773 San Marin Drive, Suite 2115, Novato, CA 94998 415.899.0700 ENVIRON International Corporation

DEVELOPMENT OF BASELINE 2006 EMI SSIONS FROM OIL AND GAS ACTIVITY IN THE DENVER-JULESBURG BASIN

Prepared for Colorado Department of Public Health and Environment Air Pollut ion Control Division

Prepared by Amnon Bar-Ilan John Grant Ron Friesen Alison K. Pollack ENVIRON International Corporation

773 San Marin Drive, Suite 2115 Novato, CA 94998

Doug Henderer

Daniel Pring Buys & Associates 300 E. Mineral Ave., Suite 10 Littleton, CO 80122

Kathleen Sgamma Independent Petroleum Associati on of Mountain States (IPAMS) 410 17th Street, Suite 1920 Denver, CO 80202

April 30, 2008April 2008

G:\IPAMS\Technical_Reports\D-J_Basin\CDPHE_S ubmission\2006_Baseline_Emiss_D-J_Basin_043008.docApril 2008

G:\IPAMS\Technical_Reports\D-J_Basin\CDPHE_Subm ission\2006_Baseline_Emiss_D-J_Basin_043008.doc i TABLE OF CONTENTS

Page

Introduction .................................................................................................................. ................1 Temporal and Geographic Scope.................................................................................................. ...1 Well Count and Production Data ................................................................................................. ....3 Development of Spatial Allocation Surrogates................................................................................5 Sources Subject to APEN Reporting and Condensate Tanks Subject To Regulation 7.................................................................................................. ......7 APEN Exempt Sources............................................................................................................ ........8 APEN Exempt Emission Calculation Methodologies .....................................................................9 Well Blowdowns................................................................................................................. .............9 Well Completions and Recompletions...........................................................................................10 Drill Rigs – Drilling Operations ............................................................................................... .....11 Workover Rigs.................................................................................................................. .............13 APEN Exempt Engines............................................................................................................ ......15 Fugitive Leaks ................................................................................................................ ................16 Heater Treater, Separators, a nd Glycol Dehydrator Burners.........................................................17 Pneumatic Control Devices...................................................................................................... ......18 Gas Actuated Pumps............................................................................................................. .........19 Produced Water Tanks........................................................................................................... ........20 APEN Exempt Atmospheric Storage Tanks..................................................................................21 Well Site Land Farming......................................................................................................... ........22 Truck Loading ................................................................................................................. ...............23 Flaring ..................................................................................................................... ...........24 Summary Results ................................................................................................................ ...........25

TABLES

Table 1. Comparison of active well count in Denver-Julesburg Basin........................................4 Table 2. 2006 well count and oil, gas and water production by county for the D-J Basin ................................................................................................4 Table 3. 2006 spud counts by county for the D-J Basin ..............................................................5 Table 4. 2006 emissions of all criteria pollutants by county for the D-J Basin. .........................................................................................................2 8 Table 5. 2006 NOx emissions by county and by source category for the D-J Basin ...........................................................................................29 Table 6. 2006 VOC emissions by county and by source category for the D-J Basin ...........................................................................................30April 2008

G:\IPAMS\Technical_Reports\D-J_Basin\CDPHE_Subm ission\2006_Baseline_Emiss_D-J_Basin_043008.doc ii FIGURES

Figure 1. D-J Basin boundaries over laid with the 2006 well locations.........................................2 Figure 2. D-J Basin gas production spatia l surrogate values for the 4km domain........................6 Figure 3. D-J Basin oil production spatial surrogate values for the 4km domain.........................6 Figure 4. D-J Basin drilling locations spat ial surrogate values for the 4km domain ....................7 Figure 5. 2006 NOx emissions by source category and by county in the D-J Basin...........................................................................................26 Figure 6. 2006 VOC emissions by source category and by county in the D-J Basin...........................................................................................26 Figure 7. D-J Basin NOx emissions proportional contributions by source category .......................................................................................................27 Figure 8. D-J Basin VOC emissions proportional contributions by source category .......................................................................................................27April 2008

G:\IPAMS\Technical_Reports\D-J_Basin\CDPHE_Subm ission\2006_Baseline_Emiss_D-J_Basin_043008.doc 1 INTRODUCTION

The Independent Petroleum Association of Mountain States (IPAMS) is sponsoring the development of a Phase III regional oil and gas emission inventory for the inter-Mountain West jointly with the Western Regional Air Partners hip (WRAP), to build on the WRAP Phase I and Phase II inventory projects. This effort is focused on creating a comprehensive criteria pollutant emissions inventory for all activities associated with oil and gas field operations in the basins throughout the study region for year 2006 as well as future projecti on years; that includes all point and area sources related to the oil and gas industry.

The initial region of interest for the emissi on inventory is the Denve r-Julesburg (D-J) Basin, which includes the 8-hour ozone nonattainment area under the jurisdiction of the Air Pollution Control Division (APCD) of the Colorado Depa rtment of Public He alth and Environment (CDPHE). The 2006 baseline invent ory consists of two primary ca tegories: sources subject to Air Pollution Emission Notice (APEN) reporting requirements, and sources exempt from APEN reporting, which are collectively termed “unpermitted” sources in this document. This document describes the methodologies by which the 2006 inve ntory was constructed. This methodology is specific to the D-J Basin and will have additions and changes for other basins in the Phase III project. For each source category, a basic de scription is given of the methodology used to estimate emissions from a single source or fr om all sources belonging to companies that participated in the survey effort (“participa ting companies”), and a description of how those emissions were scaled up to the county and basin-wide level.

In general, the inventory was developed usi ng a combination of well count and production activity from a commercially available databa se of oil and gas data maintained by IHS Corporation (“the IHS database”), the State of Colorado’s database of permitted sources including APENs sources and Regulation 7 reports, and detailed survey re sponses of oil and gas activity from several major participating companies that operate in the D-J Basin. Some additional data sources were also used, includin g American Petroleum In stitute (API) technical literature, the US Environmental Protection Agen cy’s (EPA) AP-42 emissions factor technical guidance, the US EPA’s NONROAD emissions model, and the US EPA’s Natural Gas Star program technical guidance.

Temporal and Geographic Scope

This inventory considers a base year of 2006 for purposes of es timating emissions, consistent with the year for which episodic air quality modeling will be conducted for the upcoming Denver metropolitan area 8-hour ozone SIP modeling effort . All data requested from participating companies were for these companies’ activities in the calendar year 2006. Similarly, all well count and production data for the basin obtained from the IHS database were for the calendar year 2006. Emissions from all source categorie s are assumed to be uniformly distributed throughout the year except for heaters and pne umatic pumps, which are assigned seasonality fractions as they are typically used primarily in winter.

The geographic scope of this inventory is the D-J Basin, whose boundaries as defined by the US Geological Survey (USGS) were used. The USGS boundaries for the D-J Basin were intersected with the State of Colorado boundaries so that on ly the portion of the D-J Basin within ColoradoApril 2008

G:\IPAMS\Technical_Reports\D-J_Basin\CDPHE_Subm ission\2006_Baseline_Emiss_D-J_Basin_043008.doc 2 was considered for this inventory. The followi ng counties were wholly contained within the boundaries of the D-J Basi n in this inventory:

• Adams

• Arapahoe

• Boulder

• Broomfield

• Crowley

• Denver

• Douglas

• Elbert • El Paso

• Fremont

• Jefferson

• Kit Carson

• Larimer

• Lincoln

• Logan

• Morgan • Phillips

• Pueblo

• Sedgwick

• Teller

• Washington

• Weld

• Yuma

Figure 1 shows the boundaries of the D-J Basin, w ith the 2006 well locations extracted from the IHS database overlaid.

Figure 1. D-J Basin boundaries overlaid and 2006 oil and gas well locations

.April 2008

G:\IPAMS\Technical_Reports\D-J_Basin\CDPHE_Subm ission\2006_Baseline_Emiss_D-J_Basin_043008.doc 3 Well Count and Production Data

Oil and gas related activity data across the entire D-J Basin were obtained from the IHS Enerdeq database queried via online interf ace. The IHS database uses data from the Colorado Oil and Gas Conservation Commission (COGCC) as a source of information for Colorado oil and gas activity. Two types of data were queried from the Enerdeq database: production data and well data. Production data includes information releva nt to producing wells in the basin while well data includes information relevant to drilling ac tivity (“spuds”) and completions in the basin.

Production data were obtained for the counties that make up the D-J Basin in the form of PowerTools input files. PowerTools is an IHS application which, given PowerTools inputs queried from an IHS database, analyzes, inte grates, and summarizes production data in an ACCESS database. The D-J Basin PowerTools i nput files were loaded into the PowerTools application. From ACCESS database created by PowerTools, extractions of the following data relevant to the emissions inve ntory development were made:

1. 2006 active wells, i.e. wells that report ed any oil or gas production in 2006. 2. 2006 oil, gas, and water production by well.

The production data are available by API number. The API number in the IHS database consists of 14 digits as follows:

• Digits 1 to 2: state identifier

• Digits 3 to 5: county identifier

• Digits 6 to 10: borehole identifier

• Digits 11 to 12: sidetracks

• Digits 13 to 14: event se quence code (recompletions)

Based on the expectation that the first 10 di gits, which include geographic and borehole identifiers, would predict unique sets of well head equipment, the unique wells were identified by the first 10 digits of the API number.

In an attempt to validate the IHS well count and production data, comparisons were made to summary data for 2006 provided by COGCC. It wa s found that while IHS Enerdeq oil, gas, and water production agreed to w ithin 1% with COGCC provided summary data, active well counts differed considerably between IHS data and C OGCC summary data. Upon further analysis of the COGCC database, it was discovered that the di fference in well counts was due to the way in which unique wells were identifie d. If unique wells are simply id entified by unique 14-digit API numbers, a much higher well count is estimated compared to if uni que wells are identified by the first 10 digits of the API number. Furtherm ore, discussions with COGCC indicated that production reports were received for some wells although the well di d not produce any oil or gas. However, since the production repor t was received, COGCC classified this as an active well. If the first 10 digits of the API number only are used, and only we lls with non-zero production of oil or gas are counted, well counts are consistent between the COGCC and IHS databases. Table 1 shows basin-wide well count estimates fr om the COGCC and IHS Enerdeq database.April 2008

G:\IPAMS\Technical_Reports\D-J_Basin\CDPHE_Subm ission\2006_Baseline_Emiss_D-J_Basin_043008.doc 4 Table 1 . Comparison of active well count in Denver-Julesburg Basin. Database Identifier Well Count COGCC API # (all digits) 21,847 COGCC API # (first 10 digits and only active wells) 16,783

IHS Enerdeq API # (first 10 digits and only active wells) 16,774

Well data were also obtained from the IHS Ener deq database for the counties that make up the Denver Julesburg basin in the form of “297” well data. The “297” well data contain information regarding spuds and completions. The “297”well data were proce ssed with a PERL script to arrive at a database of by-API-number, spud a nd completion dates with latitude and longitude information. Drilling events in 2006 were identified by indication that the spud occurred within 2006. If the well API number indicated the well was a recompletion, it was not counted as a drilling event, though if the API number indicated the well was a sidetrack, it was counted as a drilling event.

The well counts and oil, gas and water productio n by county for the basin are presented in Table 2, and the spuds by county are presented in Table 3.

Table 2 . 2006 well count and oil, gas and water production by county for the D-J Basin

.
County Well Count Oil Production [bbl] Gas Production [mcf] Water Production [bbl] Adams 889 406,823 6,738,398 628,171 Arapahoe 103 56,018 376,623 179,392 Boulder 232 132,523 2,373,186 62,787 Broomfield 58 31,798 635,433 14,664 Crowley 0 0 0 0 Denver 34 14,674 242,598 1,189 Elbert 60 38,296 196,974 155,302 El Paso 0 0 0 0 Fremont 37 50,074 0 0 Jefferson 0 0 0 0 Kit Carson 12 21,227 344,013 201,133 Larimer 135 116,755 212,406 3,854,032 Lincoln 12 78,112 27,203 729,088 Logan 112 207,829 260,466 6,081,895 Morgan 66 92,186 290,210 2,821,974 Phillips 19 0 555,029 127,347 Pueblo 0 0 0 0 Sedgwick 3 1,295 50,202 48,177
Teller 0 0 0 0 Washington 457 660,357 2,220,766 21,455,978 Weld 11,861 12,334,121 182,996,149 7,022,304 Yuma 2,684 0 37,111,123 3,375,324 TOTAL 16,774 14,242,088 234,630,779 46,758,757April 2008

G:\IPAMS\Technical_Reports\D-J_Basin\CDPHE_Subm ission\2006_Baseline_Emiss_D-J_Basin_043008.doc 5 Table 3. 2006 spud counts by county for the D-J Basin.

County Total Number of Spuds in 2006

Adams 7 Arapahoe 3 Boulder 9 Crowley 0
Denver 7 Elbert 1 El Paso 0 Fremont 2 Jefferson 0 Kit Carson 2
Larimer 0 Lincoln 1 Logan 9 Morgan 1 Phillips 3 Pueblo 0 Sedgwick 0
Teller 0 Washington 23 Weld 877 Yuma 555 TOTAL 1500

Development of Spatial Allocation Surrogates

Updated spatial allocatio n surrogates for oil and gas emissi ons were developed using the 2006 IHS data. Surrogates were developed for the following Denver CAMx modeling domain:

04 km Origin (-940, -292) NX = 119, NY = 119

Latitude and longitude coordinates for oil and ga s wells and drilling events were obtained from the IHS database. All data were obtained only for the portion of the D-J basin within Colorado. The locations of all wells in the D-J basin ar e shown in Figure 1. The oil and gas production surrogates were based on production data at know n well locations, while the drilling surrogate was based solely on the number a nd location of wells drilled.

The creation of the surrogates took place in severa l steps, and relied on the use of ArcView GIS software.April 2008

G:\IPAMS\Technical_Reports\D-J_Basin\CDPHE_Subm ission\2006_Baseline_Emiss_D-J_Basin_043008.doc 6 1. All wells and drill rigs were labeled w ith the appropriate grid cell IJ values. 2. For each individual well, the oil, gas and water production values were divided by the total oil, gas and water production values co rresponding to the county in which the well was located. This division resulted in dete rmination of the fracti on of a county’s total production taking place at each well. In the ca se of the drilling su rrogate, the number of drilling events, rather than the production values, was used. 3. For each unique grid cell/county combination wi th wells, each well’s production fractions were summed to create the surrogate value.

Figures 2-4 depict th e 4km domain spatial surrogate values.

Figure 2. D-J Basin gas production spatial surrogate values for the 4km domain.

Figure 3. D-J Basin oil production spatial surrogate values for the 4km domain.April 2008

G:\IPAMS\Technical_Reports\D-J_Basin\CDPHE_Subm ission\2006_Baseline_Emiss_D-J_Basin_043008.doc 7 Figure 4. D-J Basin drilling locations spatial surrogate values for the 4km domain.

Sources Subject to APEN Reporting and Condensate Tanks Subject to Regulation 7

On October 31, 2007 a request was made to the APCD for the 2006 Colorado APEN database for all oil and gas related emission sources c overed by the following SCC and SIC codes:

• All of the SCCs 202002*, 310*, 404003* (where * i ndicates all sub-SCCs for the SCC)

• And only those with the following SICs: 13*, 492*, 4612.

APEN data for the D-J basin were extracted a nd sorted by operator. Company specific APEN source data were forwarded to pa rticipating operators for a comp leteness review that included the following three issues:

1) Source Categories that were mi ssing from the APEN database, 2) Specific sources missing from the database, and 3) Sources within the database known to be no longer operating.

Following the completeness review and the additi on or deletion of sources as appropriate, emission rates were reviewed. Emission rates we re updated to reflect 20 06 actual emissions in cases where supporting data were available. Actual emission updates provided by operators followed the APCD calculation methodologies from existing permits or required Operation and Maintenance Plans. The APCD methodologies are used to update Annual Emission Calculations (Minor Sources) and 12-Month Rolling Emission Totals (Synthetic Minor and Major Sources). Documentation of these changes, and a QA/QC review of updated emissions for APEN sources accompany this document.

A separate request was made to APCD for a copy of the 2006 Regulation 7 atmospheric storage tank reports for year 2006. With in the Ozone Control Area, data from the Regulation 7 reports was utilized in place of the APEN data to re present stock tank emissions as the Regulation 7 reports best reflected actual emissions. The Regulation 7 reports for c ondensate tanks were inApril 2008

G:\IPAMS\Technical_Reports\D-J_Basin\CDPHE_Subm ission\2006_Baseline_Emiss_D-J_Basin_043008.doc 8 the form of monthly reports of condensate th roughput for each tank, and emissions for each tank, for all companies operating condensate tanks subject to Regulation 7 in th e ozone non-attainment area. A macro was written in EXCEL to pro cess the reports in such a way that monthly condensate throughput (bbl) and emissions (lb- VOC) could be extracted and summed. Confirmation was obtained that CDPHE’s a nnual Regulation 7 condensate tank emissions summary for 2006 was in reasonable agreement with the extracted emissions from the monthly Regulation 7 reports.

GIS analysis was used to intersect the boundary of the ozone non-attainment area with the latitude/longitude coordinates of all APENs sources. Those sour ces falling within the ozone non-attainment area were filtered to remove a ny sources that were condensate tanks, based on SCC and SCC description. For purposes of summing all permitted oil and gas sources’ emissions in the D-J Basin, emissions from th e remaining APENs sources (excluding condensate tanks in the ozone non-attainment area) were added to the summary emissions from all Regulation 7 condensate tank reports.

APEN Exempt Sources

Survey forms consisting of 11 Excel spreadsheets (attached) were forwar ded to participating operators in the D-J basin. Each spreadsheet contained a request fo r specific data related to one of the following APEN exempt source categories:

• Well blowdowns

• Well completions

• Drilling rigs

• Exempt engines

• Fugitive emissions

• Heaters

• Gas composition analysis for the basin

• Pneumatic devices

• Pneumatic pumps

• Water tanks

• Workover rigs

The companies participating in the survey pro cess for the D-J Basin represented 50% of well ownership in the basin, 63% of gas production in the basin, and 58% of oil production in the basin. This represented a sufficiently large percenta ge of oil and gas activity in the basin that it was felt that the responses obtained from the part icipating companies would be representative of all oil and gas operations in the basin.

In addition to the source categories listed above , emissions from three additional APEN exempt source categories were estimated based on additi onal information requests from the participating companies:

• APEN exempt atmospheric storage tanks

• Truck loading activities

• Flaring from condensate tanksApril 2008

G:\IPAMS\Technical_Reports\D-J_Basin\CDPHE_Subm ission\2006_Baseline_Emiss_D-J_Basin_043008.doc 9 Detailed inventory methodologies for each of th e source categories follow. Extrapolation of these data was necessary to account for emissions fr om all oil and gas activ ity in the basin. The extrapolation methodology to obtain county-leve l and basin-wide emissions for each source category is described below, but is largely base d on scaling by the propor tional representation of the respondents of basin-wide well count or oil or gas production, as appropriate.

For emissions from those source categories that re lied on estimates of volume of gas vented or leaked, such as well blowdowns, completions, and fugitive emissions, gas composition analyses were requested from all participating companies. These composition analyses were averaged to derive a single basin-wide produced gas composition analysis. The average composition analysis was used to determine the average VOC volume and mass fractions of the vented gas basin-wide.

It should be noted that the emission estimates cal culated for APEN exempt sources rely on data that is not as rigorously documented as permitted sources. Much of the data provided for the APEN exempt sources is based upon estimates and extrapolation fr om the survey responses. However the level of detail of the surveys and th e extent of participati on in the survey effort allow for emissions estimates of unpermitted sour ces which are an improvement on the previous WRAP Phase I and Phase II emissions inventory efforts for the D-J Basin.

APEN Exempt Emission Calculation Methodologies

Well Blowdowns

Methodology

Emissions from well blowdowns were calculate d using the estimated volume of gas vented during blowdown events, the frequency of the bl owdowns, and the VOC content of the vented gas as documented by representative compositional analyses.

The calculations applied the ideal gas law and gas characteristics defined from a laboratory analysis to estimate emissions according to Equations 1 and 2:

Equation (1) TOTAL vented vented V f V

, = ×

where: V

vented is the volume of vented gas per blowdown [mscf/event] f

is the frequency of blowdowns [events/year] V

vented,TOTAL is the total volume of vented gas from the participating companies [mscf/year] Equation (2) VOC VOC TOTAL vented blowdown Y R MW 1000 V E × × × × =

,

where: E

blowdown is the total VOC emissions from bl owdowns conducted by the participating companies [lb-VOC/yr] MW VOC is the molecular weight of the VOC [lb/lb-mol] R is the universal gas constant [lb-mol/379scf] Y

is the volume fraction of VOC in the vented gasApril 2008

G:\IPAMS\Technical_Reports\D-J_Basin\CDPHE_Subm ission\2006_Baseline_Emiss_D-J_Basin_043008.doc 10 The conversion from volume of gas vented to ma ss of VOC produced was evaluated at standard temperature and pressure.

Extrapolation to Basin-Wide Emissions

The total VOC emissions from all blowdowns repor ted by participating companies was scaled by the proportional production ownership of the par ticipating companies acc ording to Equation 3:

Equation (3) P P E E TOTAL blowdown TOTAL blowdown × =

,

where: E

blowdown,TOTAL are the total emissions basin- wide from blowdowns [tons/year] E

blowdown are the blowdown emissions from th e participating companies [tons/year] P TOTAL is the total gas production in the basin in 2006 [mscf] P is the total gas production in the basin in 2006 by the participating companies [mscf]

County-level emissions were estimated by allocat ing the total basin-wide blowdown emissions into each county according to the fraction of total 2006 gas production occurring in that county.

Well Completions and Recompletions

Methodology

Emissions from well completions were estimated on the basis of the volume of gas vented during completion and the average VOC content of th at gas, obtained from the gas composition analyses. The data received from the particip ating companies indicated that completion flaring does not occur in the D-J Basin, however any Be st Management Practic es (BMP) for initial completions or re-completions were incorporated into the data provided.

The calculation methodology for completion emissions is identical to the method for blowdown emissions, and follows Equations 4 and 5:

Equation (4) TOTAL vented vented V f V

, = ×

where: V

vented is the volume of vented ga s per initial completion or re-completion [mscf/event] f

is the frequency of completions [events/year] V

vented,TOTAL is the total volume of vented gas from completions for participating companies [mscf/year]

Equation (5) VOC VOC TOTAL vented completion Y R MW 1000 V E × × × × =

,April 2008

G:\IPAMS\Technical_Reports\D-J_Basin\CDPHE_Subm ission\2006_Baseline_Emiss_D-J_Basin_043008.doc 11 where: E

completions is the total VOC emissions from comp letions conducted by all participating companies [lb-VOC/yr] MW VOC is the molecular weight of the VOC [lb/lb-mol] R is the universal gas constant [lb-mol/379scf] Y

is the volume fraction of VOC in the vented gas

The conversion from volume of gas vented to ma ss of VOC produced was evaluated at standard temperature and pressure.

Extrapolation to Basin-Wide Emissions

The total VOC emissions from all completions reported by participating companies was scaled by the total number of completi ons in the basin to the number of completions conducted by the participating companies according to Equation 6:

Equation (6) C C E E TOTAL completion TOTAL completion × =

,

where: E

completion,TOTAL are the total emissions basin-wi de from completions [tons/year] E

completion are the completion emissions from the participating companies [tons/year] C TOTAL is the total number of completions in the basin in 2006 C

is the total number of completions in th e basin in 2006 by the participating companies.

County-level emissions were estimated by allocat ing the total basin-wide completion emissions into each county according to the fraction of tota l 2006 completions that occurred in each county.

Drill Rigs – Drilling Operations

Methodology

The participating companies were surveyed for information on drilling rigs operating in 2006 in the D-J Basin. Because many drill rigs are operate d by contractors to the oil and gas producers, data were not always available to the level of detail requested in the surveys. Some of the companies surveyed were able to provide exac t configurations for all rigs used in their operations, while others were able to provide information on only one or several representative rigs. In all cases, complete information for every parameter needed to estimate drilling rig emissions was not available, and in these cases e ngineering analysis was used to fill in missing information. Because the nature of the survey responses for drilling rigs varied so much by company, the methodology used was to first estimat e each company’s total drilling rig emissions given the nature of the data available for that company, and then to sum the emissions and scale up to the basin level.April 2008

G:\IPAMS\Technical_Reports\D-J_Basin\CDPHE_Subm ission\2006_Baseline_Emiss_D-J_Basin_043008.doc 12 In general, the emissions for an individual rig engine were estimated according to Equation 7:

Equation (7) 185

, 907 , drilling i engine drilling t LF HP EF E × × ×

=

where: E

drilling,engine is the emissions from one engine on the drilling rig for drilling one well [ton/engine/spud] EF i is the emissions factor for the engine for pollutant i [g/hp-hr] HP is the horsepower of the engine [hp] LF is the load factor of the engine

t drilling is the actual on-time of the engine for a ty pical drilling event in the basin [hr/spud]

A single drilling rig may contain from 3 – 7 or mo re engines, including draw works, mud pump, and generator engines. The total emissions from drilling one well are thus the sum of emissions from each engine, according to Equation 8:

Equation (8) 

## ∑

=

i i engine drilling drilling E E

, ,

where: E

drilling is the total emissions from drilling one well [tons/spud] E

drilling,engine,i is the total emissions from engine i from drilling one well [tons/engine/spud]

It should be noted that SO 2 emissions were estimated using th e brake-specific fuel consumption (BSFC) of the engine, as obtained from the US EPA’s NONROAD model for a similarly sized drill/bore rig engine, and the 2006 su lfur content of the off-road diesel fuel as obtained from communication with CDPHE. The off-road dies el fuel sulfur content was assumed to be 500ppm. The EPA NONROAD mode l guidance was used to determine the fraction of fuel sulfur that would go to forming PM emissions – for drilling rig engine s this was only 2.2% of sulfur content. It was assumed that the remaining sulfur in the fuel would be emitted as SO 2
.
Emissions factors were either provided by the su rvey respondent or were obtained from the US EPA’s NONROAD model. For emissions factor s taken from the NONROAD model, in cases where it was not possible to ascertain the engi ne’s technology type, unc ontrolled, undeteriorated drill/bore rig engines of the same size class we re assumed. When a producer supplied emission factors for some, but not all pollutants, the tec hnology type of the engine was estimated based on the supplied emission factors and emissions f actors from the NONROAD model were taken for the estimated technology type for drill/bore rig engines of the same size class. This allowed the calculations to incorporate information about sp ecific rig engines when it was available, and defaulted to the NONROAD model wh ere this information was not av ailable. Load factors were similarly estimated by using respondent inform ation where such detailed information was available, or by using the NONR OAD model or the WRAP Phase II analysis where they were not available.

The resulting rig configurations included engines of several Tier models, several different counts of number of engines per rig, and differing lo ad factors for the diffe rent engines on a rig.April 2008

G:\IPAMS\Technical_Reports\D-J_Basin\CDPHE_Subm ission\2006_Baseline_Emiss_D-J_Basin_043008.doc 13 Extrapolation to Basin-Wide Emissions

Due to the variability in the type of informati on provided by the participating companies, it was decided to sum the drilling emissions for each company separately using the data and assumptions for that company, and then to sum all participating compan ies’ drilling emissions and scale this to the basin-wide drilling emissi ons. Participating companies’ drilling emissions were estimated using the emissions from drilli ng one well using that company’s representative rig or rigs, and then multiplying by the number of spuds drilled by that company in 2006. If more than one representative rig was provided, al l spuds drilled by that company were divided evenly among the representative rigs. In the case of one respondent, all of that company’s rigs were detailed including the total hours of usage during the year for all rigs. This was used to sum the company’s drilling emissions, rather than the number of spuds.

The basin-wide drilling emissions were derive d by scaling up the combined participating companies’ drilling emissions according to Equation 9:

Equation (9) S S E E TOTAL drilling TOTAL drilling × =

,

where: E

drilling,TOTAL is the total emissions in the ba sin from drilling activity [tons/yr] E

drilling is the total emissions in the basin from drilling activity conducted by the participating companies (summed as described above) [tons/yr] S TOTAL is the total number of spuds th at occurred in the basin in 2006 S

is the total number of spuds in the basin in 2006 drilled by the pa rticipating companies

County-level emissions were estimated by allocati ng the total basin-wide drilling rig emissions into each county according to the fraction of total 2006 spuds that occurred in each county.

Workover Rigs

Methodology:

Participating companies’ survey responses were us ed to derive a represen tative configuration of a workover rig, and the estimated duration of use of the workover rig for a typical well workover in the basin. Workover rigs are typically sma ller in total horsepower than drilling rigs and usually consist of only one engine. For the D-J Basin, the survey responses indicated that the representative workover rig consis ted of one Detroit Diesel Seri es 60 engine of approximately 475 hp. It was assumed that this engine was a baseline, uncontrolled, undeteriorated diesel engine for purposes of estimating its emissions factors. This was considered a reasonably conservative assumption, since some workover ri g engines may be newer engines (Tier 1 or better), but some may not be recently maintained or rebuilt. Emissions factors were taken from the EPA NONROAD model for baseli ne, undeteriorated drill/bore ri g engines of the same size class. The average load factor for a workover rig engine was obtained from the WRAP Phase II survey effort, since the participating companies we re not able to provide detailed information on the load factors.April 2008

G:\IPAMS\Technical_Reports\D-J_Basin\CDPHE_Subm ission\2006_Baseline_Emiss_D-J_Basin_043008.doc 14 The basic methodology for estimating the emissions from a workover rig follows Equation 10:

Equation (10) 185

, 907 , workover i engine workover t LF HP EF E × × ×

=

where: E

workover,engine is the emissions from one workover [ton/workover] EF i is the emissions factor of the workover rig engine of pollutant i [g/hp-hr] HP is the horsepower of th e workover rig engine [hp] LF is the average load factor of the workover rig engine

t workover is the average du ration of a workover event [hr/workover]

It should be noted that SO 2 emissions were estimated using th e BSFC of the engine, as obtained from the US EPA’s NONROAD mo del for a similarly sized dril l/bore rig engine, and the 2006 sulfur content of the off-road diesel fuel as obtained from communication with CDPHE. The off-road diesel fuel sulfur content was assumed to be 500ppm. The EPA NONROAD model guidance was used to determine the fraction of fuel sulfur that would go to forming PM emissions – for workover rig engines this was 2.2% of sulfur content. It was assumed that the remaining sulfur in the fuel would be emitted as SO 2
.

Extrapolation to Basin-Wide Emissions

The total workover rig emissions for the participating companies were derived by multiplying the per-workover emissions above for each pollutant by the total number of workovers conducted by the participating companies. This was then scaled up by the ratio of total well count in the basin to wells owned by the part icipating companies, following Equation 11:

Equation (11) W W E E TOTAL workover TOTAL workover × =

,

where: E

workover,TOTAL are the total emissions basin- wide from workovers [tons/year] E

workover are the total workover rig emissions from the particip ating companies [tons/year] W

TOTAL is the total number of wells in the basin W

is the number of wells owne d by the participating companies

County-level emissions were estimated by allocati ng the total basin-wide workover rig emissions into each county according to the fraction of total 2006 well counts that are located in each county.April 2008

G:\IPAMS\Technical_Reports\D-J_Basin\CDPHE_Subm ission\2006_Baseline_Emiss_D-J_Basin_043008.doc 15 APEN Exempt Engines

Methodology:

The participating companies provided a complete inventory of all APEN exempt engines in use in their operations. Emission calculations for APEN exempt engines follow a similar methodology as for drilling rig or workover rig engines.

The basic methodology for estimating emissions from an exempt engine is shown in Equation 12:

Equation (12) 185

, 907 annual i engine t LF HP EF E × × ×

=

where: E

engine are emissions from an exem pt engine [ton/year/engine] EF i is the emissions factor of pollutant i [g/hp-hr] HP is the horsepower of the engine [hp] LF is the load factor of the engine

t annual is the annual number of hours the engine is used [hr/yr]

Note that, similar to drilling rig and workover rig engines, SO 2 emissions are estimated using the BSFC of the engine, and the assumed sulfur c ontent of the fuel, assuming that all sulfur emissions are in the form of SO 2 . For natural gas-fired exem pt engines, gas composition analyses indicate no sulfur present in the natural gas; therefore SO 2 emissions are negligible from these engines.

Extrapolation to Basin-Wide Emissions

Emissions from all exempt engines from the pa rticipating companies were summed. The total emissions from all participating companies were scaled by the ratio of total well count in the basin to wells owned by the participat ing companies according to Equation 13:

Equation (13) W W E E TOTAL engine TOTAL engine =

,

where: E

engine,TOTAL is the total emissions from exem pt engines in th e basin [ton/yr] E

engine is the total emissions from exempt e ngines owned by the participating companies [ton/yr] W

TOTAL is the total number of wells in the basin W

is the number of wells owne d by the participating companies

County-level emissions were estimated by allo cating the total basin-wide exempt engine emissions into each county according to the fracti on of total 2006 well counts that are located in each county.April 2008

G:\IPAMS\Technical_Reports\D-J_Basin\CDPHE_Subm ission\2006_Baseline_Emiss_D-J_Basin_043008.doc 16 Fugitive Leaks

Methodology

Fugitive emissions from well sites were estimated using AP-42 emissions factors and equipment counts provided in the survey re sponses. The participating comp anies provided total equipment counts for all of their operations in the basin by type of equipment and by the type of service to which the equipment applies – gas, li ght liquid, heavy liquid, or water.

Fugitive VOC emissions for an individual compon ent were estimated similar to blowdown or completion emissions, according to Equations 14 and 15:

Equation (14) TOTAL vented vented V N V

, = ×

where: V

vented is the volume of fugitive gas leaked pe r component, for different service types [mscf/component] N

is the number of component s of each service type V

vented,TOTAL is the total volume of vented gas fr om all components for all participating companies [mscf/year]

Equation (15) VOC VOC TOTAL vented fugitive Y R MW 1000 V E × × × × =

,

where: E

fugitive is the fugitive VOC emissions for all participating companies [lb-VOC/yr] MW VOC is the molecular weight of the VOC [lb/lb-mol] R is the universal gas constant [lb-mol/379scf] Y

is the volume fraction of VOC in the vented gas

The conversion from volume of gas vented to ma ss of VOC produced was evaluated at standard temperature and pressure.

Extrapolation to Basin-Wide Emissions

Basin-wide fugitive emissions are estimated by scaling the fugitive emissions from all participating companies by the ratio of the total nu mber of wells in the basin to the number of wells owned by the participating comp anies, according to Equation 16:

Equation (16) W W E E TOTAL fugitive TOTAL fugitive =

,

where: E

fugitive,TOTAL is the total emissions from fugitive leaks in the basin [ton/yr] E

fugitive is the fugitive emissions for all participating companies [lb-VOC/yr] W

TOTAL is the total number of wells in the basin W

is the number of wells owne d by the participating companiesApril 2008

G:\IPAMS\Technical_Reports\D-J_Basin\CDPHE_Subm ission\2006_Baseline_Emiss_D-J_Basin_043008.doc 17 County-level emissions were estimated by allocati ng the total basin-wide fugitive emissions into each county according to the fraction of total 2006 well counts that are loca ted in each county.

Heater Treater, Separators, and Glycol Dehydrator Burners

Methodology

Heater (heater-treater, separator, tank heaters and glycol dehydr ator burners) emissions were calculated on the basis of the emissions factor of the heater, and the annual flow rate of gas to the heater. The annual gas flow rate was calculated from the BTU rati ng of the heater and the local BTU content of the gas. The AP-42 emission fact ors for an uncontrolled small boiler were used for specific pollutants.

The basic methodology for estimating emissions fo r a single heater is shown in Equation 17:

Equation (17) hc t HV HV Q EF E annual
rated local heater heater heater × × × × =

where: E

heater is the emissions from a given heater EF heater is the emission factor for a heater for a given pollutant [lb/MMBTU] Q heater is the heater MMBTU/hr rating [MMBTU rated /hr] HV local is the local natural gas heating value [MMBTU local /scf] HV rated is the heating value for natural gas used to derive heater MMBTU rating, Q heater [MMBTU/scf]

t annual is the annual hours of operation [hr/yr] hc is a heater cycling fraction to account for the fraction of operat ing hours that the heater is firing (if available)

Emissions for all heaters in the basin operated by the participating companies were estimated according to Equation 18:

Equation (18) heater heater companies heater N E E × =

,

where: E

heater,companies is the total emissions from all heat ers operated by participating companies [lb/yr] E

heater is the emissions from a single heater [lb/yr/heater] N

heater is the total number of heaters owned by the participating companies

The participating companies were requested to pr ovide seasonal utilizatio n rates to account for changes in usage throughout the year.April 2008

G:\IPAMS\Technical_Reports\D-J_Basin\CDPHE_Subm ission\2006_Baseline_Emiss_D-J_Basin_043008.doc 18 Extrapolation to Basin-Wide Emissions

Basin-wide heater emissions were estimated according to Equation 19:

Equation (19) W W E E TOTAL companies heater
TOTAL heater × = 2000 ,

,

where: E

heater,TOTAL is the total heater emissions in the basin [ton/yr] E

heater,companies is the total emissions from all heat ers operated by participating companies [lb/yr] W

TOTAL is the total number of wells in the basin W

is the total number of wells in the ba sin owned by the participating companies

County-level emissions were estimated by allocati ng the total basin-wide heater emissions into each county according to the fraction of total 2006 well counts that are loca ted in each county.

Pneumatic Control Devices

Methodology

Pneumatic device emissions were estimated by de termining the numbers and types of pneumatic devices used at all wells in the basin owned by th e participating companies. The bleed rates of these devices per unit of gas produced were determined by using guidance from the EPA’s Natural Gas Star Program.

The methodology for estimating the emissions from all pneumatic devices owned by participating companies are shown in Equations 20 and 21:

Equation (20) annual i i TOTAL vented t N V V × × = &

,

where: V

vented,TOTAL is the total volume of vented gas from all pneumatic devices for all participating companies [mscf/year]

i V

& is the volumetric bleed rate from device i [mscf/hr/device]

N

i is the total number of device i owned by the participating companies

t annual is the number of hours pe r year that devices were operating [hr/yr]

Equation (21) VOC VOC TOTAL vented pneumatic Y R MW 1000 V E × × × × =

,

where: E

pneumatic is the pneumatic device VOC emissions for all participating companies [lb-VOC/yr] MW VOC is the molecular weight of the VOC [lb/lb-mol] R is the universal gas constant [lb-mol/379scf] Y

is the volume fraction of VOC in the vented gasApril 2008

G:\IPAMS\Technical_Reports\D-J_Basin\CDPHE_Subm ission\2006_Baseline_Emiss_D-J_Basin_043008.doc 19 The conversion from volume of gas vented to ma ss of VOC produced was evaluated at standard temperature and pressure.

Extrapolation to Basin-Wide Emissions

Basin-wide pneumatic device emissions we re estimated according to Equation 22:

Equation (22) W W E E TOTAL pneumatic
TOTAL pneumatic × = 2000 ,

where: E

pneumatic,TOTAL is the total pneumatic device emissions in the basin [ton/yr] E

pneumatic is the pneumatic device VOC emissions for all participating companies [lb-VOC/yr] W

TOTAL is the total number of wells in the basin W

is the total number of wells in the ba sin owned by the participating companies

County-level emissions were estimated by allo cating the total basin-wide pneumatic device emissions into each county according to the fracti on of total 2006 well counts that are located in each county.

Gas Actuated Pumps

Methodology

Participating companies provided data indicating either the average gas consumption rate per gallon of chemical or compound pumped, or the volume rate of gas consumption per day per
pump.

If the gas consumption rate per pump per day was specified, this was multiplied by the number of pumps owned by the respondent and the total annual usage to derive total gas consumption from gas-actuated pumps for the respondent. If th e gas consumption rate per gallon of chemical pumped was specified, this was multiplied by the total volume of chemical pumped by the respondent in the basin in 2006 to derive total gas consumption from gas-actuated pumps for the respondent.

VOC emissions were estimated similarly to pneumatic devices, following Equation 23:

Equation (23) VOC VOC TOTAL vented pump Y R MW 1000 V E × × × × =

,

where: E

pump is the gas-actuated pump VOC emissi ons for all participating companies [lb-VOC/yr] V

vented,TOTAL is the total volume of vented gas from all gas-actuated pumps for all participating companies [mscf/year]April 2008

G:\IPAMS\Technical_Reports\D-J_Basin\CDPHE_Subm ission\2006_Baseline_Emiss_D-J_Basin_043008.doc 20 MW VOC is the molecular weight of the VOC [lb/lb-mol] R is the universal gas constant [lb-mol/379scf] Y

is the volume fraction of VOC in the vented gas

The participating companies were requested to pr ovide seasonal utilizatio n rates to account for changes in usage throughout the year.

Extrapolation to Basin-Wide Emissions

Basin-wide gas-actuated pump emissions were estimated according to Equation 24:

Equation (24) W W E E TOTAL pump TOTAL pump × = 2000 ,

where: E

pump,TOTAL is the total pneumatic pump emissions in the basin [ton/yr] E

pump is the gas-actuated pump VOC emissi ons for all participating companies [lb-VOC/yr] W

TOTAL is the total number of wells in the basin W

is the total number of wells in the ba sin owned by the participating companies

County-level emissions were estimated by allocat ing the total basin-wide gas-actuated pump emissions into each county according to the fracti on of total 2006 well counts that are located in each county.

Produced Water Tanks

Methodology:

Compositional analyses were obtained for water samples collected from produced water tanks for input to the Tanks 4.0 program. Tanks 4.0 wa s used to estimate working and breathing losses based on the water composition analyses obt ained from participating companies.

The average water production per well was derived as the ratio of total water production in the basin to the number of active wells. From this a conserva tive volumetric throughput of 120,000 gallons of water per wellsite was derived. This input to Tanks 4.0 produced an output emissions factor of 0.06 lb-VOC/year/wellsite.

Extrapolation to Basin-Wide Emissions

Basin-wide emissions were derived by multiplyi ng the derived emissions factor per wellsite by the number of active wells in the basin, following Equation 25:April 2008

G:\IPAMS\Technical_Reports\D-J_Basin\CDPHE_Subm ission\2006_Baseline_Emiss_D-J_Basin_043008.doc 21 Equation (25) 2000 tan
tan TOTAL ks water ks water W EF E

−

− =

where: E

water-tanks,TOTAL is the total breathing and working loss emissions of water tanks in the basin [tons/yr] EF water-tanks is the breathing and working loss emissi ons factor for water tanks in the basin [lb-VOC/year/wellsite] W

TOTAL is the total number of wells in the basin

County-level emissions were estimated by allocat ing the total basin-wide water tank emissions into each county according to the fraction of total 2006 well counts that are located in each county.

APEN Exempt Atmospheric Storage Tanks

Methodology

A VOC emissions factor for APEN exempt storage tanks was derived by summing all uncontrolled emissions from Regulation 7 condens ate tanks and dividing by the total production from these same tanks. The resulting emissions factor is 13.86 [lb-VOC/bbl], and assumes that no flares or other controls are in pl ace for APEN exempt condensate tanks.

Extrapolation to Basin-Wide Emissions

Within the ozone non-attainment area, total pr oduction of condensate was obtained from the Regulation 7 reports, which were considered the most accurate estimate of condensate production in this area. GIS analysis was used to intersect the locations of all active wells in the basin with the boundaries of the ozone non-attainment area, in order to deri ve an estimate of the total condensate production in the area based on IHS data. Th e Regulation 7 production total was subtracted from the IHS total for the ozone non-attainment area to derive total condensate production handled by APEN exempt st orage tanks, following Equation 26:

Equation (26) NAA g NAA IHS NAA ks exempt P P P

, 7 Re

, , tan
, − =

where: P exempt,tanks,NAA is the production handled by APEN ex empt storage tanks in the ozone nonattainment area [bbl] P

IHS,NAA is the total condensate produ ction in the ozone non-attain ment area extracted from the IHS database [bbl] P

Reg7,NAA is the total condensate production handled by permitted tanks in the ozone nonattainment area as derived from the Regulation 7 reports [bbl]

Outside of the ozone non-attainment area, a si milar approach was used in which the total production handled by permitted storage tanks was es timated for the condensate tanks listed in the APENs database. This was subtracted from the total production in the basin outside of theApril 2008

G:\IPAMS\Technical_Reports\D-J_Basin\CDPHE_Subm ission\2006_Baseline_Emiss_D-J_Basin_043008.doc 22 non-attainment area to derive total condensat e production handled by APEN exempt storage tanks following Equation 27:

Equation (27) outside APENs outside IHS outside ks exempt P P P

, , , tan
, − =

where: P exempt,tanks,outside is the production handled by APEN ex empt storage tanks outside of the ozone non-attainment area [bbl] P

IHS,outside is the total condensate production ou tside of the ozone non-attainment area extracted from the IHS database [bbl] P

APENs,outside is the total condensate production handl ed by permitted tanks outside of the ozone non-attainment area as derived from th e APENs permits for condensate tanks [bbl]

Total basin-wide VOC emissions from APEN exempt condensate tanks are estimated by Equations 28 and 29:

Equation (28) 2000 tan
, , tan
,

, tan
, ks exempt NAA ks exempt NAA ks exempt EF P E ×

=

and

Equation (29) 2000 tan
, , tan
,

, tan
, ks exempt outside ks exempt outside ks exempt EF P E ×

=

where: E

exempt,tanks,NAA is the basin-wide emissions from ex empt tanks in the ozone non-attainment area [tons/yr] E

exempt,tanks,outside is the basin-wide emissions from ex empt tanks outside of the ozone nonattainment area [tons/yr] EF exempt,tanks is the derived VOC emissions fact or for exempt tanks [lb-VOC/bbl]

County-level emissions were estimated by allo cating the total basin-wide APEN exempt condensate tank emissions into each county acco rding to the fraction of total 2006 condensate production that occurred in each county.

Well Site Land Farming

Methodology

Spill reports submitted to the COGCC in 2006 for any county within the boundaries of the D-J Basin were summarized to determine the type of material released (oil, methanol, or produced water), the volume of material released, and th e volume of material recovered. All oil and methanol not recovered was conservatively assume d to completely volatilize and contribute to VOC emissions. Water spills were no t considered in this analysis.

The above methodology may double count larger spills that were transpor ted to landfarms and thus accounted for in the APEN process.April 2008

G:\IPAMS\Technical_Reports\D-J_Basin\CDPHE_Subm ission\2006_Baseline_Emiss_D-J_Basin_043008.doc 23 Extrapolation to Basin-Wide Emissions

Basin-wide emissions from spills were estimated according to Equation 30:

Equation (30) 2000 , cov i i ered unre spills V E ρ ×

=

where: E

spills is the total basin-wide VOC emissions from spills V

unrecovered,i is the total volume of spilled material of substance i that was unrecovered
ρ

i is the liquid density of substance i

County-level spill emissions were estimated by summing the spill emissions for each county, as indicated by the spill report. Spills that occurred in 2006 we re reported for only the following counties in the D-J Basin:

• Logan

• Morgan

• Washington

• Weld

• Yuma

Truck Loading

Methodology

Truck loading emissions were estimated based on loading losses per EPA AP-42, Section 5.2 methodology combined with condensate produced in the basin. As surveyed producers indicated that all condensate production in the basin was transported by truck, no correction was necessary to adjust condensate production to account for ot her modes of transport. Loading loss emissions were estimated based on EPA AP-42, Sec tion 5.2 methodology, following Equation 31:

Equation (31) ⎟ ⎠ ⎞ ⎜ ⎝ ⎛ × × × = T M V S L 46

. 12

where: L

is the loading lo ss rate [lb/1000gal] S

is the saturation factor taken from AP -42 default values based on operating mode V

is the true vapor pressure of liquid loaded [psia] M is the molecular weight of the vapor [lb/lb-mole] T

is the temperature of the bulk liquid [ o R]

Truck loading emissions for participating comp anies were then estimated by combining the calculated loading loss rate with condensa te production as shown in Equation 32:April 2008

G:\IPAMS\Technical_Reports\D-J_Basin\CDPHE_Subm ission\2006_Baseline_Emiss_D-J_Basin_043008.doc 24 Equation (32) 1000 42
× × = P

L E loading
where: E

is the truck loading emissions [lb/yr] L

is the loading lo ss rate [lb/1000gal] P is the condensate production for the surveyed producers [bbl]

Extrapolation to Basin-Wide Emissions

Basin-wide truck loading emissions were estimated according to Equation 33:

Equation (33) P P E E TOTAL loading
TOTAL loading × = 2000 ,

where: E loading,,TOTAL is the total truck loading emissions in the basin [ton/yr] E loading is the truck loading pump VOC emissi ons for all participating companies [lb-VOC/yr] P TOTAL is the total condensate production in the basin P is the condensate production for the surveyed producers [bbl]

County-level emissions were estimated by allo cating the total basin-wide truck loading emissions into each county subject to Regula tion 7 requirements according to the fraction of within-EAC condensate production for each county.

Flaring

Methodology

For this source category the AP-42 methodology was applied to estimate flare emissions associated with atmospheric storage tanks. Atmo spheric storage tanks vent rates were combined with the heat content of the gas being flared and the appropriate AP-42 emission factor to determine the NOx and CO emissions. Per input from surveyed producers, it was assumed that no flaring occurred outside of the EAC, where c ondensate tanks are not su bject to Regulation 7 control requirements.

Extrapolation to Basin-Wide Emissions

Surveyed producers indicated the use of only two control technologi es to conform to Regulation 7 requirements: flaring and va por recovery units (VRUs). Producers supplied production controlled by VRU which allowed for the calc ulation of production controlled by flaring according to Equation 34. Here it was assumed, conservatively that non surveyed producers used only flare control devices to control emissions from atmospheric storage tanks.April 2008

G:\IPAMS\Technical_Reports\D-J_Basin\CDPHE_Subm ission\2006_Baseline_Emiss_D-J_Basin_043008.doc 25 Equation (34) VRU g CNT g flare P P P

, 7 Re

, 7 Re − =

where: P

flare is the total condensate production ha ndled by permitted tanks in the ozone nonattainment area and controlled by flares [bbl] P

Reg7,CNTis the total condensate production handled by permitted tanks in the ozone nonattainment area and controlled by any technol ogy as estimated in regulation 7 summaries [bbl] P

Reg7,VRU is the total condensate production handled by permitted tanks in the ozone nonattainment area and controlled by VRUs as reported by participating companies [bbl]

Emissions were estimated according to AP-42 methodology, following Equation 35.

Equation (35) HV Q P EF E flare i flare × × × =

where: E

flare is the basinwide flaring emissions [lb/yr] EF i is the emissions factor for pollutant i [lb/MMBtu] Q is the condensate tank vent rate as s upplied by participating companies [scf/bbl] HV is the heating value of the gas as estimat ed by participating companies [BTU/scf] P

flare is the total condensate production ha ndled by permitted tanks in the ozone nonattainment area and controlled by flares [bbl]

County-level emissions were estimated by allo cating the total basin-wide truck loading emissions into each county subject to Regula tion 7 requirements according to the fraction of within EAC condensate production for each county.

Summary Results

Results from the combined permitted sources (APE Ns sources excluding condensate tanks in the ozone non-attainment area, and condensate tanks in the ozone non-attainment area from the Regulation 7 reports), and the combined unperm itted sources are presented below on a county level and as summaries for the entire D-J Basin as a series of pie charts and bar graphs. The quantitative emissions summaries are presented at the end of this document in table format.

Figure 5 shows that NOx emissions are primarily concentrated in Weld and Yuma counties, as evidenced by the areas of large concentrations of well locations, as shown in Figure 1. Figure 6 shows that VOC emissions are pr imarily concentrated in Weld county only. Production activity in Yuma county is mostly dry gas, and theref ore a smaller proportion of total VOC emissions occur in Yuma county.

Figure 7 shows that compressor engines and dril ling rigs combined account for almost 80% of NOx emissions. Similarly, Figure 8 shows th at permitted and unpermitted condensate tanks and pneumatic devices account for approximately 81% of VOC emissions.April 2008

G:\IPAMS\Technical_Reports\D-J_Basin\CDPHE_Subm ission\2006_Baseline_Emiss_D-J_Basin_043008.doc 26 0 2,000 4,000 6,000 8,000 10,000 12,000 14,000

A dam s

A

r ap

ahoe

Boulder Broom f ld Crowley Denver Elbert

F

rem

ont

J efferson Kit Cars Lar

i m

er Lincoln Logan M

organ P h illi

ps P uebl o Sedgwick Washngt n Weld Yum a

CountyNOx Emissions (tons/year) Other Categories

Glycol Dehydrator

Compressor Engines

Workover rigs

Venting - recompletions Pneumatic devices

Permitted Fugitives

Exempt engines

Drill rigs

Figure 5. 2006 NOx emissions by source category and by county in the D-J Basin.

0 20,000 40,000 60,000 80,000 100,000 120,000 140,000AdamsArapahoeBoulderBroomfldCrowleyDenverElbertFremontJeffersonKit CarsLarimerLincolnLoganMorganPhillipsPuebloSedgwickWashngtnWeldYuma

CountyVOC Emissions (tons/year) Other Categories Glycol Dehydrator Compressor Engines
Venting - recompletions
Venting - initial completions
Venting - blowdowns Truck loading of condensate liquid

Small condensate tanks
Pneumatic pumps

Pneumatic devices
Large condensate tanks
Permitted Fugitives
Unpermitted Fugitives
Drill rigs

Figure 6. 2006 VOC emissions by source category and by county in the D-J Basin.April 2008

G:\IPAMS\Technical_Reports\D-J_Basin\CDPHE_Subm ission\2006_Baseline_Emiss_D-J_Basin_043008.doc 27 Drill rigs

25%

Exempt engines 14% Other Categories 1%

Workover rigs 3% Heaters 3% Compressor Engines 55%

Figure 7. D-J Basin NOx emissions proportional contributions by source category

.

Large condensate tanks 50% Other Categories 1%

Pneumatic devices 14% Permitted Fugitives 1% Venting - recompletions 1%

Truck loading of condensate liquid 1% Venting - initial

completions 1%

Small condensate tanks 16%

Pneumatic pumps 1% Venting - blowdowns 2% Unpermitted Fugitives 9% Glycol Dehydrator 1% Compressor Engines 3%

Figure 8. D-J Basin VOC emissions proportional contributions by source category.April 2008

G:\IPAMS\Technical_Reports\D-J_Basin\CDPHE_Subm ission\2006_Baseline_Emiss_D-J_Basin_043008.doc 28 Table 4. 2006 emissions of all criteria pollutants by county for the D-J Basin.

County NOx [tons/yr] VOC [tons/yr] CO [tons/yr] SOx [tons/yr] PM [tons/yr] Adams 2,286 3,005 939 13 19 Arapahoe 742 408 253 0 4 Boulder 129 803 76 1 4 Broomfield 14 193 10 0 0 Crowley 63 1 85 0 1 Denver 32 103 19 0 2 Douglas 0 0 0 0 0 Elbert 43 363 27 0 1 El Paso 0 0 0 0 0 Fremont 16 329 9 0 1 Jefferson 6 0 10 0 0 Kit Carson 10 139 6 0 1 Larimer 37 651 23 0 1 Lincoln 14 462 11 0 0 Logan 491 1,382 183 2 9 Morgan 672 883 672 132 4 Phillips 40 47 26 0 1 Pueblo 0 0 0 0 0 Sedgwick 1 11 0 0 0 Teller 0 0 0 0 0 Washington 284 4,509 207 1 9 Weld 12,310 64,111 8,393 51 421 Yuma 3,592 4,359 1,993 24 158 Totals 20,783 81,758 12,941 226 636April 2008G:\IPAMS\Technical_Reports\D-J_Basin\CDPHE_Submission\2006_Baseline_Emiss_D-J_Basin_043008.doc29Table 5.2006 NOx emissions by county and by source category for the D-J Basin.CountyDrill rigsExemptenginesHeatersWorkoverRigsCompressorEnginesGlycolDehydratorOtherCategoriesTotalsAdams 24 151 30 29 2,041 0 112,286Arapahoe 10 18 4 3 707 0 0742Boulder 31 40 8 8 43 0 1130Broomfield 0 10 2 2 0 0 014Crowley 0 0 0 0 63 0 063Denver 24 6 1 1 0 0 032Douglas 0 0 0 0 0 0 00Elbert 3 10 2 2 26 0 043El Paso 0 0 0 0 0 0 00Fremont 7 6 1 1 0 0 016Jefferson 0 0 0 0 6 0 06Kit Carson 7 2 0 0 0 0 010Larimer 0 23 5 5 5 0 037Lincoln 3 2 0 0 8 0 015Logan 31 19 4 4 44 0 0491Morgan 3 11 2 2 638 8 7672Phillips 10 3 1 1 26 0 040Pueblo 0 0 0 0 0 0 00Sedgwick 0 1 0 0 0 0 01Teller 0 0 0 0 0 0 00Washington 79 78 15 15 97 0 0284Weld 3,012 2,018 400 391 6,363 5 12212,310Yuma 1,906 457 90 89 1,050 0 03,592Totals 5,152 2,854 565 553 11,506 13 141 20,783April 2008G:\IPAMS\Technical_Reports\D-J_Basin\CDPHE_Submission\2006_Baseline_Emiss_D-J_Basin_043008.doc30Table 6.2006 VOC emissions by county and by source category for the D-J Basin.CountyDrillrigsUnpermittedFugitivesPermittedFugitivesLargecondensatetanksPneumaticdevicesPneumaticpumpsSmallcondensatetanksTruckloading ofcondensateliquidVenting –blowdownsVenting -initialcompletionsVenting -recompletionsCompressorEnginesGlycolDehydratorOtherCategoriesTotalsAdams 2 401 84 1,279 614 44 174 23 50 2 3 212 44 75 3,005Arapahoe 1 46 18 176 70 5 24 3 3 1 1 17 22 19 408Boulder 2 105 0 417 172 12 57 7 18 3 4 3 0 4 803Broomfield 0 26 0 100 43 3 14 2 5 0 0 0 0 1 193Crowley 0 0 0 0 0 0 0 0 0 0 0 1 0 0 1Denver 2 15 0 46 23 2 6 1 2 2 3 0 0 1103Douglas 0 0 00 0 0 0 0 0 0 0 0 0 0 0Elbert 0 27 0 0 41 3 214 2 2 0 0 1 0 72 363El Paso 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0Fremont 1 17 0 0 25 2 280 3 0 1 1 0 0 1 329Jefferson 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0Kit Carson 1 5 0 0 8 1 118 1 3 1 1 0 0 0 139Larimer 0 61 0 269 92 7 211 7 2 0 0 0 0 2 651Lincoln 0 5 0 0 8 1 436 4 0 0 0 0 0 7 462Logan 2 51 0 0 77 6 1,160 12 2 3 4 45 9 13 1,382Morgan 0 30 4 0 45 3 514 5 2 0 0 147 54 77 883Phillips 1 9 0 0 13 1 0 0 4 1 1 8 9 0 47Pueblo 0 0 00 0 0 0 0 0 0 0 0 0 0 0Sedgwick 0 1.4 00 2 0 7 0 0 0 0 0 0 0 11Teller 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0Washington 6 206 0 0 312 23 3,684 37 17 8 10 13 8 185 4,509Weld 209 5348 354 38,349 8,164 591 5,977 693 1,360 292 394 1,773 240 367 64,111Yuma 132 1210 0 0 1,834 134 0 0 276 185 249 172 121 47 4,359Totals 357 7564 460 40,636 11,545 836 12,874 800 1,744 500 674 2,393 506 869 81,758