Southern Ute Indian Reservation (2015)

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2015

Southern Ute Indian Reservation

Emission Inventory

Southern Ute Indian Tribe

Environmental Programs Division – Air

Quality Program

71 Mike Frost Way

Ignacio, Colorado 81137

________________________________________________________________

Final Report for 2015 Southern Ute Indian Tribe

Comprehensive Emissions Inventory for Criteria

Pollutants, Hazardous Air Pollutants, and Greenhouse

Gases

__________________________________________________________________

Prepared by:

Southern Ute Indian Tribe

Environmental Programs Division

Air Quality Program

P.O. Box 737, MS# 84

Ignacio, Colorado 81137

(970) 563-4705

Oil and gas emission calculations prepared by Oakley Hayes, Air Quality Scientist

Non-oil and gas emissions calculations prepared by Matt Wampler, Air Quality Analyst

Emission Inventory Report prepared by Danny Powers, Air Quality Technical Manager

May, 2017

Table of Contents

Table of Figures............................................................................................................................. 3

List of Acronyms ........................................................................................................................... 9

Executive Summary ............................................................................................................ 11

II. Overview .............................................................................................................................. 12

Purpose of Inventory .................................................................................................. 12

Geographic Location of Southern Ute Indian Reservation ........................................ 12

Climate........................................................................................................................ 13

Geology ...................................................................................................................... 13

Sources........................................................................................................................ 13

III.

Data Quality Objectives .................................................................................................. 14

Accuracy ..................................................................................................................... 14

Uncertainty ................................................................................................................. 15

Completeness .............................................................................................................. 15

Comparability ............................................................................................................. 15

IV.

Point Sources .................................................................................................................... 15

Title V Oil and Gas Sources ....................................................................................... 15

Minor Point Sources ................................................................................................... 20

Landfill Gas ................................................................................................................ 30

Airports ....................................................................................................................... 33

Non-Point Sources ............................................................................................................... 35

Non-registered Oil and Gas Sources .......................................................................... 35

Fruitland Formation Outcrop Natural Gas Seeps ....................................................... 74

Gas Stations ................................................................................................................ 76

Aviation Gasoline ....................................................................................................... 78

Gravel Pits .................................................................................................................. 79

Residential Heating..................................................................................................... 80

Wildland Fires and Prescribed Burns ......................................................................... 84

Agricultural Burning................................................................................................... 87

VI.

Mobile Sources ................................................................................................................. 88

On-Road Mobile Sources ........................................................................................... 88

Non-Road Mobile Sources ......................................................................................... 89

VII. Biogenic ............................................................................................................................. 90

VIII.

Summary ....................................................................................................................... 91

IX.

Bibliography ................................................................................................................... 103

Appendix – Quality Assurance Review ........................................................................... 106

Table of Figures

Figure 1 – 2015 Total Criteria Pollutant and HAP Emission on the Southern Ute Indian Reservation in Tons per Year

.....................................................................................................................................................................................12

Figure 2 – 2015 Title V Oil and Gas Source Criteria Pollutant and GHG Emissions Estimations for the Southern Ute

Indian Reservation in Tons per Year ............................................................................................................................16

Figure 3 – 2015 Title V Oil and Gas Source Criteria Pollutant Emissions on the Southern Ute Indian Reservation in

Tons per Year ...............................................................................................................................................................17

Figure 4 – 2015 NOx Emissions at Title V Oil and Gas Sources on the Southern Ute Indian Reservation by Equipment

Type in Tons per Year ..................................................................................................................................................17

Figure 5 – 2015 VOC Emissions at Title V Oil and Gas Sources on the Southern Ute Indian Reservation by Equipment

Type in Tons per Year ..................................................................................................................................................18

Figure 6 – 2015 Title V Oil and Gas Source Hazardous Air Pollutant Emissions on the Southern Ute Indian

Reservation in Tons per Year .......................................................................................................................................18

Figure 7 – 2015 Title V Oil and Gas Source Hazardous Air Pollutant Emissions on the Southern Ute Indian

Reservation in Tons per Year .......................................................................................................................................19

Figure 8 – 2015 Hazardous Air Pollutant Emissions at Title V Oil and Gas Sources on the Southern Ute Indian

Reservation by Equipment Type in Tons per Year .......................................................................................................19

Figure 9 – 2015 Greenhouse Gas Emissions at Title V Oil and Gas Sources on the Southern Ute Indian Reservation

by Equipment Type in Tons per Year ...........................................................................................................................20

Figure 10 – 40 CFR Part 49 Minor New Source Review Program Emissions Thresholds in Tons per Year ..................21

Figure 11 – 2015 Criteria Pollutant and HAP Emissions for Permitted Tribal Minor New Sources Review Oil and Gas

Sources on the Southern Ute Indian Reservation in Tons per Year .............................................................................22

Figure 12 – 2015 Criteria Pollutant and HAP Emissions for Permitted Tribal Minor New Sources Review Oil and Gas

Sources on the Southern Ute Indian Reservation in Tons per Year .............................................................................23

Figure 13 – 2015 NOx Emissions for Permitted Tribal Minor New Sources Review Oil and Gas Sources on the

Southern Ute Indian Reservation in Tons per Year .....................................................................................................23

Figure 14 – 2015 VOC Emissions for Permitted Tribal Minor New Sources Review Oil and Gas Sources on the

Southern Ute Indian Reservation in Tons per Year .....................................................................................................24

Figure 15 – 2015 Total HAP Emissions for Permitted Tribal Minor New Sources Review Oil and Gas Sources on the

Southern Ute Indian Reservation in Tons per Year .....................................................................................................24

Figure 16 – 2015 Speciated HAP Emissions for Permitted Tribal Minor New Sources Review Oil and Gas Sources on

the Southern Ute Indian Reservation in Tons per Year ...............................................................................................25

Figure 17 – 2015 Speciated HAP Emissions for Permitted Tribal Minor New Sources Review Oil and Gas Sources on

the Southern Ute Indian Reservation in Tons per Year ...............................................................................................25

Figure 18 – 2015 GHG Emissions for Permitted Tribal Minor New Sources Review Oil and Gas Sources on the

Southern Ute Indian Reservation in Tons per Year .....................................................................................................26

Figure 19 – 2015 Criteria Pollutant and HAP Emissions from Registered TMNSR Oil and Gas Source on the Southern

Ute Indian Reservation in Tons per Year .....................................................................................................................27

Figure 20 – 2015 Criteria Pollutant and HAP Emissions from Registered TMNSR Oil and Gas Sources on the

Southern Ute Indian Reservation in Tons per Year .....................................................................................................28

Figure 21 – 2015 Total NOx Emissions for Registered Tribal Minor New Sources Review Oil and Gas Sources on the

Southern Ute Indian Reservation by Equipment Type in Tons per Year .....................................................................28

Figure 22 – 2015 Total VOC Emissions for Registered Tribal Minor New Sources Review Oil and Gas Sources on the

Southern Ute Indian Reservation by Equipment Type in Tons per Year .....................................................................29

Figure 23 – 2015 Total HAP Emissions for Registered Tribal Minor New Sources Review Oil and Gas Sources on the

Southern Ute Indian Reservation by Equipment Type in Tons per Year .....................................................................29

Figure 24 – 2015 Total GHG Emissions for Registered Tribal Minor New Sources Review Oil and Gas Sources on the

Southern Ute Indian Reservation by Equipment Type in Tons per Year .....................................................................30

Figure 25 – 2015 Municipal Solid Waste Landfill Refuse in Place in Tons and Emissions on the Southern Ute Indian

Reservation in Tons per Year ......................................................................................................................................33

Figure 26 – 2015 Municipal Solid Waste Landfill Refuse in Place in Tons and Emissions on the Southern Ute Indian

Reservation in Tons per Year .......................................................................................................................................33

Figure 27 – 2015 Criteria Pollutant and HAP Emission from Airports on the Southern Ute Indian Reservation in Tons

per Year .......................................................................................................................................................................34

Figure 28 – 2015 Criteria Pollutant and HAP Emissions from Airports on the Southern Ute Indian Reservation in

Tons per Year ...............................................................................................................................................................35

Figure 29 – 2015 Emissions from Non-registered Oil and Gas Sources on the Southern Ute Indian Reservation in

Tons per Year ...............................................................................................................................................................36

Figure 30 – 2015 Criteria Pollutant and HAP Emissions from Non-Registered Oil and Gas Sources on the Southern

Ute Indian Reservation in Tons per Year .....................................................................................................................37

Figure 31 – 2015 NOx Emissions for Non-Registered Oil and Gas Sources on the Southern Ute Indian Reservation by

Equipment Type in Tons per Year ................................................................................................................................37

Figure 32 – 2015 VOC Emissions for Non-Registered Oil and Gas Sources on the Southern Ute Indian Reservation by

Equipment Type in Tons per Year ................................................................................................................................38

Figure 33 – 2015 HAP Emissions for Non-Registered Oil and Gas Sources on the Southern Ute Indian Reservation by

Equipment Type in Tons per Year ................................................................................................................................38

Figure 34 – 2015 GHG Emissions for Non-Registered Oil and Gas Sources on the Southern Ute Indian Reservation

by Equipment Type in Tons per Year ...........................................................................................................................39

Figure 35 – Engines Reported for Non-Registered Oil and Gas Source in the 2016 by Engine Configuration and

Horsepower .................................................................................................................................................................40

Figure 36 – 2015 Natural Gas-Fired Reciprocating Internal Combustion Engine Counts and Criteria Pollutant, HAP,

and GHG Emissions on the Southern Ute Indian Reservation in Tons per Year .........................................................42

Figure 37 – 2015 Natural Gas-Fired Reciprocating Internal Combustion Engine Counts and Criteria Pollutant, HAP,

and GHG Emissions on the Southern Ute Indian Reservation in Tons per Year ..........................................................43

Figure 38 – Oxides of Nitrogen Emissions from Natural Gas-Fired Reciprocating Internal Combustion Engines at

Non-Registered Oil and Gas Sources on the Southern Ute Indian Reservation in Tons per Year ...............................43

Figure 39 – 2015 Volatile Organic Compound Emissions from Natural Gas-Fired Reciprocating Engines at NonRegistered Oil and Gas Sources on the Southern Ute Indian Reservation in Tons per Year .......................................44

Figure 40 – 2015 Carbon Monoxide Emissions from Natural Gas-Fired Reciprocating Engines at Non-Registered Oil

and Gas Sources in Tons per Year ................................................................................................................................44

Figure 41 – 2015 Turbine Count and Total Emissions of Criteria Pollutant, HAP, and GHG at Non-Registered Oil and

Gas Sources on the Southern Ute Indian Reservation in Tons per Year ......................................................................46

Figure 42 – Theoretical Extended Natural Gas Analysis – Average of 34 Natural Gas Analyses from the Southern Ute

Indian Reservation .......................................................................................................................................................47

Figure 43 – 2015 GRI-GLYCalc Model Input Parameters for TEG Dehydration Units at Non-Registered Oil and Gas

Sources on the Southern Ute Indian Reservation........................................................................................................49

Figure 44 – 2015 GRI-GLYCalc Model Emissions Output for TEG Glycol Dehydration Units on the Southern Ute

Indian Reservation in Tons per Year ............................................................................................................................49

Figure 45 – 2015 HAP and VOC Emissions from 51 TEG Dehydration Units at Non-Registered Oil and Gas Sources on

the Southern Ute Indian Reservation ..........................................................................................................................50

Figure 46 – 2015 Liquid Storage Tanks at Non-Registered Oil and Gas Sources on the Southern Ute Indian

Reservation by Tank Contents and Capacity in Barrels ...............................................................................................52

Figure 47 – 2015 Assumed Annual Average Liquid Throughput Values for Produced Water, Oil and Condensate

Tanks at Non-Registered Sources on the Southern Ute Indian Reservation ...............................................................53

Figure 48 – Produced Water Flash Gas Analysis from Non-Registered Oil and Gas Sources on the Southern Ute

Indian Reservation in Mol Percent – September 2016 ................................................................................................55

Figure 49 – Condensate Flash Gas Analysis from Non-Registered Oil and Gas Sources on the Southern Ute Indian

Reservation in Mol Percent – September 2016 ...........................................................................................................56

Figure 50 – Average Gas to Water and Gas to Condensate Ratios for Non-Registered Sources on the Southern Ute

Indian Reservation – September 2016¹ .......................................................................................................................57

Figure 51 – 2015 VOC, HAP, and GHG Emission Totals on the Southern Ute Indian Reservation in Tons per from

Liquid Storage Tanks by Tank Count, Content and Capacity .......................................................................................61

Figure 52 – 2015 VOC, HAP, and GHG Emission Totals on the Southern Ute Indian Reservation in Tons per from

Liquid Storage Tanks by Tank Count, Content and Capacity .......................................................................................61

Figure 53 – Criteria Pollutant, HAP, and GHG Emissions from Heaters and Boilers at Non-registered Oil and Gas

Sources on the Southern Ute Indian Reservation in Tons per Year, Displayed by Unit Count and Heat Rating in

MMBtu/hr....................................................................................................................................................................64

Figure 54 – Assumed Fugitive Emission Component Counts at Single and Co-Located Natural Gas Well-Sites on the

Southern Ute Indian Reservation ................................................................................................................................65

Figure 55 – 2015 Emissions of VOC, HAP, and GHG from Equipment Leaks and Fugitive Emission Sources at NonRegistered Oil and Gas Sources on the Southern Ute Indian Reservation in Tons per Year .......................................67

Figure 56 - 2015 Volatile Organic Compound, HAP, and GHG Emissions from Natural Gas Driven Pneumatic Devices

at Non-Registered Oil and Gas Sources on the Southern Ute Indian Reservation in Tons per Year ...........................69

Figure 57 – Assumed Values for Annual Natural Gas Blowdown Events Occurring at Non-Registered Oil and Gas

Sources on the Southern Ute Indian Reservation in 2015 ...........................................................................................70

Figure 58 – 2015 Volatile Organic Compound, HAP, and GHG Emissions from Natural Gas Blowdowns at NonRegistered Oil and Gas Sources on the Reservation in Tons per Year .........................................................................71

Figure 59 – Wells Completed at Non-Registered Oil and Gas Sources on the Southern Ute Indian Reservation in

2015 .............................................................................................................................................................................72

Figure 60 – 2015 Assumed Values for Well Completion and Recompletion Activities at Non-Registered Oil and Gas

Sources on the Southern Ute Indian Reservation........................................................................................................72

Figure 61 – 2015 Volatile Organic Compound, HAP, and GHG Emissions from Well Completion and Recompletion

Activities at Non-Registered Oil and Gas Sources on the Southern Ute Indian Reservation .......................................73

Figure 62 – 2015 Average Equipment Counts at Single and Co-Located Well-Sites Located at Non-Registered Oil and

Gas Sources on the Southern Ute Indian Reservation in Tons per Year ......................................................................73

Figure 63 – Average Equipment Counts at Non-Registered Oil and Gas Wells by Equipment Type ...........................74

Figure 64 - 2015 Emissions of Methane, CO2, and total GHG in CO2 Equivalence .....................................................75

Figure 65 – 2015 Annual Gasoline Throughput at Gasoline Stations Located on the Southern Ute Indian Reservation

in Gallon per Year ........................................................................................................................................................76

Figure 66 – 2015 Volatile Organic Compound Emissions from Gasoline Dispensing Stations on the Southern Ute

Indian Reservation .......................................................................................................................................................77

Figure 67 – 2015 Volatile Organic Compound and HAP Emissions from Aviation Gasoline on the Southern Ute

Indian Reservation in Tons per Year ............................................................................................................................78

Figure 68 – Emissions of PM10 from Active Gravel Pits on the Southern Ute Reservation in 2015 ...........................80

Figure 69 – 2015 Fireplace and Wood Burning Stove Residential Heating Data for the Southern Ute Indian

Reservation ..................................................................................................................................................................81

Figure 70 – 2015 Criteria Pollutant and GHG Emissions from Fireplaces and Wood Burning Stoves on Southern Ute

Indian Reservation in Tons per Year ............................................................................................................................81

Figure 71 - 2015 Liquid Propane Residential Heating Data for the Southern Ute Indian Reservation ........................82

Figure 72 – 2015 Criteria Pollutant and GHG Emissions from Liquid Propane Gas Heating at Residential Sources on

Southern Ute Indian Reservation in Tons per Year .....................................................................................................83

Figure 73 – 2015 Natural Gas Residential Heating Data for the Southern Ute Indian Reservation ............................84

Figure 74 – 2015 Criteria Pollutant and GHG Emissions from Natural Gas Heating at Residential Sources on

Southern Ute Indian Reservation in Tons per Year .....................................................................................................84

Figure 75 – 2015 Forest Fire Occurrence on the Southern Ute Indian Reservation by Fuels Characteristic

Classification System Fuel Bed Type and Acres Burned ..............................................................................................85

Figure 76 – 2015 Criteria Pollutant, NH3, and GHG Emissions from Prescribed Burns and Wildland Fires within the

Exterior Boundaries of the Southern Ute Indian Reservation in Tons per Year ..........................................................86

Figure 77 – 2015 Criteria Pollutant, NH3, and HAP Emissions from Agricultural Burning on the Southern Ute Indian

Reservation in Tons per Year .......................................................................................................................................87

Figure 78 – 2015 Criteria Pollutant Emissions from On-Road Mobile Sources on the Southern Ute Indian

Reservation in Tons per Year .......................................................................................................................................89

Figure 79 – 2015 Criteria Pollutant Emissions from Non-Road Mobile Sources on the Southern Ute Indian

Reservation in Tons per Year .......................................................................................................................................90

Figure 80 – 2015 Criteria Pollutant and HAP Emissions from Biogenic Sources on the Southern Ute Indian

Reservation in Tons per Year .......................................................................................................................................91

Figure 81 – 2015 Criteria Pollutants, HAP and GHG Emissions on the Southern Ute Indian Reservation in Tons per

Year ..............................................................................................................................................................................93

Figure 82 – 2015 NOx Emissions on the Southern Ute Indian Reservation by Source Category in Tons per Year .....94

Figure 83 – 2015 VOC Emissions on the Southern Ute Indian Reservation by Source Category in Tons per Year ......95

Figure 84 – 2015 Table of Emissions from Oil and Gas Sector Sources on the Southern Ute Indian Reservation in

Tons per year ...............................................................................................................................................................96

Figure 85 – 2015 Chart of Emissions from Oil and Gas Sector Sources on the Southern Ute Indian Reservation in

Tons per year ...............................................................................................................................................................97

Figure 86 – 2015 Chart of NOx Emissions from Oil and Gas Sector Sources on the Southern Ute Indian Reservation

in Tons per year ...........................................................................................................................................................97

Figure 87 – 2015 Chart of CO Emissions from Oil and Gas Sector Sources on the Southern Ute Indian Reservation in

Tons per year ...............................................................................................................................................................98

Figure 88 – 2015 Chart of VOC Emissions from Oil and Gas Sector Sources on the Southern Ute Indian Reservation

in Tons per year ...........................................................................................................................................................98

Figure 89 – 2015 Chart of HAP Emissions from Oil and Gas Sector Sources on the Southern Ute Indian Reservation

in Tons per year ...........................................................................................................................................................99

Figure 90 – 2015 Chart of GHG Emissions from Oil and Gas Sector Sources on the Southern Ute Indian Reservation

in Tons per year ...........................................................................................................................................................99

Figure 91 – 2015 Natural Gas-Fired Reciprocating Internal Combustion Engine Counts and Emissions in Tons per

Year on the Southern Ute Indian Reservation ...........................................................................................................100

Figure 92 – Comparison of NOx and VOC Emission Estimations for the Southern Ute Indian Reservation from the

2015 SUIT EI and the 2006 WRAP EI in Tons per year ...............................................................................................101

List of Acronyms

AP-42

EPA Compilation of Air Pollutant Emission Factors

API

American Petroleum Institute

AQP

Air Quality Program

BIA

United States Bureau of Indian Affairs

BSFC

Brake Specific Fuel Consumption

bbl

Barrel (42 U.S. Gallons)

CAA

Clean Air Act

CARMMS

Colorado Air Resource Management Modeling Study

CDPHE

Colorado Department of Health and Environment

CNG

Compressed Natural Gas

Carbon Monoxide

CO2e

Carbon Dioxide Equivalent

COGCC

Colorado Oil and Gas Conservation Commission

Calendar Year

CFR

Code of Federal Regulations

DRMS

Colorado Division of Reclamation Mining and Safety

Emissions Inventory

EIA

Environmental Impact Assessment

EPA

United States Environmental Protection Agency

FAA

Federal Aviation Administration

GHG

Greenhouse gas

GSJB

Greater San Juan Basin

HAP

Hazardous Air Pollutants

Horse Power

H2S

Hydrogen Sulfide

ICR

Information Collection Request

ITEP

Institute for Tribal Environmental Professionals

Kdf

Cretaceous Fruitland Formation

Kpcl

Cretaceous Picture Cliffs Sandstone

LFG

Landfill Gas

Liquid Petroleum

LTO

Landing and Take-off Cycles

MMscf

Million Standard Cubic Feet

MSW

Municipal Solid Waste

NEI

National Emissions Inventory

NMHC

Non-methane Hydrocarbons

NMOC

Non-methane Organic Compounds

NOx

Oxides of Nitrogen

NPS

National Park Service

Ozone

Lead

PM10

Particulate Matter 10 microns and smaller

PM2.5

Particulate Matter 2.5 microns and smaller

PSD

Prevention of Significant Deterioration

PTE

Potential to Emit

Quality Assurance

RICE

Reciprocating internal combustion engine

scf

Standard Cubic Feet

SO2

Sulfur Dioxide

SUIT

Southern Ute Indian Tribe

TEG

Tri-ethylene Glycol

TEISS

Tribal Emissions Inventory Software Solutions

THC

Total Hydrocarbons

TMNSR

Tribal Minor New Source Review Program

TOC

Total Organic Compounds

tpy

Tons per Year

USFS

United States Forest Service

VOC

Volatile Organic Compounds

WIAC

Waste Industry Air Coalition

WRAP

Western Regional Air Partnership

4SLB

Four stroke lean burn

4SRB

Four stroke rich burn

2SLB

Two stroke lean burn

Executive Summary

The Southern Ute Indian Tribe (Tribe) Air Quality Program (AQP) has prepared an

emissions inventory of all quantifiable point and non-point sources on the Southern Ute

Indian Reservation (Reservation) for calendar year 2015 (CY2015). The emissions

inventory was prepared according to the Environmental Protection Agency Class II

emission inventory guidelines of using measured data when available or data and emissions

factors from reputable sources when measured data were not available.

Oil and natural gas production is the predominant industry on the Reservation and emissions

data for these sources were collected directly from source operators through annual emission

inventories, registrations, and a Clean Air Act (CAA) Section 114 information collection

request issued by the Tribe in June, 2016. Data for other sources were collected from

various reputable state, local, and federal data sources.

As of January 2016, there were a total of 2,767 oil and gas production sources operating on

the Reservation. These sources consisted of 37 sources operating under Title V operating

permits, 5 sources operating under Tribal Minor New Source Review (TMNSR) permits,

156 sources registered under the TMNSR program, and 2,569 non-point sources with

emissions below the TMNSR program thresholds, referred to in this emissions inventory as

“non-registered sources”.

Reservation emission totals for CY2015 were 19,231.8 tons per year (tpy) of oxides of

Nitrogen (NOx), 15,467.1 tpy of Volatile Organic Compounds (VOC), 86.4 tpy of Sulfur

Dioxide (SO2), 537.7 tpy of Particulate Matter 10 micrometers or less in diameter (PM10),

19,957.8 tpy of Carbon Monoxide (CO), 2,431.7 tpy of total Hazardous Air Pollutants

(HAP), and 9,357,473 tpy of Greenhouse Gas (GHG) emissions measured in Carbon

Dioxide Equivalents (CO2e).

Total criteria pollutant and HAP emissions on the Reservation for 2015 are presented below

in Figure 1.

Figure 1 – 2015 Total Criteria Pollutant and HAP Emissions on the Southern Ute

Indian Reservation in Tons per Year

II.

Overview

1. Purpose of Inventory

The purpose of this Emissions Inventory (EI) was to establish baseline emissions estimates

for the 2015 calendar year for all quantifiable air emission sources located within the

exterior boundaries of Reservation. The emissions data for the Reservation presented in this

EI has been organized by source category and pollutant. The EI will be used for future air

quality planning purposes, such as development of air quality regulations targeted at ozone

precursors for maintaining attainment with the National Ambient Air Quality Standards,

emissions modeling, and Title V permitting fee analysis.

The primary air pollutants included in this EI are NOx, CO, PM10, VOC, HAP and GHG.

2. Geographic Location of Southern Ute Indian Reservation

The Reservation is located in southwestern Colorado. The Reservation land area covers

1,066 square miles in three counties (La Plata, Archuleta, and Montezuma) and borders New

Mexico to the south. The total area covered by this inventory is approximately 682,590

acres, which encompasses all land within the external boundaries of the Reservation. The

Southern Ute Indian Tribe (Tribe) and/or its members own approximately 320,000 acres,

while the remaining land mass is comprised of non-Indian and government land in a

checkerboard fashion. The primary land use is agricultural and the predominant industry is

oil and natural gas production.

3. Climate

The Reservation remains generally semi-arid throughout the year. Located north of

northern New Mexico desert land and south of the Colorado alpines, the average

temperature range during the winter months is between twenty and forty degrees Fahrenheit.

Freezing temperatures are common throughout the winter and during the 2015 calendar year

the coldest month was December with a low of -1.0 degrees Fahrenheit and a monthly

average of 26.2 degrees Fahrenheit. During the summer months the temperature typically

remains in the high eighties to low nineties. The warmest month of 2015 was June with a

high of 96.0 degrees Fahrenheit, and a monthly average of 67.6 degrees Fahrenheit. Snow is

the dominant form of precipitation on the Reservation and total precipitation for calendar

year 2015 was 18.37 inches. The driest month was March with a 0.34 inches of precipitation

and the wettest month was October with 2.61 inches of precipitation.1

4. Geology

The Reservation is situated in the northern portion of the San Juan Basin, a geologic

structural basin underlying southwestern Colorado and northwestern New Mexico. The

basin is composed of Cambrian to Holocene aged sedimentary rocks and contains one the

largest coal-bed methane natural gas fields in the world within the Cretaceous aged

Fruitland Formation.2 The majority of the natural gas production on the Reservation is

coalbed methane from the Fruitland Formation, but conventional natural gas is also

produced from Cretaceous aged sandstone reservoirs of the Pictured Cliffs Formation, Mesa

Verde Group, and the Dakota Sandstone. Tight gas reservoirs of the Cretaceous aged

Mancos Shale have also been drilled, however, no significant exploration and production

has occurred within the Reservation as of 2015.

5. Sources

The sources that were included in this emissions inventory were organized according to

location and size. These point sources are as follows:

A. Point Sources

1) Title V permitted oil and natural gas sources

2) TMNSR minor oil and natural gas sources, including:

a. Permitted minor TMNSR sources,

Southern Ute Indian Tribe: Ambient Monitoring. (2015). 2015 AQS Ute 3 Humidity and Temperature Hourly

Data. Retrieved from: http://www.southernute-nsn.gov/environmental-programs/air-quality/ambient-monitoring/

Fasset, J. E., & Hinds, J. S. (1971). Geology and Fuel Resources of the Fruitland Formation and Kirtland Shale of

the San Juan Basin, New Mexico and Colorado. Geological Survey Professional Paper 676. United States

Government Printing Office. Retrieved from https://pubs.usgs.gov/pp/0676/report.pdf

b. Registered minor TMNSR sources,

3) Municipal solid waste landfills, and

4) Airports.

B. Non-point Sources

1) Non-registered minor oil and natural gas sources,

2) Fruitland Formation Outcrop natural gas seeps,

3) Gasoline stations,

4) Aviation gasoline dispensing,

5) Gravel pits,

6) Residential heating,

7) Fire events (wildland fires and prescribed burns), and

8) Agricultural burning.

C. Mobile Sources

1) On-road vehicles, and

2) Non-road equipment.

D. Biogenic Sources

III.

Data Quality Objectives

Data objectives for this inventory are as follows:

1. Accuracy



Data for this EI were collected according to EPA level II EI guidelines using measured

data when available or data from reputable sources such as EPA, the Colorado Oil and

Gas Conservation Commission (COGCC) and professional organizations when

measured data were not available.

Emission factors were developed using measured data or commonly accepted emissions

factors and assumptions from EPA and professional organizations.

All data sources, emission factors, assumptions, and emission calculation methodologies

were documented.

Utilize emission calculation models when available (GRI-GLYCalc 4.0, Tanks 4.09d,

etc.) and inputs provided in annual emission reports or 2016 CAA Section 114

Information Collection Request (ICR).

Compare results of 2015 SUIT EI with results from the CY2006 Western Regional Air

Partnership (WRAP) Oil and Gas EI for the North San Juan Basin and the CY2014

WRAP EI for the Greater San Juan Basin.

Quality Assurance review of emission totals, assumptions, emission factors, and

calculation methodologies was conducted by a third party contractor.

2. Uncertainty



Reported emissions may be inaccurate.

The number of unreported oil and gas sources is unknown and can only be estimated

based on sources reported to COGCC.

An accurate EI for small oil and gas sources has never been completed for the

Reservation.

Emissions differences between CY2015 SUIT EI with WRAP CY2006 and 2014 EIs

may occur due to different preparation methodologies and assumptions.

3. Completeness



Capture 100% of point source emissions reported in the annual emission fees for

CY2015.

Capture 95% of non-point oil and gas sources in the 2016 CAA 114 ICR.

Reported information will be used to extrapolate emissions to 100% to fill data gaps.

Capture 80% of area sources (gas stations, etc.).

4. Comparability



IV.

EI results will be compared with results from the CY2006 WRAP Oil and Gas EI for the

North San Juan Basin and the CY2014 WRAP EI for the Greater San Juan Basin.

Emission factors and assumptions will be compared with methodologies used in similar

emission calculation applications.

Point Sources

1. Title V Permitted Oil and Gas Sources

Description of Sources

Thirty-six oil and gas Title V sources operated on the Reservation during calendar year

2015. Sources include natural gas compressor stations, central delivery points, treating

plants, and processing plants.

Title V sources are defined as sources with the potential to emit (PTE) one-hundred tons per

year (tpy) of a single criteria pollutant, twenty-five tpy of hazardous air pollutants (HAP) in

aggregate, or ten tons per year of an individual HAP. The Tribe has full delegation of a

Title V operating permit program under 40 CFR Part 70 and during calendar year 2015,

thirty-five oil and gas sources operated under Tribally-issued Title V permits. One source, a

natural gas processing plant, continued to operate under a Title V permit issued by EPA

Region 8.

Data Collection

Title V sources are required to report emissions annually and pay a per-ton emission fee for

pollutants emitted. Emissions data for Title V sources were collected directly from the

calendar year 2015 fee calculation worksheets submitted by each source to the Tribe and

EPA Region 8. Actual emissions data were available for all thirty-six Title V oil and gas

sources. Actual CO emissions were only reported for twenty-eight sources and actual GHG

emissions (measured in carbon dioxide equivalents (CO2e)) were not reported for any

sources. The missing CO and CO2e emissions data for these sources were obtained from

PTE values reported in Title V permit applications representing operation in calendar years

2012 or 2013.3 This data collection methodology adheres to the EPA level II EI guidelines

for utilizing measured data when available.

Emissions

Total criteria pollutant and GHG emissions estimated from Title V sources for the 2015

calendar year are displayed below in Figure 2 and Figure 3.

Figure 2 – 2015 Title V Oil and Gas Source Criteria Pollutant and GHG Emissions

Estimations for the Southern Ute Indian Reservation in Tons per Year¹, ²

2015 Title V Criteria Pollutant and GHG Emissions Estimations in Tons per

Year

Pollutant

Emissions

NOx

CO¹

VOC

PM10

SO2

CO2e²

2,598.2

2,817.3

1,155.0

68.8

52.3

2,012,320

¹Actual CO emissions were obtained from the fee calculation worksheet, if the Title V source included the CO

actual emissions. There were 28 Title V sources that included the actual CO emissions for the 2015 calendar

year. CO emissions for 8 sources are PTE values obtained from Title V permit applications representing

operations in calendar years 2012 or 2013.

²CO2e emissions for all Title V sources are PTE values obtained from Title V permit applications representing

operation in calendar years 2012 or 2013

(2016). Southern Ute Indian Tribe or EPA Calendar Year 2015 Part Title V FEE Forms.

Figure 3 – 2015 Title V Oil and Gas Source Criteria Pollutant Emissions on the

Southern Ute Indian Reservation in Tons per Year

Oxides of Nitrogen emissions by equipment type at Title V sources for the 2015 calendar

year are displayed below in Figure 4.

Figure 4 – 2015 NOx Emissions at Title V Oil and Gas Sources on the Southern Ute

Indian Reservation by Equipment Type in Tons per Year

Volatile organic compound emissions by equipment type at Title V sources for the 2015

calendar year are displayed below in Figure 5.

Figure 5 – 2015 VOC Emissions at Title V Oil and Gas Sources on the Southern

Ute Indian Reservation by Equipment Type in Tons per Year

Total and speciated 2015 HAP emissions from Title V sources are displayed below in

Figure 6 and Figure 7.

Figure 6 – 2015 Title V Oil and Gas Source Hazardous Air Pollutant Emissions on

the Southern Ute Indian Reservation in Tons per Year

2015 Title V Hazardous Air Pollutant Emissions in Tons per Year

Pollutant

Formaldehyde

Benzene

Toluene

Xylene

Ethylbenzene

Acetaldehyde

Acrolein

n-Hexane

Other HAP¹

Total

Emissions

173.1

4.9

34.8

19.6

0.9

3.6

2.1

2.4

51.2

291.78

¹Other HAP is a composite of non-speciated HAP emissions from CY 2015 Title V Fee calculation worksheets.

Figure 7 – 2015 Title V Oil and Gas Source Hazardous Air Pollutant Emissions on

the Southern Ute Indian Reservation in Tons per Year

Hazardous Air Pollutant emissions by equipment type at Title V sources for the 2015

calendar year are displayed below in Figure 8.

Figure 8 – 2015 Hazardous Air Pollutant Emissions at Title V Oil and Gas Sources

on the Southern Ute Indian Reservation by Equipment Type in Tons per Year

Greenhouse Gas emissions by equipment type at Title V sources for the 2015 calendar year

are displayed below in Figure 9.

Figure 9 – 2015 Greenhouse Gas Emissions at Title V Oil and Gas Sources on the

Southern Ute Indian Reservation by Equipment Type in Tons per Year

2. Minor Point Sources

The Tribal Minor New Source Review (TMNSR) permitting program is found at 40 CFR

Part §49.151 through §49.164.4 The TMNSR permitting program includes new or modified

source permitting, permits by rule, and a registration program. For the purposes of this

inventory, two main categories of emission sources under this program were considered: a.)

Permitted TMNSR oil and gas sources, and b.) Registered TMNSR Oil and Gas Sources.

The emission thresholds for the TMNSR permitting program are located at 40 CFR Part

§49.153. Minor sources with emissions less than the levels displayed in Figure 10 below

are not required to obtain a permit or register under the program.

The emission thresholds from 40 CFR Part 49.153 are displayed below in Figure 10.

40 CFR Part 49 - Indian Country: Air Quality Planning and Management. (2016). U.S. Government Publishing

Office. Retrieved from http://www.ecfr.gov/cgi-bin/textidx?SID=bc4187dbf0b08beb092efe4251fe4493&mc=true&tpl=/ecfrbrowse/Title40/40cfr49_main_02.tpl

Figure 10 – 40 CFR Part 49 Minor New Source Review Program Emissions

Thresholds in Tons per Year

40 CFR 49.153 Minor NSR Thresholds

Regulated NSR Pollutant

Carbon Monoxide (CO)

Nitrogen Oxides (NOx)

Sulfur Dioxide (SO2)

Volatile Organic Compounds (VOC)

PM10

PM2.5

Lead

Fluorides

Sulfuric Acid Mist

Hydrogen Sulfide (H2S)

Total Reduced Sulfur (including H2S)

Reduced Sulfur Compounds (including H2S)

Municipal Waste Combustor Emissions

Municipal Solid Waste Landfill Emissions

(measured as non-methane organic

compounds)

Minor NSR Thresholds for

Attainment/Unclassifiable Areas in Tons per

Year

0.1

A. Permitted Tribal Minor New Source Review Oil and Gas Sources

Description of Sources

This category reflects larger emission sources that would be subject to either the

Prevention of Significant Deterioration (PSD), Title V operating permit program, or

both programs absent enforceable emission limitations to reduce the source’s PTE.

These types of permits are often referred to as “synthetic minor permits”.

During calendar year 2015, twelve sources on the Reservation operated under TMNSR

permits. Of the twelve sources in this category, eleven sources were natural gas

compressor stations and one source was a natural gas processing plant. Five sources had

permits to reduce emissions below Title V permitting thresholds and seven sources had

permits to reduce emissions below the PSD permitting thresholds.

Data Collection

Only the five sources with TMNSR permitted emissions below the Title V permitting

thresholds were included in this category in order to avoid double counting emissions.

Emissions from the remaining seven sources, which hold Title V operating permits

issued by the Tribe, were already accounted for under the Title V Oil and Gas Sources

category of this inventory.

TMNSR sources are required to submit annual emissions inventories to EPA Region 8

for the pollutants regulated under each permit and emissions data was collected directly

from the annual emissions inventories submitted for calendar year 2015.5 For pollutants

not reported in the annual emissions inventories, the Southern Ute Indian Tribe Air

Quality Program (AQP) requested and received PTE data from the source operators.

This data collection methodology adheres to the EPA level II EI guidelines for using

measured data when available.

Emissions

Total 2015 criteria pollutant, HAP, and GHG emissions from permitted TMNSR oil and

gas sources on the Southern Ute Indian Reservation are presented below in Figure 11.

Figure 11 – 2015 Criteria Pollutant and HAP Emissions for Permitted Tribal

Minor New Sources Review Oil and Gas Sources on the Southern Ute Indian

Reservation in Tons per Year¹

2015 Criteria Pollutant and HAP Emissions for Permitted TMNSR Oil and Gas

Sources in Tons per Year

Pollutant

Total

(tons per

NOx

VOC

HAP

CO2e

year)

Emissions

342.7

187.5

9.1

5.1

16.2

120,489

¹ Emissions from a composite of (2016). CY 2015 EPA TMNSR Fee Forms and PTE data from source

operators.

(2016). CY 2015 EPA TMNSR Fee Forms.

Total criteria pollutant and HAP emissions from permitted TMSNR oil and gas sources

on the Southern Ute Indian Reservation are presented below in Figure 12.

Figure 12 – 2015 Criteria Pollutant and HAP Emissions for Permitted Tribal

Minor New Sources Review Oil and Gas Sources on the Southern Ute Indian

Reservation in Tons per Year

Total 2015 NOx emissions from permitted TMNSR oil and gas sources on the

Reservation are displayed below in Figure 13.

Figure 13 – 2015 NOx Emissions for Permitted Tribal Minor New Sources Review

Oil and Gas Sources on the Southern Ute Indian Reservation in Tons per Year

Total 2015 VOC emissions from permitted TMNSR oil and gas sources on the

Reservation are displayed below in Figure 14.

Figure 14 – 2015 VOC Emissions for Permitted Tribal Minor New Sources Review

Oil and Gas Sources on the Southern Ute Indian Reservation in Tons per Year

Total 2015 HAP emissions from permitted TMNSR oil and gas sources on the

Reservation are displayed below in Figure 15.

Figure 15 – 2015 Total HAP Emissions for Permitted Tribal Minor New Sources

Review Oil and Gas Sources on the Southern Ute Indian Reservation in Tons per

Year

Total 2015 speciated HAP emissions from permitted TMNSR oil and gas sources on the

Reservation are displayed below in Figure 16 and Figure 17.

Figure 16 – 2015 Speciated HAP Emissions for Permitted Tribal Minor New

Sources Review Oil and Gas Sources on the Southern Ute Indian Reservation in

Tons per Year

2015 HAP Emissions for Permitted TMNSR Oil and Gas Sources in Tons per Year

Pollutant

(tons per

year)

Formaldehyde

Benzene

Toluene

Xylenes

Ethylbenzene

Acetaldehyde

Acrolein

nHexane

Totals:

22.3

0.6

2.7

5.4

0.0

0.3

0.2

0.1

Figure 17 – 2015 Speciated HAP Emissions for Permitted Tribal Minor New

Sources Review Oil and Gas Sources on the Southern Ute Indian Reservation in

Tons per Year

Total 2015 GHG emissions from permitted TMNSR oil and gas sources on the

Reservation are displayed below in Figure 18.

Figure 18 – 2015 GHG Emissions for Permitted Tribal Minor New Sources Review

Oil and Gas Sources on the Southern Ute Indian Reservation in Tons per Year

B. Registered Tribal Minor New Source Review Oil and Gas Sources

Description of Sources

The TMNSR program required operators of true minor sources as defined in §49.152, to

Existing oil and gas sources, constructed or modified after March 1, 2013, but before

October 3, 2016 were also required to register. All oil and gas sources constructed after

March 1, 2013 are required to apply for a site-specific TMSNR permit or comply with

the Oil and Gas Federal Implementation Plan for Indian Country at 40 CFR Part 49,

Subpart C.

As of January 2016, EPA Region 8 had received 156 oil and gas source registrations for

the Reservation.6 The registrations included source locations, emission unit descriptions,

and actual emissions calculations. All of the registered sources are natural gas

production sources, primarily well-sites. Certain non-oil and gas sources, such as hot

mix asphalt plants and stone quarrying, crushing and screening operations, also required

registration with the EPA under the TMNSR program, but to date, no such sources have

been registered. Presumably, non-oil and gas sources that did not register with the EPA

Southern Ute Indian Tribe. (2016). Information Collection Request.

may exist on the Reservation, and this issue will be addressed below in the data

collection section.

Data Collection

For the purposes of this emission inventory section, only emissions from registered

TMNSR sources were included. Sources with Title V operating permits or synthetic

minor permits were not required to register under 40 CFR Part 49; therefore, there is

little risk of double counting emissions from these sources. Emissions from Title V

sources and synthetic minor sources were assessed separately, as discussed in Chapter

IV Section 1 and 2A of this report.

Due to the potential for registration information to be stale or out of date, the AQP

issued a mandatory Clean Air Act Chapter 114 ICR in June 2016 to obtain updated and

reconciled registration data from each facility operator. The ICR also included data for

non-registered oil and gas sources. Specifically, the ICR requested reconciliation of the

operational status of each previously registered source, equipment located at each

source, and the actual emissions for calendar year 2015.

The ICR also requested information that was exempted from TMNSR registration

including emissions estimates for engines less than or equal to 50-hp and facility-wide

emissions of HAP and GHG. It was also anticipated that the ICR could result in

emissions reporting by sources that had never registered with the EPA. This data

collection methodology adheres to the EPA level II EI guidelines for utilizing measured

data when available.

Emissions

Total 2015 emissions of criteria pollutants, HAP, and GHG from registered TMNSR oil

and gas sources on the Reservation are displayed below in Figure 19 and Figure 20.

Figure 19 – 2015 Criteria Pollutant and HAP Emissions from Registered TMNSR

Oil and Gas Source on the Southern Ute Indian Reservation in Tons per Year¹

2015 Registered TMNSR Criteria Pollutant Emissions in Tons per Year

Total

PM10

SO2

NOx

VOC

HAP

CO2e

Emissions 4,835.3

3,859.1

964.2

51.7

23.9

312.5

631,331

Pollutant

¹Emissions from Southern Ute Indian Tribe. (2016). Information Collection Request

Figure 20 – 2015 Criteria Pollutant and HAP Emissions from Registered TMNSR

Oil and Gas Sources on the Southern Ute Indian Reservation in Tons per Year

Total 2015 NOx emissions from registered TMNSR oil and gas sources on the

Reservation by equipment type are displayed below in Figure 21.

Figure 21 – 2015 Total NOx Emissions for Registered Tribal Minor New Sources

Review Oil and Gas Sources on the Southern Ute Indian Reservation by

Equipment Type in Tons per Year

Total 2015 VOC emissions from registered TMNSR oil and gas sources on the

Reservation by equipment type are displayed below in Figure 22.

Figure 22 – 2015 Total VOC Emissions for Registered Tribal Minor New Sources

Review Oil and Gas Sources on the Southern Ute Indian Reservation by

Equipment Type in Tons per Year

Total 2015 HAP emissions from registered TMNSR oil and gas sources on the

Reservation by equipment type are displayed below in Figure 23.

Figure 23 – 2015 Total HAP Emissions for Registered Tribal Minor New Sources

Review Oil and Gas Sources on the Southern Ute Indian Reservation by

Equipment Type in Tons per Year

Total 2015 GHG emissions from registered TMNSR oil and gas sources on the

Reservation by equipment type are displayed below in Figure 24.

Figure 24 – 2015 Total GHG Emissions for Registered Tribal Minor New Sources

Review Oil and Gas Sources on the Southern Ute Indian Reservation by

Equipment Type in Tons per Year

3. Landfill Gas

The Southern Ute Indian Tribe has two Class II municipal solid waste (MSW) landfills

within the Reservation boundaries. The first one is the Bondad Landfill located in Bondad,

Colorado and the second one is the Archuleta County Landfill, located south of Pagosa

Springs, Colorado. Both of the MSW disposal sites accept non-hazardous residential,

commercial, and industrial waste. The Bondad landfill is owned and operated by Transit

Waste, LLC and has been in operation since 1997. The Archuleta County landfill is owned

and operated by Archuleta County and began operation in 1985. The Bondad Landfill

operates under a tribally issued Title V operating permit and the Archuleta County Landfill

reports annual landfill gas emissions to the Colorado Department of Public Health and

Environment (CDPHE).

Data Collection

Emission data for the Archuleta County Landfill were provided by the Archuleta County

Solid Waste Department and included a calendar year 2015 greenhouse gas report and an

Air Pollution Emission Notice and Application for Construction Permit and Design

Capacity Report. All reports were previously submitted by Archuleta County to the CDPHE.

Emissions data for the Bondad Landfill were directly obtained from the CY2015 Title V

emissions fee form submitted to the Tribe.

Emission Calculation Methodology

Emissions for both the Archuleta County and Bondad landfills were estimated using the

EPA’s MSW landfill emissions model, LandGEM version 3.02 (LandGEM).7 The

LandGEM model estimates total landfill gas, non-methane organic compounds (NMOC),

and hazardous air pollutants (HAP).

The LandGEM model is based on a first-order decomposition rate equation for quantifying

emissions from the decomposition of landfilled waste in MSW landfills.

 M i   kt ij

QCH 4    kL0 

e

 10 

i 1 j  0.1

Where:

QCH4 = annual methane generation in the year of calculation (m3/year)

i = 1 year time increment

n = (year of the calculation) – (initial year of waste acceptance)

j = 0.1 year time increment

k = methane generation rate (year-1)

Lo = potential methane generation capacity (m3/Mg)

Mi = mass of waste accepted in the ith year (Mg)

tij = age of the jth section of waste mass Mi accepted the ith year (decimal years, e.g., 3.2

years)

LandGEM Inputs and Assumptions

Complex microbial and biochemical reactions occur within the landfill’s interior after the

waste has been deposited. The two primary constituents of landfill gas (LFG) are methane

(CH4) and carbon dioxide (CO2). LFG also contains small amounts of non-methane organic

compounds, which includes VOC, HAP, and GHG. LandGEM estimates the LFG from

anaerobic decomposition of the waste with CH4 and CO2 content between 40 and 60 percent.

The LandGEM defaults used for methane is 50 percent by volume (the model default value).

The production of LFG is a continuous process until microbial reactions are limited by

substrate or moisture. Other factors include climate, moisture conditions and types of solid

waste accepted (degradable vs. inert).

Parameters for climatic conditions used in the LandGEM model were a k-value of 0.02 year1 (an arid area that receives less than 25 inches of rain annually) and a Lo-value of 170 cubic

U.S. EPA - Landfill Gas Emissions Model. (2016). Retrieved from https://www.epa.gov/catc/clean-airtechnology-center-products#software.

meter per megagram. The VOC concentrations are assumed to be 39 percent of NMOC

concentrations, consistent with the footnote C Table 2.4-2 of the EPA’s publication titled

AP-42, Fifth Edition Compilation of Air Emission Factors (EPA AP-42).8 For the Bondad

Landfill the concentrations of HAPs in the LFG were taken from the values reported in the

Waste Industry Air Coalition (WIAC) report titled Comparison of Recent Landfill Gas

Analyses with Historic AP-42 Values.9 For HAP compounds not listed in the WIAC report,

emission factors from EPA AP-42 Table 2.4-1 and Section 2.4-4 were used. HAP emissions

for the Archuleta County Landfill are from the LandGEM report using default emissions

factors from EPA AP-42. The total estimated emissions of LFG were estimated using the

flow rate and molecular weights.

Emissions

The estimated LandGEM emissions for Bondad Landfill were provided to the Tribe in a

Title V emissions fee form package submitted by Transit Waste for calendar year 2015.

Emissions estimates for Archuleta County Landfill were calculated by the Tribe using

LandGEM and the waste acceptance rates and waste-in-place data values for 2015 taken

from the 2015 GHG report previously submitted by Archuleta County to the CDPHE. The

AQP used the same assumptions and climatic parameters used in the report for Bondad

Landfill as these values have been previously reviewed and deemed acceptable when

preparing the Title V permit for the Bondad Landfill.

To avoid double counting emissions from the Bondad Landfill, emissions from Bondad

Landfill were only included in the Landfill gas emission totals and not included in the Title

V emission totals presented in Section I.V.1 of this report.

Total refuse in place in tons and total emissions of VOC and HAP from MSP landfills on

the Reservation for 2015 are displayed below in Figure 25 and Figure 26.

U.S. Environmental Protection Agency. (2016). AP-42: Compilation of Air Emission Factors. Retrieved from

https://www.epa.gov/air-emissions-factors-and-quantification/ap-42-compilation-air-emission-factor

Waste Industry Coalition. (2001, January). Comparison of Recent Landfill Gas Analysis with Historic AP-42

Values.

Figure 25 – 2015 Municipal Solid Waste Landfill Refuse in Place in Tons and

Emissions on the Southern Ute Indian Reservation in Tons per Year ¹

2015 MSW Landfill Refuse in Place in Tons and Emissions in Tons per Year

Bondad

Landfill

Archuleta

County

Landfill

Totals

Refuse in Place

(tons)

VOC (tons per year)

HAPs (tons per year)

799,873

3.2

0.8

268,687

1.3

1.2

1,068,560.0

4.5

2.0

¹An insignificant quantity of double counting of VOCs occurs because many reported HAPs are also considered VOCs.

Figure 26 – 2015 Municipal Solid Waste Landfill Refuse in Place in Tons and

Emissions on the Southern Ute Indian Reservation in Tons per Year

4. Airports

There are three airports located within the Reservation, the Durango-La Plata County

airport, the Animas Air Park and the Animas Air Park Helipark.

Data Collection

The AQP obtained data from EPA’s 2014 National Emissions Inventory database (NEI),

which include total landing and take-off cycles (LTOs) and piston and turbine engine

emission estimates for the heliport, taxi and general aviation at the Animas Air Park.10 The

LTOs were from the Federal Aviation Administration (FAA). The methodologies used by

EPA to calculate airport emissions are detailed in the Eastern Research Group’s document

titled Documentation for Aircraft Component of the National Emissions Inventory

Methodology.11

Emissions data for the Animas Air Park and Animas Air Park Heliport were submitted to

the NEI by EPA. Emissions data for the Durango-La Plata airport were reported to the NEI

by the CDPHE.

Assumptions

Calendar year 2014 airport emissions are assumed to be similar to emissions from the

airports during CY2015.

Emissions

Total 2015 criteria pollutant and HAP emissions from airports on the Reservation for 2015

are displayed in Figure 27 and Figure 28 below.

Figure 27 –2015 Criteria Pollutant and HAP Emission from Airports on the

Southern Ute Indian Reservation in Tons per Year¹

2015 Criteria Pollutant and HAP Emission from Airports in Tons per Year

Total

NOx

VOC

SO2

PM10

Lead

HAP

Animas Air Park

Heliport

0.0

0.3

0.0

Animas Air Park

0.4

0.8

0.1

1.7

0.0

30.9

0.3

Durango-La Plata

County

34.5

16.6

4.2

10.5

0.1

167.2

4.8

Total

34.9

17.5

4.3

12.2

0.1

198.4

5.1

¹Emissions estimations for airports are from the 2014 EPA National Emission Inventory Database and

assumed to be realistic estimations of airport emissions for 2015.

U.S. EPA National Emission Inventory Emissions Inventory System. (2014). Retrieved from

https://eis.epa.gov/eis-system-web/welcome.html

Eastern Research Group. (2001, January). Documentation for Aircraft Component of the National Emissions

Inventory Methodology. (ERG No. 0245.03402.011).

Figure 28 – 2015 Criteria Pollutant and HAP Emissions from Airports on the Southern

Ute Indian Reservation in Tons per Year

¹Emissions estimations for airports are from the 2014 EPA National Emission Inventory Database and

assumed to be realistic estimations of airport emissions for 2015.

Non-Point Sources

1. Non-registered Oil and Gas Sources

Description of Sources

For the purpose of this EI non-registered oil and gas sources are defined as: oil and gas

sources with emissions below the thresholds that require registration under the EPA Tribal

Minor New Source Review (TMNSR) Program at 40 CFR Part 49. The majority of these

sources are natural gas and oil well-sites, which are comprised of artificial lift engines,

separators, filter coalescers, compressor engines, reciprocating compressors, lube oil tanks,

tank heaters, dehydration units, and produced water, condensate, and oil tanks.

Data Collection

Source information for non-registered oil and gas sources was obtained through a mandatory

Clean Air Act Section 114 ICR issued by the AQP in June of 2016 to each known operator

with sources operating on the Reservation. To identify the operators within the Reservation

and estimate the total number of non-registered sources on the Reservation, the AQP

compiled site and ownership data from the COGCC and Drilling Edge databases.12,13

The ICR was the basis for collecting the information necessary to calculate emissions from

non-registered oil and gas sources and required each recipient to provide actual equipment

counts, production information, and equipment configuration estimations for single and colocated well-sites. Data was requested for each company’s operations on the Reservation in

its entirety and not specific to any single source location.

Completed ICRs were submitted by 82% of the companies that reported production on the

Reservation in CY2015 to the COGCC or Drilling Edge databases. Data obtained from the

ICRs accounted for the equipment and production associated with 98% of the 2,588 known

non-registered oil and gas sources on the Reservation. The AQP used ground surveys to

estimate equipment counts for the remaining unreported sources.

Calculation Methodology

The AQP calculated emissions for non-registered oil and gas sources on equipment basis

using widely accepted emission factors and emission calculation methodologies, the

equipment counts reported in the ICR, and CY2015 production data from the COGCC and

Drilling Edge databases. Emissions totals for the 2% of non-reported sources were

extrapolated to 100% based on the equipment configuration estimations derived from data

obtained in the returned ICR and equipment counts taken during ground surveys.

Descriptions of how emissions were calculated for each equipment type are included later in

this section.

Non-Registered Oil and Gas Sources Emissions Summary

Criteria pollutant, HAP and GHG emission estimations from non-registered oil and gas

sources on the Reservation in 2015 are displayed below in Figure 29 and Figure 30.

Figure 29 – 2015 Emissions from Non-registered Oil and Gas Sources on the

Southern Ute Indian Reservation in Tons per Year

2015 Emissions from Non-registered Oil and Gas Sources in Tons per Year

Pollutant

Emissions

Totals

NOx

VOC

SO2

PM10

Total

HAP

GHG

(CO2e)

9,959.0

902.7

0.0

191.6

8,354.8

255.9

1,505,611

COGCC. (2015). Production Data. La Plata. Retrieved from http://cogcc.state.co.us/data2.html#/downloads

Drilling Edge Database (2015). Retrieved from http://www.drillingedge.com/colorado

Figure 30 – 2015 Criteria Pollutant and HAP Emissions from Non-Registered Oil

and Gas Sources on the Southern Ute Indian Reservation in Tons per Year

Total 2015 NOx emissions from non-registered oil and gas sources on the Reservation by

equipment type are displayed below in Figure 31.

Figure 31 – 2015 NOx Emissions for Non-Registered Oil and Gas Sources on the

Southern Ute Indian Reservation by Equipment Type in Tons per Year

Total 2015 VOC emissions from non-registered oil and gas sources on the Reservation by

equipment type are displayed below in Figure 32.

Figure 32 – 2015 VOC Emissions for Non-Registered Oil and Gas Sources on the

Southern Ute Indian Reservation by Equipment Type in Tons per Year

Total 2015 HAP emissions from non-registered oil and gas sources on the Reservation by

equipment type are displayed below in Figure 33.

Figure 33 – 2015 HAP Emissions for Non-Registered Oil and Gas Sources on the

Southern Ute Indian Reservation by Equipment Type in Tons per Year

Total 2015 GHG emissions from non-registered oil and gas sources on the Reservation by

equipment type are displayed below in Figure 34.

Figure 34 – 2015 GHG Emissions for Non-Registered Oil and Gas Sources on the

Southern Ute Indian Reservation by Equipment Type in Tons per Year

A. Natural Gas-Fired Reciprocating Internal Combustion Engines

Description of Units

Natural gas-fired spark-ignited reciprocating internal combustion engines (RICE) are

used by the oil and gas industry to compress natural gas, pump liquids, generate

electricity, and to provide artificial lift. The most prevalent pollutants emitted from

natural gas-fired RICE are NOx, CO, VOC, and HAP.

Data Collection

The ICR required recipients to list the total number of natural gas-fired spark-ignition

and compression ignition RICE operated by their company on the Reservation. Engines

were reported according to horsepower range, and engine configuration. Engine

configurations included two-stroke lean-burn (2SLB), four-stroke lean-burn (4SLB), and

four-stroke rich-burn (4SRB). The ICR included assumed values for engine operating

hours and average brake specific fuel consumption (BSFC), and provided recipients the

option to provide values more representative of their operations. A summary of reported

engines is listed below in Figure 35.

Figure 35 – Engines Reported for Non-Registered Oil and Gas Source in the 2016

by Engine Configuration and Horsepower)

Emission Calculation Methodology

Criteria Pollutant and HAP Emissions:

Criteria pollutant and HAP emissions were calculated for each engine configuration and

horsepower rating category reported in the ICR. Emission calculations were based on

the maximum horsepower of each reported horsepower range, the appropriate emission

factors for stationary internal combustion sources from Chapter 3 of EPA AP-42, an

assumed BSFC of 7,500 Btu/hp-hr, an assumed 100% engine operating load, and

assumed operating schedule of 8,760 hours per year. The assumed BSFC value was

derived by averaging the BSCF from all natural gas-fired engines in the Caterpillar Gas

Engine Rating Pro software.14 All emissions were calculated for uncontrolled operation.

The natural gas on the Reservation contains negligible amounts of sulfur, therefore SO2

emissions from engines are minimal.

Caterpillar, Inc. (2015). Gas Engine Rating Pro Emissions Estimation Software. Retrieved from

http://www.cat.com/en_US/articles/solutions/oil-gas/gas_engine_rating_pro.html

GHG Emissions:

Greenhouse gas emissions were calculated using the default values from Tables C-1 and

C-2 of 40 CFR Part 98, Subpart C and the same methodology as used for criteria

pollutants and HAP.15

Example Calculation

Conversion of EPA AP-42 emission factor (in lb/MMBtu) to grams per horsepower hour

using AQP’s assumed brake specific fuel consumption (Btu/hp-hr):

g/hp-hr = (lb/MMBtu) x (7500 Btu/hp-hr) x (g/lb)/10^6

Where:

EF = AP-42 emission factor (lb/MMbtu)

HR = heat rating (Btu/hp-hr)

Example NOx AP-42 lb/MMBtu to g/hp-hr emission factor conversion for a four-stroke

rich-burn RICE:

g/hp-hr = (2.21 lb/MMBtu) x (7500 Btu/hp-hr) x (456.3/ 1 lb)/10^6 = 0.752 g/hp-hr

Engine emission calculation:

tpy = (EF) x (hp) x (OH)/453.6 g/lb /2000 pounds/ton

Where:

tpy = tons per year

EF = emission factor (g/hp-hr)

hp = horsepower

OH = annual operating hours

Example NOx emissions calculation for a 200 hp four-stroke rich-burn engine operating

8,760 hours per year:

tpy = (0.752 g/hp-hr) x (200 hp) x (8760 hr)/453.6 g/lb)/2000 lb/ton = 1.45 tpy NOx

40 CFR Part 98 - Mandatory Greenhouse Gas Reporting. (2016). U.S. Government Publishing Office. Retrieved

from http://www.ecfr.gov/cgi-bin/textidx?SID=32c4baa0d0aff54fa651d1cdb1cd7934&mc=true&tpl=/ecfrbrowse/Title40/40cfr98_main_02.tpl

Emissions

Total criteria pollutant, HAP, and GHG emissions from natural gas-fired RICE at nonregistered oil and gas sources are displayed in Figure 36 and Figure 37.

Figure 36 – 2015 Natural Gas-Fired Reciprocating Internal Combustion Engine

Counts and Criteria Pollutant, HAP, and GHG Emissions on the Southern Ute

Indian Reservation in Tons per Year ¹

2015 Natural Gas-Fired RICE Counts and Emissions in Tons per Year on the

Southern Ute Indian Reservation¹

Engine

Configuration

and Horsepower

(hp)

2SLB 0-50 hp

2SLB 101-200 hp

2SLB 201-300 hp

2SLB 301-400 hp

2SLB 501-600 hp

4SLB 0-50 hp

4SLB 101-200 hp

4SLB 401-500 hp

4SRB 0-50 hp

4SRB 51-100 hp

4SRB 101-200 hp

4SRB 201-300 hp

4SRB 301-400 hp

4SRB 401-500 hp

Compression

Ignition

Total

Number

Engines

Reported

in 2016

ICR

600

217

NOx

SO2

PM10

VOC

Total

HAP

GHG

(CO2e)

206.5

760.0

281.2

2,443.4

999.7

152.9

107.2

134.0

2,160.7

1564.5

396.1

152.5

29.0

36.3

0.0

25.1

92.5

34.2

297.5

121.7

11.9

8.3

10.4

3,637.0

2,633.5

666.7

256.6

48.9

61.1

0.0

5.0

18.4

6.8

59.2

24.2

0.0

18.6

13.4

3.4

1.3

0.3

0.0

7.8

28.8

10.6

92.5

37.8

4.4

3.1

3.9

28.9

20.9

5.3

2.1

0.4

0.5

0.0

5.2

19.0

7.0

61.0

25.0

2.7

1.9

2.4

31.6

22.9

5.8

2.2

0.4

0.5

0.0

7,626.4

28,073.0

10,386.0

90,258.2

36,928.0

4,388.6

3,077.3

3,846.7

114,484.5

82,895.9

20,987.4

8,078.0

1,538.7

1,923.3

0.0

1,059

9,424

7,905.4

0.0

150.9

247.0

187.6

414,492

¹Engine emissions are only displayed for horsepower and engine configurations reported in the 2016 ICR.

Figure 37 - 2015 Natural Gas-Fired Reciprocating Internal Combustion Engine

Counts and Criteria Pollutant, HAP, and GHG Emissions on the Southern Ute

Indian Reservation in Tons per Year

Emissions of NOx, VOC, and CO from natural gas-fired RICE at non-registered oil and gas

sources on the Reservation in 2015 are displayed below in Figure 38, Figure 39, and Figure

40.

Figure 38 – Oxides of Nitrogen Emissions from Natural Gas-Fired Reciprocating

Internal Combustion Engines at Non-Registered Oil and Gas Sources on the

Southern Ute Indian Reservation in Tons per Year

Figure 39 - 2015 Volatile Organic Compound Emissions from Natural Gas-Fired

Reciprocating Engines at Non-Registered Oil and Gas Sources on the Southern Ute

Indian Reservation in Tons per Year

Figure 40 - 2015 Carbon Monoxide Emissions from Natural Gas-Fired

Reciprocating Engines at Non-Registered Oil and Gas Sources in Tons per Year

B. Stationary Natural Gas Turbines:

Description of Units

Natural gas-fired stationary turbines are a type of rotary internal combustion engine used

by the natural gas industry for natural gas transmission and for electric generation.

Turbines operate by introducing compressed air and fuel into a combustion chamber to

generate hot gases, which are expanded into the power turbine to rotate the power shaft

and create work. Two types of combustion processes are used in turbines, the first being

lean-premix staged combustion in which a lean air and fuel mixture is introduced into

the combustion chamber, and the second type being diffusion flame combustion where

the air and fuel mixing occurs within the combustion chamber. The power shaft is used

to run a centrifugal compressor for gas transmission, or to rotate an alternator when used

for electric generation.

Data Collection

The ICR required recipients to list the total number of natural gas-fired turbines operated

by their company on the Reservation. Turbines were reported according to horsepower

or kilowatt range, hours of operation, and turbine configuration. Turbine configurations

included uncontrolled, water-steam injection, and lean-premix. The AQP assumed

turbines to operate for 8,760 hours per year. Average brake specific fuel consumption

(BSFC) was assumed to be 11,000 Btu/hp-hr, as established in the document titled

Stationary Combustion Turbines in the United States.16 If an operator specific BSFC

was reported in the ICR, this value was used in place of the assumed BSFC value.

Only one turbine was reported at a non-registered source in the ICR. The turbine was a

0-50 hp, lean pre-mix unit, operated 8,760 hours per year, with a BSFC of 10,825

Btu/hp-hr.

Emission Calculation Methodology

Criteria Pollutant and HAP Emissions:

Criteria pollutant and HAP emissions were calculated based on the maximum reported

horsepower, emission factors for stationary gas turbines from Chapter 3.1 of EPA AP42, 100% engine operating load, an operating schedule of 8,760 hours per year and a

reported BSFC of 10,825 Btu/hp-hr. The calculation methodology for natural gas

turbines is the same methodology used for reciprocating internal combustion engines,

and displayed in an example calculation earlier in this section. The natural gas on the

Reservation contains negligible amounts of sulfur, therefore SO2 emissions from

turbines are minimal.

McGowin (1973) Stationary Combustion Turbines in the United States.

GHG Emissions:

Greenhouse gas emissions were calculated using the default values from Tables C-1 and

C-2 of 40 CFR Part 98, Subpart C and the same methodology as used for criteria

pollutants and HAP.

Emissions

Criteria pollutant, HAP, and GHG emissions from natural gas turbines on the Southern

Ute Reservation for 2015 are displayed in Figure 41.

Figure 41 - 2015 Turbine Count and Total Emissions of Criteria Pollutant, HAP,

and GHG at Non-Registered Oil and Gas Sources on the Southern Ute Indian

Reservation in Tons per Year

2015 Turbine Count and Total Emissions in Tons per Year

Turbine

Configuration

and

Horsepower

Lean-Premix

0-50 hp

Number

Turbines

NOx

SO2

PM10

VOC

Total

HAP

GHG

(CO2e)

0.2

0.0

326.0

C. Tri-Ethylene Glycol Dehydration Units

Description of Units

Tri-ethylene glycol (TEG) dehydration units are commonly used in the natural gas

industry to remove entrained water from the natural gas stream to meet pipeline contract

water specifications. The dehydration process begins with routing the natural gas stream

through TEG in an absorber (or contactor tower) where the entrained water is absorbed

by the TEG. During this step, hydrocarbons present in the natural gas stream are also

absorbed in the glycol. Following the absorption step, the water saturated (rich) glycol is

then distilled to drive off absorbed water before being re-circulated to the absorber. The

distillation step results in emissions of VOC and HAP from the reboiler still-vent. The

common still-vent HAP emissions are benzene, toluene, ethyl-benzene, and xylene.

Data Collection

The AQP collected dehydration unit counts from the ICR, which required operators to

enter the total number of dehydration units operated by their company on the

Reservation during calendar year 2015. The ICR included assumed dehydration unit

operating parameters and a theoretical extended natural gas analysis, as described later

in this section, which could be accepted or overridden with values more representative

of the operators’ operations. The theoretical extended gas analysis is displayed below in

Figure 42.

Fifty-one dehydration units were reported in the ICR submittals and all submittals

accepted the AQP’s assumed operation and natural gas composition values.

Emissions Calculation Methodology

Emissions for glycol dehydration units were calculated using the GRI-GLYCalc 4.0

model (GLYCalc), the AQP’s theoretical values for dehydration unit operating

parameters and natural gas composition, and the methodology outlined in the GLYCalc

user’s manual.17 GLYCalc is the EPA’s preferred method of quantifying emissions from

glycol dehydration units for the development of tribal/state/local emissions inventories.18

Product of combustion emissions from dehydration unit reboilers were included in the

emission totals for heaters and boilers presented in Section V.1. of this report to avoid

double counting.

Figure 42 – Theoretical Extended Natural Gas Analysis – Average of 34 Natural

Gas Analyses from the Southern Ute Indian Reservation

Theoretical Extended Natural Gas Analysis

Component

Methane

Ethane

Propane

Isobutane

n-Butane

Isopentane

n-Pentane

n-Hexane

Carbon Dioxide

Nitrogen

Hydrogen Sulfide

Helium

2,2 Dimethylbutane

2,3 Dimethylbutane

Cyclopentane

2-Methylpentane

3-Methylpentane

2,2 Dimethylpentane

Methylcyclopentane

2,4-Dimethylpentane

2,2,3-Trimethylbutane

Benzene

Average

92.2564%

1.1672%

0.3324%

0.0548%

0.0811%

0.0200%

0.0132%

0.0089%

5.9084%

0.1370%

0.0000%

0.0002%

0.0007%

0.0000%

0.0018%

0.0010%

0.0000%

0.0007%

Gas Research Institute. (2000). GLYCalc Version 4.0. Retrieved from

http://sales.gastechnology.org/000102.html

U.S. EPA. (1995). Glycol Dehydrator Emissions Test Report and Emissions Estimation Methodology. Retrieved

from https:www3.epa.gov/ttn/chief/old/efdocs/glycoldehydratortestreport.pdf

3,3-Dimethylpentane

Cyclohexane

2-Methylhexane

2,3-Dimethylpentane

1,1-Dimethylcyclopentane

3-Methylhexane

1,t-3-Dimethylcyclopentane

1,c-3-Dimethylcyclopentane

3-Ethylpentane

1,t-2-Dimethylcyclopentane

2,2,4 Trimethylpentane

n-Heptane

Methylcyclohexane

Toluene

n-Octane

Ethylbenzene

2,3-Dimethylheptane

m-Xylene

p-Xylene

o-Xylene

n-Nonane

n-Decane

n-Undecane

n-Dodecane

n-Tridecane

Total:

0.0000%

0.0013%

0.0000%

0.0002%

0.0032%

0.0017%

0.0012%

0.0018%

0.0001%

0.0000%

0.0003%

0.0002%

0.0001%

0.0006%

0.0005%

0.0001%

0.0000%

100.00%

Total VOC:

0.53%

GRI-GLYCalc Model Input Parameters

The AQP developed assumed dehydration unit operational values for natural gas

temperature, pressure, and flowrate by averaging operational information from

dehydration units at non-registered oil and gas sources provided by two of the largest

operators on the Reservation. An assumed extended natural gas analysis was prepared

by averaging 34 individual extended gas analysis from natural gas production sector

compressor stations that were reported to the AQP in Title V operating permit

applications between 2012 and 2014.

The AQP’s assumed values were input into the GLYCalc emissions model using a

pipeline water content specification of seven pounds of water per MMscf of natural gas,

1.5% H2O lean glycol, and assuming uncontrolled operation with no flash tank.

The assumed GLYCalc input parameter values are provided below in Figure 43.

Figure 43 – 2015 GRI-GLYCalc Model Input Parameters for TEG Dehydration

Units at Non-Registered Oil and Gas Sources on the Southern Ute Indian

Reservation

2015 GRI-GLYCalc Model Input Parameters

Wet Gas

Temperature

(°F)

Wet Gas

Pressure

(psig)

Dry Gas

Flowrate/

Throughput

(MMscf/day)

68.5

353.5

0.9

Lean

Glycol

Water

Content

(weight %

H2O)

1.5

Glycol

Pump Type

Electric/

Pneumatic

Pipeline

Water

Content

Specification

(lb

H2O/MMscf)

7.0

GRI-GLYCalc Model Emissions Output:

Fifty-one dehydration units were reported in the ICR submittals and all dehydration unit

emissions were calculated using the AQP’s default GRI-GLYCalc emissions report. The

GRI-GLYCalc report was applied once to each of the 51 dehydration units reported in

the ICR, and then summed to derive a Reservation-wide emissions estimate for glycol

dehydration units located at non-registered oil and gas sources.

No operator specific GLYCalc reports or dehydration unit emission estimations were

provided in the ICR submittals.

Modeled GRI-GLYCalc emissions for a single TEG dehydration unit and using the

AQP’s assumed model inputs are provided in Figure 44.

Figure 44 – 2015 GRI-GLYCalc Model Emissions Output for TEG Glycol

Dehydration Units on the Southern Ute Indian Reservation in Tons per Year

2015 GRI-GLYCalc Model Emissions Output in Tons per Year

Pollutant

Methane

Ethane

Propane

Isobutane

n-Butane

Isopentane

n-Pentane

Cyclopentane

n-Hexane

Cyclohexane

Other Hexanes

Heptanes

Uncontrolled Emissions

0.2341

0.0226

0.0211

0.0076

0.0156

0.0057

0.0050

0.0000

0.0080

0.0048

0.0000

Methylcyclohexane

2,2,4-Trimethylpentane

Benzene

Toluene

Ethylbenzene

Xylenes

C8+ Heavies

Total HC Emissions

Total VOC Emissions

Total HAP Emissions

Total BTEX Emissions

0.0097

0.0002

0.0237

0.0796

0.0122

0.0998

0.1469

0.6966

0.4399

0.3849

0.2153

Example Calculation

Example calculation for VOC emissions from ICR Reported dehydration units:

VOC Emissions (tpy) = AQP Generated GRI-GLYCalc Emissions Output x Number of

2016 ICR Reported Dehydration Units

Example:

22.4 tpy annual VOC emissions = 0.4399 tpy VOC x 51 reported dehydration units

Emissions

Volatile organic compound and HAP emissions from 51 TEG Glycol Dehydration Units

at non-registered oil and gas sources on the Reservation are provided in Figure 45.

Figure 45 – 2015 HAP and VOC Emissions from 51 TEG Dehydration Units at

Non-Registered Oil and Gas Sources on the Southern Ute Indian Reservation

2015 HAP and VOC Emissions from 51 TEG Dehydration in Tons per Year

Unit Count and

Number of

VOC

HAP

CO2e

Pollutants

Dehydration

Units

22.4

11.4

70,493.4

Totals

D. Liquid Storage Tanks

Description of Equipment and Emissions Categories

The oil and gas industry utilizes liquid storage tanks for the storage of produced water,

condensate, oil, coolants, and lubricants. The primary emissions from liquid storage

tanks are methane, VOC and HAPs. Emission categories include breathing and working

losses, flash emissions, and tank loadout.

Breathing and Working Losses:

Breathing losses occur when vapor expansion generated during temperature fluctuations

increases the vapor pressure within a tank and cause fugitive emissions to escape from

the roof vent. Light colored tanks and tank heaters can help maintain more consistent

tank temperatures and reduce breathing losses by reducing vapor pressure variations.

Full tanks also produce lower breathing losses due to less space for vapors to expand

and escape from roof vents. Working losses occur when liquids are pumped into and out

of storage tanks. The displacement of vapors within the tank and the turbulence caused

by the movement of the liquid create airborne vapors. Submerged fill tanks can be

effective for reducing turbulence and the creation of airborne vapors.

Flash Emissions:

Flash emissions are emissions that occur when liquid dumped from the separator into the

liquid storage tank goes from higher pressure to lower pressure, resulting in the

entrained gas being released as a vapor from the liquid. The gas to liquid ratio, pressure

and temperature of the liquids in the separator and the temperature and pressure of the

liquid storage tank influence the amount of flashing losses.

Tank Loadout Emissions:

Tank loadout emissions are vapor loss from transport tanks that occur during the transfer

of liquids from a storage tank to a transport tank. Loadout emissions occur due to the

generation of vapors in transport tanks during liquid loading, the transfer of vapors from

the liquid storage tank to the transport tank, and the displacement of vapors trapped in

transport tanks from previous loads during loading.

Data Collection

Tank Counts and Data for Calculating Breathing and Working Losses:

The ICR required each operator to provide the total number of produced water,

condensate, and oil tanks located at their non-registered sources on the Reservation.

Reported tank counts were based on tank contents and capacity in barrels (bbl).

A summary of tanks reported in the ICR, by tank capacity and contents, is displayed

below in Figure 46.

Figure 46 – 2015 Liquid Storage Tanks at Non-Registered Oil and Gas Sources on

the Southern Ute Indian Reservation by Tank Contents and Capacity in Barrels

The ICR also provided operators with the opportunity to override assumed data values

for annual liquid throughput, Reid Vapor Pressure, and general tank characteristics with

values more representative of their operations. Tank characteristics include roof type,

color, condition, and presence of a tank heater. Development of liquid throughput values

is discussed later in this section. Emissions from lubricant oil and glycol storage tanks

were assumed to be negligible and no data was requested for these sources.

Methodology for Deriving Average Liquid Throughput Values:

The AQP developed two types of annual liquid throughput values, based on the

availability of data in the COGCC database for sources in La Plata County, Colorado for

CY2015. If data were available from COGCC, the AQP developed specific operator

throughput values and if the data was not available, the AQP developed assumed annual

average liquid throughput values. The operator specific annual average liquid

throughput values were derived by dividing their total reported produced water and

condensate/oil production numbers by the total number of sources that reported

production for CY2015.

Assumed average annual liquid throughput values were developed for operators that

reported active sources to the COGCC in 2015, but did not report production. The

assumed annual throughput value for produced water was derived by dividing the total

CY2015 produced water production values reported to the COGCC database by the total

number of reported sources. A combined condensate and oil assumed annual average

tank throughput value was derived by dividing the total CY2015 combined condensate

and oil production value reported to the COGCC database by the number of non52

registered sources that reported condensate or oil production. Not all companies reported

condensate or oil production to COGCC and two companies reported much larger

condensate and oil production numbers than other companies producing condensate and

oil. Companies that did not produce any condensate or oil and the few companies with

large production numbers were dropped from the calculations to avoid skewed

production numbers. Assumed annual average liquid throughput values for the produced

water, oil and condensate at non-registered oil and gas sources on the Reservation are

displayed below in Figure 47.

Figure 47 – 2015 Assumed Annual Average Liquid Throughput Values for

Produced Water, Oil and Condensate Tanks at Non-Registered Sources on the

Southern Ute Indian Reservation¹

2015 Assumed Annual Average Liquid Storage Tank Throughput Values

Number of

Sources

Operating in

2015

3,477

2015

Oil/Condensate

Produced (bbl)

2015 Water

Produced (bbl)

13,662

18,956,811

Average

Oil/Condensate

per source per

year (bbl)

29.97

Average

Water per

source per

year (bbl)

10,935

¹Throughput numbers were derived from averaging production numbers from COGCC, (2015).

Production Data. Retrieved from http://cogcc.state.co.us/data2.html#/downloads

Emission Calculation Methodology

Liquid storage tank emissions are calculated based on three separate emission event

categories that occur during the course of normal tank operation at atmospheric

pressures, as described earlier in this section. The emissions categories include: standing

and working losses, flash emissions, and loadout emissions. Discussions are provided

below of the methodologies used to calculate emissions for each tank emissions

category.

Standing and Working Losses

Data Collection and Assumptions:

Emission totals for the Reservation were developed for each individual operator by

running the EPA TANKS 4.09d Emissions Estimation Software (TANKS) model once

for each tank size and production type category reported in the ICR and then multiplying

each modeled emissions total by the number of corresponding tanks reported.19 Reported

liquid throughput values were used when provided and assumed throughput values were

used when data was not provided.

U.S. EPA. (2006). TANKS 4.09d Emissions Estimation Software. Retrieved from

https://www3.epa.gov/ttnchie1/software/tanks

Emission Calculations:

Standing, and working losses were calculated using the TANKS model and reported or

assumed input data values for liquid throughput, Reid vapor pressure, and tank

characteristics. A produced water tank was assumed to consist of a mixture of 99%

water and 1% condensate and the TANKS model default values were used for

condensate and oil. The model was ran for tanks operating at atmospheric pressure and

the TANKS model meteorological conditions for Albuquerque, New Mexico. Emission

estimates using this geographic location may be biased slightly higher, as temperatures

in Albuquerque are warmer in summer and less cold in winter than within the

Reservation. All tanks were assumed to have a cone shaped roof, to be gray in color, and

equipped with a tank heater.

Liquid Storage Tanks Flash Emissions

Data Collection and Assumptions:

The ICR requested flash gas liberation data from produced water, condensate, and oil, to

aid in calculating flash emissions. No ICR submittals were returned with flash liberation

data, as this type of sampling is not common practice on the Reservation.

In September 2016, the AQP contracted a third party vendor to perform flash liberation

sampling at well-site locations operated by two different companies on the Reservation.

Sampling was performed on the separator at each well-site in order to obtain a

pressurized sample. In total, seven produced water samples were obtained from coal-bed

methane wells of the Fruitland Coal Formation on the east and west sides of the

Reservation. Two produced water samples and one condensate sample were obtained

from conventional natural gas wells of the Picture Cliffs Sandstone Formation in the

south central portion of the Reservation.20 Due to the very low oil production numbers

reported to the COGCC database for La Plata County Colorado in CY2015 and the

absence of viable sampling locations, the AQP elected to not obtain oil flash gas

samples, but to use the condensate flash sampling results to estimate oil flash emissions

Two additional condensate flash samples were provided by an operator that performed

sampling in August 2016 from liquid knockout locations on a well-site gathering

pipeline containing natural gas from conventional wells in the southern portion of the

Reservation.

All sampling reports included an extended gas analysis, gas to water ratio, gas specific

gravity, separator temperature and pressure, and ambient temperature and pressure.

Results from the six valid produced water samples were averaged to obtain assumed gas

composition and gas to water ratio values to be used in the Oil to Gas Ratio calculation

Air Pollution Testing, Inc. (2016). Southern Ute Indian Tribe Flash Liberation Analyses.

for estimating storage tank flash emissions. The same methodology was applied for

deriving average composition values from the three valid condensate samples.

Averaged extended gas analysis values for produced water and condensate are displayed

below in Figure 48 and Figure 49, respectively. Averaged gas to water and gas to

condensate values are displayed below in Figure 50.

Figure 48 –Produced Water Flash Gas Analysis from Non-Registered Oil and Gas

Sources on the Southern Ute Indian Reservation in Mol Percent – September 2016¹

Produced Water Flash Gas Analysis from the Southern Ute Indian

Reservation in Mol %

Flash Gas

Component

Sample

Average

Mol %

Hydrogen Sulfide

Nitrogen

Carbon Dioxide

Methane

0.0000

0.0373

72.3236

26.6076

0.0000

68.4996

31.0289

0.0000

1.0883

36.5680

62.2021

0.0000

1.0464

29.7757

67.0612

0.0000

2.6862

5.8668

91.4075

0.0000

0.5921

16.3515

76.3697

0.0000

0.9084

38.2309

59.1128

Ethane

0.3200

0.0271

0.1155

0.0138

0.0119

4.0640

0.7587

Propane

0.0359

0.0231

0.0124

0.037

0.0079

1.0078

0.1874

Isobutane

N-Butane

2,2

Dimethylpropane

Isopentane

N-Pentane

2,2 Dimethylbutane

Cyclopentane

2,3 Dimethylbutane

2 Methylpentane

3 Methylpentane

N-Hexane

Methylcyclopentane

0.0036

0.0100

0.0035

0.0160

0.0012

0.0015

0.0049

0.0163

0.0007

0.0029

0.1582

0.1689

0.0287

0.0359

0.0000

0.0028

0.0039

0.0000

0.4360

0.0000

0.0037

0.0078

0.0000

0.1881

0.0000

0.0003

0.0005

0.0000

0.0005

0.0000

0.0071

0.0117

0.0000

1.8678

0.0000

0.0005

0.0012

0.0000

0.0035

0.0000

0.1027

0.0612

0.0000

0.0108

0.0000

0.2114

0.0000

0.0195

0.0144

0.0000

0.0018

0.0000

0.4512

0.0000

0.0085

0.0084

0.0000

0.0227

0.0418

0.0000

0.0021

0.0000

0.1056

0.0481

0.0000

0.0228

0.0167

0.0000

0.0037

0.0108

0.1872

0.0000

0.0006

0.0000

0.0091

0.0000

0.0081

0.0514

0.0196

0.0000

0.0003

0.0000

0.0026

0.0029

0.0016

0.0011

0.0000

0.0088

0.0000

0.2092

0.0865

0.1397

0.2745

0.0000

0.0015

0.0000

0.0354

0.0169

0.0339

0.0819

0.0000

Benzene

Cyclohexane

2-Methylhexane

3-Methylhexane

2,2,4

Trimethylpentane

Other C7's

N-Heptane

Methylcyclohexane

Toluene

Other C'8s

N-Octane

Ethylbenzene

M&P Xylenes

O-Xylene

Other C9's

N-Nonane

Other C10's

N-Decane

0.0000

0.0008

0.0000

0.0141

0.0000

0.0049

0.0242

0.0000

0.0008

0.0065

0.0000

Undecanes(11)

0.0000

Totals:

100%

Total VOC:

0.7116%

0.2422%

0.0261%

2.1029%

0.0273%

2.6225%

0.9554%

Total HAP:

0.4561% 0.1881% 0.0005% 1.9560% 0.0054% 0.4946% 0.5168%

¹Air Pollution Testing, Inc. (2016, September). Southern Ute Indian Reservation Flash Liberation Analyses.

Figure 49 –Condensate Flash Gas Analysis from Non-Registered Oil and Gas

Sources on the Southern Ute Indian Reservation in Mol Percent – September 2016¹

Condensate Flash Gas Analysis from the Southern Ute Indian Reservation

Flash Gas Component

Sample 1

Mol%

Sample 2

Mol%

Sample 3

Mol%

Average Mol %

Hydrogen Sulfide

Nitrogen

Carbon Dioxide

Methane

Ethane

Propane

Isobutane

N-Butane

2,2 Dimethylpropane

Isopentane

N-Pentane

2,2 Dimethylbutane

Cyclopentane

2,3 Dimethylbutane

2 Methylpentane

3 Methylpentane

N-Hexane

Methylcyclopentane

Benzene

Cyclohexane

2-Methylhexane

3-Methylhexane

2,2,4 Trimethylpentane

Other C7's

N-Heptane

Methylcyclohexane

0.000

6.633

3.053

62.466

14.918

6.279

1.371

1.738

0.000

0.794

0.551

0.000

0.869

0.000

0.105

0.000

0.003

0.000

0.557

0.000

5.170

2.564

62.678

16.162

7.028

1.353

1.840

0.000

0.769

0.560

0.000

0.748

0.000

0.076

0.000

0.003

0.000

0.461

0.000

0.0000

0.5871

2.8208

50.2222

20.4293

12.0540

3.2488

3.6206

0.0000

1.7594

1.0198

0.0000

0.1844

0.0000

1.4232

0.0000

0.1128

0.0000

0.0291

0.0000

0.7371

0.2793

0.000

4.130

2.813

58.455

17.170

8.454

1.991

2.400

0.000

1.107

0.710

0.000

0.061

0.000

1.013

0.000

0.098

0.000

0.012

0.000

0.585

0.093

Toluene

0.166

0.126

0.1768

0.156

Other C'8s

0.000

0.8700

0.290

N-Octane

0.304

0.247

0.0000

0.184

Ethylbenzene

0.008

0.007

0.0076

0.008

M&P Xylenes

0.071

0.074

0.1086

0.085

O-Xylene

0.000

0.0000

0.000

Other C9's

0.000

0.0000

0.000

N-Nonane

0.088

0.0000

0.059

Other C10's

0.000

0.0000

0.000

N-Decane

0.027

0.048

0.0000

0.025

Undecanes(11)

0.000

0.0000

0.000

Totals:

100%

Total VOC:

12.9310%

13.4280%

25.6315%

17.3302%

Total HAP:

1.2220%

1.0340%

1.8581%

1.3714%

¹Air Pollution Testing, Inc. (2016, September). Southern Ute Indian Reservation Flash Liberation Analyses.

Figure 50 – Average Gas to Water and Gas to Condensate Ratios for NonRegistered Sources on the Southern Ute Indian Reservation – September

2016¹

Average Gas/Water and Gas/Condensate Ratios for the Southern Ute Reservation –

September 2016

Gas/Water

Gas/Condensate

(scf/bbl)

1.8

10.1

6.1

9.1

1.4

30.3

3.7

-- -5.9

-- -1

-- -3.3

16.5

¹Air Pollution Testing, Inc. (2016, September). Southern Ute Indian Reservation Flash Liberation Analyses.

Flash Emission Calculation Methodology:

Flash emissions from produced water, condensate, and oil tanks were calculated using

the Gas Oil Ratio Sampling calculation methodology, and the average gas composition

and gas to water and gas to condensate values developed by the AQP from flash

liberation sampling data obtained in 2016 from well-sites on the Reservation. Tank

throughput values in barrel per day were either reported values or the assumed values

developed by AQP, as described previously in this section. Flash emission totals for the

Reservation were developed for each individual operator using either reported or

assumed liquid throughput values and multiplying emissions by number of

corresponding tanks reported.

Example Gas Oil Ratio Calculation for Flash Emissions:

HC Emissions = ((Q)(Rs) x (MWtv) x (lb-mol/379.4 scf) x (365 days/year) x (ton/2000

lb))

Where:

Q = oil, condensate, or water production, bbl/day

Rs = measured gas-oil, gas-condensate or gas-water ratio, scf/bbl

MWtv = stock tank gas Molcular weight, lb/lb-mol

Liquid Storage Tank Loadout Emissions

Data Collection and Assumptions:

Tank loadout emissions were calculated by conservatively assuming that all liquid

storage tanks are unloaded manually by truck, and not sent through pipeline. Emission

factors and emission calculations were derived from Section 5.2 of EPA AP-42 for

Transportation and Marketing of Petroleum Liquids. Loading was assumed to be

submerged fill and the saturation emission factor for submerged dedicated normal

service was selected for calculating loading losses. Truck tank capacity was assumed to

be 100 bbl per loadout event and reported or assumed liquid production numbers were

used for calculating the number or loadout events per year. Each loadout event was

assumed to be one-hour in duration and the assumed annual hours of unloading

operations for each operator were directly correlated to the reported or assumed annual

liquid production. Molecular weight and true vapor pressure values were derived from

TANKS model runs for produced water and condensate.

Example Tank Loadout Emissions Calculation Methodology:

Tank loadout emissions are calculated using two separate calculations, a first equation is

used to estimate the total molecular weight of loading emissions losses and then a

second equation is used to estimate the total emission rate on a pollutant basis. Both

calculations are displayed below:

Loading Losses Calculation:

L = 12.46 x (S) x (P) x ((MW)/T) x (1-eff)

Where:

L=Loading Losses (lb/1000 gallons)

S = Saturation Factor

P = True Vapor Pressure (Pva @ T)

MW = Molecular Weight (lb/lb-mol)

T = Temperature

E = Control Efficiency of Loading

Total Emission Rate Calculation

Tons Per Year = (TE x WT%) x (OH)/2000

Where:

TE = Total Emission Rate (lb/hr)

WT% = Component Weight Percentage from Flash Gas Analysis

OH = Annual hour of operation

Liquid Storage Tank Greenhouse Gas Emissions

Produced Water Tank Greenhouse Gas Emissions:

Greenhouse gas (GHG) emissions for produced water storage tanks were calculated

using the emission factors and methodology from the American Petroleum Institute

document titled Compendium of Greenhouse Gas Emissions for the Oil and Gas

Industry.21 API emission factors are based on inlet separator pressures and an assumed

inlet pressure of 71.67 psi was developed for this emission inventory by averaging

pressures measured during the AQP’s 2016 flash gas sampling conducted on the

Reservation.

Example Calculation for Produced Water Tank GHG Emission

CH4 = (PR) x (O) x (EF)

Where:

CH4 = annual CH4 emissions (ton/yr)

PR = production rate (bbl/day)

O = operation (days/yr)

EF = emission factor (ton/1000 bbl)

Condensate and Oil GHG Emissions:

GHG emissions from condensate and oil tanks were calculated using the methodology

for atmospheric pressure fixed roof storage tanks receiving hydrocarbon produced

liquids from onshore petroleum and natural gas production outlined in §98.233(j) of 40

CFR Part 98 Subpart W (Subpart W). Annual volumetric GHG emissions were

calculated using the emission factors and equations W-15 from §98.233(j)(3) of Subpart

American Petroleum Institute. (2009). Compendium of Greenhouse Gas Emissions Methodologies for the Oil

and Gas Industry. Retrieved from htp://www.api.org/~media/files/ehs/climatechange/2009_ghg_compendium.ashx.

W. Volumetric GHG emissions were converted to mass emissions using equation W-36

from §98.233(u)(2)(v) of Subpart W.

Example Condensate and Oil GHG Calculations:

Annual Volumetric GHG Emissions - Equation W-15 of 40 CFR 63, Subpart W

Es,i = EFi x Count x 1000

Where:

Es,i = Annual total volumetric GHG emissions (either CO2 or CH4) at standard

conditions in cubic feet

EFi = Population emission factor for separators, wells, or non-separator equipment in

thousand standard cubic feet per separator, well, or non-separator equipment per year,

for crude oil use 4.2 for CH4 and 2.8 for CO2 at 60 °F and 14.7 psia, and for gas

condensate use 17.6 for CH4 and 2.8 for CO2 at 60 °F and 14.7 psia.

Count = Total number of separators, wells, or non-separator equipment with annual

average daily throughput less than 10 barrels per day. Count only separators, wells, or

non-separator equipment that feed oil directly to the storage tank.

1,000 = Conversion from thousand standard cubic feet to standard cubic feet.

Annual Mass Based GHG Emissions – Equation W-36 of 40 CFR 63, Subpart W:

Mass,i = (Es,i) x (pi)

Where:

Mass,i = GHG mass emissions kg/yr

Es,i = GHG volumetric emissions in scf

pi = Density of GHG

Calculation to convert kg/yr from kg/yr to tons/yr

tpy = (Mass,I x 2.20462)/2000

Total Liquid Storage Tank Emissions

Total liquid storage tank emissions from working and breathing losses, flash emissions,

tank loadout, and GHG emissions on the Reservation are displayed in below in Figure

51 and Figure 52. Emissions are displayed by tank contents and capacity.

Figure 51 – 2015 VOC, HAP, and GHG Emission Totals on the Southern Ute

Indian Reservation in Tons per from Liquid Storage Tanks by Tank Count,

Content and Capacity

2015 Liquid Storage Tank Counts and Emission Totals on the Southern Ute

Indian Reservation in Tons per Year

Tank Contents and Capacity

Produced Water 0-210 bbl

Produced Water 221-300 bbl

Produced Water 301-400 bbl

Produced Water 401+ bbl

Condensate 0-210 bbl

Condensate 211-300 bbl

Oil 0-210 bbl

Oil 221-300 bbl

Oil 301-400 bbl

Oil 400+ bbl

Tank

Count

412

337

209

245

VOC

3.4

37.0

10.3

12.3

49.3

52.7

9.0

28.1

2.6

2.9

HAP

0.8

15.7

3.0

3.4

0.0

0.1

0.2

0.0

GHG

(CO2e)

16.8

328.7

61.8

71.5

596.9

397.9

52.5

112.1

11.9

7.2

Total Tank Count and Total Emissions

1,385

207.7

23.2

1,657.3

Figure 52 - 2015 VOC, HAP, and GHG Emission Totals on the Southern Ute

Indian Reservation in Tons per from Liquid Storage Tanks by Tank Count,

Content and Capacity

E. External Combustion Sources

Description of Sources

Natural gas-fired external combustion sources are widely used by the natural gas

industry as tank heaters, heated separators, reboilers, and boilers.

Data Collection

The ICR required each operator to report the total number of heaters and boilers

operated by their company on the Reservation. Heater and boiler counts were reported

according to heat rate range in MMBTU/hr. Operators were also given the option to

report average heater and boiler operating hours to override the AQP’s assumed

operating hours. A description the AQP’s assumed values is included in the emission

calculation discussion.

Assumptions

If no hours of operation were reported in the ICR, AQP assumed heaters to operate 24

hours per day for half of the year (183 days per year) which equates to 4,392 hours per

year. Boilers were assumed to operate for 24 hours per day, 365 days a year, which

equates to 8,760 hours per year.

Emission Calculation Methodology

Criteria pollutant and HAP emissions for external combustion sources were calculated

using the emission factors from EPA AP-42 Chapter 1.4 for uncontrolled natural gasfired external combustion sources, the maximum heat rating from each heat rating

category reported in the ICR, a default natural gas heating value of 1,020 Btu/scf, and

assumed or reported operating hours.

As explained in EPA AP-42 Chapter 1.4, a default natural gas heating value of 1,020

Btu/scf shall be used to convert the emission factor from lbs/MMscf to lbs/MMBtu.

GHG emissions were calculated using the Tier 1 calculation methodology, the natural

gas emission factors from Tables C-1 and C-2 of 40 CFR Part 98, and assumed or

reported operating hours.

Example Calculations

Criteria and HAP Example Calculations:

lb/hr = (EF/HV) x (HR)

Where:

EF = Emission Factor (lb/MMscf)

HV = Default Heat Value of Natural Gas fuel (Btu/scf)

HR = Heat Rate of Boiler (MMBtu/hr)

Example NOx lb/hr calculation for 0.5 MMBtu/hr natural gas-fired boiler:

lb/hr = (0.06/1,020) x 0.5 = 2.94 E-5

tpy = (lb/hr) x OH/2000

Where:

(lb/hr) = Emission Rate

OH = Annual Operating Hours

2000 = Pounds per ton

Example NOx tpy calculation for 0.5 MMBtu/hr natural gas-fired boiler operating 4392

hours per year:

tpy = (2.94E-5) x (4392/2000)= 6.46E-5

GHG Example Calculation:

Tier 1 Calculation Methodology:

= (1 x 10-3) x (Fuel) x (EF)

Where:

Fuel = volume of fuel combusted per year (MMbtu/yr)

EF = fuel specific default emission factor, from tables C-1 and C-2 of Part 98

(kg/MMBtu)

1 x 10-3 = conversion factor from kilograms to metric tons

Emissions

Criteria pollutant, HAP and GHG emissions from external combustion sources located at

non-registered oil and gas sources on the Reservation for calendar year 2015 are

displayed below in Figure 53. Emissions are displayed by unit count and heat rating in

MMBtu/hr.

Figure 53 - Criteria Pollutant, HAP, and GHG Emissions from Heaters and Boilers

at Non-registered Oil and Gas Sources on the Southern Ute Indian Reservation in

Tons per Year, Displayed by Unit Count and Heat Rating in MMBtu/hr

2015 Emissions from Heaters and Boilers at Non-registered Oil and Gas

Sources in Tons per Year, Displayed by Unit Count and Heat Rating in

MMBtu/hr

Equipment

Type and

Heat Rating

Heaters 0-3

MMBtu/hr

Boilers

11-25

MMBtu/hr

Total

Unit

Count

NOx

VOC

SO2

PM10

HAP

CO2e

742

470.4

25.9

0.0

35.5

395.1

8.9

561,830

748

64.4

534.8

3.5

29.4

0.0

4.9

40.4

54.1

449.2

1.2

10.1

76,933

638,763

F. Equipment Leaks and Fugitive Emissions

Description of Sources

Natural gas leaks from components commonly used in the natural gas industry result in

emissions of methane, CO2, VOC, and HAP. Components include: valves, pumps,

pressure relief valves, connectors, flanges, and, open-ended lines. These components are

ancillary equipment to many larger equipment source types including: headers,

separators, heaters, filters, engines, compressors, dehydration units, and storage tanks.

Data Collection

The ICR provided operators with the option to report average fugitive component counts

for single and co-located well-sites. In the absence of ICR provided component counts,

the AQP relied on assumed component counts, as detailed below.

Assumptions

Fugitive component counts were assumed based on component counts for natural gas

production contained in the Canadian Association of Petroleum Producers (CAPP)

document titled Guide to Calculating Greenhouse Gas Emissions.22 Component counts

for single and co-located well-site locations are displayed below in Figure 54.

Canadian Association of Petroleum Producers. (2003). Guide to Calculating Greenhouse Gas Emissions.

Retrieved from http://www.capp.ca/publications-and-statistics/publications/241974

Figure 54 – Assumed Fugitive Emission Component Counts at Single and CoLocated Natural Gas Well-Sites on the Southern Ute Indian Reservation

Assumed Component Counts for Well-Site Locations on the Southern Ute Indian

Reservation

Component Type-Service

Valves-Gas/Vapor

Connectors-Gas/Vapor

Open-Ended LinesGas/Vapor

Component

count for a

Single well

Component

count for Two

co-located

wells

120

Component

count for

Three Colocated wells

180

Component

count for

Four Colocated wells

240

Emission Calculation Methodology

VOC and HAP Emission Calculations:

VOC and HAP emissions from equipment leaks and fugitive emissions were calculated

using the average emission factor approach and the gas/vapor total organic compound

(TOC) emission factors for oil and gas production from Table 2-4 of Chapter 2.3 of EPA

AP-42. The TOC emission factor for gas/vapor was chosen as the most representative of

production on the Reservation in CY2015 and is the most conservative emission factor

available. TOC emissions were calculated by multiplying the gas/vapor emission factor

by component counts from Tab 1 of the CAPP, the component count that corresponds to

the number of wells and typical well-site equipment configurations reported by each

recipient of the ICR, and an assumed 8,760 hours of annual operation. VOC and HAP

emissions were then derived by multiplying the TOC emissions by the VOC and HAP

molecular weight fraction percentages of an assumed extended natural gas analysis for

the Reservation. If component counts were provided by operators in the ICR, emissions

for their company’s productions were calculated using their reported counts in place of

the CAPP component counts.

GHG Emission Calculations:

GHG emissions from equipment leaks and fugitive emissions were calculated using the

equipment leak by population count methodology and equation W-32A of Subpart W of

40 CFR Part 98 (Subpart W). Input values for the W-32A equation included the

emission factors for gas leakage from western U.S. gas service from Table W-1A of

Subpart W, the component counts provided in the ICR, the population emission factors

listed for equipment types in Tables W-1A and W-4 through W-7 of Subpart W, an

assumed 8,760 hours of annual operation, and the methane and CO2 molecular weight

percentage rates from an assumed extended natural gas analysis. Final GHG values

were converted from volume to mass using equation W-36 of Subpart W and the gas

densities from §98.233(u)(2)(v) of Subpart W.

Example Calculations

VOC and HAP Emission Calculation Methodology:

VOC or HAP Emissions = AP-42 Average Emission Factor for Gas Valves x API

Compendium Generic Valve Count x VOC or HAP Percent Weight= lb/hr VOC or HAP

emissions

VOC Emissions (lb/hr) = (0.0099 lb/hr/gas valve) x (400 valves) x (0.06% VOC) =

0.0026lb/hr

VOC Emissions (tpy) = (0.0026 lb/hr) x (8760 hr/yr) x (Ton/2000 lb) = 0.0112 tons/year

GHG Emission Calculation Methodology – Equation W-32A of 40 CFR 98 Subpart W:

GHG Emissions (scf/yr) = (Count) x (Efs,e) x (GHGi) x (Te)

Where:

Count = Total number of the emission source type at the facility.

EFs,e = Population emission factor for the specific emission source type, as listed in

Tables W-1A and W-4 through W-7

GHGi = Concentration of GHG (CH4 or CO2) in produced natural gas

Te = Average estimated time that each emission source type associated with the

equipment leak emission was operational in the calendar year, in hours

Example Methane Calculation for Valves:

scf/yr = (50 x 0.121) x (0.922564147) x (8760) = 48,894.05scf/yr

To convert from scf/yr to scf/hour divide by 8760

Scf/hr = 48,894.05/8760 =5.58

To derive an scf/hr amount, divide scf/yr by annual hours of operation

Volume to Mass Equation - Equation W-36 of 40 CFR 98 Subpart W

Massi = (Es,i) x (pi) x 10^-3

Where:

Massi = Mass emissions in metric tons

Es,I = Volumetric emissions at standard conditions, in cubic feet

Pi = Density of GHG

Equation altered to give answer in lb/hr

Mass I = (Es,I) x (pi) x (lb/kg)

Example:

lb/hr = 5.58 x 0.0192 x 2.20462 = 0.23 lb/hr

To calculate annual emissions in ton per year, multiply lb/hr rate by 8760 hours and

divide by 2,000 lb/ton

tpy Methane = (0.23 x 8760)/2,000 = 1.03

Emissions

Volatile organic compound, HAP and GHG emissions from equipment leak and fugitive

emission sources located at non-registered oil and gas sources on the Reservation for

calendar year 2015 are displayed below in Figure 55.

Figure 55 – 2015 Emissions of VOC, HAP, and GHG from Equipment Leaks and

Fugitive Emission Sources at Non-Registered Oil and Gas Sources on the Southern

Ute Indian Reservation in Tons per Year

2015 Emissions from Equipment Leaks and Fugitive Emission Sources at

Non-registered Oil and Gas Sources in Tons per Year

Pollutant

VOC

HAP

CO2e

Emission Totals

252.9

15.1

209,593

G. Natural Gas Driven Pneumatic Devices

Description of Sources

Natural gas-driven pneumatic controllers and pumps are used in the oil and natural gas

industry for maintaining liquid levels, pressures, pressure differentials, and temperature.

Many devices are designed to leak, or “bleed”, natural gas and in doing so emit natural

gas containing methane, CO2, VOC, and HAP. Pneumatic devices are classified as high

or low continuous bleed controllers, intermittent bleed controls, or zero bleed

controllers.

Data Collection

The AQP assigned an assumed value for the average number of pneumatic devices

located at a single wellsite from the 2014 Environmental Science and Technology report

titled Methane Emissions from Process Equipment at Natural Gas Production Sites in

the United States.23 The assumed pneumatic device count value was provided in the ICR

and operators were provided the opportunity to override the assumed value with values

more representative of their operations.

Emission Calculation Methodology

Pneumatic device emissions were calculated by applying the generic natural gas

emission factors and supply pressure coefficients found in EPA’s April 2014 Report for

Oil and Natural Gas Sector Pneumatic Devices to the AQP’s assumed average device

count or average device counts reported in the ICR.

Example Emission Calculation:

lb/hr = Count x Bleed Rate x R x MW x Y

Where:

Count = total number of devices

Bleed Rate = bleed rate from device (scf/hr/device)

R = Universal gas constant (lb-mol/379.3scf)

MW = molecular weight of the component

Y = volume fraction of component in the vented gas

Example for Methane

lb/hr = 2695 x 58.5 x 1/379.3 x 16.01 x 92% = 577.2 lb/hr

tpy = lb/hr x OH/2000

Where:

lb/hr = emission rate in pounds per hour

OH = annual operating hours

2000 = pounds per ton

Allen, D. (2014). Methane Emissions from Process Equipment at Natural Gas Production Sites in the United

States: Pneumatic Controllers. Environmental Science & Technology, 49, 633-640. Retrieved from

http://pubs.acs.org/doi/pdf/10.1021/es5040156

tpy methane = 577.2 x 8760/2000 = 2528.1 tpy

Emissions

Volatile organic compound, HAP, and GHG emissions from natural gas driven

pneumatic devices on the Reservation during 2015 are displayed below in Figure 56.

Figure 56 - 2015 Volatile Organic Compound, HAP, and GHG Emissions from

Natural Gas Driven Pneumatic Devices at Non-Registered Oil and Gas Sources on

the Southern Ute Indian Reservation in Tons per Year

2015 Emissions from Natural Gas Driven Pneumatic Devices in Tons per Year

Pollutant

VOC

HAP

CO2e

Emission

129.5

7.8

150,493.2

Totals

H. Natural Gas Blowdowns

Description of Sources

Natural gas blowdowns are intentional and unintentional gas releases during

maintenance, routine operations, and emergencies. Blowdowns occur from gas

compressors, compressor startups, gas wellbores, vessels, pipelines, and various

equipment.

Data Collection

The ICR requested emissions resultant from maintenance and emergency natural gas

blowdowns. Due to the burden of capturing actual emissions for each blown down event

at a large number of non-registered sources, emissions from such events are based on

assumptions on the amount of gas released from certain types of blowdowns, the AQP’s

assumed extended gas analysis, and an assumed number of events anticipated during a

calendar year. The ICR provided operators with the opportunity to override the AQP’s

assumed values with values more representative of their operations.

Assumptions

The AQP developed assumed values for the number and time duration of annual

compressor and pipeline blowdowns that occur per year and the volume of natural gas

vented per event. Assumed values were based on information provided by two operators

with a large number of sources on the Reservation. The values assumed for 2015 are

displayed below in Figure 57.

Figure 57 – Assumed Values for Annual Natural Gas Blowdown Events Occurring

at Non-Registered Oil and Gas Sources on the Southern Ute Indian Reservation in

2015

Assumed Values for Annual Blowdown Events on the Southern Ute Indian

Reservation for 2015

Compressors

Annual compressor blowdowns per compressor

Estimated amount of gas lost per blowdown (Mscf/event)

Duration of event (hr/event)

Pipelines

Number of pipeline blowdowns per year

Estimated amount of gas lost per blowdown (Mscf/event)

Duration of event (hr/event)

1.92

Emissions Calculation Methodology

Emissions from natural gas blowdowns were calculated using either the AQP’s assumed

extended gas analysis or reported natural gas analysis, and assumed or reported event

frequencies, duration, and gas loss values.

Example Calculations:

lb/hr = (Totalvented x % vol) x (MW/(R x T))/OH

Where:

Totalvented = total volume of gas vented (scf/yr)

%vol = volume percent of gas component

MW = molecular weight of the component

R = universal gas constant (scf/lb-mol)

T = temperature (60 °F converted to 519.67 °R)

tpy = lb/hr*OH/2000

Where:

lb/hr = emission rate in pounds per hour

OH = annual operating hours

2000 = pounds per ton

Emissions

Emissions from natural gas blowdown activities occurring on the Reservation during

2015 are displayed below in Figure 58.

Figure 58 – 2015 Volatile Organic Compound, HAP, and GHG Emissions from

Natural Gas Blowdowns at Non-Registered Oil and Gas Sources on the Reservation

in Tons per Year

2015 Emissions from Natural Gas Blowdowns on the Southern Ute Indian

Reservation in Tons per Year

Pollutant

VOC

Total HAP

CO2e

Emission Totals

3.3

0.1

4,086.1

I. Well Completion and Re-completion Venting

Description of Sources

Well completions and recompletions, when not employing closed vent system

techniques, also known as “green completions”, release natural gas during the “flow

back” back stage of the process. Flow back is the stage in which drilling fluid and

hydrocarbon reservoir fluids return to the surface prior to well production. Green

completion techniques capture flow back materials, including natural gas.

Data Collection

The number of well completions that occurred in calendar year 2015 were obtained from

the COGCC database, and are displayed below in Figure 59. No data were available for

well recompletions in the COGCC database and an assumed recompletion value of 1%

of all operating wells per year was obtained from the 2015 Colorado Air Resources

Management Modeling Study (CARMMS).24

The ICR also provided the opportunity for operators to report the number of events that

occurred in calendar year 2015, including natural gas lost per event, and completion by

type (conventional or green completion).

ENVIRON International Corp.; Carter Lake Consulting; Environmental Management and Planning Solutions.

(2015). Colorado Air Resources Management Modeling Study. Retrieved from

https://www.blm.gov/co/st/en/BLM_Information/nepa/air_quality/carmms.html

Figure 59 – Wells Completed at Non-Registered Oil and Gas Sources on the

Southern Ute Indian Reservation in 2015¹

Total

Well Completions on the Southern Ute Indian Reservation in 2015

¹Well completion totals were obtained from the COGCC Database.

Assumptions

Fifty percent of all well completions and recompletions were assumed to utilize green

completion technology with no natural gas vented to atmosphere. Conventional well

completions and recompletions were assumed to vent 1,000 Mscf of natural gas per

event. These assumptions were derived by averaging information provided by two

operators with a large number of sources on the Reservation.

For well recompletions, the assumed well recompletion value of 1% of all operating

wells per year was obtained from the CARMMS study and assumed to be accurate and

representative of operations on the Reservation.

All completion and re-completion activities were assumed to be either conventional or

green completions, based on information provided by two large natural gas operators on

the Reservation. Therefore, the AQP did not estimate emissions from flaring events that

may occur during well completion or re-completion activities. Assumed well completion

and recompletion values for 2015 are displayed below in Figure 60.

Figure 60 – 2015 Assumed Values for Well Completion and Recompletion

Activities at Non-Registered Oil and Gas Sources on the Southern Ute Indian

Reservation¹

Assumed Values for Well Completion and Recompletion Activities on the

Southern Ute Indian Reservation -2015

Completion Type

Assumed Values for Well Completion and

Conventional Green

Re-completion Venting

Technology

Percent of completions by type

50%

Estimated amount of gas vented to atmosphere per

1000

event (Mscf/event)

Estimated amount of gas controlled via closed loop

system per event (Mscf/event)

¹Assumed values are based on information provided by two large natural gas operators on the Reservation.

Emission Calculation Methodology

Emissions from well completion and recompletions were calculated using an assumed

extended gas analysis, and reported or assumed event frequencies and gas loss values.

Emissions from drilling engines that are employed during well completion and recompletion activities were not calculated.

Emissions

Emissions from well completion and recompletion venting on the Reservation in

calendar year 2015 are displayed below in Figure 61.

Figure 61 – 2015 Volatile Organic Compound, HAP, and GHG Emissions from

Well Completion and Recompletion Activities at Non-Registered Oil and Gas

Sources on the Southern Ute Indian Reservation

2015 Well Completion and Recompletion Emissions from Non-registered Oil and

Gas Sources on the Southern Ute Indian Reservation in Tons per Year

Pollutant

VOC

Total HAPs

CO2e

Emission Totals

12.1

0.6

15,706.9

J. Typical Well-Site Configuration

Description

The AQP compiled equipment count information collected in the ICR to prepare average

equipment type counts based on the number of natural gas wells located on a single wellpad. This information can be used to gain a better understanding of typical well-site

configurations on the Reservation and to assist with estimating emissions from any

proposed natural gas development schedules.

Average equipment counts at non-registered oil and gas sources on the Reservation are

displayed below in Figure 62 and Figure 63.

Figure 62 – 2015 Average Equipment Counts at Single and Co-Located Well-Sites

Located at Non-Registered Oil and Gas Sources on the Southern Ute Indian

Reservation in Tons per Year

2015 - Average Equipment Counts at Single and Co-Located Natural Gas Well-Sites by

Equipment Type

Number Heater Separator Dehydrators Compressors Produced Condensate Engine

of Wells

Water

Tanks

per Pad

Tanks

0.5

1.0

0.2

0.1

0.8

0.1

0.4

1.3

2.4

0.2

1.4

0.0

1.2

1.6

2.5

0.2

0.1

1.9

0.0

1.5

1.0

3.0

0.0

1.5

0.0

2.5

Figure 63 – Average Equipment Counts at Non-Registered Oil and Gas Wells by

Equipment Type

2. Fruitland Formation Outcrop Natural Gas Seeps

Description of Sources

Naturally occurring methane and CO2 seepage from outcrops of the Cretaceous

Fruitland Formation (Fruitland Outcrop) contribute a significant quantity of the GHG

emissions on the Reservation.

Data Collection

The data used to quantify emissions from the Fruitland Outcrop were provided to the

AQP from the SUIT Department of Energy (SUIT DOE). SUIT DOE collected outcrop

seepage data on an annual basis since 2007 using an independent contractor between

2007. The goal of the study is identification, mapping, and quantification of methane

seeps on the Fruitland Outcrop. A backpack mounted, hand-held gas flux meter

manufactured by WEST Systems is used to measure methane and CO2 soil gas flux

concentrations in moles per meters squared per day (mol/m² day) at thirty-five seep

areas, totaling 53,352,338 square feet (1.9 miles) of ground. The flux concentrations

were then used by the contractor to calculate volumetric methane and CO2

concentrations for 2015 in MCFD.

Emission Calculation Methodology

The AQP calculated ton per year emission rates for methane and CO2 by converting the

volumetric methane and CO2 flux concentrations from MSCF to SCFD and then

dividing the flux concentrations by the ideal gas law constant and multiplying the

constants by the molecular weight of each gas. GHG emissions in CO2 equivalence

(CO2e) were calculated by multiplying methane emissions by the EPA’s global

warming potential factor of 25 for methane.

Example Calculations

Calculation to Convert Flux Rate in SCFD to lb/day

lb/day = Flux/Ideal Gas Law Conversion Factor*molar mass

Where:

Flux = Volumetric gas flux in SCFD

Ideal Gas Law Conversion Factor = 379.3 SCF/mol

Molar Mass = g*Mol¯¹ (CH4 = 16.04; CO2 = 44.01)

lb/day Methane = 3,097,000/379.3*16.04 = 1,053,658 lb/day Methane

Calculation to convert lb/day to tpy

tpy = lb/day/2000/ton*365 days

Emissions

Emission calculations for methane, CO2 and total GHG in CO2e are displayed below in

Figure 64:

Figure 64 - 2015 Emissions of Methane, CO2, and total GHG in CO2 Equivalence

2015 Fruitland Outcrop Methane, CO2, and Total GHG (CO2e) Emissions in Tons per

Year

Methane

192,293

CO2

229,097

Total GHG (CO2e)

5,036,413

3. Gas Stations

Description of Sources

There are five gasoline service stations that operated on the Reservation during calendar

year 2015.

Data Collection

2015 gasoline throughput values were provided to the AQP by representatives of each

gas station, and the throughput are displayed below in gallons per year in Figure 65.

Figure 65 – 2015 Annual Gasoline Throughput at Gasoline Stations Located on the

Southern Ute Indian Reservation in Gallon per Year¹

2015 Annual Gasoline Throughput in Gallons per Year

Total Gasoline Throughput

1,785,476

¹Reported throughput totals for one gasoline station included both diesel and gasoline and were corrected

to include only gasoline. The method used for correcting this value is explained below in the Assumptions

section.

Assumptions

AQP assumed that gasoline throughput values reported by gas station representatives are

valid. One gasoline station provided an aggregate throughput value for diesel and

gasoline fuel. The AQP corrected this throughput value to only include gasoline based

on the average of gasoline to diesel fuel dispensing rates contained in three information

sources assumed to be accurate for estimating the amount fuel dispensed in Colorado

and the U.S. in 201525,26,27

Due to the absence of emission factors for diesel fuel dispensing in EPA AP-42 Section

5.22, the AQP assumed emissions from diesel fuel dispensing to be negligible and did

not calculate emissions for this activity. EPA AP-42 Section 5.2.2, also assumes a

U.S. Energy Information Administration. (2016). Petroleum & Other Liquids. Retrieved from

http://www.eia.gov/petroleum/

Statista: The Statistics Portal. (2016). U.S. motor gasoline and distillate fuel oil consumption by the

transportation sector from 1992 to 2015 (in 1,000 barrels per day). Retrieved from

https://www.statista.com/statistics/189410/us-gasoline-and-diesel-consumption-for-highway-vehiclessince-1992/

American Fuels: Alternative Fuels News and Commentary. (2014). 2013 Gasoline Consumption. Retrieved from

http://www.americanfuels.net/2014/03/2013-gasoline-consumption.html

negligible methane content from gasoline evaporative emissions; therefore, AQP did not

calculate GHG emissions for gas stations.

Emission Calculation Methodology

Gas station emissions were calculated using the Tribal Emissions Inventory Software

Solutions (TEISS) emissions calculator for gasoline service stations.28 The calculator

employs emission factors from EPA AP-42 Section 5.2.2. Total reported fuel

throughputs were input into the TEISS emissions calculator for two stages of gasoline

service station emissions. Stage 1 includes underground tank filling and submerged

filling. Stage 2 includes underground tank breathing and emptying, vehicle refueling

displacement losses (uncontrolled), and spillage.

Emissions

Total VOC emissions from gas stations on the Reservation during 2015 are displayed

below in Figure 66.

Figure 66 - 2015 Volatile Organic Compound Emissions from Gasoline Dispensing

Stations on the Southern Ute Indian Reservation

2015 Gas Station Emissions on the Southern Ute Indian Reservation in Tons

per Year

Annual

Reservation

Gasoline

Throughput

(gallons)

1,785,476

Total:

Station Operation Type

Stage 1: Underground Tank

Filling, Submerged Filling

Stage 2: Underground Tank

Breathing & Emptying,

Vehicle refueling

displacement losses

(uncontrolled), and

Spillage

Pollutant

Emissions

VOC

6.5

VOC

11.3

17.8

Institute for Tribal Environmental Professionals. (2016). Tribal Emissions Inventory Software Solution Version

3.6.26. Retrieved from http://www7.nau.edu/itep/main/air/air_aqt_teiss.

4. Aviation Gasoline

Description of Sources

Emission estimates for aviation gasoline and the amount of lead in the leaded gasoline

for counties were last developed by EPA for calendar year 2014. Lead is an additive in

aviation gasoline used for piston-engine aircrafts (either general aviation or air taxi) to

increase the fuel octane and prevent valve seat decline, which is a safety concern.

Data Collection

Data was obtained from the EPA NEI for calendar year 2014. EPA’s data collection

methodology is described in EPA’s 2008 Technical Support Document titled Lead

Emissions from the Use of Leaded Aviation Gasoline in the United States.29

Assumptions

The AQP assumed EPA’s calendar year 2014 EPA’s aviation gasoline emission

estimates for La Plata County and Animas Air Parks would be the most representative

emission estimates available for calendar year 2015.

Emissions

Volatile Organic Compound and HAP emissions from aviation gasoline usage on the

Reservation in 2015 is displayed below in Figure 67.

Figure 67 – 2015 Volatile Organic Compound and HAP Emissions from Aviation

Gasoline on the Southern Ute Indian Reservation in Tons per Year¹

2015 Aviation Gasoline Emissions for the Southern Ute Indian

Reservation in Tons per Year

Aviation Gasoline Stage

Stage 1 Fueling Pollutants

VOC

HAP

Stage 2 Fueling Pollutants

VOC

HAP

Combined Stage 1 and Stage 2 Fueling

Emissions

Total VOC Emissions

Total HAP Emissions

Emissions

13.2

0.7

0.4

0.0

Total Aviation Fueling Emissions

13.6

0.7

U.S. EPA. (2008, October). Lead Emissions from the Use of Leaded Aviation Gasoline in the United States.

¹Emissions for aviation gasoline fueling are estimated from data sourced from the 2014 EPA National

Emission Inventory Database and assumed to be realistic estimations of aviation gasoline fueling

emissions for 2015.

5. Gravel Pits

Description of Sources

Ten sand and gravel pits operated within the exterior boundaries of the Reservation

during calendar year 2015. Data was collected from the Colorado Division of

Reclamation Mining and Safety (DRMS) database30. The emissions from pits on the

Reservation were estimated by scaling down the emissions estimates reported to the

2014 EPA NEI for La Plata, Archuleta, and Montezuma counties for calendar year 2014.

Data Collection

The AQP researched active gravel pits located within the exterior boundaries of the

Reservation through the DRMS ArcGIS data set. AQP used ArcGIS and the “select by

attribute” feature to select the gravel, sand, and combined sand and gravel permits

located within the exterior boundaries of the Reservation in La Plata, Archuleta, and

Montezuma counties. Permits with an active status for 2015 were then cross-referenced

with the DRMS Imaged Document data to determine if there was production in 2015.

This methodology determined ten active gravel pits in La Plata County and no active

gravel pits in Archuleta and Montezuma counties during 2015.

Emissions

Gravel pit emissions for La Plata County were obtained from the EPA’s calendar year

2014 Nonpoint Emission Inventory for gravel pits. Emission totals were reported to NEI

for La Plata and Archuleta counties as a whole and not for individual gravel pits. To

derive emission estimates for the Reservation, the reported emission totals for La Plata

County were multiplied by the percentage of active gravel pits that are located within the

exterior boundaries of the Reservation. For example 25.64% of active gravel pits in La

Plata County are within the Reservation boundaries, therefore, gravel pits on the

Reservation account for 25.64% percent of emissions in La Plata County. Emission

totals for 2015 are displayed below in Figure 68.

Colorado Division of Reclamation Mining and Safety. (2016). Active Hardrock Permits. Department of Natural

Resources. Retrieved from http://mining.state.co.us/Reports/Pages/GISData.aspx.

Figure 68 – Emissions of PM10 from Active Gravel Pits on the Southern Ute

Reservation in 2015

2015 Gravel Pit Emissions on the Southern Ute Indian Reservation in Tons per

Year

County

Pollutant

Description

County

Emissions

175.3

Percent(%) of

Active

Permitted Pits

within SUIR

25.6%

La Plata

PM10

Archuleta

PM10

29.2

0.0%

0.0

50.5

6. Residential Heating

A. Description of Sources: Fireplaces and Wood Burning Stoves

Fireplaces and wood burning stoves are a significant source of residential heating within

the exterior boundaries of the Reservation. The predominant types of solid fuel

available are pinyon-juniper, pine, and aspen.

Data Collection

The U.S. Census 2010-2014 American Community Survey 5-Year Estimate (survey)

was used to determine the number of households on the Reservation that use fireplaces

or wood burning stoves for residential heating.31 The survey estimates the total number

of households on the Reservation that used wood as a heating source during the fiveyear survey period.

The U.S. Energy Information Administration, Office of Energy Consumption and

Efficiency Statistics’ 2005 Residential Energy Consumption Survey (EIA) was used to

obtain the average number of cords used within a year at an average household.32 Table

US8 of the EIA lists that an average household uses an average of 1.6 cords per year.

The U.S. Census reported 894 households on the Reservation use fireplaces or

woodstoves as the primary heating source.

Fireplace and wood burning residential heating data for the Southern Ute Indian

Reservation in 2015 is displayed below in Figure 69.

U.S. Census Bureau. (2016). American Community Survey. Retrieved from

https://factfinder.census.gov/faces/nav/jsf/pages/index.xhtml

U.S. Energy Information Administration. (2005) Table US8 Average Consumption by Fuels Used, 2005 Physical

Units per Household

Figure 69 – 2015 Fireplace and Wood Burning Stove Residential Heating Data for

the Southern Ute Indian Reservation

2015 – Fireplace and Wood Burning Residential Heating Data for the

Southern Ute Indian Reservation

Homes Heated

Average Fuel Use

Unit of

Total Number of

with Wood

per Household/Year Measurement

Cords used in

2015

894

1.6

Cords

1,430.4

Emission Calculation Methodology

Emissions for residential fireplace and wood burning stoves were calculated using the

Tribal Emissions Inventory Software Solutions (TEISS) emission calculator. The

calculator employed emission factors from EPA AP-42 Section 1.10.2, which may be

adjusted based on the units of data input.

Example Calculation

894 households x 1.6 cord = 1,430.4 cords (input into TEISS)

household

Assumptions

The U.S. Census surveyed 5,159 households with an estimated uncertainty of ± 96

households using fireplaces or woodstoves for home heating. The stove type entered

into TEISS was conventional pre-phase I.

Emissions

Total criteria pollutant and GHG emissions from residential fireplace and wood-burning

stoves on the Reservation in 2015 are displayed below in Figure 70.

Figure 70 – 2015 Criteria Pollutant and GHG Emissions from Fireplaces and Wood

Burning Stoves on Southern Ute Indian Reservation in Tons per Year

2015 Fireplace and Wood Burning Stoves Emissions for the Southern Ute

Indian Reservation in Tons per Year

NOx

SO2

PM10

VOC

CO2e

Pollutant

Total

1.9

0.3

20.5

154.5

35.5

2,851.9

B. Description of Sources: Propane Heating

Liquid propane (LP) is the dominant source of residential heating on the Reservation

and in Southwest Colorado.

Data Collection

The U.S. Census 2010-2014 American Community Survey 5-Year Estimate was used to

determine the number of households on the Reservation that use LP gas as a source of

heating.

The U.S. Energy Information Administration, Office of Energy Consumption and

Efficiency Statistics’ 2009 Residential Energy Consumption Survey (EIA) was used to

obtain the average of LP used per household. The survey estimated the average number

of gallons of LP used within a year for an average household.33 The U.S. Census

reported 2,405 or 46.6% of households on the Reservation use LP gas as the primary

heat source and the EIA estimated 768 gallons of LP gas are burned per year in

households in Colorado.

Liquid Propane residential heating data for the Southern Ute Indian Reservation in 2015

is displayed below in Figure 71.

Figure 71 - 2015 Liquid Propane Residential Heating Data for the Southern Ute

Indian Reservation

2015 – Liquid Propane Residential Heating Data for the Southern Ute

Indian Reservation

Homes Heated

Average Fuel Use

Unit of

Total Gallons

with Liquid

per Household/Year Measurement

used in 2015

Propane

2,405

768

Gallons

1,847,040

Emission Calculation Methodology

Emissions for residential LP gas heating were calculated using the TEISS emission

calculator. The calculator employed emission factors from AP-42 Section 1.5.

Example Calculation

2,405 households x 768 gallons = 1,847,040 gallons *(input into TEISS)

household

U.S. Energy Information Administration. (2009). Table CE2.5 Household Site Fuel Consumption in the West

Region, Totals and Average, 2009 Physical Units. Retrieved from https://www.eia.gov/consumption/

Assumptions

The U.S. Census surveyed 5,159 households with an estimated uncertainty of ± 122

households that use LP gas for home heating. The actual sulfur content of LP gas on the

Reservation is unknown and the default sulfur content of 0.54 grains/100 ft3 was used in

the TEISS emission calculator.

Emissions

Total criteria pollutant and GHG emissions from residential LP gas usage on the

Reservation in 2015 is displayed below in Figure 72.

Figure 72 – 2015 Criteria Pollutant and GHG Emissions from Liquid Propane Gas

Heating at Residential Sources on Southern Ute Indian Reservation in Tons per

Year

2015 Liquid Propane Gas Heating Emissions for the Southern Ute Indian

Reservation in Tons per Year

Pollutant

NOx

SO2

PM10

VOC

CO2e

Total

12.4

0.1

0.0

3.5

0.5

10,609.9

C. Description of Sources: Natural Gas Heating

Natural gas is a prevalent residential heating fuel on the Reservation.

Data Collection

The U.S. Census 2010-2014 American Community Survey 5-Year Estimate (survey)

was used to determine the amount of households on the Reservation that use natural gas

for residential heating. The survey estimates the total number of households on the

Reservation that used natural gas as a heating source during the five-year survey period.

The U.S. Energy Information Administration, Office of Energy Consumption and

Efficiency Statistics’ 2009 Residential Energy Consumption Survey (EIA) was used to

obtain the average of natural gas used per household. The survey estimated the average

cubic feet of natural gas used within a year for an average household. The U.S. Census

reported 1,031 or 20% of households on the Reservation use natural gas as the primary

heat source and the EIA estimated 80 thousand cubic feet (80MMcf) of natural gas are

burned per year in households in Colorado.

Natural Gas residential heating data for the Southern Ute Indian Reservation in 2015 is

displayed below in Figure 73.

Figure 73 - 2015 Natural Gas Residential Heating Data for the Southern Ute Indian

Reservation

2015 – Natural Gas Residential Heating Data for the Southern Ute Indian

Reservation

Homes Heated with Average Fuel Use

Unit of

Total MMcf

Natural Gas

per Household/Year Measurement

used in 2015

1,031

MMcf

82,480

Emission Calculation Methodology

Emissions for residential natural gas heating were calculated using the TEISS emission

calculator. The calculator employed emission factors from EPA AP-42.

Example Calculation

1,031 household x 80,000 cf gas = 82,480 thousand cf gas (input into TEISS)

household

Assumptions

The U.S. Census surveyed 5,159 households with an estimated uncertainty of ± 120

households that use natural gas for home heating.

Emissions

Total criteria pollutant and GHG emissions from residential natural gas heating sources

on the Reservation in 2015 are displayed below in Figure 74.

Figure 74 – 2015 Criteria Pollutant and GHG Emissions from Natural Gas Heating

at Residential Sources on Southern Ute Indian Reservation in Tons per Year

2015 Natural Gas Heating Emissions for the Southern Ute Indian

Reservation in Tons per Year

Pollutant

NOx

SO2

PM10

VOC

CO2e

Total

3.9

0.0

1.6

0.2

4,494.8

7. Wildland Fires and Prescribed Burns

Description of Activity

The forest on the Reservation is predominantly comprised of pinyon-juniper woodlands

with ponderosa, gambel oak, aspen and sub-alpine forest at higher elevation areas. The

forest is prone to wildfire and prescribed burns are utilized as a forest management strategy

to help prevent catastrophic fires, improve wildlife habitat and improve overall forest health.

Wildfires and prescribed burns can be significant sources of air pollution on the Reservation

and the Four Corners area.

Data Collection

Wildland and prescribed burn fire (forest fire) data for calendar year 2015 were obtained

from the Bureau of Indian Affairs (BIA) and the Southern Ute Agency Fire Management

Division.34 The initial data identified 23 fires (21 wildfires and 2 prescribed fires). To

ensure accuracy, AQP accessed another data set from the U.S. Department of Agriculture

Federal Fire Occurrence Website.35 The U.S. Department of Agriculture data set identified

four additional wildfires reported by the U.S. Forest Service (USFS) and the National Park

Service (NPS). Data sets included type of fire, latitude and longitude of fire perimeter, and

acres burned.

Emission Calculation Methodology

Forest fire emission estimates were calculated using the USFS BlueSky Playground web

tool (BlueSky).36 BlueSky is comprised of several internal USFS datasets and modeling

programs, including the Fuels Characteristic Classification System fuel information dataset

(FCCS), the CONSUME3 fuel consumption model, and the FEPS emission factors model.

Forest fire data including latitude and longitude and acres burned are input into BlueSky and

BlueSky selects the correct default model input values based on the fire location. Input

values include available fuel load, fuel consumed, emission factors, and meteorological

forecast data. “Dry” was selected for the fuel moisture value. Forest fire event by FCCS

fuel bed type are displayed below in Figure 75.

Figure 75 – 2015 Forest Fire Occurrence on the Southern Ute Indian Reservation

by Fuels Characteristic Classification System Fuel Bed Type and Acres Burned

2015 Forest Fires on the Southern Ute Reservation according to FCCS

Fuelbed Type and Acres Bured

FCCS Fuel Bed Description

Bare Ground

Number of

Fires

Acres

Burned

0.5

Bureau of Indian Affairs Fire Management. (2015). Southern Ute 2015 Fire Occurrence

U.S. Department of Interior and U.S. Department of Agriculture. (2016). Federal Wildland Fire Occurrence

Data. Retrieved from Federal Fire Occurrence: http://wildfire.cr.usgs.gov/firehistory/index.html.

U.S. Forest Service AirFire Research Team. (2016). BlueSky Playground (Version 2.0 beta). Retrieved from

http://playground.airfire.org/home.php

Ponderosa Pine Savanna

Interior Douglas-Fir-Interior Ponderosa Pine/Gamble

Oak Forest

Quaking Aspen / Engelmann Spruce Forest

Pinyon-Utah Juniper Woodland

Totals

1.6

0.1

77.0

0.8

80.1

Emission Equations

Emissions = (Area burned) x (Fuel Load Available) x (Fuel Consumed (Burn

Efficiency)) x (Emission Factors)

Mass of Emissions =

Area burned (input from AQP datasets)

Fuel Load Available (updated FCCS map)

Fuel Consumed (CONSUME3)

Emission Factors (FEPS plus HAPs)

Bluesky Playground Framework

Assumptions

Collected and reported fire related data is assumed to be accurate and to be the best data

available. BlueSky is assumed to function as intended and to select the proper fuel

characteristics from the USFS FCCS map when latitude and longitude coordinates are

input into the model.

Emissions

Total criteria pollutant, NH3 and GHG from prescribed burns and wildland fires that

occurred within the exterior boundaries of Reservation boundaries in 2015 are displayed

below in Figure 76.

Figure 76 - 2015 Criteria Pollutant, NH3, and GHG Emissions from Prescribed

Burns and Wildland Fires within the Exterior Boundaries of the Southern Ute

Indian Reservation in Tons per Year

2015 Prescribed Burn and Forest Fire Emissions on the Southern Ute

Indian Reservation in Tons per Year

Pollutant

TOTAL

PM10

9.6

48.1

NOx

0.9

NH3

0.78

SO2

0.4

VOC

11.3

CO2e

833.7

8. Agricultural Burning

Description of Activity

Agricultural burning is performed on the Reservation to clear irrigation ditches of

vegetation and to clear pastures of weeds and vegetation prior to crop cultivation.

Data Collection

Emissions from agricultural burning on the Reservation were obtained from the 2014

NEI for La Plata County and Archuleta County. EPA reported two types of agricultural

burning: Agricultural Burning Grasses, and Agricultural Burning Unspecified Crop

Type. EPA did not report emissions for Agricultural Burning Unspecified Crop Type

for Archuleta County. Emissions were not included in this emissions inventory for

Montezuma County due to only 0.2% of the county falling within the Reservation

boundaries.

Emission Calculation Methodology

Emissions obtained from the NEI for La Plata and Archuleta County were scaled down

proportionally to the percentage of land in La Plata and Archuleta counties that fall

within the exterior boundaries of the Reservation.

Assumptions

AQP assumes the methods and calculations used to develop emissions from agricultural

burning are valid and acknowledges that the process used to reduce emissions for the

Reservation could result in a slight under or overestimation of emissions. It is also

assumed that emissions from agricultural burning from the 2014 NEI are realistic

estimations that occurred in 2015.

Emissions

Criteria pollutants, NH3 and HAP emission estimates from agricultural burning that

occurred within the exterior boundaries of the Reservation in 2015 are displayed below

in Figure 77.

Figure 77 – 2015 Criteria Pollutant, NH3, and HAP Emissions from Agricultural

Burning on the Southern Ute Indian Reservation in Tons per Year

Pollutant

2015 Agricultural Burning Emissions for the Southern Ute Indian

Reservation in Tons per Year¹

PM10

NOx

NH3

VOC

Total

SO2

TOTAL

HAP

0.0

2.2

12.6

0.3

0.7

0.0

0.7

¹Emissions for agricultural burning were estimated from data retrieved from the 2014 EPA National

Emission Inventory Database and are assumed to be realistic estimations of agricultural burning emissions

that occurred in 2015.

VI.

Mobile Sources

Description of Sources

Mobile source emissions are generated from on-road vehicles and non-road engines

including lawn equipment, recreational vehicles, agricultural equipment, construction

equipment, etc.

1. On-Road Mobile Sources

AQP estimated emissions from gasoline, diesel, compressed natural gas (CNG), and

ethanol fueled on-road mobile sources, such as motorcycles, passenger cars, passenger

trucks, light commercial trucks, transit buses, school buses, refuse trucks, single unit

land and short-haul trucks, motorhomes, and combination short-haul trucks.

Data Collection

Hourly humidity and temperature data were obtained from the two SUIT Ambient Air

Monitoring stations, Ute 1 and Ute 3. The humidity and temperature data were used to

calculate hourly averages for each month of the year. The hourly average values for each

month were then used as meteorology data inputs into the EPA MOVES2014a

(MOVES) emission modeling software. 37

Vehicle miles traveled (VMT) data (by vehicle type) were obtained from the 2014 NEI

County Database (CDB). Data adjustments were made to the VMTs based on the

percentage of road miles in La Plata and Archuleta County that fall within the exterior

boundaries of the Reservation, as determined from GIS shapefiles obtained from the La

Plata and Archuleta County GIS departments.38,39 The data adjustment resulted in a

reduction of the VMT data to 48.05% and 18.2% for La Plata and Archuleta counties,

respectively. No significant roads on the Reservation are located in Montezuma County,

and therefore AQP assumed VMT for Montezuma County to be negligible. The AQP

determined that 1,427.4 miles of roads are within the Reservation boundaries. Fuel type

data for on-road vehicles was obtained from the 2014 NEI National Database (NDB)

U.S. EPA Moves 2014. (2016). Retrieved from https://www.epa.gov/catc/clean-air-technology-centerproducts#software

La Plata County. (2016). Roads. GIS/Mapping. Retrieved from ftp://ftp.laplata.co.us/shapefiles/

Archuleta County. (2016). Roads - Archuleta County. GIS. Retrieved from

http://www.archuletacounty.org/504/Download-GIS-Data

and no adjustments to the data set were necessary, since fuel type usage was assumed to

be the same across the Reservation.

Emission Calculation Methodology

Data values were input into the MOVES model to calculate mobile source emissions

individually for both La Plata and Archuleta counties. The AQP later combined the two

model output data sets to obtain Reservation emission totals. MOVES calculated

emissions for running exhaust, engine start exhaust, brake wear and tire wear from

mobile sources fueled by gasoline, diesel, CNG and ethanol. Data outputs were

organized by source type, fuel type, and pollutant using the MySQLTM online open

source database.40

Assumptions

AQP assumed data from the 2014 NEI to be the best available data for 2015 and the

emissions estimations from MOVES to be correctly calculated and realistic.

Emissions

Criteria pollutant emissions from on-road mobile sources on the Reservation in 2015 are

displayed below in Figure 78.

Figure 78 – 2015 Criteria Pollutant Emissions from On-Road Mobile Sources on

the Southern Ute Indian Reservation in Tons per Year

2015 On-road Mobile Source Emissions on the Southern Ute Indian Reservation

in Tons per Year

Pollutant

Emissions

250.5

NOx

55.7

VOC

19.1

PM10

8.0

2. Non-Road Mobile Sources

Non-road mobile sources contribute a significant portion of the NOx and CO emissions

from mobile sources. Non-road mobile sources on the Reservation include agricultural

equipment, construction and mining equipment, lawn and garden equipment, and

recreational equipment.

Oracle. (2016). MySQLWorkbench Version 6.3.7. Retrieved from https://www.mysql.com/

Data Collection

Hourly humidity and temperature data were obtained from the two SUIT Ambient Air

Monitoring stations, Ute 1 and Ute 3. The humidity and temperature data were used to

calculate hourly averages for each month of the year. The hourly average values for each

month were then used as data inputs into MOVES emission modeling software.

Fuel type data for non-road sources were obtained from the 2014 NEI NDB and used as

the fuel data inputs in MOVES.

Assumptions

AQP assumed data from the 2014 NEI to be the best available data and the emissions

estimations from MOVES to be correctly calculated and realistic.

Emission Calculation Methodology

AQP performed a single MOVES model run for non-road sources, which concurrently

estimated emissions for both La Plata and Archuleta counties. The MySQL database was

used to organize the model outputs by sector, source classification code and pollutant.

Emissions were calculated on a county level and AQP reduced emissions totals for La

Plata and Archuleta County to 38.9 % and 29.5% respectively, based on the portion of

the counties that are within the exterior boundaries of the Reservation.

Emissions

Criteria pollutant emissions from non-road mobile sources on the Reservation in 2015

are displayed below in Figure 79.

Figure 79 – 2015 Criteria Pollutant Emissions from Non-Road Mobile Sources on

the Southern Ute Indian Reservation in Tons per Year

Pollutant

Emissions

VII.

2015 Mobile Non-Road Emissions on the Southern Ute Indian

Reservation in Tons per Year

NOx

VOC

PM10

1252.8

123.5

177.7

15.2

Biogenic

Biogenic processes of trees, vegetation, soil, and microbial activities generate VOC, NOx,

CO, and HAP emissions. EPA estimates biogenic emissions for triennial inventory years,

with the last estimation performed for calendar year 2014.

Assumptions

The AQP assumed the emission estimations prepared by EPA to be performed correctly and

to be the best available emissions estimates for 2015.

Emission Calculation Methodology

Biogenic emissions estimated for La Plata and Archuleta County were prepared by EPA

using the EPA’s Biogenic Emission Inventory System and Biogenic Emissions Landuse

Database.41 AQP obtained the 2014 emission estimates for La Plata and Archuleta counties

from the 2014 NEI. Emissions estimates for Montezuma County were not included in this

emissions inventory due to only 0.2% of the county falling within the Reservation

boundaries.

County wide emissions were reduced for La Plata and Archuleta County to 38.9% and

29.5% respectively, based on the area of each county that is located within the exterior

boundaries of the Reservation.

Emissions

Criteria pollutant and HAP emissions from biogenic sources on the Reservation in 2015 are

displayed below in Figure 80.

Figure 80 – 2015 Criteria Pollutant and HAP Emissions from Biogenic Sources on

the Southern Ute Indian Reservation in Tons per Year¹

2015 Biogenic Source Emissions on the Southern Ute Indian Reservation

in Tons per Year

Pollutant

NOx

VOC

HAP

Emissions

2,018.4

146.1

11,932.2

1,532.3

¹Emissions for biogenic sources were estimated from data retrieved from the 2014 EPA National Emission

Inventory data and are assumed to be realistic estimations of biogenic source emissions for 2015.

VIII.

Summary

1. Emissions Sources

Reservation emissions presented in this inventory are distributed between point, non-point,

mobile and biogenic sources.

U.S. Environmental Protection Agency. (2009). Biogenic Emission Inventory System. Retrieved from

https://www.epa.gov/air-emissions-modeling/biogenic-emission-inventory-system-beis

A. Point Sources

There are four categories of point sources including:

1) Title V permitte

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