CpHpH 

### 8 6 

### 8 6 Characterization of Coal Combustion Residues

Figure E-1. pH Titration Cur v es f or the Baseline Fly Ash and the Fly Ash with Enhanced Hg Control.

Figure E-2. pH as a Function of LS Ratio for the Baseline Fly Ash and the Fly Ash with Enhanced Hg Control. 

### 133Baseline Fly Ash Fly Ash with ACI Hg total content*: 157.7 ! 0.2 ng/g Hg total content*: 1180.1 ! 1.2 ng/g 10 

### 10 MCL MCL 1



### 1

11.2 0.011



### 2 4 6 8 10 12 14 5% 95% 95%

11.9 95% 5% 5%Hg [μg/L]Hg spike recovery [%]Hg [μg/L] 0.1 

### 0.1 95% 0.011 0.01 

### 0.01 0.001 

### 0.001 5% 2 4 6 8 10 12 14 pH 

### pH ML ML SR2-PPT-0001 - A SR2-PPT-0001 - B SR2-PPT-0001 - C 

### SR2-PPB-0001 - A SR2-PPB-0001 - B SR2-PPB-0001 - C MDL MDL
*Total content as determined by digestion using method 3052. 

### 150 

### 150 140 

### 140 130 120 110 100

90 80 70 

### 130 120 110 100

90 80 70Hg spike recovery [%]



### 60 2 4 6 8 10 12 14 

### 2 4 6 8 10 12 14 pH 

### pH 60

SR2-PPB-0001 - A 

### SR2-PPT-0001 - A 

## Mercury Release as a Function of pH Characterization of Coal Combustion Residues

Figure E-3. Mercury Release (top) and Spike Recoveries (bottom) as a Function of pH for the Baseline Fly Ash and the Fly Ash with Enhanced Hg Control. 5 th and 95 th percentiles of mercury concentrations observed in typical combustion waste landfill leachate are shown for comparison.



### 134

## Mercury Release as a Function of LS Ratio Baseline Fly Ash Fly Ash with ACI MCL 

### 0.02 MCL 

### 0.02 0.015 0.015Hg spike recovery [%]Hg [μg/L]Hg spike recovery [%]Hg [μg/L]



### 0.01 0.01 0.005 

### 0.005 0 0 

### 0 2 4 6 8 10 12 0 2 4 6 8 10 12 ML 

### LS ratio [mL/g] MDL 

### SR3-PPB-0001 - A SR3-PPB-0001 - B SR3-PPB-0001 - C
150 140 130 120 110 100

90 80 70 

### LS ratio [mL/g] SR3-PPT-0001 - A SR3-PPT-0001 - B SR3-PPT-0001 - C ML MDL



### 150 140 130 120 110 100

90 80 70 

### 60 60 

### 0 2 4 6 8 10 12 0 2 4 6 8 10 12 

### LS ratio [mL/g] LS ratio [mL/g] 

### SR3-PPB-0001 - A SR3-PPT-0001 - A Characterization of Coal Combustion Residues

Figure E-4. Mercury Release (top) and Spike Recoveries (bottom) as a Function of LS Ratio for the Baseline Fly Ash and the Fly Ash with Enhanced Hg Control.



### 135

## Arsenic Release as a Function of pH Baseline Fly Ash Fly Ash with ACI As total content*: 21.3 ! 0.3 : g/g As total content*: 24.0 ! 0.8 : g/g 

### 10000 

### 10000 1000 95% 

### 100 

### 1000 95%



### 100 MCL MCL 4.2 5%


### 0.01 

### 0.01 0.001 

### 0.001 5% 11.9 95% 5% 95% 11.2 

### 2 4 6 8 10 12 14 2 4 6 8 10 12 14 

### pH ML 

### pH ML MDL 

### SR2-PPB-0001 - A SR2-PPB-0001 - B SR2-PPB-0001 - C MDL 

### SR2-PPT-0001 - A SR2-PPT-0001 - B SR2-PPT-0001 - C *Total content as determined by digestion using method 3052. 

### 150 

### 150 140 

### 140 10 

### 10

4As [μg/L]As spike recovery [%]As [μg/L] 5% 

### 1 

### 1 0.1 

### 0.1



### 2 4 6 8 10 12 14 pH 

### 2 4 6 8 10 12 14 pH 130 120 110 100

90 80 70 

### 130 120 110 100

90 80 70 60As spike recovery [%]



### 60

SR2-PPB-0001 - A 

### SR2-PPT-0001 - A Characterization of Coal Combustion Residues

Figure E-5. Arsenic Release (top) and Spike Recoveries (bottom) as a Function of pH for the Baseline Fly Ash and the Fly Ash with Enhanced Hg Control. 5 th and 95 th percentiles of arsenic concentrations observed in typical combustion waste landfill leachate are shown for comparison.



### 136

## Arsenic Release as a Function of LS Ratio Fly Ash with ACI Baseline Fly Ash 

### 20 20 

### 15 15

0 2 4 6 8 10 12 LS ratio [mL/g] 

### 5 5 

### 0 ML ML MDL MDL 0 

### 0 2 4 6 8 10 12 LS ratio [mL/g] SR3-PPB-0001 - A SR3-PPB-0001 - B SR3-PPB-0001 - C 

### SR3-PPT-0001 - A SR3-PPT-0001 - B SR3-PPT-0001 - C


### 150 150 140 140As spike recovery [%]As [μg/L]As spike recovery [%]As [μg/L] MCL MCL 

### 10 10



### 130 130 120 120 110 110 100 100 90

90 80 80 70 70 60 60 0 2 4 6 8 10 12 0 2 4 6 8 10 12 LS ratio [mL/g] LS ratio [mL/g]
SR3-PPB-0001 - A SR3-PPT-0001 - A Characterization of Coal Combustion Residues

Figure E-6. Arsenic Release (top) and Spike Recoveries (bottom) as a Function of LS Ratio for the Baseline Fly Ash and the Fly Ash with Enhanced Hg Control.



### 137

## Selenium Release as a Function of pH Baseline Fly Ash Fly Ash with ACI Se total content*: <4.0 : g/g Se total content*: <4.0 : g/g 

### 10000 

### 10000 1000



### 1000 110.9 95% 95% 

### 100 

### 100 MCL MCL

11.2 

### 2 4 6 8 10 12 14 5% 95% 

### 0.01 

### 0.01 25.3 

### 10 

### 10Se [μg/L]Se [μg/L] 5% 5% 

### 1 1 0.1 

### 0.1
0.001 

### 0.001 11.9 5% 95% 

### 4 6 12 2 8 10 14 ML 

### pH ML 

### pH SR2-PPB-0001 - A SR2-PPB-0001 - B SR2-PPB-0001 - C MDL MDL 

### B) SR2-PPT-0001 - A SR2-PPT-0001 - B SR2-PPT-0001 - C *Total content as determined by digestion using method 3052. 

### 150 150 

### 140 140 

### 130 120 110 100

90 80 70Se spike recovery [%] 

### 130 120 110 100

90 80 70Se spike recovery [%]



### 60 

### 2 4 6 8 10 12 14 2 4 6 8 10 12 14 

### pH pH 

### 60

SR2-PPB-0001 - A SR2-PPT-0001 - A Characterization of Coal Combustion Residues

Figure E-7. Selenium Release (top) and Spike Recoveries (bottom) as a Function of pH for the Baseline Fly Ash and the Fly Ash with Enhanced Hg Control. 5 th and 95 th percentiles of selenium concentrations observed in typical combustion waste landfill leachate are shown for comparison.



### 138

## Selenium Release as a Function of LS Ratio Fly Ash with ACI Baseline Fly Ash 160 160 140 140 120 120

MCL

0 2 4 6 8 10 12 LS ratio [mL/g] MCL 40 40 20 20

0 0 0 2 4 6 8 10 12 LS ratio [mL/g] ML ML MDLSe [μg/L]

SR3-PPB-0001 - A SR3-PPB-0001 - B SR3-PPB-0001 - C MDL SR3-PPT-0001 - A SR3-PPT-0001 - B SR3-PPT-0001 - C


### 150 140 150 

### 140 100 100Se [μg/L]

80 80 60 60Se spike recovery [%]Se spike recovery [%] 

### 130 120 110 100

90 80 70 130 120 110 100

90 80 70 60 

### 60 0 2 4 6 8 10 12 

### 0 2 4 6 8 10 12 LS ratio [mL/g] 

### LS ratio [mL/g] SR3-PPB-0001 - A 

### SR3-PPT-0001 - A Characterization of Coal Combustion Residues

Figure E-8. Selenium Release (top) and Spike Recoveries (bottom) as a Function of LS Ratio for the Baseline Fly Ash and the Fly Ash with Enhanced Hg Control.



### 139

## Arsenic Solubility Fly Ash with ACI Baseline Fly Ash



### 5% 95% 5% 95%

0.001

0.01

0.1

1 10 100 1000 10000 100000As [μg/L]



### 5% 95% 5% 95%

0.001

0.01

0.1

1 10 100 1000 10000 100000As [μg/L]



### 2 4 6 8 10 12 14 

### 2 4 6 8 10 12 14 pH 

### pH SR2-PPT-0001-A SR2-PPT-0001-B SR2-PPT-0001-C Fit curve A) SR2-PPB-0001-A SR2-PPB-0001-B SR2-PPB-0001-C Fit curve 

### B)
Material log As ( μ g/L) pH range of R 2 Number of validity points PPB 0.0003 pH 5 -0.0117 pH 4 0.1674 pH 3 3-12.5 0.47 33 -1.1600 pH 2 3.8716 pH -4.2743 PPT 0.0006 pH 5 -0.0238 pH 4 0.3460 pH 3 3-13 0.84 33 -2.3840 pH 2 7.7036 pH -8.6786 Characterization of Coal Combustion Residues

Figure E-9. Regression Curves of Experimental Data of Arsenic Solubility as a Function of pH.



### 140

## Selenium Solubility Fly Ash with ACI Baseline Fly Ash 

### 100000

10000

1000

100

10

5% 5% 95%

0.001

0.01

0.1

1

14 

### 0.001 0.01

0.1

1 10 100 1000 10000 100000

14Se [μg/L] 

### 95%Se [μg/L] 

### 5%

95% 12 

### 5% 95% 12 2 4 6 8 10 

### 2 4 6 8 10 pH 

### pH SR2-PPB-0001-A SR2-PPB-0001-B SR2-PPB-0001-C A) Fit curve 

### B) SR2-PPT-0001-A SR2-PPT-0001-B SR2-PPT-0001-C Fit curve
Material log Se ( μ g/L) pH range of R 2 Number of validity points PPB 0.0006 pH 5 -0.0234 pH 4 0.3605 pH 3 3-12.5 0.54 33 -2.6711 pH 2 9.4536 pH -10.6432 PPT 0.0012 pH 5 -0.0440 pH 4 0.6379 pH 3 3-13 0.81 33 -4.3855 pH 2 14.2483 pH -15.6626 Characterization of Coal Combustion Residues

Figure E-10. Regression Curves of Experimental Data of Selenium Solubility as a Function of pH.



### 141

## 100-Year Selenium Release Estimates Selenium

100000

10000 PPB PPT % μ g/kg100-year Mt [μg/kg] Mt min Mt - 5% 

### 100 1000 Mt - 50% Mt - 95% 

### 10 Mean Mt Mt max 

### 1 0.1 5% 50% 95% 0 20 40 60 80 100 Percentile μ g/kg 3.0 4.4 733 4000 2254 4000 0.1 0.1 18.3 100.0

56.4 100.0 0.9 3.3 516 4000 1599 4000 % 0.0 0.1 12.9 100.0

40.0 100.0



### PPB PPT 

## 100-Year Arsenic Release Estimates

Arsenic 10000 PPB PPT % μ g/kg100-year Mt [μg/kg] 

### 1000 Mt min 

### 100 Mt - 5% Mt - 50% Mt - 95% 

### 10 Mean Mt Mt max 

### 1 0.1 5% 50% 95% 0 20 40 60 80 100 Percentile μ g/kg 0.1 0.2 36 473 107 1188 0.0006 0.0010 0.2 2.2 0.5 5.6 0.1 0.2 27 358

81 1049 % 0.0004 0.0007 0.1 1.5 0.3 4.4



### PPB PPT Characterization of Coal Combustion Residues

Figure E-11. 100-Y ear Arsenic Release Estimates as a Function of the Cum ulativ e Probability f or the Scenar io of Disposal in a Comb ustion W aste Landf ill.

Figure E-12. 100-Y ear Selenium Release Estimates as a Function of the Cumulativ e Probability f or the Scenar io of Disposal in a Comb ustion W aste Landf ill. 

### 142

## 100-Year Arsenic Release Estimates PPB - Arsenic 21300 μ g/kg

MCL LS 12.5 = 125 : g/kg MCL LS 95% = 1000 : g/kg 50 μ g/kg

0.2% 104 μ g/kg

0.5% 45 μ g/kg

0.2% 473 μ g/kg 2.2% 100%

1 10 100 1000 10000 100000100-year arsenic release [μg/kg]

Total content Combustion Default - pH 3 Default -pH Default ­ Waste Landfill ­ 12.5 Natural pH 95% confidence 11.2 A)

PPT - Arsenic 24000 μ g/kg

52 μ g/kg 0.2% 96 μ g/kg

0.4% 44 μ g/kg

0.2% 358 μ g/kg 1.5% 100%

1 10 100 1000 10000 100000100-year arsenic release [μg/kg]
MCL LS 95% = 1000 : g/kg MCL LS 12.5 = 125 : g/kg

Total content Combustion Default - pH 3 Default -pH Default ­ Waste Landfill ­ 12.5 Natural pH 95% confidence 11.9 B) Characterization of Coal Combustion Residues

Figure E-13. 100-Y ear Arsenic Release Estimates from A) Baseline Fly Ash and B) Fly Ash with A CI. Release estimates f or percolation controlled scenar io are compared to release estimate based on total content. The amount of the arsenic that would be released if the release concentration was at the MCL is also shown for comparison (LS default scenario = 12.5 L/kg and LS 95% = 100 L/kg). 

### 143

## 100-Year Selenium Release Estimates PPB - Selenium <4000 μ g/kg 4000 μ g/kg 4000 μ g/kg

MCL LS 12.5 = 625 : g/kg MCL LS 95% = 5000 : g/kg 1386 μ g/kg 34.7% 100% 565 μ g/kg

14.1% 100% 100%

1 10 100 1000 10000100-year selenium release [μg/kg]

Total content Combustion Default - pH 3 Default -pH Default ­ Waste Landfill ­ 12.5 Natural pH 95% confidence 11.2 A)

PPT - Selenium <4000 μ g/kg 4000 μ g/kg MCL LS 95% = 5000 : g/kg
MCL LS 12.5 = 625 : g/kg 316 μ g/kg 7.9% 740 μ g/kg

18.5% 448 μ g/kg 11.2% 100% 100%

1 10 100 1000 10000100-year selenium release [μg/kg]

Total content Combustion Default - pH 3 Default -pH Default ­ Waste Landfill ­ 12.5 Natural pH 95% confidence 11.9 B) Characterization of Coal Combustion Residues

Figure E-14. 100-year Selenium Release Estimates from A) Baseline Fly Ash and B) Fly Ash with ACI. Release estimates f or percolation controlled scenar io are compared to release estimate based on total content. The amount of the selenium that would be released if the release concentration was at the MCL is also shown for comparison (LS default scenario = 12.5 L/kg and LS 95% = 100 L/kg). 

### 144Characterization of Coal Combustion Residues 

## Comments Figure E-3:

• Fly ash from the test case had greater total Hg content

than the fly ash from the baseline case (by about 7.5 times).


### • Hg release is well below levels of potential concern

(but poor replication) for both baseline and test cases. 

### Figure E-5:

• The fly ash from the test case had similar total As

content than that from the baseline case.


### • As release was below the MCL for both the baseline

and the test cases for most pH conditions. 

### Figure E-7:

• T otal selenium content was below detection limits for Method 3052 for both fly ashes while significant sele
nium release (ranging from around 30 : g/L to around 1000 : g/L) as a function of pH was observed. This result is a consequence of the dilution effects of the digestion method and analytical requirements.


### • Selenium release from both the baseline and the test

cases was close to or exceeded the MCL (50 : g/L) for most pH conditions. 

### Figures E-1 1 and E-12:

• The fly ash from the test case would result in As re
lease slightly less than expected from the baseline case, with a 95% probability to be less than 358 and 473 : g/ kg, respectively
. 

### • The fly ash from the test case would result in Se re
lease less than expected from the baseline case, with a 95% probability to be less than 4000 : g/kg (total con
tent) in both cases and a 5% possibility that the total content will be released. 

### Figure E-13:

• For all scenarios examined, no significant difference in

arsenic release would be observed between the fly ash from the baseline case and the fly ash from the test case. 

### • For the 95% probability scenario, arsenic release from

both cases would be less than the amount that would be released if the release concentration was at the MCL and the LS ratio was the resultant LS ratio for the 95% case (i.e., about 100 L/kg). However, arsenic release would be greater than the amount that would be re
leased if the release concentration was at the MCL and the LS ratio was the LS ratio of the default sce
nario considered (i.e., 12.5 L/kg).


### • For the three default scenarios considered, arsenic re
lease would most likely be less than the amount that would be released if the release concentration was at the MCL. 

### Figure E-14:

• For scenarios at alkaline pH, lower Se release would

be expected for the test case compared to the baseline case. 

### • For the 95% probability scenario, selenium release from

both cases would be greater than the amount that would be released if the release concentration was at the MCL.


### • In conclusion, Se release will most likely be greater

than the MCL based on solubility and cumulative re
lease. W ithout controls appears worse than with con
trols.

145Characterization of Coal Combustion Residues



# Appendix F Salem Harbor Fly Ashes

146Characterization of Coal Combustion Residues



# List of Figures Figure Page F
- 1 pH T itration Curves for the Baseline Fly Ash and the Fly Ash with Enhanced Hg Control
....................................... ........ 1 4 8 F
-2 pH as a Function of LS Ratio for the Baseline Fly Ash and the Fly Ash with Enhanced Hg Control
.............................. ... 1 4 8 F
- 3 Mercury Release (top) and Spike Recoveries (bottom) as a Function of pH for the Baseline Fly Ash and the Fly Ash with Enhanced Hg Control
............................................................................................... ..................................... 1 4 9 F
-

4 Mercury Release (top) and Spike Recoveries (bottom) as a Function of LS Ratio for the Baseline Fly Ash and the Fly Ash with Enhanced Hg Control
........................................................................................... ................................... 1 5 0 F
- 5 Arsenic Release (top) and Spike Recoveries (bottom) as a Function of pH for the Baseline Fly Ash and the Fly Ash with Enhanced Hg Control
............................................................................................... ..................................... 1 5 1 F
- 6 Arsenic Release (top) and Spike Recoveries (bottom) as a Function of LS Ratio for the Baseline Fly Ash and the Fly Ash with Enhanced Hg Control
....................................................................................... ................................ 1 5 2 F
- 7 Selenium Release (top) and Spike Recoveries (bottom) as a Function of pH for the Baseline Fly Ash and the Fly Ash with Enhanced Hg Control
............................................................................................... ..................................... 1 5 3 F
- 8 Selenium Release (top) and Spike Recoveries (bottom) as a Function of LS Ratio for the Baseline Fly Ash and the Fly Ash with Enhanced Hg Control
....................................................................................... ................................ 1 54 F
- 9 Regression Curves of Experimental Data of Arsenic Solubility as a Function of pH.
........................................... .............. 1 5 5 F-10 Regression Curves of Experimental Data of Selenium Solubility as a Function of pH
.............................................. .......... 1 5 6 F-11 100-Y ear Arsenic Release Estimates as a Function of the Cumulative Probability for the Scenario of Disposal ina Combustion W aste Landfill
................................................................................................. ......................................... 1 5 7 F-12 100-Y ear Selenium Release Estimates as a Function of the Cumulative Probability for the Scenario of Disposal ina Combustion W aste Landfill
................................................................................................. ......................................... 1 5 7 F-13 100-Y ear Arsenic Release Estimates from A) Baseline Fly Ash and B) Fly Ash with ACI
............................................ ....... 1 5 8 F-14 1 0 0-year Selenium Release Estimates from A) Baseline Fly Ash and B) Fly Ash with ACI
............................................. .... 1 5 9



### 1476 

## pH Titration Curves Baseline Fly Ash Fly Ash with ACI 14 14 12 12 11.7 10.3 10 10 8

8pHpH 6 4 4 2

-1 -0.5 0 0.5 1 1.5 2 -2 -1.5 -1 -0.5 0 0.5 1 1.5 meq Acid/g dry meq Acid/g dry 2

SR2-SHB-0001 - A SR2-SHB-0001 - B SR2-SHB-0001 - C SR2-SHT-0001 - A SR2-SHT-0001 - B SR2-SHT-0001 - C



## pH as a Function of LS Ratio
14 Baseline Fly Ash 

### 14 Fly Ash with ACI


### 12 12 

### 10 10
6 

### 6 4 

### 4 2 

### 0 2 4 6 8 10 12 0 2 4 6 8 10 12 

### LS ratio [mL/g] LS ratio [mL/g] 

### 2

SR3-SHB-0001 - A SR3-SHB-0001 - B SR3-SHB-0001 - C SR3-SHT-0001 - A SR3-SHT-0001 - B SR3-SHT-0001 - CpHpH 

### 8 8 Characterization of Coal Combustion Residues

Figure F-1. pH Titr ation Cur v es f or the Baseline Fly Ash and the Fly Ash with Enhanced Hg Control.

Figure F-2. pH as a Function of LS Ratio for the Baseline Fly Ash and the Fly Ash with Enhanced Hg Control. 

### 148

## Mercury Release as a Function of pH Baseline Fly Ash Fly Ash with ACI Hg total content*: 650.6 ! 6.8 ng/g Hg total content*: 1529.6 ! 1.1 ng/g 

### 10 10 MCL MCL



### 1 1

5% 5% 

### 0.001 0.001 95% 5% 11.7 95% 5% 10.3 

### 2 4 6 8 10 12 14 2 4 6 8 10 12 14 pH pH ML ML MDL 

### SR2-SHB-0001 - A SR2-SHB-0001 - B SR2-SHB-0001 - C MDL 

### SR2-SHT-0001 - A SR2-SHT-0001 - B SR2-SHT-0001 - C *Total content as determined by digestion using method 3052. 

### 150 

### 140 150 140Hg [μg/L]Hg spike recovery [%]Hg [μg/L] 

### 0.1 0.1 95% 95% 0.032 0.011 

### 0.01 0.01



### 130 120 110 100

90 80 70 130 120 110 100

90 80 70Hg spike recovery [%]



### 60 60 

### 2 4 6 8 10 12 14 2 4 6 8 10 12 14 

### pH pH 

### SR2-SHB-0001 - A SR2-SHT-0001 - A Characterization of Coal Combustion Residues

Figure F-3. Mercury Release (top) and Spike Recoveries (bottom) as a Function of pH for the Baseline Fly Ash and the Fly Ash with Enhanced Hg Control. 5 th and 95 th percentiles of mercury concentrations observed in typical combustion waste landfill leachate are shown for comparison.



### 149

## Mercury Release as a Function of LS Ratio Baseline Fly Ash Fly Ash with ACI MCL 

### 0.1 MCL 

### 0.1 

### 0.08 0.08

0.02
0 2 4 6 8 10 12 LS ratio [mL/g] 

### 0.02
0 2 4 6 8 10 12 LS ratio [mL/g] 0 0 ML ML MDL MDL 

### SR3-SHB-0001 - A SR3-SHB-0001 - B SR3-SHB-0001 - C 

### SR3-SHT-0001 - A SR3-SHT-0001 - B SR3-SHT-0001 - C
150 150 

### 140 140Hg [μg/L]Hg spike recovery [%]Hg spike recovery [%]Hg [μg/L] 

### 0.06 0.04 

### 0.06 0.04

130 120 110 100

90 80 70 130 120 110 100

90 80 70 60 

### 0 2 4 6 8 10 12 0 2 4 6 8 10 12 

### LS ratio [mL/g] LS ratio [mL/g] 

### 60

SR3-SHB-0001 - A SR3-SHT-0001 - A Characterization of Coal Combustion Residues

Figure F-4. Mercury Release (top) and Spike Recoveries (bottom) as a Function of LS Ratio for the Baseline Fly Ash and the Fly Ash with Enhanced Hg Control.



### 150

## Arsenic Release as a Function of pH Baseline Fly Ash Fly Ash with ACI As total content*: 25.9 ! 0.04 : g/g As total content*: 26.0 ! 0.03 : g/g 

### 10000 10000 

### 1000 156 

### 1000 95% 95% 

### 100 100 19.30



### 0.01 

### 0.01 0.001 

### 0.001 5% 95% 5% 95% 11.7 10.3 

### 2 4 6 8 10 12 14 

### 2 4 6 8 10 12 14 pH 

### pH ML ML MDL 

### SR2-SHB-0001 - A SR2-SHB-0001 - B SR2-SHB-0001 - C MDL 

### SR2-SHT-0001 - A SR2-SHT-0001 - B SR2-SHT-0001 - C *Total content as determined by digestion using method 3052. 

### 150 

### 140 150 140 MCL 

### 10 MCL 

### 10As [μg/L]As spike recovery [%]As [μg/L] 5% 5% 

### 1 

### 1 0.1 

### 0.1



### 130 

### 130As spike recovery [%] 

### 120 

### 120 110 

### 110 100 

### 100 90



### 90 80 

### 80 70 

### 70 60 

### 60 2 4 6 8 10 12 14 2 4 6 8 10 12 14 

### pH pH


### SR2-SHB-0001 - A SR2-SHT-0001 - A Characterization of Coal Combustion Residues

Figure F-5. Arsenic Release (top) and Spike Recoveries (bottom) as a Function of pH for the Baseline Fly Ash and the Fly Ash with Enhanced Hg Control. 5 th and 95 th percentiles of arsenic concentrations observed in typical combustion waste landfill leachate are shown for comparison.



### 151

## Arsenic Release as a Function of LS Ratio Fly Ash with ACI Baseline Fly Ash 250 

### 40 50 200

50

0As spike recovery [%]As [μg/L] 

### 30 20 MCL 

### 10 MCL 

### 0 0 2 4 6 8 10 12 150 100As [μg/L]As spike recovery [%]

SR3-SHB-0001 - A SR3-SHT-0001 - A 0 2 4 6 8 10 12 LS ratio [mL/g] SR3-SHT-0001 - A SR3-SHT-0001 - B SR3-SHT-0001 - C ML 

### LS ratio [mL/g] MDL 

### SR3-SHB-0001 - A SR3-SHB-0001 - B SR3-SHB-0001 - C
150 140 130 120 110 100

90 80 70 ML MDL

150 140 130 120 110 100

90 80 70 60 60 0 2 4 6 8 10 12 0 2 4 6 8 10 12 LS ratio [mL/g] LS ratio [mL/g] Characterization of Coal Combustion Residues

Figure F-6. Arsenic Release (top) and Spike Recoveries (bottom) as a Function of LS Ratio for the Baseline Fly Ash and the Fly Ash with Enhanced Hg Control.



### 152

## Selenium Release as a Function of pH Baseline Fly Ash Fly Ash with ACI Se total content*: 41.9 ! 0.06 : g/g Se total content*: 44.0 ! 0.04 : g/g 

### 10000 

### 10000 1217 1497



### 1000 

### 1000 95% 95% 

### 100 

### 100 MCL MCL



### 0.01 

### 0.01 0.001 

### 0.001 5% 11.7 95% 5% 10.3 95% 

### 2 4 6 8 10 12 14 

### 2 4 6 8 10 12 14 ML 

### pH ML 

### pH MDL 

### SR2-SHB-0001 - A SR2-SHB-0001 - B SR2-SHB-0001 - C MDL 

### SR2-SHT-0001 - A SR2-SHT-0001 - B SR2-SHT-0001 - C *Total content as determined by digestion using method 3052. 

### 150 150 140 140 5% 

### 1 10 

### 10Se [μg/L]Se spike recovery [%]Se [μg/L] 5% 

### 1 0.1 

### 0.1



### 130 120 110 100

90 80 70 130 120 110 100

90 80 70Se spike recovery [%]



### 60 60 2 4 6 8 10 12 14 2 4 6 8 10 12 14 pH pH SR2-SHB-0001 - A SR2-SHT-0001 - A Characterization of Coal Combustion Residues

Figure F-7. Selenium Release (top) and Spike Recoveries (bottom) as a Function of pH for the Baseline Fly Ash and the Fly Ash with Enhanced Hg Control. 5 th and 95 th percentiles of selenium concentrations observed in typical combustion waste landfill leachate are shown for comparison.



### 153

## Selenium Release as a Function of LS Ratio Fly Ash with ACI Baseline Fly Ash 

### 5000 5000 4000 

### 4000

1000
0 2 4 6 8 10 12 LS ratio [mL/g] 

### 1000 MCL MCL 0 

### 0 ML ML MDL 

### 0 2 4 6 8 10 12 LS ratio [mL/g] SR3-SHB-0001 - A SR3-SHB-0001 - B SR3-SHB-0001 - C MDL 

### SR3-SHT-0001 - A SR3-SHT-0001 - B SR3-SHT-0001 - C
150 150 140 140Se [μg/L]Se [μg/L]Se spike recovery [%] 3000 2000 

### 3000 2000Se spike recovery [%] 130 120 110 100

90 80 70 130 120 110 100

90 80 70 60 60 0 2 4 6 8 10 12 0 2 4 6 8 10 12 LS ratio [mL/g] LS ratio [mL/g]
SR3-SHB-0001 - A SR3-SHT-0001 - A Characterization of Coal Combustion Residues

Figure F-8. Selenium Release (top) and Spike Recoveries (bottom) as a Function of LS Ratio for the Baseline Fly Ash and the Fly Ash with Enhanced Hg Control.



### 154

## Arsenic Solubility Fly Ash with ACI Baseline Fly Ash 

### 100000 100000 

### 10000

10000 

### 1000

1000



### 5% 95% 0.1 0.1 

### 0.01 0.01 5% 95% 

### 95% 5% 95% 

### 100 100As [μg/L]As [μg/L] 

### 10

10 5% 

### 1

1

0.001 

### 0.001 2 4 6 8 10 12 14 

### 2 4 6 8 10 12 14 pH 

### pH SR2-SHB-0001-A 

### SR2-SHT-0001-A SR2-SHB-0001-B 

### SR2-SHT-0001-B SR2-SHB-0001-C 

### SR2-SHT-0001-C A) Fit curve 

### B) Fit curve
Material log As ( μ g/L) pH range of R 2 Number of validity points SHB 0.0000 pH 5 0.0011 pH 4 -0.0428 pH 3 3-12.5 0.96 33 0.4859 pH 2 -2.2393 pH 5.6031 SHT 0.0003 pH 5 -0.0106 pH 4 0.1194 pH 3 3-13 0.92 33 -0.5142 pH 2 0.4220 pH 3.3432 Characterization of Coal Combustion Residues

Figure F-9. Regression Curves of Experimental Data of Arsenic Solubility as a Function of pH.



### 155

## Selenium Solubility Fly Ash with ACI Baseline Fly Ash 

### 100000 100000



### 10000 10000



### 1000 1000 

### 95% 95% 5% 

### 100 100Se [μg/L]Se [μg/L]



### 10 10 

### 5% 1 1 

### 0.1 0.1 

### 0.01 0.01 

### 0.001 0.001 

### 5% 95% 5% 95% 

### 2 4 6 8 10 12 14 2 4 6 8 10 12 14 

### pH pH


### A) B) 

### SR2-SHB-0001-A SR2-SHB-0001-B SR2-SHB-0001-C Fit curve SR2-SHT-0001-A SR2-SHT-0001-B SR2-SHT-0001-C Fit curve
Material log Se ( μ g/L) pH range of R 2 Number of validity points SHB -0.0001 pH 5 0.0061 pH 4 -0.1107 pH 3 3-12.5 0.93 33 0.9490 pH 2 -3.5922 pH 6.8613 SHT 0.0001 pH 5 -0.0020 pH 4 0.0141 pH 3 3-13 0.98 33 0.0589 pH 2 -0.6849 pH 3.3216 Characterization of Coal Combustion Residues

Figure F10. Regression Curves of Experimental Data of Selenium Solubility as a Function of pH.



### 156

## 100-Year Arsenic Release Estimates Arsenic 100000 SHB SHT



### 10000 μ g/kg % μ g/kg %100-year Mt [μg/kg] Mt min



### 1000 Mt - 5% Mt - 50% 

### 100 Mt - 95% Mean Mt 

### 10 Mt max



### 1 0.1 0 5% 20 40 50% 60 80 95% 100 Percentile SHB SHT 0.8 3.6 546 7922 1749 18969 0.003 0.014

2.1 30.6

6.8 73.2 2.7 6.1 968 13374

3013 26000 0.01 0.02

3.7 51.4 11.6 100.0



## 100-Year Selenium Release Estimates

Selenium 100000

10000 SHB SHT % μ g/kg100-year Mt[μg/kg] Mt min Mt - 5% 

### 100 1000 Mt - 50% Mt - 95% 

### 10 Mean Mt Mt max 

### 1 0.1 5% 50% 95% 0 20 40 60 80 100 Percentile SHB SHT μ g/kg 6.6 34.5 5011 41900 17623 41900 0.02 0.08 12.0 100.0

42.1 100.0 4.7 24.3 3650 44000 14240 44000 % 0.01 0.06

8.3 100.0

32.4 100.0 Characterization of Coal Combustion Residues

Figure F-11. 100-Y ear Arsenic Release Estimates as a Function of the Cum ulativ e Probability f or the Scenar io of Disposal in a Comb ustion W aste Landf ill.

Figure F-12. 100-Y ear Selenium Release Estimates as a Function of the Cum ulativ e Probability f or the Scenario of Disposal in a Comb ustion W aste Landf ill. 

### 157

## 100-Year Arsenic Release Estimates SHB - Arsenic 25900 μ g/kg

241 μ g/kg 0.9% 360 μ g/kg 1.4% 1967 μ g/kg 7.6% 7922 μ g/kg 30.6% 100%

1 10 100 1000 10000 100000100-year arsenic release [μg/kg]
MCL LS 95% = 1000 : g/kg MCL LS 12.5 = 125 : g/kg

Total content Combustion Default - pH 3 Default -pH Default ­ Waste Landfill - 12.5 Natural pH 95% confidence 11.7 A)

SHT - Arsenic 26000 μ g/kg

1950 μ g/kg 7.5% 2590 μ g/kg 10% 3326 μ g/kg 12.8% 13374 μ g/kg 51.4% 100%

1 10 100 1000 10000 100000100-year arsenic release [μg/kg]
MCL LS 95% = 1000 : g/kg MCL LS 12.5 = 125 : g/kg

Total content Combustion Default - pH 3 Default -pH Default ­ Waste Landfill ­ 12.5 Natural pH 95% confidence 10.3 B) Characterization of Coal Combustion Residues

Figure F-13. 100-Y ear Arsenic Release Estimates from A) Baseline Fly Ash and B) Fly Ash with A CI. Release estimates f or percolation controlled scenar io are compared to release estimate based on total content. The amount of the arsenic that would be released if the release concentration was at the MCL is also shown for comparison (LS default scenario = 12.5 L/kg and LS 95% = 100 L/kg). 

### 158

## 100-Year Selenium Release Estimates SHB - Selenium 41900 μ g/kg 41900 μ g/kg MCL LS 95% = 5000 : g/kg MCL LS 12.5 = 625 : g/kg 15208 μ g/kg 36.3% 20296 μ g/kg 48.4% 1572 μ g/kg 3.8% 100% 100%

1 10 100 1000 10000 100000100-year selenium release [μg/kg]

A)
SHT - Selenium 44000 μ g/kg 44000 μ g/kg 24978 μ g/kg 100000 100% 100% 56.8% Total content Combustion Default - pH 3 Default -pH Default ­ Waste Landfill - 12.5 Natural pH 95% confidence 11.7

18708 μ g/kg 42.5% 1337 μ g/kg 10000 3% MCL LS 95% = 5000 : g/kg100-year selenium release [μg/kg] MCL LS 12.5 = 625 : g/kg

B) 1000
100

10

1 Total content Combustion Default - pH 3 Default -pH Default ­ Waste Landfill - 12.5 Natural pH 95% confidence 10.3 Characterization of Coal Combustion Residues

Figure F-14. 100-year Selenium Release Estimates from A) Baseline Fly Ash and B) Fly Ash with ACI. Release estimates f or percolation controlled scenar io are compared to release estimate based on total content. The amount of the selenium that would be released if the release concentration was at the MCL is also shown for comparison (LS default scenario = 12.5 L/kg and LS 95% = 100 L/kg). 

### 159Characterization of Coal Combustion Residues 

## Comments Figure F-3:

• The fly ash from the test case had similar total Hg

content to that from the baseline case.


### • Hg release is greater in baseline than test case, but

both were below MCL. 

### Figure F-5:

• The fly ash from the test case had similar total As

content than that from the baseline case.


### • The laboratory measurements fit within the 5–95% con
fidence intervals of the field observations.


### • Arsenic release is less in baseline than test case, but

both are about 10 times greater than the MCL. Ar
senic release at pH higher than 9 is much greater for the test case than the baseline case. 

### Figure F-6:

• Initial landfill leachate As concentrations will likely be

about 20–30 : g/L for the baseline case but at least 100 : g/L for the test case. 

### Figure F–7:

• The fly ash from the test case had similar total Se con
tent to that from the baseline case.


### • Se release is similar in baseline and test cases, but sig
nificantly above MCL for both cases. The observed concentrations are greater than reported in the EP A database but consistent with the EPRI database. 

### Figure F-8:

• Initial landfill leachate Se concentrations are expected

to be around 200 : g/L for the baseline case and in
creasing with increasing LS ratio, but the initial con
centrations for the test case are expected to be around 3000 : g/L and decreasing with increasing LS ratio. 

### Figures F-1 1 and F-12:

• The fly ash from the test case would result in As re
lease greater than expected from the baseline case, with a 95% probability to be less than 13,375 and 7,925 : g/kg, respectively
. 

### • The fly ash from the test case would result in Se re
lease less than expected from the baseline case. At the 95 th

### percentile the total content of Se will be re
leased (41,900 and 44,000 : g/kg, respectively , for the baseline case and the test case).


### • 10–100% of the Se can be anticipated to be leached

from the fly ash for both cases under the projected landfill conditions. 

### Figure-13:

• Greater As release would be expected for the test case

compared to the baseline case, for all scenarios exam
ined.


### • For all scenarios examined, Arsenic release from the

test case fly ash would be greater than the amount that would be released if the release concentration was at the MCL. 

### Figure F-14:

• At the 95 th

### percentile, Se release estimate exceeds total

content for both the baseline and the test cases. This is not physically possible. However , this result indicates that there is 5% possibility that 100% of the total Se content would be released.


### • For all scenarios examined, Se release would most likely

be greater than the amount that would be released if the release concentration was at the MCL.

160Characterization of Coal Combustion Residues



# Appendix G Facility C Fly Ashes

161Characterization of Coal Combustion Residues



# List of Figures Figure Page G

- 1 pH T itration Curves for the Baseline Fly Ash and the Fly Ash with Enhanced Hg Control
....................................... ........ 1 63 G

- 2 pH as a Function of LS Ratio for the Baseline Fly Ash and the Fly Ash with Enhanced Hg Control
.............................. ... 1 63 G

- 3 Mercury Release (top) and Spike Recoveries (bottom) as a Function of pH for the Baseline Fly Ash and the Fly Ash with Enhanced Hg Control
............................................................................................... ..................................... 1 6 4 G

- 4 Mercury Release (top) and Spike Recoveries (bottom) as a Function of LS Ratio for the Baseline Fly Ash and the Fly Ash with Enhanced Hg Control
........................................................................................... ................................... 1 6 5 G

- 5 Arsenic Release (top) and Spike Recoveries (bottom) as a Function of pH for the Baseline Fly Ash and the Fly Ash with Enhanced Hg Control
............................................................................................... ..................................... 1 66 G

- 6 Arsenic Release (top) and Spike Recoveries (bottom) as a Function of LS Ratio for the Baseline Fly Ash and the Fly Ash with Enhanced Hg Control
....................................................................................... ................................ 1 6 7 G

- 7 Selenium Release (top) and Spike Recoveries (bottom) as a Function of pH for the Baseline Fly Ash and the Fly Ash with Enhanced Hg Control
............................................................................................... ..................................... 1 6 8 G

- 8 Selenium Release (top) and Spike Recoveries (bottom) as a Function of LS Ratio for the Baseline Fly Ash and the Fly Ash with Enhanced Hg Control
....................................................................................... ................................ 1 69 G

- 9 Regression Curves of Experimental Data of Arsenic Solubility as a Function of pH.
........................................... .............. 1 70 G-10 Regression Curves of Experimental Data of Selenium Solubility as a Function of pH
.............................................. .......... 1 7 1 G-11 100-Y ear Arsenic Release Estimates as a Function of the Cumulative Probability for the Scenario of Disposal ina Combustion W aste Landfill
................................................................................................. ......................................... 1 7 2 G-12 100-Y ear Selenium Release Estimates as a Function of the Cumulative Probability for the Scenario of Disposal ina Combustion W aste Landfill
................................................................................................. ......................................... 1 7 2 G-13 100-Y ear Arsenic Release Estimates from A) Baseline Fly Ash and B) Fly Ash with ACI
............................................ ....... 1 7 3 G-14 1 0 0 -year Selenium Release Estimates from A) Baseline Fly Ash and B) Fly Ash with ACI
.............................................. ... 1 7 4



### 1626 

## pH Titration Curves Baseline Fly Ash Fly Ash with ACI 14 14 12 12 11.3 10 10 8.1 8 8pHpH 6 4 4 2

-0.5 0 0.5 1 1.5 2 -0.5 0 0.5 1 1.5 2 meq Acid/g dry meq Acid/g dry 2

SR2-GAT - A SR2-GAT - B SR2-GAB - A SR2-GAB - B SR2-GAB - C



## pH as a Function of LS Ratio
14 Baseline Fly Ash 14 Fly Ash with ACI
12 12 10 10

6 6 4 4 2 2 0 2 4 6 8 10 12 0 2 4 6 8 10 12 LS ratio [mL/g] LS ratio [mL/g] SR3-GAB - A SR3-GAB - B SR3-GAB - C SR3-GAT - A SR3-GAT - BpHpH 8 8 Characterization of Coal Combustion Residues

Figure G-1. pH Titr ation Cur v es f o r the Baseline Fly Ash and the Fly Ash with Enhanced Hg Control.

Figure G-2. pH as a Function of LS Ratio for the Baseline Fly Ash and the Fly Ash with Enhanced Hg Control. 

### 163

## Mercury Release as a Function of pH Baseline Fly Ash Fly Ash with ACI Hg total content*: 15.8 ! 0.9 ng/g Hg total content*: 1150.7 ! 14.4 ng/g 10 10 MCL MCL

1 1

0.001 0.001 5% 11.3 95% 5% 8.1 95% 2 4 6 8 10 12 14 2 4 6 8 10 12 14 ML pH ML pH MDL SR2-GAB - A SR2-GAB - B SR2-GAB - C MDL S R2-GAT - A S R2-GAT - B *Total content as determined by digestion using method 3052. 

### 150 150 

### 140 140 0.01 5% 5%Hg [μg/L]Hg spike recovery [%]Hg [μg/L] 0.1 0.1 95% 95% 0.016 0.014 0.01Hg spike recovery [%] 

### 130 120 110 100

90 80 70 130 120 110 100

90 80 70 

### 60 60 

### 2 4 6 8 10 12 14 2 4 6 8 10 12 14 

### pH pH


### SR2-GAB - A SR2-GAT - A Characterization of Coal Combustion Residues

Figure G-3. Mercury Release (top) and Spike Recoveries (bottom) as a Function of pH for the Baseline Fly Ash and the Fly Ash with Enhanced Hg Control. 5 th and 95 th percentiles of mercury concentrations observed in typical combustion waste landfill leachate are shown for comparison.



### 164

## Mercury Release as a Function of LS Ratio Baseline Fly Ash Fly Ash with ACI 0.1 0.1 0.08 0.08

0.02 0.02 0 0 0 2 4 6 8 10 12 ML ML LS ratio [mL/g] MDL 0 2 4 6 8 10 12 LS ratio [mL/g] SR3-GAB - A SR3-GAB - B SR3-GAB - C MDL SR3-GAT - A SR3-GAT - B

150 150 140 140Hg spike recovery [%]Hg [μg/L] 0.06Hg spike recovery [%]Hg [μg/L] 0.06 0.04 0.04

130 120 110 100

90 80 70 130 120 110 100

90 80 70 60 60 0 2 4 6 8 10 12 0 2 4 6 8 10 12 LS ratio [mL/g] LS ratio [mL/g] SR3-GAB - A SR3-GAT - A Characterization of Coal Combustion Residues

Figure G-4. Mercury Release (top) and Spike Recoveries (bottom) as a Function of LS Ratio for the Baseline Fly Ash and the Fly Ash with Enhanced Hg Control.



### 165

## Arsenic Release as a Function of pH Baseline Fly Ash Fly Ash with ACI

*Total content as determined by digestion using method 3052. MDL ML 11.3 237.37 MCL

0.001

0.01

0.1

1 10 100 1000 10000

2 4 6 8 10 12 14 pHAs [μg/L]

SR2-GAB - A SR2-GAB - B SR2-GAB - C 5% 95% 95% As total content*: 93.6 ! 5.5 : g/g

MDL ML 8.1 119.67

0.001

0.01 100 1000 10000

2 4 6 8 10 12 14 pH SR2-GAT - A SR2-GAT - B 5% 95% 95% As total content*: 506.3 ! 28.7 : g/g



### 140 150 140 150 MCL 10As spike recovery [%]As [μg/L] 5% 5% 1 0.1



### 60 60 2 4 6 8 10 12 14 2 4 6 8 10 12 14 pH pHAs spike recovery [%] 

### 130 130 120 120 110 110 100 100

90 90 80 80 70 70

SR2-GAB - A SR2-GAT - A Characterization of Coal Combustion Residues

Figure G-5. Arsenic Release (top) and Spike Recoveries (bottom) as a Function of pH for the Baseline Fly Ash and the Fly Ash with Enhanced Hg Control. 5 th and 95 th percentiles of arsenic concentrations observed in typical combustion waste landfill leachate are shown for comparison.



### 166

## Arsenic Release as a Function of LS Ratio Fly Ash with ACI Baseline Fly Ash 400 400 350 350 300 300

50 0 2 4 6 8 10 12 LS ratio [mL/g] 50 MCL MCL 0 0
ML ML 0 2 4 6 8 10 12 LS ratio [mL/g] MDL SR3-GAB - A SR3-GAB - B SR3-GAB - C MDL SR3-GAT - A SR3-GAT - B

150 150 140 140 250 250 200As spike recovery [%]As [μg/L]As [μg/L]As spike recov ery [%] 200 150 100 150 100

0 2 4 6 8 10 12 LS ratio [mL/g] 130 130 120 110 100 120 110 100

90 90 80 80 70 70 60 60 0 2 4 6 8 10 12 LS ratio [mL/g] SR3-GAB - A SR3-GA T - A Characterization of Coal Combustion Residues

Figure G-6. Arsenic Release (top) and Spike Recoveries (bottom) as a Function of LS Ratio for the Baseline Fly Ash and the Fly Ash with Enhanced Hg Control.



### 167

## Selenium Release as a Function of pH Baseline Fly Ash Fly Ash with ACI Se total content*: <4.0 : g/g Se total content*: 206.3 ! 0.9 : g/g 10000 10000 3288.09 2851.88 1000

1000 95% 95% 100 100 MCL MCL

0.01 0.01 0.001 5% 11.3 95% 5% 8.1 0.001 95% 2 4 6 8 10 12 14 2 4 6 8 10 12 14 ML pH ML pH MDL SR 2-GAB - A SR 2-GAB - B SR 2-GAB - C MDL SR2-GAT - A SR2-GAT - B *Total content as determined by digestion using method 3052. 150 150 140 140 5% 1 10 10Se [μ g/L]Se spike recovery [%]Se [μ g/L] 5% 1 0.1 0.1

130 120 110 100

90 80 70 130 120 110 100

90 80 70Se spike recovery [%]

60 60 2 4 6 8 10 12 14 2 4 6 8 10 12 14 pH pH
SR2-GAB - A SR2-GAT - A Characterization of Coal Combustion Residues

Figure G-7. Selenium Release (top) and Spike Recoveries (bottom) as a Function of pH for the Baseline Fly Ash and the Fly Ash with Enhanced Hg Control. 5 th and 95 th percentiles of selenium concentrations observed in typical combustion waste landfill leachate are shown for comparison.



### 168

## Selenium Release as a Function of LS Ratio Fly Ash with ACI Baseline Fly Ash 8000 8000 7000 7000 6000 6000 5000 5000Se [μ g/L]Se spike recovery [%]Se [μg/L] 4000 4000 3000 3000 2000 2000 1000 1000 MCL 0 MC L 0 0 2 4 6 8 10 12 0 2 4 6 8 10 12 ML LS rat io [mL/g] ML LS ratio [ mL/g] MDL MDL SR3-GAB - A S R3-GAB - B SR3-GAB - C SR3-GAT - A SR 3-GAT - B

150 150 140 140Se spike recovery [%] 130 120 110 100

90 80 70 130 120 110 100

90 80 70 60 60 0 2 4 6 8 10 12 0 2 4 6 8 10 12 LS ratio [m L/g] LS ratio [mL/g]
SR3-GAB - A SR3-GA T - A Characterization of Coal Combustion Residues

Figure G-8. Selenium Release (top) and Spike Recoveries (bottom) as a Function of LS Ratio for the Baseline Fly Ash and the Fly Ash with Enhanced Hg Control.



### 169A) 

## Arsenic Solubility Fly Ash with ACI Baseline Fly AshAs [μg/L] 100000 10000

1000

100

10

1 0.1 0.01 0.001 5% 95% 5% 95%

2 4 6 8 10 12 14 5% 95% 5% 95%

0.001

0.01

0.1

1 10 100 1000 10000 100000

2 4 6 8 10 12 14As [μg/L]

pH
B) pH SR2-GAT - A SR2-GAT - B Fit curve
Material log As (μg/L) pH range of validity R 2 Number of points SR2-GAB - A SR2-GAB - B SR2-GAB - C Fit curve

GAB 0.0012 pH 5 -0.0416 pH 4 0.5236 pH 3 3-12.5 0.78 33 -3.0400 pH 2 8.0912 pH -5.3943 GAT -0.0008 pH 5 0.0304 pH 4 -0.4500 pH 3 3-12.5 0.75 22 3.1407 pH 2 -10.1848 pH 14.1412 Characterization of Coal Combustion Residues

Figure G-9. Regression Curves of Experimental Data of Arsenic Solubility as a Function of pH.



### 170

## Selenium Solubility Fly Ash with ACI Baseline Fly Ash 100000

10000

1000 100000 10000

1000 95% 100 10 5% 1 0.1 0.01 0.001 5% 95% 12 14 2 4Se [μg/L] 95% 5% 100

10Se [μg/L] 1 0. 1 0. 01 0. 001 pH pH SR2-GAB - A SR2-GAB - B SR2-GAB - C Fit curve B) A) 5%
SR2-GAT - A SR2-GAT - B Fit curve 95% 12 6 8 10 14 2 4 6 8 10

Material log Se (μg/L) pH range of R 2 Number of validity points GAB -0.0003 pH 5 0.0092 pH 4 -0.1259 pH 3 3-12.5 0.98 33 0.8035 pH 2 -2.2208 pH 4.5849 GAT -0.00002 pH 5 0.0021 pH 4 -0.0530 pH 3 3-12.5 0.96 22 0.5431 pH 2 -2.2226 pH 5.8084 Characterization of Coal Combustion Residues

Figure G-10. Regression Curves of Experimental Data of Selenium Solubility as a Function of pH.



### 171Arsenic 

## 100-Year Arsenic Release Estimates 100000

10000

1000 Mt min Mt - 5% 100 Mt - 50% Mt - 95% 10 Mean Mt Mt max 1 95% 0.1 GAB GAT μg/kg 5.8 27.5 4086 59706 13789 93600 % μg/kg % 0.0062 4.1 0.0008 0.0294 7.0 0.0014 4.4 1142 0.2 63.8 15411 3.0 14.7 3485 0.7 100.0 48499 9.6100-year Mt [μg/kg]

5% 50% 0 20 40 60 80 100 Percentile GAB GAT



## 100-Year Selenium Release Estimates

Selenium

1000000

100000

10000 Mt min



### 95% GAB GAT μg/kg % μg/kg %100-year Mt [μg /kg] 24.8 0.6 31.1 0.02 Mt - 5% Mt - 50% 

### 1000

100 Mt - 95% Mean Mt 

### 10 Mt max



### 1 69.6 4000 4000 4000 4000 1.7 100.0 100.0 100.0 100.0 142.5 21033 206300

78816 206300 0.1 10.2 100.0

38.2 100.0 

### 0.1 5% 50% 0 20 40 60 80 100 P ercentile GAB GAT Characterization of Coal Combustion Residues

Figure G-11. 100-Y ear Arsenic Release Estimates as a Function of the Cum ulativ e Probability f or the Scenar io of Disposal in a Comb ustion W aste Landf ill.

Figure G-12. 100-Y ear Selenium Release Estimates as a Function of the Cum ulativ e Probability f or the Scenar io of Disposal in a Comb ustion W aste Landf ill. 

### 172

## 100-Year Arsenic Release Estimates GAB - Arsenic 93600 μg/kg 93600 μg/kg 100% 59706 μg/kg 100% 2967 μg/kg 3.2% 4855 μg/kg 5.2% 63.8%

1 10 100 1000 10000 100000100-y ear arsenic releas e [μ g/kg]
MCL LS 95% = 1000 : g/kg MCL LS 12.5 = 125 : g/kg

Total content Combustion Default - pH 3 Default - pH Default ­ Waste Landfill ­ 12.5 Natural pH 95% confidence 11.3 A)

GAT - Arsenic 506300 μg/kg

1496 μg/kg 0.3% 2413 μg/kg 0.5% 1178 μg/kg 0.2% 15411 μg/kg 3.0% 100%

1 10 100 1000 10000 100000 1000000100-year arsenic release [μg/kg]

MCL LS 95% = 1000 : g/kg MCL LS 12.5 = 125 : g/kg

B) Total content Combustion Default - pH 3 Default - pH Default ­ Waste Landfill ­ 12.5 Natural pH 95% confidence 8.1 Characterization of Coal Combustion Residues

Figure G-13. 100-Y ear Arsenic Release Estimates from A) Baseline Fly Ash and B) Fly Ash with A CI. Release estimates f or percolation controlled scenar io are compared to release estimate based on total content. The amount of the arsenic that would be released if the release concentration was at the MCL is also shown for comparison (LS default scenario = 12.5 L/kg and LS 95% = 100 L/kg). 

### 173

## 100-Year Selenium Release Estimates GAB - Selenium <4000 μg/ kg 4000 μg/kg 100% 100% 3447.2 μg/kg 86. 2% 100% 100%

1 10 100 1000 10000

Total content Com bustion Waste Landfill ­ 95% confidence Default - pH 3 Default - pH 12.5 Default - Natural pH100-year selenium release [ μg/ kg]

11.3 MCL LS 95% = 5000 : g/kg
MCL LS 12.5 = 625 : g/kg 4000 μg/ kg 4000 μg/kg

A)

GAT - Selenium
41101.1 μg/kg 19. 9% 206300 μg/kg 100% 7191.3 μg/ kg 3.5% 206300 μg/ kg 100% 206300 μg/kg 100%

1 10 100 1000 10000 100000 1000000100-year selenium release [μ g/kg]
MCL LS 95% = 5000 : g/kg MCL LS 12.5 = 625 : g/kg

Total content Combustion Default - pH 3 Default - pH Default ­ Waste Landfill - 12.5 Natural pH 8.1 B) 95% confidence Characterization of Coal Combustion Residues

Figure G-14. 100-year Selenium Release Estimates from A) Baseline Fly Ash and B) Fly Ash with ACI. Release estimates f or percolation controlled scenar io are compared to release estimate based on total content. The amount of the selenium that would be released if the release concentration was at the MCL is also shown for comparison (LS default scenario = 12.5 L/kg and LS 95% = 100 L/kg). 

### 174Characterization of Coal Combustion Residues 

## Comments Figure G-1:

• All extract Hg concentrations are well below levels of

potential concern. 

### Figure G-5:

• Arsenics extract concentrations for the baseline case

peak between pH 7 and 9, with maximum concentrations significantly greater than the range reported forfield landfill leachates in the EPA database but consistent with the range of concentrations for field landfill leachates reported in the EPRI database.


### • Arsenic extract concentrations for the test case indicate somewhat lower concentrations than for the baseline case over the range of pH examined, even though the test case as around 5 times as much total As as the baseline case. These results also suggestdifferent chemistry controlling the aqueous-solid equilibrium for the two cases. 

### Figure G-7:

• Se extract concentrations as a function of pH exhibit

similar behavior for the baseline and test cases, even though the test case has greater than 50 times the amount of total As than the baseline case. 

### Figure G-8:

• Initial leachate concentrations for Se are likely to be

ca. 1000–4000 : g/L (at LS=2), which is much greater than reported in the EPA database but consistent with values reported in the EPRI database for landfill leachates. 

### Figures G-11and G-12:

• A much greater percentage and quantity of As can be

anticipated to be released from the baseline case than for the test case under the scenarios examined. 

### Figure G13:

• Arsenic release from the base case warrants further

examination. 

### Figure G-14:

• Se release from the test case warrants further examination.

175Characterization of Coal Combustion Residues



# Appendix H St. Clair Fly Ashes

176Characterization of Coal Combustion Residues



# List of Figures Figure Page H-1 pH Titration Curves for the Baseline Fly Ash and the Fly Ash with Enhanced Hg Control ....................................... ........ 178 H-2 pH as a Function of LS Ratio for the Baseline Fly Ash and the Fly Ash with Enhanced Hg Control .............................. ... 178 H-3 Mercury Release (top) and Spike Recoveries (bottom) as a Function of pH for the Baseline Fly Ash and the Fly Ash with Enhanced Hg Control ............................................................................................... ..................................... 179 H-4 Mercury Release (top) and Spike Recoveries (bottom) as a Function of LS Ratio for the Baseline Fly Ash and the Fly Ash with Enhanced Hg Control ........................................................................................... ................................... 180 H-5 Arsenic Release (top) and Spike Recoveries (bottom) as a Function of pH for the Baseline Fly Ash and the Fly Ash with Enhanced Hg Control ............................................................................................... ..................................... 181 H-6 Arsenic Release (top) and Spike Recoveries (bottom) as a Function of LS Ratio for the Baseline Fly Ash and the Fly Ash with Enhanced Hg Control ....................................................................................... ................................ 182 H-7 Selenium Release (top) and Spike Recoveries (bottom) as a Function of pH for the Baseline Fly Ash and the Fly Ash with Enhanced Hg Control ............................................................................................... ..................................... 183 H-8 Selenium Release (top) and Spike Recoveries (bottom) as a Function of LS Ratio for the Baseline Fly Ash and the Fly Ash with Enhanced Hg Control ....................................................................................... ................................ 184 H-9 Regression Curves of Experimental Data of Arsenic Solubility as a Function of pH. ........................................... .............. 185 H-10 Regression Curves of Experimental Data of Selenium Solubility as a Function of pH
.............................................. .......... 186 H-11 100-Year Arsenic Release Estimates as a Function of the Cumulative Probability for the Scenario of Disposal in a Combustion Waste Landfill ................................................................................................. ......................................... 187 H-12 100-Year Selenium Release Estimates as a Function of the Cumulative Probability for the Scenario of Disposal in a Combustion Waste Landfill ................................................................................................. ......................................... 187 H-13 100-Year Arsenic Release Estimates from A) Baseline Fly Ash and B) Fly Ash with ACI ............................................ ....... 188 H-14 10 0-year Selenium Release Estimates from A) Baseline Fly Ash and B) Fly Ash with ACI ................................................. 189



### 177

## pH as a Function of LS Ratio
14 Baseline Fly Ash 14 Fly Ash with B-PAC
12 12 10 10

6 6 4 4 2 2 0 2 4 6 8 10 12 0 2 4 6 8 10 12 LS ratio [mL/g] LS ratio [mL/g]pH 8pH 8

SR3-JAB - A SR3-JAB - B SR3-JAT - A SR3-JAT - B Characterization of Coal Combustion Residues 

## pH Titration Curves Baseline Fly Ash Fly Ash with B-PAC 14 14 12.1 12.2 12 12 10 10

8 8pHpH 6 6 4 4 2 2

-1 0 1 2 3 4 5 6 7 -1 0 1 2 3 4 5 6 7 meq Acid/g dry meq Acid/g dry
SR2-JAB - A SR2-JAB - B SR2-JAT - A SR2-JAT - B
Figure H-1. pH Titr ation Cur v es f or the Baseline Fly Ash and the Fly Ash with Enhanced Hg Control.

Figure H-2. pH as a Function of LS Ratio for the Baseline Fly Ash and the Fly Ash with Enhanced Hg Control. 

### 178

## Mercury Release as a Function of pH Baseline Fly Ash Fly Ash with B-PAC Hg total content*: 110.9 ! 5.8 ng/g Hg total content*: 1163.0 ! 8.9 ng/g 10 10 MCL MCL

1 1]]LL//g 0.1g 0.1μμ[[HgHg] % [yrvecoe rekispg H 95% 95% 0.030 0.01 0.01 5% 5% 0.001 0.001 5% 95% 12.1 5% 95% 12.2 2 4 6 8 10 12 14 2 4 6 8 10 12 14 pH pH ML ML MDL SR2-JAB - A MDL SR2-JAB - B SR2-JAT - A SR2-JAT - B 0.020

*Total content as determined by digestion using method 3052. 

### 150 

### 150 140 

### 140] % 

### 130 

### 130y [r 

### 120 

### 120ve 

### 110 

### 110coer 

### 100 

### 100eki 

### 90 

### 90sp 

### 80 

### 80gH 

### 70 

### 70

60 

### 60 2 4 6 8 10 12 14 

### 2 4 6 8 10 12 14 pH 

### pH
SR2-JAB - A 

### SR2-JAT - A

Figure H-3. Mercury Release (top) and Spike Recoveries (bottom) as a Function of pH for the Baseline Fly Ash and the Fly Ash with Enhanced Hg Control. 5 th and 95 th percentiles of mercury concentrations observed in typical combustion waste landfill leachate are shown for comparison. Characterization of Coal Combustion Residues



### 179

## Mercury Release as a Function of LS Ratio Baseline Fly Ash Fly Ash with B-PAC 0.1 0.1 0.08 0.08]]/L 0.06/L 0.06g [μ[μggH 0.04gH 0.04 0.02 0 0 2 4 6 8 10 ML LS ratio [mL/g] MDL]]%%[[yyrrveveoocceerreekkiispspggHH 12 0.02 0 0 2 4 6 8 10 12 ML LS ratio [mL/g] MDL SR3-JAB - A SR3-JAB - B

150 140 SR3-JAT - A SR3-JAT - B

150 140

60 60 0 2 4 6 8 10 12 0 2 4 6 8 10 12 LS ratio [mL/g] LS ratio [mL/g] 130 130 120 120 110 110 100 100

90 90 80 80 70 70

SR3-JAB - A SR3-JAT - A
Figure H-4. Mercury Release (top) and Spike Recoveries (bottom) as a Function of LS Ratio for the Baseline Fly Ash and the Fly Ash with Enhanced Hg Control. Characterization of Coal Combustion Residues



### 180

## Arsenic Release as a Function of pH Baseline Fly Ash Fly Ash with B-PAC 10000 As total content*: 43.4 ! 2.6 : g/g As total content*: 40.8 ! 1.1 : g/g 10000 1000 1000 95% 95% 100 100 MCL MCL 10 10As [μg/L]As [μg/L]As spike recovery [%] 5% 5% 1 1 0.54 0.92 0.1 0.1 0.01 0.01 0.001 0.001 5% 95% 12.1 5% 95% 12.2 2 4 6 8 10 12 14 2 4 6 8 10 12 14 ML pH ML pH MDL MDL SR2-JAB - A SR2-JAB - B SR2-JAT - A SR2-JAT - B *Total content as determined by digestion using method 3052. 

### 150 150 

### 140 140



### 60 60 

### 2 4 6 8 10 12 14 2 4 6 8 10 12 14 

### pH pHAs spike recovery [%] 

### 130 130 

### 120 120 

### 110 110 

### 100 100



### 90 90 80 70 

### 80 70

SR2-JAB - A SR2-JAT - A Characterization of Coal Combustion Residues

Figure H-5. Arsenic Release (top) and Spike Recoveries (bottom) as a Function of pH for the Baseline Fly Ash and the Fly Ash with Enhanced Hg Control. 5 th and 95 th percentiles of arsenic concentrations observed in typical combustion waste landfill leachate are shown for comparison.



### 181

## Arsenic Release as a Function of LS Ratio Baseline Fly Ash Fly Ash with B-PAC 350 350 300 300 250 250

MCL 200 150 100

50 MCL 0 0 2 4 6 8 10 LS ratio [mL/g] ML MDL 12

SR3-JAB - A SR3-JAB - B

150 140 200 150 100

50

0 0 2 4 6 8 10 12 LS ratio [mL/g] ML MDL SR3-JAT - A SR3-JAT - B

150 140As spike recovery [%]As [μg/L]As spike recovery [%]As [μg/L]

SR3-JAB - A SR3-JAT - A 130 120 110 100

90 80 70 130 120 110 100

90 80 70 60 60 0 2 4 6 8 10 12 0 2 4 6 8 10 12 LS ratio [mL/g] LS ratio [mL/g] Characterization of Coal Combustion Residues

Figure H-6. Arsenic Release (top) and Spike Recoveries (bottom) as a Function of LS Ratio for the Baseline Fly Ash and the Fly Ash with Enhanced Hg Control.



### 182

## Selenium Release as a Function of pH Baseline Fly Ash Fly Ash with B-PAC Se total content*: 10.7 ! 0.1 : g/g Se total content*: 12.6 ! 0.9 : g/g 10000 10000 1000 1000 95% 95%

100 100 MCL 50.80 MCL 58.85 10 5%

12.2 2 4 6 8 10 12 14 5% 95%Se [μg/L]Se spike recovery [%]Se [μg/L] 10 1 0.1 0.01 0.001 5% 1 0.1 0.01 0.001 5% 95% 12.1 2 4 6 8 10 12 14 ML pH ML pH MDL SR2-JAB - A SR2-JAB - B MDL SR2-JAT - A SR2-JAT - B *Total content as determined by digestion using method 3052. 150 150 140 140Se spike recovery [%] 130 120 110 100

90 80 70 130 120 110 100

90 80 70 60 60 2 4 6 8 10 12 14 2 4 6 8 10 12 14 pH pH SR2-JA B - A SR2-JAT - A Characterization of Coal Combustion Residues

Figure H-7. Selenium Release (top) and Spike Recoveries (bottom) as a Function of pH for the Baseline Fly Ash and the Fly Ash with Enhanced Hg Control. 5 th and 95 th percentiles of selenium concentrations observed in typical combustion waste landfill leachate are shown for comparison.



### 183

## Selenium Release as a Function of LS Ratio Baseline Fly Ash Fly Ash with B-PACSe [μg/L]Se spike recovery [%] 

### 800 800 

### 700 700 

### 600 600 

### 500 400 300 200 100 MCL



### 0 0 2 4 6 8 10 ML 

### LS ratio [mL/g] MDL 

### 12

SR3-JAB - A SR3-JAB - B

150 140Se [μg/L]Se spike recovery [%]

SR3-JAB - A 

### SR3-JAT - A 500 400 300 200 100 MCL 0 0 2 4 6 8 10 12 MDL ML LS ratio [mL/g]
SR3-JAT - A SR3-JAT - B



### 150 140 130 120 110 100

90 80 70 

### 130 120 110 100

90 80 70 60 

### 60 0 2 4 6 8 10 12 

### 0 2 4 6 8 10 12 LS ratio [mL/g] 

### LS ratio [mL/g] Characterization of Coal Combustion Residues

Figure H-8. Selenium Release (top) and Spike Recoveries (bottom) as a Function of LS Ratio for the Baseline Fly Ash and the Fly Ash with Enhanced Hg Control.



### 184

## Arsenic Solubility Baseline Fly Ash Fly Ash with B-PAC



### 5% 95% 5% 95%

0.001

0.01

0.1

1 10 100 1000 10000 100000As [μg/L]



### 5% 95% 5% 95%

0.001

0.01

0.1

1 10 100 1000 10000 100000As [μg/L]



### 2 4 6 8 10 12 14 2 4 6 8 10 12 14 

### pH pH SR2-JAT - A SR2-JAT - B Fit curve 

### SR2-JAB - A SR2-JAB - B Fit curve B) 

### A)

Material log As (μg/L) pH range of R 2 Number of validity points JAB 0.0010 pH 5 -0.0324 pH 4 0.4137 pH 3 3-12.5 0.62 22 -2.4547 pH 2 6.7105 pH -6.6563 JAT 0.0025 pH 5 -0.0973 pH 4 1.4698 pH 3 4-12.5 0.81 22 -10.6792 pH 2 37.2419 pH -50.3673 Characterization of Coal Combustion Residues

Figure H-9. Regression Curves of Experimental Data of Arsenic Solubility as a Function of pH.



### 185

## Selenium Solubility Baseline Fly Ash Fly Ash with B-PAC 

### 100000 100000

10000 10000 1000 1000

5% 95% 0.1

0.1 0.01 0.01 5% 1 95% 95% 100 100Se [μg/L]Se [μg/L] 

### 10 10 5% 1

0.001 0.001 95% 5% 2 4 6 8 10 12 14 2 4 6 8 10 12 14 pH pH SR2-JAT - A SR2-JAT - B Fit curve SR2-JAB - A SR2-JAB - B Fit curve B) A)
Material log Se (μg/L) pH range of R 2 Number of validity points JAB 0.0002 pH 5 -0.0070 pH 4 0.0761 pH 3 3-12.5 0.75 22 -0.2648 pH 2 -0.3724 pH 4.6460 JAT 0.0005 pH 5 -0.0201 pH 4 0.2890 pH 3 3-12.5 0.61 22 -1.9155 pH 2 5.6877 pH -3.7128 Characterization of Coal Combustion Residues

Figure H-10. Regression Curves of Experimental Data of Selenium Solubility as a Function of pH.



### 186

### 1000 

## 100-Year Arsenic Release Estimates

A rsenic 10000 JAB JAT100-year Mt [μg/kg] μg/kg % μg/kg % Mt min 0.01 0.00003 0.01 0.00001 

### 100 Mt - 5% Mt - 50% Mt - 95% 

### 10 Mean Mt Mt max 

### 1 0.1 95% 5% 50% 0 20 40 60 80 100 Percentile 0.05 8 110

25 836 0.0001 0.02

0.3 0.1 1.9 0.01 2 29

7 346 0.00003 0.01

0.1 0.02

0.8



### JAB JAT



## 100-Year Selenium Release Estimates

Selenium

100000100-year Mt [μg/kg] 

### 10000 Mt min Mt - 5% 

### 100 1000 Mt - 50% Mt - 95% 

### 10 Mean Mt Mt max 

### 1 0.1 5% 50% 95% 0 20 40 60 80 100 Percentile JAB JAT μg/kg 1.8 4.5 748 10028

2270 10700 % 0.02 0.04

7.0 93.7 21.2 100.0 μg/kg 1.9 4.3 710 9602 2172 12600 % 0.01 0.03

5.6 76.2 17.2 100.0



### JAB JAT Characterization of Coal Combustion Residues

Figure H-1 1. 100-Y ear Arsenic Release Estimates as a Function of the Cum ulativ e Probability f or the Scenar io of Disposal in a Comb ustion W aste Landf ill.

Figure H-12. 100-Y ear Selenium Release Estimates as a Function of the Cum ulativ e Probability f o r the Scenar io of Disposal in a Comb ustion W aste Landf ill. 

### 187

## 100-Year Arsenic Release Estimates
JAB - Arsenic 43400 μg/kg 100000 100%100-year arsenic release [μg/kg] 10000
1000 110 μg/kg 0.3% 100

10

1 Total content Combustion Waste Landfill ­ 95% confidence A) 18 μg/kg 0.04% 110 μg/kg 0.3% 12 μg/kg 0.03% MCL LS 95% = 1000 : g/kg MCL LS 12.5 = 125 : g/kg

Default - pH 3 Default - pH 12.5 Default ­ Natural pH 12.1100-year arsenic release [μg/kg] JAT - Arsenic 100000 40800 μg/kg 100% 10000

1000

0.1 μg/kg 0.0001% MCL LS 95% = 1000 : g/kg 29 μg/kg 47 μg/kg MCL LS 12.5 = 125 : g/kg 100 0.1% 0.1% 7 μg/kg 0.02% 10

1 0.1 0.01 Total content Combustion Default - pH 3 Default - pH Default ­ Waste Landfill - 12.5 Natural pH B) 95% confidence 12.2 Characterization of Coal Combustion Residues

Figure H-13. 100-Y ear Arsenic Release Estimates from A) Baseline Fly Ash and B) Fly Ash with B-P A C
. Release estimates f or percolation controlled scenar io are compared to release estimate based on total content. The amount of the arsenic that would be released if the release concentration was at the MCL is also shown for comparison (LS default scenario = 12.5 L/kg and LS 95% = 100 L/kg). 

### 188

## 100-Year Selenium Release Estimates JAB - Selenium 100000 MCL LS 95% = 5000 : g/kg 10700 μg/kg 100% 10028 μg/kg 93.7%

1 10 100 1000 10000100-year selenium release [μg/kg] 6070 μg/kg 56.7% MCL LS 12.5 = 625 : g/kg 727 μg/kg 635 μg/kg 6.8% 5.9%

Total content Combustion Default - pH 3 Default - pH Default ­ Waste Landfill - 12.5 Natural pH A) 95% confidence 12.1

JAT - Selenium 100000 MCL LS 95% = 5000 : g/kg 12600 μg/kg 9602 μg/kg100-year selenium release [μg/kg] 100% 10000 25.7% MCL LS 12.5 = 625 : g/kg 778 μg/kg 736 μg/kg 6.2% 5.8% 1000

100

10

1 Total content Combustion Default - pH 3 Default - pH Default ­ Waste Landfill - 12.5 Natural pH 95% confidence 12.2 76.2% 3243 μg/kg

B) Characterization of Coal Combustion Residues

Figure H-14. 100-y ear Selenium Release Estimates from A) Baseline Fly Ash and B) Fly Ash with B-P A C
. Release estimates f or percolation controlled scenar io are compared to release estimate based on total content. The amount of the selenium that would be released if the release concentration was at the MCL is also shown for comparison (LS default scenario = 12.5 L/kg and LS 95% = 100 L/kg). 

### 189Characterization of Coal Combustion Residues 

## Comments Figure H-3:

• All extract concentrations for Hg are well below levels of potential concern.


### • Scatter in the extract concentrations for the cased with

enhanced Hg control most likely results from the material heterogeneity associated with addition of particulate activated carbon. 

### Figure H-5:

• All extract concentrations for As are well below levels

of potential concern. 

### Figure H-6:

• Initial As leachate concentrations from landfills are expected to be substantially greater (i.e., equal to 50 : g/ L at LS=2) than indicated by SR002 (LS=10) because of other ionic species at higher concentrations presentat low LS ratio typical of landfill scenarios. These anticipated concentrations are consistent with landfill leachate concentrations reported in the EPRI database. 

### Figure H-7:

• Extract concentrations of selenium are greater than

the MCL but within the range reported in the EPA and EPRI databases. 

### Figure H-8:

• Initial Se leachate concentrations from landfills are expected to be substantially greater (i.e., more than 200– 300 :g/L at LS=2) than indicated by SR002 (LS=10)because of other ionic species at higher concentrations present at low LS ratio typical of landfill scenarios. These anticipated concentrations are consis
tent with landfill leachate concentrations reported in the EPRI database. 

### Figures H-11 and H-12:

• A much greater percentage and quantity of As can be

anticipated to be released from the baseline case than for the test case under the scenarios examined. 

### Figure H-13:

• For the three default scenarios considered and the 95%

probability scenario, arsenic release would most likely be less than the amount that would be released if the release concentration was at the MCL. 

### Figure H-14:

• For the 95% probability scenario, selenium release from

baseline and test cases would be greater than theamount that would be released if the release concentration was at the MCL.


### • For the default scenario corresponding to disposal in a

monofill (leachate pH controlled by the material being disposed) and the default scenario corresponding to the “extreme” pH of 12.5, no significant difference in selenium release between the baseline and test cases would be expected.


### • For the default scenario corresponding to the “extreme”

pH of 3, selenium release is expected to be greater for the baseline case than the test case. In both cases, selenium release would be at or greater than the amount that would be released if the release concentration was at the MCL.


### • Se release from the baseline and test cases warrants

further examination.

190Characterization of Coal Combustion Residues



# Appendix I Facility L Fly Ashes

191Characterization of Coal Combustion Residues



# List of Figures Figure Page I-1 pH Titration Curves for the Baseline Fly Ash and the Fly Ash with Enhanced Hg Control ....................................... ........ 193 I-2 pH as a Function of LS Ratio for the Baseline Fly Ash and the Fly Ash with Enhanced Hg Control .............................. ... 193 I-3 Mercury Release (top) and Spike Recoveries (bottom) as a Function of pH for the Baseline Fly Ash and the Fly Ash with Enhanced Hg Control ............................................................................................... ..................................... 194 I-4 Mercury Release (top) and Spike Recoveries (bottom) as a Function of LS Ratio for the Baseline Fly Ash and the Fly Ash with Enhanced Hg Control ........................................................................................... ................................... 195 I-5 Arsenic Release (top) and Spike Recoveries (bottom) as a Function of pH for the Baseline Fly Ash and the Fly Ash with Enhanced Hg Control ............................................................................................... ..................................... 196 I-6 Arsenic Release (top) and Spike Recoveries (bottom) as a Function of LS Ratio for the Baseline Fly Ash and the Fly Ash with Enhanced Hg Control ....................................................................................... ................................ 197 I-7 Selenium Release (top) and Spike Recoveries (bottom) as a Function of pH for the Baseline Fly Ash and the Fly Ash with Enhanced Hg Control ............................................................................................... ..................................... 198 I-8 Selenium Release (top) and Spike Recoveries (bottom) as a Function of LS Ratio for the Baseline Fly Ash and the Fly Ash with Enhanced Hg Control ....................................................................................... ................................ 199 I-9 Regression Curves of Experimental Data of Arsenic Solubility as a Function of pH. ........................................... .............. 200 I-10 Regression Curves of Experimental Data of Selenium Solubility as a Function of pH
.............................................. .......... 201 I-11 100-Year Arsenic Release Estimates as a Function of the Cumulative Probability for the Scenario of Disposal in a Combustion Waste Landfill ................................................................................................. ......................................... 202 I-12 100-Year Selenium Release Estimates as a Function of the Cumulative Probability for the Scenario of Disposal in a Combustion Waste Landfill ................................................................................................. ......................................... 202 I-13 100-Year Arsenic Release Estimates from A) Baseline Fly Ash and B) Fly Ash with ACI ............................................ ....... 203 I-14 100 -year Selenium Release Estimates from A) Baseline Fly Ash and B) Fly Ash with ACI .............................................. ... 204



### 192

## pH Titration Curves Baseline Fly Ash Fly Ash with Enhanced Hg Control 14 14 12 12 10 10

8 6 5.8

4 2 8 6 5.0 4 2pHpH

-0.5 -0.25 0 0.25 0.5 -0.5 -0.25 0 0.25 0.5 meq Acid/g dry meq Acid/g dry
SR2-LAB - A SR2-LAB - B SR2-LAT - A SR2-LAT - B



## pH as a Function of LS Ratio Baseline Fly Ash Fly Ash with Enhanced Hg Control 

### 14 14 12 12 10 10pH 

### 8

6 4 2pH 

### 8 6 4 2 0 2 4 6 8 10 12 0 2 4 6 8 10 12 LS ratio [mL/g] LS ratio [mL/g]
SR3-LAB - A SR3-LAB - B SR3-LAT - A SR3-LAT - B Characterization of Coal Combustion Residues

Figure I-1. pH Titr ation Cur v es f or the Baseline Fly Ash and the Fly Ash with Enhanced Hg Control.

Figure I-2. pH as a Function of LS Ratio for the Baseline Fly Ash and the Fly Ash with Enhanced Hg Control. 

### 193

## Mercury Release as a Function of pH Baseline Fly Ash Fly Ash with Enhanced Hg Control 

### 10 Hg total content*: 13 ! 0.2 ng/g 

### 10 Hg total content*: 37.7 ! 1.3 ng/g MCL



### 1 MCL 

### 1Hg [μg/L]Hg [μg/L]Hg spike recovery [%] 

### 0.1 95% 0.010 

### 0.1 95% 

### 0.01 

### 0.01 0.009 5% 5% 

### 0.001 

### 0.001 5.8 5% 95% 5.0 5% 95% 

### 2 4 6 8 10 12 14 2 4 6 8 10 12 14 ML 

### pH pH MDL ML MDL 

### SR2-LAB - A SR2-LAB - B SR2-LAT - A SR2-LAT - B *Total content as determined by digestion using method 3052. 

### 150 150 

### 140 140Hg spike recovery [%] 

### 130 120 110 100

90 

### 130 120 110 100

90 80 80 70 

### 70 60 

### 60 2 4 6 8 10 12 14 

### 2 4 6 8 10 12 14 pH 

### pH
SR2-LAB - A 

### SR2-LAT - A Characterization of Coal Combustion Residues

Figure I-3. Mercury Release (top) and Spike Recoveries (bottom) as a Function of pH for the Baseline Fly Ash and the Fly Ash with Enhanced Hg Control. 5 th and 95 th percentiles of mercury concentrations observed in typical combustion waste landfill leachate are shown for comparison.



### 194

## Mercury Release as a Function of LS Ratio Baseline Fly Ash 

### 0.1 Fly Ash with Enhanced Hg Control 

### 0.1 0.08 

### 0.08Hg spike recovery [%]Hg [μg/L] 

### 0.06 0.04 0.02 0 0 2 4 6 8 10 ML 

### LS ratio [mL/g] MDL 

### 12

SR3-LAB - A SR3-LAB - B

150 140 130 120 110 100

90 80 70Hg [μg/L]Hg spike recovery [%] 

### 0.06 0.04 0.02 0 0 2 4 6 8 10 12 ML 

### LS ratio [mL/g] MDL 

### SR3-LAT - A SR3-LAT - B

150 140 130 120 110 100

90 80 70 60 60 0 2 4 6 8 10 12 0 2 4 6 8 10 12 LS ratio [mL/g] LS ratio [mL/g] SR3-LAB - A SR3-LAT - A Characterization of Coal Combustion Residues

Figure I-4. Mercury Release (top) and Spike Recoveries (bottom) as a Function of LS Ratio for the Baseline Fly Ash and the Fly Ash with Enhanced Hg Control.



### 195

## Arsenic Release as a Function of pH Fly Ash with Enhanced Hg Control

MDL ML 5.0 24.96



### 0.001

0.01 100 1000 10000

2 4 6 8 10 12 14 pH SR2-LAT - A SR2-LAT - B 5% 95% 95% As total content*: 18.7 ! 0.7 : g/g Baseline Fly Ash

MDL ML 5.8 25.95



### 0.001

0.01 100 1000 10000

2 4 6 8 10 12 14 pH SR2-LAB - A SR2-LAB - B 5% 95% 95% As total content*: 20 ! 1.1 : g/g

MCL MCL 

### 10 10As [μg/L]As [μg/L]As spike recovery [%] 5% 5% 

### 1 1 0.1 

### 0.1

*Total content as determined by digestion using method 3052. 

### 150 150 140 140As spike recovery [%] 

### 130 120 110 100

90 80 70 130 120 110 100

90 80 70 60 60 2 4 6 8 10 12 14 2 4 6 8 10 12 14 pH pH
SR2-LAB - A SR2-LAT - A Characterization of Coal Combustion Residues

Figure I-5. Arsenic Release (top) and Spike Recoveries (bottom) as a Function of pH for the Baseline Fly Ash and the Fly Ash with Enhanced Hg Control. 5 th and 95 th percentiles of arsenic concentrations observed in typical combustion waste landfill leachate are shown for comparison.



### 196

## Arsenic Release as a Function of LS Ratio Baseline Fly Ash Fly Ash with Enhanced Hg Control

MCL 

### 0 10 20 30 40 50As [μg/L]

MCL 

### 0 10 20 30 40 50As [μg/L]



### 0 2 4 6 8 10 12 0 2 4 6 8 10 12 ML 

### LS ratio [mL/g] ML 

### LS ratio [mL/g] MDL MDL 

### SR3-LAB - A SR3-LAB - B SR3-LAT - A SR3-LAT - B

150 150 140 140As spike recovery [%] 

### 130 120 110 100

90 80 70As spike recovery [%] 

### 130 120 110 100

90 80 70 60 60 0 2 4 6 8 10 12 0 2 4 6 8 10 12 LS ratio [mL/g] LS ratio [mL/g] SR3-LAB - A SR3-LAT - A Characterization of Coal Combustion Residues

Figure I-6. Arsenic Release (top) and Spike Recoveries (bottom) as a Function of LS Ratio for the Baseline Fly Ash and the Fly Ash with Enhanced Hg Control.



### 197

## Selenium Release as a Function of pH Baseline Fly Ash Fly Ash with Enhanced Hg Control

MDL ML 5.8 MCL



### 0.001

0.01 100 1000 10000

2 4 6 8 10 12 14 pH SR2-LAB - A SR2-LAB - B 5% 95% 95% Se total content*: 4.1 ! 0.1 : g/g

MDL ML 5.0 MCL



### 0.001

0.01 100 1000 10000

2 4 6 8 10 12 14 pH SR2-LAT - A SR2-LAT - B 5% 95% 95% Se total content*: 4.3 ! 0.2 : g/g



### 10 8.29 

### 10Se spike recovery [%]Se [μg/L]Se [μg/L] 5.85 5% 5% 

### 1 1 

### 0.1 0.1

*Total content as determined by digestion using method 3052. 

### 150 

### 150 140 

### 140

60 

### 60 2 4 6 8 10 12 14 

### 2 4 6 8 10 12 14 pH 

### pHSe spike recovery [%] 

### 130 

### 130 120 

### 120 110 

### 110 100 

### 100

90 

### 90 80 

### 80 70 

### 70

SR2-LAB - A 

### SR2-LAT - A Characterization of Coal Combustion Residues

Figure I-7. Selenium Release (top) and Spike Recoveries (bottom) as a Function of pH for the Baseline Fly Ash and the Fly Ash with Enhanced Hg Control. 5 th and 95 th percentiles of selenium concentrations observed in typical combustion waste landfill leachate are shown for comparison.



### 198

## Selenium Release as a Function of LS Ratio Baseline Fly Ash Fly Ash with Enhanced Hg Control MCL 

### 50 MCL 

### 50 40 40Se [μg/L]Se spike recovery [%] 

### 30 20 10

0 0 2 4 6 8 10 ML 

### LS ratio [mL/g] MDL 

### 12

SR3-LAB - A SR3-LAB - B

150 140 130 120 110 100

90 80 70Se [μg/L]Se spike recovery [%] 

### 30 20 10

MDL ML 

### 0 0 2 4 6 8 LS ratio [mL/g] 10 12

SR3-LAT - A SR3-LAT - B

150 140 130 120 110 100

90 80 70 60 

### 60 0 2 4 6 8 10 12 

### 0 2 4 6 8 10 12 LS ratio [mL/g] 

### LS ratio [mL/g] SR3-LAB - A 

### SR3-LAT - A Characterization of Coal Combustion Residues

Figure I-8. Selenium Release (top) and Spike Recoveries (bottom) as a Function of LS Ratio for the Baseline Fly Ash and the Fly Ash with Enhanced Hg Control.



### 199

## Arsenic Solubility Baseline Fly Ash Fly Ash with Enhanced Hg Control 

### 100000 100000



### 10000 10000



### 1000 1000



### 0.1
5% 95% 0.1 

### 0.01 0.01 5% 95% 

### 95% 95% 5% 

### 100 100As [μg/L]As [μg/L]



### 10 10 

### 5% 1 1



### 0.001 0.001 

### 2 4 6 8 10 12 14 2 4 6 8 10 12 14 

### pH pH SR2-LAT - A SR2-LAT - B Fit curve 

### A) SR2-LAB - A SR2-LAB - B Fit curve B)

Material log As (μg/L) pH range of R 2 Number of validity points LAB 0.0004 pH 5 -0.0120 pH 4 0.0966 pH 3 3-12.5 0.92 22 0.0151 pH 2 -2.4406 pH 7.2162 LAT 0.0000 pH 5 0.0040 pH 4 -0.1157 pH 3 3-12.5 0.92 22 1.2681 pH 2 -5.5708 pH 9.6784 Characterization of Coal Combustion Residues

Figure I-9. Regression Curves of Experimental Data of Arsenic Solubility as a Function of pH.



### 200

### A) 

## Selenium Solubility Baseline Fly Ash Fly Ash with Enhanced Hg ControlSe [μg/L] 

### 100000 10000

1000

100

10

95% 0.001

0.01

0.1

1 10 100 1000 10000 100000

12 14Se [μg/L]



### 5% 95% 5% 95% 95% 

### 1 0.1 0.01 0.001 5%



### 2 4 6 8 10 12 14 5% 2 4 6 8 10 

### pH pH 

### SR2-LAB - A SR2-LAB - B Fit curve B) SR2-LAT - A SR2-LAT - B Fit curve

Material log Se (μg/L) pH range of R 2 Number of validity points LAB 0.0007 pH 5 -0.0239 pH 4 0.3133 pH 3 3-12.5 0.94 22 -1.8284 pH 2 4.4667 pH -1.9621 LAT 0.0007 pH 5 -0.0230 pH 4 0.2978 pH 3 3-12.5 0.81 22 -1.7038 pH 2 4.0275 pH -1.4335 Characterization of Coal Combustion Residues

Figure I-10. Regression Curves of Experimental Data of Selenium Solubility as a Function of pH.



### 201

### A rsenic 

## 100-Year Arsenic Release Estimates 100000

10000 LAB LAT % μg/kg100-year Mt [μg/kg] Mt min Mt - 5% 

### 100 1000 Mt - 50% Mt - 95% 

### 10 Mean Mt Mt max 

### 1 0.1 5% 50% 95% 0 20 40 60 80 100 Percentile μg/kg 0.83 13.36 2049 20000 10541 20000 0.00413 0.0668

10.25 100.0

52.7 100.0 1.50 17.38 2471 18700 10090 18700 % 0.00800 0.09296 13.22 100.0 53.96 100.0



### LAB LAT



## 100-Year Selenium Release Estimates

Selenium

100000 μg/kg



### 10000 Mt min Mt - 5% 

### 100 1000 Mt - 50% Mt - 95% 

### 10 Mean Mt Mt max 

### 1 0.1 5% 50% 95% 0 20 40 60 80 100 Percentile100-year Mt [μg/kg] LAB LAT μg/kg 0.3 1.0 143 2113

484 4100 % 0.01 0.02

3.5 51.5 11.8 100.0 0.3 1.0 141 2041

466 4300 % 0.007

0.02

3.3 47.5 10.8 100.0



### LAB LAT Characterization of Coal Combustion Residues

Figure I-1 1 . 100-Y ear Arsenic Release Estimates as a Function of the Cum ulativ e Probability f or the Scenar io of Disposal in a Comb ustion W aste Landf ill.

Figure I-12. 100-Y ear Selenium Release Estimates as a Function of the Cum ulativ e Probability f or the Scenar io of Disposal in a Comb ustion W aste Landf ill. 

### 202

## 100-Year Arsenic Release Estimates
LAB - Arsenic 100000 20000 μg/kg 20000 μg/kg 20000 μg/kg 100% 100% 100%100-year arsenic release [μg/kg] 10000 729.3 μg/kg 3.7% 324.3 μg/kg 1000 MCL LS 95% = 1000 : g/kg 1.6% MCL LS 12.5 = 125 : g/kg 100

10

1 Total content Combustion Default - pH 3 Default - pH Default ­ Waste Landfill - 12.5 Natural pH 95% confidence 5.8 A)100-year arsenic release [μg/kg]

B) LAT - Arsenic 100000 18700 μg/kg 18700 μg/kg 18700 μg/kg 100% 100% 100% 10000 312 μg/kg 468 μg/kg 1000 MCL LS 95% = 1000 : g/kg 1.7% 2.5% MCL LS 12.5 = 125 : g/kg 100

10

1 Total content Combustion Default - pH 3 Default - pH Default ­ Waste Landfill - 12.5 Natural pH 95% confidence 5.0 Characterization of Coal Combustion Residues

Figure I-13. 100-Y ear Arsenic Release Estimates from A) Baseline Fly Ash and B) Fly Ash with Enhanced Hg Control. Release estimates f or percolation controlled scenar io are compared to release estimate based on total content. The amount of the arsenic that would be released if the release concentration was at the MCL is also shown for comparison (LS default scenario = 12.5 L/kg and LS 95% = 100 L/kg). 

### 203

## 100-Year Selenium Release Estimates LAB - Selenium 4100 μg/kg 10000 100% 2112.6 μg/kg MCL LS 95% = 5000 : g/kg100-year selenium release [μg/kg] 51.5% 587.9 μg/kg 989.7 μg/kg 14.3% 24.1% 1000 MCL LS 12.5 = 625 : g/kg 103.6 μg/kg 2.5% 100

10

1 Total content Combustion Default - pH 3 Default - pH Default - Natural Waste Landfill - 12.5 pH 95% confidence 5.8 A)100-year selenium release [μg/kg]

B) LAT - Selenium 4300 μg/kg 100% 10000 2040.9 μg/kg 947.6 μg/kg 47.5% 22% 559.4 μg/kg 1000 13.0%

100

10

1 Total content Combustion Default - pH 3 Default - pH Waste Landfill - 12.5 95% confidence 73.1 μg/kg 1.7% MCL LS 95% = 5000 : g/kg
MCL LS 12.5 = 625 : g/kg

Default - Natural pH 5.0 Characterization of Coal Combustion Residues

Figure I-14. 100-year Selenium Release Estimates from A) Baseline Fly Ash and B) Fly Ash with Enhanced Hg Control. Release estimates f or percolation controlled scenar io are compared to release estimate based on total content. The amount of the selenium that would be released if the release concentration was at the MCL is also shown for comparison (LS default scenario = 12.5 L/kg and LS 95% = 100 L/kg). 

### 204Characterization of Coal Combustion Residues 

## Comments Figure I-3:

• Fly ash from the test case had greater total Hg content

than the fly ash from the baseline case (by about 3 times).


### • Hg release is low (but poor replication) for both baseline

and test cases. 

### Figure I-5:

• The fly ash from the test case had lower total As content than that from the baseline case (by about 4.5 times).


### • Arsenic release was close to or exceeded the MCL

(10 : g/L) for both the baseline and the test cases for all pH conditions. 

### Figure I-7:

• Fly ash from the test case had greater total Se content

than the fly ash from the baseline case (by about 4.5 times).


### • Selenium release from both the baseline and the test

cases was close to the MCL (50 : g/L) for most pH conditions. 

### Figures I-11 and I-12:

• The fly ash from the test case would result in similar

As release than expected from the baseline case, with a 95% probability to be less than 18700 and 20000 : g/ kg, respectively. 

### • The fly ash from the test case would result in similar Se release than expected from the baseline case, with a 95% probability to be less than 21 15 and 2045 : g/kg, respectively
. 

### Figure I-13:

• For the 95% probability scenario, arsenic release from

both cases would exceed the amount that would be released if the release concentration was at the MCL.


### • For two of the three default scenarios considered (i.e.,

pH 3 and natural pH), arsenic release would most likely be less than the amount that would be released if the release concentration was at the MCL. However, for the default scenario at pH 12.5, arsenic release would most likely exceed the amount that would be released if the release concentration was at the MCL. 

### Figure I-14:

• Similar Se release would be expected for the test case

compared to the baseline case for all scenarios examined.


### • For the 95% probability scenario, selenium release from

both cases would be less than the amount that would be released if the release concentration was at the MCL and the LS ratio was the resultant LS ratio for the 95%case (i.e., around 100 L/kg). However, selenium release would be greater than the amount that would be released if the release concentration was at the MCLand the LS ratio was the LS ratio of the default scenario considered (i.e., 12.5 L/kg).

205