United States
           Environmental Protection
           Agency
Air and Radiation
6202J
EPA430-R-04-001
May 2004
M E T H A N
OUTREACH
' R O G R A M
              Methane Emissions From
                Abandoned Coal Mines
                    in the United States:
                  Emissions Inventory Methodology
                and 1990-2002 Emissions Estimates
                      SEPARATOR
          GAS COMPRESSOR
                               TO MARKET
      BLOWER
                             ABANDONED MINE WORKS

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       METHANE EMISSIONS
   FROM ABANDONED COAL MINES
      IN THE UNITED STATES:
EMISSION INVENTORY METHODOLOGY
AND 1990-2002 EMISSIONS ESTIMATES
             April 2004


    Coalbed Methane Outreach Program

    U.S. Environmental Protection Agency

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                  COALBED METHANE OUTREACH PROGRAM

The Coalbed Methane Outreach Program (CMOP) is a U.S.  Environmental Protection Agency
(EPA) voluntary program.  CMOP works with coal companies and related industries to identify
technologies, markets, and means of financing for the profitable recovery and use of coal mine
methane (a greenhouse gas) that would otherwise be vented to the atmosphere. CMOP assists
the coal industry by profiling coal mine methane project opportunities at the nation's gassiest
mines,  by  conducting mine-specific technical and economic assessments, and by identifying
private,  federal,  state,  and  local  institutions  and programs  that  could facilitate  project
development.

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                               ACKNOWLEDGMENTS

This report was  prepared under  Environmental Protection Agency  Contract 68-W-00-092  by
Raven Ridge Resources Incorporated. The principal authors are Mr. Michael Cote, Mr. Ronald
Collings, and  Mr.  Raymond  Pitcher of  Raven  Ridge Resources,  Incorporated, and  Clark
Talkington and Pamela Franklin of U.S. EPA.

The authors and U.S. EPA gratefully acknowledge the contributions of several individuals that
contributed their time and expertise in reviewing drafts of the report and providing insightful and
invaluable comments.

Kashy Aminian, West Virginia University

Clemens Backhaus, Fraunhofer UMSICHT (Fraunhofer Institute for Environmental, Safety, and
Energy Technology - Germany)

Philip Cloues, U.S. National Park Service
llham Demir, Illinois Geologic Survey

Michiel Dusar, Geologic Survey of Belgium

Roger Fernandez, U.S. Environmental Protection Agency

Satya Harpalani, Southern Illinois University, Carbondale

David Kirchgessner, U.S. Environmental Protection Agency, Office of Research & Development

Les Lunarzewski, Lunagas Party Ltd (Australia)

Jim Penman, UK Department of Environment, Food & Rural Affairs

Patrick Rienks, Ingersoll-Rand Energy Systems

Abouna Saghafi, Commonwealth Scientific & Industrial Research Organization (Australia)

Elizabeth Scheehle, U.S. Environmental Protection Agency

Karl Schultz, Climate Mitigation Works LLC (United Kingdom)

Peet Soot, Northwest Fuels Development Inc.

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                         TABLE OF CONTENTS

Table of Contents	i
List of Figures	iii
List of Tables	iv
Abbreviations and Acronyms	v
EXECUTIVE SUMMARY	1
1.0-INTRODUCTION	4
      1.1 GREENHOUSE GAS INVENTORY GUIDELINES AND PRACTICES	4
      1.2 DEFINITION OF AN ABANDONED COAL MINE	5
      1.3 PREVIOUS ATTEMPTS TO ESTIMATE ABANDONED MINE EMISSIONS	5
      1.4 REPORT STRUCTURE	6

2.0 - ABANDONED MINES AS A SOURCE OF METHANE EMISSIONS	8
      2.1 OVERVIEW OF COAL MINE METHANE	8
           2.1.1 Active coal mine emissions	9
           2.1.2 Abandoned coal mine emissions	9
      2.2 FACTORS INFLUENCING METHANE EMISSIONS	9
           2.2.1 Gas content and adsorption characteristics of coal	10
           2.2.2 Methane flow capacity of the mine	12
           2.2.3 Mine Flooding	13
           2.2.4 Active Vents	14
           2.2.5 Mine Seals	14

3.0-COAL MINE EMISSIONS DATA	15
      3.1 COAL MINE EMISSIONS DATA	15
      3.2 MINE STATUS INFORMATION	17

4.0-EMISSIONS ESTIMATION	19
      4.1 OVERVIEW	19
      4.2 FORECASTING ABANDONED MINE METHANE EMISSIONS USING
         DECLINE CURVES	19
      4.3 GENERATING DIMENSIONLESS DECLINE CURVES WITH FLOW
         SIMULATION	22
      4.4 DATA AVAILABILITY AND UNCERTAINTY	23
           4.4.1 Adsorption isotherms	24
           4.4.2 Permeability	26
           4.4.3 Pressure at abandonment	26
           4.4.4 Ventilation air emissions	26
      4.5 SENSITIVITY ANALYSIS FOR ADSORPTION ISOTHERM,
         PERMEABILITY, AND PRESSURE	26
      4.6 ANNUAL EMISSION ESTIMATIONS AS A FUNCTION OF MINE STATUS	27
           4.6.1 Venting mines	27
           4.6.2 Flooded mines	27
            4.6.3 Sealed mines	28
      4.7 CALCULATING ANNUAL METHANE EMISSIONS INVENTORY	29
           4.7.1 Mines of unknown status	30
            4.7.2 Combining the known status and unknown status inventories	30
US Environmental Protection Agency

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                 TABLE OF CONTENTS (CONTINUED)


5.0 CALIBRATION THROUGH FIELD MEASUREMENTS 	32
      5.1 FIELD MEASUREMENT METHODOLOGY	32
      5.2 COMPILATION OF DATA	33

6.0 ESTIMATING EMISSIONS FROM MINES CLOSED BEFORE 1972	35
      6.1 HISTORICAL TRENDS IN GASSY MINE EMISSIONS	35
      6.2 ESTIMATING LOCATIONS OF GASSY MINES ABANDONED BEFORE 1972 36
      6.3 ESTIMATING DATE OF ABANDONMENT FOR PRE-1972 MINES	38
      6.4 ESTIMATING INITIAL EMISSION RATES FOR PRE-1972 MINES	39
      6.5 CALCULATING TOTAL ABANDONED  MINE METHANE EMISSIONS  FOR
      MINES CLOSED PRIOR TO 1972	40

7.0 RESULTS OF THE 1990 - 2002 ABANDONED MINE METHANE EMISSIONS
   INVENTORY 	42
      7.1  1990 BASELINE INVENTORY	42
      7.2  EMISSIONS FOR 1991-2002	42
      7.3  INVENTORY  ADJUSTMENTS FOR  1990-2002 METHANE  RECOVERY
      PROJECTS	43
            7.3.1 Summary of U.S. Emissions	44
      7.4 KEY ASSUMPTIONS AND AREAS OF UNCERTAINTY	46
            7.4.1  Limited data on mines abandoned before 1972	47
            7.4.2  Biases in U.S. mine ventilation data	47
            7.4.3  Lack of data  on gasification prior to 1990	47
            7.4.4  Exclusion of surface mines emissions	47
            7.4.5  Total estimated uncertainty range	48
      7.5 PROJECTING FUTURE EMISSIONS FROM ABANDONED COAL MINES	49

8.0 CONCLUSIONS 	51

9.0 REFERENCES	53

APPENDIX A. U.S. Abandoned Coal Mine Database	A-1
APPENDIX B. State Agencies and Organizations	B-1
APPENDIX C. Combining Uncertain Parameters Using Monte Carlo Simulation	C-1
APPENDIX D. Effect of Barometric Pressure on Mine Venting	D-1
APPENDIX E. Sensitivity Analysis Calculations	E-1
APPENDIX F. Emission Inventory: Sample Calculations According to Mine Type	F-1
                                               US Environmental Protection Agency

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                               LIST OF FIGURES
Figure 1.  Abandoned Mine Methane Emissions Estimate (mmcf)for 1990-2002	3
Figure 2.  Map of U.S. Gassy Coal Basins	8
Figure 3.  Comparison of Methane Storage Capacity of Sandstone and Coal	11
Figure 4.  Typical Adsorption  Isotherms as a Function of Coal Rank	11
Figure 5.  Methodology for calculating abandoned mine emissions	21
Figure 6.  Cambria Mine Gob Well Decline Curve	22
Figure 7.  Dimensionless decline curve for non-flooding, venting abandoned mines	23
Figure 8.  Average methane adsorption isotherms for U.S. coal basins	25
Figure 9. Methane adsorption as a function of mine pressure for the Central
          Appalachian Basin	'.	25
Figure 10.  Emission model for abandoned flooding mines	28
Figure 11. Emission model for abandoned mine with different degrees of sealing	29
Figure 12. Year 2000 emissions inventory: methane emissions from abandoned mines	31
Figure 13. Vented emissions from unflooded abandoned mines in U.S. coal basins	34
Figure 14. Active coal mine methane emissions from nine states, 1971-1980	36
Figure 15. Mine closures in Colorado and Illinois, 1910 -1960	39
Figure 16. Active mine emission data for northern West Virginia	40
Figure 17. Emissions contribution from mines abandoned prior to 1972
          for the 1990-2002 inventories	41
Figure 18. Gassy coal mines abandoned annually, 1990-2002	43
Figure 19. Abandoned mine methane emissions estimate, 1990-2002	45
Figure 20. Net Abandoned Mine Emissions (CO2e and Gg methane)	45
Figure 21. Abandoned coal mine emissions from each U.S. coal basin, 1990 -2002	46
Figure 22. Range of abandoned mine methane emissions estimates, 1990-2002	48
Figure 23. Trends in coal mine emissions from gassy U.S. mines	49
US Environmental Protection Agency                                                     iii

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                               LIST OF TABLES
Table 1.  Data sources used to compile gassy abandoned coal mines database	16
Table 2.  Abandoned coal mines by basin	17
Table 3.  Status of abandoned mines	18
Table 4.  Adsorption isotherms available for each coal basin	24
Table 5.  Distribution of (known) types of abandoned mines for year 2000	30
Table 6.  Year 2000 abandoned mine emissions by coal basin, Bcf	31
Table 7.  Year 2000 abandoned mine emissions, tonnes of CO2e	31
Table 8.  Gassy abandoned mines located  in 17 counties	38
Table 9.  Distributions of methane emissions,  1971-1975	40
Table 10. Contribution of mines closed from 1920-1969 to the 1990 inventory	41
Table 11. Cumulative gassy coal mines abandoned, 1990 -2002 	42
Table 12. Abandoned mine methane recovery projects	44
Table 13. Summary of abandoned coal mine emissions by basin  (Bcf/yr)	46
IV
US Environmental Protection Agency

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      cf
      Bcf
      Gg
      kg
      km
      km2
      kPa
      mcf
      mcfd
      m3
      md
      mmcf
      PL
      psia
      psig
      scf
      t
      tonne
      VL
      AMDB
      BMP
      CO2e
      CBM
      CFD
      CMM
      EIA
      GHG
      GRI
      IPCC
      MSHA
      P
      STP
      USBM
      U.S. EPA
      V
  ABBREVIATIONS AND ACRONYMS

           Weights and Measures
cubic feet
billion cubic feet
gigagrams = 109 grams
kilogram = 103 grams
kilometer = 103 meter
square kilometer
kilopascals = 103 Pascals
thousand cubic feet
thousand cubic feet per day
cubic meter
millidarcies = 10"3 Darcies
million cubic feet
Langmuir pressure
pounds per square inch absolute
pounds per square inch gauge
standard cubic feet
short ton
metric ton
Langmuir volume

                Acronyms
Abandoned Mine Database
Bottom hole pressure
Carbon Dioxide global warming equivalent
Coalbed Methane
Computational fluid dynamics
Coal Mine Methane
Energy Information Administration
Greenhouse gas
Gas Research Institute
Intergovernmental Panel on Climate Change
U.S. Mine Safety and Health Administration
Pressure
Standard temperature and  pressure
United States Bureau of Mines
United States Environmental Protection Agency
Volume
                              Conversion Factors
      1 million m3 = 35.315 mmcf
      1 tonne CO2e = 2.483 Mcf CH4
      1 kPa = 0.145 psi
      1 m3/tonne = 32.04 scf/t gas storage
      1 mcf CH4 = 0.0001926 Gg CH4
US Environmental Protection Agency

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                             EXECUTIVE SUMMARY
Coal mine methane (CMM) emissions are one of the major sources of anthropogenic methane
emissions in the U.S., accounting for approximately 10 percent of total emissions. Current CMM
emission estimates, however, only include emissions from active, or working, mines and do not
account  for methane  vented from  abandoned  mines.   The  United States  Environmental
Protection Agency (EPA) has recently completed an  effort to quantify abandoned underground
mine methane (AMM) emissions both to improve the  accuracy of the CMM emissions inventory
and to assess mitigation opportunities.  According to these estimates, detailed in this report,
AMM emissions increased total U.S. coalmine methane emissions by about 13 billion cubic feet
(Bcf) in 2002, or about 5% of total U.S. CMM emissions.
U.S. EPA prepares  an annual  inventory to identify and quantify the country's anthropogenic
sources and sinks of greenhouse gas emissions. In addition to fulfilling its commitment to the
United Nations  Framework Convention on Climate Change (UNFCCC)  to publish and  make
available a national  inventory of greenhouse gas emissions,  the U.S. develops the  inventory
because systematically and consistently estimating national and international emissions is a
prerequisite for accounting for reductions and evaluating mitigation strategies.

Thousands of closed coal mines in  the United States  and other  countries  continue to emit
methane, contributing to the  total greenhouse  gas emissions from coal mining.  The unique
features of abandoned mines, however, require a separate emissions estimation methodology
from that employed  for operating mines. To date, the  coal  mine  methane  (CMM)  emission
inventory is limited to operating  (active) mines, in part because the Intergovernmental  Panel on
Climate Change (IPCC)  has  not provided  guidance  on how to quantify emissions  from
abandoned mines  This report proposes  a  credible  methodology for determining  methane
emissions from  abandoned  underground  coal  mines  and uses this methodology to quantify
methane emissions from abandoned U.S. mines for each year from 1990 through 2002.

The  method outlined in this report  is consistent with  the "Tier 2" approach for estimating
emissions from  active mines  as described in the Revised 1996 IPCC Guidelines for National
Greenhouse Gas Inventories (IPCC, 1997). Under this approach, data availability dictates
whether emissions estimates are based on a country- or basin-specific method.  This method
consists of five steps  as described below:

•  Step 1    Create a database  on abandoned  gassy mines.  Based on an  analysis of
             methane emissions at  operating  mines, 98% of all CMM emissions come  from
             mines that emit more than 100 mcfd (thousand cubic feet  per day).  Assuming
             that emissions profiles for abandoned mines are correlated to their emissions
             during active mining operations, EPA compiled a database containing information
             on 374 abandoned  coal mines that produced emissions greater than 100 mcfd
             when  they were active. The database includes the name, location,  coal basin,
             date of abandonment,  emission  rate at closure, and status (venting, flooded,
             sealed, or unknown  status)  of each  mine.  For mines  closing  since 1990, the
             emission  rate  includes  both   ventilation   emissions  and   emissions   from
             degasification systems.
US Environmental Protection Agency

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•  Step 2:    Identify the factors affecting methane emissions and develop coal basin-
             specific  decline curves.  Several  important  factors impact  mine methane
             emissions, including the gas content of the coal, flow capacity in the coal seam
             and the mine void, and the time since  abandonment.  The latter is especially
             important because gas emissions decline significantly following closure and level
             off over time. Coal basin-specific geological data and coal mine-specific emission
             data were used  to develop input parameters for a numerical  model.  Decline
             curves were then used to forecast abandoned mine  methane emissions as a
             function of time since the mine was abandoned,  given the characteristics of a
             specific coal basin.

•  Step 3:    Calibrate through field measurements.  Field  measurements  are an important
             tool  used  to  verify whether  theoretical calculations  accurately reflect  actual
             emissions  from  abandoned mines.  A  series of field measurements  were
             conducted at seven abandoned mines across the country.  The goal of the field
             study was to determine the measurement interval and duration necessary to
             accurately predict average methane emission rates from a mine vent. The field
             measurements were also  used to test the accuracy of the basin-specific decline
             curves.  Measurements from a  previous EPA study (Kirchgessner, 2001) of
             abandoned mine vents at 21 mines were used to validate these results.

•  Step 4:    Calculate a national emissions inventory for each year.  Once decline curves
             were developed, emission estimates of each mine were calculated according to
             their status: venting, flooded, sealed, or unknown.  To arrive at a total abandoned
             mine emission inventory in a given year, Monte Carlo  simulations were used to
             sum the probability distributions for the mines within each basin, and then to sum
             the emission distributions for the basins.

•  Step 5:    Adjust  for  methane recovery and determine the  net total  emissions.
             Methane recovery projects are known to exist at about 20 abandoned mines in
             the US. The quantity of gas recovered and used at the abandoned mine projects
             is subtracted from the total emissions to determine the net total emissions.

Employing this methodology, abandoned mine emissions for 1990 were estimated to range from
6.9 to 10.1 billion cubic feet (Bcf), or 2.8 to 4.1 million tonnes CO2 equivalent (CO2e), with a best
estimate of 8.4 Bcf or 3.4 million  tonnes CO2e. For the year 2002, additional contributions of
emissions from 163  gassy  mines that  closed  between  1991-2002, increases the range of
emissions estimates to 10.9 to 14.7 Bcf (4.4 to 5.9 million tonnes CO2e), with a best estimate of
12.8  Bcf  (5.2 million tonnes CO2e).  However,  mine methane recovery  projects  reduce
abandoned mine  methane emissions by  approximately 2.6  Bcf (1.0 million tonnes CO2e),
bringing the net emissions for 2002 to approximately 10.2 Bcf (4.1 million tonnes CO2e).  Figure
1 shows  the  estimated annual abandoned  coal mine methane emissions for 1990 - 2002,
including emissions avoided due to methane recovery projects.

This methodology and the calculated emissions estimates are based on the best available data.
At a 95% confidence interval,  the current level of uncertainty is approximately  + 20%. This
uncertainty range accounts for four important areas of uncertainty that could significantly impact
the emissions inventory calculations: limited data on mines closed before 1972, biases in the
U.S. mine ventilation data, no  data on mine drainage before  1990,  and exclusion of surface
mine emissions. There are also important uncertainties associated with poor data availability for
                                                       US Environmental Protection Agency

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coal permeability, the condition of abandoned mines (whether sealed or flooded), and, where
applicable, the effectiveness of mine seals.

             Figure 1. Abandoned Mine Methane Emissions Estimates, 1990-2002
18.0 -
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1990 1991 1992 1993 1994 1995 1996 1997 1998 1999 2000 2001 2002
The methodology and emission estimates presented in this report are a first attempt to quantify
emissions from abandoned coal mines in the U.S.  EPA will continue to refine the methodology
to quantify abandoned mine emissions with  greater certainty.  Some  important  next steps
include:

   •   Identifying all abandoned mine methane recovery projects in the U.S. that operated from
       1990 to the present and obtaining data on emission reductions;

   •   Obtaining more field data to verify methodological results and to serve as the basis for
       refinements to the methodology;

   •   Developing methodologies to set baselines and  calculate emissions avoided on a
       project-specific basis; and

   •   Incorporating the abandoned mine emissions into the U.S. Inventory of Greenhouse Gas
       Emissions and Sinks.
US Environmental Protection Agency

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1.0    Introduction

EPA prepares an  annual  inventory of  its greenhouse gas (GHG) emissions to track U.S.
progress in  meeting  its  commitments under the  United  Nations  Framework  Convention on
Climate Change  (UNFCCC). Active coal mines, which  account for  nearly  10% of U.S.
anthropogenic methane emissions, are  included in the U.S. inventory.  Coal mines release
methane, a greenhouse gas over 20 times more potent than carbon dioxide, as a direct result of
the coal mining process. In 2002, operating coal mines liberated 174 billion cubic feet (Bcf) of
CMM.  Of this amount, 44 Bcf was recovered,  resulting in net emissions of 130 Bcf (53 million
metric  tons of carbon dioxide equivalents, or  million tonnes CC^e) from active  mines (EPA,
2002).'

In the U.S., extensive data availability has facilitated the development of emissions estimates for
active mines with a high degree of confidence.  The location and operating status of the mines
are known;  vent air  emissions are measured by the  Mine Safety &  Health Administration
(MSHA) at least quarterly; and gas volumes sold are recorded by state tax authorities or oil and
gas boards   In addition, many coal mining companies in the U.S. voluntarily cooperate with
EPA to refine the methane emission estimates.

In contrast, quantifying emissions from thousands of abandoned  mines across the country has
proven much more challenging. For many of these mines, there  are few if any data, especially
for mines  closed before  1972. Some of these abandoned mines continue to emit methane,
contributing to total greenhouse gas emissions from the coal sector. EPA conducted this study
to determine the magnitude  of abandoned coal mine methane  emissions and to assess the
technical feasibility of including this source in  the U.S. greenhouse gas emissions inventory.
Consistent with the stated goals of the U.S. Greenhouse Gas Inventory, the purposes of this
study are  twofold  1) to  develop  a credible methodology for determining methane emissions
from abandoned underground coal mines, and 2) to quantify those emissions for each year from
1990 through 2002 The methodology developed in this report incorporates quantitative models
with  coal  basin-specific  parameters,  calibrated with field measurements  at  several  mines.
These  emission calculations were used in  conjunction with a comprehensive database of U.S.
mines  abandoned  since 1972 to generate an aggregate estimate of U.S.  abandoned mine
methane emissions for each year from 1990 to 2002.


       1.1    Greenhouse Gas Inventory Guidelines and Practices

Current guidelines of the Intergovernmental  Panel on Climate Change (IPCC, 1997)  establish
three different methodological levels (called "tiers") for estimating  greenhouse gas emissions
depending on the level of detail available.   For coal  mining, the three tiers are  described as
follows:

     •  Tier 1:  the least  accurate  estimate; based on national  coal production data and
                global average emission factors.
1 130 Bcf CHj = 130 x 109 ft3 CH4 x (0.04246 Ib CH4 / ft3 CH4 ) x (21 Ib CO2 / Ib CH4 )(GWP) x (1 kg C02 /
2.2 Ib CO; ) x (metric tonne/1000 kg) = 52.7 million metric tonnes CO2 equivalent (CO2e). Here, the factor
of  21 Ib CO, to 1 Ib CH4 reflects the global warming potential  (GWP) of CH4, which is 21 times greater
than CO2 on a mass basis over a 100 year time frame.


4                                                      US Environmental Protection Agency

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     •   Tier 2:   a more detailed estimate; based on national average emission factors, or if
                 more  specific  emission factors  are  available,  on sub-national  emission
                 factors.
     •   Tier 3:   the most detailed estimate; based on mine-specific emission measurements.

The methodology developed  in this report is consistent with Tier 2 guidelines.  Under this
approach, emissions estimates can be based on country- or basin-specific methods, depending
on data availability.  In the U.S., data on the gas content of coal are readily available, both for
entire coal basins and within  each basin. To implement the Tier 2 approach, EPA examined
emissions data from hundreds of gassy active mines, as well as a limited number of abandoned
mines. Computer simulation of post-mining emissions, together with the available  emissions
data, produced basin-specific  decline curves based on established mathematical equations for
gas rate declines. Following general IPCC guidance, EPA relied on both statistical analysis and
expert judgment to develop  emissions factors for abandoned mine emissions in each U.S. coal
basin.


       1.2    Definition of an Abandoned Coal Mine


In order to avoid  double counting or undercounting of emissions, it is important to clearly define
the term "abandoned mine."2 The  Mine Safety & Health Administration (MSHA) classifications
for inactive or non-producing mines are as follows:

       1) Non-Producing, Men Working:                No coal being produced, but persons
                                                    are maintaining equipment.

       2) No One Working,  Temporarily Abandoned:     Coal  production has ceased,  mine
                                                    may reopen in near future.

       3) No One Working, Permanently Abandoned:     Mine has been  abandoned for more
                                                    than 90 days.

Although the MSHA definitions are practical from an operational perspective,  they are not as
clear when  defining mine emissions as active  or abandoned.  Often, a coal mine will stop
producing coal (e.g., Category 2  above),  but it will continue to operate ventilation  fans for
months or even  years afterwards. During  this time, the coal mine must report the methane
emissions to MSHA as part of the active coal mine emissions inventory.  Thus, it would be
double-counting to include  them  as part  of the abandoned coal mine  emissions  inventory.
Taking this into account for this methodology, the term "abandoned" is defined for purposes of
developing an emissions estimate as the time when active mine ventilation ceases.


       1.3  Previous Attempts to Estimate Abandoned Mine Emissions


While the IPCC has recommended that emissions from abandoned mines be included in the
GHG emissions  inventory,  it  has  not yet provided  any methodological  guidance on how  to
2 The Mine Safety & Health  Administration (MSHA)  catalogs information on  individual mines using
Federal Information Processing Standards (FIPS) codes.   For coal mines, MSHA assigns both an
operational and auxiliary status regarding mining activities; these codes are defined  in the Code of
Federal Regulations (30 CFR Part 50, User's Handbook).


US Environmental Protection Agency                                                       ฃ

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calculate abandoned mine emissions, due in large part to the lack of reliable data (IPCC, 1997).
EPA's earlier efforts to develop a methodology for abandoned mine emissions resulted in wide-
ranging estimates, from 1 to 34  Bcf per year. In a separate EPA study on developing improved
methane emission estimates at  coal mining operations, 1995 abandoned mine emissions were
estimated to be 7.4 Bcf, based on pre-abandonment data and vent pipe emissions measured at
21  abandoned underground  coal  mines  in  the  Appalachian  and   Black  Warrior  basins
(Kirchgessner et al., 2001).


      1.4    Report Structure


The report  outlines a logical  approach for estimating CMM emissions.  An overview of each
major section is presented below.

Section 2.0   Abandoned Mines as a Source of Methane Emissions
              This section describes the location of gassy underground mines in the U.S. and
              introduces readers to the factors affecting methane emissions from abandoned
              coal mines.

Section 3.0   Coal Mine Methane Emissions Data
              This  section  describes the data sources for abandoned mines in  the U.S.,
              including data limitations, and summarizes these data.

Section 4.0   Emissions Estimation
              This section outlines the  quantitative procedures to estimate abandoned mine
              methane emissions.   Because methane emissions at abandoned mines  will
              decline over time, basin-specific decline curves were developed  to calculate
              emission estimates for individual mines.  These mine-specific  emissions were
              then totaled to develop a national estimate. Because taking measurements at
              every abandoned mine is not practical, the proposed methodology incorporates
              a  probabilistic  analysis  (Monte Carlo simulation) to  develop  a  range  of
              emissions estimates with  a high degree of confidence.

Section 5.0   Calibration Through Field Measurements
              This section describes the field measurements EPA undertook to  validate the
              calculated estimates.

Section 6.0   Estimating Emissions from Mines Closed Before 1972
              This section presents the results of EPA's  efforts to gather data and quantify
              abandoned mine emissions  from mines  closed  before 1972.  Unfortunately,
              critical data are missing  for mines closed  prior  to 1972, including the active
              mine emissions data, time of abandonment, number of gassy mines, and mine
              status. Therefore, this information was estimated based on extrapolations from
              physical, geologic and hydrologic constraints that apply to mines  closed after
              1972.

Section 7.0   Results of the 1990-2002 Abandoned Mine Methane Emissions Inventory
              This section presents the estimates of total methane liberated from abandoned
              U.S.  mines annually from 1990 through 2002. Net emission estimates include
              adjustments for mine methane recovery projects.  This section also discusses
              the range of variability and uncertainty in the calculations.
                                                      US Environmental Protection Agency

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Section 8.0    Conclusions
               This section presents conclusions and proposed  next steps to set a roadmap
               for  possible  future  activities  to  improve  these emissions  estimates for
               abandoned mines, and to develop methodologies for project-specific baselines.
US Environmental Protection Agency

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2.0   Abandoned Mines as a Source of Methane Emissions
      2.1    Overview of Coal Mine Methane
Coalbed methane is formed during coalification, the process that transforms plant material into
coal.  Organic matter accumulates in swamps as lush vegetation  dies and decays.  As this
organic matter becomes more deeply buried, the temperature and pressure increase, subjecting
the organic matter to extreme conditions that transform it into coal and methane, as well as
byproducts  including carbon dioxide, nitrogen,  and water.  As heat and pressure continue to
increase, the carbon content ("rank") of the coal increases.

The methane trapped in coal seams is commonly referred to as coalbed methane (CBM) or coal
seam gas.  Generally, the deeper the  coal seam and/or higher the coal rank, the higher the
methane content.  Coalbed methane is known as coal mine methane (CMM) when mining
activity releases the methane, a potent greenhouse gas.

Not all coal seams are gassy (generally defined as mineable seams capable of producing more
than 100 mcfd in coal mine ventilation emissions).  In the U.S.,  gassy coals are located in the
Appalachian Basins  in the  East, Black Warrior Basin in the South, the  Illinois Basin in the
Central  U.S., and  several western  basins such as the San Juan  and  Powder River Basins.
Figure 2 shows the locations of gassy coal basins in the U.S
            Figure 2. Map of U.S. Gassy Coal Basins with Underground Coal Mines
                BITUMINOUS COAL BASIN
                                               ANTHRACITE COAL BASIN
                                                     US Environmental Protection Agency

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              2.1.1  Active Coal Mine Emissions

To ensure mine safety,  active  underground coal  mines must remove methane from the mine
using powerful ventilation systems.  For particularly gassy mines,  operators employ methane
drainage systems to supplement their ventilation systems.  In the U.S., these drainage systems
consist  of pre-mine vertical boreholes (drilled from the surface), in-mine horizontal boreholes
drilled prior to mining, or vertical or in-mine gob wells.3 The methane gas emitted through the
ventilation and drainage  systems is either released directly to the atmosphere or recovered and
used.

              2.1.2  Abandoned Coal Mine Emissions

As mines mature and coal seams are mined out,  mines are closed  and eventually abandoned.
Often, mines may be  sealed by filling shafts or portals with gravel and capping them  with a
concrete seal. Vent pipes and  boreholes may be plugged in a similar manner to oil  and gas
wells.

As active mining stops, the mine's gas production decreases, but the methane liberation does
not stop completely.  Following an initial decline,  abandoned mines can liberate methane at a
near-steady rate over an  extended period of  time. The  gas migrates up through conduits,
particularly if they have not been sealed adequately.  In addition, diffuse emissions can occur
when methane migrates to the surface through cracks and fissures in the strata overlying the
coal mine.

After they are abandoned, some  mines  may flood as a result  of intrusion of groundwater or
surface  water into the void. Flooded mines typically produce gas for only a few years.


      2.2    Factors Influencing Mine Methane Emissions


Within a coalbed, methane is stored both as a free gas in coal's  pores and fractures, as well as
on  the  coal surface through physical adsorption. As the  partial pressure of methane  in the
fracture  (cleat) system of the coal decreases, the methane desorbs from the coal and moves
into the  cleat system as free gas. The pressure differential between the cleat system and the
open mine void4 provides the  energy to  move  the methane  into the  mine.  Driven by this
pressure differential between the gas in the mine and atmospheric pressure, the  methane will
eventually flow through existing conduits and will be emitted to the atmosphere.

Many factors can impact the  rate of CMM emissions at both active and abandoned mines. The
most important factor is  the  total gas (methane)  content of the coal, which has been directly
linked to methane emissions from mining activities (Grau, et al. 1981, EPA, 1990)

The time since abandonment is  a  critical factor  affecting an abandoned  mine's annual
emissions, as the mine's emissions decline steeply as a function of time elapsed.5 EPA has
developed a decline curve, which describes the rate at which methane continues to desorb from
3 A "gob" or "goaf is the rubble zone formed by collapsed roof strata caused by the removal of coal.
4 The mine void refers to the mined out area of the coal seam.
5 The decline of CMM emissions begins with the cessation of coal production, although abandoned mine
emissions officially begin only when active (forced) ventilation of the mine ceases.
US Environmental Protection Agency

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the coal after abandonment,  moves  into the mine  void, and  is eventually released to the
atmosphere.   The decline  curves are strong functions of time: the methane emissions rate
decreases rapidly in the years immediately after a mine closure, and flattens out after several
decades. The development of these decline curves is described in Section 4 of this report.

Other factors impacting the rate of methane emission include mine size, flooding,  sealing, and
the coal's permeability, porosity, and water saturation.

The remainder of this section  discusses in greater detail several additional factors influencing
abandoned mine emissions:

                •   Gas content and adsorption characteristics of coal
                •   Methane flow capacity of the mine
                •   Mine flooding
                •   Open (active) mine vents
                •   Mine seals

Each of these factors can impact methane emissions independent of the other factors, but in
almost all cases several factors are important.

              2.2.1  Gas Content and Adsorption  Characteristics of Coal
Compared to many sedimentary rocks, coal beds have the capacity to store a large amount of
methane gas.6 Coal can hold a significant amount of methane in the adsorbed state because of
the extensive internal surface area of the coal matrix (up to 250 square meters/gram, or 2.4
billion square feet per ton).7  Figure 3 illustrates the methane storage capacity of a middle rank
coal compared with the storage  capacity of a similar mass of (non-adsorbing) sandstone having
a porosity of 15%. This figure illustrates that coal can contain significant quantities of methane
even at very low pressures. The gas content of coal is generally expressed as standard cubic
feet per short ton (scf/ton), or cubic meters per metric ton (m3/tonne).8

This difference in storage capacity is  due primarily  to coal's  internal pore  structure.   For
example, porosity in sedimentary rock (e.g. sandstone and limestone) is mostly in the mesopore
(20 to 500 angstroms) and macropore (>500 angstroms) range.  In contrast, a significant fraction
of the coal matrix is in the micropore range (<20 angstroms).9 The  methane content at a given
temperature and pressure generally increases with coal rank  because of the  increase in the
percentage of micropores and surface area available for methane adsorption (Figure 4).
6 The quantity of gas that can be stored in the pore space of most sedimentary rock is a function of
temperature and pressure as described by the real gas law.
7 The density of the adsorbed methane is approximately its liquid density at atmospheric pressure boiling
point (Yee et al., 1993).
  32 scf/ton is approximately equal to 1 m3/tonne.
9 As  coal increases in rank, the pore structure of the matrix changes. The percentage of the total matrix
porosity in the micropore range increases with increasing rank from about 30% for a lignite to about 80%
for an anthracite (Can, et. al., 1972).


10                                                      US Environmental Protection Agency

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           Figure 3. Comparison of methane storage capacity of sandstone and coal
1,000 -
900


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500 1 ,000 1 ,500 2,000 2,500 3.000 3,500
Pressure, psia
          Figure 4. Typical adsorption isotherms as a function of coal rank (GRI, 1996)
                                                                              10
               I
                    0     325    650    975    1300   1625     )9SG   2275
                                          Depth (ft)

                     0     140    280   420     560    700     840     980
                                        Pressure {psia)
The curves shown in Figure 4 are called adsorption isotherms because they are measured at a
constant temperature.11 Adsorption  isotherms can be characterized by mathematical functions
based  on  theoretical adsorption  properties.  One  function  commonly  used  for  methane
10
  Depth indicated in Figure 4 is derived from the fresh water pressure gradient of 0.43 psi/ft (GRI, 1996).
  At constant pressure, increasing temperature decreases the amount of adsorbed methane.
US Environmental Protection Agency
11

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    •  Permeability, k, a property of the porous media (coal) plays a major role in the rate at
       which gas can flow from the unmined coal into the void space of the abandoned mine.
       Unfortunately, measurements of the absolute permeability of coal are scarce.

    •  The area, A, across which gas moves from the unmined coal into the void space can be
       very large  because  of the  large  areas  of exposed coal  in  an  underground mine.
       Determining the coal's surface area in an abandoned mine is very difficult.

    •  The pressure gradient from the coal to the void space of the mine decreases over time
       as the gas  is released and the  pressure in the coal seam is reduced.  As a result, the
       emissions rate from an abandoned mine decreases over time.

In an application related to coal mine methane production, gas production from oil and gas wells
is predicted using Darcy's Law together with material balance  equations. In this  context, the well
acts as a material  sink whose rate of withdrawal (q) is a  function of the difference between a
specified pressure at the  well, (Pw), and the  pressure at some outside boundary of the gas
reservoir (Pr).  For a gas, this function takes the following form:

                    q = PI (Pw2 - Pr2)n                                     (Equation 3)

where:
                    q = volumetric rate of gas production
                    Pw = pressure  at the well
                    Pr =  pressure of the gas reservoir
                    PI =  Productivity Index
                    n = empirically derived exponent13

By convention, flow from  the reservoir to the well (q) is  a negative value. Equation 3 is
essentially the same as Equation 2, modified for a gas and  combining the permeability of the
rock, the viscosity of the gas, the geometry and configuration of the pressure sink and outside
gas reservoir, and the thickness of the flow unit into the  PI term.

By analogy,  the coal  mine  and its connection  to the  atmosphere  (via  the vent shaft  or
overburden fracture conduit) acts as  the wellbore, and the unmined coal within and peripheral to
the mine is the reservoir of the stored methane. The PI  can be considered a constant at the low
pressures involved in coal  mining. The application of Equation 3 to abandoned mine methane
emission forecasting will be discussed later in this report.

              2.2.3 Mine flooding

Over time,  abandoned mines may partially  or  completely flood, which  will decrease  or
completely shut off gas flowing into the mine.  The  inhibition of  gas flow depends  on  the
pressure balance between  the gas within the coal and the water in the coal cleat system.  Even if
the gas  phase is  at a higher pressure  than  the water phase, the  presence of water  will
substantially inhibit gas flow into the mine. As the water level rises in a mine, the gas flow will be
reduced  more rapidly than it would  have otherwise, because as the coal  cleat becomes re-
saturated with water, its relative permeability to gas decreases. Thus, the presence of water in
the coal cleat system decreases the apparent permeability of the coal seam.
13 The exponent n accounts for turbulence and other non-ideal flow conditions (Slider, 1983).


US Environmental Protection Agency                                                         13

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Mine flooding  plays a critical role in methane emissions from abandoned coal  mines.   For
example, even if a coal  mine contains  a  large quantity of methane and the coal is highly
permeable, if the mine rapidly floods the total methane emitted will be far less than if the mine
had remained dry.

              2.2.4 Active vents

At some abandoned mines, vent pipes relieve the buildup of pressure resulting from desorption
and flow of methane into the mine void. These vents are installed to prevent methane from
migrating into  surrounding strata.  An abandoned mine with  an  open (or "active") vent  will
behave very much like a natural gas well (at a much lower pressure regime).

Methane emissions from venting  mines are a function of the pressure differential  between the
vent and the gas in the coal bed. The surface opening of the vent is at atmospheric pressure,
while the gas  within the unmined coal seam near the mine  void will  range from  atmospheric
pressure (14.7 psi,  or 1.01 bars) to tens of psi (more than  1 bar) above atmospheric pressure.

Mines with  open vents are known to "breathe" with atmospheric changes.  In other words, the
mines emit methane during times of low atmospheric pressure and pull air in during times of
high atmospheric pressure. The effect of barometric pressure on measured vent emission rates
is described in Section 5.2.
             2.2.5 Mine seals

While many abandoned mines have active (open) vents, some mines are sealed in an attempt
to prevent unauthorized access or the escape of methane gas. Even during active mining, seals
are placed in worked-out areas of the mine to reduce fresh air ventilation requirements as a
cost-saving measure. Old shafts and drifts are commonly plugged with cement.

It is  common, however, for gas to leak out  around these plugs or to make its way through
fractures in the overlying strata. The seals  are generally assumed to leak even at very low
pressure differentials (e.g., a few tenths of a psi), and they typically degrade over time. Although
mine seals can impact the rate of flow, they are  not considered to be effective at preventing
atmospheric methane emissions over time.
14                                                     US Environmental Protection Agency

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3.0   Coal Mine Methane Emissions Data

The first step in developing an  emissions inventory is collecting  information on abandoned
mines. There are numerous abandoned mines in the United States, and it is impractical to visit,
measure, and collect mine-specific data from individual mines. Thousands of U.S. coal mines
that operated during the 20th century have since  closed.14 MSHA estimates that over 7,500
underground  coal  mines have  been  abandoned  just  since  1980 as  a result of significant
restructuring in the coal industry  (U.S. Department of Labor, 2000). Throughout the 1990s, on
average, 14 gassy mines were abandoned each year. Therefore, to estimate U.S. abandoned
mine emissions with a reasonable degree of confidence for this study, EPA relied on historical
emissions data, available MSHA databases, and information collected during field studies.  EPA
emissions estimates are also based on known characteristics of coal basins, including lithology,
coal rank, coal depth, coal seam gas content, and hydrologic characteristics.
Emissions data for coal mines has been compiled only since 1971, originally by U.S. Bureau of
Mines (USBM), and currently by MSHA. Thus, gathering historical information for abandoned
mines in the U.S. is difficult for mines abandoned prior to 1972, for which very few data exist.
EPA has developed a  methodology to estimate emissions contributions from these older
abandoned  mines  based  on  extrapolation  from  mines  closed in and after  1972  (this
methodology is described in detail in Section 6). The remainder of this section  and Section 4.0
describe data sources and methodology for estimating emissions from mines abandoned in or
after 1972.


       3.1   Coal Mine Emissions Data

For mines abandoned in or after 1972, EPA compiled data from  several  key sources to
characterize abandoned mines and their emissions.  Table 1 shows the data sources that EPA
used to  compile a database of gassy abandoned mines.

•  Mine Safety and Health Administration (MSHA). The largest source of data assembled on
   abandoned mines is  the  MSHA Coal  Mine Information System (MIS) Database, which
   contains information for over 7,500 coal mines abandoned since 1980, categorized on the
   basis of average daily emissions. The MSHA MIS database lists 98 mine closures during the
   1980s for mines that had active emissions  greater than 200 mcfd. Since 1990, MSHA has
   provided EPA with information on all coal  mines with emissions greater than 100 mcfd.15
   One limitation of this data set is that it includes only ranges of emissions data, rather than
   more precise estimates.16

•  United States Bureau of Mines (USBM). The USBM produced a  series of five information
   circulars on coal mine emissions from 1971-1985. EPA used these reports to identify gassy
14 Only a small portion of all US mines are gassy. In 2001, for example, approximately 125 of nearly 600
operating underground coal mines (20%) contained  detectable methane levels in ventilation air and were
considered gassy (methane emissions above 100,000 cubic feet per day).  The percentage of gassy
mines was much lower during the early- and mid-twentieth century, when most coal mining occurred in
small shallower mines.
15 Except for the years 1991 and 1992, when ventilation fan data were not collected.
16 All mines reporting emissions greater than 200 mcfd were designated as one of three categories: 200 -
500 mcfd, 500-1,000 mcfd, or >1,000 mcfd.


US Environmental Protection Agency                                                       15

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   active  mines with emissions greater  than 100  mcfd that closed during this  period.
   Subsequently, EPA also used these data to establish average basin-specific emission rates
   for gassy mines. To estimate emissions from individual mines that closed during the 1980s,
   EPA extrapolated from the USBM information to determine basin-average emission rates for
   the mines with emissions greater than 1  mmcfd.

•  State agencies. Some additional comprehensive mine opening and closure information was
   obtained  through state mine and mineral agencies.  Mine maps were available for some
   mines through coal mine operators and state geologic surveys.
     Table 1.  Data sources used to compile gassy abandoned coal mines database
Year
1971
1973
1975
1980
1985
1980-1990
1990-2002
(excluding '91 & '92)
Data Source
USBM
USBM
USBM
USBM
USBM (partial list)
MSHA MIS Database
MSHA Quarterly
Reports
Range of
Vent
Emissions
> 100 mcfd
> 100 mcfd
> 100 mcfd
> 100 mcfd
> 1 00 mcfd
> 200 mcfd
> 100 mcfd
Degasification
Data
No
No
No
No
No
No
Yes
Number
of Mines
199
178
196
200
85
98
95-182
EPA used these data sets to compile a list of abandoned gassy mines that constitute the vast
majority of abandoned mine emissions. This was a multiple step process:

   1.  First, EPA was able to establish a national profile of abandoned active mines. The 1997
       MSHA mine methane  emissions dataset consisted of all (586) active coal  mines with
       detectable emissions, not just mines with emissions greater than 100 mcfd. Based on
       these 1997 active mine data, EPA determined that mines emitting greater than 100 mcfd
       comprised 98% of emissions for all  mines with  reportable emissions (EPA, 2002). The
       USBM data showed similar results for the 1970s.

   2.  EPA used an analogous assumption that the profile of abandoned mines is substantially
       similar to the profile of active mine emissions: that is, that 98% of abandoned mine
       emissions come from  mines that produced  98% of their emissions when they were
       active.  In other words, mines that emitted more than 100 mcfd when they were active
       will contribute more than  98% of the total abandoned mine emissions when  they are
       closed.

   3.  EPA determined which abandoned mines constitute a representative sample population
       of  abandoned  mines. 393 mines  that were  abandoned between 1972 and  2002
       produced emissions greater than 100 mcfd when they were active (Table 2). Analogous
       to the known distribution of active mine  methane emissions, these  393 abandoned
       mines  are assumed to account for 98%  of all abandoned mine emissions.  Thus, these
       mines  constitute the sample population used  as the  basis for estimating  methane
       emissions from all abandoned mines in the U.S..
16
US Environmental Protection Agency

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                       Table 2. Abandoned Coal Mines by Basin
Coal Basin
Central Appalachian
Northern Appalachian
Penn. Anthracite
Illinois
Black Warrior
Piceance
Uinta
San Juan
Other
Total
Total No. of
Abandoned Coal
Mines
6075
834
312
100
68
28
28
2
135
7582
Coal Mines That Had
Active Emissions
>100 mcfd
(Years 1972 -2002)
178
101
0
64
14
14
15
0
8
393
Gassy
Mines as a
% of Total
Mines
2.9
12.1
0.0
64.0
17.9
50.0
54.0
0.0
6.0
5.0
From 2002 MSHA Data base
       3. 2    Mine status information


Additional mine-specific information was collected on each of the targeted mines from state and
federal regulatory agencies and from the mine operators where possible. Information collected
included:

          •   Mine-specific maps
          •   Mined-out acreage
          •   Locations of vents and shafts
          •   Degree of flooding
          •   Status of mine (e.g., sealed or venting to the atmosphere)

Table 3 shows the status of the 393 gassy abandoned mines in the database.17 The entire list of
393 coal mines in the database can be found in Appendix A, including the status of the mine (if
known), the date of abandonment, emissions at abandonment, and coal basin.  Of the 393
mines, 244 (62%) of these abandoned mines were classified as either:

          •  Vented to the atmosphere,
          •  Sealed to some degree (either earthen or concrete seals),  or
          •  Flooded (enough to inhibit methane flow to the atmosphere).

The  status of the remaining  149  mines (38%) is unknown. These "unknown"  mines were
classified into one of these three categories by generalizing on the basis of other mines in a
given coal basin, using a  probability  distribution analysis.  For example, in  the Black Warrior
basin, 92% of the mines are  known to  flood once they are abandoned, but only 21% of the
mines in the Northern Appalachian basin do so (Table 3). As a result, one would expect a larger
17 Information regarding the status of abandoned mines was obtained from state government agencies in
ten states (Appendix B).
US Environmental Protection Agency
17

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percentage of the abandoned mines in the Black Warrior basin to be flooded  compared with
abandoned mines in the Northern Appalachian basin.

                 Table 3. Status of Abandoned Mines in U.S. Database
Basin
Central Appalachia
Illinois Basin
Northern Appalachia
Warrior Basin
Western Basins
Total
Sealed
(% of
Known)
24 (25%)
18(55%)
36 (49%)
1 (8%)
20 (74%)
99 (43%)
Vented
(% of
Known)
25 (26%)
3 (9%)
23(31%)
0 (0%)
5(19%)
56 (16%)
Flooded
(% of
Known)
48 (49%)
12(36%)
15(20%)
12(92%)
2 (7%)
89 (42%)
Total Known
97 (54%)
33 (52%)
74 (74%)
13(93%)
27 (77%)
244 (62%)
Unknown
Status
83 (46%)
31 (48%)
26 (26%)
1 (7%)
8 (23%)
149(38%)
Total Mines
180
64
100
14
35
393
Data on adsorption  isotherms,  gas content, flow capacity and abandonment status are not
available for all of the 374 gassy U.S. underground coal mines known to be abandoned since
1972. However, the methane ventilation rate before abandonment and the date of abandonment
are available for the post-1971 abandoned mines. Mine degasification data are available from
1990 to present  Several adsorption isotherms for the most commonly mined coals in each coal
basin are documented (Masemore, et al., 1996), as described below in Section 4.4.1.
18
US Environmental Protection Agency

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4.0   Emissions  Estimation

       4.1   Overview

Once the database of  abandoned mines is compiled, it is possible to calculate emissions based
on the factors described in Section 2.2. Figure 5 illustrates the steps involved in the calculation
procedure.

As Figure 5 indicates, the template for calculating abandoned mine methane emissions is based
primarily on the status of the mine, whether flooded,  vented, sealed, or unknown. Emissions
calculations for each type follow a similar sequence of steps.
    •   Vented mines.  Closed mines are often intentionally left vented to the atmosphere to
       allow methane to escape  and prevent the dangerous or explosive buildup of methane
       underground. Even after active ventilation measures (such as fans) cease and the mine
       is officially abandoned, the open access to the atmosphere impacts the mine's methane
       emissions.   To estimate  emissions from abandoned vented mines, this methodology
       uses basin-specific decline curves to develop low, mid-range, and high emission factors
       that  are  incorporated into  probability  distributions   for  annual  emissions.  The
       methodology for calculating emissions from vented mines is described in Section 4.6.1.

    •   Flooded mines.  Abandoned mines frequently partially or completely fill with water from
       surrounding strata. The water impedes the escape of the methane in the coal seam,
       effectively  trapping it.   Emissions estimates  for abandoned flooded  mines  are based on
       emission  factors  (low, medium,  and  high) that  are  incorporated into  probability
       distributions  for annual emissions.  The  methodology for  calculating emissions from
       flooded mines is described in Section 4.6.2.

    •   Sealed mines.  The efficiency of the seal  impacts emissions from abandoned sealed
       mines.  Emission  factors are  based on low, mid-range,  and high emission factors for
       each seal type,  which are  incorporated  into  annual  probability distributions.  The
       methodology for calculating emissions from sealed mines is described in Section 4.6.3.

    •   Unknown  mines. To  estimate their  emissions,  abandoned mines  of unknown status
       must be assigned a classification as vented, flooded, or sealed. This apportionment,
       based on  the  proportion  of these types for abandoned  mines  that are known,  is
       described in Section 4.7.1.
       4.2   Forecasting  Abandoned  Mine  Methane  Emissions  Using  Decline
             Curves


The methane emission rate of a mine before abandonment is a function of the gas content of
the coal, the rate of coal mining, and the flow  capacity of the mine.  In this respect,  methane
emissions from active mines are very similar to conventional gas wells, where the initial rate of a
water-free conventional gas well reflects both the gas content of the producing formation and
the productivity index of the well.  Production from conventional gas wells as a function of time
US Environmental Protection Agency                                                       19

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is commonly forecast using decline curve analysis. The physical basis for decline curve analysis
and its application to abandoned mine emission forecasting are described below..

Existing data on abandoned  mine emissions through time, although sparse, appear to fit a
hyperbolic model  of decline.  For example,  USBM measured  daily  emissions at the Cambria
Mine in Pennsylvania18 for over 3 years, including approximately 1.5 years after the gob area
was sealed (Garcia et al., 1994). As shown in Figure 6, a hyperbolic decline equation matches
this set of data with a  correlation coefficient  (R2)  equal  to 0.88,  indicating  a  statistically
significant correlation.

An examination of Equation 3 (page 13) reveals why methane emission rates from  abandoned
mines decline over time. As methane leaves the system, the reservoir pressure, Pr,  declines as
described  by the isotherm. At the same time, both the  mine pressure (Pw ~ 1 atm for vented
mines) and the PI term are  essentially constant at the pressures of interest (atmospheric to 30
psia). Thus, the flowrate q becomes smaller (q is defined as a negative number by convention).

Methane production from abandoned coal mines can be estimated based on the decline curve
(Equation  3) used  in conjunction  with material balances.   Fetkovitch  et al. (1994)  have
generated a rate-time equation that can be used  to predict future  gas  production.  These
authors combined the pseudosteady state flow equation (Equation  3) with a material balance
equation that calculates the pressure loss as material is removed. The resulting expression for
gas production as a function of time clearly shows that gas production declines in a hyperbolic
fashion:

                           q = qi(1 +bDit)M/b)                              (Equation 4)

Where:
             q = the gas rate at time t in mcf/d
             q, = the initial gas rate at time zero (t0) in mcf/d
             b = the hyperbolic exponent, dimensionless
             DJ = the initial decline rate, 1/yr
             t = elapsed time from t0 in years

The coefficients b and DI can be  determined by fitting Equation  4 to measured rate  data.
Unfortunately, historical information on methane emission rates from abandoned mines is very
rare. The only parameters in  Equation 4 that are readily available  from the abandoned  mine
database are the emission rate at the time of abandonment (q,) and the date of abandonment
(t0). The values for the coefficients DI and b must be obtained in other ways. Once determined,
Equation 4 can be used to forecast future gas production.  Several  key parameters that affect
the flow of methane from a mine, including flow capacity, pressure in the coal at abandonment,
and the gas storage as a function of pressure  (represented by the adsorption  isotherm) are
implicitly incorporated into this equation's coefficients.
18 This particular well used a blower to maintain a constant low pressure on the wellhead, which
accelerated gas production but did not affect the hyperbolic nature of the decline curve.


20                                                     US Environmental Protection Agency

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            Figure  5.    Methodology for Calculating Abandoned  Mine  Emissions
                            Select an
                            Inventory
                            Year from
                             AMDB
                                     Select a
                                     Mine for
                                     Analysis
                     /Is mine status"-
                     \   known   x
Select unknown
    status
  spreadsheet
                      Select Basin for
                       Decline Curve
                       Calculations
                     Generate emission
                        probability
                       distribution as
                      flooded, vented
                        and sealed
                      Add to unknown
                        mine status
                        summation
                     Generate unknown
                        mine status
                     emission  inventory
                        probability
                        distribution

                     Determine fraction
                     of each status type
                         by basin
                     Multiply emission
                        inventory
                      distribution by
                      fraction of each
                        status type
Generate factored
 unknown mine
 status emission
    inventory
   probability
   distribution
                                                   Select flooded
                                                  status spreadsheet
                              Generate yearly
                                emissions
                                probability
                                distribution
                              Add to flooded
                             status summation
                               Generate total
                               flooded status
                             emission inventory
                                probability
                                distribution
                                                            Select vented
                                                          status spreadsheet
                                                           Select Basin for
                                                            Decline Curve
                                                             Calculation
                                                          Calculate low, mid
                                                          and high emission
                                                               factors
                                                         Define distribution
                                                          type and assign
                                                              data
                                                          Generate yearly
                                                            emissions
                                                            probability
                                                            distribution
                                                          Add to vented
                                                         status summation
                                                           Generate total
                                                           vented status
                                                          smission inventory
                                                             probability
                                                             distribution
                                                      :ornbine all mine status probabilit^x
                                                      distributions through Monte Carlo
                                                      Simulation to generate probabii
                                                     distribution for the abandoned m
                                                           emission inventory
                                                         no   \
                                                         ity   W
                                                         ine  /
                                                                                       Calculate perm
                                                                                       based low, mid
                                                                                       and high factors  i
                                                                                      for each seal type I
                                                                                      Calculate average
                                                                                       factor for each
                                                                                         seal type
Define distribution
 type and assign
 Generate yearly
   emissions
   probability
   distribution
  Add to sealed
status summation
                                                                                       Generate total
                                                                                       sealed status   I
                                                                                     emission inventory j
                                                                                         probability    j
                                                                                        distribution    j
US Environmental Protection Agency
                                                                                                                          21

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                       Figure 6. Cambria Mine gob well decline curve
       800 i
                            200
   300       400

Days from Abandonment
                                                        500
                                                                 600
700
       4.3   Generating Dimensionless Decline Curves with Flow Simulation


To forecast  methane emissions over time for a given mine, one  must characterize the gas
production of that mine as a function of time (e.g, a decline function), and initiated at the time of
abandonment. To accomplish this,  EPA has  used  a computational fluid dynamics (CFD) flow
simulation model.19

To illustrate  how a decline curve can be built with the CFD simulator, a conceptual model of a
non-flooding, actively venting mine was built. The numerical model was configured such that the
volume of the mined-out areas, or void  volume, was  10% of the model bulk volume.20 The
remaining volume was coal in communication with the void volume. This coal represents both
the coal remaining  in the mined seam and unmined coal seams in communication with the void
volume because of roof and floor fracturing and relaxation.

The  model  was configured  to simulate  a single  component (methane),  single-phase  (gas)
system for a period of 100 years. The model was initialized at  20 psia in the void with the outer
boundaries acting  as barriers to flow. The coal permeability  was set at 1 millidarcy and the
average adsorption isotherm for the Central Appalachian coal  basin was used as the adsorbed
methane storage function. The minimum pressure was limited to one atmosphere.
19  CFD software uses the rate equations of gas  flowing through  a porous media (conservation  of
momentum) with material balance  equations (conservation  of  mass)  in combination with  an initial
pressure and boundary conditions that define the flow geometry.
  The 10% void volume value was based on a proprietary study of several abandoned mine complexes,
which accounted for the volume of coal peripheral to the mine workings.
22
                    US Environmental Protection Agency

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According to the idealized case  in the model, the gas  from the  mine void depletes rapidly,
reducing the methane pressure in the mine, which in turn allows desorption of methane from the
coal.  This methane then migrates to the void  area where it is removed  from the system. In
generating the family of dimensionless emission decline curves, the conceptual model size was
held constant and the methane flow capacity (PI  in Equation 3) was modified  by adjusting the
permeability. Modifications  of this procedure for flooded and sealed mines will be discussed in
following sections.

Figure  7 shows  the  resulting  methane  production decline curve for a non-flooded,  actively
vented mine. This figure is  normalized to the initial emission rate (q/qi), which allows this curve
to be applied to mines  with differing initial emission rates, as long as they  have similar  initial
pressures, permeability and adsorption isotherms. This figure is based on an  isotherm for the
Central  Appalachian basin,  a permeability of 1 md, and an initial pressure of 20 psia.

Figure 7. Dimensionless decline curve for non-flooded, actively venting abandoned mine
                                                     Hyperbolic constant!
                                                    Di = 1.23/yr
                                                    b = 1.76
                               Simulation Rate Normalizec
                               Hyperbolic Fit
                       15
                              30
                                      45
                                             60

                                            Years
                                                    75
                                                           90
                                                                  105
                                                                         120
       4.4    Data Availability and Uncertainty

Generating mine-specific methane production decline curves requires the estimation of several
key parameters
       •  Initial gas emission rate at time t0
       •  The coal's adsorption isotherm
       •  Permeability (a measure of methane flow capacity)
       •  Mine pressure at abandonment
US Environmental Protection Agency
23

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For mines abandoned during or after 1972, two key  data  are generally available: average
methane emissions rate while mine was active, and the date of abandonment. The initial gas
flow rate at time t0 (closure)  can be estimated, by assuming it is approximately equal to the
average methane liberation rate for each mine (ventilation plus drainage) while the mine was
active.21 Methane drainage information is available on a mine-specific basis since 1990.

To estimate mine-specific values for parameters such as coal adsorption isotherm coefficients,
permeability, and pressure at time of abandonment, a probability  distribution  was generated
based on the most likely value and the probable range of values for each parameter. This range
of values  is not meant to  capture extreme values; rather, the probability distribution helps to
select values that represent the highest and lowest quartile. Specifically, values are chosen at
the  ten-percentile and the ninety-percentile of the cumulative probability density function of the
parameter. For example, 0.1,  1.0 and 10.0 md were selected as the low, mid and high values for
permeability. This means that  10% of all coal permeability values are less than 0.1 md, and 90%
are less than 10.0 md. Similarly, 50% of coal permeability values are expected to be above 1.0
md  and 50% are below 1.0 md. Where measured data are lacking, values such  as  permeability
are selected based on expert opinion.

Once the low,  mid-range, and high values are selected, they are applied to a probability density
function, using a Monte Carlo  simulation to combine these distributions as either summations or
products.  This technique combines the statistical distribution of the data by randomly sampling
values from each distribution, performing the mathematical  operation, then repeating the  task
numerous times.   The  Monte  Carlo simulation  provides a rigorous approach to combining
uncertainties expressed as probability distributions, but the calculated results ultimately depend
on the adequacy of the  underlying statistical model.  The uncertainties associated with combining
different probability distributions using Monte Carlo simulations are described in Appendix C.

              4.4.1  Adsorption Isotherms

Masemore et  al.  (1996) compiled numerous adsorption isotherm  parameters  for each  coal
basin. Table 4 lists the number of isotherms available by coal basin. Based on these datasets,
ranges could be determined for the PL and VL parameters of the adsorption isotherms, using the
low, mid and high values from the probability distribution. Average values of these isotherms are
shown in Figure 8.  Figure 9  shows the adsorption isotherms for the Central Appalachian  coal
basin at the  low-pressure range of interest.
              Table 4.  Adsorption isotherms available for each coal basin
Basin
# of Isotherms
Central
Appalachia
11
Illinois
4
Northern
Appalachia
22
Black
Warrior
16
Western
41
21 While the actual emission rate at the time of closure may be somewhat more accurate than average
active mine emissions, these data are generally not available.  Moreover, ventilation rates during a mine's
final closure would represent  the ventilation of only a small part of the  mine where the final work is
conducted, since presumably seals have already been installed throughout the mine workings.
24
US Environmental Protection Agency

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              Figure 8.  Average methane adsorption isotherm for U.S. coal basins
700 -
600 -
500 -
c
o
ซ 400
c
0)
c
2 300 •
in
ra
O
200
100 -


• ** ' *r ^' •-4
*-'"' --X" ^---'•"*"'"'
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f • ' . i
•^ ,x ' ' — *' Central Appalachia j
^ . ^ — '* — Western Basins i
ty^'tS —ป— Illinois I
,'/'' ~*~ 'Northern Appalachia \
t>

100 200 300 400 500
Pressure, psia
 Figure 9.  Methane adsorption as a function of mine pressure for the Central Appalachian Basin
160 -
140 -
120 -
100
c
O
o
(A
60 •
40
20 -





x !
K *
--" I
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-" ' CALow


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5 10 15 20 25 30 35 40 45 50
psia
US Environmental Protection Agency
25

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             4.4.2 Permeability

Coal permeability data are limited. The few data that are available generally come from
borehole injection tests into unmined coal or from analysis of the production profile of coalbed
methane wells. These  data are generally proprietary; therefore, a range of permeability values
was selected based on expert judgment. To ensure a sufficiently broad range for this parameter,
the low and high values for permeability were selected to  be  0.1 and  10.0 millidarcy (md),
respectively with a mid  case value of 1.0 md.

             4.4.3 Pressure at abandonment

Mine pressure could be measured by closing a vent and allowing the void  area to approach
equilibrium  with the pressure  in  the surrounding unmined coal. Unfortunately, no data have
been published on  the pressure within abandoned mines. Proprietary information on  shut-in
pressures measured at some abandoned mines, range from essentially atmospheric up to 27
psia. The impact of barometric pressure on abandoned  mine methane emissions is described
in Appendix D.

For this model, initial pressures of 17, 20, and 30 psia  were used to represent the low, mid-
range, and high values.

             4.4.4 Initial Emissions Rates: Ventilation Air Emissions


Ventilation air methane emissions rates from active mines are used as in indicator of a mine's
initial emission rate at time   of  abandonment.  To calculate these  initial  rates,  EPA used
emissions data from underground ventilation systems from active mines,  obtained from USBM
and MSHA, based  upon averages of  quarterly instantaneous readings.  The MSHA quarterly
readings for ventilation emissions were assigned a probability distribution, which became the
basis for the initial mine emissions rates used in this inventory.

Some errors are inherent in the measured ventilation emissions data.  For example, a degree of
imprecision is  introduced  into  the  readings because the measurements are not continuous.
Mutmansky (2000)  showed that  individual mine emission measurements vary from +10%  to
+20%. Additionally,  the measurement equipment used by MSHA introduced a bias  of +2%  to
+16%, resulting in an average of 10% overestimation of annual methane emissions (Mutmansky
and Wang, 2000). The combination of these two measurements  and calculation methods result
in  the  quarterly  instantaneous  readings  ranging  from  10%  underestimated  to 30%
overestimated.


      4.5    Sensitivity Analysis  for Adsorption  Isotherm,  Permeability, and
             Pressure


A  sensitivity  analysis  was performed to determine if the range  of uncertainty for three
parameters (adsorption isotherm,  represented by VL and PL;  permeability; and  pressure  at
abandonment) is large enough to  significantly affect the emissions inventory. If an individual
parameter does  not have a   significant effect on the  outcome,  the  mid-case value of the
parameter can be used in the  calculations. Conversely, if the sensitivity analysis indicates that
26                                                    US Environmental Protection Agency

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the outcome is significantly affected by the parameter value, then three values of the parameter
(high, medium, and low values) are input into a probability distribution.

Sensitivity  analysis calculations are  presented  in  Appendix  E.   For example,  the  1990
emissions for the Central  Appalachian  basin are much more sensitive to permeability than to
either initial pressure  or the adsorption isotherm. Therefore, inventory calculations,  use only
mid-case values for initial  pressure and the mid-case  basin-specific isotherm,  but include the
range of values for permeability for the probabilistic analysis.


       4.6   Annual Emission Estimations As a  Function of Mine Status


Estimating  emissions  from an  abandoned mine for any given year after its closure  depends
upon the status of the mine: whether it is open to the atmosphere through one or several vents,
flooded, or partially sealed. Approaches for estimating emissions  for each of these types of
mines are described below.

             4.6.1  Venting Mines

Emissions from a vented mine are calculated using Equation 4 (page 19).  Mine-specific values
are input for the known elapsed time since closure, the  average active mine emission  rate, and
three sets of decline constants for each basin (a low, mid and high case). These decline curves
are  based  on the simulated decline curves (see Figure 7) that  were generated using  the
average adsorption isotherm for the coal basin, an initial pressure of 20 psia, and permeability
values of 0.1, 1.0 and 10.0 md.  The calculated emission rates represent the low, mid  and high
values, with the low and high values representing an 80% range of certainty.

The time since  abandonment is perhaps the most important determinant of mine emissions in
the early years after closure because of the rapid rate of emissions decline.

             4.6.2  Flooded Mines

Empirical observations suggest that methane emissions from  flooded mines decline rapidly, and
that the flooding process dominates the other factors affecting methane emissions. In fact, the
very rapid methane emissions decline rate for flooded mines  suggests that their contribution to
long-term methane emissions will be insignificant.

Based  on these considerations, no attempt was made to arrive  at a theoretical model of this
process; rather, this  approach uses  measured  data  to fit a decline curve  equation.   An
exponential equation was developed from emissions data measured at eight abandoned mines,
located in two of the five major U.S. coal basins, known to be filling with  water. Using a least
squares, curve-fitting  algorithm, emissions data were  matched  to this exponential  equation.
There were not  enough data to establish basin-specific  equations, as was done  with the vented
and  non-flooding mines.  The following equation  represents methane emissions from flooded
mines as a function of time:

                          q = qie ('Dt)                                    (Equation 5)

where:
US Environmental Protection Agency                                                        27

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             q = the gas flow rate at time t in mcf/d
             qi = the initial gas flow rate at time zero (t0) in mcf/d
             D = the decline rate, 1/yr
             t = elapsed time from t0 in years

Figure 10  shows the normalized emission rate compared to the initial emission rate as  a
function of time  since abandonment.  The graph  shows  measured  data from  eight flooded
mines, the best-fit curve for those data points (solid  line), and the  95% confidence interval
(dashed lines).

                  Figure 10. Emission model for abandoned flooding mines
50% I
~ 45% -
0)
o
•D
C
*•ป
Emission Rate
•j. ro ro c
T O Ol C
o
c
.2 10% -
o


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1 ป
s I •
1 *
* \ i
* \
s
1





t
1
ซ *
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'*-
v^ซป.^








C~ป-ซ*ปซ™j|









- - Upper Li
-— Best Fit
~ " Lower Li
* Measure





2468
Years Since Abandonment








mit 	 \
d i





10 12 14
             4.6.3  Sealed Mines

Seals have an inhibiting effect on the rate of flow of methane into the atmosphere compared to
open-vented mines. The total volume of methane emitted will be the same, but it will occur over
a longer period.  Accordingly,  this methodology treats the emissions prediction from a sealed
mine in a similar manner to emissions from  a vented mine, but using a lower initial emissions
rate that depends on the degree of sealing. The CFD simulator was again  used with the
conceptual  abandoned mine model to predict the decline curve for inhibited flow. The degree of
sealing, or the percent sealed (Xs), is defined by Equation 6:
                             = 100*(1-qis/qi)
                  (Equation 6)
where:
             qis =   initial emissions from abandoned mine at time t0 (after sealing)
             q, =    emission rate at abandonment prior to sealing
28
US Environmental Protection Agency

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Figure 11 shows a set of decline curves for several cases with different degrees of sealing for a
mine in the Black Warrior Basin.  The emission rates are normalized to the emission rate of the
mine at the time of closure. This graph illustrates how the rate of decline decreases as the
degree of sealing (percent sealed) increases.

Unfortunately, no measurements of diffuse emissions are available to calibrate the sealed mine
emission  rate calculations. Therefore,  the decline curves  shown in  Figure 11 were used to
select the high,  mid-range, and  low values for sealed mine emissions.  As 11 illustrates, the
difference in emission rates between an unsealed mine and a 50% sealed mine is insignificant
after a year of closure. However,  significant differences are seen in the fractional emission rates
between cases for 50%, 80% and 95% closure achieved for sealed mines.  Thus, these values
were selected as the low, mid-range, and high  range values for the  extent of mine sealing,
respectively.

       Figure 11. Emission model for abandoned mines with different degrees of sealing
                 1.00
                                                            •No Seal
                                                            •50% Sealed
                                                            70% Sealed
                                                            80% Sealed
                                                            90% Sealed
                                                            '95% Sealed
                 0.00
                                      10        15        20

                                       Years from Abandonment
                                                                 25
                                                                           30
       4.7    Calculating Annual Methane Emissions

To calculate annual methane emissions from abandoned mines, a spreadsheet workbook was
developed for each inventory year, containing data for 364 gassy mines abandoned since 1972.
These mines are estimated to account for 98% of abandoned mine emissions in those years.
For mines of known condition, the emissions are calculated according to the methods described
previously for  each type (venting, flooded, or sealed). Probability distributions of total  annual
emissions for  each mine are summed to provide yearly emissions classified by mine  status,
which  are  then aggregated  to  determine  total  annual emissions.  Emissions for mines of
unknown status are calculated and incorporated  into the total  annual emissions inventory as
described below. Example calculations for each  type of mine for the year 2000 are shown in
Appendix F.
US Environmental Protection Agency
29

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             4.7.1  Mines of Unknown Status
To calculate emissions for mines whose status is unknown, it was assumed that the population
of these unknown status mines is similar to the population of mines that are known to be sealed,
venting, or flooded. That is, the percentage of sealed, venting, or flooded mines is assumed to
be consistent for all  the  mines in  a given basin.  This  assumption is reasonable because
abandonment practices  such as backfilling shafts and portals are uniform within a given state.
In addition, the hydrogeology and flooding characteristics of mines are similar within most of the
U.S. basins,  although they can vary greatly in Central Appalachia.

Three  probability density  functions  of the total  emissions from these mines are  calculated
assuming that they are  either venting, flooding,  or sealed. The probability density function for
each status  type is then multiplied by the percentage of mines known to be vented, flooded or
sealed within each basin. Table 5 shows the percentage of each  known status type for the year
2000 inventory.

               Table 5. Distribution of (known) types of abandoned  mines
                                     for year 2000
Basin
Central Appalachia
Illinois Basin
Northern Appalachia
Warrior Basin
Western Basins
Sealed %
25%
56%
48%
8%
76%
Venting %
26%
6%
32%
0%
16%
Flooded %
49%
38%
21%
92%
8%
             4.7.2  Combining the known status and unknown status inventories

To arrive at a total abandoned mine emission inventory, the distributions from the known and
unknown status mines are summed using Monte Carlo simulation. The distribution for the total
basin value for the year 2000 inventory is shown in Figure 12. From the distributions for each
basin, a probability table can be constructed, as shown in Table 6. The emission distributions of
the individual basins were  added  together  using  Monte  Carlo simulation  to  produce the
probability distribution for the combined basins.22  Table 7 converts the emissions inventory for
all abandoned mines in the U.S. from units of cubic feet of methane to metric tons  of carbon
dioxide equivalent (CO2e).
22 The mean of the total basin distribution will equal the sum of the mean of the basin distributions. The
probability of the 2.5% values of all basins occurring is 0.0255 = 1.0E-08, which is why the 2.5% value of
the total distribution is greater than the sum of the 2.5% values of each basin. Accordingly, the 97.5%
value of the total distribution is less than the sum of the 97.5% values of each zone.
30
US Environmental Protection Agency

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   Figure 12. Year 2000 emissions inventory: Total methane emissions from abandoned mines

                          Distribution for All Basins for Year 2000
           o

           o>
           D
           cr
           o>
                                10.0      11.0      12.0


                                        Values (Bcf)
                                                          13.0
                                                                   14.0
                                                                           15.0
               Table 6.  Year 2000  abandoned mine emissions by coal basin, Bcf
Basin
Central Appalachia
Illinois Basin
Northern Appalachia
Warrior Basin
Western Basins
Total
2.5%
Probability
3.2
0.70
2.2
0.27
1.3
9.3
50%
Probability
4.5
1.0
2.7
0.94
1.8
11.1
97.5%
Probability
5.8
1.4
3.2
1.8
2.5
12.8
Mean
4.5
1.0
2.7
0.97
1.9
11.0
           Table 7. Year 2000 Abandoned Mine Methane Emissions, Tonnes of CO2e
Basin
Central Appalachia
Illinois Basin
Northern Appalachia
Warrior Basin
Western Basins
Total
2.5%
Probability
1,297,075
283,434
872,747
110,154
530,668
3,748,640
50%
Probability
1,810,396
407,555
1,087,689
376,608
745,404
4,456,451
97.5%
Probability
2,339,099
575,287
1,297,761
723,240
1,008,743
5,139,777
Mean
1,813,577
414,150
1,087,483
390,591
751,990
4,457,789
US Environmental Protection Agency
31

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5.0    Calibration through Field Measurements

In developing abandoned mine emission estimates, field  measurements serve two  important
roles. First, they provide empirical data for model inputs. One of the keys to estimating methane
emissions from  an abandoned mine is determining the  average methane emissions  rate from
the mine  in order to project future  emissions rates. The field measurement  program was
designed to determine the measurement interval and duration necessary to accurately calculate
an average  methane emission rate  from  a mine vent.  Second, field  measurements verify
whether theoretical calculations serve as a  reliable proxy for real outcomes or events.  In this
case, field measurements tested the accuracy of the mathematical decline  curves used  for
basin-specific emissions estimates.

Previously, EPA's Office of Research  and  Development (ORD)  initiated  a field  research
program in the early 1990s (Kirchgessner, et al., 2001), collecting data for 21 abandoned mines
located throughout the  Northern and  Central  Appalachian, Black  Warrior, and Illinois  basins.
Seven of the mines that produced no methane were documented to be at  least partially flooded.
Of the 14 mines that were producing methane, seven  were also  documented to be at  least
partially flooded. This study was limited by the  fact that only single or one-day measurements at
each  borehole or  vent  pipe were recorded, and the results were not  normalized for average
barometric pressure.

For the present  study, EPA conducted a series of field measurements at  abandoned mine vent
locations  across  the U.S.,  with the goal of measuring actual methane  emissions  at a
representative sample of  mines with vent  pipes.  Vent pipes are the only feasible sites at an
abandoned mine to accurately measure methane emissions.  Of the 393 abandoned mines in
the database, 55  (14%) are known to have  vent pipes still  in place.   Unfortunately, limited
access to the mines  precluded measurement of  all but seven mines.23   Two of these seven
mines were nearly flooded at the time of the study and  produced little methane.


       5.1   Field Measurement Methodology


Between  November 1998 and February 2000, EPA recorded measurements at five unflooded
abandoned mines to which  the agency  had  access. Measurements were recorded  at two
abandoned mines  located in Ohio and Virginia continuously for 6-12 hours. EPA also measured
three additional  mines located in Illinois and Colorado, recording measurements hourly for 3-4
days, normalizing them to  average barometric pressures.

At the five abandoned mines where measurements were conducted, vane anemometers24 and
methane  detectors were  used to determine gas flow rates and concentrations,  respectively.
Several  correction  factors  are  necessary  to   convert  anemometer  flow and  methane
concentration measurements to standard methane emission values, to account for the blocking
factor of the vanes and provide an empirical correction  for the velocity profile.25
23 EPA contacted mine operators and landowners that controlled over 50 of the candidate abandoned
mines, but attained access to only seven mines.
24 An anemometer measures the velocity of gas flow through a shaft or vent pipe of a known cross-
sectional area.
25 USBM conducted a series of measurements for pipes smaller than 12 inches in diameter (Garcia, et al.,
1987). Based on their work, method factors for 4-, 6-, and 8-inch diameter pipes are 0.68, 0.71 and 0.78,


32                                                    US Environmental Protection Agency

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Corrections are also necessary for reporting gas emissions  under standard temperature and
pressure (STP) conditions. However,  because elevation and temperature conditions  at most
mines do not vary greatly, these corrections are generally insignificant. According to the USBM
study, the  effects of density  changes due to  methane  concentrations using anemometers
calibrated in air are miniscule.

As part of this study, EPA monitored the effects of barometric pressure on mine venting, since
atmospheric pressure can impact the rate of methane release from abandoned  mines.  Results
of these measurements are shown in Appendix F.


       5.2     Compilation of Data


Figure  13  shows  EPA's measurements of abandoned mine methane  emissions field data
collected during  the  two studies (1991-2000).   The emission rate  decline  curves are shown
separately  for each  coal basin, with  the dashed lines indicating  the 10  and 90 percentile
emission predictions.  The solid lines indicate the  50% emission predictions. As these graphs
illustrate, emission rates from  nine of  the ten abandoned  mines that were measured fall very
close to the predicted mid-case decline rate for their respective basins.

Of the seven flooded mines with  no  methane  emissions  investigated, five mines had been
abandoned for less than 10 years, while  the remaining two had been abandoned for  over 15
years. Of the nine flooded mines that produced  methane emissions,  six (67%) fell within a 95%
predictive confidence interval of the exponential  equation defined in Equation 5 (also shown in
Figure  10).  These data suggest that most U.S.  mines prone to flooding will  become mostly
flooded within 8 years and after 14 years no longer have any measurable methane emissions.
Based on this assumption and  until additional data can be collected, this methodology  uses an
average U.S. decline rate for all flooding mines.
respectively. The National Coal Board of the United Kingdom had previously developed method factors
for correcting vane anemometer measurements for 12  to 30 inch diameter pipes (Northover, 1957).
Furthermore, results indicated that for pipes larger than 12 inches in diameter, a method factor of 0.85 is
sufficient for conversion purposes.


US Environmental Protection Agency                                                        33

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      Figure 13. Vented emissions from unflooded, abandoned mines in U.S. coal basins
Ce
0.90 -
0.80 -
a, 0.70 -
ft nfin .
.2
| 0.40
O
'•5 0.30 -
CO
"• 0.20
0.10 --
0.90
0.80
a, 0.70
"TO
"• 0.60
.5
ฐ 0.40
0
'o 0.30
"• 0.20
0.10
ntral Appalachian Basin Decline Curves for Active Vents
	 ~ 	 : 0.90 "
0.80 -
• " 'High 7j
— Mid - 0-60 '
- ~_ .- 	 " • • Low 	 5 .. n
A Measured ป.
ฐ 0.40
' •--.., 1 a3ฐ"
v A """*""•- — ..ป "• 0.20 -
	 ' 	 ' 	 r 	
1 15 20 25 30
Years
Black Wamor Basin Decline Curves for Active Vents
	 0.90
- ' 0.80
" v 'High „
— Mid ฃ
A Measured ?
— 0.40
. 'o
- ' _ ง 0.30
' \ """""*"••-•--.,„, % 0.20
...,,„ 	 „,,.„.„ """"" "•
" 	 I 	
^ — • ' o.oo
15 20 25 30
Years
Western Basins Decline Curves
0.90 - - 	
0.80
0) 0.70 -
"ro '•
Illinois Basin Decline Curves for Active Vents

* i ~ " 'High
^ ! Mid
\ " " 'Low
ป\ ^*x •ซ
5 10 15 20 25 30
Years
Northern Appalachian Basin Decline Curves for Active Vents
s I , 	 1 	 1
" " High
A —Mid
^ " " Low
* Measured
'
\
* \. " V ^ ' ซ. ^ ' ...
5 10 15 20 25 30
Years
for Active Vents
	 i 	
• - 'High
~n \. Mid
ฐ 0.40 - ' - ;
O ::
'o 0.30 - :. ' " - „ i
2 ป •• ' " " v v
"• 0.20 ^ \ ' • ,., """•••[-ซ.,.
A Measured

ฐ-10 • ••- 	 -Tj— — " ซ_ __^™__..
5 10 15 20 25 30
Years
34
US Environmental Protection Agency

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6.0   Estimating Emissions from Mines Closed Before 1972

 For mines abandoned in or after 1972, data  are readily available, including comprehensive
 active mine emissions data, date of abandonment, number of gassy mines, mine status, and
 even coal production on a state and county basis. In contrast, most of the information needed
 to calculate emissions from abandoned mines  is largely unknown for mines closed before
 1972.

 Emissions from the pre-1972  mines may be  characterized using the  dimensionless decline
 curves described in this report. Key data needed to  use  a modified version of the post-1971
 methodology for the pre-1972 mines include the number of suspected gassy mine closures, the
 dates of closure, and the emissions rate at closure. For this report, EPA makes the reasonable
 assumption that pre-1972 mines are governed by the same physical, geologic and hydrologic
 constraints that apply to 1971, 1973, and 1975 coal mine datasets. The major reason for this is
 that most mining methods at that time were still room and pillar mining.

 To  extrapolate  emissions  estimates for  mines abandoned  before  1972,  EPA compiled
 information from several  USBM studies (1971,  1973, and 1975). In addition, EPA obtained
 statewide mine closure dates for Colorado and Illinois throughout the 20th century, and used
 this information for  establishing  national  trends.   EPA determined  that  most coal mine
 emissions in the U.S. originate in relatively small geographic areas. For example, during the
 1970s, nearly 80% of CMM emissions came from seventeen counties in seven states.

 Based  on these data,  EPA applied basin-specific decline curve equations to 145 gassy coal
 mines estimated to have  closed between 1920 and 1971  in the U.S, representing 78% of the
 active mine emissions during that time.  Mines abandoned before 1972 are estimated to have
 contributed 1.7 Bcf methane emissions to the 1990 abandoned mine emissions inventory.


       6.1    Historical  Trends in Gassy Mine Emissions


 The gassy mine population in the U.S. is geographically limited to specific coal seams within a
 few coal basins. The population of gassy mines (those with emissions >100 mcfd) in the U.S.
 has remained  stable since  1971,  numbering between  100-200 mines. Based  on  several
 historical observations, it is reasonable  to assume that there were fewer gassy mines during
 the early days of mining:

       1)  Historic trends  in mine size indicate exponential growth in recent years. A USBM
          study has shown that the average mine size in 1985 was one  half of those in  1995.
          Thus,  extrapolating backward from  this trend suggests that  pre-1972  mine  sizes
          would be much  smaller than those in  1985 would.

       2)  Many of the gassy mines  closed after 1972 had operated since early in the 20th
          century, particularly in the Pittsburgh coal seam, where the largest concentration of
          gassy mines  in the U.S. is located.

       3)  Coal mines  operating in coal seams  at depths up to 2000 feet in Virginia  (e.g.,
          Pocahontas #3) and Alabama  (Mary Lee), which produced a significant portion of the
          U.S. emissions  in the 1970s, and even today, only began operating in the 1940s.
US Environmental Protection Agency                                                       35

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       4)  Prior to the 1970's, all underground mining in the U.S. was through room and pillar
          operations.  Longwall production, associated with  high  gas production, was  not
          introduced widely until the 1970s.  These historic production trends created smaller
          mine voids that exposed less coal and other gassy strata, therefore probably emitting
          less gas.

       5)  Historical records indicate that prior to 1920, there were far fewer gassy coal mines
          (by current standards) operating at only a fraction of the production rates practiced
          after 1920.

EPA estimates that emissions from mines closed before 1920 would emit less than 0.1 Bcf of
methane during 1990, making it an insignificant contribution to the  1990 emissions inventory
baseline. Thus, EPA's estimate of abandoned mine emissions in this inventory is based only on
mines that were closed since 1920.
       6.2    Estimating the Locations of Gassy Mines Abandoned Before 1972
 The geographic distribution of active mine methane emissions during the 1970s is assumed to
 represent emissions from mines abandoned prior to 1972. The  primary justification for this
 assumption is that the room and pillar mining methods used in 1971 were similar to those used
 in previous decades.

 The oldest, most comprehensive dataset of underground coal mine emissions that EPA has
 found is a 1972 USBM Circular listing emissions for all  mines in the U.S. (>100 mcfd) during
 1971 (Irani, 1972). Emissions from these coal mines originated in 64 counties located in eleven
 states. Of these, the nine states shown in Figure 14 made up 95 - 99% of the total methane
 emissions from active coal mines in 1971.

         Figure 14. Active Coal Mine Methane Emissions from Nine States, 1971 - 1980
                                                                 BKENTUCKY

                                                                 • OHIO

                                                                 DUTAH

                                                                 DCOLO

                                                                 m ALABAMA

                                                                 • ILLINOIS

                                                                 • VIRGINIA

                                                                 PPENN

                                                                 DSO W VIR

                                                                 Q NO W VIR
36
US Environmental Protection Agency

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 Seven states  (Pennsylvania, West Virginia, Virginia, Alabama, Illinois,  Colorado, and Utah)
 produced over 90% of the total U.S. active mine emissions from 1971-1980.

 •  The Northern Appalachian basin states were  by  far the largest  contributors during  the
    1970s, emitting  approximately 50% of all U.S. emissions. Pennsylvania and northern West
    Virginia are the principal representatives of the Northern Appalachian basin. ,26

 •  Central Appalachian Basin states contributed approximately 25% of U.S. mining emissions
    during the  1970s.  Southern West Virginia and Virginia are the principal contributors.27

 •  The  next  highest group  of producing  states, Illinois, Alabama, and  Colorado,  each
    contributed significantly to the U.S. total mining emissions.

 •  Utah and Colorado represent the Western Basins.

U.S. coal mine  emissions are even more concentrated than these numbers suggest. 78% of all
U.S. coal mine emissions originated from only 17 counties within seven states. Other counties
each  accounted for  less than 1% of the national emissions. Because of the relatively high
uncertainty associated with the  pre-1972 data, identifying more mines would  only reduce  the
uncertainty incrementally.  Therefore, EPA used these 17 counties as a representative sample
of coal mines in all five major U.S. coal  basins that  constituted the majority of coal production
from  gassy underground  mines.   Emissions from  these 17 counties have  been scaled to
account for emissions from all U.S. mines.28

EPA  compiled  a list of 145 (suspected) gassy mines  located in these 17 counties  that  had
closed prior to  1972.  Table 8 lists the counties and the number of mines estimated to be in
each  county.29
26 Emissions from abandoned mines in Ohio constitute 2% of the total emissions from this basin and are
considered negligible in comparison.
27 Kentucky mine emissions were only 2% of total emissions; Kentucky's emissions are divided between
the Central Appalachian and Illinois Basins. Kentucky was therefore considered negligible in comparison.
28 Since these mines represent 78% of the total emissions, they are multiplied by a scaling factor of 1.22
to account for all U.S. emissions.
29 In Colorado, Utah,  Illinois, Virginia, and Alabama, EPA obtained the information directly from state
agencies or from old state publications.  In fact, Colorado and Illinois had databases that included mine
closure dates since the  late  1800s. For  Pennsylvania and West Virginia, the number of mines was
estimated using maps showing all the mines that had once operated.


US Environmental Protection Agency                                                         37

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                  Table 8. Gassy Abandoned Mines Located in 17 Counties
County
Franklin
Pitkin
Buchanan
Raleigh
McDowell
Cambria
Jefferson
Washington
Indiana
Las Animas
Marion
Marshall
Carbon
Monongalia
Greene
Tuscaloosa
Jefferson
TOTAL
State Number of Mines
IL
CO
VA
WV
WV
PA
AL
PA
PA
CO
WV
WV
UT
WV
PA
AL
IL

23
18
17
15
12
12
9
9
7
7
4
3
3
2
2
1
1
145
       6.3   Estimating Date of Abandonment for Pre-1972 Mines


 EPA was able to estimate the date of abandonment for mines closed prior to 1972 based on
 extrapolation from historical  records of gassy mine closures.  While researching historical coal
 mine information at the  state level,  EPA found  that the  states of Illinois and  Colorado had
 compiled historical coal mine opening and closure dates for each county dating back to the late
 1800s. From these data, a histogram was developed of Illinois and Colorado mine closures in
 counties  known to have gassy mines.   This  subset of  mines represents  34%  of  the total
 number of pre-1972, gassy mines and 30% of the total abandoned mine emissions.

 As Figure 15 illustrates,  mine closures in the two states show consistent patterns since 1910,
 including an increased number of mine closures following World Wars  I and II.  Based on a
 reasonable assumption that mine closures  in these two states followed national trends, EPA
 used the average to estimate the approximate  closure  dates  (decade) for mines  in  all 17
 counties. The mid-decade date (e.g. 6/30/1925) was selected as the nominal "closure date" for
 mines closed in a given decade.30
30 This selection of mid-decadal closure has a minimal impact on the estimated emissions rate.  For
example, the incremental change in emission rates caused by adjusting the nominal closure date by up to
4 years will be less than 1% because of the extended time since abandonment (e.g., 20 to 70 years for
the 1990 emissions inventory).
38
US Environmental Protection Agency

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                 Figure 15. Mine Closures in Colorado and Illinois, 1910 - 1960
       30% T
                                   B Illinois Mine Closures
                                   il Colorado Mine Closures
                                   H Average
               1910s
                          1920s
1930s       1940s
     Decade
1950s
1960s
       6.4 Estimating Initial Emission Rates for Pre-1972 Mines


 Once the  number  of abandoned mines and  their approximate  closure  dates have been
 established, the next  step  is to determine  the  mine's  initial  emission rate  at the  time of
 abandonment.

 EPA conducted a statistical analysis of all the  active mine emissions originating in the 17
 counties for the years 1971,  1973, and 1975, based on data from the USBM circulars.  The
 data were aggregated to the state level in order to use larger samples of mine data.31  Table 9
 summarizes the distributions for the seven states.

 There were three key steps in determining the distribution of initial methane emission rates:

     1)  100 mcfd was defined as the minimum emissions rate.

     2)  The maximum emission rate for each state was based on the USBM data sets.

     3)  Distribution functions were fitted to the datasets to calculate the probability distribution
        of the statewide emission inventory.  In most cases, the best fit was either a log-normal
        or  an  inverse Gaussian distribution; however, in some cases other distributions were
        found  to be  better fits. Figure 16 illustrates a function that was fitted to the  northern
        West Virginia dataset using a "log-logistic" distribution.
31
  West Virginia was divided into two "states" because its mines occur in two coal basins.
US Environmental Protection Agency
                                                   39

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       Table 9. Distributions of Methane Emissions from USBM Datasets from 1971-1975
STATE
Minimum Emission
Rate (mmcfd)
Mean of Data
Distribution (mmcfd)
Maximum Emission
Rate (mmcfd)
AL
0.1
1.0
6.1
VA
0.1
1.1
8.5
swv
0.1
0.6
5.0
UT
0.1
0.4
1.9
CO
0.1
1.0
3.5
IL
0.1
0.7
2.4
PA
0.1
1.0
6.0
NWV
0.1
2.6
12.2
             Figure 16. Active mine emissions for northern West Virginia
                  040 -r
                  035 --
                               2    4    6     8    10

                               Methane Emissions, mmcf/d
                                                      12
                                                           14
       6.5  Calculating Total  Abandoned  Mine  Methane  Emissions  for  Mines
           Closed Prior to 1972


 The initial emission rate distributions for mines in these gassy counties were used as inputs for
 the  post-1972 basin-specific decline  equations. Emissions for each  inventory year were
 calculated  for mines  closed during each of the five decades (1920s through 1960s) and then
 summed  Because it is unknown whether the mines are sealed or venting, a  conservative
 approach assumes that the mines could still be venting.
 Based upon the presumed similarity of hydrologic conditions for mines abandoned before  and
 after 1972, a basin-specific factor was used to account for flooding.  All mines abandoned prior
 to  1972 that  had flooded would have been  closed for at least 19  years  by 1990  and,
 presumably, would have completely flooded out by then. To derive a net, or relative, emissions
 number, emissions were reduced by the percentage of flooding  mines  in each of the basins
 (summarized in Table 3).
40
US Environmental Protection Agency

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 Table 10 shows the emissions contribution for all mines closed in each decade to the  1990
 inventory of total abandoned mine emissions.
    Table 10. Contribution of mines closed from 1920-1969 (by decade) to the 1990 inventory

Decade of mine closure
Mine methane emissions in
1990 (Bcf)
Relative contribution of pre-
1970 closures to 1990
emissions inventory

1920s
0.258
15.1%


1930s
0.277
16.2%


1940s
0.279
16.3%


1950s
0.611
35.7%


1960s
0.286
16.7%

Total
emissions
from
mines
closed,
1920-1969
1.712
100.0%

 The annual emissions  inventory totals for 1990 - 2002 calculated  in this report (Section 7)
 include  emissions from  the 145  mines  abandoned  prior to 1972.  The  pre-1972  mines
 contributed 1.7 Bcf (0.7 million tonnes CO2e) to the  1990 emissions inventory (20%  of the
 total), and declined to 1.4 Bcf (0.6 million  tonnes CO2e) by the year 2000 (10% of the total).
 Figure 17 shows the emissions contribution for each coal basin from  mines abandoned prior to
 1972 for the  1990-2002  inventories  The range of uncertainty associated with the  pre-1972
 emissions analysis is discussed in Section 7.4.
            Figure 17. Emissions contribution from mines abandoned prior to 1972

                                to the 1990-2002 inventories
            1.80 -,
            1.60
            1.40
          2.
          in
          c
          o
            1.20 -
            0.80 - -
           a 0.60 - —
            0.00
                1990 1991 1992 1993  1994  1995  1996  1997  1998 1999 2000 2001 2002
US Environmental Protection Agency
41

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7.0    Results of the 1990 - 2002 Abandoned Mine Methane Emissions
       Inventory


       7.1    1990 Baseline Inventory


For the 1990 baseline year, the abandoned mines emissions inventory was based on emissions
from 145 suspected gassy mines that closed from 1920 - 1971 (estimated as described in the
previous section) as well as 249 mines closed after 1972 that are known to have active mine
methane ventilation emission rates greater than 100 mcfd at the time of abandonment.

As described previously, EPA used estimated initial emission rates (based on MSHA reports for
post-1972 mines), time of abandonment, and  basin-specific decline curves to calculate annual
emissions for each mine in the database. Because coal mine degasification data is not available
for years prior to 1990, the estimated initial emission rates reflect ventilation emissions only.

The gassy mines for which emissions were calculated are assumed to account for 98% of total
national emissions.  Therefore, to account for total post-1971 abandoned mine emissions, this
estimate was multiplied by 1.02. EPA estimates that 1990 methane emissions from post-1971
U.S.  abandoned coal mines range from 5.6 to 7.9 Bcf (2.3 to 3.2 million tonnes CO2e), with a
median value of 6.6 Bcf (2.7 million tonnes CO2e) at the 95% confidence level.


       7.2    Emissions for 1991 -2002


To determine the post-1971  abandoned mine emissions for  1991 through 2002,  EPA used
several sources  of  information.  Using MSHA data  and  EPA  annual  coal mine emissions
inventory data,  EPA identified  and calculated the ventilation emissions and degasification
volumes from 144 mines that were closed from 1991-2002 (Figure 18).32  Table 11 shows the
number of gassy mines closed each year by coal basin.

For nearly all mines closed between  1990 and 2002, the initial methane emission rate at time of
abandonment reflects ventilation emissions only. However, for 14 mines that  closed between
1992 and 2002, degasification data  were available, so the initial emissions rate  for these 14
mines includes the total methane liberation rate (ventilation plus degasification).
Table 11. Cumulative Number of Gassy Coal Mines Abandoned Annualh
Coal Basin
Central Appalachian
Illinois Basin
Northern Appalachian
Black Warrior
Western U.S.
U. S. Total
1990
105
35
60
9
21
230
1991
108
37
64
9
22
240
1992
114
38
68
9
23
252
1993
119
40
74
10
23 .
266
1994
131
44
80
10
23
288
1995
143
47
82
10
25
306
1996
157
53
94
11
27
342
1997
162
56
97
12
28
355
1998
164
59
97
13
30
363
1999
166
59
97
14
31
367
/, 1990-2002
2000
168
61
98
14
33
374
2001
176
62
99
14
35
386
2002
180
64
100
14
35
393
32 An additional 17 mines  closed from 1991-2002, but they were reopened for coal mining activity.
Emissions from these mines were never added to the abandoned mine database.
42
US Environmental Protection Agency

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                Figure  18. Gassy Coal Mines Abandoned Annually (1990-2002)
                                                                    -T 450
                                                    ป Total Number of Mines
                                                      in Database
                  1990 1991  1992  1993  1994  1995  1996  1997  1998  1999 2000 2001 2002

                                          Year
       7.3    Inventory Adjustments for 1990 - 2002 Methane Recovery Projects
Once the total methane emissions for 1990 - 2002 were calculated, they were adjusted to reflect
abandoned  mine methane emissions that are recovered and used. No known or reported
abandoned mine methane recovery projects were in operation from 1990 - 1992, and therefore
emissions inventories for these years have not been adjusted.

Conceptually,  estimating   annual emissions  for  abandoned mines with recovery projects
consists of two  key steps: (1) calculating  the  estimated emission rate without  the recovery
project, and  (2) subtracting the project-specific emissions  estimate  for individual  mines as
appropriate.33  The total annual "avoided" emissions are determined  by subtracting the  total
project-specific emissions from the annual total that was  calculated assuming no recovery
projects.

Table 12 shows the number of abandoned mine methane recovery projects that were operating
from 1990-2002, and the emissions avoided as a consequence of those projects. It is important
to note that the emissions avoided values do not represent the amount  of gas produced from
each project, but rather  the amount of emissions that would have occurred had the project not
been in place. Recovery projects often rely on blowers and other equipment that may pull more
methane out of the mine than likely would be vented naturally.34 Therefore, some of the CMM
captured at an abandoned mine recovery project is not always considered an avoided emission.
33
  In actuality, the emissions avoided were integrated as part of the Monte Carlo simulation, rather than
subtracted at the end of the calculation.
34 For this analysis, it is assumed that the negative pressure applied to the mine void to facilitate methane
recovery would negate any additional diffuse emissions from the mine.
US Environmental Protection Agency
43

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Furthermore,  EPA assumes that the projects produce  gas equal  to  or  greater than  the
emissions avoided value; therefore, the presence of the project reduces the mine emissions to
zero.35

                   Table 12. Abandoned Mine Methane Recovery Projects

# of Recovery Projects
Emissions Avoided (mmcf)
1990
0
0
1991
0
0
1992
0
0
1993
1
34
1994
2
190
1995
3
779
1996
4
1,214
1997
11
2,899
1998
13
3,244
1999
14
2,975
2000
15
2,587
2001
17
2,487
2002
21
2,625
             7.3.1  Summary of U.S. Emissions

Figure 19 shows that gross abandoned mine emissions ranged from 8.4 to 16.8 Bcf during the
decade, varying by as much as 2 Bcf from year to year. Fluctuations were due to the number of
mines closed during a given year as well as the magnitude of the emissions from those mines
when active. Abandoned mine emissions peaked in 1996 due to the large number of mine
closures from 1994 to 1996 (76 gassy mines closed during this three-year period). Abandoned
mine emissions have declined since  1996, due primarily to the decreased number of closures;
fewer than twelve gassy mine closures occurred during each of the years from 1998-2002. The
abandoned mine emissions estimate for the year 2002 had  declined to 12.9 Bcf  (5.2 million
tonnes CO2e, excluding recovery projects),  compared to a peak of nearly 16.7 Bcf (6.7 million
tonnes CO2e) in 1996. Figure 20 shows the net emissions in units of CO2e and Gg of methane.

Table 13 summarizes the abandoned coal mine emissions for each basin from  1990 to 2002.
The  majority of abandoned mine emissions originate from mines located in the Central and
Northern Appalachian basins. On average, mines abandoned in these two basins make up 72%
of the mines in the database and between 65-75% of the U.S. abandoned mine emissions.

Figure 21  shows that the Central Appalachian basin is by far the largest contributor to the post-
1971  abandoned  mines emission inventory.   Interestingly, the  overall  ranking of the  basins
differed only slightly up  until 1997, but since that time emissions contributions from  the Central
and Northern Appalachian basins have declined, while emissions from the Western and Warrior
basins have risen. This change reflects the geographical shift in U.S. coal production away from
the Appalachian basin.
35 The only exception known is the Blue Creek Mine project, which was an active mine project until 1999.
It produced only 0.2bcf in 2002, but the emissions avoided potential was 0.6 Bcf. The reason is that, for
now, the recovery project is simply a continuation of the small number of active mine gas wells that were
operating prior to closure.
44
US Environmental Protection Agency

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           Figure 19. Abandoned Mine Methane Emissions Estimate for 1990-2002
18.0 -

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M Emission Avoided
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1990 1991 1992 1993 1994 1995 1996 1997 1998 1999 2000 2001 2002
            Figure 20. Net Abandoned Mine Emissions (CO2e and Gg Methane)
7 0 -

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40

US Environmental Protection Agency
45

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         Table 13. Summary of Abandoned Coal Mine Emissions by Basin (Bcf/yr)

Central Appalachian
Basin
Illinois Basin
Northern
Appalachian Basin
Warrior Basin
Western Basins
U. S. Total
Methane Liberated
Emissions Avoided
Net Emissions (Bcf)
Methane Liberated
Emissions Avoided
Net Emissions (Bcf)
Methane Liberated
Emissions Avoided
Net Emissions (Bcf)
Methane Liberated
Emissions Avoided
Net Emissions (Bcf)
Methane Liberated
Emissions Avoided
Net Emissions (Bcf)
Methane Liberated
Emissions Avoided
Net Emissions (Bcf)
1990
3.12
0.00
3.12
0.71
0.00
0.71
3.09
0.00
3.09
0.19
0.00
0.19
1.34
0.00
1.34
8.44
0.00
8.44
1991
3.51
0.00
3.51
0.70
0.00
0.70
2.85
0.00
2.85
0.11
0.00
0.11
1.35
0.00
1.35
8.53
0.00
8.53
1992
4.23
0.00
4.23
0.99
0.00
0.99
2.83
0.00
2.83
0.07
0.00
0.07
1.40
0.00
1.40
9.53
0.00
9.53
1993
4.57
0.00
4.57
0.93
0.00
0.93
3.63
0.03
3.59
0.05 .
0.00
0.05
1.56
0.00
1.56
10.74
0.03
10.71
1994
5.17
0.16
5.01
1.12
0.00
1.12
3.63
0.03
3.59
0.03
0.00
0.03
1.50
0.00
1.50
11.46
0.19
11.27
199S
6.17
0.75
5.42
1.27
0.00
1.27
4.43
0.03
4.40
0.06
0.00
0.06
1.48
0.00
1.48
13.40
0.78
12.62
1996
7.06
0.63
6.43
1.69
0.00
1.69
^5.34
0.59
4.75
0.14
0.00
0.14
1.77
0.00
1.77
15.99
1.21
14.78
1997
6.87
0.96
5.91
1.81
0.00
1.81
5.79
1.47
4.32
0.38
0.00
0.38
1.90
0.47
1.44
16.75
2.90
13.85
1998
6.47
1.49
4.98
1.63
0.06
1.57
4.53
1.30
3.23
0.49
0.00
0.49
2.17
0.40
1.77
15.28
3.24
12.04
1999
5.81
1.27
4.54
1.46
0.05
1.41
3.82
1.31
2.51
0.77
0.00
0.77
2.13
0.35
1.78
13.98
2.97
11.00
2000
5.21
1.02
4.19
1.30
0.04
1.25
3.41
1.18
2.22
1.17
0.02
1.15
2.51
0.32
2.19
13.59
2.59
11.00
2001
5.05
0.95
4.11
1.29
0.04
1.24
3.37
1.08
2.28
0.89
0.12
0.77
2.32
0.29
2.03
12.93
2.49
10.44
2002
5.08
0.89
4.19
1.51
0.26
1.25
3.28
1.00
2.28
0.77
0.20
0.57
2.21
0.27
1.94
12.86
2.62
10.23
        Figure  21. Abandoned Coal Mine Emissions from U.S. Coal Basins, 1990 - 2002


w
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31
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-*- Central Appl
-ป-•• Northern Appl x "'-•*••• — * 	 *
•••ป••• Western Basins
-•-Warrior Basin
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~* ' — * 	 <&..., — ifc 	 .* 	 *
89 1990 1991 1992 1993 1994 1995 1996 1997 1998 1999 2000 2001 2002 2003
Year
       7.4    Key Assumptions and Areas of Uncertainty

Uncertainties  in  the emission  inventory  results from  data  gaps, methodology,  and  key
assumptions made in developing an  estimate of abandoned  mine emissions.   This section
identifies and attempts to quantify these uncertainties.

Four important areas of uncertainty  described in this report could significantly impact the
emissions inventory calculations:
46
US Environmental Protection Agency

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    1)  Limited data on mines closed before 1972
    2)  Biases in U.S. mine ventilation data
    3)  Lack of data on mine drainage before 1990
    4)  Exclusion of surface mine emissions.

Each of these key areas of uncertainty is discussed briefly below.

             7.4.1 Limited data on mines abandoned before 1972

The limitations on data available for mines abandoned prior to 1972 have been dealt with in this
emissions inventory using the methodology described in Section 6.

             7.4.2 Biases in U.S. mine ventilation data

U.S. mine  ventilation data, as received from MSHA, has inherent limitations because  it  is
reported in broad classification ranges.  In addition,  research  has suggested  that the MSHA
data is inherently biased to overestimate ventilation emissions, with estimated error of +30%  to
- 10% (Mutmansky and Wang 2000).

             7.4.3 Lack of data on degasification prior to 1990

Comprehensive data on degasification systems prior to 1990 are  not  available.  Therefore,
EPA's estimates of pre-1990 mine methane emissions includes only mine ventilation emissions.
For  mines  closed since  1990,   EPA  compiled  estimates  of methane  liberated  using
degasification systems in addition to  ventilation. For mines using degasification  systems for
which no data are available, EPA assigned default recovery  efficiencies.

Because methane liberated from degasification systems prior to 1990 was not incorporated  in
this inventory, the total active mine emissions estimate used from 1972-1989 for this inventory
may be underestimated by approximately 6.5%.  This figure is based on USBM's  estimate for
1973, that  total coal mine ventilation  emissions accounted for 93.5%  of the total methane
liberated from U.S. coal mines (Irani, et al, 1974).

However, the overall impact on the emissions  inventory of not accounting  for degasification
systems may be  less than 6.5%,  since  many of the mines are suspected  to be flooded or
sealed,  which would dramatically decrease their emissions.  Abandoned mine  emissions rapidly
decline  during the early years after abandonment,  further mitigating the impact of  potential
marginal increases in the initial emissions rate.

             7.4.4 Exclusion of surface mine emissions

Surface mines are included in the  U.S. inventory of active  coal mine methane emissions, but
have not been included in this abandoned mine  emissions inventory.  In 2002, active surface
mines emitted 25.4 Bcf (10.2 million tonnes of CO2),  or 19% of total U.S. coal mine methane
emissions.  Although some abandoned surface mines may  contribute methane  emissions, it  is
assumed that they constitute a negligible share of abandoned mine emissions. The coal seams
mined at the surface are shallow, and therefore less likely to have a  high  gas content.  In
US Environmental Protection Agency                                                       47

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addition, regulations often require reclamation of the mined void, which for surface mining may
involve leveling and covering the mined-out area.

              7.4.5  Total estimated uncertainty range

These key  uncertainties,  as well as  those associated with coal permeability,  mine seal
effectiveness,  abandonment status, and the Monte Carlo  simulation36 result in  an estimated
range of certainty of + 20%. Figure 22 shows the  high and low estimate range  within a 95%
confidence interval for net emissions. For each of the years  in this inventory, the estimated
mean-value emissions varied from the 50% case (the most  likely case) by only +3%.  The 50%
case was developed  from an uncertainty analysis with a 95% confidence interval.  Statistically,
the closeness of the calculated mean to the probability distribution analysis results indicates that
the sample population of gassy mines used for the analysis has a normal distribution.

The IPCC  considers an uncertainty level of + 20% to 55% acceptable  for Tier 2  coal  mine
methane emissions inventories (IPCC, 1997). When compared to other IPCC Tier 2 emission
inventories,  the methodology used  in this report produced a fairly narrow range of values. The
range is relatively narrow in part because mine-specific data (required for a Tier 3 inventory) is
used. The largest degree of uncertainty is associated with abandoned mines of unknown status,
(which account for 36% of the mines), which have an overall uncertainty of + 60%.

    Figure  22. Range of Abandoned Mine Methane Emissions (net) Estimates for 1990-2002
      c-
      o
      55.
      (0
      c
      o
      'in
      
-------
       7.5    Projecting future emissions from abandoned coal mines

The total  methane liberated from active underground mines continues to decrease for  U.S.
mines.37 Yet active mine emissions  (and therefore initial emission  rates for mines at time of
abandonment) continue to increase from individual mines. As more  mines  incorporate longwall
mining techniques, ventilation equipment becomes  more sophisticated,  and mining depths
increase, the emissions  from  active  coal mines are likely to  continue to increase.  Figure 23
shows that the per-mine average ventilation emissions for gassy coal mines that were closed
from  1991-1999  nearly  doubled from the 1990  inventory.   Furthermore, average ventilation
emissions for currently operating mines  (with emissions greater than 100 mcfd) are more  than
double that of the active-mine emissions  for mines closed from 1991-1999.

Although the specific emissions of active  gassy mines in the U.S. are increasing, the actual
number of active mines has decreased.  For example, fewer than 125 gassy mines have been
operating in the  U.S.  since  1995  (EPA,  2002), and only 95 gassy mines were active in 2002.
Underground coal production in the U.S. has been declining since 1997, with a corresponding
decrease in the associated mine methane emissions. As a result of these trends, the downward
trend in total abandoned mine emissions since  1996, shown in Figure 22, is expected continue
as fewer gassy mines remain to close.

           Figure 23. Trends in Coal Mine Emissions from Active Gassy U.S. Mines
                     Average U.S. Coal Mine Emissions for
                                 Mines >100 mcfd
•g 2,500

~ 2,000 -

I 1-500
(A
I 1,000
                0)
                c
                re
                4-1
                0>
     500 -
                                                       -2,250-
                                           1,440
                              750
                         Mines Closed Mines Closed     Mines
                            1990 or      1991-1999    Currently
                            before                    Operating
                                                     (2002 Data)
The  methodology for creating this  inventory allows  estimation of future abandoned  mine
emissions,  by coupling predicted decline curves with  presumed closure dates for currently
active mines. Abandoned  mine emissions could then  be forecasted for any given  year. In
37
  According to  Inventory of U.S. Greenhouse Gas Emissions and Sinks:  1990 - 2000, the methane
liberated from underground mines decreased by 13.5 million tonnes of C02 equivalent, from 67.6 million
tonnes to 51.1 million tonnes.  This equates to a reduction of 32.4 Bcf or slightly less than 1 Bm3.
US Environmental Protection Agency
                                                                     49

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addition,  this estimation  methodology allows coal mining  regions with high  emissions  or
emission anomalies to be  identified.  Most importantly,  this methodology  may be used  to
determine the effect that abandoned mine emissions may have on the U.S. Greenhouse Gas
Inventory in future years.
50                                                     US Environmental Protection Agency

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 8.0   Conclusions

 EPA's Inventory of U.S.  Greenhouse Gas Emissions and Sinks includes methane emission
 estimates for underground mining, surface mining, and post-mining activities at active mines.38
 The emissions estimation methodology and results described  in  this report  enables the
 quantification of emissions from abandoned mines, for which there is currently no recognized
 methodology.

 This methodology has been designed to produce robust estimates and to incorporate new data
 as available. It allows annual emissions inventories to be readily updated, because it is flexible
 enough to allow  additional mines to be included in  the  inventory  as  information  becomes
 available. In addition,  the method can  be used  to predict future  emissions from existing
 underground coal mines for any given year. Furthermore, the mine database  is thorough and
 representative of the majority of methane emissions from abandoned mines in  the U.S. Finally,
 the method requires minimal  inputs: active  mine emissions, mine  closure dates,  and coal
 adsorption isotherm data. Thus, it could potentially be used to  estimate coal mine methane
 emissions in other nations.

 The methodology  and emission  estimates presented in this  report are the  first attempt to
 systematically quantify emissions from abandoned coal mines in the U.S..  EPA will continue to
 refine the methodology to quantify abandoned mine emissions with greater certainty.  Important
 next steps include:

    •   Researching additional  sources for data on  mines closing before  1972  to further refine
       estimates for emissions from the pre-1972 mines

    •   Developing more  accurate estimates of the percentage of gas liberated by drainage
       systems before 1990

    •   Identifying all abandoned mine methane recovery projects in the U.S. that operated from
       1990 to the present and obtaining data on emission reductions

    •   Considering the  results of any additional work  being conducted with regard to the
       uncertainty in MSHA ventilation emission data

    •   Obtaining more field data to  verify  methodological  results or serve as the  basis for
       refinements to the methodology

    •   Developing  methodologies  to  set baselines and calculate emissions avoided on a
       project-specific basis

    •   Incorporating the abandoned mine emissions into the U.S. Inventory of Greenhouse Gas
       Emissions and Sinks

    •   Evaluating the method for its application to other countries,  and if not, developing a more
       universal methodology
38 Post-mining emissions are emissions from coal during storage (e.g. in piles) and transportation (e.g.
while in train cars) prior to the coal's usage as fuel.


US Environmental Protection Agency                                                        51

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Several other countries have also begun to quantify their abandoned mine emissions. As EPA
continues refining its methodology and estimates, we welcome comments and suggestions on
this report  and the  methodology,  as there are  many potential gains from critical  input and
coordination.
52                                                     US Environmental Protection Agency

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9.0   References

IPCC/UNEP/OECD/IEA,  1997, Revised 1996  IPCC Guidelines for National Greenhouse Gas
Inventories,  Paris:  Intergovernmental Panel on Climate Change; J. T. Houghton, L.G. Meiro
Filho, B.A. Callander,  N. Harris, A. Kattenberg, and  K. Maskell,  eds.;  Cambridge University
Press, Cambridge, U.K.

Fetkovich, M.J., Fetkovich, E. J., and Fetkovich, M.D.: "Useful Concepts for Decline Curve
Forecasting, Reserve Estimation and Analysis," paper SPE 28628 presented at the 1994 SPE
69th Annual Technical Conference and Exhibition

Gan,  H.. Nandi. S.P., and Walker, P.L. Jr., 1972, Nature  of the Porosity in American Coals:
Fuel, v. 51. p 272-277

Garcia,  Fred and  J. Cervik, 1987, Method Factors  for Anemometer Measurement at Pipe
Outlets, U.S Bureau of Mines, Rl 9061, Pittsburgh, PA.

Garcia, Fred. Frank E. McCall, and Michael A. Trevits, 1994, Proceedings of the 7th U.S. Mine
Ventilation Symposium, A Case Study of Methane  Gas Migration Through Sealed Mine Gob
Into Active Mine Workings, U.S. Bureau of Mines, Pittsburgh, PA.

Gas Research  Institute, 1996,  A  Guide  To  Coalbed Methane  Reservoir Engineering, GRI
Reference No GRl-94/0397, Chicago, IL.

Grau, Roy H III and John  C. LaScola, 1981, Methane Emissions From U.S. Coal Mines in
1980, U.S Bureau of Mines,  Information Circular 8987, Pittsburgh, PA.

Irani,  M. C   E D  Thimons,  T. G. Bobick, Maurice Deul, and M. G. Zabetakis, 1972, Methane
Emissions From US Coal Mines, A Survey, U.S. Bureau of Mines, Information Circular 8558,
Pittsburgh PA

Irani, M. C  P W Jeran, and Maurice Deul, 1974, Methane Emissions From  U.S. Coal Mines in
1973, A Survey (A Supplement to  1C 8558), U.S. Bureau of Mines, Information Circular 8659,
Pittsburgh PA

Irani, M. C  J H Jansky, P.  W. Jeran, and G. L. Hassett, 1977, Methane Emissions From U.S.
Coal Mines m 1975 A Survey, (A Supplement to ICs  8558 and 8659), U.S. Bureau of Mines,
Information Circular 8733, Pittsburgh, PA.

Masemore  S  S Piccot, E. Ringler, and W. P. Diamond, 1996, Evaluation and Analysis of Gas
Content and Coal Properties of Major Coal Bearing  Regions of the United States, EPA-600/R-
96-065, Washington. D.C.

Mutmansky,  Jan M.. and Yanbei Wang, 2000, Analysis of Potential Errors in Determination of
Coal Mine Annual Methane  Emissions,  Pennsylvania  State University, Department of Energy
and Geo-Environmental  Engineering, University Park, PA.
US Environmental Protection Agency                                                       53

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Kirchgessner, D.A.,  Piccot,  S.  D., and  Masemore,  S.S., 2001, An  Improved Inventory of
Methane Emissions  from  Coal  Mining in the  U.S., Journal of Air  and Waste Management
Association, Volume 50:1904-1919, March 2001.

Northover, E.W., Vane Anemometer Measurements of the Quantity of Air Entering and Leaving
Auxiliary Systems, National Coal Board, M.R.E.  Rep. 2061, March 1957, London.

Seidle,  J.P.  and  L.E. Arri,  "Use of  Conventional Reservoir  Models  for Coalbed Methane
Simulation,"  Paper CIM/SPE  90-118,  presented  at  the CIM/SPE  International  Technical
Meeting, Calgary, Alberta (June 10-13, 1990)

Slider,   H.C.  Worldwide  Practical Petroleum  Reservoir  Engineering  Methods.,  PennWell
Publishing Company, Tulsa, Oklahoma, 1983, (P. 45)

Soot,  Peet,  Northwest  Fuel Development, Inc.,  Various Emissions  Databases and  Field
Measurement Results.

U.S. Environmental  Protection Agency,  1990, Methane Emissions  From Coal Mining, EPA
400/9-90/008, Washington  D.C.

U.S. Environmental Protection Agency, 2002,  Greenhouse Gas Emissions and Sinks: 1990-
2001, EPA 236-R-00-001, Washington D.C.

U.S. Department of Labor, 2000,  Mine Safety and Health Administration, Coal Mine Safety and
Health, Coal MIS Data Base, Arlington, WV

Yee, D., Seidle,  J.P. and Hanson, W.B. "Gas Sorption on Coal and Measurement  of Gas
Content" in Hydrocarbons from Coal, AAPG Studies In Geology #38, 1993.
54                                                   US Environmental Protection Agency

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        APPENDIX A.  U. S. Abandoned Coal Mine Database
State
OK
OK
OK
KY
KY
KY
KY
KY
KY
KY
KY
KY
KY
KY
KY
KY
KY
KY
KY
KY
KY
KY
KY
KY
KY
KY
KY
KY
KY
KY
KY
TN
TN
TN
VA
VA
VA
VA
VA
VA
VA
VA
VA
VA
VA
VA
VA
County
Haskell
Le Flore
Okmulgee
Harlan
Harlan
Harlan
Harlan
Henderson
Johnson
Leslie
Leslie
Leslie
Letcher
Martin
Martin
Martin
MeCreary
Pike
Pike
Pike
Pike
Pike
Pike
Pike
Pike
Pike
Pike
Pike
Pike
Whitley
Whitley
Clearborne
Rosedale
Sequatchie
Buchanan
Buchanan
Buchanan
Buchanan
Buchanan
Buchanan
Buchanan
Buchanan
Buchanan
Buchanan
Buchanan
Buchanan
Buchanan
Coal Basin
Arkoma
Arkoma
Arkoma
Central Appl.
Central Appl.
Central Appl.
Central Appl.
Central Appl.
Central Appl.
Central Appl.
Central Appl.
Central Appl.
Central Appl.
Central Appl.
Central Appl.
Central Appl.
Central Appl.
Central Appl.
Central Appl.
Central Appl.
Central Appl.
Central Appl.
Central Appl.
Central Appl.
Central Appl.
Central Appl.
Central Appl.
Central Appl.
Central Appl.
Central Appl.
Central Appl.
Central Appl.
Central Appl.
Central Appl.
Central Appl.
Central Appl.
Central Appl.
Central Appl.
Central Appl.
Central Appl.
Central Appl.
Central Appl.
Central Appl.
Central Appl.
Central Appl.
Central Appl.
Central Appl.
Mine Name
Choctaw Coal
Howe No 1
Pollyanna No 4
No. 10 Wisconsin Steel
Mine
Creech No 1
Harlan No.1
Arch No. 37
Retiki
White Ash No 1
No 2
Unicorn No. 2
No. 60
Scotia Mine
Peter Cave No 1
Wolf Creek No.3
Wolf Creek No 4
Justus
Big Creek No 2
Leslie
Scotts Branch
No. 1 Mine (D)
No. 2 Mine (D)
No. 6 Mine (D)
No. 1 Mine (D)
No. 1 Mine
Ovenfork Mine
Mate Creek No 2
No 3
No. 9
No. 1
Blue Gem No 1
Matthews Mine
Volunteer No 1
Kelly's Creek No. 63
Jewell No 18
LAMBERT FORK
WINSTON MINE NO 10
No 1
1-A Mine
VIRGINIA POCAHONTAS 4
Raven No. 1
VP 1
Big Creek Seaboard No. 1
Beatrice Mine
No 4
Virginia Pocahontas No 2
VPNoS
Current Emissions
Status







Sealed






Sealed
Flooded


Sealed
















Flooded
Sealed
Flooded
Venting/
partially Flooded
Sealed/
Recovering Methane
Flooded
Recovering Methane
Venting
Sealed
Flooded
Sealed/
Recovering Methane
Recovering Methane
Date
Abandoned
10/29/90
06/10/72
10/11/96
6/10/1972
6/15/1995
7/10/1995
1/21/1999
02/03/95
06/10/77
08/29/96
8/29/1996
05/07/01
06/10/82
06/10/77
06/10/77
10/2/1995
06/15/94
06/10/81
06/10/81
06/10/81
10/20/82
12/16/82
03/04/83
06/14/83
11/14/88
1/15/1992
06/10/94
06/10/94
8/25/1995
08/15/86
02/27/97
12/29/1990
06/10/74
2/18/1994
06/70/82
06/18/85
02/25/92
04/23/93
06/10/93
8/9/1993
6/10/1994
06/10/94
8/18/1995
12/5/1995
03/21/96
12/11/1996
12/10/1997
Active
Mine
Emissions
(mmcfd)
0.35
1.6
0.35
0.1
0.2
0.2
1
0.35
0.35
0.35
0.2
0.3
0.4
0.15
0.75
1
0.35
0.15
0.75
0.35
0.35
0.35
0.35
0.35
0.35
2.4
0.75
0.35
0.1
0.35
0.35
0.2
2.5
0.1
0.15
0.75
0.35
0.35
0.35
2.4
0.1
7.5
2.4
6.8
0.35
2.8
7.3
US Environmental Protection Agency
A-1

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        APPENDIX A. U. S. Abandoned Coal Mine Database
State
VA
VA
VA
VA
VA
VA
VA
VA
VA
VA
VA
VA
VA
VA
VA
VA
VA
VA
VA
VA
VA
VA
VA
VA
VA
VA
VA
VA
VA
VA
WV
WV
WV
WV
WV
WV
WV
WV
WV
WV
WV
WV
WV
WV
WV
WV
WV
WV
County
Buchanan
Dickenson
Dickenson
Dickerson
Lee
Lee
Lee
Russell
Russell
Russell
Russell
Russell
Ta2ewell
Tazewell
Wise
Wise
Wise
Wise
Wise
Wisf-
Wist-
Wl5,(-
Wisซ-
V'VISC
Wisi
Wisป-
V.IS.'
Wisซ
V\is<
Coal Basin
Central Appl.
Central Appl.
Central Appl.
Central Appl.
Central Appl.
Central Appl.
Central Appl.
Central Appl.
Central Appl.
Central Appl.
Central Appl.
Central Appl.
Central Appl.
Central Appl.
Central Appl.
Central Appl.
Central Appl.
Central Appl.
Central Appl.
Central Appl.
Central Appl.
Central Appl.
Central Appl.
Central Appl.
Central Appl.
Central Appl.
Central Appl.
Central Appl.
Central Appl.
Wist- i Central Appl.
b Kinป Central Appl.
b^xini j Central Appl.
b>:x)n<- | Central Appl.
faoor't-
b:>on(
Central Appl.
Central Appl.
boom ; Central Appl.
boonc [ Central Appl.
biookf- ' Central Appl.
brooM-
Frfyetlf
Fayette
Kanawlia
Kanawha
Kanawha
Kanawha
Lincoln
Logar
Logan
Central Appl.
Central Appl.
Central Appl.
Central Appl.
Central Appl.
Central Appl.
Central Appl.
Central Appl.
Central Appl.
Central Appl.
Mine Name
1-A
Splashdam
McClure No 1
Moss No 3
No. 1 Mine
#1
Holton
Chaney Creek No 2
MOSS NO. 2
HURRICANE CREEK
Moss No 3A2
Moss No 4
Amonate No 31
No 1
PRESCOTT NO 1
No 7
Virginia No 1
Wentz B Portal
Osaka No 2
Prescott No 2 Mine
No 1
No. 2
Bullitt Mine
Wentz No 1
Pierre
Har-Lee No 3
No 1
Deep No 20
#12
Sargent Hollow
Ferrell No 17
HAMPTON NO 3 MINE
Wharton No. 4
HAMPTON NO 4
Birchfield No 1
Oasis No. 1
Lightfoot No. 1
Beech Bottom
Valley Camp No 1
Royal No 5
Siltix
No 34
Cannelton No 8
MADISON NO 1 MINE
Lady Dunn No 105
Five Block No 4 Mine
Guyan No 5
No4-H
Current Emissions
Status

Partially Flooded
Flooded
Flooded


Flooded
Flooded
Flooded
Flooded
Flooded
Adjacent to strip
mine

Flooded
Flooded


Flooded

Sealed
Flooded
Flooded
Venting
Flooded
Venting
Sealed
Flooded
Venting


Flooded
Flooded

Flooded
Venting




Sealed
Flooded

Venting

Flooded

Flooded
Sealed
Date
Abandoned
3/12/2001
09/27/95
8/20/1996
06/10/76
04/28/92
03/24/94
01/23/97
06/10/74
07/15/83
06/29/87
03/18/88
01/11/89
09/26/94
06/70/95
02/20/81
06/70/82
06/70/82
06/70/82
06/16/89
01/11/94
04/08/94
5/24/1995
08/01/95
01/25/96
01/31/96
04/29/96
05/08/96
01/08/97
5/21/1999
7/12/2001
06/70/82
02/02/87
3/23/1987
01/23/91
06/70/92
06/70/96
2/9/2000
06/10/74
06/70/82
06/70/77
10/23/87
06/70/72
04/05/83
06/14/84
11/12/87
09/26/80
06/70,74
06/10/74
Active
Mine
Emissions
(mmcfd)
0.25
0.35
1.4
1.4
0.35
0.75
0.35
0.35
1.3
0.35
0.75
0.75
2.2
0.35
0.35
0.15
0.15
0.35
0.35
0.35
0.35
0.1
0.75
0.35
0.35
0.35
0.35
0.35
0.1
0.2
0.35
0.35
0.2
0.35
1.5
1.1
0.2
0.35
0.35
0.35
0.35
0.35
0.35
0.35
0.75
0.75
0.35
0.35
A-2
US Environmental Protection Agency

-------
        APPENDIX A.  U. S. Abandoned Coal Mine Database
State
WV
wv
vw
WV
wv
WV
WV
WV
WV
WV
WV
WV
WV
WV
WV
WV
WV
WV
WV
WV
WV
WV
WV
WV
WV
WV
WV
WV
WV
WV
WV
WV
WV
WV
WV
WV
WV
WV
WV
WV
WV
WV
WV
WV
WV
WV
County
Logan
Logan
Logan
Logan
McDowell
McDowell
McDowell
McDowell
McDowell
McDowell
McDowell
McDowell
McDowell
McDowell
McDowell
McDowell
McDowell
Mingo
Mingo
Mingo
Mingo
Nicholas
Nicholas
Nicholas
Nicholas
Nicholas
Nicholas
Nicholas
Nicholas
Nicholas
Nicholas
Nicholas
Nicholas
Nicholas
Nicholas
Nicholas
Raleigh
Raleigh
Raleigh
Raleigh
Raleigh
Raleigh
Raleigh
Raleigh
Raleigh
Raleigh
Coal Basin
Central Appl.
Central Appl.
Central Appl.
Central Appl.
Central Appl.
Central Appl.
Central Appl.
Central Appl.
Central Appl.
Central Appl.
Central Appl.
Central Appl.
Central Appl.
Central Appl.
Central Appl.
Central Appl.
Central Appl.
Central Appl.
Central Appl.
Central Appl.
Central Appl.
Central Appl.
Central Appl.
Central Appl.
Central Appl.
Central Appl.
Central Appl.
Central Appl.
Central Appl.
Central Appl.
Central Appl.
Central Appl.
Central Appl.
Central Appl.
Central Appl.
Central Appl.
Central Appl.
Central Appl.
Central Appl.
Central Appl.
Central Appl.
Central Appl.
Central Appl.
Central Appl.
Central Appl.
Central Appl.
Mine Name
Paragon
NO 1 CEDAR GROVE
Dehue
Guyan No 1
Cannelton No 3 & 4
Pocahontas No 7
Maitland
U.S. Steel No 14-4
NEWHALL NO 6 MINE
SHANNON BRANCH MINE
GARY NO 10
Little B Mine No 2
Keystone No 1 Mine
Ogla
No 4 Mine
U.S. Steel No 2
ANGUS
National No 25
Gary No 20-B
No 19
Rocky Hollow
Sewell No 4
Coalbank Fork No 9
Mine #3
Mine No 4
No 24 Mine
Mine No 4
Hewett Fork No 1A
Big Foot Coal 4-B Mine
Stone Run 6A
SEWELL #1A
SEWELL NO 1
Donegan No 10
Mine No 1
Long Run Deep Mine No 1
Hutchinsons Branch Mine
No. 1
East Gulf
Bethlehem No 46
Macalpin #3
ECCLES NO 5
KEYSTONE NO 4-A MINE
SLAB FORK NO 8
SLAB FORK NO. 10 MINE
WINDING GULF #4
ECCLES NO 6
KEYSTONE NO 4 MINE
Current Emissions
Status
Flooded
Flooded
Sealed
Flooded
Venting /
Partially Flooded

Venting /
Partially Flooded
Venting /
Partially Flooded
Venting/
Partially Flooded
Flooded
Sealed
Sealed

Flooded
Sealed
Venting/
Partially Flooded
Venting



















Flooded
Flooded
Flooded
Flooded
Flooded
Flooded
Flooded
Flooded
Flooded
Flooded
Date
Abandoned
06/10/74
09/26/80
11/14/85
07/03/90
06/10/74
06/10/74
06/10/77
06/10/77
10/01/79
11/05/82
02/28/84
12/19/85
04/01/87
06/17/88
06/27/88
06/10/91
10/24/95
06/10/74
06/10/82
07/02/90
11/19/94
06/10/72
02/27/82
04/26/82
07/27/82
09/15/82
09/20/82
01/05/83
03/21/83
06/14/83
04/22/86
09/06/88
06/14/90
06/24/93
04/17/96
06/26/00
06/10/74
06/10/77
10/19/79
10/01/81
07/21/82
02/06/84
02/06/84
02/06/84
06/28/85
10/01/85
Active
Mine
Emissions
(mmcfd)
0.15
2.4
0.35
0.35
0.35
0.15
1
1.4
0.75
1.3
0.75
2.4
0.35
1.6
2.4
0.9
0.35
0.35
0.15
0.35
0.35
0.75
2.4
2.4
2.4
2.4
2.4
2.4
2.4
2.4
0.35
0.35
0.35
2.4
2.4
0.25
1
0.15
0.3
0.75
0.35
0.75
0.75
0.35
0.35
0.35
US Environmental Protection Agency
A-3

-------
        APPENDIX A. U. S. Abandoned Coal Mine Database
State
WV
wv
WV
wv
wv
wv
wv
wv
wv
wv
wv
wv
wv
wv
wv
wv
wv
wv
wv
wv
wv
wv
wv
wv
wv
wv
wv
wv
IL
IL
IL
IL
IL
IL
IL
IL
IL
IL
IL
IL
IL
IL
IL
IL
IL
County
Raleigh
Raleigh
Raleigh
Raleigh
Raleigh
Raleigh
Raleigh
Raleigh
Raleigh
Upshur
Upshur
Upshur
Webster
West
Wyoming
Wyoming
•Wyoming
Wyoming
Wyoming
Wyoming
Wyoming
Wyoming
Wyoming
Wyoming
Wyoming
Wyoming


Christian
Clinton
Douglas
Douglas
Franklin
Franklin
Franklin
Franklin
Franklin
Gallatin
Gallatin
Hamilton
Jefferson
Jefferson
Jefferson
Jefferson
Jefferson
Coal Basin
Central Appl.
Central Appl.
Central Appl.
Central Appl.
Central Appl.
Central Appl.
Central Appl.
Central Appl.
Central Appl.
Central Appl.
Central Appl.
Central Appl.
Central Appl.
Central Appl.
Central Appl.
Central Appl.
Central Appl.
Central Appl.
Central Appl.
Central Appl.
Central Appl.
Central Appl.
Central Appl.
Central Appl.
Central Appl.
Central Appl.
Central Appl.
Central Appl.
Illinois
Illinois
Illinois
Illinois
Illinois
Illinois
Illinois
Illinois
Illinois
Illinois
Illinois
Illinois
Illinois
Illinois
Illinois
Illinois
Illinois
Mine Name
KEYSTONE NO 5 MINE
SKELTON MINE
Macalpin
Bonny
No 4 Mine
Beckley
KEYSTONE NO 2 MINE
Tommy Creek #1
Maple Meadow Mine
Adrian Mine
Queen # 14 Mine
Grand Badger No 1A Mine
Smoot
Dixianna
Buckeye Coll.
Kepler
Otsego
Itmann No 4
GASTON NO 2 MINE
Beckley No 1
National Pocahontas
ITMANN #3
Beckley No 2
ITMANN # 1 AND SHOP
Shawnee Mine
KOPPERSTON NO. 1
Mine No 1
Bells Creek Mine No. 1
Peabody No. 10
Monterey No 2
Zeigler#5
Murdock
Old Ben No 27
Old Ben No 25
Old Ben No 21
Old Ben No 24
Old Ben No 26
Eagle No. 2
Eagle No 1
Inland No 2
Inland No 1
Orient #3
Orient #5
Wheeler Creek
Orient No 6
Current Emissions
Status
Flooded
Flooded
Flooded
Sealed/
Recovery Pending
Venting/
Partially Flooded
Flooded
Flooded
Flooded
Sealed/
Recovery Pending





Sealed
Venting/
Partially Flooded

Flooded

Venting/Partially
Flooded
Venting/Partially
Flooded
Sealed
Venting/Partially
Flooded
Sealed
Venting/Partially
Flooded
Sealed




Sealed


Venting Methane

Sealed
Sealed




Sealed
Sealed

Sealed /
Date
Abandoned
12/31/85
12/08/86
07/06/89
06/10/90
1/29/1991
7/1/1992
5/7/1993
03/20/96
7/10/1998
6/10/1977
11/05/82
08/08/83
01/22/97
06/10/72
06/10/74
06/10/74
06/10/74
06/10/76
01/15/82
2/9/1982
01/31/84
05/20/87
6/21/1988
06/12/92
11/7/1994
01/10/96
12/13/82
6/10/1998
7/10/1994
07/25/96
05/27/87
11/1/1996
02/05/87
9/10/1994
11/13/95
7/10/1998
7/10/1998
06/70/94
05/15/96
06/70/82
06/70/82
02/01/84
02/01/84
04/04/88
3/13/1997
Active
Mine
Emissions
(mmcfd)
0.35
0.35
0.35
3.4
2.9
3.7
0.6
0.35
2.6
0.2
2.4
2.4
0.35
0.35
0.15
0.75
0.15
1
0.35
0.7
0.75
1.4
1
0.35
2.4
0.35
2.4
0.50
0.75
0.75
0.35
0.75
0.75
1
1.4
1.2
1.6
0.75
0.35
0.35
1.1
1.5
1.5
0.75
1
A-4
US Environmental Protection Agency

-------
        APPENDIX A.  U. S. Abandoned Coal Mine Database
State

IL
IL
IL
IL
IL
IL
IL
IL
IL
IL
IL
IL
IL
IL
IN
IN
IN
KY
KY
KY
KY
KY
KY
KY
KY
KY
KY
KY
KY
KY
KY
KY
KY
KY
KY
KY
KY
KY
KY
KY
KY
KY
KY
KY
OH
OH
County

Montgomery
Montgomery
Montgomery
Perry
Randolph
Randolph
Randolph
Saline
Saline
Saline
St. Clair
Williamson
Williamson

Gibson
Sullivan
Sullivan
Hopkins
Hopkins
Hopkins
Hopkins
Hopkins
Hopkins
Hopkins
Hopkins
Hopkins
Hopkins
Muhlenberg
Muhlenberg
Muhlenberg
Muhlenberg
Ohio
Ohio
Ohio
Union
Union
Union
Union
Union
Union
Union
Webster
Webster
Webster
Belmont
Belmont
Coal Basin

Illinois
Illinois
Illinois
Illinois
Illinois
Illinois
Illinois
Illinois
Illinois
Illinois
Illinois
Illinois
Illinois
Illinois
Illinois
Illinois
Illinois
Illinois
Illinois
Illinois
Illinois
Illinois
Illinois
Illinois
Illinois
Illinois
Illinois
Illinois
Illinois
Illinois
Illinois
Illinois
Illinois
Illinois
Illinois
Illinois
Illinois
Illinois
Illinois
Illinois
Illinois
Illinois
Illinois
Illinois
Northern
Appl.
Northern
Appl.
Mine Name

Crown
Crown #2
HILLSBORO MINE
Kathleen
Baldwin No 1
No 11
Spartan
No 16
No 5
Sahara No 20
River King Underground
ZEIGLER#4 UG
ORIENT NO. 4
Big Ridge Mine
Kings
Thunderbird
Buck Creek
East Diamond
Island Creek No 9
FIES MINE
ZEIGLERNO9MINE
Drake No 4
Providence No 1
Busick Mine
Green River No. 9
West Hopkins
Richland Mine
Drake No 1
Crescent
River Queen Underground
No 1
Star Underground
ALSTON NO 3 MINE
Peacock Coal Mine No.
KEN NO 4 MINE
Pyro No 2
Peabody Camp No 2
Pyro No. 11 Highway
Pyro No. 9 Slope William
Station
Camp No.2
Hamilton No 2
Hamilton No 1
Dorea
Wheatcroft #9
Smith U/G mine
Powhatan No 4
POWHATAN NO 5 MINE
Current Emissions
Status
Recovering Methane
Sealed
Sealed




Sealed
Flooded
Flooded
Flooded

Sealed
Sealed

Sealed
Sealed

Venting/Flooded
Venting/Flooded
Venting/Flooded

Flooded
Venting/Flooded


Sealed/Filled

Sealed/Filled
Flooded
Flooded
Flooded



Sealed
Sealed



Venting/Flooded
Venting/Flooded
Sealed/Filled


Venting
Venting
Date
Abandoned

06/10/72
06/10/82
12/02/83
08/23/95
067? 0/82
06/70/82
12/10/97
06/10/72
06/10/72
06/10/82
05/11/90
11/14/80
09/01/87
3/15/1997
06/10/74
06/10/72
2/2/1998
06/10/72
06/10/74
01/11/80
01/11/80
04/27/82
06/70/83
06/29/83
5/1/1992
06/70/94
9/21/2000
06/10/72
06/10/77
02/02/81 -
05/15/96
02/06/81
02/01/83
09/01/84
06/10/74
06/10/83
11/15/1991
11/15/1991
8/20/1993
03/18/94
05/14/96
01/29/93
06/10/96
9/21/2000
06/10/78
03/31/81
Active
Mine
Emissions
(mmcfd)

1
1.1
0.35
0.35
0.35
0.15
0.35
0.15
0.15
0.35
0.35
0.75
0.75
0.60
0.35
0.75
0.35
0.35
0.35
1.1
0.75
0.35
0.35
0.35
1.2
0.35
0.2
0.35
0.75
0.35
0.35
0.35
0.75
0.35
0.35
0.35
0.2
1.2
0.4
0.35
0.35
0.35
1.9
0.35
0.75
0.35
US Environmental Protection Agency
A-5

-------
        APPENDIX A. U. S. Abandoned Coal Mine Database
State
OH
OH
OH
OH
OH
OH
OH
OH
OH
OH
OH
OH
OH
PA
PA
PA
PA
PA
PA
PA
PA
PA
PA
PA
PA
PA
PA
PA
PA
PA
PA
PA
County
Belmont
Belmont
Belmont
Belmont
Harrison
Harrison
Harrison
Harrison
Harrison
Jefferson
Monroe
Perry
Vinton
Allegheny
Allegheny
Allegheny
Allegheny
Allegheny
Allegheny
Armstrong
Armstrong
Armstrong
Armstrong
Cambria
Cambria
Cambria
Cambria
Cambria
Cambria
Cambria
Centre
Fayette
Coal Basin
Northern
Appl.
Northern
Appl.
Northern
Appl.
Northern
Appl.
Northern
Appl.
Northern
Appl.
Northern
Appl.
Northern
Appl.
Northern
Appl.
Northern
Appl.
Northern
Appl.
Northern
Appl.
Northern
Appl.
Northern
Appl.
Northern
Appl.
Northern
Appl.
Northern
Appl.
Northern
Appl.
Northern
Appl.
Northern
Appl.
Northern
Appl.
Northern
Appl.
Northern
Appl.
Northern
Appl.
Northern
Appl.
Northern
Appl.
Northern
Appl.
Northern
Appl.
Northern
Appl.
Northern
Appl.
Northern
Appl.
Northern
Appl.
Mine Name
POWHATAN NO 1
Powhatan No 3
ALLISON MINE
Saginaw no 1
Nelms#1
Rose Valley No. 6
VAIL
Oak Park No 7
NELMS NO 2
Jensie
POWHATAN 7 MINE
Sunnyhill No. 9 South
Raccoon #3
Oakmont
HARMAR MINE
Renton Mine
Allegheny No. 2 & Portal
No. 3
Newfield
OCEAN #5 MINE
Harold No 1
Jane Nos 1 & 2
DAVID MINE
Jane
Bethlehem No 31
Bethlehem No 77
Nanty Glo No 31
Bethlehem No 32
Lancashire No 25
Lancashire No 20
Cambria Slope No 33
Rushton
Isabella
Current Emissions
Status
Sealed
Venting
Venting
Venting
Sealed/
Recovering Methane

Venting
Sealed/
Recovering Methane
Venting
Venting
Temporary Seal



Sealed


Sealed
Sealed


Sealed/Adjacent to
Dianne Mine
Sealed
Sealed
Flooded/
Pumping Water
Sealed
Sealed/
Recovering Methane
Sealed
Sealed
Recovering Methane

Sealed
Date
Abandoned
02/16/82
03/18/83
01/11/84
06/17/93
06/10/77
8/28/1980
01/04/84
05/13/88
2/29/1996
06/10/74
08/03/92
7/10/1991
09/25/89
05/01/80
01/13/89
10/23/1992
10/25/1993
06/26/95
03/18/97
06/10/74
06/10/84
02/27/96
08/22/96
06/10/78
06/10/78
06/10/84
09/17/85
03/05/86
09/09/88
7/15/1994
12/31/1992
06/10/74
Active
Mine
Emissions
(mmcfd)
0.75
0.35
0.35
0.35
1.9
0.5
0.35
0.75
1.5
0.35
0.35
0.1
0.35
0.35
0.35
0.7
0.1
0.75
0.35
0.15
0.75
0.35
0.75
0.35
0.35
0.35
4.5
0.35
0.9
8.5
0.4
0.35
A-6
US Environmental Protection Agency

-------
        APPENDIX A.  U. S. Abandoned Coal Mine Database
State
PA
PA
PA
PA
PA
PA
PA
PA
PA
PA
PA
PA
PA
PA
PA
PA
PA
PA
PA
PA
PA
PA
PA
PA
PA
PA
PA
PA
PA
PA
PA
PA
County
Greene
Greene
Greene
Greene
Greene
Greene
Greene
Greene
Indiana
Indiana
Indiana
Indiana
Indiana
Indiana
Indiana
Indiana
Indiana
Indiana
Indiana
Indiana
Luzerne
Luzerne
Somerset
Somerset
Somerset
Washington
Washington
Washington
Washington
Washington
Washington
Washington
Coal Basin
Northern
Appl.
Northern
Appl.
Northern
Appl.
Northern
Appl.
Northern
Appl.
Northern
Appl.
Northern
Appl.
Northern
Appl.
Northern
Appl.
Northern
Appl.
Northern
Appl.
Northern
Appl.
Northern
Appl.
Northern
Appl.
Northern
Appl.
Northern
Appl.
Northern
Appl.
Northern
Appl.
Northern
Appl.
Northern
Appl.
Northern
Appl.
Northern
Appl.
Northern
Appl.
Northern
Appl.
Northern
Appl.
Northern
Appl.
Northern
Appl.
Northern
Appl.
Northern
Appl.
Northern
Appl.
Northern
Appl.
Northern
Appl.
Mine Name
WARWICK MINE NO. 2
ROBENAMINE
GATEWAY MINE
Nemacolin Mine
Shannopin Mine
Lazarus
Monongahela Resource
Warwick Mine No 2
CONEMAUGH NO. 1
Greenwich Collieries No 1
Urling No. 1
Florence No. 1
Urling No. 3
Greenwich Collieries No 2
Homer City
Florence No. 2
Lucerne No 8
Lucerne No. 9
Marion
Lucerne No. 6 Extension
Forge Slope
No. 19 Wanamie Colliery
BIRD #2
BIRD #3
Grove No. 1
VESTA #4 MINE
Beth Ellsworth No 51
WESTLAND #2
Marianna No 58
Clyde
VESTA #5 MINE
MONTOUR#4
Current Emissions
Status
Sealed
Flooded
Venting

Sealed

Venting
Flooded/Pumping
Water


Venting

Venting




Sealed/
Partially Flooded
Sealed*



Flooded
Flooded

Sealed
Flooded
Sealed
Sealed/
Partially Flooded


Flooded
Date
Abandoned
05/01/80
02/12/84
12/9/1992
3/25/1996
3/25/1996
6/13/1996
06/13/96
3/10/1997
09/23/82
8/1/1988
12/18/1989
3/7/1990
1/3/1991
03/13/93
6/30/1993
10/4/1994
03/31/95
8/23/1995
01/23/97
5/24/2000
06/10/72
6/10/1972
10/30/91
10/30/91
12/21/1994
04/14/80
06/70/83
09/27/83
8/31/1988
12/9/1994
04/17/96
05/22/96
Active
Mine
Emissions
(mmcfd)
0.35
2.1
2.6
0.6
1
0.6
0.35
1.1
0.35
0.3
0.7
0.2
0.7
1.2
1.7
0.3
0.35
0.35
0.75
0.3
1.5
0.2
0.75
0.4
0.35
0.35
0.75
0.35
2.2
0.1
1.6
3
US Environmental Protection Agency
A-7

-------
        APPENDIX A. U. S. Abandoned Coal Mine Database
State
PA
PA
PA
PA
WV
WV
WV
WV
WV
WV
WV
WV
WV
WV
WV
WV
WV
WV
WV
WV
WV
WV
WV
WV
WV
WV
WV
WV
WV
WV
WV
WV
County
Washington
Westmoreland
Westmoreland

Barbour
Barbour
Barbour
Gilmer
Gilmer
Grant
Harrison
Harrison
Harrison
Harrison
Marion
Marion
Marion
Marion
Marion
Marion
Marion
Marion
Marion
Marshall
Marshall
Mason
Monongalia
Monongalia
Monongalia
Monongalia
Preston
Preston
Coal Basin
Northern
Appl.
Northern
Appl.
Northern
Appl.
Northern
Appl.
Northern
Appl.
Northern
Appl.
Northern
Appl.
Northern
Appl.
Northern
Appl.
Northern
Appl.
Northern
Appl.
Northern
Appl.
Northern
Appl.
Northern
Appl.
Northern
Appl.
Northern
Appl.
Northern
Appl.
Northern
Appl.
Northern
Appl.
Northern
Appl.
Northern
Appl.
Northern
Appl.
Northern
Appl.
Northern
Appl.
Northern
Appl.
Northern
Appl.
Northern
Appl.
Northern
Appl.
Northern
Appl.
Northern
Appl.
Northern
Appl.
Northern
Appl.
Mine Name
Westland
Banning No 4
DELMONT
Hutchinson
Boulder Mine
BADGER NO. 15 MINE
BADGER NO 14 MINE
Kanawha #1
Kanawha #2
Potomac
Compass No 2
Mars No 2
Williams
Pioneer Mine
Consol No 9
No 93
Phillip Sporn No 1
Bethlehem No 44
Consol No. 20
Bethlehem No 41
JOANNE MINE
Federal No 1
Tygart River
Alexander
Ireland
Putnam
Pursglove No. 15
Blacksville No 1
Arkwright No 1
Osage No. 3
#1
H & H Mine No 2
Current Emissions
Status

Flooded
Flooded
Flooded
Sealed
Sealed
Sealed
Sealed
Sealed
Sealed
Sealed
Flooded
Venting/
Partially Flooded
Venting/
Partially Flooded
Venting/
Recovering Gas
Venting

Venting
Venting/
Recovering Gas
Venting/
Partially Flooded
Venting
Venting
Flooded/
Pumping Water
Venting/
Partially Flooded
Venting



Sealed/Recovering
Methane

Sealed
Sealed
Date
Abandoned
05/22/96
06/70/83
03/04/88
06/10/74
03/17/83
02/26/84
08/28/85
09/15/82
11/02/82
04/07/80
06/10/74
06/10/74
06/10/78
11/12/82
06/10/77
06/10/78
06/10/79
10/1/1979
10/1/1982
02/15/83
03/10/83
03/24/87 .
08/26/93
7/10/1981
06/10/94
06/10/72
9/14/1989
06/10/93
5/24/1996
5/25/1996
09/14/82
03/22/83
Active
Mine
Emissions
(mmcfd)
0.75
0.75
0.35
0.35
2.2
0.35
0.35
2.2
2.2
0.35
0.75
0.75
2.2
2.2
1.4
1
0.35
0.3
1.1
0.75
1.3
1.8
0.35
2.2
1.5
0.35
2.1
2.9
4.2
5.3
2.2
2.2
A-8
US Environmental Protection Agency

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        APPENDIX A.  U. S. Abandoned Coal Mine Database
State
WV
vw
CO
CO
CO
CO
CO
CO
CO
CO
CO
CO
CO
CO
CO
CO
CO
CO
CO
NM
NM
UT
UT
UT
UT
UT
UT
UT
UT
UT
UT
UT
UT
UT
UT
AL
AL
AL
AL
AL
AL
AL
AL
AL
AL
AL
County
Preston
Taylor
Delta
Delta
Delta
Gunnison
Gunnison
Gunnison
Mesa
Mesa
Moffat
Pitkin
Pitkin
Pitkin
Pitkin
Pitkin
Fremont
Las Animas
Las Animas
Colfax
Colfax
Carbon
Carbon
Carbon
Carbon
Carbon
Carbon
Carbon
Carbon
Carbon
Carbon
Carbon
Emery
Grand
Sevier
Jefferson
Jefferson
Jefferson
Jefferson
Jefferson
Jefferson
Jefferson
Jefferson
Shelby
Shelby
Walker
Coal Basin
Northern
Appl.
Northern
Appl.
Piceance
Piceance
Piceance
Piceance
Piceance
Piceance
Piceance
Piceance
Piceance
Piceance
Piceance
Piceance
Piceance
Piceance
Raton
Raton
Raton
Raton
Raton
Uinta
Uinta
Uinta
Uinta
Uinta
Uinta
Uinta
Uinta
Uinta
Uinta
Uinta
Uinta
Uinta
Uinta
Warrior
Warrior
Warrior
Warrior
Warrior
Warrior
Warrior
Warrior
Warrior
Warrior
Warrior
Mine Name
#3 Mine
Keg No 1
Hawks Nest East
Somerset Mine
Bowie No 1
Bear Creek Mine
BEAR MINE
Bear No 3
Roadside North Portal
Roadside South Portal
Eagle No 5
COAL BASIN
L.S.Wood
Thompson Creek No. 1
Dutch Creek No. 2
Dutch Creek No 1
Southfield Mine
Allen
Golden Eagle
York Canyon Mine
Cimarron
Carbon No 2
Kennilworth
Braztah No 3
Price River No. 3
Price River No. 5
Beehive
Castle Gaste Portal #5
Sunnyside Mine No. 3
Castle Gate Mine
Sunnyside Mine No. 1
Soldier Canyon
Trail Mountain Mine
Wilberg
Emery
Flat Top
Bessie Mine
Concord No 1
Mulga
MAXINE MINE
NEBOMINE
Chetopa
Blue Creek No. 3
Segco No 2
BOONE NO. 1
Gorges No 7
Current Emissions
Status
Sealed

Venting
Sealed
Venting Methane

Sealed
Flooded
Sealed
Venting/
Partially Flooded

Sealed
Sealed
Sealed
Sealed
Sealed


Sealed/
Recovering Methane

Sealed

Sealed



Sealed
Sealed
Sealed
Sealed
Sealed
Venting

Sealed
Sealed
Flooded

Flooded
Flooded
Flooded
Flooded
Flooded
Sealed/
Recovering Methane
Flooded

Flooded
Date
Abandoned
07/19/83
11/15/82
1/3/1986
2/16/1989
12/10/1998
10/12/79
05/27/82
04/01/97
2/25/2000
4/25/2000
03/04/96
02/27/81
12/02/85
09/01/86
7/1/1988
10/4/1992
5/10/2001
06/10/84
5/30/1996
3/3/1986
10/10/98
06/1 0/74
06/10/74
06/10/79
06/10/82
06/10/82
03/27/87
03/31/88
09/20/90
10/23/91
6/27/1994
10/10/1999
6/29/2001
02/05/90
08/01/95
06/10/79
06/10/82
06/10/84
06/10/84
10/02/89
10/02/89
067? 0/96
10/1/1999
06/10/72
12/10/1998
06/10/79
Active
Mine
Emissions
(mmcfd)
2.2
2,2
0.9
0.7
1.2
0.7
0.75
0.35
0.7
0.4
0.35
1.6
2.4
0.35
1.7
2.9
0.35
0.75
4.5
0.3
0.75
0.35
0.75
0.35
0.9
0.3
1.7
1.7
1.7
0.75
1.7
2.6
0.85
1.7
0.35
1
1
4.5
1.2
0.35
0.35
0.75
12.3
0.35
1.3
0.35
US Environmental Protection Agency
A-9

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        APPENDIX A.  U. S. Abandoned Coal Mine Database
State


AL
AL
AL

County

Walker
Walker
Walker

Coal Basin

Warrior
Warrior
Warrior

Mine Name

Segco No 1
Mary Lee No 2
Mary Lee No 1

Current Emissions
Status

Flooded
Flooded
Flooded

Date
Abandoned

06/1 0/84
06/10/93
5/10/1997
Active
Mine
Emissions
(mmcfd)
0.75
0.35
1.5
A-10
US Environmental Protection Agency

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APPENDIX B. State Agencies and Organizations with Information on
                    Abandoned Coal  Mines and Regulations
Geological Survey of Alabama
420 Hackberry Lane (W.B. Jones Hall)
The University of Alabama
Tuscaloosa, Alabama 35486-6999
(205) 349-2852


Colorado Department of Natural Resources
Division of Minerals and Geology
1313 Sherman St., Rm. 215
Denver, CO 80203
(303) 866-3567
Illinois Department of Natural Resources
Illinois Office of Mines and Minerals
300 W. Jefferson, Suite 300
Springfield, IL 62701-1787
(217)782-6791
Illinois State Geological Survey
615 E. Peabody
Champaign, IL 61820
(217)333-4747
Ohio Department of Natural Resources
Division of Mines and Reclamation
1855 Fountain Square, Bldg. H-3
Columbus, Ohio 43224
(614) 265-6633

Pennsylvania Dept. of Environmental Protection
Bureau of Abandoned Mine Reclamation
Rachel Carson State Office Building
PO Box 8476
Harrisburg, PA 17105-8476
(717)783-2267

Pennsylvania Dept. of Environmental Protection
Bureau of Abandoned Mine Reclamation
Rachel Carson State Office Building
P.O. Box 8461
Harrisburg, PA  17105-8461
(717)787-5103

Utah Department of Natural Resources
Division of Oil, Gas, and Mining
Abandoned Mine Reclamation
1594 West North Temple, Suite 1210
P.O. Box 145801
Salt Lake City, Utah 84114-5801
(801)538-5349
Indiana Department of Natural Resources
Bureau of Mine Reclamation
402 W. Washington St., Rm. W295
Indianapolis, IN 46204
(317)232-1547

Geological Survey
Indiana University
Energy Resources Division
611 North Walnut Grove
Bloomington, IN 47405-2208
(812)855-7636


Kentucky Department of Mines and Minerals
P.O. Box 2244
Frankfort, KY 40602
(502) 573-0140
Virginia Dept. of Mines, Minerals, and Energy
PO Box 900
U.S. Route 23 South
Big Stone Gap, VA24219
(540)523-8100


West Virginia Dept. of Environmental Protection
Office of Abandoned Mine Lands & Reclamation
PO Box 6064, NRCCE Bldg.
Morgantown, WV 26505
(304) 293-2867 ext. 5460


West Virginia Dept. of Environmental Protection
Office of Mining & Reclamation
10 McJunkin Road
Nitro, WV 25143
(304)759-0510
US Environmental Protection Agency
                                       B-1

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   Appendix C. Combining Uncertain Parameters Using Monte Carlo
                                     Simulation


The IPCC guidelines for GHG inventory reporting require that the values be reported to within a
95% confidence interval. In other words, that there is a 95% probability that the true value will lie
within a specified interval (or, conversely, a 5% chance that the true value will lie outside of this
interval). Because the methodology presented in this report relies on combining variables with
uncertain values, a technique was needed that allowed the statistical uncertainty of those values
to be captured in the calculated abandoned mine methane emission value for a given inventory
year. One way to do this type of analysis is through Monte Carlo simulation.

The purpose of this appendix is to explain the process of combining  probability distributions
within mathematical functions, such as products and sums, using Monte Carlo simulation and to
help provide an understanding of  the nature of the results. The stepwise calculation of the
volume of methane emitted from a vented abandoned mine for the inventory year 1992, and its
associated confidence interval, will be  used as an  example  to illustrate the process. The
methane emissions for several mines will then be summed using Monte Carlo simulation to
provide a frequency distribution, and hence the confidence interval, for the emission inventory of
those abandoned mines.
                                          Figure C-1. Histogram of Gas Content Data and the Best Fit
                                             of the Lognormal Distribution Function to the Data
       Quantifying uncertainty

The term  "variables  with  uncertain
values" means that if the variable of
interest is  measured repeatedly,  the
value of that variable will be different
with   each    measurement.   This
difference   can   be   related   to
measurement   error  or   variations
through time or by sample location. If
the  value   is   measured  numerous
times, the frequency of occurrence of
a value or  range  of values can  be
determined  and  an   experimental
frequency   histogram   is   created.
Figure  C-1  is an  example  of a
frequency histogram of gas content
data from a coal basin in the United States. A continuous probability distribution function can be
fitted to the frequency histogram of the measured data. It is generally the probability distribution
function that is used within mathematical expressions to generate a frequency histogram of the
result. A lognormal distribution  function is the best fit to the histogram in Figure C-1, but there
are several functions available to choose from,  each with a  different general  shape.  The
@Riskฎ add-in to Microsoft Excel  used in this inventory contains a subroutine that fits  a set of
probability distribution functions to the experimental frequency histogram and then ranks each
function by the goodness of fit using three different statistical tests.
                                                            scf/ton
US Environmental Protection Agency
                                                                                   C-1

-------
                                            Figure C-2. Cumulative Probability of Gas Content Data and
                                            Best Fit of the Lognormal Distribution Function to the Data
                                                  X<=7.6                   X<=93.2
                                              	J5.Q%._	               35 Q%
Another way that data distributions are
often  presented is by the cumulative
frequency  diagram.  Figure  C-2 is  a
cumulative frequency diagram of the
data shown in Figure C-1 including the
lognormal    cumulative    probability
function.  Both  of  these  figures show
delimiters  at   the   5%  and   95%
frequency.   The  meaning   of  these
values is best understood from Figure
C-2. The 5% value of 7.6 scf/t means
that 5%  of the  time a sampled value
will be 7.6 scf/t  or less or, conversely,
that 95% of the time a sampled value
will be 7.6 scf/t or  more. There is  a
95% chance that a sampled  value will
be 93.0 scf/t or less,  or a 5%  chance  that it will be 93.0 scf/t or greater. These values represent
the 90% confidence interval. In other  words, there is a 90% chance that a sampled value will lie
between  7.6 and 93.0 scf/t.
                                                            40
                                                                 60
                                                                       80
                                                                                  120
                                                             Gas Content, scf/t
       Methodology review
The methodology for determining the methane emissions from an abandoned underground coal
mine for a particular inventory year uses mathematical prediction techniques based on material
balance and the behavior of  gas flowing  through a porous  adsorptive media,  coal, to the
atmosphere. Section 4.2 in the main body of the report describes how a set of dimensionless
emission rate decline curves  were generated  for  each U.S.  coal  basin based on  these
principles. These decline curves were then fitted to a hyperbolic equation of the form:
                                                 (-1/b)
Where:
                                       = (1+bD|t)
              q is the gas rate at time t in mmcf/d
              q, is the initial gas rate at time zero (t0) in mmcf/d
              b is the hyperbolic exponent, dimensionless
              Di is the initial decline rate,
1/day
t is elapsed time from t0, days

Based on these decline curves and the
time since abandonment, the emissions
for  a   given   inventory   year   are
determined.
       Using probability
       distributions as variables
A  single value of the yearly emissions
can be calculated from the single values
of the initial emission rate and the decline
                                                Figure C-3. Uncertainty of the Initial Emission Rate at
                                                         Abandonment for a Mine
                                                  X <=0 7000
                                                    2.5%
                                                                 mrncf/d
C-2
                                                        US Environmental Protection Agency

-------
coefficients, b  and Dj.  The initial emission  rate (qi),  however, is uncertain. The  measured
emissions have an estimated uncertainty of plus 10% and minus 30% within a 95% confidence
interval (as discussed in  Section 4.4.4). In the example above, the  measured emissions at
closure was 1.0  mmcf/d, plus 0.1  mmcf/d  or  minus 0.3 mmcf/d. This  information can  be
characterized as a triangular probability function with a mean value of 0.925 as shown in Figure
C-3. Using  this function in place of the single  value for initial  emission  rate will result in a
frequency histogram of the yearly methane emission for this mine in 1992.

Unfortunately, the initial emission rate is not the only uncertainty in the hyperbolic equation. The
hyperbolic  decline  coefficients are also uncertain. The decline coefficients for the Central
Appalachian Basin are listed in Table C-1. The low, mid and high cases relate to low, mid and
high permeability uncertainty (see section 4.4.2). The range of values is not meant  to capture
the extreme values,  but  values that represent the  highest  and lowest quartile of the  data
distribution.  These are specified as the values at the ten-percentile and the ninety-percentile of
the cumulative probability function of the parameter.
Table C-1. Central Appalachian Hyperbolic Decline
Coefficients
Case
Low(P10)
Mid (P50)
High (P90)
b
1.079
1.834
1.014
Di, 1/day
0.00892
0.00874
0.00077
Figure  C-4 shows the  three emissions decline profiles based  on these coefficients for the
example mine data in Table C-2. Given an abandonment date and an emission rate at the time
of closure, as in Table C-2, the mid-range case emission estimate for the inventory year 1992
can be calculated using the following function.
                 q = 63.4 = 365 * 0.925 (1+1.83 * 0.0087 * 1278)
                                                                 (-1/1.83)
Table C-2. Sample inventory calculation for a vented mine

Coal
Basin
CA

Mine Name
Example

Status
Venting

Date of
Abn.
06/21/88
Active
Mine
Emissions
(mmcf/d)
0.925
Time
Since
Closure,
days
1278

Mid
Emission
(mmcf/yr)
63.4

High
Emission
(mmcf/yr)
170.7

Low
Emission
(mmcf/yr)
30.7
Calculating    the    emission    rate
probability function  for the  low, mid or
high permeability case for an inventory
year  can  be  done   on   a  personal
computer using a spreadsheet program
with "add-in'  Monte  Carlo simulation
software  such  as   @Riskฎ.   The
software randomly  selects  a value for
the initial emission rate variable based
on   the  probability   of   this  value
occurring as described by the triangular
probability function  (Figure C-3). This
value is used to calculate a  value of the
mmcf/year
~" ฐ ^
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•-• Mid Permeability
••*••• Low Permeability




f~-#-~~ซ_
•••^!™,.4,,.v

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0 1000 2000 3000 4000 5000 6000 7000 8000 9000 10000
Days Since Abandonment
US Environmental Protection Agency
C-3

-------
yearly emissions for the inventory year of interest. This sampling process is repeated numerous
times (the number of times is set by the user) producing the probability function for the emission
rate  for that inventory  year. This is shown by Figure  C-5,  which represents sampling  the
triangular probability function and calculating the result 5,000  times for the  low, mid and high
emissions  estimates shown  in  Table  C-2.  Each  of  the forecasted  distributions  has  an
uncertainty range of plus 10% and minus 30% relative to the mode as shown in Table C-3.
Table C-3. 95% confidence intervals and percent difference for example mine emissions for 1992
by permeability case, mmcf
Case
Low Permeability
Mid Permeability
High Permeability
P2.5%
48.0
23.2
129.2
Mode
68.1
33.1
184.3
P97.5%
75.4
36.5
203.0
% Difference Low
-30%
-30%
-30%
% Difference High
10%
10%
10%
                                             Figure C-5. Yearly Emission Volumes Based on
                                          Permeability and Emission Rate At Closure Uncertainties
                                      0.35
                                                                             200
                                                              mmcf/yr
       Distributions within
       distributions
In  order  to  generate   a  single
probability  density  function of the
emissions  for this  mine for 1992,
the low,  mid and high distributions
need  to be combined.  Here the
probability  density function depicts
the frequency of occurrence of the
range of values that potentially may
occur, plotted versus the probability
of any  given outcome  occurring.
Generating  this  probability density
function    is   accomplished   by
selecting  the  low,  mid  and high
emission distributions as  the low,
mid and high points in another triangular distribution shown in Figure C-6. The endpoints (which
are specified as the means of each distribution) are defined as the P10, mode and P90 because
this is how the permeability ranges were characterized when generating the decline curves. A
                                                       condition  must  be applied to this
                                                       distribution  so  that  no  negative
                                                       emission values are returned in the
                                                       final    distribution.    The    final
                                                       distribution is shown in Figure C-7.
                                                       This  distribution  shows  that  the
                                                       emission for  inventory year 1992 is
                                                       between 12.3 and 210.7 mmcf at a
                                                       95%  confidence  interval  with  a
                                                       mean of 96.5 mmcf. This is a range
                                                       of  plus  118% and  minus   87%
                                                       relative  to   the   mean   of   the
                                                       distribution. Figure C-8  shows the
                                                       mean    predicted   for    yearly
                                                       emissions  for this mine  with  the
                                                       95% confidence interval.
      Figure C-6. Static Triangular Distribution for
                      Uncertainty
                                   150
                                           200
                                                  250
                          mmcf/yr
C-4
                                                         US Environmental Protection Agency

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                         Figure C-7. Initial Rate Distribution and Permeability
                                     Distribution Combined
                                                             X<-2107
                                           100        150

                                              mmcf/yr
                          Figure C-8. Single Abandoned Mine Emissions
                          Uncertainty over Time with Initial Rate Uncertainty
                         0    1000   2000  3000   4000  5000  6000   7000  8000  9000  10000

                                        Days Since Abandonment
       Summing distributions

The probability distribution  of the emissions and their associated confidence  intervals will be
different for each mine  for any given  inventory  year.  Summing  these  distributions  is an
appropriate way  to  determine  the  basin  total  emissions  and  the  associated  uncertainty.
Intuitively,  one might expect that the range  of uncertainty of a combination of highly uncertain
predictions would  yield an even more uncertain result, while,  in fact,  the opposite is true. Table
C-4 lists a subset of vented Central Appalachian basin mines for inventory year 1992 with the
mean value of their calculated yearly emissions, the 2.5% and 97.5% probability values, and
their percent difference  relative  to the mean. The  result of the summed distributions is also
shown on the bottom line of Table C-4. The sum of the mean values for each  mine's emission
distribution is the  same as the mean of the  summed distributions. However, the summation of
the values of the 2.5%  probabilities is  much smaller than the 2.5%  probability value of the
summed distributions.  Similarly, the sum of the 97.5% probability values is much larger than the
97.5% probability  value of the summed distributions.  The range of uncertainty of the summed
distributions is significantly  smaller than the range of uncertainty of  the individual distributions
for a given confidence interval.
US Environmental Protection Agency
C-5

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Table C-4. Partial list or Central Appalachian abandoned coal mines and their mean emission
estimate with the 95% confidence interval bounding values
Mine Name
Cannelton No 8
U.S. Steel No 14-4
Maitland
Beckley No 2
Beckley No 1
Kepler
Newhall No 6 Mine
Sewell No 4
Sums (
of Values
Sum of
Distributions
Mean
18.6
52.1
37.3
89.4
34.3
19.4
21.1
14.9
287.2
287.2
2.5%
Prob.
1.8
4.9
3.5
10.6
3.3
1.9
2.0
1.5
29.0
165.4
97.%
Prob.
40.8
113.1
81.2
195.3
76.0
41.7
45.6
31.5
625.2
429.6
%Diff
Low
-90%
-91%
-91%
-88%
-90%
-90%
-91%
-90%

-42%
%Diff
High
119%
117%
118%
118%
121%
115%
116%
112%

50%
Std
Dev
10.4
28.8
20.8
49.6
19.3
10.6
11.8
8.1

68.0
Coefficient of
Variation
56%
55%
56%
55%
56%
55%
56%
54%

24%
Conclusions

This process may seem counterintuitive. For example, an individual mine in Table C-4 (Beckley
#1) located in the Central Appalachian Basin had an uncertainty range of plus 121% and minus
90% for the 1992 inventory. After that mine is combined into a larger group of mines (classified
by coal basin), the resulting range of uncertainty for the Central Appalachian Basin mine group
is plus 41% and minus 32%.  Furthermore, the range of uncertainty associated with the entire
population of abandoned mines compiled for the 1992 inventory results in an even lower range
of plus or minus 20%  The above example illustrates the phenomenon, supported by the central
limits theorem, that the coefficient of variation (standard deviation divided by the mean) of the
sum of distributions is smaller than the coefficient of variation of the component distributions.
C-6
US Environmental Protection Agency

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                 APPENDIX D.  Effect of Barometric Pressure

During the spring of 1999,  EPA collected gas flow and quality data from an abandoned mine
vent in the Illinois basin to  correlate flow rates with barometric pressure.39 The mine selected
for the  study had  been closed since  1962,  but  a three-inch  vent  pipe  remained intact  and
continued to vent  methane into the atmosphere. This mine  is considered  representative of
gassy abandoned mines in the Illinois basin region.40

Figure  D-1, which shows all three  data sets taken, clearly  illustrates the strong inverse
relationship between barometric pressure  and methane emissions from the mine vent.  As
barometric pressure increases, mine emissions decrease.  As the graph illustrates, the 72-hour
and 96-hour studies  resulted  in  roughly the same average emission rate.   Based on  these
measurements, EPA determined that 72-hour flow measurements are sufficient for determining
a mine's average flow rate.41

     Figure D-1. Illinois Basin field measurements of barometric pressure and mine emissions
                                                        Methane Emissions
                                                        Barometric Pressure
                                                                         30.053
                3-Mar-99  4-Mar-i
                             6-Mar-99  7-Mar-99  8-Mar-99  17-Mar-99  18-Mar-99  19-Mar-99  20-Mar-9

                                           DATE
Correlating gas flow  rates to barometric pressure is  critical  for obtaining  representative field
measurements for decline curve validation. The correlation between gas flow and barometric
pressure is shown  in  Figure D-2. The  linear regression equation describing the relationship
resulted in  a correlation coefficient (R2) equal to 0.92.
39 Flow measurements were recorded at the vent pipe every hour over three 2-4 day periods to determine
the minimum time necessary to obtain representative emissions data.  Corresponding hourly barometric
pressure data obtained from the Midwestern Climate Center indicates that the average annual barometric
pressure for this county was 30.03 inches of mercury. Variations in barometric pressure during the study
were typical of the annual variation. The calculated average methane emissions rate for the  vent pipe
equaled 316.5 mcfd; daily readings ranged from 195 to 365 mcfd.
40 This mine is of room and pillar type, 500 to 600 feet deep, and includes the Herrin #6 coal seam.
41 Daily variations in the flow rate mean that daily measurements may not be reflective of the average flow
rate.
US Environmental Protection Agency
D-1

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For this  study, only field-measured gas flow rates were normalized  to  account for  average
annual barometric pressure.  Emission rates derived from numerical modeling were based on a
constant barometric pressure of one atmosphere.

Ideally, one would measure diffuse emissions from sealed mines, through surface cracks and
fissures,  to  more accurately determine the degree to which mines  are sealed (referred to  in
terms of  percentage sealed). Some techniques exist to measure these diffuse emissions (e.g.,
using infrared detectors), but resource limitations prohibited their use for this study.

Of the 374 mines in the U.S. abandoned mines database, only about 14%  maintain vents to the
atmosphere. Therefore,  basing  emissions estimates on  field  data  alone would  result in an
unrepresentative and biased estimate.  Therefore, additional field  measurements could be used
to further  calibrate  emission estimates.   It would be  particularly  useful to  extend  such
measurements to sealed mines since they comprise such  a significant  component of the
inventory.
       Figure D-2. Correlation between mine methane emissions and barometric pressure
            01
            c
            .0
            '
            .2

            UJ

            O
400 -


375


350 -


325


300


275


250


225


200


175
              150

                 ' Predicted CH,
                  emissions from
                  measured mine vent
                                   Average annual barometric
                                   pressure at abandoned mine
                                   site
                                30    301   30.2   30.3    30.4

                                     Barometric Pressure (in. Hg)
D-2
                                           US Environmental Protection Agency

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               Appendix E.  Sensitivity Analysis Calculations
To test the sensitivity of emissions calculations to three parameters (adsorption isotherm, as
represented by VL and PL, permeability, and pressure at abandonment) involves 27 calculations
for each  mine for each inventory year, since three values of each parameter must be tested
(high, low,  and  mid-range). A sensitivity analysis was performed to determine if the range of
uncertainty of these three  parameters is large enough to make a significant difference  in the
outcome  of the calculation. If a parameter does not have a significant effect on the outcome, the
probability analysis is not necessary and the mid-case value of the parameter can be used in
the calculations.

To test the sensitivity of  the  calculations to the range  of uncertainty,  seven  cases  were
generated using the values shown in Table E-1. Gas content of coal mines at low pressures is
most sensitive to the value of the Langmuir Pressure, to  which it is inversely proportional. The
Langmuir Volume has little effect.
Table E-1. Parameter values used in sensitivity analysis
Parameter
Permeability, md
Pressure, psia
PL. psia
V, . scf/ton
High
10
30
176
712
Mid
1
20
286
911
Low
0.1
17
667
1093
These  values were combined and used in the CFD model to calculate an emission inventory
number using a set of mine data from the Central Appalachian basin. Table E-2 lists the results,
which are shown graphically in Figure E-1. The mine is assumed to be emitting methane to the
atmosphere through one or several vents as opposed to being sealed or flooded.

                  Table E-2. Results of parameter sensitivity test
Permeability
High
Mid
Low
Mid
Mid
Mid
Mid
Pressure
Mid
Mid
Mid
High
Low
Mid
Mid
Isotherm
Mid
Mid
Mid
Mid
Mid
High
Low
Emissions,
Bcf/yr
8.877
4.259
1.627
4.970
4.049
4.504
3.546
US Environmental Protection Agency
E-1

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 Figure E-1. Range of uncertainty for 1990 methane emissions for the Central Appalachian basin
                              associated with key parameters.
10 -
9 -
8 -
7 -
6 -
? 5
m
4 -
3 -
2 -
1 '

\






I
1 8.877 |



V 4.504 i
•4.049 .... i - i
• 3.546 I

11.627 !

Permeability Pressure Isotherm
Figure E-1 shows that the calculated emissions for 1990 for the Central Appalachian basin are
much more sensitive to permeability than to either initial pressure or the adsorption isotherm.
Inventory  calculations, therefore, use  mid-case values for  initial pressure  and the mid-case
basin isotherm, but include the range of values for permeability for the probabilistic analysis.
E-2
US Environmental Protection Agency

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 APPENDIX F. Emissions Inventory: Sample Calculations According To
                                    Mine Types

 Venting Mines

 The low, mid and high emission calculations are based on decline equations derived from the
 simulation model using the mid case  adsorption  isotherm for the basin,  using permeability
 values of 1.0, 10.0 and 0.1  md,  respectively. Table F-1 shows the results from the spreadsheet
 for the year 2000 inventory.

               Table F-1. Sample inventory calculation for a venting mine
Coal
Basin
Central
Appl.
Mine Name
Cannelton
No 8
Status
Venting
Date of
Abn.
04/05/83
Active
Mine
Emissions
(mmcf/yr)
323.644
Time
Since
Closure,
days
6480
Mid
Emission
(mmcf/yr)
9.349
High
Emission
(mmcf/yr)
20.146
Low
Emission
(mmcf/yr)
3.533
The mid case equation for Central Appalachian Basin (shown below) is based on Equation 4:
                   q = 9.349 = 323.64(1+1.83 * 0.0087 * 6480)H/1 83)

Different decline curve equation sets are used for each coal basin, because each basin has a
unique adsorption isotherm, which affects the decline curves calculated for each permeability
value.

The  resulting three emissions estimates for each basin are then  used  to define a  triangular
distribution for each mine (Figure F-1). The 10% and 90% probabilities shown in Table F-1 and
Figure F-1 are used to represent the lower and upper quartiles of the distribution.

This  methodology uses the entire triangular distribution of emissions for each mine as input for a
Monte Carlo simulation. This produces a probability distribution  of emissions for the population
of all venting abandoned mines (Figure F-2).

The frequency histogram shown in Figure F-2 is the result of randomly sampling the  triangular
distribution of emissions for each  mine (e.g., in Figure F-1) one thousand times and adding
them together. Additional trials did not significantly change the mean or the variance of the
distribution. The brackets on the x-axis show the 95% certainty bounds.
US Environmental Protection Agency
F-1

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          Figure F-1. Distribution of Year 2000 Emissions for a vented abandoned mine
                      Cannelton # 8 Mine, Central Appalachian Basin
                    X<=3.533                           X<=20.146

                                                         90JD3L
                          5.0
                                    10.0        15.0        20.0


                                   Emissions for Year 2000 in mmcf
                                                                    25.0
                                                                              30.0
Figure F-2. Probability density function for vented abandoned mines emissions for the year 2000
                     Distribution for Known Vented Mines for Year 2000
                           X<=2.112                          X<=3.425

                             2.5%                            97.5%
            E
            0>

            cr
            o>
              1.5
2.5           3.0


 Values in Bcf
                                                                 3.5
                                                                              4.0
F-2
                  US Environmental Protection Agency

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Flooded Mines

The calculation procedure  for flooded, but still venting, mines  is very similar to that for dry
venting mines except that an exponential function is used rather than a hyperbolic function. For
the mid-range case shown in Table F-2 below, emissions are calculated using Equation 5:
                                      q = q,e
                                              (-Dt)
                           0.223 = 1022exp(- 0.672(4580/365))

For flooded mines, the exponential constant D in Equation 5 is the same for all basins because
it is a simple empirical curve fit to measured data. The low, mid and high emission values, as
shown in Table F-2, are used to define a triangular distribution. The triangular distributions for
all flooded mines are summed to generate a probability distribution for the emissions inventory
for the year 2000 (Figure F-3).
               Table F-2. Sample inventory calculation for a flooded mine
Coal
Basin
Central
Appl.
Mine
Name
Ogla
Status
Flooded
Date of
Abn.
06/17/88
Active
Mine
Emissions
(mmcf/yr)
1022
Time Since
Closure,
days
4580
Mid
Emission
(mmcf/yr)
0.206
Low
Emission
(mmcf/yr)
0.039
High
Emission
(mmcf/yr)
1.106
        Figure F-2. Probability density function for flooded abandoned mines emissions
                                    for the year 2000
                      Distribution for Known Flooded Mines for Year 2000
                             X<=229.48                    X<=374.53
                         200
                                  250
                                            300

                                       Values in mmcf
                                                     350
                                                               400
                                                                        450
US Environmental Protection Agency
F-3

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Sealed Mines

The sealed mine calculations average the low, mid-range, and  high emission factors based on
the permeability uncertainty for each  of the "percent sealed" cases of 50%, 80%, and 95%.
Here, the 80% sealed case is treated  as  the most likely or mid-range case. The average
emission factor for each of the three values of percentage sealed is used to define a triangular
distribution, which  is then used in the Monte Carlo simulation to create a  probability density
function for emissions from sealed abandoned mines. The probability density plot for the year
2000 emissions inventory for sealed mines is shown in Figure F-4.

  Figure F-4. Probability density function for year 2000 emissions from sealed abandoned mines
                      Distribution for Known Sealed Mines for Year 2000
                              X<=4.415                    X<=6.684
                                                       ,,,....97,5%	
              o

              flj

              CT
              0)
                3.0
                      3.5
                           4.0
                                 4.5
                                       5.0    5.5    6.0
                                         Values in Bcf
                                                        6.5
                                                             7.0
F-4
US Environmental Protection Agency

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