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Subpart W— Petroleum and Natural Gas Systems 

This redline strikeout document represents the changes proposed to the subparts A and W 

regulatory text in the proposed action: 

Greenhouse Gas Reporting Rule: Revisions and Confidentiality Determinations for 

Petroleum and Natural Gas Systems; Proposed Rule 

signed by the EPA Administrator Gina McCarthy on February 20, 2014 

Subpart A:Section 98.6 is amended by revising the definition of “Well completions” to read as 

follows: 

Well completions means the process that allows for the flow of petroleum or natural gas 

from newly drilled wells to expel drilling and reservoir fluids and test the reservoir flow 

characteristics, steps which may vent produced gas to the atmosphere via an open pit or tank. 

Well completion also involves connecting the well bore to the reservoir, which may include 

treating the formation or installing tubing, packer(s), or lifting equipment, steps that do not 

significantly vent natural gas to the atmosphere. This process may also include high-rate 

flowback of injected gas, water, oil, and proppant used to fracture or re-fracture and prop open 

new fractures in existing lower permeability gas reservoirs, steps that may vent large quantities 

of produced gas to the atmosphere. 

Subpart W—Petroleum and Natural Gas Systems is amended as follows:

§98.230 Definition of the source category. 

(a) This source category consists of the following industry segments: 

(1) Offshore petroleum and natural gas production. Offshore petroleum and natural gas 

production is any platform structure, affixed temporarily or permanently to offshore submerged 

lands, that houses equipment to extract hydrocarbons from the ocean or lake floor and that 

processes and/or transfers such hydrocarbons to storage, transport vessels, or onshore. In 

addition, offshore production includes secondary platform structures connected to the platform 
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structure via walkways, storage tanks associated with the platform structure and floating 

production and storage offloading equipment (FPSO). This source category does not include 

reporting of emissions from offshore drilling and exploration that is not conducted on production 

platforms. 

(2) Onshore petroleum and natural gas production. Onshore petroleum and natural gas 

production means all equipment on a single well-pad or associated with a single well-pad 

(including but not limited to compressors, generators, dehydrators, storage vessels, engines, 

boilers, heaters, flares, separation and processing equipment, and portable non-self-propelled 

equipment, which includes well drilling and completion equipment, workover equipment, gravity 

separation equipment, auxiliary non-transportation-relatedmaintenance and repair equipment, 

and leased, rented or contracted equipment) used in the production, extraction, recovery, lifting, 

stabilization, separation or treating of petroleum and/or natural gas (including condensate). This 

equipment also includes associated storage or measurement vessels, and all enhanced oil 

recovery (EOR) operations using CO2 or natural gas injection, and all petroleum and natural gas 

production equipment located on islands, artificial islands, or structures connected by a causeway 

to land, an island, or an artificial island. Onshore petroleum and natural gas production also 

means all equipment on or associated with a single enhanced oil recovery (EOR) well pad using 

CO2 or natural gas injection. 

(3) Onshore natural gas processing. Natural gas processing means the separation of 

natural gas liquids (NGLs) or non-methane gases from produced natural gas, or the separation of 

NGLs into one or more component mixtures. Separation includes one or more of the following: 

forced extraction of natural gas liquids, sulfur and carbon dioxide removal, fractionation of 

NGLs, or the capture of CO2 separated from natural gas streams. This segment also includes all 
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residue gas compression equipment owned or operated by the natural gas processing plant. This 

industry segment includes processing plants that fractionate gas liquids, and processing plants 

that do not fractionate gas liquids but have an annual average throughput of 25 MMscf per day or 

greater. 

(4) Onshore natural gas transmission compression. Onshore natural gas transmission 

compression means any stationary combination of compressors that move natural gas from 

production fields, natural gas processing plants, or other transmission compressors through 

transmission pipelines to natural gas distribution pipelines, LNG storage facilities, or into 

underground storage. In addition, a transmission compressor station includes equipment for 

liquids separation, and tanks for the storage of water and hydrocarbon liquids. Residue (sales) 

gas compression that is part of onshore natural gas processing plants are included in the onshore 

natural gas processing segment and are excluded from this segment. 

(5) Underground natural gas storage. Underground natural gas storage means subsurface 

storage, including depleted gas or oil reservoirs and salt dome caverns that store natural gas that 

has been transferred from its original location for the primary purpose of load balancing (the 

process of equalizing the receipt and delivery of natural gas); natural gas underground storage 

processes and operations (including compression, dehydration and flow measurement, and 

excluding transmission pipelines); and all the wellheads connected to the compression units 

located at the facility that inject and recover natural gas into and from the underground 

reservoirs. 

(6) Liquefied natural gas (LNG) storage. LNG storage means onshore LNG storage 

vessels located above ground, equipment for liquefying natural gas, compressors to capture and 
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re-liquefy boil-off-gas, re-condensers, and vaporization units for re-gasification of the liquefied 

natural gas. 

(7) LNG import and export equipment. LNG import equipment means all onshore or 

offshore equipment that receives imported LNG via ocean transport, stores LNG, re-gasifies 

LNG, and delivers re-gasified natural gas to a natural gas transmission or distribution system. 

LNG export equipment means all onshore or offshore equipment that receives natural gas, 

liquefies natural gas, stores LNG, and transfers the LNG via ocean transportation to any location, 

including locations in the United States. 

(8) Natural gas distribution. Natural gas distribution means the distribution pipelines and 

metering and regulating equipment at metering-regulating stations that are operated by a Local 

Distribution Company (LDC) within a single state that is regulated as a separate operating 

company by a public utility commission or that is operated as an independent municipally-owned 

distribution system. This segment also excludes customer meters and regulators, infrastructure, 

and pipelines (both interstate and intrastate) delivering natural gas directly to major industrial 

users and farm taps upstream of the local distribution company inlet. 

(b) [Reserved] 

§98.231 Reporting threshold. 

(a) You must report GHG emissions under this subpart if your facility contains petroleum 

and natural gas systems and the facility meets the requirements of §98.2(a)(2). Facilities must 

report emissions from the onshore petroleum and natural gas production industry segment only if 

emission sources specified in paragraph §98.232(c) emit 25,000 metric tons of CO2 equivalent or 

more per year. Facilities must report emissions from the natural gas distribution industry segment 
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only if emission sources specified in paragraph §98.232(i) emit 25,000 metric tons of CO2 

equivalent or more per year. 

(b) For applying the threshold defined in §98.2(a)(2), natural gas processing facilities 

must also include owned or operated residue gas compression equipment. 

§98.232 GHGs to report. 

(a) You must report CO2, CH4, and N2O emissions from each industry segment specified 

in paragraph (b) through (i) of this section, CO2, CH4, and N2O emissions from each flare as 

specified in paragraph (b) through (i) of this section, and stationary and portable combustion 

emissions as applicable as specified in paragraph (k) of this section. 

(b) For offshore petroleum and natural gas production, report CO2, CH4, and N2O 

emissions from equipment leaks, vented emission, and flare emission source types as identified 

in the data collection and emissions estimation study conducted by BOEMRE in compliance 

with 30 CFR 250.302 through 304. Offshore platforms do not need to report portable emissions. 

(c) For an onshore petroleum and natural gas production facility, report CO2, CH4, and 

N2O emissions from only the following source types on a single well-pad or associated with a 

single well-pad: 

(1) Natural gas pneumatic device venting. 

(2) [Reserved] 

(3) Natural gas driven pneumatic pump venting. 

(4) Well venting for liquids unloading. 

(5) Gas well venting during well completions without hydraulic fracturing. 

(6) Gas well venting during well completions with hydraulic fracturing. 

(7) Gas well venting during well workovers without hydraulic fracturing. 
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(8) Gas well venting during well workovers with hydraulic fracturing. 

(9) Flare stack emissions. 

(10) Storage tanks vented emissions from produced hydrocarbons. 

(11) Reciprocating compressor rod packing venting. 

(12) Well testing venting and flaring. 

(13) Associated gas venting and flaring from produced hydrocarbons. 

(14) Dehydrator vents. 

(15) [Reserved] 

(16) EOR injection pump blowdown. 

(17) Acid gas removal vents. 

(18) EOR hydrocarbon liquids dissolved CO2. 

(19) Centrifugal compressor venting. 

(20) [Reserved] 

(21) Equipment leaks from valves, connectors, open ended lines, pressure relief valves, 

pumps, flanges, and other equipment leak sources (such as instruments, loading arms, stuffing 

boxes, compressor seals, dump lever arms, and breather caps). 

(22) You must use the methods in §98.233(z) and report under this subpart the emissions 

of CO2, CH4, and N2O from stationary or portable fuel combustion equipment that cannot move 

on roadways under its own power and drive train, and that is located at an onshore petroleum and 

natural gas production facility as defined in §98.238. Stationary or portable equipment are the 

following equipment, which are integral to the extraction, processing, or movement of oil or 

natural gas: well drilling and completion equipment, workover equipment, natural gas 

dehydrators, natural gas compressors, electrical generators, steam boilers, and process heaters. 
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(d) For onshore natural gas processing, report CO2, CH4, and N2O emissions from the 

following sources: 

(1) Reciprocating compressor rod packing venting. 

(2) Centrifugal compressor venting. 

(3) Blowdown vent stacks. 

(4) Dehydrator vents. 

(5) Acid gas removal vents. 

(6) Flare stack emissions. 

(7) Equipment leaks from valves, connectors, open ended lines, pressure relief valves, 

and meters. 

(e) For onshore natural gas transmission compression, report CO2, CH4, and N2O 

emissions from the following sources: 

(1) Reciprocating compressor rod packing venting. 

(2) Centrifugal compressor venting. 

(3) Transmission storage tanks. 

(4) Blowdown vent stacks. 

(5) Natural gas pneumatic device venting. 

(6) [Reserved]Flare stack emissions.

(7) Equipment leaks from valves, connectors, open ended lines, pressure relief valves, 

and meters. 

(f) For underground natural gas storage, report CO2, CH4, and N2O emissions from the 

following sources: 

(1) Reciprocating compressor rod packing venting. 
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(2) Centrifugal compressor venting. 

(3) Natural gas pneumatic device venting. 

(4) [Reserved]Flare stack emissions.

(5) Equipment leaks from valves, connectors, open ended lines, pressure relief valves, 

and meters. 

(g) For LNG storage, report CO2, CH4, and N2O emissions from the following sources: 

(1) Reciprocating compressor rod packing venting. 

(2) Centrifugal compressor venting. 

(3) Equipment leaks from valves; pump seals; connectors; vapor recovery compressors, 

and other equipment leak sources. 

(4) Flare stack emissions. 

(h) LNG import and export equipment, report CO2, CH4, and N2O emissions from the 

following sources: 

(1) Reciprocating compressor rod packing venting. 

(2) Centrifugal compressor venting. 

(3) Blowdown vent stacks. 

(4) Equipment leaks from valves, pump seals, connectors, vapor recovery compressors, 

and other equipment leak sources. 

(5) Flare stack emissions. 

(i) For natural gas distribution, report CO2, CH4, and N2O emissions from the following 

sources: 

(1) Meters, regulators, and associated equipment at above grade transmission-distribution 

transfer stations, including equipmentEquipment leaks from connectors, block valves, control 
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valves, pressure relief valves, orifice meters, regulators, and open-ended lines at above grade 

transmission-distribution transfer stations. 

(2) Equipment leaks from vaults at below grade transmission-distribution transfer 

stations. 

(3) Meters, regulators, and associated equipment Equipment leaks at above grade 

metering-regulating stationstations that are not above grade transmission-distribution transfer 

stations. 

(4) Equipment leaks from vaults at below grade metering-regulating stations. 

(5) PipelineDistribution main equipment leaks. 

(6) Service lineDistribution services equipment leaks. 

(7) Report under subpart W of this part the emissions of CO2, CH4, and N2O emissions 

from stationary fuel combustion sources following the methods in §98.233(z).

(j) [Reserved] 

(k) Report under subpart C of this part (General Stationary Fuel Combustion Sources) the 

emissions of CO2, CH4, and N2O from each stationary fuel combustion unit by following the 

requirements of subpart C except for facilities under onshore petroleum and natural gas 

production and natural gas distribution. Onshore petroleum and natural gas production facilities 

must report stationary and portable combustion emissions as specified in paragraph (c) of this 

section. Natural gas distribution facilities must report stationary combustion emissions as 

specified in paragraph (i) of this section. 

(l) You must report under subpart PP of this part (Suppliers of Carbon Dioxide), CO2 

emissions captured and transferred off site by following the requirements of subpart PP. 

§98.233 Calculating GHG emissions. 
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You must calculate and report the annual GHG emissions as prescribed in this section. 

For actual conditions, reporters must use average atmospheric conditions or typical operating 

conditions as applicable to the respective monitoring methods in this section. 

(a) Natural gas pneumatic device venting. Calculate CH4 and CO2 volumetric emissions 

from continuous high bleed, continuous low bleed, and intermittent bleed natural gas pneumatic 

devices using Equation W-1 of this section. 

 

t

i

Es i Countt EFt GHGi Tt * * * , (Eq. W-1) 

Where: 

MasstEs,i = Annual total massvolumetric GHG emissions at standard conditions in metric 

tons CO2estandard cubic feet per year from a natural gas pneumatic device 

vents, of types “t”,” (continuous high bleed, continuous low bleed, 

intermittent bleed), for GHGi. 

Countt = Total number of natural gas pneumatic devices of type “t” (continuous high 

bleed, continuous low bleed, intermittent bleed) as determined in paragraph 

(a)(1),) or (a)(2), and (a)(3) of this section. 

EFt = Population emission factors for natural gas pneumatic device ventingvents (in 

standard cubic feet per hour per device) of each type “t” listed in Tables W1A, W-3, and W-4 of this subpart for onshore petroleum and natural gas 

production, onshore natural gas transmission compression, and underground 

natural gas storage facilities, respectively. 

GHGi = For onshore petroleum and natural gas production facilities, concentration of 

GHGi, CH4, or CO2, in natural gas as defined in paragraph (u)(2)(i) of this 

section and for onshore natural gas transmission compression facilities, and 

underground natural gas storage, GHGi equals 0.975 for CH4 and 1.1 × 10−2

for CO2 facilities, concentration of GHGi, CH4 or CO2, in produced natural 

gas or processed natural gas for each facility as specified in paragraphs 

(u)(2)(i), (iii), and (iv) of this section. 

Convi = Conversion from standard cubic feet to metric tons CO2e; 0.000479 for CH4,

and 0.00005262 for CO2.

Tt = Average estimated number of hours in the operating year the devices, of each 

type “t,”, were operational using engineering estimates based on best 

available data. Default is 8760 hours. 
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(1) For all industry segments, determine “Countt” for Equation W-1 of this subpart for 

each type of natural gas pneumatic device (continuous high bleed, continuous low bleed, and 

intermittent bleed) by counting the devices, except as specified in paragraph (a)(2) of this 

section. The reported number of devices must represent the total number of devices for the 

reporting year. onshore petroleum and natural gas production, provide the total number of 

continuous high bleed, continuous low bleed, or intermittent bleed natural gas pneumatic devices 

of each type as follows:

(i) In the first calendar year, for the total number of each type, you may count the total of 

each type, or count any percentage number of each type plus an engineering estimate based on 

best available data of the number not counted.

(ii) In the second consecutive year, for the total number of each type, you may count the 

total of each type, or count any percentage number of each type plus an engineering estimate 

based on best available data of the number not counted.

(iii) In the third consecutive calendar year, complete the count of all pneumatic devices, 

including any changes to equipment counted in prior years.

(iv) For the calendar year immediately following the third consecutive calendar year, and 

for calendar years thereafter, facilities must update the total count of pneumatic devices and 

adjust accordingly to reflect any modifications due to changes in equipment.

(2) For onshore natural gas transmission compression and underground natural gas 

storage, all natural gas pneumatic devices must be counted in the first year and updated every 

calendar year. For the onshore petroleum and natural gas production industry segment, you have 

the option in the first two consecutive calendar years to determine “Countt” for Equation W-1 of 
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this subpart for each type of natural gas pneumatic device (continuous high bleed, continuous 

low bleed, and intermittent bleed) using engineering estimates based on best available data.

(3) For all industry segments, determine the type of pneumatic device using engineering 

estimates based on best available information. 

(4) Calculate both CH4 and CO2 mass emissions from volumetric emissions using 

calculations in paragraph (v) of this section. 

(b) [Reserved] 

(c) Natural gas driven pneumatic pump venting. (1) Calculate CH4 and CO2 volumetric

emissions from natural gas driven pneumatic pump venting using Equation W-2 of this section. 

Natural gas driven pneumatic pumps covered in paragraph (e) of this section do not have to 

report emissions under this paragraph (c) of this section.).

Es,i  Count * EF * GHGi * T (Eq. W-2) 

Where: 

MassiEs,i = Annual total massvolumetric GHG emissions at standard conditions in metric 

tons CO2estandard cubic feet per year from all natural gas driven pneumatic 

pump venting, for GHGi. 

Count = Total number of natural gas driven pneumatic pumps. 

EF = Population emissions factors for natural gas driven pneumatic pumps (in 

standard cubic feet per hour per pump venting) listed in Tables W-1A of this 

subpart for onshore petroleum and natural gas production. 

GHGi = Concentration of GHGi, CH4, or CO2, in produced natural gas as defined in 

paragraph (u)(2)(i) of this section. 

Convi = Conversion from standard cubic feet to metric tons CO2e; 0.000479 for CH4,

and 0.00005262 for CO2.

T = Average estimated number of hours in the operating year the pumps were 

operational using engineering estimates based on best available data. Default 

is 8760 hours. 
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(2) Calculate both CH4 and CO2 mass emissions from volumetric emissions using 

calculations in paragraph (v) of this section. 

(d) Acid gas removal (AGR) vents. For AGR vents (including processes such as amine, 

membrane, molecular sieve or other absorbents and adsorbents), calculate emissions for CO2

only (not CH4) vented directly to the atmosphere or emitted through a flare, engine (e.g., 

permeate from a membrane or de-adsorbed gas from a pressure swing adsorber used as fuel 

supplement), or sulfur recovery plant, using any of the calculation methodologies described in 

this paragraph (d) of this section, as applicable. 

(1) Calculation Methodology 1. If you operate and maintain a continuous emissions 

monitoring system (CEMS) that has both a CO2 concentration monitor and volumetric flow rate 

monitor, you must calculate CO2 emissions under this subpart by following the Tier 4 

Calculation Methodology and all associated calculation, quality assurance, reporting, and 

recordkeeping requirements for Tier 4 in subpart C of this part (General Stationary Fuel 

Combustion Sources). Alternatively, you may follow the manufacturer’s instructions or industry 

standard practice. If a CO2 concentration monitor and volumetric flow rate monitor are not 

available, you may elect to install a CO2 concentration monitor and a volumetric flow rate 

monitor that comply with all of the requirements specified for the Tier 4 Calculation 

Methodology in subpart C of this part (General Stationary Fuel Combustion Sources). The 

calculation and reporting of CH4 and N2O emissions is not required as part of the Tier 4 

requirements for AGRsAGR units. 

(2) Calculation Methodology 2. If a CEMS is not available but a vent meter is installed, 

use the CO2 composition and annual volume of vent gas to calculate emissions using Equation 

W-3 of this section. 
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2 , 2 * CO a CO E  Vs Vol Ea,CO2 = VS * VolCO2 (Eq. W-3) 

Where: 

Ea,CO2 = Annual volumetric CO2 emissions at actual conditions, in cubic feet per year. 

VS = Total annual volume of vent gas flowing out of the AGR unit in cubic feet 

per year at actual conditions as determined by flow meter using methods set 

forth in §98.234(b). Alternatively, you may follow the manufacturer’s 

instructions or industry standard practice for calibration of the vent meter. 

VolCO2 = VolumeAnnual average volumetric fraction of CO2 content in vent gas 

flowing out of the AGR unit as determined in paragraph (d)(6) of this section. 

(3) Calculation Methodology 3. If a CEMS or a vent meter is not installed, you may use 

the inlet or outlet gas flow rate of the acid gas removal unit to calculate emissions for CO2 using 

Equations W-4A or W-4B of this section. If inlet gas flow rate is known, use Equation W-4A. If 

outlet gas flow rate is known, use Equation W-4B. 





 







  

O

I O

a CO in Vol

Vol Vol E V

1 , 2 (Eq. W-4A) 





 







  

I

I O

a CO out Vol

Vol Vol E V

1 , 2 (Eq. W-4B) 

Where: 

Ea, CO2 = Annual volumetric CO2 emissions at actual conditions, in cubic feet per year. 

Vin = Total annual volume of natural gas flow into the AGR unit in cubic feet per 

year at actual conditions as determined using methods specified in paragraph 

(d)(5) of this section. 

Vout = Total annual volume of natural gas flow out of the AGR unit in cubic feet per 

year at actual conditions as determined using methods specified in paragraph 

(d)(5) of this section. 

VolI = VolumeAnnual average volumetric fraction of CO2 content in natural gas 

flowing into the AGR unit as determined in paragraph (d)(7) of this section. 
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Volo = VolumeAnnual average volumetric fraction of CO2 content in natural gas 

flowing out of the AGR unit as determined in paragraph (d)(8) of this section. 

(4) Calculation Methodology 4. If CEMS or a vent meter is not installed, you may 

calculate emissions using any standard simulation software packages, such as AspenTech 

HYSYS® and, or API 4679 AMINECalc, that uses the Peng-Robinson equation of state, and 

speciates CO2 emissions. A minimum of the following, determined for typical operating 

conditions over the calendar year by engineering estimate and process knowledge based on best 

available data, must be used to characterize emissions: 

(i) Natural gas feed temperature, pressure, and flow rate. 

(ii) Acid gas content of feed natural gas. 

(iii) Acid gas content of outlet natural gas. 

(iv) Unit operating hours, excluding downtime for maintenance or standby. 

(v) Exit temperature of natural gas. 

(vi) Solvent pressure, temperature, circulation rate, and weight. 

(5) RecordFor Calculation Method 3, determine the gas flow rate of the inlet andwhen 

using Equation W-4A of this section or the gas flow rate of the outlet when using Equation W4B of this section for the natural gas stream of an AGR unit using a meter according to methods 

set forth in §98.234(b). If you do not have a continuous flow meter, either install a continuous 

flow meter or use an engineering calculation to determine the flow rate. 

(6) IfFor Calculation Method 2, if a continuous gas analyzer is not available on the vent 

stack, either install a continuous gas analyzer or take quarterly gas samples from the vent gas 

stream to determine VolCO2 in Equation W-3 of this section according to methods set forth in 

§98.234(b). 
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(7) IfFor Calculation Method 3, if a continuous gas analyzer is installed on the inlet gas 

stream, then the continuous gas analyzer results must be used. If a continuous gas analyzer is not 

available, either install a continuous gas analyzer or take quarterly gas samples from the inlet gas 

stream to determine VolI in Equation W-4A or W-4B of this section according to methods set 

forth in §98.234(b). 

(8) Determine volumeFor Calculation Method 3, determine annual average volumetric

fraction of CO2 content in natural gas flowing out of the AGR unit using one of the methods 

specified in paragraphs (d)(8)(i) through (d)(8)(iii) of this section. 

(i) If a continuous gas analyzer is installed on the outlet gas stream, then the continuous 

gas analyzer results must be used. If a continuous gas analyzer is not available, you may install a 

continuous gas analyzer. 

(ii) If a continuous gas analyzer is not available or installed, quarterly gas samples may 

be taken from the outlet gas stream to determine VolO in Equation W-4A or W-4B of this section 

according to methods set forth in §98.234(b). 

(iii) UseIf a continuous gas analyzer is not available or installed, you may use sales line 

quality specification for CO2 in natural gas. 

(9) Calculate CO2annual volumetric CO2 emissions at standard conditions using 

calculations in paragraph (t) of this section. 

(10) Calculate annual Mmass CO2 emissions shall be calculated from volumetric CO2

emissions at standard conditions using calculations in paragraph (v) of this section. 

(11) Determine if CO2 emissions from the AGR unit are recovered and transferred 

outside the facility. Adjust the CO2 emissions estimated in paragraphs (d)(1) through (d)(10) of 
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this section downward by the magnitude of CO2 emissions recovered and transferred outside the 

facility. 

(e) Dehydrator vents. For dehydrator vents, calculate annual CH4 and CO2 emissions 

using the applicable calculation methods described in paragraphs (e)(1) through (e)(4) of this 

section. If emissions from dehydrator vents are routed to a vapor recovery system, you must 

adjust the emissions downward according to paragraph (e)(5) of this section. If emissions from 

dehydrator vents are routed to a flare or regenerator fire-box/fire tubes, you must calculate CH4, 

CO2, and N2O annual emissions as specified in paragraph (e)(6) of this section.calculate annual 

CH4, CO2 and N2O emissions using any of the calculation methodologies described in paragraph 

(e) of this section.

(1) Calculation Methodology 1. Calculate annual mass emissions from dehydrator vents 

withabsorbent dehydrators that have an annual average of daily natural gas throughput that is 

greater than or equal to 0.4 million standard cubic feet per day by using a software program, such 

as AspenTech HYSYS® or GRI-GLYCalcTM, that uses the Peng-Robinson equation of state to 

calculate the equilibrium coefficient, speciates CH4 and CO2 emissions from dehydrators, and 

has provisions to include regenerator control devices, a separator flash tank, stripping gas and a 

gas injection pump or gas assist pump. A minimum of theThe following parameters must be 

determined by engineering estimate based on best available data and must be used at a minimum

to characterize emissions from dehydrators: 

(i) Feed natural gas flow rate. 

(ii) Feed natural gas water content. 

(iii) Outlet natural gas water content. 

(iv) Absorbent circulation pump type (e.g., natural gas pneumatic/air pneumatic/electric). 
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(v) Absorbent circulation rate. 

(vi) Absorbent type: including (e.g., triethylene glycol (TEG), diethylene glycol (DEG) 

or ethylene glycol (EG).).

(vii) Use of stripping gas. 

(viii) Use of flash tank separator (and disposition of recovered gas). 

(ix) Hours operated. 

(x) Wet natural gas temperature and pressure. 

(xi) Wet natural gas composition. Determine this parameter by selectingusing one of the 

methods described underin paragraphs (e)(1)(xi)(A) through (e)(1)(xi)(D) of this section. 

(A) Use the wet natural gas compositionGHG mole fraction as defined in paragraph 

(u)(2)(i) or (u)(2)(ii) of this section. 

(B) If wet natural gas compositionthe GHG mole fraction cannot be determined using 

paragraph (u)(2)(i) or (u)(2)(ii) of this section, select a representative analysis. 

(C) You may use an appropriate standard method published by a consensus-based 

standards organization if such a method exists or you may use an industry standard practice as 

specified in §98.234(b) to sample and analyze wet natural gas composition. 

(D) If only composition data for dry natural gas is available, assume the wet natural gas is 

saturated. 

(2) Calculation Methodology 2. Calculate annual CH4 and CO2volumetric emissions from 

glycol dehydrators withthat have an annual average of daily natural gas throughput that is less 

than 0.4 million standard cubic feet per day using Equation W-5 of this section: 

Es,i EFi *Count*1000 (Eq. W-5) 
Page 19 of 214 

This document showing the proposed amendments to subparts A and W is provided for informational 

puroposes only. We have taken steps to ensure the accuracy of this version, but it is not the official version. 

Where: 

Es,i = Annual total volumetric GHG emissions (either CO2 or CH4) at standard 

conditions in cubic feet. 

EFi = Population emission factors for glycol dehydrators in thousand standard cubic 

feet per dehydrator per year. Use 73.4 for CH4andCH4 and 3.21 for CO2 at 60 

°F and 14.7 psia. 

Count = Total number of glycol dehydrators withthat have an annual average of daily 

natural gas throughput that is less than 0.4 million standard cubic feet per 

day. 

1000 = Conversion of EFi in thousand standard cubic feet to standard cubic feet. 

(3) Determine if dehydrator unit has vapor recovery. Adjust the emissions estimated in 

paragraphs (e)(1) or (e)(2) of this section downward by the magnitude of emissions captured.

(4) Calculate annual emissions from dehydrator vents to flares or regenerator fire-box/fire 

tubes as follows:

(A) Use the dehydrator vent volume and gas composition as determined in paragraphs 

(e)(1) and (e)(2) of this section.

(B) Use the calculation methodology of flare stacks in paragraph (n) of this section to 

determine dehydrator vent emissions from the flare or regenerator combustion gas vent. 

(5) Dehydrators that use desiccant shall calculate emissions from the amount of gas 

vented from the vessel when it is depressurized for the desiccant refilling process using Equation 

W-6 of this section. Desiccant dehydrators covered in (e)(5) of this section do not have to report 

emissions under (i) of this section. Calculation Method 3. Dehydrators that use desiccant must 

calculate emissions from the amount of gas vented from the vessel when it is depressurized for 

the desiccant refilling process using Equation W-6 of this section. Desiccant dehydrator 

emissions covered in this paragraph do not have to be calculated separately using the method 

specified in paragraph (i) of this section for blowdown vent stacks.
Page 20 of 214 

This document showing the proposed amendments to subparts A and W is provided for informational 

puroposes only. We have taken steps to ensure the accuracy of this version, but it is not the official version. 

 

(4* *100)

* * * *% *

1

2

2

, P

H D p P G N Es n

 (Eq. W-6) 

Where: 

Es,n = Annual natural gas emissions at standard conditions in cubic feet. 

H = Height of the dehydrator vessel (ft). 

D = Inside diameter of the vessel (ft). 

P1 = Atmospheric pressure (psia). 

P2 = Pressure of the gas (psia). 

Pp = pi (3.14). 

%G = Percent of packed vessel volume that is gas. 

N = Number of dehydrator openings in the calendar year. 

100 = Conversion of %G to fraction. 

(64) For glycol dehydrators, both CH4 and CO2 mass emissions shall be calculated from 

volumetric GHGi emissions using calculations in paragraph (v) of this section. For dehydrators 

that use desiccant, both CH4 and CO2 volumetric and mass emissions shall be calculated from 

volumetric natural gas emissions using calculations in paragraphs (u) and (v) of this section. For 

glycol dehydrators that use the calculation method in paragraph (e)(2) of this section, calculate 

both CH4 and CO2 mass emissions from volumetric GHGi emissions using calculations in 

paragraph (v) of this section. For desiccant dehydrators that use the calculation method in 

paragraph (e)(3) of this section, calculate both CH4 and CO2 volumetric and mass emissions 

from volumetric natural gas emissions using calculations in paragraphs (u) and (v) of this 

section.

(5) Determine if the dehydrator unit has vapor recovery. Adjust the emissions estimated 

in paragraphs (e)(1), (e)(2), and (e)(3) of this section downward by the magnitude of emissions 
Page 21 of 214 

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puroposes only. We have taken steps to ensure the accuracy of this version, but it is not the official version. 

recovered using a vapor recovery system as determined by engineering estimate based on best 

available data. 

(6) Calculate annual emissions from dehydrator vents to flares or regenerator fire-box/fire 

tubes as follows: 

(i) Use the dehydrator vent volume and gas composition as determined in paragraphs 

(e)(1) or (e)(2) of this section for absorbent dehydrators. Use the dehydrator vent volume and gas 

composition as determined in paragraphs (e)(3) and (e)(4) of this section for dehydrators that use 

desiccant. 

(ii) Use the calculation method of flare stacks in paragraph (n) of this section to 

determine dehydrator vent emissions from the flare or regenerator combustion gas vent. 

(f) Well venting for liquids unloadings. Calculate CO2 and CH4annual volumetric natural 

gas emissions from well venting for liquids unloading using one of the calculation 

methodologies described in paragraphs (f)(1), (f)(2), or (f)(3) of this section. Calculate annual 

CH4 and CO2 volumetric and mass emissions using the method described in paragraph (f)(4) of 

this section.

(1) Calculation Methodology 1.Method 1. Calculate emissions from wells with plunger 

lifts and wells without plunger lifts separately. For at least one well of each unique well tubing 

diameter group and pressure group combination in each sub-basin category (see §98.238 for the 

definitions of tubing diameter group, pressure group, and sub-basin category), where gas wells 

are vented to the atmosphere to expel liquids accumulated in the tubing, install a recording flow 

meter shall be installed on the vent line used to vent gas from the well (e.g., on the vent line off 

the wellhead separator or atmospheric storage tank) according to methods set forth in 

§98.234(b). Calculate the total emissions from well venting to the atmosphere for liquids 
Page 22 of 214 

This document showing the proposed amendments to subparts A and W is provided for informational 

puroposes only. We have taken steps to ensure the accuracy of this version, but it is not the official version. 

unloading using Equation W-7A of this section. For any tubing diameter group and pressure 

group combination in a sub-basin where liquids unloading occurs both with and without plunger 

lifts, Equation W-7A will be used twice, once for wells with plunger lifts and once for wells 

without plunger lifts. 





h

p

Ea FR Tp

1

 (Eq. W-7A) 

Where: 

Ea,n = Annual natural gas emissions for all wells of the same tubing diameter group 

and pressure group combination in a sub-basin at actual conditions in cubic 

feet, a, in cubic feet. Calculate emission from wells with plunger lifts and 

wells without plunger lifts separately. 

h = Total number of wells of the same tubing diameter group and pressure group 

combination in a sub-basin either with or without plunger lifts. 

p = Wells 1 through h of the same tubing diameter group and pressure group 

combination in a sub-basin. 

Tp = Cumulative amount of time in hours of venting for each well, p, of the same 

tubing diameter group and pressure group combination in a sub-basin during 

the year. If the available venting data do not contain a record of the date of 

the venting events and data are not available to provide the venting hours for 

the specific time period of January 1 to December 31, you may calculate an 

annualized vent time, Tp, using Equation W-7B of this section. 

FR = Average flow rate in cubic feet per hour for all measured wells venting forof 

the same tubing diameter group and pressure group combination in a subbasin, over the duration of the liquids unloading, under actual conditions as 

determined in paragraph (f)(1)(i) of this section. 

x p

p p

p

HR

T D

MP  (Eq. W-7B) 

Where: 

HRp = Cumulative amount of time in hours of venting for each well, p, during the 

monitoring period. 
Page 23 of 214 

This document showing the proposed amendments to subparts A and W is provided for informational 

puroposes only. We have taken steps to ensure the accuracy of this version, but it is not the official version. 

MPp = Time period, in days, of the monitoring period for each well, p. A minimum 

of 300 days in a calendar year are required. The next period of data collection 

must start immediately following the end of data collection for the previous 

reporting year. 

Dp = Time period, in days during which the well, p, was in production (365 if the 

well was in production for the entire year). 

(i) Determine the well vent average flow rate (“FR” in Equation W-7A of this section) as 

specified under paragraphin paragraphs (f)(1)(i)(A) through (f)(1)(i)(C) of this section for at least 

one well in a unique well tubing diameter group and pressure group combination in each subbasin category. Calculate emissions from wells with plunger lifts and wells without plunger lifts 

separately.

(A) TheCalculate the average flow rate per hour of venting is calculated for each unique 

tubing diameter group and pressure group combination in each sub-basin category by dividing 

the recorded total annual flow by the recorded time (in hours) for all measured liquid unloading 

events with venting to the atmosphere. 

(B) ThisApply the average hourly flow rate per hour is appliedcalculated under paragraph 

(f)(1)(i)(A) of this section to all wells in the same pressure group that have the same tubing 

diameter group, for the number of hours of venting these wells. 

(C) ACalculate a new average flow rate is calculated every other calendar year for each 

reporting sub-basin category starting with the first calendar year of data collection. For a new 

producing sub-basin category, calculate an average flow rate is calculated beginning in the first 

year of production. 

(ii) Calculate natural gas volumetric emissions at standard conditions using calculations 

in paragraph (t) of this section. 
Page 24 of 214 

This document showing the proposed amendments to subparts A and W is provided for informational 

puroposes only. We have taken steps to ensure the accuracy of this version, but it is not the official version. 

(2) Calculation Methodology 2. Calculate the total emissions for each sub-basin from 

well venting to the atmosphere for liquids unloading without plunger lift assist using Equation 

W-8 of this section. 

           







 



          

W

p

V

q

s p p p p p p q p q

p

E V CD WD SP SFR HR Z 1 1

, ,

3 2 0.37 10 1.0 (Eq. W-8) 

Where: 

Es,n = Annual natural gas emissions for each sub-basin at standard conditions, s, in 

cubic feet/ per year. 

W = Total number of wells with well venting for liquids unloading for each subbasin. 

p = Wells 1 through W with well venting for liquids unloading for each subbasin. 

Vp = Total number of unloading events in the monitoring period per well, p. 

0.37×10−3 = {3.14 (pi)/4}/{14.7*144} (psia converted to pounds per square feet). 

CDp = Casing internal diameter for each well, p, in inches. 

WDp = Well depth from either the top of the well or the lowest packer to the bottom 

of the well, for each well, p, in feet. 

SPp = For each well, p, shut-in pressure or surface pressure for wells with tubing 

production, or casing pressure for each well with no packers, in pounds per 

square inch absolute (psia); or casing-to-tubing pressure ratio of one well 

with no packer from the same sub-basin multiplied by the tubing pressure of 

each well, p, in the sub-basin, in pounds per square inch absolute (psia). If 

casing pressure is not available for each well, you may determine the casing 

pressure by multiplying the tubing pressure of each well with a ratio of casing 

pressure to tubing pressure from a well in the same sub-basin for which the 

casing pressure is known. The tubing pressure must be measured during gas 

flow to a flow-line. The shut-in pressure, surface pressure, or casing pressure 

must be determined just prior to liquids unloading when the well production 

is impeded by liquids loading or closed to the flow-line by surface valves. 

Vp = Number of unloading events per year per well, p.
Page 25 of 214 

This document showing the proposed amendments to subparts A and W is provided for informational 

puroposes only. We have taken steps to ensure the accuracy of this version, but it is not the official version. 

SFRp = Average flow-line rate of gas for well, p, at standard conditions in cubic feet 

per hour. Use Equation W-33 of this section to calculate the average flowline rate at standard conditions. 

HRp,q = Hours that each well, p, was left open to the atmosphere during each 

unloading event, q. 

1.0 = Hours for average well to blowdown casing volume at shut-in pressure. 

q = Unloading event. 

Zp,q = If HRp,q is less than 1.0 then Zp,q is equal to 0. If HRp,q is greater than or equal 

to 1.0 then Zp,q is equal to 1. 

(3) Calculation Methodology 3. Calculate the total emissions for each sub-basin from 

well venting to the atmosphere for liquids unloading with plunger lift assist using Equation W-9 

of this section.

           







 



          

W

p

V

q

s p p p p p p q p q

p

E V TD WD SP SFR HR Z 1 1

, ,

3 2 0.37 10 0.5 (Eq. W-9) 

Where: 

Es,n = Annual natural gas emissions for each sub-basin at standard conditions, s, in 

cubic feet/ per year. 

W = Total number of wells with plunger lift assist and well venting for liquids 

unloading for each sub-basin. 

p = Wells 1 through W with well venting for liquids unloading for each subbasin. 

Vp = Total number of unloading events in the monitoring period for each well, p. 

0.37×10−3 = {3.14 (pi)/4}/{14.7*144} (psia converted to pounds per square feet). 

TDp = Tubing internal diameter for each well, p, in inches. 

WDp = Tubing depth to plunger bumper for each well, p, in feet. 

SPp = Flow-line pressure for each well, p, in pounds per square inch absolute (psia), 

using engineering estimate based on best available data. 

Vp = Number of unloading events per year for each well, p.
Page 26 of 214 

This document showing the proposed amendments to subparts A and W is provided for informational 

puroposes only. We have taken steps to ensure the accuracy of this version, but it is not the official version. 

SFRp = Average flow-line rate of gas for well, p, at standard conditions in cubic feet 

per hour. Use Equation W-33 of this section to calculate the average flowline rate at standard conditions. 

HRp,q = Hours that each well, p, was left open to the atmosphere during each 

unloading event, q. 

0.5 = Hours for average well to blowdown tubing volume at flow-line pressure. 

q = Unloading event. 

Zp,q = If HRp,q is less than 0.5 then Zp,q is equal to 0. If HRp,q is greater than or equal 

to 0.5 then Zp,q is equal to 1. 

(i)-(ii) [Reserved]

(4) BothCalculate CH4 and CO2 volumetric and mass emissions shall be calculated from 

volumetric natural gas emissions using calculations in paragraphs (u) and (v) of this section. 

(g) Gas well venting during completions and workovers fromwith hydraulic fracturing. 

Calculate CH4, CO2 and N2O annual emissions from gas well venting during completions 

involving hydraulic fracturing in wells and well workovers using Equation W-10A or Equation 

W-10B of this section. Equation W-10A applies to well venting when the backflow rate is 

measured or calculated, Equation W-10B applies when the backflow vent or flare volume is 

measured. Use Equation W-10A if the flow rate for backflow during well completions and 

workovers from hydraulic fracturing is known for the specified number of wells per paragraph 

(g)(1) in a sub-basin and well type (horizontal or vertical) combination. Use Equation W-10B if 

the flow volume for backflow during well completions and workovers from hydraulic fracturing 

is known for all wells in a sub-basin and well type (horizontal or vertical) combination. Both

CH4 and CO2 volumetric and mass emissions shall be calculated from volumetric total gas

emissions using calculations in paragraphs (u) and (v) of this section. Calculate annual 

volumetric natural gas emissions from gas well venting during completions and workovers 

involving hydraulic fracturing using Equation W-10A or Equation W-10B of this section. 
Page 27 of 214 

This document showing the proposed amendments to subparts A and W is provided for informational 

puroposes only. We have taken steps to ensure the accuracy of this version, but it is not the official version. 

Equation W-10A applies to well venting when the flowback rate is measured from a specified 

number of example completions or workovers and Equation W-10B applies when the flowback 

vent or flare volume is measured for each completion or workover. Completion and workover 

activities are separated into two periods, an initial period when flowback is routed to open pits or 

tanks and a subsequent period when gas content is sufficient to route the flowback to a separator 

or when the gas content is sufficient to allow measurement by the devices specified in paragraph 

(g)(1) of this section, regardless of whether a separator is actually utilized. If you elect to use 

Equation W-10A of this section, you must follow the procedures specified in paragraph (g)(1) of 

this section. Emissions must be calculated separately for completions and workovers, for each 

sub-basin, and for each well type combination identified in paragraph (g)(2) of this section. You 

must calculate CH4 and CO2 volumetric and mass emissions as specified in paragraph (g)(3) of 

this section. If emissions from gas well venting during completions and workovers with 

hydraulic fracturing are routed to a flare, you must calculate CH4, CO2, and N2O annual 

emissions as specified in paragraph (g)(4) of this section. 

    

       

W

p

Es n Tp s FRM s PRs p EnFs p Tp i FRMi PRs p

1

, , , , , , 2 (Eq. W-10A) 

    

    

W

p

Es n FVs p EnFs p Tp i FRp i

1

, , , , , 2 (Eq. W-10B) 

Where: 

Es,n = Annual volumetric totalnatural gas emissions in standard cubic feet at 

standard conditions from gas well venting during completions or workovers 

following hydraulic fracturing for each sub-basin and well type (horizontal 

vs. vertical) combination. 

W = Total number of wells completed or worked over using hydraulic fracturing 

in a sub-basin and well type (horizontal vs. vertical) combination. 

Comment [EPA1]: Proposed Revised Equation. 

Comment [EPA2]: Proposed Revised Equation. 
Page 28 of 214 

This document showing the proposed amendments to subparts A and W is provided for informational 

puroposes only. We have taken steps to ensure the accuracy of this version, but it is not the official version. 

Tp,s = Cumulative amount of time of backflowflowback, after sufficient quantities 

of gas are present to enable separation, where gas vented or flared for the 

completion or workover, in hours, for each well, p, in a sub-basin and well 

type (horizontal vs. vertical) combination during the reporting year. This may 

include non-contiguous periods of venting or flaring. 

Tp,i = Cumulative amount of time of flowback to open tanks/pits, from when gas is 

first detected until sufficient quantities of gas are present to enable 

separation, for the completion or workover, in hours, for each well, p, in a 

sub-basin and well type combination during the reporting year. This may 

include non-contiguous periods of routing to open tanks/pits.

FRMs = Ratio of average flowback, during the period when sufficient quantities of 

gas are present to enable separation, of well completions and workovers from 

hydraulic fracturing to 30-day production rate from Equation W-12.for the 

sub-basin and well type combination, calculated using procedures specified 

in paragraph (g)(1)(iii) of this section, expressed in standard cubic feet per 

hour. 

PRs,p = First 30-day average production flow rate in standard cubic feet per hour of 

each well p, as required in paragraph (g)(1) of this section.

FRMi = Ratio of initial flowback rate during well completions and workovers from 

hydraulic fracturing to 30-day production rate for the sub-basin and well type 

combination, calculated using procedures specified in paragraph (g)(1)(iv) of 

this section, expressed in standard cubic feet per hour, for the period of flow 

to open tanks/pits. 

PRs,p = Average production flow rate during the first 30 days of production after 

completions of newly drilled gas wells or gas well workovers using hydraulic 

fracturing in standard cubic feet per hour of each well p, that was measured in 

the sub-basin and well type combination. 

EnFs,p = Volume of CO2 or N2 injected gas in cubic feet at standard conditions that 

was injected into the reservoir during an energized fracture job for each well,

p, as determined by using an appropriate meter according to methods 

described in § 98.234(b), or by using receipts of gas purchases that are used 

for the energized fracture job. Convert to standard conditions using paragraph 

(t) of this section. If the fracture process did not inject gas into the reservoir, 

then EnFs,p is 0. If or if the injected gas is CO2 then EnFs,p is 0. 

SGs,p = Volume of natural gas in cubic feet at standard conditions that was recovered 

into a flow-line for well p as per paragraph (g)(3) of this section. This 

parameter includes any natural gas that is injected into the well for clean-up. 

If no gas was recovered, SGs,p is 0.

FVs,p = Flow volume vented or flared of each well (, p), in standard cubic feet 

measured using a recording flow meter (digital or analog) on the vent line to 
Page 29 of 214 

This document showing the proposed amendments to subparts A and W is provided for informational 

puroposes only. We have taken steps to ensure the accuracy of this version, but it is not the official version. 

measure flowback during the separation period of the completion or 

workover according to methods set forth in §98.234(b). 

FRp,i = Flow rate vented or flared of each well, p, in standard cubic feet measured 

using a recording flow meter (digital or analog) on the vent line to measure 

the flowback, at the beginning of the period of time when sufficient quantities 

of gas are present to enable separation, of the completion or workover 

according to methods set forth in §98.234(b). 

(1) The average flow rate for flowback during well completions and workovers from 

hydraulic fracturing shall be determined using measurement(s) for Calculation Methodology 1 or 

calculation(s) for Calculation Methodology 2 described in this paragraph (g)(1) of this section. If 

Equation W-10A is used, the number of measurements or calculations shall be determined per 

sub-basin and well type (horizontal or vertical) as follows: at least one measurement or 

calculation for less than or equal to 25 completions or workovers; at least two measurements or 

calculations for 26 to 50 completions or workovers; at least three measurements or calculations

for 51 to 100 completions or workovers; at least four measurements or calculations for 101 to 

250 completions or workovers; and at least five measurements or calculations for greater than 

250 completions or workovers.If you elect to use Equation W-10A of this section, you must use 

Calculation Method 1 as specified in paragraph (g)(1)(i) of this section, or Calculation Method 2 

as specified in paragraph (g)(1)(ii) of this section, to determine the value of FRMs and FRMi. 

These values must be based on the flow rate for flowback, once sufficient gas is present to enable 

separation. The number of measurements or calculations required to estimate FRMs and FRMi

must be determined individually for completions and workovers per sub-basin and well type as 

follows: complete measurements or calculations for a least one completion or workover for less 

than or equal to 25 completions or workovers for each well type within a sub-basin; complete 

measurements or calculations for at least two completions or workovers for 26 to 50 completions 
Page 30 of 214 

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puroposes only. We have taken steps to ensure the accuracy of this version, but it is not the official version. 

or workovers for each sub-basin and well type combination; complete measurements or 

calculations for at least three completions or workovers for 51 to 100 completions or workovers 

for each sub-basin and well type combination; complete measurements or calculations for at least 

four completions or workovers for 101 to 250 completions or workovers for each sub-basin and 

well type combination; and complete measurements or calculations for at least five completions 

or workovers for greater than 250 completions or workovers for each sub-basin and well type 

combination.

(i) Calculation Methodology 1. When using Equation W-10A, for each measured well 

completion(s) in each gas producing sub-basin category and well type (horizontal or vertical) 

combination and for each measured well workover(s) in each gas producing sub-basin category 

and well type (horizontal or vertical) combination, a recording flow meter (digital or analog) 

shall be installed on the vent line, ahead of a flare or vent if used, to measure the backflow rate

according to methods set forth in §98.234(b).You must use Equation W-12A as specified in 

paragraph (g)(1)(iii) of this section to determine the value of FRMs. You must use Equation W12B as specified in paragraph (g)(1)(iv) of this section to determine the value of FRMi. The 

procedures specified in paragraphs (g)(1)(v) and (g)(1)(vi) also apply. When making flowback 

measurements for use in Equations W-12A and W-12B of this section, you must use a recording 

flow meter (digital or analog) installed on the vent line, ahead of a flare or vent, to measure the 

flowback rates in units of standard cubic feet per hour according to methods set forth in § 

98.234(b).

(ii) Calculation Methodology 2. When using Equation W-10A, for each calculated 

horizontal well completion and each calculated vertical well completion in each gas producing 

sub-basin category and for each calculated well horizontal workover and for each calculated 
Page 31 of 214 

This document showing the proposed amendments to subparts A and W is provided for informational 

puroposes only. We have taken steps to ensure the accuracy of this version, but it is not the official version. 

vertical well workover in each gas producing sub-basin category, record the well flowing 

pressure upstream (and downstream in subsonic flow) of a well choke according to methods set 

forth in §98.234(b) to calculate the well backflow during well completions and workovers from 

hydraulic fracturing. Calculate emissions using Equation W-11A of this section for subsonic 

flow or Equation W-11B of this section for sonic flow. Use best engineering estimate based on 

best available data along with Equation W-11C of this section to determine whether the 

predominant flow is sonic or subsonic. If the value of R in Equation W-11C is greater than or 

equal to 2, then flow is sonic; otherwise, flow is subsonic:You must use Equation W-12A as 

specified in paragraph (g)(1)(iii) of this section to determine the value of FRMs. You must use 

Equation W-12B as specified in paragraph (g)(1)(iv) of this section to determine the value of 

FRMi. The procedures specified in paragraphs (g)(1)(v) and (g)(1)(vi) also apply. When 

calculating the flowback rates for use in Equations W-12A and W-12B of this section based on 

well parameters, you must record the well flowing pressure immediately upstream (and 

immediately downstream in subsonic flow) of a well choke according to methods set forth in § 

98.234(b) to calculate the well flowback. The upstream pressure must be surface pressure and 

reservoir pressure cannot be assumed. The downstream pressure must be measured after the 

choke and atmospheric pressure cannot be assumed. Calculate flowback rate using Equation W11A of this section for subsonic flow or Equation W-11B of this section for sonic flow. You 

must use best engineering estimates based on best available data along with Equation W-11C of 

this section to determine whether the predominant flow is sonic or subsonic. If the value of R in 

Equation W-11C of this section is greater than or equal to 2, then flow is sonic; otherwise, flow 

is subsonic. Convert calculated FRa values shall be converted from actual conditions upstream of 
Page 32 of 214 

This document showing the proposed amendments to subparts A and W is provided for informational 

puroposes only. We have taken steps to ensure the accuracy of this version, but it is not the official version. 

the restriction orifice to standard conditions (FRs,p and FRi,p) for use in Equations W-12A and W12B of this section using Equation W-33 in paragraph (t) of this section.































  













  

1.758

1

2

1.515

1

5 2 1.27 10 * * 3430* * P

P

P

P FRa A Tu (Eq. W-11A) 

Where: 

FRa = Average flowFlowback rate in actual cubic feet per hour, under actual 

subsonic flow conditions. 

A = Cross sectional open area of the restriction orifice (m2

). 

P1 = Upstream pressurePressure immediately upstream of the choke (psia). 

Tu = Upstream temperatureTemperature immediately upstream of the choke

(degrees Kelvin). 

P2 = Downstream pressurePressure immediately downstream of the choke (psia). 

3430 = Constant with units of m2 /(sec2 * K). 

1.27*105

 = Conversion from m3 /second to ft3/hour. 

FRa A 08*Tu 1.27 10 * * 187. 5   (Eq. W-11B) 

Where: 

FRa = Average flowFlowback rate in actual cubic feet per hour, under actual sonic 

flow conditions. 

A = Cross sectional open area of the restriction orifice (m2

). 

Tu = Upstream temperatureTemperature immediately upstream of the choke

(degrees Kelvin). 

187.08 = Constant with units of m2

 /(sec2 * K). 

1.27*105

 = Conversion from m3 /second to ft3 /hour. 

2

1

P R  P

 (Eq. W-11C) 

Where: 
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R = Pressure ratio.

P1 = Pressure immediately upstream of the restriction orifice in pounds per square 

inch absolute.choke (psia).

P2 = Pressure immediately downstream of the restriction orifice in pounds per 

square inch absolute. choke (psia).

(iii) For Equation W-10A, the ratio of backflow rate during well completions and 

workovers from hydraulic fracturing to 30-day production rate is calculated of this section, 

calculate FRMs using Equation W-12A of this section. 







  N

p

s p

N

p

s p

s

PR

FR

FRM

1

,

1

,

 (Eq. W-12A) 

Where: 

FRMs = Ratio of average flowback rate during, during the period of time when 

sufficient quantities of gas are present to enable separation, of well 

completions and workovers from hydraulic fracturing to 30-day production 

rate for each sub-basin and well type combination. 

FRs,p = Measured average flowback rate from Calculation Methodology 1 described 

in paragraph (g)(1)(i) of this section or calculated flowaverage flowback rate 

from Calculation Methodology 2 described in paragraph (g)(1)(ii) of this 

section, during the separation period in standard cubic feet per hour for 

well(s) p for each sub-basin and well type (horizontal or vertical) 

combination. MeasuredConvert measured and calculated FRa values shall be 

converted from actual conditions upstream of the restriction orifice (FRa) to 

standard conditions (FRs,p) for each well p using Equation W-33 in paragraph 

(t) of this section. You may not use flow volume as used in Equation W-10B 

converted to a flow rate for this parameter. 

PRs,p = First 30-dayAverage production flow rate during the first 30 days of

production rateafter completions of newly drilled gas wells or gas well 

workovers using hydraulic fracturing, in standard cubic feet per hour for each 

well, p, that was measured in the sub-basin and well type combination. 

N = Number of measured or calculated well completions or workovers using 

hydraulic fracturing in a sub-basin and well type combination. 
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(iv) For Equation W-10A of this section, calculate FRMi using Equation W-12B of this 

section. 

,

1

,

1

N

i p

p

i N

s p

p

FR

FRM

PR











 (Eq. W-12B) 

Where: 

FRMi = Ratio of flowback gas rate while flowing to open tanks/pits during well 

completions and workovers from hydraulic fracturing to 30-day production 

rate. 

FRi,p = Initial measured gas flowback rate from Calculation Method 1 described in 

paragraph (g)(1)(i) of this section or initial calculated flow rate from 

Calculation Method 2 described in paragraph (g)(1)(ii) of this section in 

standard cubic feet per hour for well(s), p, for each sub-basin and well type 

combination. Measured and calculated FRi,p values must be based on flow 

conditions at the beginning of the separation period and must be expressed at 

standard conditions. 

PRs,p = Average production flow rate during the first 30-days of production after 

completions of newly drilled gas wells or gas well workovers using hydraulic 

fracturing, in standard cubic feet per hour of each well, p, that was measured 

in the sub-basin and well type combination. 

N = Number of measured or calculated well completions or workovers using 

hydraulic fracturing in a sub-basin and well type combination. 

(ivv) For Equation W-10A of this section, the ratio of backflowflowback rate during well 

completions and workovers from hydraulic fracturing to 30-day production rate for horizontal 

and vertical wells are applied to all horizontal and vertical well completions in the gas producing 

sub-basin and well type combination and to all horizontal and vertical well workovers, 

respectively, in the gas producing sub-basin and well type combination for the total number of 

hours of backflowflowback and for the first 30 day average production rate for each of these 

wells. 
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(vvi) For Equation W-10A,12A and W-12B of this section, calculate new flowback rates 

for horizontal and vertical gas well completions and horizontal and vertical gas well workovers 

in each sub-basin category shall be calculated once every two years starting in the first calendar 

year of data collection. 

(2) The volume of CO2 or N2 injected into the well reservoir during energized hydraulic 

fractures will be measured using an appropriate meter as described in 98.234(b) or using receipts 

of gas purchases that are used for the energized fracture job.For paragraphs (g) introductory text 

and (g)(1) of this section, measurements and calculations are completed separately for workovers 

and completions per sub-basin and well type combination. A well type combination is a unique 

combination of the parameters listed in paragraphs (g)(2)(i) through (g)(2)(iii) of this section. 

(i) Calculate gas volume at standard conditions using calculations in paragraph (t) of this 

section.

(i) Vertical or horizontal (directional drilling). 

(ii) [Reserved]With flaring or without flaring.

(iii) Reduced emission completion/workover or not reduced emission 

completion/workover. 

(3) Determine if the backflow gas from the well completion or workover from hydraulic 

fracturing is recovered with purpose designed equipment that separates natural gas from the 

backflow, and sends this natural gas to a flow-line (e.g.,reduced emissions completion or 

workovers).

(i) Use the factor SGs,P in Equation W-10A of this section, to adjust the emissions 

estimated in paragraphs (g)(1) through (g)(4) of this section by the magnitude of emissions 
Page 36 of 214 

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captured using purpose designed equipment that separates saleable gas from the flowback as 

determined by engineering estimate based on best available data.

(iii) Calculate gas volume at standard conditions using calculations in paragraph (t) of 

this section.

 (4) Calculate Bboth CH4 and CO2 volumetric and mass emissions shall be calculated 

from total natural gas volumetric total emissions using calculations in paragraphs (u) and (v) of 

this section. 

(54) Calculate annual emissions from gas well venting during well completions and 

workovers from hydraulic fracturing to flares as follows:where all or a portion of the gas is flared 

as specified in paragraphs (g)(4)(i) and (g)(4)(ii) of this section.

(i) Use the volumetric total gas well venting volume natural gas emissions vented to the 

atmosphere during well completions and workovers as determined in paragraph (g) of this 

section to calculate volumetric and mass emissions using paragraphs (u) and (v) of this section. 

(ii) Use the calculation methodology of flare stacks in paragraph (n) of this section to 

determine adjust emissions for the portion of gas well ventingflared during well completions and 

workovers using hydraulic fracturing emissions from the flare. This adjustment to emissions 

from completions using flaring, versus completions without flaring, accounts for the conversion 

of CH4 to CO2 in the flare and for the formation on N2O during flaring. 

(h) Gas well venting during completions and workovers without hydraulic fracturing. 

Calculate CH4, CO2 and N2O annual volumetric natural gas emissions from each gas well 

venting during well completions and workovers not involvingwithout hydraulic fracturing using 

Equation W-13A of this section:. Calculate annual volumetric natural gas emissions from each 

gas well venting during completions without hydraulic fracturing using Equation W-13B of this 
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section. You must convert annual volumetric natural gas emissions to CH4 and CO2 volumetric 

and mass emissions as specified in paragraph (h)(1) of this section. If emissions from gas well 

venting during completions and workovers without hydraulic fracturing are routed to a flare, you 

must calculate CH4, CO2, and N2O annual emissions as specified in paragraph (h)(2) of this 

section.

Es,wo  Nwo *EFwo (Eq. W-13A) 

p

f

p

Es p Vp * T 1

, 

 (Eq. W-13B) 

Where: 

Es,nwo = Annual volumetric natural gas emissions in standard cubic feet from gas well 

venting during well completions and workovers without hydraulic fracturing. 

Nwo = Number of workovers per sub-basin category that flare gas or vent gas to the 

atmosphere and do not involve hydraulic fracturing in the reporting year. 

EFwo = Emission Ffactor for non-hydraulic fracture well workover venting in 

standard cubic feet per workover. EFwo =Use 3,114 standard cubic feet 

natural gas per well workover without hydraulic fracturing. 

Es,p = Annual volumetric natural gas emissions in standard cubic feet from gas well 

venting during well completions without hydraulic fracturing.

p = Well completions 1 through f in a sub-basin. 

f = Total number of well completions without hydraulic fracturing in a sub-basin 

category. 

Vp = Average daily gas production rate in standard cubic feet per hour for each 

well, p, undergoing completion without hydraulic fracturing, p. This is the 

total annual gas production volume divided by total number of hours the 

wells produced to the flow-line. For completed wells that have not 

established a production rate, you may use the average flow rate from the 

first 30 days of production. In the event that the well is completed less than 

30 days from the end of the calendar year, the first 30 days of the production 

straddling the current and following calendar years shall be used. 

Comment [EPA3]: Proposed Revised Equation. 

Comment [EPA4]: Proposed New Equation. 
Page 38 of 214 

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Tp = Time that gas is vented to either the atmosphere or a flare for each well, p, 

undergoing completion without hydraulic fracturing, p, was venting in hours 

during the year. 

(1) Volumetric emissions for Calculate both CH4 and CO2 shall be calculated volumetric 

emissions from volumetric natural gas volumetric emissions using calculations in paragraph (u) 

of this section. Mass emissions for Calculate both CH4 and CO2 shall be calculatedmass 

emissions from volumetric natural gas emissions vented to atmosphere using calculations in 

paragraphs (v) of this section. 

(2) Calculate annual emissions of CH4, CO2, and N2O from gas well venting to flares 

during well completions and workovers not involving hydraulic fracturing to flares as follows:as 

specified in paragraphs (h)(2)(i) and (h)(2)(ii) of this section.

(i) Use the gas well venting volume and gas composition during well completions and 

workovers that are flared as determined using the methods specified in paragraphs (h) and (h)(1)

of this section. 

(ii) Use the calculation methodology of flare stacks in paragraph (n) of this section to 

determine emissions from the flare for gas well venting to a flare during well completions and 

workovers emissions without hydraulic fracturing from the flare. 

(i) Blowdown vent stacks. Calculate CO2 and CH4 blowdown vent stack emissions from 

depressurizingthe depressurization of equipment(s) to reduce system pressure for planned or 

emergency shutdowns resulting from human intervention or to take equipment out of service for 

maintenance (excludingas specified in either paragraph (i)(2) or (i)(3) of this section. Equipment 

with a unique physical volume of less than 50 cubic feet as determined in paragraph (i)(1) of this 

section are not subject to the requirements in paragraphs (i)(2) through (i)(4) this section. The 

requirements in this paragraph (i) do not apply to blowdown vent stack emissions from
Page 39 of 214 

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depressurizing to a flare, over-pressure relief, operating pressure control venting and, blowdown 

of non-GHG gases;, and desiccant dehydrator blowdown venting before reloading is covered in 

paragraph (e)(5) of this section) as follows:. 

(1) Calculate theMethod for calculating unique physical volumes. You must calculate 

each unique physical volume (including pipelines, compressor case or cylinders, manifolds, 

suction bottles, discharge bottles, and vessels) between isolation valves determined, in cubic feet,

by using engineering estimates based on best available data. 

(2) If the unique physical volume between isolation valves is greater than or equal to 50 

cubic feet, retain logs of the number of blowdowns for each unique physical volume (including 

but not limited to compressors, vessels, pipelines, headers, fractionators, and tanks). Unique 

physical volumes smaller than 50 cubic feet are exempt from reporting under paragraph (i) of 

this section.

(3) Method for determining emissions from blowdown vent stacks according to 

equipment type. If you elect to determine emissions according to each equipment type, using 

unique physical volumes as calculated in paragraph (i)(1) of this section, you must calculate 

emissions as specified in paragraphs (i)(2)(i) through (i)(2)(iii) of this section for each equipment 

type. Equipment types must be grouped into the following seven categories: station piping, 

pipeline venting, compressors, scrubbers/strainers, pig launchers and receivers, emergency 

shutdowns, and all other blowdowns greater than or equal to 50 cubic feet. 

(i) Calculate the total annual ventingnatural gas emissions forfrom each unique 

volumesphysical volume that is blown down using either Equation W-14A or W-14B of this 

section. 
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 

  ,

459.67 * * 459.67

s a

s n

a sa

T P

E N V VC

T PZ

          

    

 (Eq. W-14A) 

Where: 

Es,n = Annual natural gas venting emissions at standard conditions from blowdowns

each unique physical volume that is blown down, in cubic feet. 

N = Number of occurrences of blowdowns for each unique physical volume in the 

calendar year. You must retain logs documenting the number of occurrences 

of blowdowns for each unique physical volume in the calendar year. 

V = Unique physical volume (including pipelines, compressors and vessels) 

between isolation valves, in cubic feet, as calculated in paragraph (i)(1) of 

this section. 

C = Purge factor that is 1 if the unique physical volume is not purged, or zero0 if 

the unique physical volume is purged using non-GHG gases. 

Ts = Temperature at standard conditions (60 °F). 

Ta = Temperature at actual conditions in the unique physical volume (°F). 

Ps = Absolute pressure at standard conditions (14.7 psia). 

Pa = Absolute pressure at actual conditions in the unique physical volume (psia). 

Za = Compressibility factor at actual conditions for natural gas. You may use 1 if 

the temperature is above -10 degrees Fahrenheit and pressure is below 5 

atmospheres, or if the compressibility factor at the actual temperature and 

pressure is 0.98 or greater. 

  

 ,, ,,

,

1 ,

459.67

459.67

N s ab p ae p

p s n

p ap s a

TP P

E V  T PZ

          

    

 (Eq. W-14B) 

Where: 

Es,n = Annual natural gas venting emissions at standard conditions from 

blowdownseach unique physical volume that is blown down, in cubic feet. 

p = Individual occurrence of blowdown for the same unique physical volume. 

N = Number of occurrences of blowdowns for each unique physical volume in the 

calendar year. You must retain logs documenting the number of occurrences 

of blowdowns for each unique physical volume in the calendar year.

Comment [EPA5]: Proposed Revised Equation. 

Comment [EPA6]: Proposed Revised Equation. 
Page 41 of 214 

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Vp = TotalUnique physical volume (including pipelines, compressors and vessels) 

between isolation valves, in cubic feet, for each blowdown “p.” 

Ts = Temperature at standard conditions (60 °F). 

Ta,p = Temperature at actual conditions in the unique physical volume ( °F) for each 

blowdown “p”. 

Ps = Absolute pressure at standard conditions (14.7 psia). 

Pa,b,p = Absolute pressure at actual conditions in the unique physical volume (psia) at 

the beginning of the blowdown “p”. 

Pa,e,p = Absolute pressure at actual conditions in the unique physical volume (psia) at 

the end of the blowdown “p”; 0 if blowdown volume is purged using nonGHG gases. 

Za = Compressibility factor at actual conditions for natural gas. You may use 1 if 

the temperature is above -10 degrees Fahrenheit and pressure is below 5 

atmospheres, or if the compressibility factor at the actual temperature and 

pressure is 0.98 or greater. 

(ii) Calculate the annual natural gas emissions, in cubic feet, from each equipment type 

by summing Es,n, as calculated in either Equation W-14A or Equation W-14B of this subpart, for 

all unique physical volumes associated with the equipment type. 

(iii) Calculate total annual CH4 and CO2 volumetric and mass emissions from each 

equipment type by using the annual natural gas emission value calculated in paragraph (i)(2)(ii) 

of this section for the equipment type and the calculation method specified in paragraph (i)(4) of 

this section. 

(3) Method for determining emissions from blowdown vent stacks using a flow meter. In 

lieu of determining emissions from blowdown vent stacks using unique physical volumes as 

specified in paragraphs (i)(1) and (i)(2) of this section, you may use a flow meter and measure 

blowdown vent stack emissions. If you choose to use this method, you must measure the natural 

gas emissions from the blowdown(s) at the facility using a flow meter according to methods in 
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§98.234(b), and calculate annual CH4 and CO2 volumetric and mass emissions measured by the 

meters according to paragraph (i)(4) of this section. 

(4) Method for converting from natural gas emissions to GHG volumetric and mass 

emissions. Calculate both CH4 and CO2 volumetric and mass emissions using calculationsthe 

methods specified in paragraphs (u) and (v) of this section. 

(j) Onshore production storage tanks. Calculate CH4, CO2, and N2O (when flared) 

emissions from atmospheric pressure fixed roof storage tanks receiving hydrocarbon produced 

liquids from onshore petroleum and natural gas production facilities (including stationary liquid 

storage not owned or operated by the reporter), calculate annual CH4 and CO2 emissions using 

any of the calculation methodologies described in this paragraph (j).as specified in this paragraph 

(j). For wells flowing to gas-liquid separators with annual average daily throughput of oil greater 

than or equal to 10 barrels per day, calculate annual CH4 and CO2 using Calculation Method 1 or 

2 as specified in paragraphs (j)(1) and (j)(2) of this section. For wells flowing directly to 

atmospheric storage tanks without passing through a wellhead separator with throughput greater 

than 10 barrels per day, calculate annual CH4 and CO2 emissions using Calculation Method 2 as 

specified in paragraph (j)(2) of this section. For wells flowing to gas-liquid separators or directly 

to atmospheric storage tanks with throughput less than 10 barrels per day, use Calculation 

Method 3 as specified in paragraphs (j)(3) of this section. You must also calculate emissions that 

may have occurred due to dump valves not closing properly using the method specified in 

paragraph (j)(6) of this section. If emissions from atmospheric pressure fixed roof storage tanks 

are routed to a vapor recovery system, you must adjust the emissions downward according to 

paragraph (j)(4) of this section. If emissions from atmospheric pressure fixed roof storage tanks 
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are routed to a flare, you must calculate CH4, CO2, and N2O annual emissions as specified in 

paragraph (j)(5) of this section.

(1) Calculation Methodology 1. For separators with annual average daily throughput of 

oil greater than or equal to 10 barrels per day. Calculate annual CH4 and CO2 emissions from 

onshore production storage tanks using operating conditions in the last wellhead gas-liquid 

separator before liquid transfer to storage tanks. Calculate flashing emissions with a software 

program, such as AspenTech HYSYS® or API 4697 E&P Tank, that uses the Peng-Robinson 

equation of state, models flashing emissions, and speciates CH4 and CO2 emissions that will 

result when the oil from the separator enters an atmospheric pressure storage tank. A minimum 

of theThe following parameters must be determined for typical operating conditions over the 

year by engineering estimate and process knowledge based on best available data, and must be 

used at a minimum to characterize emissions from liquid transferred to tanks.:

(i) Separator temperature. 

(ii) Separator pressure. 

(iii) Sales oil or stabilized oil API gravity. 

(iv) Sales oil or stabilized oil production rate. 

(v) Ambient air temperature. 

(vi) Ambient air pressure. 

(vii) Separator oil composition and Reid vapor pressure. If this data is not available, 

determine these parameters by uselecting one of the methods described under paragraphin 

paragraphs (j)(1) ()(vii)(A) through (j)(1)(vii)(C) of this section. 
Page 44 of 214 

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(A) If separator oil composition and Reid vapor pressure default data are provided with 

the software program, select the default values that most closely match your separator pressure 

first, and API gravity secondarily. 

(B) If separator oil composition and Reid vapor pressure data are available through your 

previous analysis, select the latest available analysis that is representative of produced crude oil 

or condensate from the sub-basin category. 

(C) Analyze a representative sample of separator oil in each sub-basin category for oil 

composition and Reid vapor pressure using an appropriate standard method published by a 

consensus-based standards organization. 

(2) Calculation Methodology 2. Calculate annual CH4 and CO2 emissions from onshore 

production storage tanks for wellhead gas-liquid separators with annual average daily throughput 

of oil greater than or equal to 10 barrels per day by assuming that all of the CH4 and CO2 in 

solution at separator temperature and pressure is emitted from oil sent to storage tanks., using 

either of the methods in paragraphs (j)(2)(i) or (j)(2)(ii) of this section. You may use an 

appropriate standard method published by a consensus-based standards organization if such a 

method exists or you may use an industry standard practice as described in §98.234(b) to sample 

and analyze separator oil composition at separator pressure and temperature. 

(3) Calculation Methodology 3. For wells with annual average daily oil production 

greater than or equal to 10 barrels per day that flow directly to atmospheric storage tanks without 

passing through a wellhead separator, calculate annual CH4 and CO2 emissions by either of the 

methods in paragraph (j)(3) of this section:

(i) If well production oil and gas compositions are available through your previous 

analysis, select the latest available analysis that is representative of produced oil and gas from the 
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sub-basin category and assume all of the CH4 and CO2 in both oil and gas are emitted from the 

tank. 

(ii) If well production oil and gas compositions are not available, use default oil and gas 

compositions in software programs, such as API 4697 E&P Tank, that most closely match your 

well production gas/oil ratio and API gravity and assume all of the CH4 and CO2 in both oil and 

gas are emitted from the tank. 

(43) Calculation Methodology 4. For wells with annual average daily oil production 

greater than or equal to 10 barrels per day that flow to a separator not at the well pad, calculate 

annualMethod 3. Calculate CH4 and CO2 emissions by either of the methods in paragraph (j)(4) 

of this section:

(i) If well production oil and gas compositions are available through your previous 

analysis, select the latest available analysis that is representative of oil at separator pressure 

determined by best available data and assume all of the CH4and CO2 in the oil is emitted from 

the tank.

(ii) If well production oil composition is not available, use default oil composition in 

software programs, such as API 4697 E&P Tank, that most closely match your well production 

API gravity and pressure in the off-well pad separator determined by best available data. Assume 

all of the CH4 and CO2 in the oil phase is emitted from the tank.

(5) Calculation Methodology 5. For well pad gas-liquid separators and for wells flowing 

off a well pad without passing through a gas-liquid separator with annual average daily 

throughput of oil less than 10 barrels per day useusing Equation W-15 of this section: 

Es,i EFi *Count *1000 (Eq. W-15) 
Page 46 of 214 

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Where: 

Es,i = Annual total volumetric GHG emissions (either CO2 or CH4 ) at standard 

conditions in cubic feet. 

EFi = Population emission factor for separators or wells in thousand standard cubic 

feet per separator or well 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 or wells with annual average daily throughput less 

than 10 barrels per day. Count only separators or wells that feed oil directly 

to the storage tank. 

1,000 = Conversion from thousand standard cubic feet to standard cubic feet. 

(64) Determine if the storage tank receiving your separator oil has a vapor recovery 

system. 

(i) Adjust the emissions estimated in paragraphs (j)(1) through (j)(53) of this section 

downward by the magnitude of emissions recovered using a vapor recovery system as 

determined by engineering estimate based on best available data. 

(ii) [Reserved] 

(57) Determine if the storage tank receiving your separator oil is sent to flare(s). 

(i) Use your separator flash gas volume and gas composition as determined in this 

section. 

(ii) Use the calculation methodology of flare stacks in paragraph (n) of this section to 

determine your contribution to storage tank emissions from the flare. 

(86) Calculate emissions from occurrences of well pad gas-liquid separator liquid dump 

valves not closing during the calendar year by using Equation W-16 of this section. 





 



  n

n

s i o n T E E CF * 8760

* , , (Eq. W-16) 
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Where: 

Es,i,o = Annual total volumetric GHG emissions at standard conditions from each 

storage tank in cubic feet that resulted from the dump valve on the gas-liquid 

separator not closing properly. 

En = Storage tank emissions as determined in Calculation Methodologies 1, 2, or 

43 in paragraphs (j)(1), (j)(2), and (j)(43) of this section (with wellhead 

separators) in standard cubic feet per year. 

Tn = Total time thea dump valve is not closing properly in the calendar year in 

hours. Estimate Tn is estimated bybased on maintenance or, operations

records (records) such that when a record shows the valve to be open 

improperly, it is assumed, or routine well pad inspections that indicate the 

period of time when the valve was malfunctioning in open or partially open 

position. for the entire time period preceding the record starting at either the 

beginning of the calendar year or the previous record showing it closed 

properly within the calendar year. If a subsequent record shows it is closing 

properly, then assume from that time forward the valve closed properly until 

either the next record of it not closing properly or, if there is no subsequent 

record, the end of the calendar year.

CFn = Correction factor for tank emissions for time period Tn is 32.87 for crude oil 

production. Correction factor for tank emissions for time period Tn is 54.37 

for gas condensate production. Correction factor for tank emissions for time 

period Tn is 1.0 for periods when the dump valve is closed.

8,760 = Conversion to hourly emissions. 

(97) Calculate both CH4 and CO2 mass emissions from volumetric natural gas volumetric

emissions using calculations in paragraph (v) of this section. 

(k) Transmission storage tanks. For vent stacks connected to one or more transmission 

condensate storage tanks, either water or hydrocarbon, without vapor recovery, in onshore 

natural gas transmission compression, calculate CH4, and CO2 and N2O annual emissions from 

compressor scrubber dump valve leakage as follows:specified in paragraphs (k)(1) through (k)(3) 

of this section. If emissions from compressor scrubber dump valve leakage are routed to a flare, 

you must calculate CH4, CO2, and N2O annual emissions as specified in paragraph (k)(4) of this 

section.
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(1) Except as specified in paragraph (k)(1)(iv) of this section, you must Mmonitor the 

tank vapor vent stack annually for emissions using one of the methods specified in paragraphs 

(k)(1)(i) through (k)(1)(iii) of this section. 

(i) Use an optical gas imaging instrument according to methods set forth in §

98.234(a)(1) or by directly measuring). 

(ii) Measure the tank vent directly using a flow meter or high volume sampler according 

to methods in § 98.234(b) throughor (d) for a duration of 5 minutes, or. 

(iii) Measure the tank vent using a calibrated bag according to methods in § 98.234(b). Or 

youc) for a duration of 5 minutes or until the bag is full, whichever is shorter. 

(iv) You may annually monitor leakage through compressor scrubber dump valve(s) into 

the tank using an acoustic leak detection device according to methods set forth in §98.234(a)(5). 

(2) If the tank vapors from the vent stack are continuous for 5 minutes, or the acoustic 

leak detection device detects a leak, then you must use one of the following two methods in 

either paragraph (k)(2)(i) or (k)(2)(ii) of this section and the requirements specified in paragraphs 

(k)(2)(iii) and (k)(2)(iv) of this section to quantify annual emissions:.

(i) Use a flow meter, such as a turbine meter, calibrated bag, or high flowvolume sampler 

to estimate tank vapor volumes from the vent stack according to methods set forth in §98.234(b) 

through (d). If you do not have a continuous flow measurement device, you may install a flow 

measuring device on the tank vapor vent stack. If the vent is directly measured for five minutes 

under paragraph §98.233(k)(1)(ii) or (k)(1)(iii) of this section to detect continuous leakage, this 

serves as the measurement. 

(ii) Use an acoustic leak detection device on each scrubber dump valve connected to the 

tank according to the method set forth in §98.234(a)(5). 
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(iii) Use the appropriate gas composition in paragraph (u)(2)(iii) of this section. 

(iv) Calculate GHGCH4 and CO2 volumetric and mass emissions at standard conditions 

using calculations in paragraphs (t), (u), and (v) of this section, as applicable to the monitoring 

equipment used. 

(3) If the leaking dump valve(s) is fixed following leak detection, the annual emissions 

shall be calculated from the beginning of the calendar year to the time the valve(s) is repaired. If 

a leaking dump valve is identified, the leak must be counted as having occurred since the 

beginning of the calendar year, or from the previous test that did not detect leaking in the same 

calendar year. If the leaking dump valve is fixed following leak detection, the leak duration will 

end upon being repaired. If a leaking dump valve is identified and not repaired, the leak must be 

counted as having occurred through the rest of the calendar year.

(4) Calculate annual emissions from storage tanks to flares as follows:specified in 

paragraphs (k)(4)(i) and (k)(4)(ii) of this section.

(i) Use the storage tank emissions volume and gas composition as determined in 

paragraphs (k)(1) through (k)(3) of this section. 

(ii) Use the calculation methodology of flare stacks in paragraph (n) of this section to 

determine storage tank emissions sent to a flare. 

(l) Well testing venting and flaring. Calculate CH4, and CO2 and N2O (when 

flared)annual emissions from well testing venting and flaring emissions as follows:specified in 

paragraphs (l)(1) through (l)(5) of this section. If emissions from well testing venting are routed 

to a flare, you must calculate CH4, CO2, and N2O annual emissions as specified in paragraph 

(l)(6) of this section.
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(1) Determine the gas to oil ratio (GOR) of the hydrocarbon production from oil well(s) 

tested. Determine the production rate from gas well(s) tested. 

(2) If GOR cannot be determined from your available data, then you must measure 

quantities reported in this section according to one of the two procedures specified in paragraph 

(l)(2)(i) or (l)(2)(ii) of this section to determine GOR:.

(i) You may use an appropriate standard method published by a consensus-based 

standards organization if such a method exists. 

(ii) Or youYou may use an industry standard practice as described in §98.234(b). 

(3) Estimate venting emissions using Equation W-17A (for oil wells) or Equation W-17B

(for gas wells) of this section. 

Ea,n  GOR * FR*D (Eq. W-17A) 

Ea,n  PR*D (Eq. W-17B) 

Where: 

Ea,n = Annual volumetric natural gas emissions from well(s) testing in cubic feet 

under actual conditions. 

GOR = Gas to oil ratio in cubic feet of gas per barrel of oil; oil here refers to 

hydrocarbon liquids produced of all API gravities. 

FR = FlowAverage annual flow rate in barrels of oil per day for the oil well(s) 

being tested. 

PR = Average annual production rate in actual cubic feet per day for the gas well(s) 

being tested. 

D = Number of days during the calendar year, that the well(s) is tested. 

(4) Calculate natural gas volumetric emissions at standard conditions using calculations 

in paragraph (t) of this section. 
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(5) Calculate both CH4 and CO2 volumetric and mass emissions from volumetric natural 

gas volumetric emissions using calculations in paragraphs (u) and (v) of this section. 

(6) Calculate emissions from well testing to flaresif emissions are routed to a flare as 

follows:specified in paragraphs (l)(6)(i) and (l)(6)(ii) of this section.

(i) Use the well testing emissions volume and gas composition as determined in 

paragraphs (l)(1) through (34) of this section. 

(ii) Use the calculation methodology of flare stacks in paragraph (n) of this section to 

determine well testing emissions from the flare. 

(m) Associated gas venting and flaring. Calculate CH4, and CO2 and N2O (when 

flared)annual emissions from associated gas venting and flaring emissions not in conjunction 

with well testing (refer to paragraph (l): Well testing venting and flaring of this section) as 

follows:specified in paragraphs (m)(1) through (m)(4) of this section. If emissions from 

associated gas venting are routed to a flare, you must calculate CH4, CO2, and N2O annual 

emissions as specified in paragraph (m)(5) of this section.

(1) Determine the GOR of the hydrocarbon production from each well whose associated 

natural gas is vented or flared. If GOR from each well is not available, use the GOR from a 

cluster of wells in the same sub-basin category shall be used. 

(2) If GOR cannot be determined from your available data, then you must use one of the 

two procedures specified in paragraphs (m)(2)(i) or (m)(2)(ii) of this section to determine GOR:.

(i) You may use an appropriate standard method published by a consensus-based 

standards organization if such a method exists. 

(ii) Or youYou may use an industry standard practice as described in §98.234(b). 

(3) Estimate venting emissions using Equation W-18 of this section. 

Formatted: None
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, ,, , , 1 1

y x

sn pq pq p q p q q p

E GOR V SG ERE      (Eq. W-18) 

Where: 

EaEs,n = Annual volumetric natural gas emissions, at the facility level, from associated 

gas venting under actualat standard conditions, in cubic feet. 

GORp,q = Gas to oil ratio, for well p in sub-basin q, in standard cubic feet of gas per 

barrel of oil; oil here refers to hydrocarbon liquids produced of all API 

gravities. 

Vp,q = Volume of oil produced, for well p in sub-basin q, in barrels in the calendar 

year during time periods in which associated gas was vented or flared. 

SGp,q = Volume of associated gas sent to sales, for well p in sub-basin q, in standard 

cubic feet of gas in the calendar year during time periods in which associated 

gas was vented or flared. 

EREp,q = Emissions reported elsewhere, volume of associated gas for well p in subbasin q, in standard cubic feet, during time periods in which associated gas 

was vented or flared and for which emission source types of this section 

calculate and report emissions from the associated gas stream prior to venting 

or flaring of the associated gas (i.e., §98.233(j) for onshore production 

storage tanks).

x = Total number of wells in sub-basin that vent or flare associated gas. 

y = Total number of sub-basins in a basin that contain wells that vent or flare 

associated gas. 

(4) Calculate natural gas volumetric emissions at standard conditions using calculations 

in paragraph (t) of this section.

(54) Calculate both CH4 and CO2 volumetric and mass emissions from volumetric natural 

gas emissions using calculations in paragraphs (u) and (v) of this section. 

(65) Calculate emissions from associated natural gas to flaresif emissions are routed to a 

flare as follows:specified in paragraphs (m)(5)(i) and (m)(5)(ii) of this section.

(i) Use the associated natural gas volume and gas composition as determined in 

paragraph (m)(1) through (m)(4) of this section. 

Comment [EPA7]: Proposed Revised Equation. 
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(ii) Use the calculation methodology of flare stacks in paragraph (n) of this section to 

determine associated gas emissions from the flare. 

(n) Flare stack emissions. Calculate CO2, CH4, and N2O emissions from a flare stack as 

follows:specified in paragraphs (n)(1) through (n)(9) of this section.

(1) If you have a continuous flow measurement device on the flare, you must use the 

measured flow volumes to calculate the flare gas emissions. If all of the flare gas is not measured 

by the existing flow measurement device, then the flow not measured can be estimated using 

engineering calculations based on best available data or company records. If you do not have a 

continuous flow measurement device on the flare, you can install a flow measuring device on the 

flare or use engineering calculations based on process knowledge, company records, and best 

available data. 

(2) If you have a continuous gas composition analyzer on gas to the flare, you must use 

these compositions in calculating emissions. If you do not have a continuous gas composition 

analyzer on gas to the flare, you must use the appropriate gas compositions for each stream of 

hydrocarbons going to the flare as follows:specified in paragraphs (n)(2)(i) through (n)(2)(iii) of 

this section.

(i) For onshore natural gas production, determine natural gas compositionthe GHG mole 

fraction using paragraph (u)(2)(i) of this section. 

(ii) For onshore natural gas processing, when the stream going to flare is natural gas, use 

the GHG mole percentfraction in feed natural gas for all streams upstream of the de-methanizer 

or dew point control, and GHG mole percentfraction in facility specific residue gas to 

transmission pipeline systems for all emissions sources downstream of the de-methanizer 

overhead or dew point control for onshore natural gas processing facilities. For onshore natural 
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gas processing plants that solely fractionate a liquid stream, use the GHG mole percentfraction in 

feed natural gas liquid for all streams. 

(iii) For any applicable industry segment, when the stream going to the flare is a 

hydrocarbon product stream, such as methane, ethane, propane, butane, pentane-plus and mixed 

light hydrocarbons, then you may use a representative composition from the source for the 

stream determined by engineering calculation based on process knowledge and best available 

data. 

(3) Determine flare combustion efficiency from manufacturer. If not available, assume 

that flare combustion efficiency is 98 percent. 

(4) CalculateConvert GHG volumetric emissions to standard conditions using 

calculations in paragraph (t) of this section. 

(5) Calculate GHG volumetric emissions from flaring at actualstandard conditions using 

Equations W-19, W-20, and W-2120 of this section. 

Es CH s CH L U , 4 4   VX Z Z * *1 *        (Eq. W-19) 

  5

,2 2

1

s* *** * s CO CO s j j L

j

E VX VY R Z 



  (Eq. W-20) 

(Eq. W-21)

Where: 

Ea,CH4 (un-combusted)= Contribution of annual un-combusted CH4 emissions from flare 

stack in cubic feet, under actual conditions.

Ea,CO2 (un-combusted) = Contribution of annual un-combusted CO2 emissions from 

flare stack in cubic feet, under actual conditions.

Ea,CO2 (combusted) = Contribution of annual combusted CO2 emissions from flare stack in cubic 

feet, under actual conditions.

Comment [EPA8]: Proposed Revised Equation. 

Comment [EPA9]: Proposed: Equation W-20 

removed; Equation W-21 revised and renumbered to 

W-20. 
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Es,CH4 = Annual CH4 emissions from flare stack in cubic feet, at standard conditions. 

Es,CO2 = Annual CO2 emissions from flare stack in cubic feet, at standard conditions. 

VaVs = Volume of gas sent to flare in standard cubic feet, during the year as 

determined in paragraph (n)(1) of this section. 

η = Flare combustion efficiency, expressed as Ffraction of gas combusted by a 

burning flare (default is 0.98). For gas sent to an unlit flare, η is zero.

XCH4 = Mole fraction of CH4 in the feed gas to the flare as determined in paragraph 

(n)(2) of this section. 

XCO2 = Mole fraction of CO2 in the feed gas to the flare as determined in paragraph 

(n)(2) of this section. 

ZU = Fraction of the feed gas sent to an un-lit flare determined by engineering 

estimate and process knowledge based on best available data and operating 

records. 

XCO2 = Mole fraction of CO2 in gas to the flare.

ZL = Fraction of the feed gas sent to a burning flare (equal to 1- ZU). 

Yj = Mole fraction of gas hydrocarbon constituents j (such as methane, ethane, 

propane, butane, and pentanes-plus).) in the feed gas to the flare as 

determined in paragraph (n)(1) of this section.

Rj = Number of carbon atoms in the gas hydrocarbon constituent j in the feed gas 

to the flare: 1 for methane, 2 for ethane, 3 for propane, 4 for butane, and 5 for 

pentanes-plus). 

(5) Calculate GHG volumetric emissions at standard conditions using calculations in 

paragraph (t) of this section.

(6) Calculate both CH4 and CO2 mass emissions from volumetric CH4 and CO2 emissions 

using calculation in paragraph (v) of this section. 

(7) [Reserved]

(8) Calculate N2O emissions from flare stacks using Equation W-40 in paragraph (z) of 

this section. 

(98) If you operate and maintain a CEMS that has both a CO2 concentration monitor and 

volumetric flow rate monitor for the combustion gases from the flare, you must calculate only 
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CO2 emissions for the flare. You must follow the Tier 4 Calculation Methodology and all 

associated calculation, quality assurance, reporting, and recordkeeping requirements for Tier 4 in 

subpart C of this part (General Stationary Fuel Combustion Sources). If a CEMS is used to 

calculate flare stack emissions, the requirements specified in paragraphs (n)(1) through (n)(7) are 

not required. If a CO2 concentration monitor and volumetric flow rate monitor are not available, 

you may elect to install a CO2 concentration monitor and a volumetric flow rate monitor that 

comply with all of the requirements specified for the Tier 4 Calculation Methodology in subpart 

C of this part (General Stationary Fuel Combustion).

(109) The flare emissions determined under paragraph (n) of this section must be 

corrected for flare emissions calculated and reported under other paragraphs of this section to 

avoid double counting of these emissions. 

(o) Centrifugal compressor venting. Calculate CH4, CO2 and N2O (when flared) 

emissions from both wet seal and dry seal centrifugal compressor vents as follows:

(1) For each centrifugal compressor covered by §98.232 (d)(2), (e)(2), (f)(2), (g)(2), and 

(h)(2) you must conduct an annual measurement in the operating mode in which it is found. 

Measure emissions from all vents (including emissions manifolded to common vents) including 

wet seal oil degassing vents, unit isolation valve vents, and blowdown valve vents. Record 

emissions from the following vent types in the specified compressor modes during the annual 

measurement.

(i) Operating mode, blowdown valve leakage through the blowdown vent, wet seal and 

dry seal compressors.

(ii) Operating mode, wet seal oil degassing vents.
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(iii) Not operating, depressurized mode, unit isolation valve leakage through open 

blowdown vent, without blind flanges, wet seal and dry seal compressors.

(A) For the not operating, depressurized mode, each compressor must be measured at 

least once in any three consecutive calendar years. If a compressor is not operated and has blind 

flanges in place throughout the 3 year period, measurement is not required in this mode. If the 

compressor is in standby depressurized mode without blind flanges in place and is not operated 

throughout the 3 year period, it must be measured in the standby depressurized mode.

(2) For wet seal oil degassing vents, determine vapor volumes sent to an atmospheric 

vent or flare, using a temporary meter such as a vane anemometer or permanent flow meter 

according to 98.234(b) of this section. If you do not have a permanent flow meter, you may 

install a permanent flow meter on the wet seal oil degassing tank vent.

(3) For blowdown valve leakage and unit isolation valve leakage to open ended vents, 

you can use one of the following methods: Calibrated bagging or high volume sampler according 

to methods set forth in §98.234(c) and §98.234(d), respectively. For through valve leakage, such 

as isolation valves, you may use an acoustic leak detection device according to methods set forth 

in §98.234(a). If you do not have a flow meter, you may install a port for insertion of a 

temporary meter, or a permanent flow meter, on the vents.

(4) Estimate annual emissions using the flow measurement and Equation W-22 of this 

section.

* * *(1 ) Es,i,m  MTm Tm M i,m  Bm (Eq. W-22)

Where:

Es,i,m = Annual GHGi (either CH4 or CO2 ) volumetric emissions at standard 

conditions, in cubic feet.
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MTm = Measured gas emissions in standard cubic feet per hour.

Tm = Total time the compressor is in the mode for which Es,i is being calculated, 

in the calendar year in hours.

Mi,m = Mole fraction of GHGi in the vent gas; use the appropriate gas 

compositions in paragraph (u)(2) of this section.

Bm = Fraction of operating time that the vent gas is sent to vapor recovery or 

fuel gas as determined by keeping logs of the number of operating hours for the vapor recovery 

system and the time that vent gas is directed to the fuel gas system or sales.

(5) Calculate annual emissions from each centrifugal compressor using Equation W-23 of 

this section.

, , * * E EF T GHG s im m m i  (Eq. W-23)

Where:

Es,i,m = Annual total volumetric GHG emissions at standard conditions from each 

centrifugal compressor for mode-source combination m, in cubic feet.

EFm = Reporter emission factor for each mode m, in cubic feet per hour, from 

Equation W-24 of this section as calculated in paragraph 6.

Tm = Total time in hours per year the compressor was in each mode, as listed in 

paragraph (o)(1)(i) through (o)(1)(iii).

GHGi = For onshore natural gas processing facilities, concentration of GHGi, CH4

or CO2, in produced natural gas or feed natural gas; for other facilities listed in §98.230(a)(4) 

through (a)(8),GHGi equals 1.

(6) You shall use the flow measurements of operating mode wet seal oil degassing vent, 

operating mode blowdown valve vent and not operating depressurized mode isolation valve vent 
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for all the reporter's compressor modes not measured in the calendar year to develop the 

following emission factors using Equation W-24 of this section for each emission source and 

mode as listed in paragraph (o)(1)(i) through (o)(1)(iii).

,

1

Countm

m p

p

m

m

MT

EF

Count

 



(Eq. W-24)

Where:

EFm = Reporter emission factors for compressor in the three modes m (as listed 

in paragraph (o)(1)(i) through (o)(1)(iii)) in cubic feet per hour.

MTm,p = Flow measurements from all centrifugal compressor sources in each 

mode-source combination, m, for each measured compressor, p, in standard cubic feet per hour.

Countm= Total number of compressors measured.

m = Compressor mode-source combination as listed in paragraphs (o)(1)(i) 

through (o)(1)(iii).

(i) The emission factors must be calculated annually. You must use all measurements 

from the current calendar year and the preceding two calendar years, totaling three consecutive 

calendar years of measurements in paragraph (o)(6) of this section.

(ii) [Reserved]

(7) Onshore petroleum and natural gas production shall calculate emissions from 

centrifugal compressor wet seal oil degassing vents as follows:

Es,i Count * EFi (Eq. W-25)

Where:
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Es,i = Annual total volumetric GHG emissions at standard conditions from 

centrifugal compressor wet seals in cubic feet.

Count = Total number of centrifugal compressors for the reporter.

EFi = Emission factor for GHGi . Use 1.2 × 107 standard cubic feet per year per 

compressor for CH4 and 5.30 × 105 standard cubic feet per year per compressor for CO2 at 60 °F 

and 14.7 psia.

(8) Calculate both CH4 and CO2 mass emissions from volumetric emissions using 

calculations in paragraph (v) of this section.

(9) Calculate emissions from seal oil degassing vent vapors to flares as follows:

(i) Use the seal oil degassing vent vapor volume and gas composition as determined in 

paragraphs (o)(5) of this section.

(ii) Use the calculation methodology of flare stacks in paragraph (n) of this section to 

determine degassing vent vapor emissions from the flare.

If you are required to report emissions from centrifugal compressor venting as specified 

in §98.232(d)(2), (e)(2), (f)(2), (g)(2), and (h)(2), you must conduct volumetric emission 

measurements specified in paragraph (o)(1) of this section using methods specified in paragraphs 

(o)(2) through (o)(5) of this section; perform calculations specified in paragraphs (o)(6) through 

(o)(9) of this section; and calculate CH4 and CO2 mass emissions as specified in paragraph 

(o)(11) of this section. If emissions from a compressor source are routed to a flare, paragraphs 

(o)(1) through (o)(11) of this section do not apply and instead you must calculate CH4, CO2, and 

N2O emissions as specified in paragraph (o)(12) of this section. If emissions from a compressor 

source are captured for fuel use or are routed to a thermal oxidizer, paragraphs (o)(1) through 

(o)(12) of this section do not apply and instead you must calculate and report emissions as 
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specified in subpart C of this part. If emissions from a compressor source are routed to vapor 

recovery, the calculations specified in paragraphs (o)(1) through (o)(12) of this section do not 

apply. If you are required to report emissions from centrifugal compressor venting at an onshore 

petroleum and natural gas production facility as specified in §98.232(c)(19), you must calculate 

volumetric emissions as specified in paragraph (o)(10) of this section; and calculate CH4 and 

CO2 mass emissions as specified in paragraph (o)(11) of this section. 

(1) General requirements for conducting volumetric emission measurements. You must 

conduct volumetric emission measurements on each centrifugal compressor as specified in this 

paragraph. Compressor sources (as defined in § 98.238) without manifolded vents must use a 

measurement method specified in paragraph (o)(1)(i) or (o)(1)(ii) of this section. Manifolded 

compressor sources (as defined in § 98.238) must use a measurement method specified in 

paragraph (o)(1)(i), (o)(1)(ii), (o)(1)(iii), or (o)(1)(iv) of this section. 

(i) Centrifugal compressor source as found leak measurements. Measure venting from 

each compressor according to either paragraph (o)(1)(i)(A) or (o)(1)(i)(B) of this section at least 

once annually, based on the compressor mode (as defined in § 98.238) in which the compressor 

was found at the time of measurement, except as specified in paragraphs (o)(1)(i)(C) and 

(o)(1)(i)(D) of this section. If additional measurements beyond the required annual testing are 

performed (including duplicate measurements or measurement of additional operating modes), 

then all measurements satisfying the applicable monitoring and QA/QC that is required by this 

paragraph (o) must be used in the calculations specified in this section. 

 (A) For a compressor measured in operating-mode, you must measure volumetric 

emissions from blowdown valve leakage through the blowdown vent as specified in either 

paragraph (o)(2)(i)(A) or (o)(2)(i)(B) of this section and, if the compressor has wet seal oil 
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degassing vents, measure volumetric emissions from wet seal oil degassing vents as specified in 

paragraph (o)(2)(ii) of this section. If a compressor has a continuously operating vapor recovery 

system for the wet seal degassing, then measurement of wet seal degassing is not required. 

(B) For a compressor measured in not-operating-depressurized-mode, you must measure 

volumetric emissions from isolation valve leakage as specified in either paragraph (o)(2)(i)(A), 

(o)(2)(i)(B), or (o)(2)(i)(C) of this section. If a compressor is not operated and has blind flanges 

in place throughout the reporting period, measurement is not required in this compressor mode. 

(C) You must measure the compressor as specified in paragraph (o)(1)(i)(B) of this 

section at least once in any three consecutive calendar years, provided the measurement can be 

taken during a scheduled shutdown. If three consecutive calendar years occur without measuring 

the compressor in not-operating-depressurized-mode, you must measure the compressor as 

specified in paragraph (o)(1)(i)(B) of this section at the next scheduled depressurized shutdown. 

The requirement specified in this paragraph does not apply if the compressor has blind flanges in 

place throughout the reporting year. 

(D) You must measure the compressor as specified in paragraph (o)(1)(i)(A) of this 

section at least once in any three consecutive calendar years, provided that the measurement can 

be taken when the compressor is in operating-mode. If three consecutive calendar years occur 

without measuring the compressor in operating-mode, you must measure the compressor as 

specified in paragraph (o)(1)(i)(A) of this section in the next calendar year that the compressor is 

in operating-mode for more than 2,000 hours. 

(ii) Centrifugal compressor source continuous monitoring. Instead of measuring the 

compressor source according to paragraph (o)(1)(i) of this section for a given compressor, you 
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may elect to continuously measure volumetric emissions from a compressor source as specified 

in paragraph (o)(3) of this section. 

(iii) Manifolded centrifugal compressor source as found leak measurements. For a 

compressor source that is part of a manifolded group of compressor sources (as defined in § 

98.238), instead of measuring the compressor source according to paragraph (o)(1)(i), (o)(1)(ii), 

or (o)(1)(iv) of this section, you may elect to measure combined volumetric emissions from the 

manifolded group of compressor sources by conducting leak measurements at the common vent 

stack as specified in paragraph (o)(4) of this section. The leak measurements must be conducted 

at the frequency specified in paragraphs (o)(1)(iii)(A) through (o)(1)(iii)(C) of this section. 

(A) A minimum of three leak measurements must be taken for each manifolded group of 

compressor sources in a calendar year. 

(B) The leak measurements may be performed while the compressors are in any 

compressor mode. 

(C) The three required leak measurements must be separated by a minimum of 60 days. If 

more than two leak measurements are performed, the first and last measurements in a calendar 

year must be separated by a minimum of 120 days. 

(iv) Manifolded centrifugal compressor source continuous monitoring. For a compressor 

source that is part of a manifolded group of compressor sources, instead of measuring the 

compressor source according to paragraph (o)(1)(i), (o)(1)(ii), or (o)(1)(iii) of this section, you 

may elect to continuously measure combined volumetric emissions from the manifolded group of 

compressor sources as specified in paragraph (o)(5) of this section. 

(2) Methods for performing as found leak measurements from individual centrifugal 

compressor sources. If conducting leak measurements for each compressor source, you must 
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determine the volumetric emissions of leaks from blowdown valves and isolation valves as 

specified in paragraph (o)(2)(i) of this section, and the volumetric emissions of leaks from wet 

seal oil degassing vents as specified in paragraph (o)(2)(ii) of this section. 

(i) For blowdown valves on compressors in operating-mode and for isolation valves on 

compressors in not-operating-depressurized-mode, determine the volumetric emissions of leaks 

using one of the methods specified in paragraphs (o)(2)(i)(A) through (o)(2)(i)(C) of this section. 

(A) Measure the volumetric flow at standard conditions from the blowdown vent using 

calibrated bagging or high volume sampler according to methods set forth in § 98.234(c) and § 

98.234(d), respectively. 

(B) Measure the volumetric flow at standard conditions from the blowdown vent using a 

temporary meter such as a vane anemometer according to methods set forth in § 98.234(b). 

(C) For isolation valves, you may use an acoustic leak detection device according to 

methods set forth in § 98.234(a) instead of measuring the isolation valve leakage through the 

blowdown vent as provided for in paragraphs (o)(2)(i)(A) or (o)(2)(i)(B) of this section. 

 (ii) For wet seal oil degassing vents in operating-mode, determine vapor volumes at 

standard conditions, using a temporary meter such as a vane anemometer or permanent flow 

meter according to methods set forth in § 98.234(b). 

(3) Methods for continuous leak measurement from individual centrifugal compressor 

sources. If you elect to conduct continuous volumetric emission measurements for an individual 

compressor source as specified in paragraph (o)(1)(ii) of this section, you must measure 

volumetric emissions as specified in paragraphs (o)(3)(i) and (o)(3)(ii) of this section. 

 (i) Continuously measure the volumetric flow for the individual compressor source at 

standard conditions using a permanent meter according to methods set forth in § 98.234(b). 
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(ii) If compressor blowdown emissions are included in the metered emissions specified in 

paragraph (o)(3)(i) of this section, the compressor blowdown emissions may be included with the 

reported emissions for the compressor source and do not need to be calculated separately using 

the method specified in paragraph (i) of this section for blowdown vent stacks. 

(4) Methods for performing as found leak measurements from manifolded groups of 

centrifugal compressor sources. If conducting leak measurements for a manifolded group of 

compressor sources, you must measure volumetric emissions of leaks as specified in paragraphs 

(o)(4)(i) and (o)(4)(ii) of this section. 

(i) Measure at a single point in the manifold downstream of all compressor inputs and 

where emissions cannot be comingled with other non-compressor emission sources. 

 (ii) Determine the volumetric flow at standard conditions from the common stack using 

one of the methods specified in paragraphs (o)(4)(ii)(A) through (o)(4)(ii)(C) of this section. 

(A) A temporary meter such as a vane anemometer according the methods set forth in § 

98.234(b). 

(B) Calibrated bagging according to methods set forth in § 98.234(c). 

(C) A high volume sampler according to methods set forth § 98.234(d). 

(5) Methods for continuous leak measurement from manifolded groups of centrifugal 

compressor sources. If you elect to conduct continuous volumetric emission measurements for a 

manifolded group of compressor sources as specified in paragraph (o)(1)(iv) of this section, you 

must measure volumetric emissions as specified in paragraphs (o)(5)(i) through (o)(5)(iii) of this 

section. 

(i) Measure at a single point in the manifold downstream of all compressor inputs and 

where emissions cannot be comingled with other non-compressor emission sources. 
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(ii) Continuously measure the volumetric flow for the manifolded group of compressor 

sources at standard conditions using a permanent meter according to methods set forth in § 

98.234(b). 

(iii) If compressor blowdown emissions are included in the metered emissions specified 

in paragraph (o)(5)(ii) of this section, the compressor blowdown emissions may be included with 

the reported emissions for the manifolded group of compressor sources and do not need to be 

calculated separately using the method specified in paragraph (i) of this section for blowdown 

vent stacks. 

(6) Method for calculating volumetric GHG emissions from as found leak measurements 

for individual centrifugal compressor sources. For compressor sources measured according to 

paragraph (o)(1)(i) of this section, you must calculate annual GHG emissions from the 

compressor sources as specified in paragraphs (o)(6)(i) through (o)(6)(iv) of this section. 

(i) Using Equation W-21 of this section, calculate the annual volumetric GHG emissions 

for each centrifugal compressor mode-source combination specified in paragraphs (o)(1)(i)(A) 

and (o)(1)(i)(B) of this section that was measured during the reporting year. 

Es,i,m MTs,m *Tm *GHGi,m (Eq. W-21) 

Where: 

Es,i,m = Annual volumetric GHGi (either CH4 or CO2) emissions for measured 

compressor mode-source combination m, at standard conditions, in cubic 

feet. 

MTs,m = Volumetric gas emissions for measured compressor mode-source 

combination m, in standard cubic feet per hour, measured according to 

paragraph (o)(2) of this section. If multiple measurements are performed for a 

given mode-source combination m, use the average of all measurements. 
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Tm = Total time the compressor is in the mode-source combination for which Es,i,m

is being calculated in the reporting year, in hours. 

GHGi,m = Mole fraction of GHGi in the vent gas for measured compressor mode-source 

combination m; use the appropriate gas compositions in paragraph (u)(2) of 

this section. 

m = Compressor mode-source combination specified in paragraph (o)(1)(i)(A) or 

(o)(1)(i)(B) of this section that was measured for the reporting year. 

 (ii) Using Equation W-22 of this section, calculate the annual volumetric GHG emissions 

from each centrifugal compressor mode-source combination specified in paragraph (o)(1)(i)(A) 

and (o)(1)(i)(B) of this section that was not measured during the reporting year. 

Es,i,m EFm,s *Tm *GHGi,m (Eq. W-22) 

Where: 

Es,i,m = Annual volumetric GHGi (either CH4 or CO2) emissions for unmeasured 

compressor mode-source combination m, at standard conditions, in cubic 

feet. 

EFm,s = Reporter emission factor for compressor mode-source combination m, in 

standard cubic feet per hour, as calculated in paragraph (o)(6)(iii) of this 

section. 

Tm = Total time the compressor was in the unmeasured mode-source combination 

m, for which Es,i,m is being calculated in the reporting year, in hours. 

GHGi,m = Mole fraction of GHGi in the vent gas for unmeasured compressor modesource combination m; use the appropriate gas compositions in paragraph 

(u)(2) of this section. 

m = Compressor mode-source combination specified in paragraph (o)(1)(i)(A) or 

(o)(1)(i)(B) of this section that was not measured in the reporting year. 

 (iii) Using Equation W-23 of this section, develop an emission factor for each 

compressor mode-source combination specified in paragraph (o)(1)(i)(A) and (o)(1)(i)(B) of this 

section. These emission factors must be used in Equation W-23 of this section to determine 

Field Code Changed
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volumetric emissions from a centrifugal compressor in the mode-source combinations that were 

not measured in the reporting year. 

EF

MT

Count m s

mps

p

Count

m

m

,

, ,

 

1

 (Eq. W-23) 

Where: 

EFm,s = Reporter emission factor to be used in Equation W-23 of this section for 

compressor mode-source combination m, in standard cubic feet per hour. The 

reporter emission factor must be based on all compressors measured in 

compressor mode-source combination m in the current reporting year and the 

preceding two reporting years. 

MTm,p,s = Average volumetric gas emission measurement for compressor mode-source 

combination m, for compressor p, in standard cubic feet per hour, calculated 

using all volumetric gas emission measurements (MTm in Equation W-21 of 

this section) for compressor mode-source combination m for compressor p in 

the current reporting year and the preceding two reporting years. 

Countm = Total number of compressors measured in compressor mode-source 

combination m in the current reporting year and the preceding two reporting 

years. 

m = Compressor mode-source combination specified in paragraph (o)(1)(i)(A) or 

(o)(1)(i)(B) of this section. 

(iv) The reporter emission factor in Equation W-23 of this section may be calculated by 

using all measurements from a single owner or operator instead of only using measurements 

from a single facility. If you elect to use this option, the reporter emission factor must be applied 

to all reporting facilities for the owner or operator. 

 (7) Method for calculating volumetric GHG emissions from continuous monitoring of 

individual centrifugal compressor sources. For compressor sources measured according to 

paragraph (o)(1)(ii) of this section, you must use the continuous volumetric emission 

measurements taken as specified in paragraph (o)(3) of this section and calculate annual 

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volumetric GHG emissions associated with the compressor source using Equation W-24A of this 

section. 

Es,i,v Qs,v *GHGi,v (Eq. W-24A) 

Where: 

Es,i,v = Annual volumetric GHGi (either CH4 or CO2) emissions from compressor 

source v, at standard conditions, in cubic feet. 

Qs,v = Volumetric gas emissions from compressor source v, for reporting year, in 

standard cubic feet. 

GHGi,v = Mole fraction of GHGi in the vent gas for compressor source v; use the 

appropriate gas compositions in paragraph (u)(2) of this section. 

(8) Method for calculating volumetric GHG emissions from as found leak measurements 

of manifolded groups of centrifugal compressor sources. For manifolded groups of compressor 

sources measured according to paragraph (o)(1)(iii) of this section, you must calculate annual 

volumetric GHG emissions using Equation W-24B of this section. 

Es,i,g 8760*MTg,avg *GHGi,g (Eq. W-24B) 

Where: 

Es,i,g = Annual volumetric GHGi (either CH4 or CO2) emissions for manifolded 

group of compressor sources g, at standard conditions, in cubic feet. 

MTg,avg = Average volumetric gas emissions of all measurements performed in the 

reporting year according to paragraph (o)(4) of this section for the 

manifolded group of compressor sources g, in standard cubic feet per hour. 

GHGi,g = Mole fraction of GHGi in the vent gas for manifolded group of compressor 

sources g; use the appropriate gas compositions in paragraph (u)(2) of this 

section. 

Field Code Changed
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(9) Method for calculating volumetric GHG emissions from continuous monitoring of 

manifolded group of centrifugal compressor sources. For a manifolded group of compressor 

sources measured according to paragraph (o)(1)(iv) of this section, you must use the continuous 

volumetric emission measurements taken as specified in paragraph (o)(5) of this section and 

calculate annual volumetric GHG emissions associated with each manifolded group of 

compressor sources using Equation W-24C of this section. If the centrifugal compressors 

included in the manifolded group of compressor sources share the manifold with reciprocating 

compressors, you must follow the procedures in either this paragraph (o)(9) or paragraph (p)(9) 

of this section to calculate emissions from the manifolded group of compressor sources. 

Es,i,g Qs,g *GHGi,g (Eq. W-24C) 

Where: 

Es,i,g = Annual volumetric GHGi (either CH4 or CO2) emissions from manifolded 

group of compressor sources g, at standard conditions, in cubic feet. 

Qs,g = Volumetric gas emissions from manifolded group of compressor sources g, 

for reporting year, in standard cubic feet. 

GHGi,g = Mole fraction of GHGi in the vent gas for measured manifolded group of 

compressor sources g; use the appropriate gas compositions in paragraph 

(u)(2) of this section. 

(10) Method for calculating volumetric GHG emissions from wet seal oil degassing vents 

at an onshore petroleum and natural gas production facility. You must calculate emissions from 

centrifugal compressor wet seal oil degassing vents at an onshore petroleum and natural gas 

production facility using Equation W-25 of this section. 

Es,i Count*EFi,s (Eq. W-25) 

Where: 
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 Es,i = Annual volumetric GHGi (either CH4 or CO2) emissions from centrifugal 

compressor wet seals, at standard conditions, in cubic feet. 

Count = Total number of centrifugal compressors that have wet seal oil degassing 

vents. 

EFi,s = Emission factor for GHGi. Use 1.2 × 107 standard cubic feet per year per 

compressor for CH4 and 5.30 × 105 standard cubic feet per year per 

compressor for CO2 at 60 °F and 14.7 psia. 

(11) Method for converting from volumetric to mass emissions. You must calculate both 

CH4 and CO2 mass emissions from volumetric emissions using calculations in paragraph (v) of 

this section. 

(12) General requirements for calculating volumetric GHG emissions from centrifugal 

compressors routed to flares. You must calculate and report emissions from all centrifugal 

compressor sources that are routed to a flare as specified in paragraphs (o)(12)(i) through 

(o)(12)(iii) of this section. 

(i) Emissions calculations under this paragraph (o) of this section are not required for 

compressor sources that are routed to a flare. 

(ii) If any compressor sources are routed to a flare, calculate the emissions for the flare 

stack as specified in paragraph (n) of this section and report emissions from the flare as specified 

in § 98.236(n), without subtracting emissions attributable to compressor sources from the flare. 

(iii) Report all applicable activity data for compressors with compressor sources routed to 

flares as specified in § 98.236(o). 

(p) Reciprocating compressor venting. Calculate CH4 and CO2 emissions from all 

reciprocating compressor vents as follows. For each reciprocating compressor covered in 

§98.232(d)(1), (e)(1), (f)(1), (g)(1), and (h)(1) you must conduct an annual measurement for each 

compressor in the mode in which it is found during the annual measurement, except as specified 
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in paragraph (p)(9) of this section. Measure emissions from (including emissions manifolded to 

common vents) reciprocating rod packing vents, unit isolation valve vents, and blowdown valve 

vents. Record emissions from the following vent types in the specified compressor modes during 

the annual measurement as follows:

(1) Operating or standby pressurized mode, blowdown vent leakage through the 

blowdown vent stack.

(2) Operating mode, reciprocating rod packing emissions.

(3) Not operating, depressurized mode, unit isolation valve leakage through the 

blowdown vent stack, without blind flanges.

(i) For the not operating, depressurized mode, each compressor must be measured at least 

once in any three consecutive calendar years if this mode is not found in the annual 

measurement. If a compressor is not operated and has blind flanges in place throughout the 3 

year period, measurement is not required in this mode. If the compressor is in standby 

depressurized mode without blind flanges in place and is not operated throughout the 3 year 

period, it must be measured in the standby depressurized mode.

(ii) [Reserved]

(4) If reciprocating rod packing and blowdown vent are connected to an open-ended vent 

line use one of the following two methods to calculate emissions:

(i) Measure emissions from all vents (including emissions manifolded to common vents) 

including rod packing, unit isolation valves, and blowdown vents using either calibrated bagging 

or high volume sampler according to methods set forth in §98.234(c) and §98.234(d), 

respectively.

Formatted: Level 2
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(ii) Use a temporary meter such as a vane anemometer or a permanent meter such as an 

orifice meter to measure emissions from all vents (including emissions manifolded to a common

vent) including rod packing vents and unit isolation valve leakage through blowdown vents 

according to methods set forth in §98.234(b). If you do not have a permanent flow meter, you 

may install a port for insertion of a temporary meter or a permanent flow meter on the vents. For 

through-valve leakage to open ended vents, such as unit isolation valves on not operating, 

depressurized compressors and blowdown valves on pressurized compressors, you may use an 

acoustic detection device according to methods set forth in §98.234(a).

(5) If reciprocating rod packing is not equipped with a vent line use the following method 

to calculate emissions:

(i) You must use the methods described in §98.234(a) to conduct annual leak detection of 

equipment leaks from the packing case into an open distance piece, or from the compressor crank 

case breather cap or other vent with a closed distance piece.

(ii) Measure emissions found in paragraph (p)(5)(i) of this section using an appropriate 

meter, or calibrated bag, or high volume sampler according to methods set forth in §98.234(b), 

(c), and (d), respectively.

(6) Estimate annual emissions using the flow measurement and Equation W-26 of this 

section.

Es,i,m  MTm *Tm * M i,m (Eq. W-26)

Where:

Es,i,m = Annual GHG i (either CH4 or CO2 ) volumetric emissions at standard 

conditions, in cubic feet.

MTm = Measured gas emissions in standard cubic feet per hour.
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Tm = Total time the compressor is in the mode for which Es,i,m is being 

calculated, in the calendar year in hours.

Mi,m = Mole fraction of GHG i in gas; use the appropriate gas compositions in 

paragraph (u)(2) of this section.

(7) Calculate annual emissions from each reciprocating compressor using Equation W-27 

of this section.

, , * * E EF T GHG s im m m i  (Eq. W-27)

Where:

Es,i,m = Annual total volumetric GHG emissions at standard conditions from each 

reciprocating compressor for mode-source combination m, in cubic feet.

EFm = Reporter emission factor for each mode, m, in cubic feet per hour, from 

Equation W-28 of this section as calculated in paragraph (p)(7)(i) of this section.

Tm = Total time in hours per year the compressor was in each mode, m, as listed 

in paragraph (p)(1) through (p)(3).

GHGi = For onshore natural gas processing facilities, concentration of GHG i, CH4

or CO2, in produced natural gas or feed natural gas; for other facilities listed in §98.230(a)(4) 

through (a)(8), GHGi equals 1.

m = Compressor mode as listed in paragraph (p)(1) through (p)(3).

(i) You shall use the flow meter readings from measurements of operating and standby 

pressurized blowdown vent, operating mode vents, not operating depressurized isolation valve 

vent for all the reporter's compressor modes not measured in the calendar year to develop the 

following emission factors using Equation W-28 of this section for each mode as listed in 

paragraph (p)(1) through (p)(3).
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,

1

Countm

m p

p

m

m

MT

EF

Count

 



(Eq. W-28)

Where:

EFm = Reporter emission factors for compressor in the three modes, m, in cubic 

feet per hour.

MTm,p = Flow measurements from all reciprocating compressor sources in each 

mode-source combination, m, for each measured compressor, p, in standard cubic feet per hour.

Countm= Total number of compressors measured in each mode, m.

m = Compressor mode-source combination as listed in (p)(1) through (p)(3).

(A) You must combine emissions for blowndown vents, measured in the operating and 

standby pressurized modes.

(B) The emission factors must be calculated annually. You must use all measurements 

from the current calendar year and the preceding two calendar years, totaling three consecutive 

calendar years of measurements.

(ii) [Reserved]

(8) Determine if the reciprocating compressor vent vapors are sent to a vapor recovery 

system.

(i) Adjust the emissions estimated in paragraphs (p)(7) of this section downward by the 

magnitude of emissions recovered using a vapor recovery system as determined by engineering 

estimate based on best available data.

(ii) [Reserved]
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(9) Onshore petroleum and natural gas production shall calculate emissions from 

reciprocating compressors as follows:

Es,i Count * EFi (Eq. W-29)

Where:

Es,i = Annual total volumetric GHG emissions at standard conditions from 

reciprocating compressors in cubic feet.

Count = Total number of reciprocating compressors for the reporter.

EFi = Emission factor for GHGi . Use 9.48 × 103 standard cubic feet per year per 

compressor for CH4 and 5.27 × 102 standard cubic feet per year per compressor for CO2 at 60 °F 

and 14.7 psia.

(10) Estimate CH4 and CO2 volumetric and mass emissions from volumetric natural gas 

emissions using the calculations in paragraphs (u) and (v) of this section.

If you are required to report emissions from reciprocating compressor venting as 

specified in §98.232(d)(1), (e)(1), (f)(1), (g)(1), and (h)(1), you must conduct volumetric 

emission measurements specified in paragraph (p)(1) of this section using methods specified in 

paragraphs (p)(2) through (p)(5) of this section; perform calculations specified in paragraphs 

(p)(6) through (p)(9) of this section; and calculate CH4 and CO2 mass emissions as specified in 

paragraph (p)(11) of this section. If emissions from a compressor source are routed to a flare, 

paragraphs (p)(1) through (p)(11) of this section do not apply and instead you must calculate 

CH4, CO2, and N2O emissions as specified in paragraph (p)(12) of this section. If emissions from 

a compressor source are captured for fuel use or are routed to a thermal oxidizer, paragraphs 

(p)(1) through (p)(12) of this section do not apply and instead you must calculate and report 

emissions as specified in subpart C of this part. If emissions from a compressor source are routed 
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to vapor recovery, the calculations specified in paragraphs (p)(1) through (p)(12) of this section 

do not apply. If you are required to report emissions from reciprocating compressor venting at an 

onshore petroleum and natural gas production facility as specified in §98.232(c)(11), you must 

calculate volumetric emissions as specified in paragraph (p)(10) of this section; and calculate 

CH4 and CO2 mass emissions as specified in paragraph (p)(11) of this section. 

(1) General requirements for conducting volumetric emission measurements. You must 

conduct volumetric emission measurements on each reciprocating compressor as specified in this 

paragraph. Compressor sources (as defined in § 98.238) without manifolded vents must use a 

measurement method specified in paragraph (p)(1)(i) or (p)(1)(ii) of this section. Manifolded 

compressor sources (as defined in § 98.238) must use a measurement method specified in 

paragraph (p)(1)(i), (p)(1)(ii), (p)(1)(iii), or (p)(1)(iv) of this section. 

(i) Reciprocating compressor source as found leak measurements. Measure venting from 

each compressor according to either paragraph (p)(1)(i)(A), (p)(1)(i)(B), or (p)(1)(i)(C) of this 

section at least once annually, based on the compressor mode (as defined in § 98.238) in which 

the compressor was found at the time of measurement, except as specified in paragraph 

(p)(1)(i)(D) of this section. If additional measurements beyond the required annual testing are 

performed (including duplicate measurements or measurement of additional operating modes), 

then all measurements satisfying the applicable monitoring and QA/QC that is required by this 

paragraph (o) must be used in the calculations specified in this section. 

(A) For a compressor measured in operating-mode, you must measure volumetric 

emissions from blowdown valve leakage through the blowdown vent as specified in either 

paragraph (p)(2)(i)(A) or (p)(2)(i)(B) of this section, and measure volumetric emissions from 

reciprocating rod packing as specified in paragraph (p)(2)(ii) of this section. 
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(B) For a compressor measured in standby-pressurized-mode, you must measure 

volumetric emissions from blowdown valve leakage through the blowdown vent as specified in 

either paragraph (p)(2)(i)(A) or (p)(2)(i)(B) of this section. 

(C) For a compressor measured in not-operating-depressurized-mode, you must measure 

volumetric emissions from isolation valve leakage as specified in either paragraph (p)(2)(i)(A), 

(p)(2)(i)(B), or (p)(2)(i)(C) of this section. If a compressor is not operated and has blind flanges 

in place throughout the reporting period, measurement is not required in this compressor mode. 

(D) You must measure the compressor as specified in paragraph (p)(1)(i)(C) of this 

section at least once in any three consecutive calendar years, provided the measurement can be 

taken during a scheduled shutdown. If there is no scheduled shutdown within three consecutive 

calendar years, you must measure the compressor as specified in paragraph (p)(1)(i)(C) of this 

section either prior to or during the next compressor shutdown when the replacement of the 

compressor rod packing occurs. 

(ii) Reciprocating compressor source continuous monitoring. Instead of measuring the 

compressor source according to paragraph (p)(1)(i) of this section for a given compressor, you 

may elect to continuously measure volumetric emissions from a compressor source as specified 

in paragraph (p)(3) of this section. 

(iii) Manifolded reciprocating compressor source as found leak measurements. For a 

compressor source that is part of a manifolded group of compressor sources (as defined in § 

98.238), instead of measuring the compressor source according to paragraph (p)(1)(i), (p)(1)(ii), 

or (p)(1)(iv) of this section, you may elect to measure combined volumetric emissions from the 

manifolded group of compressor sources by conducting leak measurements at the common vent 
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stack as specified in paragraph (p)(4) of this section. The leak measurements must be conducted 

at the frequency specified in paragraphs (p)(1)(iii)(A) through (p)(1)(iii)(C) of this section. 

(A) A minimum of three leak measurements must be taken for each manifolded group of 

compressor sources in a calendar year. 

(B) The leak measurements may be performed while the compressors are in any 

compressor mode. 

(C) The three required leak measurements must be separated by a minimum of 60 days. If 

more than three leak measurements are performed, the first and last measurements in a calendar 

year must be separated by a minimum of 120 days. 

(iv) Manifolded reciprocating compressor source continuous monitoring. For a 

compressor source that is part of a manifolded group of compressor sources, instead of 

measuring the compressor source according to paragraph (p)(1)(i), (p)(1)(ii), or (p)(1)(iii) of this 

section, you may elect to continuously measure combined volumetric emissions from the 

manifolded group of compressors sources as specified in paragraph (p)(5) of this section. 

(2) Methods for performing as found leak measurements from individual reciprocating 

compressor sources. If conducting leak measurements for each compressor source, you must 

determine the volumetric emissions of leaks from blowdown valves and isolation valves as 

specified in paragraph (p)(2)(i) of this section. You must determine the volumetric emissions of 

leaks from reciprocating rod packing as specified in paragraph (p)(2)(ii) or (p)(2)(iii) of this 

section. 

(i) For blowdown valves on compressors in operating-mode or standby-pressurizedmode, and for isolation valves on compressors in not-operating-depressurized-mode, determine 
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puroposes only. We have taken steps to ensure the accuracy of this version, but it is not the official version. 

the volumetric emissions of leaks using one of the methods specified in paragraphs (p)(2)(i)(A) 

through (p)(2)(i)(C) of this section. 

(A) Measure the volumetric flow at standard conditions from the blowdown vent using 

calibrated bagging or high volume sampler according to methods set forth in § 98.234(c) and § 

98.234(d), respectively. 

(B) Measure the volumetric flow at standard conditions from the blowdown vent using a 

temporary meter such as a vane anemometer, according to methods set forth in § 98.234(b). 

(C) For isolation valves, you may use an acoustic leak detection device according to 

methods set forth in § 98.234(a) instead of measuring the isolation valve leakage through the 

blowdown vent as provided for in paragraphs (p)(2)(i)(A) or (p)(2)(i)(B) of this section. 

(ii) For reciprocating rod packing equipped with an open-ended vent line on compressors 

in operating-mode, determine the volumetric emissions of leaks using one of the methods 

specified in paragraphs (p)(2)(ii)(A) and (p)(2)(ii)(B) of this section. 

(A) Measure the volumetric flow at standard conditions from the open-ended vent line 

using calibrated bagging or high volume sampler according to methods set forth in § 98.234(c) 

and § 98.234(d), respectively. 

(B) Measure the volumetric flow at standard conditions from the open-ended vent line 

using a temporary meter such as a vane anemometer, according to methods set forth in § 

98.234(b). 

(iii) For reciprocating rod packing not equipped with an open-ended vent line on 

compressors in operating-mode, you must determine the volumetric emissions of leaks using the 

method specified in paragraphs (p)(2)(iii)(A) and (p)(2)(iii)(B) of this section. 
Page 81 of 214 

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(A) You must use the methods described in §98.234(a) to conduct annual leak detection 

of equipment leaks from the packing case into an open distance piece, or from the compressor 

crank case breather cap or other vent with a closed distance piece. 

(B) You must measure emissions found in paragraph (p)(2)(iii)(A) of this section using 

an appropriate meter, calibrated bag, or high volume sampler according to methods set forth in 

§98.234(b), (c), and (d), respectively. 

(3) Methods for continuous leak measurement from individual reciprocating compressor 

sources. If you elect to conduct continuous volumetric emission measurements for an individual 

compressor source as specified in paragraph (p)(1)(ii) of this section, you must measure 

volumetric emissions as specified in paragraphs (p)(3)(i) and (p)(3)(ii) of this section. 

(i) Continuously measure the volumetric flow for the individual compressor sources at 

standard conditions using a permanent meter according to methods set forth in § 98.234(b). 

(ii) If compressor blowdown emissions are included in the metered emissions specified in 

paragraph (p)(3)(i) of this section, the compressor blowdown emissions may be included with the 

reported emissions for the compressor source and do not need to be calculated separately using 

the method specified in paragraph (i) of this section for blowdown vent stacks. 

(4) Methods for performing as found leak measurements from manifolded groups of 

reciprocating compressor sources. If conducting leak measurements for a manifolded group of 

compressor sources, you must measure volumetric emissions of leaks as specified in paragraphs 

(p)(4)(i) and (p)(4)(ii) of this section. 

(i) Measure at a single point in the manifold downstream of all compressor inputs and 

where emissions cannot be comingled with other non-compressor emission sources. 
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(ii) Determine the volumetric flow at standard conditions from the common stack using 

one of the methods specified in paragraph (p)(4)(ii)(A) through (p)(4)(ii)(C). 

(A) A temporary meter such as a vane anemometer according the methods set forth in § 

98.234(b). 

(B) Calibrated bagging according to methods set forth in § 98.234(c). 

(C) A high volume sampler according to methods set forth § 98.234(d). 

(5) Methods for continuous leak measurement from manifolded groups of reciprocating 

compressor sources. If you elect to conduct continuous volumetric emission measurements for a 

manifolded group of compressor sources as specified in paragraph (p)(1)(iv) of this section, you 

must measure volumetric emissions as specified in paragraphs (p)(5)(i) through (p)(5)(iii) of this 

section. 

(i) Measure at a single point in the manifold downstream of all compressor inputs and 

where emissions cannot be comingled with other non-compressor emission sources. 

(ii) Continuously measure the volumetric flow for the manifolded group of compressor 

sources at standard conditions using a permanent meter according to methods set forth in § 

98.234(b). 

(iii) If compressor blowdown emissions are included in the metered emissions specified 

in paragraph (p)(5)(ii) of this section, the compressor blowdown emissions may be included with 

the reported emissions for the manifolded group of compressor sources and do not need to be 

calculated separately using the method specified in paragraph (i) of this section for blowdown 

vent stacks. 

(6) Method for calculating volumetric GHG emissions from as found leak measurements 

for individual reciprocating compressor sources. For compressor sources measured according to 
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paragraph (p)(1)(i) of this section, you must calculate GHG emissions from the compressor 

sources as specified in paragraphs (p)(6)(i) through (p)(6)(iv) of this section. 

(i) Using Equation W-26 of this section, calculate the annual volumetric GHG emissions 

for each reciprocating compressor mode-source combination specified in paragraphs (p)(1)(i)(A) 

through (p)(1)(i)(C) of this section that was measured during the reporting year. 

Es,i,m MTs,m *Tm *GHGi,m (Eq. W-26) 

Where: 

Es,i,m = Annual volumetric GHGi (either CH4 or CO2) emissions for measured 

compressor mode-source combination m, at standard conditions, in cubic 

feet. 

MTs,m = Volumetric gas emissions for measured compressor mode-source 

combination m, in standard cubic feet per hour, measured according to 

paragraph (p)(2) of this section. If multiple measurements are performed for a 

given mode-source combination m, use the average of all measurements. 

Tm = Total time the compressor is in the mode-source combination m, for which 

Es,i,m is being calculated in the reporting year, in hours. 

GHGi,m = Mole fraction of GHGi in the vent gas for measured compressor mode-source 

combination m; use the appropriate gas compositions in paragraph (u)(2) of 

this section. 

m = Compressor mode-source combination specified in paragraph (p)(1)(i)(A), 

(p)(1)(i)(B), or (p)(1)(i)(C) of this section that was measured for the reporting 

year. 

(ii) Using Equation W-27 of this section, calculate the annual volumetric GHG emissions 

from each reciprocating compressor mode-source combination specified in paragraph 

(p)(1)(i)(A), (p)(1)(i)(B), and (p)(1)(i)(C) of this section that was not measured during the 

reporting year. 

Es,i,m EFm,s *Tm *GHGi,m (Eq. W-27) 

Field Code Changed

Field Code Changed
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puroposes only. We have taken steps to ensure the accuracy of this version, but it is not the official version. 

Where: 

Es,i,m = Annual volumetric GHGi (either CH4 or CO2) emissions for unmeasured 

compressor mode-source combination m, at standard conditions, in cubic 

feet. 

EFm,s = Reporter emission factor for compressor mode-source combination m, in 

standard cubic feet per hour, as calculated in paragraph (p)(6)(iii) of this 

section. 

Tm = Total time the compressor was in the unmeasured mode-source combination 

m, for which Es,i,m is being calculated in the reporting year, in hours. 

GHGi,m = Mole fraction of GHGi in the vent gas for unmeasured compressor modesource combination m; use the appropriate gas compositions in paragraph 

(u)(2) of this section. 

m = Compressor mode-source combination specified in paragraph (p)(1)(i)(A), 

(p)(1)(i)(B), or (p)(1)(i)(C) of this section that was not measured in the 

reporting year. 

(iii) Using Equation W-28 of this section, develop an emission factor for each compressor 

mode-source combination specified in paragraph (p)(1)(i)(A), (p)(1)(i)(B), and (p)(1)(i)(C) of 

this section. These emission factors must be used in Equation W-27 of this section to determine 

volumetric emissions from a reciprocating compressor in the mode-source combinations that 

were not measured in the reporting year. EF

MT

Count m s

mps

p

Count

m

m

,

, ,

 

1

(Eq. W-28)

Where:

EFm = Reporter emission factors for compressor in the three modes, m, in cubic 

feet per hour.

MTm,p = Flow measurements from all reciprocating compressor sources in each 

mode-source combination, m, for each measured compressor, p, in standard cubic feet per hour.

Countm= Total number of compressors measured in each mode, m.

Formatted: ___GHG PARAGRAPH, None

Formatted: ___GHG PARAGRAPH
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m = Compressor mode-source combination as listed in (p)(1) through (p)(3).

(A) You must combine emissions for blowndown vents, measured in the operating and 

standbypressurized modes.

(B) The emission factors must be calculated annually. You must use all measurements 

from the current calendar year and the preceding two calendar years, totaling three consecutive 

calendar years of measurements.

(ii) [Reserved]

(8) Determine if the reciprocating compressor vent vapors are sent to a vapor recovery 

system.

(i) Adjust the emissions estimated in paragraphs (p)(7) of this section downward by the 

magnitude of emissions recovered using a vapor recovery system as determined by engineering 

estimate based on best available data.

(ii) [Reserved]

(9) Onshore petroleum and natural gas production shall calculate emissions from 

reciprocating compressors as follows:

Es,i,v Qs,v *GHGi,v (Eq. W-29)

Where:

Es,i = Annual total volumetric GHG emissions at standard conditionsfrom 

Es,i,g 8760*MTg,avg *GHGi,g reciprocating compressors Es,i,g  Qs,g *GHGi,g Es,i Count*EFi,s

in cubic feet.

Count = Total number of reciprocating compressors for the reporter.

Formatted: None

Formatted: None

Formatted: ___GHG PARAGRAPH
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EFi = Emission factor for GHGi. Use 9.48 × 103 standard cubic feet per year per 

compressor for CH4 and 5.27 × 102 standard cubic feet per year per compressor for CO2 at 60 °F 

and 14.7 psia. 

(10) Estimate CH4 and CO2 volumetric and mass emissions from volumetric natural gas 

emissions using the calculations in paragraphs (u) and (v) of this section.

.

EF

MT

Count m s

mps

p

Count

m

m

,

, ,

 

1

 (Eq. W-28) 

Where: 

EFm,s = Reporter emission factor to be used in Equation W-27 of this section for 

compressor mode-source combination m, in standard cubic feet per hour. The 

reporter emission factor must be based on all compressors measured in 

compressor mode-source combination m in the current reporting year and the 

preceding two reporting years. 

MTm,p,s = Average volumetric gas emission measurement for compressor mode-source 

combination m, for compressor p, in standard cubic feet per hour, calculated 

using all volumetric gas emission measurements (MTm in Equation W-26 of 

this section) for compressor mode-source combination m for compressor p in 

the current reporting year and the preceding two reporting years. 

Countm = Total number of compressors measured in compressor mode-source 

combination m in the current reporting year and the preceding two reporting 

years. 

m = Compressor mode-source combination specified in paragraph (p)(1)(i)(A), 

(p)(1)(i)(B), or (p)(1)(i)(C) of this section. 

(A) Emission factors must be calculated annually for each compressor mode-source 

combination specified in paragraph ((p)(1)(i)(A), (p)(1)(i)(B), and (p)(1)(i)(C) of this section. 

(B) You must combine emissions for blowndown vents, measured in the operating and 

standby-pressurized modes. 

Field Code Changed
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puroposes only. We have taken steps to ensure the accuracy of this version, but it is not the official version. 

(iv) The reporter emission factor in Equation W-28 of this section may be calculated by 

using all measurements from a single owner or operator instead of only using measurements 

from a single facility. If you elect to use this option, the reporter emission factor must be applied 

to all reporting facilities for the owner or operator. 

(7) Method for calculating volumetric GHG emissions from continuous monitoring of 

individual reciprocating compressor sources. For compressor sources measured according to 

paragraph (p)(1)(ii) of this section, you must use the continuous volumetric emission 

measurements taken as specified in paragraph (p)(3) of this section and calculate annual 

volumetric GHG emissions associated with the compressor source using Equation W-29A of this 

section. 

Es,i,v Qs,v *GHGi,v (Eq. W-29A) 

Where: 

Es,i,v = Annual volumetric GHGi (either CH4 or CO2) emissions from compressor 

source v, at standard conditions, in cubic feet. 

Qs,v = Volumetric gas emissions from compressor source v, for reporting year, in 

standard cubic feet. 

GHGi,v = Mole fraction of GHGi in the vent gas for compressor source v; use the 

appropriate gas compositions in paragraph (u)(2) of this section. 

(8) Method for calculating volumetric GHG emissions from as found leak measurements 

of manifolded groups of reciprocating compressor sources. For manifolded groups of compressor 

sources measured according to paragraph (p)(1)(iii) of this section, you must calculate annual 

GHG emissions using Equation W-29B of this section. 

Es,i,g 8760*MTg,avg *GHGi,g (Eq. W-29B) 

Field Code Changed

Field Code Changed
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Where: 

Es,i,g = Annual volumetric GHGi (either CH4 or CO2) emissions for manifolded 

group of compressor sources g, at standard conditions, in cubic feet. 

MTg,avg = Average volumetric gas emissions of all measurements performed in the 

reporting year according to paragraph (p)(4) of this section for the 

manifolded group of compressor sources g, in standard cubic feet per hour. 

GHGi,g = Mole fraction of GHGi in the vent gas for manifolded group of compressor 

sources g; use the appropriate gas compositions in paragraph (u)(2) of this 

section. 

(9) Method for calculating volumetric GHG emissions from continuous monitoring of 

manifolded group of reciprocating compressor sources. For a manifolded group of compressor 

sources measured according to paragraph (p)(1)(iv) of this section, you must use the continuous 

volumetric emission measurements taken as specified in paragraph (p)(5) of this section and 

calculate annual volumetric GHG emissions associated with each manifolded group of 

compressor sources using Equation W-29C of this section. If the reciprocating compressors 

included in the manifolded group of compressor sources share the manifold with centrifugal 

compressors, you must follow the procedures in either this paragraph (p)(9) or paragraph (o)(9) 

of this section to calculate emissions from the manifolded group of compressor sources. 

Es,i,g  Qs,g *GHGi,g (Eq. W-29C) 

Where: 

Es,i,g = Annual volumetric GHGi (either CH4 or CO2) emissions from manifolded 

group of compressor sources g, at standard conditions, in cubic feet. 

Qs,g = Volumetric gas emissions from manifolded group of compressor sources g, 

for reporting year, in standard cubic feet. 

GHGi,g = Mole fraction of GHGi in the vent gas for measured manifolded group of 

compressor sources g; use the appropriate gas compositions in paragraph 

(u)(2) of this section. 

Field Code Changed
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(10) Method for calculating volumetric GHG emissions from reciprocating compressor 

venting at an onshore petroleum and natural gas production facility. You must calculate 

emissions from reciprocating compressor venting at an onshore petroleum and natural gas 

production facility using Equation W-29D of this section. 

Es,i Count*EFi,s (Eq. W-29D) 

Where: 

Es,i = Annual volumetric GHGi (either CH4 or CO2 ) emissions from reciprocating 

compressors, at standard conditions, in cubic feet. 

Count = Total number of reciprocating compressors. 

EFi,s = Emission factor for GHGi. Use 9.48 × 103 standard cubic feet per year per 

compressor for CH4 and 5.27 × 102 standard cubic feet per year per 

compressor for CO2 at 60 °F and 14.7 psia. 

(11) Method for converting from volumetric to mass emissions. You must calculate both 

CH4 and CO2 mass emissions from volumetric emissions using calculations in paragraph (v) of 

this section. 

(12) General requirements for calculating volumetric GHG emissions from reciprocating 

compressors routed to flares. You must calculate and report emissions from all reciprocating 

compressor sources that are routed to a flare as specified in paragraphs (p)(12)(i) through 

(p)(12)(iii) of this section. 

(i) Emissions calculations under this paragraph (p) of this section are not required for 

compressor sources that are routed to a flare. 

(ii) If any compressor sources are routed to a flare, calculate the emissions for the flare 

stack as specified in paragraph (n) of this section and report emissions from the flare as specified 

in § 98.236(n), without subtracting emissions attributable to compressor sources from the flare. 

Field Code Changed
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(iii) Report all applicable activity data for compressors with compressor sources routed to 

flares as specified in § 98.236(p). 

(q) Equipment leak surveys. Leak detection and leaker emission factors.You must use the 

methods described in §98.234(a) to conduct leak detection(s) of equipment leaks from all 

component types listed in §98.232(d)(7), (e)(7), (f)(5), (g)(3), (h)(4), and (i)(1). This paragraph 

(q) applies to component types in streams with gas content greater than 10 percent CH4 plus CO2

by weight. Component types in streams with gas content less than or equal to 10 percent CH4

plus CO2 by weight are exempt from the requirements of this paragraph (q) and do not need to be 

reported. Tubing systems equal to or less than one half inch diameter are exempt from the 

requirements of this paragraph (q) and do not need to be reported. IfFor industry segments listed 

in § 98.230(a)(3) through (a)(8), if equipment leaks are detected for sourcescomponent types

listed in this paragraph (q), then you must calculate equipment leak emissions per component 

type per reporting facility using Equations W-30A or W-30B30 of this section for each 

component type. Use. For the industry segment listed in § 98.230(a)(8), the results from 

Equation W-30 are used to calculate population emission factors on a meter/regulator run basis 

using Equation W-30A for industry segments listed in 98.230(a)(3)-(a)(7). Use Equation W-30B 

for industry segments listed in 98.230(a)(8).31 of this section.





p x

z

Es p i GHGi EFs p Tp z

1

, , * , * , (Eq. W-30A30) 

 

      



t

q t n

x

p

Es i GHGi EF Tp q

1 1

, * * , (Eq. W-30B)

Where: 
Page 91 of 214 

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Es,p,i = Annual total volumetric GHG emissions at standard conditionsof GHGi from 

eachspecific component type “p” (listed in § 98.232(d)(7), (e)(7), (f)(5), 

(g)(3), (h)(4), and (i)(1)) in standard (“s”) cubic feet, as specified in 

paragraphs (q)(1) through (q)(8) of this section. 

xxp = Total number of eachspecific component type “p” detected as leaking during 

annual leak surveys. 

EFEFs,p = Leaker emission factor for specific component types listed in Table W-2 

through Table W-7 of this subpart. 

GHGi = For onshore natural gas processing facilities, concentration of GHGi, CH4 or 

CO2, in the total hydrocarbon of the feed natural gas; for onshore natural gas 

transmission compression and underground natural gas storage, GHGi equals 

0.975 for CH4 and 1.1 ×10−2

 for CO2 ; for LNG storage and LNG import and 

export equipment, GHGi equals 1 for CH4 and 0 for CO2 ; and for natural gas 

distribution, GHGi equals 1 for CH4 and 1.1 × 10−2

 CO2. 

Tp,z = The total time the surveyed component, “z”, component type “p,”, was found 

leaking and operational, in hours. If one leak detection survey is conducted in 

the calendar year, assume the component was leaking for the entire calendar 

year., accounting for time the component was not operational (i.e. not 

operating under pressure) using engineering estimate based on best available 

data. If multiple leak detection surveys are conducted in the calendar year, 

assume that the component found to be leaking has been leaking since the 

previous survey (if not found leaking in the previous survey) or the beginning 

of the calendar year (if it was found leaking in the previous survey)., 

accounting for time the component was not operational using engineering 

estimate based on best available data. For the last leak detection survey in the 

calendar year, assume that all leaking components continue to leak until the 

end of the calendar year, accounting for time the component was not 

operational using engineering estimate based on best available data.

t = Calendar year of reporting.

n = The number of years over which one complete cycle of leak detection is 

conducted over all the T-D transfer stations in a natural gas distribution 

facility; 0 < n ≤ 5. For the first (n-1) calendar years of reporting the 

summation in Equation W-30B should be for years that the data is available.

Tp,q = The total time the component, p, was found leaking and operational, in hours, 

in year q. If one leak detection survey is conducted, assume the component 

was leaking for the entire period n. If multiple leak detection surveys are 

conducted, assume that the component found to be leaking has been leaking 

since the previous survey (if not found to be leaking in the previous survey) 

or the beginning of the calendar year (if it was found to be leaking in the 

Formatted: _tabs for equations_last
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previous survey). For the last leak detection survey in the cycle, assume that 

all leaking components continue to leak until the end of the cycle.

(1) You must select to conduct either one leak detection survey in a calendar year or 

multiple complete leak detection surveys in a calendar year. The number of leak detection 

surveys selected must be conducted during the calendar year. 

(2) Calculate GHGboth CO2 and CH4 mass emissions in carbon dioxide equivalent at 

standard conditions using calculations in paragraph (v) of this section. 

(3) Onshore natural gas processing facilities shallmust use the appropriate default total 

hydrocarbon leaker emission factors for compressor components in gas service and noncompressor components in gas service listed in Table W-2 of this subpart for equipment leaks 

detected from valves, connectors, open ended lines, pressure relief valves, and meters. 

(4) Onshore natural gas transmission compression facilities shallmust use the appropriate 

default total hydrocarbon leaker emission factors for compressor components in gas service and 

non-compressor components in gas service listed in Table W-3 of this subpart for equipment 

leaks detected from valves, connectors, open ended lines, pressure relief valves, and meters. 

(5) Underground natural gas storage facilities for storage stations shallmust use the 

appropriate default total hydrocarbon leaker emission factors for storage stations in gas service 

listed in Table W-4 of this subpart for equipment leaks detected from valves, connectors, open 

ended lines, pressure relief valves, and meters. 

(6) LNG storage facilities shallmust use the appropriate default methane leaker emission 

factors for LNG storage components in gas service listed in Table W-5 of this subpart for 

equipment leaks detected from valves, pump seals, connectors, and other. 
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(7) LNG import and export facilities shallmust use the appropriate default methane leaker 

emission factors for LNG terminals components in LNG service listed in Table W-6 of this 

subpart for equipment leaks detected from valves, pump seals, connectors, and other. 

(8) Natural gas distribution facilities for above grade transmission-distribution transfer 

stations, shallmust use the appropriate Equation W-30 of this section and the default methane 

leaker emission factors for transmission-distribution transfer station components in gas service 

listed in Table W-7 of this subpart for equipment leaks detected from connectors, block valves, 

control valves, pressure relief valves, orifice meters, regulators, and open ended lines. Leak 

detection at naturalto calculate component emissions from annual equipment leak surveys 

conducted at above grade transmission-distribution transfer stations. Natural gas distribution 

facilities is onlyare required to perform equipment leak surveys only at above grade stations that 

qualify as transmission-distribution transfer stations. Below grade transmission-distribution 

transfer stations and all metering-regulating stations that do not meet the definition of 

transmission-distribution transfer stations are not required to perform componentequipment leak 

detectionsurveys under this section. 

(i) Natural gas distribution facilities may choose to conduct equipment leak 

detectionsurveys at the T-Dall above grade transmission-distribution transfer stations over 

multiple years, not exceeding a five year period to cover all T-Dabove grade transmissiondistribution transfer stations. If the facility chooses to use the multiple year option, then the 

number of T-Dtransmission-distribution transfer stations that are monitored in each year should 

be approximately equal across all years in the cycle without monitoring the same station twice 

during the multiple year survey. 
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(ii) [Reserved]Use Equation W-31 to determine the meter/regulator run population 

emission factors for each GHGi. The meter/regulator run population emission factors calculated 

using Equation W-31 must be used in Equation W-32B of this section to estimate emissions from 

above grade metering-regulating stations that are not transmission-distribution transfer stations. 

As additional survey data become available, you must recalculate the meter/regulator run 

population emission factors for each GHGi annually according to paragraph (q)(8)(iii) of this 

section. 

 



 

   n

y

Count

w

w y

n

y p

s p i y

s MR i MR y

T

E

EF

1 1

,

1

7

1

, , ,

, , ,

(Eq. W-31) 

Where: 

EFs,MR,i = Meter/regulator run population emission factor for GHGi based on all 

surveyed above grade transmission-distribution transfer stations over “n” 

years, in standard cubic feet of GHGi per operational hour of all 

meter/regulator runs. 

Es,p,i,y = Annual total volumetric emissions at standard conditions of GHGi from 

component type “p” during year “y” in standard (“s”) cubic feet, as calculated 

using Equation W-30 of this section. 

p = Seven component types listed in Table W-7 of this subpart for transmissiondistribution transfer stations. 

Tw,y = The total time the surveyed meter/regulator run “w” was operational, in hours 

during survey year “y” using engineering estimate based on best available 

data. 

CountMR,y = Count of meter/regulator runs surveyed at above grade transmissiondistribution transfer stations in year “y”. 

y = Year of data included in emission factor “EFs,MR,i” according to paragraph 

(q)(8)(iii) of this section. 

n = Number of years of data used to calculate emission factor “EFs,MR,i” 

according to paragraph (q)(8)(iii) of this section. 
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(iii) The emission factor “EFs,MR,i”, based on annual equipment leak surveys at above 

grade transmission-distribution transfer stations, must be calculated annually. If the facility has 

submitted a smaller number of annual reports than the duration of the selected cycle period (up to 

5 years), then all available data from the current year and previous years must be used in the 

emission calculation. After the first cycle is completed, the survey will continue on a rolling 

basis by including the measurements from the current calendar year and as many of the previous 

calendar years as are needed to complete the survey cycle. 

(r) Equipment leaks by population count. Population count and emission factors. This 

paragraph applies to emissions sources listed in §98.232 (c)(21), (f)(5), (g)(3), (h)(4), (i)(2), 

(i)(3), (i)(4), (i)(5), and (i)(6) on streams with gas content greater than 10 percent CH4 plus CO2

by weight. Emissions sources in streams with gas content less than or equal to 10 percent CH4

plus CO2 by weight are exempt from the requirements of this paragraph (q) and do not need to be 

reported. Tubing systems equal to or less than one half inch diameter are exempt from the 

requirements of paragraph (r) of this section and do not need to be reported. CalculateYou must 

calculate emissions from all emission sources listed in this paragraph using Equation W-3132A

of this section., except for natural gas distribution facility emission sources listed in § 

98.232(i)(3). Natural gas distribution facility emission sources listed in § 98.232(i)(3) must 

calculate emissions using Equation W-32b and according to paragraph (r)(6) of this section. 

Es,e,i Counte *EFs,e *GHGi *Te (Eq. W-32A) 

Es,MR,i CountMR *EFs,MR,i *Tw,avg 31 (Eq. W-32B) 

Where: 

Comment [EPA10]: Proposed: Equation Revised 

and Renumbered. 

Comment [EPA11]: Proposed New Equation. 
Page 96 of 214 

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puroposes only. We have taken steps to ensure the accuracy of this version, but it is not the official version. 

Es,e,i = Annual volumetric GHG emissions at of GHGi from the emission source type 

in standard conditions from each component type in cubic feet. The emission 

source type may be a component (e.g. connector, open-ended line, etc.), 

below grade metering-regulating station, below grade transmissiondistribution transfer station, distribution main, or distribution service.

Es,MR,i = Annual volumetric emissions of GHGi from all meter/regulator runs at above 

grade metering regulating stations that are not above grade transmission 

distribution transfer stations, in standard cubic feet. 

CountsCounte = Total number of this type ofthe emission source type at the facility. For 

onshore petroleum and natural gas production facilities, average component 

counts are provided by major equipment piece in Tables W-1B and Table W1C of this subpart. Use average component counts as appropriate for 

operations in Eastern and Western U.S., according to Table W-1D of this 

subpart. Underground natural gas storage shallfacilities must count the 

componentseach component listed for population emission factors in Table 

W-4. of this subpart. LNG Storage shallstorage facilities must count the 

number of vapor recovery compressors. LNG import and export 

shallfacilities must count the number of vapor recovery compressors. Natural 

gas distribution shallfacilities must count the meter/regulator runs: (1) the 

number of distribution services by material type; (2) miles of distribution 

mains by material type; and (3) number of below grade metering-regulating 

stations, by pressure type; as describedlisted in paragraph (r)(6)Table W-7 of 

this sectionsubpart. 

CountMR = Total number of meter/regulator runs at above grade metering-regulating 

stations that are not above grade transmission-distribution transfer stations. 

EFs,e = Population emission factor for the specific componentemission source type, 

as listed in Table W-1A and Tables W-31A and W-4 through Table W-7 of 

this subpart. Use appropriate population emission factor for operations in 

Eastern and Western U.S., according to Table W-1D of this subpart. EF for 

meter/regulator runs at above grade metering-regulating stations is 

determined in Equation W-32 of this section.

EFs,MR,i = Meter/regulator run population emission factor for GHGi based on all 

surveyed above grade transmission-distribution transfer stations over “n” 

years, in standard cubic feet of GHGi per operational hour of all 

meter/regulator runs., as determined in Equation W-31. 

GHGi = For onshore petroleum and natural gas production facilities, concentration of 

GHGi, CH4, or CO2, in produced natural gas as defined in paragraph (u)(2) of 

this section; for onshore natural gas transmission compression and 

underground natural gas storage, GHGi equals 0.975 for CH4 and 1.1 × 10−2

for CO2; for LNG storage and LNG import and export equipment, GHGi

equals 1 for CH4 and 0 for CO2; and for natural gas distribution, GHGi equals 

1 for CH4 and 1.1 × 10−2

CO2. 
Page 97 of 214 

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TsTe = Average estimated time that each componentemission source type associated 

with the equipment leak emission was operational in the calendar year, in 

hours, using engineering estimate based on best available data. 

Tw,avg = Average estimated time that each meter/regulator run was operational in the 

calendar year, in hours per meter/regulator run, using engineering estimate 

based on best available data. 

(1) Calculate both CH4 and CO2 mass emissions from volumetric emissions using 

calculations in paragraph (v) of this section. 

(2) Onshore petroleum and natural gas production facilities shallmust use the appropriate 

default whole gas population emission factors listed in Table W-1A of this subpart for equipment 

leaks from valves, connectors, open ended lines, pressure relief valves, pump, flanges, and other. 

Major equipment and components associated with gas wells are considered gas service 

components in reference to Table W-1A of this subpart and major natural gas equipment in 

reference to Table W-1B of this subpart. Major equipment and components associated with crude 

oil wells are considered crude service components in reference to Table W-1A of this subpart 

and major crude oil equipment in reference to Table W-1C of this subpart. Where facilities 

conduct EOR operations the emissions factor listed in Table W-1A of this subpart shall be used 

to estimate all streams of gases, including recycle CO2 stream. The component count can be 

determined using either of the methodologiescalculation methods described in this paragraph 

(r)(2). The same methodologycalculation method must be used for the entire calendar year. 

(i) Component Count Methodology 1. For all onshore petroleum and natural gas 

production operations in the facility perform the following activities: 

(A) Count all major equipment listed in Table W-1B and Table W-1C of this subpart. For 

meters/piping, use one meters/piping per well-pad. 
Page 98 of 214 

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(B) Multiply major equipment counts by the average component counts listed in Table 

W-1B and W-1C of this subpart for onshore natural gas production and onshore oil production, 

respectively. Use the appropriate factor in Table W-1A of this subpart for operations in Eastern 

and Western U.S. according to the mapping in Table W-1D of this subpart. 

(ii) Component Count Methodology 2. Count each component individually for the 

facility. Use the appropriate factor in Table W-1A of this subpart for operations in Eastern and 

Western U.S. according to the mapping in Table W-1D of this subpart. 

(3) Underground natural gas storage facilities for storage wellheads shallmust use the 

appropriate default total hydrocarbon population emission factors for storage wellheads in gas 

service listed in Table W-4 of this subpart for equipment leak from connectors, valves, pressure 

relief valves, and open ended lines. 

(4) LNG storage facilities shallmust use the appropriate default methane population 

emission factorsfactor for LNG storage compressors in gas service listed in Table W-5 of this 

subpart for equipment leak from vapor recovery compressors. 

(5) LNG import and export facilities shallmust use the appropriate default methane 

population emission factor for LNG terminal compressors in gas service listed in Table W-6 of 

this subpart for equipment leak from vapor recovery compressors. 

(6) Natural gas distribution facilities shallmust use the appropriate methane emission 

factors as described in paragraph (r)(6) of this section. 

(i) Below grade metering-regulating stations;, distribution mains;, and distribution 

services, shall must use the appropriate default methane population emission factors listed in 

Table W-7 of this subpart. Below grade T-Dtransmission-distribution transfer stations shallmust

use the emission factor for below grade metering-regulating stations. 
Page 99 of 214 

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(ii) Emissions from all above grade metering-regulating stations (including above grade 

TD transfer stations) shall be calculated by applying the emission factor calculated in Equation 

W-32 and the total count of meter/regulator runs at all above grade metering-regulating stations 

(inclusive of TD transfer stations) to Equation W-31. The facility wide emission factor in 

Equation W-32 will be calculated by using the total volumetric GHG emissions at standard 

conditions for all equipment leak sources calculated in Equation W-30B in paragraph (q)(8) of 

this section and the count of meter/regulator runs located at above grade transmissiondistribution transfer stations that were monitored over the years that constitute one complete 

cycle as per paragraph (q)(8)(i) of this section. A meter on a regulator run is considered one 

meter/regulator run. Reporters that do not have above grade T-D transfer stations shall report a 

count of above grade metering-regulating stations only and do not have to comply with 

§98.236(c)(16)(xix).Above grade metering-regulating stations (that are not above grade 

transmission-distribution transfer stations) must use the meter/regulator run population emission 

factor calculated in Equation W-31. Natural gas distribution facilities that do not have above 

grade transmission-distribution transfer stations are not required to calculate emissions for above 

grade metering-regulating stations.

Count

E

EF s,i  8760  (Eq. W-32)

Where:

EF = Facility emission factor for a meter/regulator run per component type at 

above grade metering-regulating for GHGi in cubic feet per meter/regulator 

run per hour.

Es,i = Annual volumetric GHG i emissions, CO2 or CH4 at standard condition from 

each component type at all above grade TD transfer stations, from Equation 

W-30B.
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Count = Total number of meter/regulator runs at all TD transfer stations that were 

monitored over the years that constitute one complete cycle as per (q)(8)(i) of 

this section.

8760 = Conversion to hourly emissions

(s) Offshore petroleum and natural gas production facilities. Report CO2, CH4, and N2O 

emissions for offshore petroleum and natural gas production from all equipment leaks, vented 

emission, and flare emission source types as identified in the data collection and emissions 

estimation study conducted by BOEMRE in compliance with 30 CFR 250.302 through 304. 

(1) Offshore production facilities under BOEMRE jurisdiction shall report the same 

annual emissions as calculated and reported by BOEMRE in data collection and emissions 

estimation study published by BOEMRE referenced in 30 CFR 250.302 through 304 (GOADS). 

(i) For any calendar year that does not overlap with the most recent BOEMRE emissions 

study publication year, report the most recent BOEMRE reported emissions data published by 

BOEMRE referenced in 30 CFR 250.302 through 304 (GOADS). Adjust emissions based on the 

operating time for the facility relative to the operating time in the most recent BOEMRE 

published study. 

(ii) [Reserved] 

(2) Offshore production facilities that are not under BOEMRE jurisdiction shallmust use 

the most recent monitoring methods and calculation methodologies published by BOEMRE 

referenced in 30 CFR 250.302 through 304 to calculate and report annual emissions (GOADS). 

(i) For any calendar year that does not overlap with the most recent BOEMRE emissions 

study publication, you may report the most recently reported emissions data submitted to 

demonstrate compliance with this subpart of part 98, with emissions adjusted based on the 

operating time for the facility relative to operating time in the previous reporting period. 
Page 101 of 214 

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(ii) [Reserved] 

(3) If BOEMRE discontinues or delays their data collection effort by more than 4 years, 

then offshore reporters shall once in every 4 years use the most recent BOEMRE data collection 

and emissions estimation methods to report estimate emissions. These emission estimates would 

be used to report emissions from the facility sources as required in paragraph (s)(1)(i) of this 

section. 

(4) For either first or subsequent year reporting, offshore facilities either within or outside 

of BOEMRE jurisdiction that were not covered in the previous BOEMRE data collection cycle 

shallmust use the most recent BOEMRE data collection and emissions estimation methods 

published by BOEMRE referenced in 30 CFR 250.302 through 304 to calculate and report 

emissions (GOADS) to report emissions. 

(t) GHG volumetric emissions using actual conditions. If equation parameters in §98.233 

are already at standard conditions, which results in volumetric emissions at standard conditions, 

then this paragraph does not apply. Calculate volumetric emissions at standard conditions as 

specified in paragraphs (t)(1) or (2) of this section, with actual pressure and temperature 

determined by engineering estimates based on best available data unless otherwise specified. 

(1) Calculate natural gas volumetric emissions at standard conditions using actual natural 

gas emission temperature and pressure, and Equation W-33 of this section for conversions of Ea,n

or conversions of FRa (whether sub-sonic or sonic). 

 

  a s a

a n s a

s n T P Z

E T P

E

459.67 * *

, * 459.67 * , 

  (Eq. W-33) 

Where: 

Comment [EPA12]: Proposed Revised 

Equation. 
Page 102 of 214 

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Es,n = Natural gas volumetric emissions at standard temperature and pressure (STP) 

conditions in cubic feet, except Es,n equals FRs,p for each well p when 

calculating either subsonic or sonic flowrates under 98.233(g). 

Ea,n = Natural gas volumetric emissions at actual conditions in cubic feet, except 

Ea,n equals FRa,p for each well p when calculating either subsonic or sonic 

flowrates under 98.233(g). 

Ts = Temperature at standard conditions (60 °F). 

Ta = Temperature at actual emission conditions (°F). 

Ps = Absolute pressure at standard conditions (14.7 psia). 

Pa = Absolute pressure at actual conditions (psia). 

Za = Compressibility factor at actual conditions for natural gas. You may use 1 if 

the temperature is above -10 degrees Fahrenheit and pressure is below 5 

atmospheres, or if the compressibility factor at the actual temperature and 

pressure is 0.98 or greater. 

(2) Calculate GHG volumetric emissions at standard conditions using actual GHG 

emissions temperature and pressure, and Equation W-34 of this section. 

 

  a s a

a i s a

s i T P Z

E T P

E

459.67 * *

* 459.67 * ,

, 

  (Eq. W-34) 

Where: 

Es,i = GHG i volumetric emissions at standard temperature and pressure (STP) 

conditions in cubic feet. 

Ea,i = GHG i volumetric emissions at actual conditions in cubic feet. 

Ts = Temperature at standard conditions (60 °F). 

Ta = Temperature at actual emission conditions (°F). 

Ps = Absolute pressure at standard conditions (14.7 psia). 

Pa = Absolute pressure at actual conditions (psia). 

Za = Compressibility factor at actual conditions for GHG i. You may use 1 if the 

compressibility factor at the actual temperature and pressure is 0.98 or 

greater. 

Comment [EPA13]: Proposed Revised 

Equation. 
Page 103 of 214 

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(3) Reporters using 68 °F for standard temperature may use the ratio 519.67/527.67 to 

convert volumetric emissions from 68 °F to 60 °F. 

(u) GHG volumetric emissions. at standard conditions. Calculate GHG volumetric 

emissions at standard conditions as specified in paragraphs (u)(1) and (2) of this section, with 

mole fraction of GHGs in the natural gas determined by engineering estimate based on best 

available data unless otherwise specified. 

(1) Estimate CH4 and CO2 emissions from natural gas emissions using Equation W-35 of 

this section. 

 (Eq. W-35) 

Where: 

Es,i = GHG i (either CH4 or CO2 ) volumetric emissions at standard conditions in 

cubic feet. 

Es,n = Natural gas volumetric emissions at standard conditions in cubic feet. 

Mi = Mole fraction of GHG i in the natural gas. 

(2) For Equation W-35 of this section, the mole fraction, Mi, shall be the annual average 

mole fraction for each sub-basin category or facility, as specified in paragraphs (u)(2)(i) through 

(vii) of this section. 

(i) GHG mole fraction in produced natural gas for onshore petroleum and natural gas 

production facilities. If you have a continuous gas composition analyzer for produced natural 

gas, you must use an annual average of these values for determining the mole fraction. If you do 

not have a continuous gas composition analyzer, then you must use an annual average gas 

composition based on your most recent available analysis of the sub-basin category or facility, as 

applicable to the emission source. 

Es,i  Es,n * M i
Page 104 of 214 

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(ii) GHG mole fraction in feed natural gas for all emissions sources upstream of the demethanizer or dew point control and GHG mole fraction in facility specific residue gas to 

transmission pipeline systems for all emissions sources downstream of the de-methanizer 

overhead or dew point control for onshore natural gas processing facilities. For onshore natural 

gas processing plants that solely fractionate a liquid stream, use the GHG mole percent in feed 

natural gas liquid for all streams. If you have a continuous gas composition analyzer on feed 

natural gas, you must use these values for determining the mole fraction. If you do not have a 

continuous gas composition analyzer, then annual samples must be taken according to methods 

set forth in §98.234(b). 

(iii) GHG mole fraction in transmission pipeline natural gas that passes through the 

facility for the onshore natural gas transmission compression industry segment. You may use 

either a default 95 percent methane and 1 percent carbon dioxide fraction for GHG mole fraction 

in natural gas. or site specific engineering estimates based on best available data. 

(iv) GHG mole fraction in natural gas stored in the underground natural gas storage 

industry segment. You may use a default 95 percent methane and 1 percent carbon dioxide 

fraction for GHG mole fraction in natural gas. 

(v) GHG mole fraction in natural gas stored in the LNG storage industry segment. You 

may use either a default 95 percent methane and 1 percent carbon dioxide fraction for GHG mole 

fraction in natural gas or site specific engineering estimates based on best available data. 

(vi) GHG mole fraction in natural gas stored in the LNG import and export industry 

segment. For export facilities that receive gas from transmission pipelines, you may use either a 

default 95 percent methane and 1 percent carbon dioxide fraction for GHG mole fraction in 

natural gas or site specific engineering estimates based on best available data. 
Page 105 of 214 

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(vii) GHG mole fraction in local distribution pipeline natural gas that passes through the 

facility for natural gas distribution facilities. You may use a default 95 percent methane and 1 

percent carbon dioxide fraction for GHG mole fraction in natural gas or site specific engineering 

estimates based on best available data. 

(v) GHG mass emissions. Calculate GHG mass emissions in carbon dioxide 

equivalentmetric tons by converting the GHG volumetric emissions at standard conditions into 

mass emissions using Equation W-36 of this section. 

3

, * *10 Massi

 Es i  i (Eq. W-36) 

Where: 

Massi = GHGi (either CH4, CO2, or N2O) mass emissions in metric tons CO2e. 

Es,i = GHGi (either CH4, CO2, or N2O) volumetric emissions at standard conditions, 

in cubic feet. 

Pi = Density of GHGi. Use 0.0526 kg/ft3

 for CO2 and N2O, and 0.0192 kg/ft3 for 

CH4 at 60 °F and 14.7 psia. 

GWP = Global warming potential, 1 for CO2, 25 for CH4, and 298 for N2O.

(w) EOR injection pump blowdown. Calculate CO2 pump blowdown emissions from 

each EOR injection pump system as follows: 

(1) Calculate the total injection pump system volume in cubic feet (including pipelines, 

manifolds and vessels) between isolation valves. 

(2) Retain logs of the number of blowdowns per calendar year. 

(3) Calculate the total annual ventingCO2 emissions from each EOR injection pump 

system using Equation W-37 of this section: 

3

2 2 * * * *10  Mass CO  N Vv Rc GHG CO (Eq. W-37) 

Where: 
Page 106 of 214 

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MassCO2 = Annual EOR injection gas ventingpump system emissions in metric tons 

from blowdowns. 

N = Number of blowdowns for the equipmentEOR injection pump system in the 

calendar year. 

Vv = Total volume in cubic feet of blowdown equipmentEOR injection pump 

system chambers (including pipelines, manifolds and vessels) between 

isolation valves. 

Rc = Density of critical phase EOR injection gas in kg/ft3

. You may use an 

appropriate standard method published by a consensus-based standards 

organization if such a method exists or you may use an industry standard 

practice to determine density of super critical EOR injection gas. 

GHGCO2 = Mass fraction of CO2 in critical phase injection gas. 

1 × 10−3

 = Conversion factor from kilograms to metric tons. 

(x) EOR hydrocarbon liquids dissolved CO2. Calculate CO2 emissions downstream of the 

storage tank from dissolved CO2 in hydrocarbon liquids produced through EOR operations as 

follows: 

(1) Determine the amount of CO2 retained in hydrocarbon liquids after flashing in 

tankage at STP conditions. Annual samples of hydrocarbon liquids downstream of the storage 

tank must be taken according to methods set forth in §98.234(b) to determine retention of CO2 in 

hydrocarbon liquids immediately downstream of the storage tank. Use the annual analysis for the 

calendar year. 

(2) Estimate emissions using Equation W-38 of this section. 

2 * M CO hl hl ass S V  (Eq. W-38) 

Where: 

MassCO2 = Annual CO2 emissions from CO2 retained in hydrocarbon liquids produced 

through EOR operations beyond tankage, in metric tons. 

Shl = Amount of CO2 retained in hydrocarbon liquids downstream of the storage 

tank, in metric tons per barrel, under standard conditions. 
Page 107 of 214 

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Vhl = Total volume of hydrocarbon liquids produced at the EOR operations in 

barrels in the calendar year. 

(y) [Reserved] 

(z) Onshore petroleum and natural gas production and natural gas distribution 

combustion emissions. Calculate CO2, CH4, and N2O combustion-related emissions from 

stationary or portable equipment, except as specified in paragraph (z)(3) and (z)(4) of this 

section, as follows: 

(1) If a fuel combusted in the stationary or portable equipment is listed in Table C-1 of 

subpart C of this part, or is a blend containing one or more fuels listed in Table C-1, calculate 

emissions according to paragraph (z)(1)(i) of this section. If the fuel combusted is natural gas and 

is of pipeline quality specification and has a minimum high heat value of 950 Btu per standard 

cubic foot, use the calculation methodology described in paragraph (z)(1)(i) of this section and 

you may use the emission factor provided for natural gas as listed in Table C-1. If the fuel is 

natural gas, and is not pipeline quality or has a high heat value of less than 950 Btu per standard 

cubic feet, calculate emissions according to paragraph (z)(2) of this section. If the fuel is field 

gas, process vent gas, or a blend containing field gas or process vent gas, calculate emissions 

according to paragraph (z)(2) of this section. 

(i) For fuels listed in Table C-1 or a blend containing one or more fuels listed in Table C1, calculate CO2, CH4, and N2O emissions according to any Tier listed in subpart C of this part. 

You must follow all applicable calculation requirements for that tier listed in § 98.33, any 

monitoring or QA/QC requirements listed for that tier in § 98.34, any missing data procedures 

specified in 98.35, and any recordkeeping requirements specified in § 98.37. 
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(ii) Emissions from fuel combusted in stationary or portable equipment at onshore natural 

gas and petroleum production facilities and at natural gas distribution facilities will be reported 

according to the requirements specified in § 98.236(c)(19) and not according to the reporting 

requirements specified in subpart C of this part. 

(2) For fuel combustion units that combust field gas, process vent gas, a blend containing 

field gas or process vent gas, or natural gas that is not of pipeline quality or that has a high heat 

value of less than 950 Btu per standard cubic feet, calculate combustion emissions as follows: 

(i) You may use company records to determine the volume of fuel combusted in the unit 

during the reporting year. 

(ii) If you have a continuous gas composition analyzer on fuel to the combustion unit, 

you must use these compositions for determining the concentration of gas hydrocarbon 

constituent in the flow of gas to the unit. If you do not have a continuous gas composition 

analyzer on gas to the combustion unit, you must use the appropriate gas compositions for each 

stream of hydrocarbons going to the combustion unit as specified in the applicable paragraph in 

(u)(2) of this section. 

(iii) Calculate GHG volumetric emissions at actual conditions using Equations W-39A 

and W-39B of this section: 



 

5

1

, 2 ( * 2 ) * * * j

Ea CO Va YCO  Va Y j R j (Eq. W-39A) 

  , 4 4 * 1 * Ea CH  Va   YCH (Eq. W-39B) 

Where: 

Ea,CO2 = Contribution of annual CO2 emissions from portable or stationary fuel 

combustion sources in cubic feet, under actual conditions. 
Page 109 of 214 

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Va = Volume of gas sent to combustion unit in actual cubic feet, during the year. 

YCO2 = ConcentrationMole fraction of CO2 constituent in gas sent to combustion 

unit. 

Ea,CH4 = Contribution of annual CH4 emissions from portable or stationary fuel 

combustion sources in cubic feet, under actual conditions. 

η = Fraction of gas combusted for portable and stationary equipment determined 

using engineering estimation. For internal combustion devices, a default of 

0.995 can be used. 

Yj = ConcentrationMole fraction of gas hydrocarbon constituents j (such as 

methane, ethane, propane, butane, and pentanes plus) in gas sent to 

combustion unit. 

Rj = Number of carbon atoms in the gas hydrocarbon constituent j; 1 for methane, 

2 for ethane, 3 for propane, 4 for butane, and 5 for pentanes plus, in gas sent 

to combustion unit. 

YCH4 = ConcentrationMole fraction of methane constituent in gas sent to combustion 

unit. 

(iv) Calculate GHG volumetric emissions at standard conditions using calculations in 

paragraph (t) of this section. 

(v) Calculate both combustion-related CH4 and CO2 mass emissions from volumetric 

CH4 and CO2 emissions using calculation in paragraph (v) of this section. 

(vi) Calculate N2O mass emissions using Equation W-40 of this section. 

Mass N O     Fuel  HHV  EF 3

2 1 10 (Eq. W-40)

Where: 

MassN2O = Annual N2O emissions from the combustion of a particular type of fuel 

(metric tons CO2e). 

Fuel = MassAnnual mass or volume of the fuel combusted (mass or volume per 

year, choose appropriately to be consistent with the units of HHV). 

HHV = Higher heating value of fuel, mmBtu/unit of fuel (in units consistent with the 

fuel quantity combusted). For the higher heating value for field gas or process 

vent gas, use 1.235 × 10−3 mmBtu/scf for HHV. 

Comment [EPA14]: Proposed Revised Equation.
Page 110 of 214 

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EF = Use 1.0 × 10−4

 kg N2O/mmBtu. 

1 × 10−3

 = Conversion factor from kilograms to metric tons. 

GWP = Global warming potential, as listed in Table A-1 of subpart A of this part.

(3) External fuel combustion sources with a rated heat capacity equal to or less than 5 

mmBtu/hr do not need to report combustion emissions or include these emissions for threshold 

determination in §98.231(a). You must report the type and number of each external fuel 

combustion unit. 

(4) Internal fuel combustion sources, not compressor-drivers, with a rated heat capacity 

equal to or less than 1 mmBtu/hr (or the equivalent of 130 horsepower), do not need to report 

combustion emissions or include these emissions for threshold determination in §98.231(a). You 

must report the type and number of each internal fuel combustion unit. 

§98.234 Monitoring and QA/QC requirements. 

The GHG emissions data for petroleum and natural gas emissions sources must be quality 

assured as applicable as specified in this section. Offshore petroleum and natural gas production 

facilities shall adhere to the monitoring and QA/QC requirements as set forth in 30 CFR 250. 

(a) You must use any of the methods described as follows in this paragraph to conduct 

leak detection(s) of equipment leaks and through-valve leakage from all source types listed in 

§ 98.233(k), (o), (p) and (q) that occur during a calendar year, except as provided in paragraph 

(a)(4) of this section. 

(1) Optical gas imaging instrument. Use an optical gas imaging instrument for equipment 

leak detection in accordance with 40 CFR part 60, subpart A, § 60.18 of the Alternative work 

practice for monitoring equipment leaks, § 60.18(i)(1)(i); § 60.18(i)(2)(i) except that the 

monitoring frequency shall be annual using the detection sensitivity level of 60 grams per hour 
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as stated in 40 CFR Part 60, subpart A, Table 1: Detection Sensitivity Levels; § 60.18(i)(2)(ii) 

and (iii) except the gas chosen shall be methane, and § 60.18(i)(2)(iv) and (v); § 60.18(i)(3); 

§ 60.18(i)(4)(i) and (v); including the requirements for daily instrument checks and distances, 

and excluding requirements for video records. Any emissions detected by the optical gas imaging 

instrument is a leak unless screened with Method 21 (40 CFR part 60, appendix A-7) monitoring, 

in which case 10,000 ppm or greater is designated a leak. In addition, you must operate the 

optical gas imaging instrument to image the source types required by this subpart in accordance 

with the instrument manufacturer’s operating parameters. Unless using methods in paragraph 

(a)(2) of this section, an optical gas imaging instrument must be used for all source types that are 

inaccessible and cannot be monitored without elevating the monitoring personnel more than 2 

meters above a support surface. 

(2) Method 21. Use the equipment leak detection methods in 40 CFR part 60, appendix 

A-7, Method 21. If using Method 21 monitoring, if an instrument reading of 10,000 ppm or 

greater is measured, a leak is detected. Inaccessible emissions sources, as defined in 40 CFR part 

60, are not exempt from this subpart. Owners or operators must use alternative leak detection 

devices as described in paragraph (a)(1) or (a)(2) of this section to monitor inaccessible 

equipment leaks or vented emissions. 

(3) Infrared laser beam illuminated instrument. Use an infrared laser beam illuminated 

instrument for equipment leak detection. Any emissions detected by the infrared laser beam 

illuminated instrument is a leak unless screened with Method 21 monitoring, in which case 

10,000 ppm or greater is designated a leak. In addition, you must operate the infrared laser beam 

illuminated instrument to detect the source types required by this subpart in accordance with the 

instrument manufacturer’s operating parameters. 
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(4) [Reserved] 

(5) Acoustic leak detection device. Use the acoustic leak detection device to detect 

through-valve leakage. When using the acoustic leak detection device to quantify the throughvalve leakage, you must use the instrument manufacturer’s calculation methods to quantify the 

through-valve leak. When using the acoustic leak detection device, if a leak of 3.1 scf per hour or 

greater is calculated, a leak is detected. In addition, you must operate the acoustic leak detection 

device to monitor the source valves required by this subpart in accordance with the instrument 

manufacturer’s operating parameters. Acoustic stethoscope type devices designed to detect 

through valve leakage when put in contact with the valve body and that provide an audible leak 

signal but do not calculate a leak rate can be used to identify non-leakers with subsequent 

measurement required to calculate the rate if through-valve leakage is identified. Leaks are 

reported if a leak rate of 3.1 scf per hour or greater is measured. 

(b) You must operate and calibrate all flow meters, composition analyzers and pressure 

gauges used to measure quantities reported in § 98.233 according to the procedures in § 98.3(i) 

and the procedures in paragraph (b) of this section. You may use an appropriate standard method 

published by a consensus-based standards organization if such a method exists or you may use 

an industry standard practice. Consensus-based standards organizations include, but are not 

limited to, the following: ASTM International, the American National Standards Institute 

(ANSI), the American Gas Association (AGA), the American Society of Mechanical Engineers 

(ASME), the American Petroleum Institute (API), and the North American Energy Standards 

Board (NAESB). 

(c) Use calibrated bags (also known as vent bags) only where the emissions are at nearatmospheric pressures and below the maximum temperature specified by the vent bag 
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manufacturer such that the bag is safe to handle. The bag opening must be of sufficient size that 

the entire emission can be tightly encompassed for measurement till the bag is completely filled. 

(1) Hold the bag in place enclosing the emissions source to capture the entire emissions 

and record the time required for completely filling the bag. If the bag inflates in less than one 

second, assume one second inflation time. 

(2) Perform three measurements of the time required to fill the bag, report the emissions 

as the average of the three readings. 

(3) Estimate natural gas volumetric emissions at standard conditions using calculations in 

§ 98.233(t). 

(4) Estimate CH4 and CO2 volumetric and mass emissions from volumetric natural gas 

emissions using the calculations in § 98.233(u) and (v). 

(d) Use a high volume sampler to measure emissions within the capacity of the 

instrument. 

(1) A technician following manufacturer instructions shall conduct measurements, 

including equipment manufacturer operating procedures and measurement methodologies 

relevant to using a high volume sampler, including positioning the instrument for complete 

capture of the equipment leak without creating backpressure on the source. 

(2) If the high volume sampler, along with all attachments available from the 

manufacturer, is not able to capture all the emissions from the source then use anti-static wraps 

or other aids to capture all emissions without violating operating requirements as provided in the 

instrument manufacturer’s manual. 
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(3) Estimate natural gas volumetric emissions at standard conditions using calculations in 

§ 98.233(t). Estimate CH4 and CO2 volumetric and mass emissions from volumetric natural gas 

emissions using the calculations in § 98.233(u) and (v). 

(4) Calibrate the instrument at 2.5 percent methane with 97.5 percent air and 100 percent 

CH4 by using calibrated gas samples and by following manufacturer’s instructions for calibration. 

(e) Peng Robinson Equation of State means the equation of state defined by Equation W41 of this section: 

2 2 V 2bV b

a

V b

RT

p

m m  m     

 (Eq. W-41) 

Where: 

p = Absolute pressure. 

R = Universal gas constant. 

T = Absolute temperature. 

Vm = Molar volume. 

 a = c

c

p

R T

2 2 0.45724

 b = c

c

p

0.7780RT

α =   2

2 1 0.37464 1.54226 0.26992 1 































    Tc

T  

Where: 

ω = Acentric factor of the species. 

Tc = Critical temperature. 
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Pc = Critical pressure. 

(f) Special reporting provisions 

(1) Best available monitoring methods. EPA will allow owners or operators to use best 

available monitoring methods for parameters in § 98.233 Calculating GHG Emissions as 

specified in paragraphs (f)(2), (f)(3), and (f)(4) of this section. If the reporter anticipates the 

potential need for best available monitoring for sources for which they need to petition EPA and 

the situation is unresolved at the time of the deadline, reporters should submit written notice of 

this potential situation to EPA by the specified deadline for requests to be considered. EPA 

reserves the right to review best available monitoring method requests submitted after the 

deadlines specified in this section, and will consider requests which demonstrate unique or 

unusual circumstances unforeseen at the time of the applicable best available monitoring method 

deadline. The Administrator reserves the right to request further information in regard to all 

petition requests. The owner or operator must use the calculation methodologies and equations in 

§ 98.233 Calculating GHG Emissions. Best available monitoring methods means any of the 

following methods specified in paragraph (f)(1) of this section:

(i) Monitoring methods currently used by the facility that do not meet the specifications 

of this subpart.

(ii) Supplier data.

(iii) Engineering calculations.

(iv) Other company records.

(2) Best available monitoring methods for well-related emissions. During January 1, 2011 

through December 31, 2011, owners and operators may use best available monitoring methods 
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for any well-related data that cannot reasonably be measured according to the monitoring and 

QA/QC requirements of this subpart. These well-related sources are:

(i) Gas well venting during well completions and workovers with hydraulic fracturing as 

specified in § 98.233(g).

(ii) Well testing venting and flaring as specified in § 98.233(l).

(3) Best available monitoring methods for specified activity data. During January 1, 2011 

through December 31, 2011, owners or operators may use best available monitoring methods for 

activity data as listed below that cannot reasonably be obtained according to the monitoring and 

QA/QC requirements of this subpart. These sources are:

(i) Cumulative hours of venting, days, or times of operation in § 98.233(e), (f), (g), (h), 

(l), (o), (p), (q), and (r).

(ii) Number of blowdowns, completions, workovers, or other events in § 98.233(f), (g), 

(h), (i), and (w).

(iii) Cumulative volume produced, volume input or output, or volume of fuel used in 

paragraphs § 98.233(d), (e), (j), (k), (l), (m), (n), (x), (y), and (z).

(4) Best available monitoring methods for leak detection and measurement. During 

January 1, 2011 through December 31, 2011, owners or operators may use best available 

monitoring methods for sources requiring leak detection and/or measurement that cannot 

reasonably be obtained according to the monitoring and QA/QC requirements of this part. These 

sources include:

(i) Reciprocating compressor rod packing venting in onshore natural gas processing, 

onshore natural gas transmission compression, underground natural gas storage, LNG storage, 
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and LNG import and export equipment as specified in § 98.232(d)(1), (e)(1), (f)(1), (g)(1), and 

(h)(1).

(ii) Centrifugal compressor wet seal oil degassing venting in onshore natural gas 

processing, onshore natural gas transmission compression, underground natural gas storage, 

LNG storage, and LNG import and export equipment as specified in § 98.232(d)(2), (e)(2), 

(f)(2), (g)(2), and (h)(2).

(iii) Acid gas removal vent stacks in onshore petroleum and natural gas production and 

onshore natural gas processing as specified in § 98.232(c)(17) and (d)(6).

(iv) Equipment leak emissions from valves, connectors, open ended lines, pressure relief 

valves, block valves, control valves, compressor blowdown valves, orifice meters, other meters, 

regulators, vapor recovery compressors, centrifugal compressor dry seals, and/or other 

equipment leaks in onshore natural gas processing, onshore natural gas transmission 

compression, underground natural gas storage, LNG storage, LNG import and export equipment, 

and natural gas distribution as specified in § 98.232(d)(7), (e)(7), (f)(5), (g)(3), (h)(4), and (i)(1).

(v) Condensate (oil and/or water) storage tanks in onshore natural gas transmission 

compression as specified in § 98.232(e)(3).

(5) Requests for the use of best available monitoring methods. 

(i) No request or approval by the Administrator is necessary to use best available 

monitoring methods between January 1, 2011 and December 31, 2011 for the sources specified 

in paragraph (f)(2) of this section.

(ii) No request or approval by the Administrator is necessary to use best available 

monitoring methods between January 1, 2011 and December 31, 2011 for sources specified in 

paragraph (f)(3) of this section.
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(iii) No request or approval by the Administrator is necessary to use best available 

monitoring methods between January 1, 2011 and December 31, 2011 for sources specified in 

paragraph (f)(4) of this section.

(iv) No request or approval by the Administrator is necessary to use best available 

monitoring methods for data that cannot reasonably be obtained between January 1, 2011 and 

December 31, 2011 for sources not listed in paragraph (f)(2), (f)(3), and (f)(4) of this section.

(6)-(7) [Reserved]

(8) Requests for extension of the use of best available monitoring methods beyond 2011 

for sources listed in paragraphs (f)(2), (f)(3), (f)(4), and (f)(5)(iv) of this section 

(i) Timing of request. EPA does not anticipate a need for best available monitoring 

methods beyond 2011, but for all reporting years after 2011, best available monitoring methods 

will be considered for unique or unusual circumstances which include data collection methods 

that do not meet safety regulations, technical infeasibility, or counter to other local, State, or 

Federal regulations. For use of best available monitoring methods in 2012, an initial notice of 

intent to request best available monitoring methods must be submitted by December 31, 2011. 

Any notice of intent submitted prior to the effective date of this rule cannot be used to meet this 

December 31, 2011 deadline; a new notice of intent must be signed and submitted by the 

designated representative. In addition to the initial notification of intent, owners or operators 

must also submit an extension request containing the information specified in 98.234(f)(8)(ii) by 

March 30, 2012. Any best available monitoring methods request submitted prior to the effective 

date of this rule cannot be used to meet the March 30, 2012 deadline; a new best available 

monitoring methods request must be signed and submitted by the designated representative. 

Owners or operators that submit both a timely notice of intent and extension request consistent 
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with 98.234(f)(8)(ii) can automatically use best available monitoring method through June 30, 

2012, for the specific parameters identified in their notification of intent and best available 

monitoring methods request regardless of whether the best available monitoring methods request 

is ultimately approved. Owners or operators that submit a notice of intent but do not follow up 

with a best available monitoring methods request by March 30, 2012 cannot use best available 

monitoring methods in 2012. For 2012, when an owner or operator has submitted a notice of 

intent and a subsequent best available monitoring method extension request, use of best available 

monitoring methods will be valid, upon approval by the Administrator, until the date indicated in 

the approval or until December 31, 2012, whichever is earlier. For reporting years after 2012, a

new request to use best available monitoring methods must be submitted by June 30th of the year 

prior to the reporting year for which use of best available monitoring methods is sought.

(ii) Content of request. Requests must contain the following information:

(A) A list of specific source categories and parameters for which the owner or operator is 

seeking use of best available monitoring methods.

(B) For each specific source for which an owner or operator is requesting use of best 

available monitoring methods, a description of the unique or unusual circumstances, such as data 

collection methods that do not meet safety regulations, technical infeasibility, or specific laws or 

regulations that are counter to data collection methods that conflict with each specific source.

(C) A detailed explanation and supporting documentation of how and when the owner or 

operator will comply with all of the subpart W reporting requirements for which use of best 

available monitoring methods are sought.

(iii) Approval criteria. To obtain approval to use best available monitoring methods after 

December 31, 2011, the owner or operator must submit a request demonstrating to the 

Formatted: Level 2
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Administrator's satisfaction that the owner or operator faces unique or unusual circumstances 

which include, by way of example and not in limitation, clearly demonstrated data collection 

methods that do not meet safety regulations, technical infeasibility, or counter to other local, 

State, or Federal regulations, along with the reasons the owner or operator cannot otherwise 

address the unique or unusual circumstances as required to be demonstrated in this 

paragraph.[Reserved]

(g) For the purposes of fulfilling requirements in 40 CFR 98.233(f) and (g) which require 

measurements to be taken every other year beginning in the first year of data collection, reporters 

have the option of taking the first measurement in 2012 to satisfy the requirements for the 2011-

2012 data collection cycle. 

(h) [Reserved]

For well venting for liquids unloading, if a monitoring period other than the full calendar 

year is used to determine the cumulative amount of time in hours of venting for each well (the 

term “Tp” in Equation W-7A and W-7B of § 98.233) or the number of unloading events per well 

(the term “Vp” in Equations W-8 and W-9 of § 98.233), then the monitoring period must begin 

before February 1 of the reporting year and must not end before December 1 of the reporting 

year. The end of one monitoring period must immediately precede the start of the next 

monitoring period for the next reporting year. All production days must be monitored and all 

venting accounted for. 

§98.235 Procedures for estimating missing data.

A complete record of all estimated and/or measured parameters used in the GHG 

emissions calculations is required. If data are lost or an error occurs during annual emissions 

estimation or measurements, you must repeat the estimation or measurement activity for those 
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sources as soon as possible, including in the subsequent calendar year if missing data are not 

discovered until after December 31 of the year in which data are collected, until valid data for 

reporting is obtained. Data developed and/or collected in a subsequent calendar year to substitute 

for missing data cannot be used for that subsequent year's emissions estimation. Where missing 

data procedures are used for the previous year, at least 30 days must separate emissions 

estimation or measurements for the previous year and emissions estimation or measurements for 

the current year of data collection. For missing data which are continuously monitored or 

measured, (for example flow meters), or for missing temperature or pressure data that are 

required under §98.236, the reporter may use best available data for use in emissions 

determinations. The reporter must record and report the basis for the best available data in these 

cases.

Except as specified in § 98.233, whenever a value of a parameter is unavailable for a 

GHG emission calculation required by this subpart (including, but not limited to, if a measuring 

device malfunctions during unit operation, a required gas sample is not taken, or activity data are 

not collected), you must follow the procedures specified in paragraphs (a) through (h) of this 

section, as applicable. 

(a) If you choose to take quarterly gas samples as allowed in § 98.233(d) in lieu of using 

a continuous gas analyzer, and there is a missing sample, you must substitute the average value 

of the last four samples for which data are available. 

(b) If you did not conduct monitoring as specified in §98.233(k) for a transmission 

storage tank(s), you must assume the vent stack(s) connected to the transmission storage tank(s) 

was leaking for the entire calendar year. 
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(c) For stationary and portable combustion sources that use the calculation methods of 

subpart C of this part, you must use the missing data procedures in subpart C of this part. 

(d) For each missing value of a parameter that should have been measured using a 

continuous flow meter, composition analyzer, thermocouple, or pressure gauge, you must 

substitute the arithmetic average of the quality-assured values of that parameter immediately 

preceding and immediately following the missing data incident. If the “after” value is not 

obtained by the end of the reporting year, you may use the “before” value for the missing data 

substitution. If, for a particular parameter, no quality-assured data are available prior to the 

missing data incident, you must use the first quality-assured value obtained after the missing data 

period as the substitute data value. A value is quality-assured according to the procedures 

specified in §98.234. 

(e) For the first six months of required data collection, facilities that become newly 

subject to this subpart W may use best engineering estimates for any data that cannot reasonably 

be measured or obtained according to the requirements of this subpart. 

(f) For the first six months of required data collection, facilities that are currently subject 

to this subpart W and that acquire new wells that were not previously subject to this subpart W 

may use best engineering estimates for any data related to those newly acquired wells that cannot 

reasonably be measured or obtained according to the requirements of this subpart. 

(g) For each missing value of any activity data not described in this section, you must 

substitute data value(s) using the best available estimate(s) of the parameter(s), based on all 

available process data (including, but not limited to, processing rates, operating hours). 
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(h) You must report information for all measured and substitute values of a parameter, 

and the procedures used to substitute an unavailable value of a parameter per the requirements in 

§ 98.236(bb). 

§98.236 Data reporting requirements. 

In addition to the information required by §98.3(c), each annual report must contain 

reported emissions and related information as specified in this section. 

(a) Report annual emissions in metric tons of CO2e for each GHG separately for each of 

the industry segments listed in paragraphs (a)(1) through (8) of this section. The annual report 

must include the information specified in paragraphs (a)(1) through (8) of this section for each 

applicable industry segment. The annual report must also include annual emissions totals, in 

metric tons of CO2e of each GHG, for each applicable industry segment listed in paragraphs 

(a)(1) through (a)(8) of this section, and each applicable emission source listed in paragraphs (b) 

through (z) of this section.

(1) Onshore petroleum and natural gas production. For the equipment/activities specified 

in paragraphs (a)(1)(i) through (a)(1)(xvii) of this section, report the information specified in the 

applicable paragraphs of this section. 

(i) Natural gas pneumatic devices. Report the information specified in paragraph (b) of 

this section. 

(ii) Natural gas driven pneumatic pumps. Report the information specified in paragraph 

(c) of this section. 

(iii) Acid gas removal units. Report the information specified in paragraph (d) of this 

section. 

(iv) Dehydrators. Report the information specified in paragraph (e) of this section. 
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(v) Liquids unloading. Report the information specified in paragraph (f) of this section. 

(vi) Completions and workovers with hydraulic fracturing. Report the information 

specified in paragraph (g) of this section. 

(vii) Completions and workovers without hydraulic fracturing. Report the information 

specified in paragraph (h) of this section. 

(viii) Onshore production storage tanks. Report the information specified in paragraph (j) 

of this section. 

(ix) Well testing. Report the information specified in paragraph (l) of this section. 

(x) Associated natural gas. Report the information specified in paragraph (m) of this 

section. 

(xi) Flare stacks. Report the information specified in paragraph (n) of this section. 

(xii) Centrifugal compressors. Report the information specified in paragraph (o) of this 

section. 

(xiii) Reciprocating compressors. Report the information specified in paragraph (p) of 

this section. 

(xiv) Equipment leaks by population count. Report the information specified in paragraph 

(r) of this section. 

(xv) EOR injection pumps. Report the information specified in paragraph (w) of this 

section. 

(xvi) EOR hydrocarbon liquids. Report the information specified in paragraph (x) of this 

section. 

(xvii) Combustion equipment. Report the information specified in paragraph (z) of this 

section.
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(2) Offshore petroleum and natural gas production. Report the information specified in 

paragraph (s) of this section.

(3) Onshore natural gas processing. For the equipment/activities specified in paragraphs 

(a)(3)(i) through (a)(3)(vii) of this section, report the information specified in the applicable 

paragraphs of this section.

(i) Acid gas removal units. Report the information specified in paragraph (d) of this 

section. 

(ii) Dehydrators. Report the information specified in paragraph (e) of this section. 

(iii) Blowdown vent stacks. Report the information specified in paragraph (i) of this 

section. 

(iv) Flare stacks. Report the information specified in paragraph (n) of this section. 

(v) Centrifugal compressors. Report the information specified in paragraph (o) of this 

section. 

(vi) Reciprocating compressors. Report the information specified in paragraph (p) of this 

section. 

(vii) Equipment leak surveys. Report the information specified in paragraph (q) of this 

section. 

(4) Onshore natural gas transmission compression. For the equipment/activities specified 

in paragraphs (a)(4)(i) through (a)(4)(vii) of this section, report the information specified in the 

applicable paragraphs of this section. 

(i) Natural gas pneumatic devices. Report the information specified in paragraph (b) of 

this section. 
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(ii) Blowdown vent stacks. Report the information specified in paragraph (i) of this 

section. 

(iii) Transmission storage tanks. Report the information specified in paragraph (k) of this 

section. 

(iv) Flare stacks. Report the information specified in paragraph (n) of this section. 

(v) Centrifugal compressors. Report the information specified in paragraph (o) of this 

section. 

(vi) Reciprocating compressors. Report the information specified in paragraph (p) of this 

section. 

(vii) Equipment leak surveys. Report the information specified in paragraph (q) of this 

section.

(5) Underground natural gas storage. For the equipment/activities specified in paragraphs 

(a)(5)(i) through (a)(5)(vi) of this section, report the information specified in the applicable 

paragraphs of this section.

(i) Natural gas pneumatic devices. Report the information specified in paragraph (b) of 

this section. 

(ii) Flare stacks. Report the information specified in paragraph (n) of this section. 

(iii) Centrifugal compressors. Report the information specified in paragraph (o) of this 

section. 

(iv) Reciprocating compressors. Report the information specified in paragraph (p) of this 

section. 

(v) Equipment leak surveys. Report the information specified in paragraph (q) of this 

section. 
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(vi) Equipment leaks by population count. Report the information specified in paragraph 

(r) of this section. 

(6) LNG storage. For the equipment/activities specified in paragraphs (a)(6)(i) through 

(a)(6)(v) of this section, report the information specified in the applicable paragraphs of this 

section. 

(i) Flare stacks. Report the information specified in paragraph (n) of this section. 

(ii) Centrifugal compressors. Report the information specified in paragraph (o) of this 

section. 

(iii) Reciprocating compressors. Report the information specified in paragraph (p) of this 

section. 

(iv) Equipment leak surveys. Report the information specified in paragraph (q) of this 

section. 

(v) Equipment leaks by population count. Report the information specified in paragraph 

(r) of this section. 

(7) LNG import and export equipment. For the equipment/activities specified in 

paragraphs (a)(7)(i) through (a)(7)(vi) of this section, report the information specified in the 

applicable paragraphs of this section. 

(i) Blowdown vent stacks. Report the information specified in paragraph (i) of this 

section. 

(ii) Flare stacks. Report the information specified in paragraph (n) of this section. 

(iii) Centrifugal compressors. Report the information specified in paragraph (o) of this 

section. 
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(iv) Reciprocating compressors. Report the information specified in paragraph (p) of this 

section. 

(v) Equipment leak surveys. Report the information specified in paragraph (q) of this 

section. 

(vi) Equipment leaks by population count. Report the information specified in paragraph 

(r) of this section. 

(8) Natural gas distribution. For the equipment/activities specified in paragraphs (a)(8)(i) 

through (a)(8)(iii) of this section, report the information specified in the applicable paragraphs of 

this section. 

(i) Combustion equipment. Report the information specified in paragraph (z) of this 

section. 

(ii) Equipment leak surveys. Report the information specified in paragraph (q) of this 

section. 

(iii) Equipment leaks by population count. Report the information specified in paragraph 

(r) of this section. 

 (b) For offshore petroleum and natural gas production, report emissions of CH4, CO2, 

and N2O as applicable to the source type (in metric tons CO2e per year at standard conditions) 

individually for all of the emissions source types listed in the most recent BOEMRE study.

(c) Report the information listed in this paragraph for each applicable source type in 

metric tons of CO2e for each GHG. If a facility operates under more than one industry segment, 

each piece of equipment should be reported under the unit's respective majority use segment. 

When a source type listed under this paragraph routes gas to flare, separately report the 

emissions that were vented directly to the atmosphere without flaring, and the emissions that 
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resulted from flaring the gas. Both the vented and flared emissions will be reported under the 

respective source type and not under the flare source type.

(1) For natural gas pneumatic devices (refer to Equation W-1 of §98.233), report the 

following:

(i) Actual count and estimated count separately of natural gas pneumatic high bleed 

devices as applicable.

(ii) Actual count and estimated count separately of natural gas pneumatic low bleed 

devices as applicable.

(iii) Actual count and estimated count separately of natural gas pneumatic intermittent 

bleed devices as applicable.

(iv) Report annual CO2 and CH4 emissions at the facility level, expressed in metric tons 

CO2e for each gas, for each of the following pieces of equipment: high bleed pneumatic devices; 

intermittent bleed pneumatic devices; low bleed pneumatic devices.

(2) For natural gas driven pneumatic pumps (refer to Equation W-2 of §98.233), report 

the following,

(i) Count of natural gas driven pneumatic pumps.

(ii) Report annual CO2 and CH4 emissions at the facility level, expressed in metric tons 

CO2e for each gas, for all natural gas driven pneumatic pumps combined.

(3) For each acid gas removal unit (refer to Equation W-3 and Equation W-4 of §98.233), 

report the following:

(i) Total throughput off the acid gas removal unit using a meter or engineering estimate 

based on process knowledge or best available data in million cubic feet per year.
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(ii) For Calculation Methodology 1 and Calculation Methodology 2 of §98.233(d), annual 

average fraction of CO2 content in the vent from the acid gas removal unit (refer to 

§98.233(d)(6)).

(iii) For Calculation Methodology 3 of §98.233(d), annual average volume fraction of 

CO2 content of natural gas into and out of the acid gas removal unit (refer to §98.233(d)(7) and 

(d)(8)).

(iv) Report the annual quantity of CO2, expressed in metric tons CO2e, that was recovered 

from the AGR unit and transferred outside the facility, under subpart PP of this part.

(v) Report annual CO2 emissions for the AGR unit, expressed in metric tons CO2e.

(vi) For the onshore natural gas processing industry segment only, report a unique name 

or ID number for the AGR unit.

(vii) An indication of which calculation methodology was used for the AGR.

(4) For dehydrators, report the following:

(i) For each Glycol dehydrator with a throughput greater than or equal to 0.4 MMscfd 

(refer to §98.233(e)(1)), report the following:

(A) Glycol dehydrator feed natural gas flow rate in MMscfd, determined by engineering 

estimate based on best available data.

(B) Glycol dehydrator absorbent circulation pump type.

(C) Whether stripper gas is used in glycol dehydrator.

(D) Whether a flash tank separator is used in glycol dehydrator.

(E) Type of absorbent.

(F) Total time the glycol dehydrator is operating in hours.

(G) Temperature, in degrees Fahrenheit and pressure, in psig, of the wet natural gas.
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(H) Concentration of CH4 and CO2 in wet natural gas.

(I) What vent gas controls are used (refer to §98.233(e)(3) and (e)(4)).

(J) For each glycol dehydrator, report annual CO2 and CH4 emissions that resulted from 

venting gas directly to the atmosphere, expressed in metric tons CO2e for each gas.

(K) For each glycol dehydrator, report annual CO2, CH4, and N2O emissions that resulted 

from flaring process gas from the dehydrator, expressed in metric tons CO2e for each gas.

(L) For the onshore natural gas processing industry segment only, report a unique name 

or ID number for glycol dehydrator.

(ii) For all glycol dehydrators with a throughput less than 0.4 MMscfd (refer to §98.233, 

Equation W-5 of §98.233), report the following:

(A) Count of glycol dehydrators.

(B) Which vent gas controls are used (refer to §98.233(e)(3) and (e)(4)).

(C) Report annual CO2 and CH4 emissions at the facility level that resulted from venting 

gas directly to the atmosphere, expressed in metric tons CO2e for each gas, combined for all 

glycol dehydrators with annual average daily throughput of less than 0.4 MMscfd.

(D) Report annual CO2, CH4, and N2O emissions at the facility level that resulted from 

the flaring of process gas, expressed in metric tons CO2e for each gas, combined for all glycol 

dehydrators with annual average daily throughput of less than 0.4 MMscfd.

(iii) For absorbent desiccant dehydrators (refer to Equation W-6 of §98.233), report the 

following:

(A) Count of desiccant dehydrators.

(B) Report annual CO2 and CH4 emissions at the facility level, expressed in metric tons 

CO2e for each gas, for all absorbent desiccant dehydrators combined.
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(5) For well venting for liquids unloading, report the following:

(i) For Calculation Methodology 1 (refer to Equation W-7 of §98.233), report the 

following for each tubing diameter group and pressure group combination within each sub-basin 

category:

(A) Count of wells vented to the atmosphere for liquids unloading.

(B) Count of plunger lifts. Whether the selected well from the tubing diameter and 

pressure group combination had a plunger lift (yes/no).

(C) Cumulative number of unloadings vented to the atmosphere.

(D) Average flow rate of the measured well venting in cubic feet per hour (refer to 

§98.233(f)(1)(i)(A)).

(E) Internal casing diameter or internal tubing diameter in inches, where applicable, and 

well depth of each well, in feet, selected to represent emissions in that tubing size and pressure 

combination.

(F) Casing pressure, in psia, of each well selected to represent emissions in that tubing 

size group and pressure group combination that does not have a plunger lift.

(G) Tubing pressure, in psia, of each well selected to represent emissions in a tubing size 

group and pressure group combination that has a plunger lift.

(H) Report annual CO2 and CH4 emissions, expressed in metric tons CO2e for each gas.

(ii) For Calculation Methodologies 2 and 3 (refer to Equation W-8 and W-9 of §98.233), 

report the following for each sub-basin category:

(A) Count of wells vented to the atmosphere for liquids unloading.

(B) Count of plunger lifts.

(C) Cumulative number of unloadings vented to the atmosphere.
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(D) Average internal casing diameter, in inches, for all wells, where applicable.

(E) Report annual CO2 and CH4 emissions, expressed in metric tons CO2e for each GHG 

gas.

(6) For well completions and workovers, report the following for each sub-basin 

category:

(i) For gas well completions and workovers with hydraulic fracturing by sub-basin and 

well type (horizontal or vertical) combination (refer to Equation W-10A and W-10B of §98.233), 

report the following:

(A) Total count of completions in calendar year.

(B) When using Equation W-10A, measured flow rate of backflow during well 

completion in standard cubic feet per hour.

(C) Total count of workovers in calendar year that flare gas or vent gas to the 

atmosphere.

(D) When using Equation W-10A, measured flow rate of backflow during well workover 

in standard cubic feet per hour.

(E) When using Equation W-10A, total number of days of backflow from all wells during 

completions.

(F) When using Equation W-10A, total number of days of backflow from all wells during 

workovers.

(G) Report number of completions employing purposely designed equipment that 

separates natural gas from the backflow and the amount of natural gas, in standard cubic feet, 

recovered using engineering estimate based on best available.
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(H) Report number of workovers employing purposely designed equipment that separates 

natural gas from the backflow and the amount of natural gas, in standard cubic feet, recovered 

using engineering estimate based on best available data.

(I) Annual CO2 and CH4 emissions that resulted from venting gas directly to the 

atmosphere, expressed in metric tons CO2e for each gas.

(J) Annual CO2, CH4, and N2O emissions that resulted from flares, expressed in metric 

tons CO2e for each gas.

(ii) For gas well completions and workovers without hydraulic fracturing (refer to 

Equation W-13 of §98.233):

(A) Total count of completions in calendar year.

(B) Total count of workovers in calendar year that flare gas or vent gas to the 

atmosphere.

(C) Total number of days of gas venting to the atmosphere during backflow for 

completion.

(D) Annual CO2 and CH4 emissions that resulted from venting gas directly to the 

atmosphere, expressed in metric tons CO2e for each gas.

(E) Annual CO2, CH4, and N2O emissions that resulted from flares, expressed in metric 

tons CO2e for each gas.

(7) For blowdown vent stack emission source, (refer to Equation W-14A and Equation 

W-14B of §98.233), report the following:

(i) For each unique physical volume that is blown down more than once during the 

calendar year, report the following:

(A) Total number of blowdowns for each unique physical volume in the calendar year.
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(B) Annual CO2 and CH4 emissions, for each unique physical blowdown volume, 

expressed in metric tons CO2e for each gas.

(C) A unique name or ID number for the unique physical volume.

(ii) For all unique volumes that are blown down once during the calendar year, report the 

following:

(A) Total number of blowdowns for all unique physical volumes in the calendar year.

(B) Annual CO2 and CH4 emissions from all unique physical volumes as an aggregate per 

facility, expressed in metric tons CO2e for each gas.

(8) For gas emitted from produced oil sent to atmospheric tanks:

(i) For wellhead gas-liquid separator with oil throughput greater than or equal to 10 

barrels per day, using Calculation Methodology 1 and 2 of §98.233(j), report the following by 

sub-basin category, unless otherwise specified:

(A) Number of wellhead separators sending oil to atmospheric tanks.

(B) Estimated average separator temperature, in degrees Fahrenheit, and estimated 

average pressure, in psig.

(C) Estimated average sales oil stabilized API gravity, in degrees.

(D) Count of hydrocarbon tanks at well pads.

(E) Best estimate of count of stock tanks not at well pads receiving your oil.

(F) Total volume of oil from all wellhead separators sent to tank(s) in barrels per year.

(G) Count of tanks with emissions control measures, either vapor recovery system or 

flaring, for tanks at well pads.

(H) Best estimate of count of stock tanks assumed to have emissions control measures not 

at well pads, receiving your oil.
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(I) Range of concentrations of flash gas, CH4 and CO2.

(J) Annual CO2 and CH4 emissions that resulted from venting gas to the atmosphere, 

expressed in metric tons CO2e for each gas, for all wellhead gas-liquid separators or storage 

tanks using Calculation Methodology 1, and for all wellhead gas-liquid separators or storage 

tanks using Calculation Methodology 2 of §98.233(j).

(K) Annual CO2 and CH4 gas quantities that were recovered, expressed in metric tons 

CO2e for each gas, for all wellhead gas-liquid separators or storage tanks using Calculation 

Methodology 1, and for all wellhead gas-liquid separators or storage tanks using Calculation 

Methodology 2 of §98.233(j).

(L) Annual CO2, CH4, and N2O emissions that resulted from flaring gas, expressed in 

metric tons CO2e for each gas, for all wellhead gas-liquid separators or storage tanks using 

Calculation Methodology 1, and for all wellhead gas-liquid separators or storage tanks using 

Calculation Methodology 2 of §98.233(j).

(ii) For wells with oil production greater than or equal to 10 barrels per day, using 

Calculation Methodology 3 and 4 of §98.233(j), report the following by sub-basin category:

(A) Total volume of sales oil from all wells in barrels per year.

(B) Total number of wells sending oil directly to tanks.

(C) Total number of wells sending oil to separators off the well pads.

(D) Sales oil API gravity range for wells in (c)(8)(ii)(B) and (c)(8)(ii)(C) of this section, 

in degrees.

(E) Count of hydrocarbon tanks on wellpads.

(F) Count of hydrocarbon tanks, both on and off well pads assumed to have emissions 

control measures: either vapor recovery system or flaring of tank vapors.
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(G) Annual CO2 and CH4 emissions that resulted from venting gas to the atmosphere, 

expressed in metric tons CO2e for each gas, at the sub-basin level for Calculation Methodology 3 

or 4 of §98.233(j).

(H) Annual CO2 and CH4 gas quantities that were recovered, expressed in metric tons 

CO2e for each gas, at the sub-basin level for Calculation Methodology 3 or 4 of §98.233(j).

(I) Annual CO2, CH4, and N2O emissions that resulted from flaring gas, expressed in 

metric tons CO2e for each gas, at the sub-basin level for Calculation Methodology 3 and 4 of 

§98.233(j).

(iii) For wellhead gas-liquid separators and wells with throughput less than 10 barrels per 

day, using Calculation Methodology 5 of §98.233(j) Equation W-15 of §98.233, report the 

following:

(A) Number of wellhead separators.

(B) Number of wells without wellhead separators.

(C) Total volume of oil production in barrels per year.

(D) Best estimate of fraction of production sent to tanks with assumed control measures: 

either vapor recovery system or flaring of tank vapors.

(E) Count of hydrocarbon tanks on well pads.

(F) Annual CO2 and CH4 emissions that resulted from venting gas to the atmosphere, 

expressed in metric tons CO2e for each gas, at the sub-basin level for Calculation Methodology 5 

of §98.233(j).

(G) Annual CO2 and CH4 gas quantities that were recovered, expressed in metric tons 

CO2e for each gas, at the sub-basin level for Calculation Methodology 5 of §98.233(j).
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(H) Annual CO2, CH4, and N2O emissions that resulted from flaring gas, expressed in 

metric tons CO2e for each gas, at the sub-basin level for Calculation Methodology 5 of 

§98.233(j).

(iv) If wellhead separator dump valve is functioning improperly during the calendar year 

(refer to Equation W-16 of §98.233), report the following:

(A) Count of wellhead separators that dump valve factor is applied.

(B) Annual CO2 and CH4 emissions that resulted from venting gas to the atmosphere, 

expressed in metric tons CO2e for each gas, at the sub-basin level for improperly functioning 

dump valves.

(9) For transmission tank emissions identified in §98.233(k) from scrubber dump valves 

report the following:

(i) For each vent stack, report annual CO2 and CH4 emissions that resulted from venting 

gas directly to the atmosphere, expressed in metric tons CO2e for each gas.

(ii) For each transmission storage tank, report annual CO2, CH4, and N2O emissions that 

resulted from flaring process gas from the transmission storage tank, expressed in metric tons 

CO2e for each gas.

(iii) A unique name or ID number for the vent stack monitored according to 40 CFR 

98.233(k).

(10) For well testing venting and flaring (refer to Equation W-17A or W-17B of 

§98.233), report the following:

(i) Number of wells tested per basin in calendar year.

(ii) Average gas to oil ratio for each basin.

(iii) Average number of days the well is tested in a basin.
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(iv) Report annual CO2 and CH4 emissions at the facility level, expressed in metric tons 

CO2e for each gas, emissions from well testing venting.

(v) Report annual CO2, CH4, and N2O emissions at the facility level, expressed in metric 

tons CO2e for each gas, emissions from well testing flaring.

(11) For associated natural gas venting and flaring (refer to Equation W-18 of §98.233), 

report the following for each basin:

(i) Number of wells venting or flaring associated natural gas in a calendar year.

(ii) Average gas to oil ratio for each basin.

(iii) Report annual CO2 and CH4 emissions at the facility level, expressed in metric tons 

CO2e for each gas, emissions from associated natural gas venting.

(iv) Report annual CO2, CH4, and N2O emissions at the facility level, expressed in metric 

tons CO2e for each gas, emissions from associated natural gas flaring.

(12) For flare stacks (refer to Equation W-19, W-20, and W-21 of §98.233), report the 

following for each flare:

(i) Whether flare has a continuous flow monitor.

(ii) Volume of gas sent to flare in cubic feet per year.

(iii) Percent of gas sent to un-lit flare determined by engineering estimate and process 

knowledge based on best available data and operating records.

(iv) Whether flare has a continuous gas analyzer.

(v) Flare combustion efficiency.

(vi) Report uncombusted CH4 emissions, in metric tons CO2e (refer to Equation W-19 of 

§98.233).
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(vii) Report uncombusted CO2 emissions, in metric tons CO2e (refer to Equation W-20 of 

§98.233).

(viii) Report combusted CO2 emissions, in metric tons CO2e (refer to Equation W-21 of 

§98.233).

(ix) Report N2O emissions, in metric tons CO2e.

(x) For the natural gas processing industry segment, a unique name or ID number for the 

flare stack.

(xi) In the case that a CEMS is used to measure CO2 emissions for the flare stack, 

indicate that a CEMS was used in the annual report and report the combusted CO2 and 

uncombusted CO2 as a combined number.

(13) For each centrifugal compressor:

(i) For compressors with wet seals in operational mode (refer to Equations W-22 through 

W-24 of §98.233), report the following for each degassing vent:

(A) Number of wet seals connected to the degassing vent.

(B) Fraction of vent gas recovered for fuel or sales or flared.

(C) Annual throughput in million scf, use an engineering calculation based on best 

available data.

(D) Type of meters used for making measurements.

(E) Reporter emission factor for wet seal oil degassing vents in cubic feet per hour (refer 

to Equation W-24 of §98.233).

(F) Total time the compressor is operating in hours.

(G) Report seal oil degassing vent emissions for compressors measured and for 

compressors not measured in metric tons of CO2e for each gas.
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(ii) For wet and dry seal centrifugal compressors in operating mode, (refer to Equations 

W-22 through W-24 of §98.233), report the following:

(A) Total time in hours the compressor is in operating mode.

(B) Reporter emission factor for blowdown vents in cubic feet per hour (refer to Equation 

W-24 of §98.233).

(C) Report blowdown vent emissions when in operating mode in metric tons of CO2e for 

each gas.

(iii) For wet and dry seal centrifugal compressors in not operating, depressurized mode 

(refer to Equations W-22 through W-24 of §98.233), report the following:

(A) Total time in hours the compressor is in shutdown, depressurized mode.

(B) Reporter emission factor for isolation valve emissions in shutdown, depressurized 

mode in cubic feet per hour (refer to Equation W-24 of §98.233).

(C) Report the isolation valve leakage emissions in not operating, depressurized mode in 

metric tons of CO2e for each gas.

(iv) Report total annual compressor emissions from all modes of operation in metric tons 

of CO2e for each gas.

(v) For centrifugal compressors in onshore petroleum and natural gas production (refer to 

Equation W-25 of §98.233), report the following:

(A) Count of compressors.

(B) Report annual emissions in metric tons of CO2e for each gas (refer to Equation W-25 

of §98.233) collectively.

(14) For reciprocating compressors:
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(i) For reciprocating compressors rod packing emissions with or without a vent in 

operating mode, report the following:

(A) Annual throughput in million scf, use an engineering calculation based on best 

available data.

(B) Total time in hours the reciprocating compressor is in operating mode.

(C) Report rod packing emissions for compressors measured and for compressors not 

measured in metric tons of CO2e for each gas.

(ii) For reciprocating compressors blowdown vents not manifold to rod packing vents, in 

operating and standby pressurized mode (refer to Equations W-26 through W-28 of §98.233), 

report the following:

(A) Total time in hours the compressor is in standby, pressurized mode.

(B) Reporter emission factor for blowdown vents in cubic feet per hour (refer to §98.233, 

Equation W-28).

(C) Report blowdown vent emissions when in operating and standby pressurized modes 

in metric tons of CO2e for each gas.

(iii) For reciprocating compressors in not operating, depressurized mode (refer to 

Equations W-26 through W-28 of §98.233), report the following:

(A) Total time the compressor is in not operating, depressurized mode.

(B) Reporter emission factor for isolation valve emissions in not operating, depressurized 

mode in cubic feet per hour (refer to Equation W-28 of §98.233).

(C) Report isolation valve leakage emissions in not operating, depressurized mode in 

metric tons of CO2e for each gas.
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(iv) Report total annual compressor emissions from all modes of operation in metric tons 

of CO2e for each gas.

(v) For reciprocating compressors in onshore petroleum and natural gas production (refer 

to Equation W-29 of §98.233), report the following:

(A) Count of compressors.

(B) Report annual emissions in metric tons of CO2e for each gas collectively (refer to 

Equation W-29 of §98.233).

(15) For each component type (major equipment type for onshore production) that uses 

emission factors for estimating emissions (refer to §98.233(q) and (r))

(i) For equipment leaks found in each leak survey (refer to §98.233(q)), report the 

following:

(A) Total count of leaks found in each complete survey listed by date of survey and each 

component type for which there is a leaker emission factor in Tables W-2, W-3, W-4, W-5, W-6, 

and W-7 of this subpart.

(B) For onshore natural gas processing, range of concentrations of CH4 and CO2 (refer to 

Equation W-30A of §98.233).

(C) Annual CO2 and CH4 emissions in metric tons CO2e for each gas (refer to Equation 

W-30A of §98.233), by component type.

(ii) For equipment leaks calculated using population counts and factors (refer to 

§98.233(r)), report the following:

(A) For source categories §98.230(a)(5), (a)(6), and (a)(7), total count for each 

component type in Tables W-4, W-5, and W-6 of this subpart for which there is a population 

emission factor, listed by major heading and component type.
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(B) For onshore production (refer to §98.230 paragraph (a)(2)), total count for each type 

of major equipment in Table W-1B and Table W-1C of this subpart, by facility.

(C) Annual CO2 and CH4 emissions, in metric tons CO2e for each gas (refer to Equation 

W-31 of §98.233), by component type.

(16) For local distribution companies, report the following:

(i) Total number of above grade T-D transfer stations in the facility.

(ii) Number of years over which all T-D transfer stations will be monitored at least once.

(iii) Number of T-D stations monitored in calendar year.

(iv) Total number of below grade T-D transfer stations in the facility.

(v) Total number of above grade metering-regulating stations (this count will include 

above grade T-D transfer stations) in the facility.

(vi) Total number of below grade metering-regulating stations (this count will include 

below grade T-D transfer stations) in the facility.

(vii) [Reserved]

(viii) Leak factor for meter/regulator run developed in Equation W-32 of §98.233.

(ix) Number of miles of unprotected steel distribution mains.

(x) Number of miles of protected steel distribution mains.

(xi) Number of miles of plastic distribution mains.

(xii) Number of miles of cast iron distribution mains.

(xiii) Number of unprotected steel distribution services.

(xiv) Number of protected steel distribution services.

(xv) Number of plastic distribution services.

(xvi) Number of copper distribution services.
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(xvii) Annual CO2 and CH4 emissions, in metric tons CO2e for each gas, from all above 

grade T-D transfer stations combined.

(xviii) Annual CO2 and CH4 emissions, in metric tons CO2e for each gas, from all below 

grade T-D transfer stations combined.

(xix) Annual CO2 and CH4 emissions, in metric tons CO2e for each gas, from all above 

grade metering-regulating stations (including T-D transfer stations) combined.

(xx) Annual CO2 and CH4 emissions, in metric tons CO2e for each gas, from all below 

grade metering-regulating stations (including T-D transfer stations) combined.

(xxi) Annual CO2 and CH4 emissions, in metric tons CO2e for each gas, from all 

distribution mains combined.

(xxii) Annual CO2 and CH4 emissions, in metric tons CO2e for each gas, from all 

distribution services combined.

(17) For each EOR injection pump blowdown (refer to Equation W-37 of §98.233), 

report the following:

(i) Pump capacity, in barrels per day.

(ii) Volume of critical phase gas between isolation valves.

(iii) Number of blowdowns per year.

(iv) Critical phase EOR injection gas density.

(v) For each EOR pump, report annual CO2 emissions, expressed in metric tons CO2e for 

each gas.

(18) For EOR hydrocarbon liquids dissolved CO2 for each sub-basin category (refer to 

Equation W-38 of §98.233), report the following:

(i) Volume of crude oil produced in barrels per year.
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(ii) Amount of CO2 retained in hydrocarbon liquids in metric tons per barrel, under 

standard conditions.

(iii) Report annual CO2 emissions at the sub-basin level, expressed in metric tons CO2e.

(19) For onshore petroleum and natural gas production and natural gas distribution 

combustion emissions, report the following:

(i) Cumulative number of external fuel combustion units with a rated heat capacity equal 

to or less than 5 mmBtu/hr, by type of unit.

(ii) Cumulative number of external fuel combustion units with a rated heat capacity larger 

than 5 mmBtu/hr, by type of unit.

(iii) Report annual CO2, CH4, and N2O emissions from external fuel combustion units 

with a rated heat capacity larger than 5 mmBtu/hr, expressed in metric tons CO2e for each gas, 

by type of unit.

(iv) Cumulative volume of fuel combusted in external fuel combustion units with a rated 

heat capacity larger than 5 mmBtu/hr, by fuel type.

(v) Cumulative number of internal fuel combustion units, not compressor-drivers, with a 

rated heat capacity equal to or less than 1 mmBtu/hr or 130 horsepower, by type of unit.

(vi) Report annual CO2, CH4, and N2O emissions from internal combustion units greater 

than 1mmBtu/hr, expressed in metric tons CO2e for each gas, by type of unit.

(vii) Cumulative volume of fuel combusted in internal combustion units with a rated heat 

capacity larger than 1 mmBtu/hr or 130 horsepower, by fuel type.

(d) Report annual throughput as determined by engineering estimate based on best 

available data for each industry segment listed in paragraphs (a)(1) through (a)(8) of this section.
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(e) For onshore petroleum and natural gas production, report the best available estimate 

of API gravity, best available estimate of gas to oil ratio, and best available estimate of average 

low pressure separator pressure for each oil sub-basin category. 

(b) Natural gas pneumatic devices. You must indicate whether the facility contains the 

following types of equipment: continuous high bleed natural gas pneumatic devices, continuous 

low bleed natural gas pneumatic devices, and intermittent bleed natural gas pneumatic devices. If 

the facility contains any continuous high bleed natural gas pneumatic devices, continuous low 

bleed natural gas pneumatic devices, or intermittent bleed natural gas pneumatic devices, then 

you must report the information specified in paragraphs (b)(1) through (b)(4) of this section. 

(1) The number of natural gas pneumatic devices as specified in paragraphs (b)(1)(i) and 

(b)(1)(ii) of this section. 

(i) The total number of devices, determined according to §98.233(a)(1) and (a)(2). 

(ii) If the reported value in paragraph (b)(1)(i) of this section is an estimated value 

determined according to §98.233(a)(2), then you must report the information specified in 

paragraphs (b)(1)(ii)(A) through (b)(1)(ii)(C) of this section. 

(A) The number of devices reported in paragraph (b)(1)(i) of this section that are counted. 

(B) The number of devices reported in paragraph (b)(1)(i) of this section that are 

estimated (not counted). 

(C) Whether the calendar year is the first calendar year of reporting or the second 

calendar year of reporting. 

(2) Estimated average number of hours in the calendar year that the natural gas pneumatic 

devices reported in paragraph (b)(1)(i) of this section were operating in the calendar year (“Tt” in 

Equation W-1 of this subpart). 
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(3) Annual CO2 emissions, in metric tons CO2, for the natural gas pneumatic devices 

combined, calculated using Equation W-1 of this subpart and § 98.233(a)(4), and reported in 

paragraph (b)(1)(i) of this section. 

(4) Annual CH4 emissions, in metric tons CH4, for the natural gas pneumatic devices 

combined, calculated using Equation W-1 of this subpart and § 98.233(a)(4), and reported in 

paragraph (b)(1)(i) of this section. 

 (c) Natural gas driven pneumatic pumps. You must indicate whether the facility has any 

natural gas driven pneumatic pumps. If the facility contains any natural gas driven pneumatic 

pumps, then you must report the information specified in paragraphs (c)(1) through (c)(4) of this 

section. 

(1) Count of natural gas driven pneumatic pumps. 

(2) Average estimated number of hours in the calendar year the pumps were operational 

(“T” in Equation W-2 of this subpart). 

(3) Annual CO2 emissions, in metric tons CO2, for all natural gas driven pneumatic 

pumps combined, calculated according to §98.233(c)(1) and (c)(2). 

(4) Annual CH4 emissions, in metric tons CH4, for all natural gas driven pneumatic 

pumps combined, calculated according to §98.233(c)(1) and (c)(2). 

(d) Acid gas removal units. You must indicate whether your facility has any acid gas 

removal units that vent directly to the atmosphere, to a flare or engine, or to a sulfur recovery 

plant. If your facility contains any acid gas removal units that vent directly to the atmosphere, to 

a flare or engine, or to a sulfur recovery plant, then you must report the information specified in 

paragraphs (d)(1) and (d)(2) of this section. 
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(1) You must report the information specified in paragraphs (d)(1)(i) through (d)(1)(vi) of 

this section for each acid gas removal unit. 

(i) A unique name or ID number for the acid gas removal unit. For the onshore petroleum 

and natural gas production industry segment, a different name or ID may be used for a single 

acid gas removal unit for each location it operates at in a given year. 

(ii) Total feed rate entering the acid gas removal unit, using a meter or engineering 

estimate based on process knowledge or best available data, in million cubic feet per year. 

(iii) The calculation method used to calculate CO2 emissions from the acid gas removal 

unit, as specified in § 98.233(d). 

(iv) Whether any CO2 emissions from the acid gas removal unit are recovered and 

transferred outside the facility, as specified in § 98.233(d)(11). If any CO2 emissions from the 

acid gas removal unit were recovered and transferred outside the facility, then you must report 

the annual quantity of CO2, in metric tons CO2, that was recovered and transferred outside the 

facility. 

(v) Annual CO2 emissions, in metric tons CO2, from the acid gas removal unit, calculated 

using any one of the calculation methods specified in § 98.233(d) and as specified in § 

98.233(d)(10) and (11). 

(vi) Sub-basin ID (for the onshore petroleum and natural gas production industry segment 

only). 

(2) You must report information specified in paragraphs (d)(2)(i) through (d)(2)(iii) of 

this section, applicable to the calculation method reported in paragraph (d)(1)(iii) of this section, 

for each acid gas removal unit. 
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(i) If you used Calculation Method 1 or Calculation Method 2 as specified in § 98.233(d) 

to calculate CO2 emissions from the acid gas removal unit, then you must report the information 

specified in paragraphs (d)(2)(i)(A) and (d)(2)(i)(B) of this section. 

(A) Annual average volumetric fraction of CO2 in the vent gas exiting the acid gas 

removal unit. 

(B) Annual volume of gas vented from the acid gas removal unit, in cubic feet. 

(ii) If you used Calculation Method 3 as specified in § 98.233(d) to calculate CO2

emissions from the acid gas removal unit, then you must report the information specified in 

paragraphs (d)(2)(ii)(A) through (d)(2)(ii)(D) of this section. 

(A) Which equation was used; Equation W-4A or W-4B. 

(B) Annual average volumetric fraction of CO2 in the natural gas flowing out of the acid 

gas removal unit, as specified in Equation W-4A or Equation W-4B of this subpart. 

(C) Annual average volumetric fraction of CO2 content in natural gas flowing into the 

acid gas removal unit, as specified in Equation W-4A or Equation W-4B of this subpart. 

(D) The natural gas flow rate used, as specified in Equation W-4A of this subpart, 

reported as either total annual volume of natural gas flow into the acid gas removal unit in cubic 

feet at actual conditions; or total annual volume of natural gas flow out of the acid gas removal 

unit, as specified in Equation W-4B of this subpart, in cubic feet at actual conditions,.

(iii) If you used Calculation Method 4 as specified in § 98.233(d) to calculate CO2

emissions from the acid gas removal unit, then you must report the information specified in 

paragraphs (d)(2)(iii)(A) through (d)(2)(iii)(L) of this section, as applicable to the simulation 

software package used. 

(A) The name of the simulation software package used. 
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(B) Natural gas feed temperature, in degrees Fahrenheit. 

(C) Natural gas feed pressure, in pounds per square inch. 

(D) Natural gas flow rate, in standard cubic feet per minute. 

(E) Acid gas content of the feed natural gas, in mole percent. 

(F) Acid gas content of the outlet natural gas, in mole percent. 

(G) Unit operating hours, excluding downtime for maintenance or standby, in hours per 

year. 

(H) Exit temperature of the natural gas, in degrees Fahrenheit. 

(I) Solvent pressure, in pounds per square inch. 

(J) Solvent temperature, in degrees Fahrenheit. 

(K) Solvent circulation rate, in gallons per minute. 

(L) Solvent weight, in pounds per gallon. 

(e) Dehydrators. You must indicate whether your facility contains any of the following 

equipment: absorbent dehydrators with an annual average daily natural gas throughput greater 

than or equal to 0.4 million standard cubic feet per day, glycol dehydrators with an annual 

average daily natural gas throughput less than 0.4 million standard cubic feet per day, and 

dehydrators that use desiccant. If your facility contains any of the equipment listed in this 

paragraph (e), then you must report the applicable information in paragraphs (e)(1) through 

(e)(3).

(1) For each absorbent dehydrator that has an annual average daily natural gas throughput 

greater than or equal to 0.4 million standard cubic feet per day (as specified in § 98.233(e)(1)), 

you must report the information specified in paragraphs (e)(1)(i) through (e)(1)(xviii) of this 

section for the dehydrator. 
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(i) A unique name or ID number for the dehydrator. For the onshore petroleum and 

natural gas production industry segment, a different name or ID may be used for a single 

dehydrator for each location it operates at in a given year. 

(ii) Dehydrator feed natural gas flow rate, in million standard cubic feet per day, 

determined by engineering estimate based on best available data. 

(iii) Dehydrator feed natural gas water content, in pounds per million standard cubic feet. 

(iv) Dehydrator outlet natural gas water content, in pounds per million standard cubic 

feet. 

(v) Dehydrator absorbent circulation pump type (e.g., natural gas pneumatic, air 

pneumatic, or electric). 

(vi) Dehydrator absorbent circulation rate, in gallons per minute. 

(vii) Type of absorbent (e.g., triethylene glycol (TEG), diethylene glycol (DEG), or 

ethylene glycol (EG)). 

(viii) Whether stripper gas is used in dehydrator. 

(ix) Whether a flash tank separator is used in dehydrator. 

(x) Total time the dehydrator is operating, in hours. 

(xi) Temperature of the wet natural gas, in degrees Fahrenheit. 

(xii) Pressure of the wet natural gas, in pounds per square inch gauge. 

(xiii) Mole fraction of CH4 in wet natural gas. 

(xiv) Mole fraction of CO2 in wet natural gas. 

(xv) Whether any dehydrator emissions are vented to a vapor recovery device. 

(xvi) Whether any dehydrator emissions are vented to a flare or regenerator firebox/fire 

tubes. If any emissions are vented to a flare or regenerator firebox/fire tubes, report the 
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information specified in paragraphs (e)(1)(xvi)(A) through (e)(1)(xvi)(C) of this section for these 

emissions from the dehydrator. 

(A) Annual CO2 emissions, in metric tons CO2, for the dehydrator, calculated according 

to § 98.233(e)(6). 

(B) Annual CH4 emissions, in metric tons CH4, for the dehydrator, calculated according 

to § 98.233(e)(6). 

(C) Annual N2O emissions, in metric tons N2O, for the dehydrator, calculated according 

to § 98.233(e)(6). 

(xvii) Whether any dehydrator emissions are vented to the atmosphere without being 

routed to a flare or regenerator firebox/fire tubes. If any emissions are not routed to a flare or 

regenerator firebox/fire tubes, then you must report the information specified in paragraphs 

(e)(1)(xvii)(A) and (e)(1)(xvii)(B) of this section for those emissions from the dehydrator. 

(A) Annual CO2 emissions, in metric tons CO2, for the dehydrator when not venting to a 

flare or regenerator firebox/fire tubes, calculated according to § 98.233(e)(1) and (e)(5). 

(B) Annual CH4 emissions, in metric tons CH4, for the dehydrator when not venting to a 

flare or regenerator firebox/fire tubes, calculated according to § 98.233(e)(1) and (e)(5). 

(xviii) Sub-basin ID (for the onshore petroleum and natural gas production industry 

segment only). 

 (2) For glycol dehydrators with an annual average daily natural gas throughput less than 

0.4 million standard cubic feet per day (as specified in § 98.233(e)(2)), you must report the 

information specified in paragraphs (e)(2)(i) through (e)(2)(v) of this section for the entire 

facility. 

(i) The total number of dehydrators at the facility. 
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(ii) Whether any dehydrators reported in paragraph (e)(2)(i) of this section were vented to 

a vapor recovery device. If any dehydrators reported in paragraph (e)(2)(i) of this section were 

vented to a vapor recovery device, then you must report the total number of dehydrators at the 

facility that vented to a vapor recovery device. 

(iii) Whether any dehydrators reported in paragraph (e)(2)(i) of this section were vented 

to a control device other than a vapor recovery device or a flare or regenerator firebox/fire tubes. 

If any dehydrators reported in paragraph (e)(2)(i) of this section were vented to a control device 

other than a vapor recovery device or a flare or regenerator firebox/fire tubes, then you must 

specify the type of control device and the number of dehydrators at the facility that were vented 

to each type of control device. 

(iv) Whether any dehydrators reported in paragraph (e)(2)(i) of this section were vented 

to a flare or regenerator firebox/fire tubes. If any dehydrators reported in paragraph (e)(2)(i) of 

this section were vented to a flare or regenerator firebox/fire tubes, then you must report the 

information specified in paragraphs (e)(2)(iv)(A) through (e)(2)(iv)(D) of this section. 

(A) The total number of dehydrators venting to a flare or regenerator firebox/fire tubes. 

(B) Annual CO2 emissions, in metric tons CO2, for the dehydrators reported in paragraph 

(e)(2)(iv)(A) of this section, calculated according to § 98.233(e)(6). 

(C) Annual CH4 emissions, in metric tons CH4, for the dehydrators reported in paragraph 

(e)(2)(iv)(A) of this section, calculated according to § 98.233(e)(6). 

(D) Annual N2O emissions, in metric tons N2O, for the dehydrators reported in paragraph 

(e)(2)(iv)(A) of this section, calculated according to § 98.233(e)(6). 
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(v) For dehydrators reported in paragraph (e)(2)(i) of this section that were not vented to 

a flare or regenerator firebox/fire tubes, report the information specified in paragraphs 

(e)(2)(v)(A) and (e)(2)(v)(B) of this section. 

(A) Annual CO2 emissions in metric tons CO2, for emissions from all dehydrators 

reported in paragraph (e)(2)(i) of this section that were not vented to a flare or regenerator 

firebox/fire tubes, calculated according to § 98.233(e)(2), (e)(4), and (e)(5), where emissions are 

added together for all such dehydrators. 

(B) Annual CH4 emissions in metric tons CO2, for emissions from all dehydrators 

reported in paragraph (e)(2)(i) of this section that were not vented to a flare or regenerator 

firebox/fire tubes, calculated according to § 98.233(e)(2), (e)(4), and (e)(5), where emissions are 

added together for all such dehydrators. 

(3) For dehydrators that use desiccant (as specified in § 98.233(e)(3)), you must report 

the information specified in paragraphs (e)(3)(i) through (e)(3)(iii) of this section for the entire 

facility. 

(i) The same information specified in paragraphs (e)(2)(i) through (e)(2)(iv) of this 

section for glycol dehydrators, and report the information under this paragraph for dehydrators 

that use desiccant.

(ii) Annual CO2 emissions, in metric tons CO2, for emissions from all desiccant 

dehydrators reported under paragraph (e)(3)(i) of this section that are not venting to a flare or 

regenerator firebox/fire tubes, calculated according to § 98.233(e)(3), (e)(4), and (e)(5), and 

summing for all such dehydrators. 

(iii) Annual CH4 emissions, in metric tons CH4, for emissions from all desiccant 

dehydrators reported in paragraph (e)(3)(i) of this section that are not venting to a flare or 
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regenerator firebox/fire tubes, calculated according to § 98.233(e)(3), (e)(4), and (e)(5), and 

summing for all such dehydrators. 

(f) Liquids unloading. You must indicate whether well venting for liquids unloading 

occurs at your facility, and if so, which methods (as specified in § 98.233(f)) were used to 

calculate emissions. If your facility performs well venting for liquids unloading and uses 

Calculation Method 1, then you must report the information specified in paragraph (f)(1) of this 

section. If the facility performs liquids unloading and uses Calculation Method 2 or 3, then you 

must report the information specified in paragraph (f)(2) of this section. 

(1) For each sub-basin and well tubing diameter and pressure grouping for which you 

used Calculation Method 1 to calculate natural gas emissions from well venting for liquids 

unloading, report the information specified in paragraphs (f)(1)(i) through (f)(1)(xii) of this 

section. Report information separately for wells with plunger lifts and wells without plunger lifts. 

(i) Sub-basin ID. 

(ii) Well tubing diameter and pressure group ID.

(iii) Plunger lift indicator. 

(iv) Count of wells vented to the atmosphere for the sub-basin/well tubing diameter and 

pressure grouping. 

(v) Percentage of wells for which the monitoring period used to determine the cumulative 

amount of time venting was not the full calendar year. 

(vi) Cumulative amount of time wells were vented (sum of “Tp” from Equation W-7A or 

W-7B of this subpart), in hours. 

(vii) Cumulative number of unloadings vented to the atmosphere for each well, 

aggregated across all wells in the sub-basin/well tubing diameter and pressure grouping. 
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(viii) Annual natural gas emissions, in standard cubic feet, from well venting for liquids 

unloading, calculated according to § 98.233(f)(1). 

(ix) Annual CO2 emissions, in metric tons CO2, from well venting for liquids unloading, 

calculated according to § 98.233(f)(1) and § 98.233(f)(4). 

(x) Annual CH4 emissions, in metric tons CH4, from well venting for liquids unloading, 

calculated according to § 98.233(f)(1) and § 98.233(f)(4). 

(xi) For each well tubing diameter group and pressure group combination, you must 

report the information specified in paragraphs (f)(1)(xi)(A) through (f)(1)(xi)(E) of this section 

for each individual well not using a plunger lift that was tested during the year. 

(A) API number of tested well. 

(B) Casing pressure, in pounds per square inch absolute. 

(C) Internal casing diameter, in inches. 

(D) Measured depth of the well, in feet. 

(E) Average flow rate of the well venting over the duration of the liquids unloading, in 

standard cubic feet per hour. 

(xii) For each well tubing diameter group and pressure group combination, you must 

report the information specified in paragraphs (f)(1)(xii)(A) through (f)(1)(xii)(E) of this section 

for each individual well using a plunger lift that was tested during the year. 

(A) The API well number. 

(B) The tubing pressure, in pounds per square inch absolute. 

(C) The internal tubing diameter, in inches. 

(D) Measured depth of the well, in feet. 
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(E) Average flow rate of the well venting over the duration of the liquids unloading, in 

standard cubic feet per hour. 

(2) For each sub-basin for which you used Calculation Method 2 or 3 (as specified in § 

93.233(f)) to calculate natural gas emissions from well venting for liquids unloading, you must 

report the information in (f)(2)(i) through (f)(2)(x) of this section. Report information separately 

for each calculation method. 

(i) Sub-basin ID. 

(ii) Calculation method. 

(iii) Plunger lift indicator. 

(iv) Number of wells vented to the atmosphere. 

 (v) Cumulative number of unloadings vented to the atmosphere for each well, aggregated 

across all wells. 

(vi) Annual natural gas emissions, in standard cubic feet, from well venting for liquids 

unloading, calculated according to § 98.233(f)(2) or § 98.233(f)(3), as applicable. 

(vii) Annual CO2 emissions, in metric tons CO2, from well venting for liquids unloading, 

calculated according to § 98.233(f)(2) or § 98.233(f)(3), as applicable, and § 98.233(f)(4). 

(viii) Annual CH4 emissions, in metric tons CH4, from well venting for liquids unloading, 

calculated according to § 98.233(f) (2) or § 98.233(f)(3), as applicable, and § 98.233(f)(4).

(ix) For wells without plunger lifts, the average internal casing diameter, in inches. 

(x) For wells with plunger lifts, the average internal tubing diameter, in inches. 

(g) Completions and workovers with hydraulic fracturing. You must indicate whether 

your facility had any gas well completions or workovers with hydraulic fracturing during the 

calendar year. If your facility had gas well completions or workovers with hydraulic fracturing 
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during the calendar year, then you must report information specified in paragraphs (g)(1) through 

(g)(10) of this section, for each sub-basin and well type combination. Report information 

separately for completions and workovers. 

(1) Sub-basin ID. 

(2) Well type . 

(3) Number of completions or workovers in the category. 

(4) Calculation method used. 

(5) If you used Equation W-10A to calculate annual volumetric total gas emissions, then 

you must report the information specified in paragraphs (g)(5)(i) and (g)(5)(ii) of this section. 

(i) Cumulative backflow time, in hours, for each sub-basin (“Tp” in Equation W-10A). 

(ii) Measured flowback rate, in standard cubic feet per hour, for each sub-basin (“FRs,p” 

in Equation W-12A). 

(6) If you used Equation W-10B to calculate annual volumetric total gas emissions for 

completions that vent gas to the atmosphere, then you must report the vented natural gas volume, 

in standard cubic feet, for each well in the sub-basin (“FVs,p” in Equation W-10B). 

(7) Annual gas emissions, in standard cubic feet (“Es,n” in Equation W-10A or W-10B). 

(8) Annual CO2 emissions, in metric tons CO2. 

(9) Annual CH4 emissions, in metric tons CH4. 

(10) If the well emissions were vented to a flare, then you must report the total N2O 

emissions, in metric tons N2O. 

(h) Completions and workovers without hydraulic fracturing. You must indicate whether 

the facility had any gas well completions without hydraulic fracturing or any gas well workovers 

without hydraulic fracturing, and if the activities occurred with or without flaring. If the facility 
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had gas well completions or workovers without hydraulic fracturing, then you must report the 

information specified in paragraphs (h)(1) through (h)(4) of this section, as applicable. 

(1) For each sub-basin with gas well completions without hydraulic fracturing and 

without flaring, report the information specified in paragraphs (h)(1)(i) through (h)(1)(vi) of this 

section. 

(i) Sub-basin ID. 

(ii) Number of well completions that vented gas directly to the atmosphere without 

flaring. 

(iii) Total number of hours that gas vented directly to the atmosphere during backflow for 

all completions in the sub-basin category (the sum of all “Tp” for completions that vented to the 

atmosphere as used in Equation W-13B). 

(iv) Average daily gas production rate for all completions without hydraulic fracturing in 

the sub-basin without flaring, in standard cubic feet per hour (average of all “Vp” used in 

Equation W-13B). 

(v) Annual CO2 emissions, in metric tons CO2, that resulted from completions venting 

gas directly to the atmosphere (“Es,p” from Equation W-13B for completions that vented directly 

to the atmosphere, converted to mass emissions according to §98.233(h)(1)). 

(vi) Annual CH4 emissions, in metric tons CH4, that resulted from completions venting 

gas directly to the atmosphere (“Es,p” from Equation W-13B for completions that vented directly 

to the atmosphere, converted to mass emissions according to §98.233(h)(1)). 

(2) For each sub-basin with gas well completions without hydraulic fracturing and with 

flaring, report the information specified in paragraphs (h)(2)(i) through (h)(2)(vii) of this section. 

(i) Sub-basin ID. 

Formatted: Not Superscript/ Subscript
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(ii) Number of well completions that flared gas. 

(iii) Total number of hours that gas vented to a flare during backflow for all completions 

in the sub-basin category (the sum of all “Tp” for completions that vented to a flare from 

Equation W-13B). 

(iv) Average daily gas production rate for all completions without hydraulic fracturing in 

the sub-basin with flaring, in standard cubic feet per hour (the average of all “Vp” from Equation 

W-13B). 

(v) Annual CO2 emissions, in metric tons CO2, that resulted from completions that flared 

gas calculated according to §98.233(h)(2). 

(vi) Annual CH4 emissions, in metric tons CH4, that resulted from completions that flared 

gas calculated according to §98.233(h)(2). 

(vii) Annual N2O emissions, in metric tons N2O, that resulted from completions that 

flared gas calculated according to §98.233(h)(2). 

(3) For each sub-basin with gas well workovers without hydraulic fracturing and without 

flaring, report the information specified in paragraphs (h)(3)(i) through (h)(3)(iv) of this section. 

(i) Sub-basin ID. 

(ii) Number of workovers that vented gas to the atmosphere without flaring. 

(iii) Annual CO2 emissions, in metric tons CO2 per year, that resulted from workovers 

venting gas directly to the atmosphere (“Es,wo” in Equation W-13A for workovers that vented 

directly to the atmosphere, converted to mass emissions as specified in §98.233(h)(1)). 

(iv) Annual CH4 emissions, in metric tons CH4 per year, that resulted from workovers 

venting gas directly to the atmosphere (“Es,wo” in Equation W-13A for workovers that vented 

directly to the atmosphere, converted to mass emissions as specified in §98.233(h)(1)). 
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(4) For each sub-basin with gas well workovers without hydraulic fracturing and with 

flaring, report the information specified in paragraphs (h)(4)(i) through (h)(4)(v) of this section. 

(i) Sub-basin ID. 

(ii) Number of workovers that flared gas. 

(iii) Annual CO2 emissions, in metric tons CO2 per year, that resulted from workovers 

that flared gas calculated as specified in §98.233(h)(2). 

(iv) Annual CH4 emissions, in metric tons CH4 per year, that resulted from workovers 

that flared gas, calculated as specified in §98.233(h)(2). 

(v) Annual N2O emissions, in metric tons N2O per year, that resulted from workovers that 

flared gas calculated as specified in §98.233(h)(2). 

(i) Blowdown vent stacks. You must indicate whether your facility has blowdown vent 

stacks. If your facility has blowdown vent stacks, then you must report whether emissions were 

calculated by equipment type or by using flow meters. If you calculated emissions by equipment 

type, then you must report the information specified in paragraph (i)(1) of this section. If you 

calculated emissions using flow meters, then you must report the information specified in 

paragraph (i)(2) of this section. 

(1) Report by equipment type. If you calculated emissions from blowdown vent stacks by 

equipment type, then you must report the equipment types and the information specified in 

paragraphs (i)(1)(i) through (i)(1)(iii) of this section for each equipment type. If a blowdown 

event resulted in emissions from multiple equipment types, then you must report the information 

in paragraphs (i)(1)(i) through (i)(1)(iii) of this section for the equipment type that represented 

the largest portion of the emissions for the blowdown event. 
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(i) Total number of blowdowns in the calendar year for the equipment type (the sum of 

equation variable “N” from Equation W-14A or Equation W-14B of this subpart, for all unique 

physical volumes for the equipment type). 

(ii) Annual CO2 emissions for the equipment type, in metric tons CO2, calculated 

according to § 98.233(i)(2)(iii). 

(iii) Annual CH4 emissions for the equipment type, in metric tons CH4, calculated 

according to §98.233(i)(2)(iii). 

(2) Report by flow meter. If you elect to calculate emissions from blowdown vent stacks 

by using a flow meter according to §98.233(i)(3), then you must report the information specified 

in paragraphs (i)(2)(i) and (i)(2)(ii) of this section for the facility. 

(i) Annual CO2 emissions from all blowdown vent stacks at the facility, in metric tons 

CO2 (the sum of all CO2 mass emission values calculated according to § 98.233(i)(3), for all flow 

meters). 

(ii) Annual CH4 emissions from all blowdown vent stacks at the facility, in metric tons 

CH4, (the sum of all CH4 mass emission values calculated according to § 98.233(i)(3), for all 

flow meters). 

(j) Onshore production storage tanks. You must indicate whether your facility sends 

produced oil to atmospheric tanks. If your facility sends produced oil to atmospheric tanks, then 

you must indicate which Calculation Method(s) you used to calculate GHG emissions, and you 

must report the information specified in paragraphs (j)(1) and (j)(2) of this section as applicable. 

If any atmospheric tanks were observed to have malfunctioning dump valves during the calendar 

year, then you must indicate that dump valves were malfunctioning and you must report the 

information specified in paragraph (j)(3) of this section. 
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(1) If you used Calculation Method 1 or Calculation Method 2 to calculate GHG 

emissions, then you must report the information specified in paragraphs (j)(1)(i) through 

(j)(1)(xiv) of this section for each sub-basin and by calculation method. 

(i) Sub-basin ID. 

(ii) Calculation method used, and name of the software package used if using Calculation 

Method 1. 

(iii) The total annual gas-liquid separator oil volume that is sent to applicable onshore 

production storage tanks, in barrels. 

(iv) The average gas-liquid separator temperature, in degrees. 

(v) The average gas-liquid separator pressure, in pounds per square inch gauge. 

(vi) The average sales oil or stabilized oil API gravity, in degrees. 

(vii) The minimum and maximum concentration (mole fraction) of CO2 in flash gas from 

onshore production storage tanks. 

(viii) The minimum and maximum concentration (mole fraction) of CH4 in flash gas from 

onshore production storage tanks. 

(ix) The number of wells sending oil to gas-liquid separators or directly to atmospheric 

tanks. 

(x) The number of atmospheric tanks. 

(xi) An estimate of the number of atmospheric tanks, not on well-pads, receiving your oil. 

(xii) If any emissions from the atmospheric tanks at your facility were controlled with 

vapor recovery systems, then you must report the information specified in paragraphs 

(j)(1)(xii)(A) through (j)(1)(xii)(E) of this section. 
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(A) The number of atmospheric tanks that control emissions with vapor recovery 

systems. 

(B) Total CO2 mass, in metric tons CO2, that was recovered during the calendar year 

using a vapor recovery system. 

(C) Total CH4 mass, in metric tons CH4, that was recovered during the calendar year 

using a vapor recovery system. 

(D) Annual CO2 emissions, in metric tons CO2, from atmospheric tanks equipped with 

vapor recovery systems. 

(E) Annual CH4 emissions, in metric tons CH4, from atmospheric tanks equipped with 

vapor recovery systems. 

(xiii) If any atmospheric tanks at your facility vented gas directly to the atmosphere 

without using a vapor recovery system or without flaring, then you must report the information 

specified in paragraphs (j)(1)(xiii)(A) through (j)(1)(xiii)(C) of this section. 

(A) The number of atmospheric tanks that vented gas directly to the atmosphere without 

using a vapor recovery system or without flaring. 

(B) Annual CO2 emissions, in metric tons CO2, that resulted from venting gas directly to 

the atmosphere. 

(C) Annual CH4 emissions, in metric tons CH4, that resulted from venting gas directly to 

the atmosphere. 

(xiv) If you controlled emissions from any atmospheric tanks at your facility with one or 

more flares, then you must report the information specified in paragraphs (j)(1)(xiv)(A) through 

(j)(1)(xiv)(D) of this section. 

(A) The number of atmospheric tanks that controlled emissions with flares. 
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(B) Annual CO2 emissions, in metric tons CO2, from atmospheric tanks that controlled 

emissions with one or more flares. 

(C) Annual CH4 emissions, in metric tons CH4, from atmospheric tanks that controlled 

emissions with one or more flares. 

(D) Annual N2O emissions, in metric tons N2O, from atmospheric tanks that controlled 

emissions with one or more flares. 

(2) If you used Calculation Method 3 to calculate GHG emissions, then you must report 

the information specified in paragraph (j)(2)(i) through (j)(2)(iii) of this paragraph. 

(i) Report the information specified in paragraphs (j)(2)(i)(A) through (j)(2)(i)(F) of this 

section, at the basin level, for atmospheric tanks where emissions were calculated using 

Calculation Method 3. 

(A) The total annual oil throughput that is sent to all atmospheric tanks in the basin, in 

barrels. 

(B) An estimate of the fraction of oil throughput reported in paragraph (j)(2)(i)(A) sent to 

atmospheric tanks in the basin that controlled emissions with flares. 

(C) An estimate of the fraction of oil throughput reported in paragraph (j)(2)(i)(A) sent to 

atmospheric tanks in the basin that controlled emissions with vapor recovery systems. 

(D) The number of atmospheric tanks in the basin. 

(E) The number of wells with gas-liquid separators (“Count” from Equation W-15 of this 

subpart)in the basin. 

(F) The number of wells without gas-liquid separators (“Count” from Equation W-15 of 

this subpart)in the basin. 
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(ii) Report the information specified in paragraphs (j)(2)(ii)(A) through (j)(2)(ii)(D) of 

this section for each sub-basin with atmospheric tanks whose emissions were calculated using 

Calculation Method 3 and that did not control emissions with flares. 

(A) Sub-basin ID. 

(B) The number of atmospheric tanks in the sub-basin that did not control emissions with 

flares. 

(C) Annual CO2 emissions, in metric tons CO2, from atmospheric tanks in the sub-basin 

that did not control emissions with flares, calculated using Equation W-15 of this subpart. 

(D) Annual CH4 emissions, in metric tons CH4, from atmospheric tanks in the sub-basin 

that vented gas directly to the atmosphere, calculated using Equation W-15 of this subpart. 

(iii) Report the information specified in paragraphs (j)(2)(iii)(A) through (j)(2)(iii)(E) of 

this section for each sub-basin with atmospheric tanks whose emissions were calculated using 

Calculation Method 3 and that controlled emissions with flares. 

(A) Sub-basin ID. 

(B) The number of atmospheric tanks in the sub-basin that controlled emissions with 

flares. 

(C) Annual CO2 emissions, in metric tons CO2, from atmospheric tanks that controlled 

emissions with flares. 

(D) Annual CH4 emissions, in metric tons CH4, from atmospheric tanks that controlled 

emissions with flares. 

(E) Annual N2O emissions, in metric tons N2O, from atmospheric tanks that controlled 

emissions with flares. 
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(3) If any gas-liquid separator liquid dump values did not close properly during the 

calendar year, then you must report the information specified in paragraphs (j)(3)(i) through 

(j)(3)(iv) of this section. 

(i) The total number of gas-liquid separators whose liquid dump valves did not close 

properly during the calendar year. 

(ii) The total time the dump valves on gas-liquid separators did not close properly in the 

calendar year, in hours (“Tn” in Equation W-16 of this subpart). 

(iii) Annual CO2 emissions, in metric tons CO2, that resulted from dump valves on gasliquid separators not closing properly during the calendar year, calculated using Equation W-16 

of this subpart. 

(iv) Annual CH4 emissions, in metric tons CH4, that resulted from the dump valves on 

gas-liquid separators not closing properly during the calendar year, calculated using Equation W16 of this subpart. 

(k) Transmission storage tanks. You must indicate whether your facility contains any 

transmission storage tanks. If your facility contains at least one transmission storage tank, then 

you must report the information specified in paragraphs (k)(1) through (k)(3) of this section for 

each transmission storage tank vent stack. 

(1) For each transmission storage tank vent stack, report the information specified in 

(k)(1)(i) through (k)(1)(iv) of this section. 

(i) The unique name or ID number for the transmission storage tank vent stack. 

(ii) Method used to determine if dump valve leakage occurred. 

(iii) Indicator whether scrubber dump valve leakage occurred for the transmission storage 

tank vent. 
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(iv) Indicator if there is a flare attached to the transmission storage tank vent stack. 

(2) If scrubber dump valve leakage occurred for a transmission storage tank vent stack, as 

reported in paragraph (k)(1)(iii), and the vent stack vented directly to the atmosphere during the 

calendar year, then you must report the information specified in paragraphs (k)(2)(i) through 

(k)(2)(v) of this section for each transmission storage vent stack where scrubber dump valve 

leakage occurred. 

(i) Method used to measure the leak rate. 

(ii) Measured leak rate (average leak rate from a continuous flow measurement device), 

in standard cubic feet per hour. 

(iii) Duration of time that venting occurred, in hours (may use best available data if a 

continuous flow measurement device was used). 

(iv) Annual CO2 emissions, in metric tons CO2, that resulted from venting gas directly to 

the atmosphere, calculated according to § 98.233(k)(1) through (k)(3). 

(v) Annual CH4 emissions, in metric tons CH4, that resulted from venting gas directly to 

the atmosphere, calculated according to § 98.233(k)(1) through (k)(3). 

(3) If scrubber dump valve leakage occurred for a transmission storage tank vent stack, as 

reported in paragraph (k)(1)(iii), and the vent stack vented to a flare during the calendar year, 

then you must report the information specified in paragraphs (k)(3)(i) through (k)(3)(vi) of this 

section. 

 (i) Method used to measure the leak rate. 

(ii) Measured leakage rate (average leak rate from a continuous flow measurement 

device) in standard cubic feet per hour. 
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(iii) Duration of time that flaring occurred in hours (may use best available data if a 

continuous flow measurement device was used). 

(iv) Annual CO2 emissions, in metric tons CO2, that resulted from flaring gas, calculated 

according to § 98.233(k)(4). 

(v) Annual CH4 emissions, in metric tons CH4, that resulted from flaring gas, calculated 

according to § 98.233(k)(4). 

(vi) Annual N2O emissions, in metric tons N2O, that resulted from flaring gas, calculated 

according to § 98.233(k)(4). 

(l) Well testing. You must indicate whether you performed gas well or oil well testing, 

and if the testing of gas wells or oil wells resulted in vented or flared emissions during the 

calendar year. If you performed well testing that resulted in vented or flared emissions during the 

calendar year, then you must report the information specified in paragraphs (l)(1) through (l)(4) 

of this section, as applicable. 

(1) If you used Equation W-17A to calculate annual volumetric natural gas emissions at 

actual conditions from oil wells and the emissions are not vented to a flare, then you must report 

the information specified in paragraphs (l)(1)(i) through (l)(1)(vi) of this section. 

(i) Number of wells tested in the calendar year. 

(ii) Average number of well testing days in the calendar year. 

(iii) Average gas to oil ratio for well(s) tested, in cubic feet of gas per barrel of oil. 

(iv) Average flow rate for well(s) tested, in barrels of oil per day. 

(v) Annual CO2 emissions, in metric tons CO2, calculated according to § 98.233(l). 

(vi) Annual CH4 emissions, in metric tons CH4, calculated according to § 98.233(l). 
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(2) If you used Equation W-17A to calculate annual volumetric natural gas emissions at 

actual conditions from oil wells and the emissions are vented to a flare, then you must report the 

information specified in paragraphs (l)(2)(i) through (l)(2)(vii) of this section. 

(i) Number of wells tested in the calendar year. 

(ii) Average number of well testing days in the calendar year. 

(iii) Average gas to oil ratio for well(s) tested, in cubic feet of gas per barrel of oil. 

(iv) Average flow rate for well(s) tested, in barrels of oil per day. 

(v) Annual CO2 emissions, in metric tons CO2, calculated according to § 98.233(l). 

(vi) Annual CH4 emissions, in metric tons CH4, calculated according to § 98.233(l). 

(vii) Annual N2O emissions, in metric tons N2O, calculated according to § 98.233(l). 

(3) If you used Equation W-17B to calculate annual volumetric natural gas emissions at 

actual conditions from gas wells and the emissions were not vented to a flare, then you must 

report the information specified in paragraphs (l)(3)(i) through (l)(3)(v) of this section. 

(i) Number of wells tested in the calendar year. 

(ii) Average number of well testing days in the calendar year. 

(iii) Average annual production rate for well(s) tested, in actual cubic feet per day. 

(iv) Annual CO2 emissions, in metric tons CO2, calculated according to § 98.233(l). 

(v) Annual CH4 emissions, in metric tons CH4, calculated according to § 98.233(l). 

(4) If you used Equation W-17B to calculate annual volumetric natural gas emissions at 

actual conditions from gas wells and the emissions were vented to a flare, then you must report 

the information specified in paragraphs (l)(4)(i) through (l)(4)(vi) of this section. 

(i) Number of wells tested in calendar year. 

(ii) Average number of well testing days in the calendar year. 
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(iii) Average annual production rate for well(s) tested, in actual cubic feet per day. 

(iv) Annual CO2 emissions, in metric tons CO2, calculated according to § 98.233(l). 

(v) Annual CH4 emissions, in metric tons CH4, calculated according to § 98.233(l). 

(vi) Annual N2O emissions, in metric tons N2O, calculated according to § 98.233(l). 

(m) Associated natural gas. You must indicate whether any associated gas was vented or 

flared during the calendar year. If associated gas was vented or flared during the calendar year, 

then you must report the information specified in paragraphs (m)(1) through (m)(9) of this 

section for each sub-basin. 

(1) Sub-basin ID. 

(2) Indicator whether any associated gas was vented directly to the atmosphere without 

flaring. 

(3) Indicator whether any associated gas was flared. 

(4) Average gas to oil ratio, in standard cubic feet of gas per barrel of oil (average of the 

“GOR” values used in Equation W-18 of this subpart). 

(5) Volume of oil produced, in barrels, in the calendar year during the time periods in 

which associated gas was vented or flared (the sum of “Vp,q” used in Equation W-18 of this 

subpart). 

(6) Total volume of associated gas sent to sales, in standard cubic feet, in the calendar 

year during time periods in which associated gas was vented or flared (the sum of “SG” values 

used in Equation W-18 of this subpart). 

(7) Total volume of emissions reported elsewhere, in standard cubic feet, during time 

periods in which associated gas was vented or flared and which are calculated and reported under 
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other paragraphs of this section, in standard cubic feet (the sum of “EREp,q” values used in 

Equation W-18 of this subpart). 

(8) If you had associated gas emissions directly to the atmosphere without flaring, then 

you must report the information specified in paragraphs (m)(8)(i) through (m)(8)(iii) of this 

section for each sub-basin. 

(i) Total number of wells for which associated gas was vented directly to the atmosphere 

without flaring. 

(ii) Annual CO2 emissions, in metric tons CO2, calculated according to § 98.233(m)(3) 

and (m)(4). 

(iii) Annual CH4 emissions, in metric tons CH4, calculated according to § 98.233(m)(3) 

and (m)(4). 

(9) If you had associated gas emissions that were flared, then you must report the 

information specified in paragraphs (m)(9)(i) through (m)(9)(iv) of this section for each subbasin. 

(i) Total number of wells for which associated gas was flared. 

(ii) Annual CO2 emissions, in metric tons CO2, calculated according to § 98.233(m)(5). 

(iii) Annual CH4 emissions, in metric tons CH4, calculated according to § 98.233(m)(5). 

(iv) Annual N2O emissions, in metric tons N2O, calculated according to § 98.233(m)(5). 

(n) Flare stacks. You must indicate if your facility contains any flare stacks. You must 

report the information specified in paragraphs (n)(1) through (n)(12) of this section for each flare 

stack at your facility, and for each industry segment applicable to your facility. 
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(1) Unique name or ID for the flare stack. For the onshore petroleum and natural gas 

production industry segment, a different name or ID may be used for a single flare stack for each 

location where it operates at in a given calendar year. 

(2) Indicate whether the flare stack has a continuous flow measurement device. 

(3) Indicate whether the flare stack has a continuous gas composition analyzer on feed 

gas to the flare. 

(4) Volume of gas sent to the flare, in standard cubic feet (“Va” in Equation W-19 of this 

subpart). 

(5) Fraction of the feed gas sent to an un-lit flare (“Zu” in Equation W-19 of this subpart). 

(6) Flare combustion efficiency, expressed as the fraction of gas combusted by a burning 

flare. 

(7) Mole fraction of CH4 in the feed gas to the flare (“XCH4” in Equation W-19 of this 

subpart). 

(8) Mole fraction of CO2 in the feed gas to the flare (“XCO2” in Equation W-20 of this 

subpart). 

(9) Annual CO2 emissions, in metric tons CO2 (refer to Equation W-20 of this subpart).

(10) Annual CH4 emissions, in metric tons CH4 (refer to Equation W-19 of this subpart). 

(11) Annual N2O emissions, in metric tons N2O (refer to Equation W-40 of this subpart). 

(12) Indicate whether a CEMS was used to measure emissions from the flare. If a CEMS 

was used to measure emissions from the flare, then you are not required to report N2O and CH4

emissions for the flare stack. 

(o) Centrifugal compressors. You must indicate whether your facility has centrifugal 

compressors. You must report the information specified in paragraphs (o)(1) and (o)(2) of this 
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section for all centrifugal compressors at your facility. For each compressor source or 

manifolded group of compressor sources that you conduct as found leak measurements as 

specified in § 98.233(o)(2) or (o)(4), you must report the information specified in paragraph 

(o)(3) of this section. For each compressor source or manifolded group of compressor sources 

that you conduct continuous monitoring as specified in § 98.233(o)(3) or (o)(5), you must report 

the information specified in paragraph (o)(4) of this section. Centrifugal compressors in onshore 

petroleum and natural gas production are not required to report information in paragraphs (o)(1) 

through (o)(4) of this section and instead must report the information specified in paragraph 

(o)(5) of this section. 

(1) Compressor activity data. Report the information specified in paragraphs (o)(1)(i) 

through (o)(1)(xvi) of this section for each compressor located at your facility. 

(i) Unique name or ID for the centrifugal compressor. 

(ii) Hours in operating-mode. 

(iii) Hours in not-operating-depressurized-mode. 

(iv) Indicate whether the compressor was measured in operating-mode. 

(v) Indicate whether the compressor was measured in not-operating-depressurized-mode. 

(vi) Indicate whether any compressor sources are part of a manifolded group of 

compressor sources. 

(vii) Indicate whether any compressor sources are routed to a flare. 

(viii) Indicate whether any compressor sources have vapor recovery. 

(ix) Indicate whether emissions from any compressor sources are captured for fuel use or 

are routed to a thermal oxidizer. 

(x) Indicate whether the compressor has blind flanges installed. 
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(xi) Indicate whether the compressor has wet or dry seals. 

(xii) If the compressor has wet seals, the number of wet seals. 

(xiii) Compressor power rating (hp). 

(xiv) Year compressor was installed. 

(xv) Compressor model name and description. 

(xvi) Date of last maintenance shutdown that compressor was depressurized. 

(2) Compressor source emission vent . For each compressor source at each compressor, 

report the information specified in paragraphs (o)(2)(i) through (o)(2)(viii) of this section. 

(i) Centrifugal compressor name or ID. Use the same ID as in paragraph (o)(1)(i) of this 

section. 

(ii) Centrifugal compressor source (wet seal, isolation valve, or blowdown valve). 

(iii) Unique name or ID for the emission vent. If the emission vent is connected to a 

manifolded group of compressor sources, use the same emission vent ID for each compressor 

source. 

(iv) Emission vent type. Indicate whether the emission vent is for a single compressor 

source or manifolded group of compressor sources and whether the emissions from the emission 

vent are released to the atmosphere, routed to a flare, combustion (fuel or thermal oxidizer), or 

vapor recovery. 

(v) Indicate whether an as found leak measurement(s) as identified in § 98.233(o)(2) or 

(o)(4) was conducted on the emission vent. 

(vi) Indicate whether continuous leak measurements as identified in § 98.233(o)(3) or 

(o)(5) were conducted on the emission vent. 
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(vii) Report emissions as specified in paragraphs (o)(2)(vii)(A) and (o)(2)(vii)(B) of this 

section for the emission vent. For emission vents associated with individual compressor sources 

that use an as found leak measurement(s), calculate emissions by summing all emissions from all 

compressor mode-source combinations for the emission vent. 

(A) Annual CO2 emissions, in metric tons CO2.

(B) Annual CH4 emissions, in metric tons CH4. 

(viii) If the emission vent is routed to flare, combustion, or vapor recovery, report the 

percentage of time that the respective device was operational. 

(3) As found leak measurement sample data. If the measurement methods specified in 

paragraphs § 98.233(o)(2) or (o)(4) are conducted, report the information specified in paragraph 

(o)(3)(i) of this section. If the measurement method specified in paragraph § 98.233(o)(2) is 

performed, report the information specified in paragraph (o)(3)(ii) of this section. 

(i) For each as found leak measurement performed on an emission vent, report the 

information specified in paragraphs (o)(3)(i)(A) through (o)(3)(i)(E) of this section. 

(A) Name or ID of emission vent. Use same emission vent ID as in paragraph (o)(2)(iii) 

of this section. 

(B) Sample date. 

(C) Leak measurement method. 

(D) Measured flow rate, in standard cubic feet per hour. 

(E) For each compressor attached to the emission vent, report the mode of operation the 

compressor was in when the sample was taken. 
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(ii) For each compressor mode-source combination where a reporter emission factor as 

calculated in equation W-24 was used to calculate emissions in Equation W-23, report the 

information specified in paragraphs (o)(3)(ii)(A) through (o)(3)(ii)(D) of this section 

(A)The compressor mode-source combination. 

(B) The compressor mode-source combination reporter emission factor, in standard cubic 

feet per hour (EFm,s in Equation W-24). 

(C) The total number of compressors measured in the compressor mode-source 

combination in the current reporting year and the preceding two reporting years (Countm in 

Equation W-24). 

(D) Indicate whether the compressor mode-source combination reporter emission factor 

is facility-specific or corporate. 

(4) Continuous leak measurement data. If the measurement methods specified in 

paragraphs § 98.233(o)(3) or (o)(5) are conducted, report the information specified in paragraphs 

(o)(4)(i) and (o)(4)(ii) of this section for each continuous measurement conducted on each 

emission vent associated with each compressor source or manifolded group of compressor 

sources. 

(i) Name or ID of emission vent. Use same emission vent ID as in paragraph (o)(2)(iii) of 

this section. 

(ii) Measured volume of flow during the reporting year, in million standard cubic feet. 

(5) Centrifugal compressors with wet seal degassing vents in onshore petroleum and 

natural gas production must report the information specified in paragraphs (o)(5)(i) through 

(o)(5)(iii) of this section. 

(i) Number of centrifugal compressors that have wet seal oil degassing vents. 
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(ii) Annual CO2 emissions, in metric tons CO2, from centrifugal compressors with wet 

seal oil degassing vents.

(iii) Annual CH4 emissions, in metric tons CH4, from centrifugal compressors with wet 

seal oil degassing vents. 

(p) Reciprocating compressors. You must indicate whether your facility has reciprocating 

compressors. You must report the information specified in paragraphs (p)(1) and (p)(2) of this 

section for all reciprocating compressors at your facility. For each compressor source or 

manifolded group of compressor sources that you conduct as found leak measurements as 

specified in § 98.233(p)(2) or (p)(4), you must report the information specified in paragraph 

(p)(3) of this section. For each compressor source or manifolded group of compressor sources 

that you conduct continuous monitoring as specified in § 98.233(p)(3) or (p)(5), you must report 

the information specified in paragraph (p)(4) of this section. Reciprocating compressors in 

onshore petroleum and natural gas production are not required to report information in 

paragraphs (p)(1) through (p)(4) of this section and instead must report the information specified 

in paragraph (p)(5) of this section. 

(1) Compressor activity data. Report the information specified in paragraphs (p)(1)(i) 

through (p)(1)(xvi) of this section for each compressor located at your facility. 

(i) Unique name or ID for the reciprocating compressor. 

(ii) Hours in operating-mode. 

(iii) Hours in standby-depressurized-mode. 

(iv) Hours in not-operating-depressurized-mode. 

(v) Indicate whether the compressor was measured in operating-mode. 

(vi) Indicate whether the compressor was measured in standby-depressurized-mode. 
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(vii) Indicate whether the compressor was measured in not-operating-depressurizedmode. 

(viii) Indicate whether any compressor sources are part of a manifolded group of 

compressor sources. 

(ix) Indicate whether any compressor sources are routed to a flare. 

(x) Indicate whether any compressor sources have vapor recovery. 

(xi) Indicate whether emissions from any compressor sources are captured for fuel use or 

are routed to a thermal oxidizer. 

(xii) Indicate whether the compressor has blind flanges installed. 

(xiii) Compressor power rating (hp). 

(xiv) Year compressor was installed. 

(xv) Compressor model name and description. 

(xvi) Date of last maintenance shutdown for rod packing replacement. 

(2) Compressor source emission vent. For each compressor source at each compressor, 

report the information specified in paragraphs (p)(2)(i) through (p)(2)(viii) of this section. 

(i) Reciprocating compressor name or ID. Use the same ID as in paragraph (p)(1)(i) of 

this section. 

(ii) Reciprocating compressor source (isolation valve, blowdown valve, or rod packing). 

(iii) Unique name or ID for the emission vent. If the emission vent is connected to a 

manifolded group of compressor sources, use the same emission vent ID for each compressor 

source. 

(iv) Emission vent type. Indicate whether the emission vent is for a single compressor 

source or manifolded group of compressor sources and whether the emissions from the emission 
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vent are released to the atmosphere, routed to a flare, combustion (fuel or thermal oxidizer), or 

vapor recovery. 

(v) Indicate whether an as found leak measurement(s) as identified in § 98.233(p)(2) or 

(p)(4) was conducted on the emission vent. 

(vi) Indicate whether continuous leak measurements as identified in § 98.233(p)(3) or 

(p)(5) were conducted on the emission vent. 

(vii) Report emissions as specified in paragraphs (p)(2)(vii)(A) and (p)(2)(vii)(B) of this 

section for the emission vent. For emission vents associated with individual compressor sources 

that use an as found leak measurement(s), calculate emissions by summing all emissions from all 

compressor mode-source combinations for the emission vent. 

(A) Annual CO2 emissions, in metric tons CO2.

(B) Annual CH4 emissions, in metric tons CH4. 

(viii) If the emission vent is routed to flare, combustion, or vapor recovery, report the 

percentage of time that the respective device was operational. 

(3) As found leak measurement sample data. If the measurement methods specified in 

paragraphs § 98.233(p)(2) or (p)(4) are conducted, report the information specified in paragraph 

(p)(3)(i) of this section. If the measurement method specified in paragraph § 98.233(p)(2) is 

performed, report the information specified in paragraph (p)(3)(ii) of this section. 

(i) For each as found leak measurement performed on an emission vent, report the 

information specified in paragraphs (p)(3)(i)(A) through (p)(3)(i)(E) of this section. 

(A) Name or ID of emission vent. Use same emission vent ID as in paragraph (p)(2)(iii) 

of this section. 

(B) Sample date. 
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(C) Leak measurement method. 

(D) Measured flow rate, in standard cubic feet per hour. 

(E) For each compressor attached to the emission vent, report the mode of operation the 

compressor was in when the sample was taken. 

(ii) For each compressor mode-source combination where a reporter emission factor as 

calculated in equation W-28 was used to calculate emissions in Equation W-27, report the 

information specified in paragraphs (p)(3)(ii)(A) through (p)(3)(ii)(D) of this section 

(A) The compressor mode-source combination. 

(B) The compressor mode-source combination reporter emission factor, in standard cubic 

feet per hour (EFm,s in Equation W-28). 

(C) The total number of compressors measured in the compressor mode-source 

combination in the current reporting year and the preceding two reporting years (Countm in 

Equation W-28). 

(D) Indicate whether the compressor mode-source combination reporter emission factor 

is facility-specific or corporate. 

(4) Continuous leak measurement data. If the measurement methods specified in 

paragraphs § 98.233(p)(3) or (p)(5) are conducted, report the information specified in paragraphs 

(p)(4)(i) and (p)(4)(ii) of this section for each continuous measurement conducted on each 

emission vent associated with each compressor source or manifolded group of compressor 

sources. 

(i) Name or ID of emission vent. Use same emission vent ID as in paragraph (p)(2)(iii) of 

this section. 

(ii) Measured volume of flow during the reporting year, in million standard cubic feet. 
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(5) Reciprocating compressors in onshore petroleum and natural gas production must 

report the information specified in paragraphs (p)(5)(i) through (p)(5)(iii) of this section. 

(i) Number of reciprocating compressors. 

(ii) Annual CO2 emissions, in metric tons CO2, from reciprocating compressors.

(iii) Annual CH4 emissions, in metric tons CH4, from reciprocating compressors. 

(q) Equipment leak surveys. If your facility is subject to the requirements of § 98.233(q), 

then you must report the information specified in paragraphs (q)(1) and (q)(2) of this section. 

Natural gas distribution facilities must also report the information specified in paragraph (q)(3) 

of this section. 

(1) You must report the information specified in paragraphs (q)(1)(i) and (ii) of this 

section. 

(i) The number of complete equipment leak surveys performed during the calendar year. 

(ii) Natural gas distribution facilities performing equipment leak surveys across a 

multiple year leak survey cycle must report the number of years in the leak survey cycle. 

(2) You must indicate whether your facility contains any of the component types listed in 

§ 98.232(d)(7), (e)(7), (f)(5), (g)(3), (h)(4), or (i)(1), for your facility’s industry segment. For 

each component type that is located at your facility, you must report the information specified in 

paragraphs (q)(2)(i) through (q)(2)(v) of this section. If a component type is located at your 

facility and no leaks were identified from that component, then you must report the information 

in paragraphs (q)(2)(i) through (q)(2)(v) of this section but report a zero (“0”) for the information 

required according to paragraphs (q)(2)(iii), (q)(2)(iv), and (q)(2)(v) of this section. 

(i) Component type. 
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(ii) Total number of the surveyed component type that were identified as leaking in the 

calendar year (“xp” in Equation W-30 of this subpart for the component type). 

(iii) Average time the surveyed components were found leaking and operational, in hours 

(average of “Tp,z” from Equation W-30 of this subpart for the component type). 

(iv) Annual CO2 emissions, in metric tons CO2, for the component type. 

(v) Annual CH4 emissions, in metric tons CH4, for the component type. 

(3) Natural gas distribution facilities must report the information specified in paragraphs 

(q)(3)(i) through (q)(3)(viii) of this section. 

(i) Number of above grade transmission-distribution transfer stations surveyed in the 

calendar year. 

(ii) Number of meter/regulator runs at above grade transmission-distribution transfer 

stations surveyed in the calendar year (“CountMR,y” from Equation W-31 of this subpart, for the 

current calendar year). 

 (iii) Average time that meter/regulator runs surveyed in the calendar year were 

operational, in hours (average of “Tw,y” from Equation W-31 of this subpart, for the current 

calendar year). 

(iv) Number of above grade transmission-distribution transfer stations surveyed in the 

current leak survey cycle. 

(v) Number of meter/regulator runs at above grade transmission-distribution transfer 

stations surveyed in current leak survey cycle (sum of “CountMR,y” from Equation W-31 of this 

subpart, for all calendar years in the current leak survey cycle). 
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(vi) Average time that meter/regulator runs surveyed in the current leak survey cycle 

were operational, in hours (average of “Tw,y” from Equation W-31 of this subpart, for all years 

included in the leak survey cycle). 

(vii) Meter/regulator run CO2 emission factor based on all surveyed transmissiondistribution transfer stations in the current leak survey cycle, in standard cubic feet of CO2 per 

meter/regulator run operating hour (“EFs,MR,i” for CO2 calculated using Equation W-31 of this 

subpart). 

(viii) Meter/regulator run CH4 emission factor based on all surveyed transmissiondistribution transfer stations in the current leak survey cycle, in standard cubic feet of CH4 per 

meter/regulator run operating hour (“EFs,MR,i” for CH4 calculated using Equation W-31 of this 

subpart). 

(r) Equipment leaks by population count. If your facility is subject to the requirements of 

§ 98.233(r), then you must report the information specified in paragraph (r)(1) of this section. 

Natural gas distribution facilities must also report the information specified in paragraph (r)(2) of 

this section. Onshore petroleum and natural gas production facilities must also report the 

information specified in paragraph (r)(3) of this section. 

(1) You must indicate whether your facility contains any of the emission source types 

covered by § 98.233(r), for the applicable industry segment. You must report the information 

specified in paragraphs (r)(1)(i) through (r)(1)(v) of this section separately for each emission 

source type that is located at your facility. Onshore petroleum and natural gas production 

facilities must report the information specified in paragraphs (r)(1)(i) through (r)(1)(v) of this 

section separately by component type, service type, and geographic location (i.e., Eastern U.S or 

Western U.S.). 
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(i) Emission source type. Onshore petroleum and natural gas production facilities must 

report the component type, service type and geographic location. 

(ii) Total number of the emission source type at the facility (“Counte” in Equation W-32A 

of this subpart). 

(iii) Average estimated time that the emission source type was operational in the calendar 

year, in hours (“Te” in Equation W-32A of this subpart). 

(iv) Annual CO2 emissions, in metric tons CO2, for the emission source type. 

(v) Annual CH4 emissions, in metric tons CH4, for the emission source type. 

(2) Natural gas distribution facilities must also report the information specified in 

paragraphs (q)(2)(i) through (q)(2)(viii) of this section. 

(i) Number of above grade transmission-distribution transfer stations at the facility. 

(ii) Number of above grade metering-regulating stations that are not transmissiondistribution transfer stations at the facility. 

(iii) Number of below grade transmission-distribution transfer stations at the facility. 

(iv) Number of below grade metering-regulating stations that are not transmissiondistribution transfer stations at the facility. 

(v) Total number of meter/regulator runs at above grade metering-regulating stations that 

are not above grade transmission-distribution transfer stations (“CountMR” in Equation W-32B of 

this subpart). 

(vi) Average estimated time that each meter/regulator run was operational in the calendar 

year, in hours per meter/regulator run (“Tw,avg” in Equation W-32B of this subpart). 

(vii) Annual CO2 emissions, in metric tons CO2, from above grade metering regulating 

stations that are not above grade transmission-distribution transfer stations. 
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(viii) Annual CH4 emissions, in metric tons CH4, from above grade metering regulating 

stations that are not above grade transmission-distribution transfer stations. 

(3) Onshore petroleum and natural gas production facilities must also report the 

information specified in paragraphs (r)(3)(i) and (r)(3)(ii) of this section. 

(i) Calculation method used. 

(ii) Onshore petroleum and natural gas production facilities must report the information 

specified in paragraphs (r)(3)(ii)(A) and (r)(3)(ii)(B) of this section, for each major equipment 

type, production type (i.e., natural gas or crude oil), and geographic location combination in 

Tables W-1B and W-1C of this subpart. 

(A) An indication of whether the facility contains the major equipment type. 

(B) If the facility does contain the equipment type, the count of the major equipment 

type. 

(s) Offshore petroleum and natural gas production. You must report the information 

specified in paragraphs (s)(1) through (s)(3) of this section for each emission source type listed 

in the most recent BOEMRE study. 

(1) Annual CO2 emissions, in metric tons CO2. 

(2) Annual CH4 emissions, in metric tons CH4. 

(3) Annual N2O emissions, in metric tons N2O. 

(t) [Reserved] 

(u) [Reserved] 

(v) [Reserved] 

(w) EOR injection pumps. You must indicate whether CO2 EOR injection was used at 

your facility during the calendar year and if any EOR injection pump blowdowns occurred 
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during the year. If any EOR injection pump blowdowns occurred during the calendar year, then 

you must report the information specified in paragraphs (w)(1) through (w)(8) of this section for 

each EOR injection pump system. 

(1) Sub-basin ID. 

(2) EOR injection pump system identifier. 

(3) Pump capacity, in barrels per day. 

(4) Total volume of EOR injection pump system equipment chambers, in cubic feet (“Vv” 

in Equation W-37 of this subpart). 

(5) Number of blowdowns for the EOR injection pump system in the calendar year. 

(6) Density of critical phase EOR injection gas, in kilograms per cubic foot(“Rc” in 

Equation W-37 of this subpart). 

(7) Mass fraction of CO2 in critical phase EOR injection gas (“GHGCO2” in Equation W37 of this subpart). 

(8) Annual CO2 emissions, in metric tons CO2, from EOR injection pump system 

blowdowns. 

(x) EOR hydrocarbon liquids. You must indicate whether hydrocarbon liquids were 

produced through EOR operations. If hydrocarbon liquids were produced through EOR 

operations, you must report the information specified in paragraphs (x)(1) through (x)(4) of this 

section for each sub-basin category with EOR operations. 

(1) Sub-basin ID. 

(2) Total volume of hydrocarbon liquids produced through EOR operations in the 

calendar year, in barrels (“Vhl” in Equation W-38 of this subpart). 
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(3) Average CO2 retained in hydrocarbon liquids downstream of the storage tank, in 

metric tons per barrel under standard conditions (“Shl” in Equation W-38 of this subpart). 

(4) Annual CO2 emissions, in metric tons CO2, from CO2 retained in hydrocarbon liquids 

produced through EOR operations downstream of the storage tank (“MassCO2” in Equation W-38 

of this subpart). 

(y) [Reserved] 

(z) Combustion equipment at onshore petroleum and natural gas production facilities and 

natural gas distribution facilities. If your facility is required by § 98.232(c)(22) or (i)(7) to report 

emissions from combustion equipment, then you must indicate whether your facility has any 

combustion units subject to reporting according to paragraphs (a)(1)(xvii) or (a)(8)(i) of this 

section. If your facility contains any combustion units subject to reporting according to 

paragraphs (a)(1)(xvii) or (a)(8)(i) of this section, then you must report the information specified 

in paragraphs (z)(1) and (z)(2) of this section, as applicable. 

(1) Indicate whether the combustion units include: external fuel combustion units with a 

rated heat capacity less than or equal to 5 million Btu per hour; or, internal fuel combustion units 

that are not compressor-drivers, with a rated heat capacity less than or equal to 1 mmBtu/hr (or 

the equivalent of 130 horsepower). If the facility contains external fuel combustion units with a 

rated heat capacity less than or equal to 5 million Btu per hour or internal fuel combustion units 

that are not compressor-drivers, with a rated heat capacity less than or equal to 1 million Btu per 

hour (or the equivalent of 130 horsepower), then you must report the information specified in 

paragraphs (z)(1)(i) and (z)(1)(ii) of this section for each unit type. 

(i) The type of combustion unit. 

(ii) The total number of combustion units. 
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(2) Indicate whether the combustion units include: external fuel combustion units with a 

rated heat capacity greater than 5 million Btu per hour; internal fuel combustion units that are not 

compressor-drivers, with a rated heat capacity greater than 1 million Btu per hour (or the 

equivalent of 130 horsepower); or, internal fuel combustion units of any heat capacity that are 

compressor-drivers. If your facility contains: external fuel combustion units with a rated heat 

capacity greater than 5 mmBtu/hr; internal fuel combustion units that are not compressor-drivers, 

with a rated heat capacity greater than 1 million Btu per hour (or the equivalent of 130 

horsepower); or internal fuel combustion units of any heat capacity that are compressor-drivers, 

then you must report the information specified in paragraphs (z)(2)(i) through (z)(2)(vi) for each 

combustion unit type and fuel type combination. 

(i) The type of combustion unit. 

(ii) The type of fuel combusted. 

(iii) The quantity of fuel combusted in the calendar year, in thousand standard cubic feet, 

gallons, or tons. 

(iv) Annual CO2 emissions, in metric tons CO2, calculated according to § 98.233(z)(1) 

and (z)(2). 

(v) Annual CH4 emissions, in metric tons CH4, calculated according to § 98.233(z)(1) and 

(z)(2). 

(vi) Annual N2O emissions, in metric tons N2O, calculated according to § 98.233(z)(1) 

and (z)(2). 

(aa) Each facility must report the information specified in paragraphs (aa)(1) through 

(aa)(9) of this section, for each applicable industry segment, by using best available data. If a 

quantity required to be reported is zero, you must report zero as the value. 
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(1) For onshore petroleum and natural gas production, report the data specified in 

paragraphs (aa)(1)(i) and (aa)(1)(ii) of this section. 

(i) Report the information specified in paragraphs (aa)(1)(i)(A) through (aa)(1)(i)(D) of 

this section for the basin as a whole. 

(A) The quantity of gas produced in the calendar year from wells, in thousand standard 

cubic feet. This includes gas that is routed to a pipeline, vented or flared, or used in field 

operations. This does not include gas injected back into reservoirs or shrinkage resulting from 

lease condensate production. 

(B) The quantity of gas produced in the calendar year for sales, in thousand standard 

cubic feet. 

(C) The quantity of crude oil ratio, and best available estimate ofproduced in the calendar 

year for sales, not including lease condensates, in barrels. 

(D) The quantity of lease condensate produced in the calendar year for sales, in barrels. 

(ii) Report the information specified in paragraphs (aa)(1)(ii)(A) through (aa)(1)(ii)(M) of 

this section for each unique sub-basin category. 

(A) State. 

(B) County. 

(C) Formation type. 

(D) The number of producing wells at the end of the calendar year. 

(E) The number of producing wells acquired during the calendar year. 

(F) The number of producing wells divested during the calendar year. 

(G) The number of wells completed during the calendar year. 

(H) The number of wells taken out of production during the calendar year. 
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(I) Average mole fraction of CH4 in produced gas. 

(J) Average mole fraction of CO2 in produced gas. 

(K) If an oil sub-basin, report the average GOR of all wells, in thousand standard cubic 

feet per barrel. 

(L) If an oil sub-basin, report the average API gravity of all wells. 

(M) If an oil sub-basin, report average low pressure separator pressure, in pounds per 

square inch gauge. 

(2) For offshore production, report the quantities specified in paragraphs (aa)(2)(i) 

through (aa)(2)(iii) of this section. 

(i) The quantity of gas produced from the offshore platform in the calendar year for sales, 

in thousand standard cubic feet. 

(ii) The quantity of oil produced from the offshore platform in the calendar year for sales, 

in barrels. 

(iii) The quantity of condensate produced from the offshore platform in the calendar year 

for sales, in barrels. 

(3) For natural gas processing, report the quantities specified in paragraphs (aa)(3)(i) 

through (aa)(3)(vii) of this section. 

(i) The quantity of produced gas received at the gas processing plant in the calendar year, 

in thousand standard cubic feet. 

(ii) The quantity of processed (residue) gas leaving the gas processing plant in the 

calendar year, in thousand standard cubic feet. 

(iii) The quantity of NGLs (bulk and fractionated) received at the gas processing plant in 

the calendar year, in barrels. 
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(iv) The quantity of NGLs (bulk and fractionated) leaving the gas processing plant in the 

calendar year, in barrels. 

(v) Average mole fraction of CH4 in produced gas received. 

(vi) Average mole fraction of CO2 in produced gas received. 

(vii) Indicate whether the facility fractionates NGLs. 

(4) For natural gas transmission compression, report the quantity specified in paragraphs 

(aa)(4)(i) through (aa)(4)(v) of this section. 

(i) The quantity of gas transported through the compressor station in the calendar year, in 

thousand standard cubic feet. 

(ii) Number of compressors. 

(iii) Total compressor power rating of all compressors combined, in horsepower. 

(iv) Average upstream pipeline pressure, in pounds per square inch gauge. 

(v) Average downstream pipeline pressure, in pounds per square inch gauge. 

(5) For underground natural gas storage, report the quantities specified in paragraphs 

(aa)(5)(i) through (aa)(5)(iii) of this section. 

(i) The quantity of gas injected into storage in the calendar year, in thousand standard 

cubic feet. 

(ii) The quantity of gas withdrawn from storage in the calendar year, in thousand standard 

cubic feet. 

(iii) Total storage capacity, in thousand standard cubic feet. 

(6) For LNG import equipment, report the quantity of LNG imported in the calendar year, 

in thousand standard cubic feet. 
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(7) For LNG export equipment, report the quantity of LNG exported in the calendar year, 

in thousand standard cubic feet. 

(8) For LNG storage, report the quantities specified in paragraphs (aa)(8)(i) through 

(aa)(8)(iii) of this section. 

(i) The quantity of LNG added into storage in the calendar year, in thousand standard 

cubic feet. 

(ii) The quantity of LNG withdrawn from storage in the calendar year , in thousand 

standard cubic feet. 

(iii) Total storage capacity, in thousand standard cubic feet. 

(9) For natural gas distribution, report the quantities specified in paragraphs (aa)(9)(i) 

through (aa)(9)(vii) of this section. 

(i) The quantity of natural gas received at all custody transfer stations in the calendar 

year, in thousand standard cubic feet. This value may include meter corrections, but only for the 

calendar year covered by the annual report. 

(ii) The quantity of natural gas withdrawn from in-system storage in the calendar year, in 

thousand standard cubic feet. 

(iii) The quantity of natural gas added to in-system storage in the calendar year, in 

thousand standard cubic feet. 

(iv) The quantity of natural gas delivered to end users, in thousand standard cubic feet. 

This value does not include stolen gas, or gas that is otherwise unaccounted for. 

(v) The quantity of natural gas transferred to third parties such as other LDCs or 

pipelines, in thousand standard cubic feet. This value does not include stolen gas, or gas that is 

otherwise unaccounted for. 
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(vi) The quantity of natural gas consumed by the LDC for operational purposes, in 

thousand standard cubic feet. 

(vii) The estimated quantity of gas stolen in the calendar year, in thousand standard cubic 

feet. 

(bb) For any missing data procedures used, report the information in paragraphs (bb)(1) 

through (bb)(5) in this section for each individual missing data value used in a calculation. 

Aggregation of missing data values within a component, well, sub-basin, or basin is not 

acceptable. If missing data is substituted for the same parameter in non-consecutive periods 

during the calendar year, the information in paragraphs (bb)(1) through (bb)(5) in this section 

should be reported for each period separately. 

(1) The date(s) the missing data is used. 

(2) The equation(s) in which the missing data is used. 

(3) The description of the unique or unusual circumstance that led to missing data use, 

including information on any equipment or components involved and any procedures that were 

not followed. 

(4) The description of the procedures used to substitute an unavailable value of a 

parameter. 

(5) The description of how the owner or operator will avoid the use of missing data in the 

future, such as mitigation strategies or changes to standard operating procedures. 

§98.237 Records that must be retained. 

Monitoring Plans, as described in §98.3(g)(5), must be completed by April 1, 2011. In 

addition to the information required by §98.3(g), you must retain the following records: 

(a) Dates on which measurements were conducted. 
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(b) Results of all emissions detected and measurements. 

(c) Calibration reports for detection and measurement instruments used. 

(d) Inputs and outputs of calculations or emissions computer model runs used for 

engineering estimation of emissions. 

(e) The records required under §98.3(g)(2)(i) shall include an explanation of how 

company records, engineering estimation, or best available information are used to calculate each 

applicable parameter under this subpart. 

§98.238 Definitions. 

Except as provided in this section, all terms used in this subpart have the same meaning 

given in the Clean Air Act and subpart A of this part. 

Acid gas means hydrogen sulfide (H2S) and/or carbon dioxide (CO2) contaminants that 

are separated from sour natural gas by an acid gas removal unit. 

Acid gas removal unit (AGR) means a process unit that separates hydrogen sulfide and/or 

carbon dioxide from sour natural gas using liquid or solid absorbents or membrane separators. 

Acid gas removal vent emissions mean the acid gas separated from the acid gas absorbing 

medium (e.g., an amine solution) and released with methane and other light hydrocarbons to the 

atmosphere or a flare. 

Associated gas venting or flaring means the venting or flaring of natural gas which 

originates at wellheads that also produce hydrocarbon liquids and occurs either in a discrete 

gaseous phase at the wellhead or is released from the liquid hydrocarbon phase by separation. 

This does not include venting or flaring resulting from activities that are reported elsewhere, 

including tank venting, well completions, and well workovers. 
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Associated with a single well-pad means associated with the hydrocarbon stream as 

produced from one or more wells located on that single well-pad. The association ends where the 

stream from a single well-pad is combined with streams from one or more additional single wellpads, where the point of combination is located off that single well-pad. Onshore production 

storage tanks on or associated with a single well-pad are considered a part of the onshore 

production facility. 

Basin means geologic provinces as defined by the American Association of Petroleum 

Geologists (AAPG) Geologic Note: AAPG-CSD Geologic Provinces Code Map: AAPG 

Bulletin, Prepared by Richard F. Meyer, Laure G. Wallace, and Fred J. Wagner, Jr., Volume 75, 

Number 10 (October 1991) (incorporated by reference, see §98.7) and the Alaska Geological 

Province Boundary Map, Compiled by the American Association of Petroleum Geologists 

Committee on Statistics of Drilling in Cooperation with the USGS, 1978 (incorporated by 

reference, see §98.7). 

Component means each metal to metal joint or seal of non-welded connection separated 

by a compression gasket, screwed thread (with or without thread sealing compound), metal to 

metal compression, or fluid barrier through which natural gas or liquid can escape to the 

atmosphere.

Compressor means any machine for raising the pressure of a natural gas or CO2 by 

drawing in low pressure natural gas or CO2 and discharging significantly higher pressure natural 

gas or CO2. 

Compressor mode means the operational and pressurized status of a compressor. For a 

centrifugal compressor, “mode” refers to either operating -mode or not-operating-depressurized -
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mode. For a reciprocating compressor, “mode” refers to either: operating -mode, standbypressurized -mode, or not-operating-depressurized -mode. 

Compressor source means any type of vent or valve (i.e., wet seal, blowdown valve, 

isolation valve, or rod packing) on a centrifugal or reciprocating compressor.

Condensate means hydrocarbon and other liquid, including both water and hydrocarbon 

liquids, separated from natural gas that condenses due to changes in the temperature, pressure, or 

both, and remains liquid at storage conditions. 

Distribution pipeline means a pipeline that is designated as such by the Pipeline and 

Hazardous Material Safety Administration (PHMSA) 49 CFR 192.3. 

Engineering estimation, for purposes of subpart W, means an estimate of emissions based 

on engineering principles applied to measured and/or approximated physical parameters such as 

dimensions of containment, actual pressures, actual temperatures, and compositions. 

Enhanced oil recovery (EOR) means the use of certain methods such as water flooding or 

gas injection into existing wells to increase the recovery of crude oil from a reservoir. In the 

context of this subpart, EOR applies to injection of critical phase or immiscible carbon dioxide 

into a crude oil reservoir to enhance the recovery of oil. 

Equipment leak means those emissions which could not reasonably pass through a stack, 

chimney, vent, or other functionally-equivalent opening.

Equipment leak detection means the process of identifying emissions from equipment, 

components, and other point sources.

External combustion means fired combustion in which the flame and products of 

combustion are separated from contact with the process fluid to which the energy is delivered. 
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Process fluids may be air, hot water, or hydrocarbons. External combustion equipment may 

include fired heaters, industrial boilers, and commercial and domestic combustion units. 

Facility with respect to natural gas distribution for purposes of reporting under this 

subpart and for the corresponding subpart A requirements means the collection of all distribution 

pipelines and metering-regulating stations that are operated by a Local Distribution Company 

(LDC) within a single state that is regulated as a separate operating company by a public utility 

commission or that are operated as an independent municipally-owned distribution system. 

Facility with respect to natural gas distribution for purposes of reporting under this 

subpart and for the corresponding subpart A requirements means the collection of all distribution 

pipelines and metering-regulating stations that are operated by a Local Distribution Company 

(LDC) within a single state that is regulated as a separate operating company by a public utility 

commission or that are operated as an independent municipally-owned distribution system. 

Facility with respect to onshore petroleum and natural gas production for purposes of 

reporting under this subpart and for the corresponding subpart A requirements means all 

petroleum or natural gas equipment on a single well-pad or associated with a single well-pad and 

CO2e OR operations that are under common ownership or common control including leased, 

rented, or contracted activities by an onshore petroleum and natural gas production owner or 

operator and that are located in a single hydrocarbon basin as defined in §98.238. Where a 

person or entity owns or operates more than one well in a basin, then all onshore petroleum and 

natural gas production equipment associated with all wells that the person or entity owns or 

operates in the basin would be considered one facility. 
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Farm Taps are pressure regulation stations that deliver gas directly from transmission 

pipelines to generally rural customers. In some cases a nearby LDC may handle the billing of the 

gas to the customer(s). 

Field means oil and gas fields identified in the United States as defined by the Energy 

Information Administration Oil and Gas Field Code Master List 2008, DOE/EIA 0370(08) 

(incorporated by reference, see §98.7). 

Flare, for the purposes of subpart W, means a combustion device, whether at ground level 

or elevated, that uses an open or closed flame to combust waste gases without energy recovery. 

Flare combustion efficiency means the fraction of hydrocarbon gas, on a volume or mole 

basis, that is combusted at the flare burner tip. 

Flare stack emissions means CO2 and N2O from partial combustion of hydrocarbon gas 

sent to a flare plus CH4emissions resulting from the incomplete combustion of hydrocarbon gas 

in flares. 

Forced extraction of natural gas liquids means removal of ethane or higher carbon 

number hydrocarbons existing in the vapor phase in natural gas, by removing ethane or heavier 

hydrocarbons derived from natural gas into natural gas liquids by means of a forced extraction 

process. Forced extraction processes include but are not limited to refrigeration, absorption (lean 

oil), cryogenic expander, and combinations of these processes. Forced extraction does not 

include in and of itself; natural gas dehydration, or the collection or gravity separation of water 

or hydrocarbon liquids from natural gas at ambient temperature or heated above ambient 

temperatures, or the condensation of water or hydrocarbon liquids through passive reduction in 

pressure or temperature, or portable dewpoint suppression skids. 
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Horizontal well means a well bore that has a planned deviation from primarily vertical to 

a primarily horizontal inclination or declination tracking in parallel with and through the target 

formation. 

Internal combustion means the combustion of a fuel that occurs with an oxidizer (usually 

air) in a combustion chamber. In an internal combustion engine the expansion of the hightemperature and -pressure gases produced by combustion applies direct force to a component of 

the engine, such as pistons, turbine blades, or a nozzle. This force moves the component over a 

distance, generating useful mechanical energy. Internal combustion equipment may include 

gasoline and diesel industrial engines, natural gas-fired reciprocating engines, and gas turbines. 

Liquefied natural gas (LNG) means natural gas (primarily methane) that has been 

liquefied by reducing its temperature to -260 degrees Fahrenheit at atmospheric pressure. 

LNG boil-off gas means natural gas in the gaseous phase that vents from LNG storage 

tanks due to ambient heat leakage through the tank insulation and heat energy dissipated in the 

LNG by internal pumps. 

Manifolded compressor source means a compressor source (as defined in this section) 

that is manifolded to a common vent that routes gas from multiple compressors. 

Manifolded group of compressor sources means a collection of any combination of 

manifolded compressor sources (as defined in this section) that are manifolded to a common 

vent. 

Meter/regulator run means a series of components used in regulating pressure or metering 

natural gas flow or both. At least one meter, at least on regulator, or any combination of both on 

a single run of piping is considered one meter/regulator run.
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Metering-regulating station means a station that meters the flowrate, regulates the 

pressure, or both, of natural gas in a natural gas distribution facility. This does not include 

customer meters, customer regulators, or farm taps. 

Natural gas means a naturally occurring mixture or process derivative of hydrocarbon and 

non-hydrocarbon gases found in geologic formations beneath the earth’s surface, of which its 

constituents include, but are not limited to, methane, heavier hydrocarbons and carbon dioxide. 

Natural gas may be field quality, pipeline quality, or process gas. 

Offshore means seaward of the terrestrial borders of the United States, including waters 

subject to the ebb and flow of the tide, as well as adjacent bays, lakes or other normally standing 

waters, and extending to the outer boundaries of the jurisdiction and control of the United States 

under the Outer Continental Shelf Lands Act. 

Onshore petroleum and natural gas production owner or operator means the person or 

entity who holds the permit to operate petroleum and natural gas wells on the drilling permit or 

an operating permit where no drilling permit is issued, which operates an onshore petroleum 

and/or natural gas production facility (as described in §98.230(a)(2)). Where petroleum and 

natural gas wells operate without a drilling or operating permit, the person or entity that pays the 

State or Federal business income taxes is considered the owner or operator. 

Operating pressure means the containment pressure that characterizes the normal state of 

gas or liquid inside a particular process, pipeline, vessel or tank. 

Pressure groups as applicable to each sub-basin are defined as follows: Less than or equal 

to 25 psig; greater than 25 psig and less than or equal to 60 psig; greater than 60 psig and less 

than or equal to 110 psig; greater than 110 psig and less than or equal to 200 psig; and greater 

than 200 psig. The pressure in the context of pressure groups is either the well shut-in pressure; 
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well casing pressure; or you may use the casing-to-tubing pressure of one well from the same 

sub-basin multiplied by the tubing pressure for each well in the sub-basin. 

Pump means a device used to raise pressure, drive, or increase flow of liquid streams in 

closed or open conduits. 

Pump seals means any seal on a pump drive shaft used to keep methane and/or carbon 

dioxide containing light liquids from escaping the inside of a pump case to the atmosphere. 

Pump seal emissions means hydrocarbon gas released from the seal face between the 

pump internal chamber and the atmosphere. 

Reservoir means a porous and permeable underground natural formation containing 

significant quantities of hydrocarbon liquids and/or gases. 

Reduced emissions completion means a well completion following hydraulic fracturing 

where gas flowback that is otherwise vented is captured, cleaned, and routed to the flow line or 

collection system, re-injected into the well or another well, used as an on-site fuel source, or used 

for other useful purpose that a purchased fuel or raw material would serve, with no direct release 

to the atmosphere. 

Reduced emissions workover means a well workover with hydraulic fracturing (i.e., 

refracturing) where gas flowback that is otherwise vented is captured, cleaned, and routed to the 

flow line or collection system, re-injected into the well or another well, used as an on-site fuel 

source, or used for other useful purpose that a purchased fuel or raw material would serve, with 

no direct release to the atmosphere. 

Residue Gas and Residue Gas Compression mean, respectively, production lease natural 

gas from which gas liquid products and, in some cases, non-hydrocarbon components have been 

extracted such that it meets the specifications set by a pipeline transmission company, and/or a 
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distribution company; and the compressors operated by the processing facility, whether inside 

the processing facility boundary fence or outside the fence-line, that deliver the residue gas from 

the processing facility to a transmission pipeline. 

Separator means a vessel in which streams of multiple phases are gravity separated into 

individual streams of single phase. 

Sub-basin category, for onshore natural gas production, means a subdivision of a basin 

into the unique combination of wells with the surface coordinates within the boundaries of an 

individual county and subsurface completion in one or more of each of the following five 

formation types: Oil, high permeability gas, shale gas, coal seam, or other tight gas reservoir 

rock. The distinction between high permeability gas and tight gas reservoirs shall be designated 

as follows: High permeability gas reservoirs with >0.1 millidarcy permeability, and tight gas 

reservoirs with ≤0.1 millidarcy permeability. Permeability for a reservoir type shall be 

determined by engineering estimate. Wells that produce only from high permeability gas, shale 

gas, coal seam, or other tight gas reservoir rock are considered gas wells; gas wells producing 

from more than one of these formation types shall be classified into only one type based on the 

formation with the most contribution to production as determined by engineering knowledge. All 

wells that produce hydrocarbon liquids (with or without gas) and do not meet the definition of a 

gas well in this sub-basin category definition are considered to be in the oil formation. All 

emission sources that handle condensate from gas wells in high permeability gas, shale gas, or 

tight gas reservoir rock formations are considered to be in the formation that the gas well belongs 

to and not in the oil formation. 
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Transmission-distribution (T-D) transfer station means a metering-regulating station 

where a local distribution company takes part or all of the natural gas from a transmission 

pipeline and puts it into a distribution pipeline. 

Transmission pipeline means a Federal Energy Regulatory Commission rate-regulated 

Interstate pipeline, a state rate-regulated Intrastate pipeline, or a pipeline that falls under the 

“Hinshaw Exemption” as referenced in section 1(c) of the Natural Gas Act, 15 U.S.C. 717-717 

(w)(1994). 

Tubing diameter groups are defined as follows: Outer diameter less than or equal to 1 

inch; outer diameter greater than 1 inch and less than 2.375 inch; and outer diameter greater than 

or equal to 2.375 inch. 

Tubing systems means piping equal to or less than one half inch diameter as per nominal 

pipe size. 

Turbine meter means a flow meter in which a gas or liquid flow rate through the 

calibrated tube spins a turbine from which the spin rate is detected and calibrated to measure the 

fluid flow rate. 

Vented emissions means intentional or designed releases of CH4 or CO2 containing 

natural gas or hydrocarbon gas (not including stationary combustion flue gas), including process 

designed flow to the atmosphere through seals or vent pipes, equipment blowdown for 

maintenance, and direct venting of gas used to power equipment (such as pneumatic devices). 

Vertical well means a well bore that is primarily vertical but has some unintentional 

deviation or one or more intentional deviations to enter one or more subsurface targets that are 

off-set horizontally from the surface location, intercepting the targets either vertically or at an 

angle. 
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Well testing venting and flaring means venting and/or flaring of natural gas at the time 

the production rate of a well is determined for regulatory, commercial, or technical purposes. If 

well testing is conducted immediately after well completion or workover, then it is considered 

part of well completion or workover. 

Table W-1A of Subpart W of Part 98—Default Whole Gas Emission Factors for Onshore 

Petroleum and Natural Gas Production 

Onshore petroleum and 

natural gas production 

Emission factor 

(scf/hour/component) 

Eastern U.S. 

Population Emission Factors—All Components, Gas Service1

Valve 0.027 

Connector 0.003 

Open-ended Line 0.061 

Pressure Relief Valve 0.040 

Low Continuous Bleed Pneumatic Device Vents2 1.39 

High Continuous Bleed Pneumatic Device Vents2 37.3 

Intermittent Bleed Pneumatic Device Vents2 13.5 

Pneumatic Pumps3 13.3 

Population Emission Factors—All Components, Light Crude Service4

Valve 0.05 

Flange 0.003 

Connector 0.007 

Open-ended Line 0.05 

Pump 0.01 

Other 5 0.30 

Population Emission Factors—All Components, Heavy Crude Service6

Valve 0.0005 

Flange 0.0009 
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Onshore petroleum and 

natural gas production 

Emission factor 

(scf/hour/component) 

Connector (other) 0.0003 

Open-ended Line 0.006 

Other 5 0.003 

Western U.S. 

Population Emission Factors—All Components, Gas Service1

Valve 0.121 

Connector 0.017 

Open-ended Line 0.031 

Pressure Relief Valve 0.193 

Low Continuous Bleed Pneumatic Device Vents2 1.39 

High Continuous Bleed Pneumatic Device Vents2 37.3 

Intermittent Bleed Pneumatic Device Vents2 13.5 

Pneumatic Pumps3 13.3 

Population Emission Factors—All Components, Light Crude Service4

Valve 0.05 

Flange 0.003 

Connector (other) 0.007 

Open-ended Line 0.05 

Pump 0.01 

Other5 0.30 

Population Emission Factors—All Components, Heavy Crude Service6

Valve 0.0005 

Flange 0.0009 

Connector (other) 0.0003 

Open-ended Line 0.006 

Other5 0.003 

1 For multi-phase flow that includes gas, use the gas service emissions factors. 

2 Emission Factor is in units of “scf/hour/device.” 

3 Emission Factor is in units of “scf/hour/pump.” 
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4 Hydrocarbon liquids greater than or equal to 20°API are considered “light crude.” 

5 “Others” category includes instruments, loading arms, pressure relief valves, stuffing boxes, 

compressor seals, dump lever arms, and vents. 

6 Hydrocarbon liquids less than 20°API are considered “heavy crude.”

Table W-1B to Subpart W of Part 98—Default Average Component Counts for Major 

Onshore Natural Gas Production Equipment 

Major equipment Valves Connectors Open-ended lines Pressure relief valves 

Eastern U.S. 

Wellheads 8 38 0.5 0 

Separators 1 6 0 0 

Meters/piping 12 45 0 0 

Compressors 12 57 0 0 

In-line heaters 14 65 2 1 

Dehydrators 24 90 2 2 

Western U.S. 

Wellheads 11 36 1 0 

Separators 34 106 6 2 

Meters/piping 14 51 1 1 

Compressors 73 179 3 4 

In-line heaters 14 65 2 1 

Dehydrators 24 90 2 2 

Table W-1C to Subpart W of Part 98—Default Average Component Counts For Major 

Crude Oil Production Equipment 

Major equipment Valves Flanges Connectors Open-ended lines Other components 

Eastern U.S. 

Wellhead 5 10 4 0 1 

Separator 6 12 10 0 0 

Heater-treater 8 12 20 0 0 

Header 5 10 4 0 0 
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Major equipment Valves Flanges Connectors Open-ended lines Other components 

Western U.S. 

Wellhead 5 10 4 0 1 

Separator 6 12 10 0 0 

Heater-treater 8 12 20 0 0 

Header 5 10 4 0 0 

Table W-1D of Subpart W of Part 98—Designation of Eastern And Western U.S. 

Eastern U.S. Western U.S. 

Connecticut Alabama 

Delaware Alaska 

Florida Arizona 

Georgia Arkansas 

Illinois California 

Indiana Colorado 

Kentucky Hawaii 

Maine Idaho 

Maryland Iowa 

Massachusetts Kansas 

Michigan Louisiana 

New Hampshire Minnesota 

New Jersey Mississippi 

New York Missouri 

North Carolina Montana 

Ohio Nebraska 

Pennsylvania Nevada 

Rhode Island New Mexico 

South Carolina North Dakota 

Tennessee Oklahoma 
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Eastern U.S. Western U.S. 

Vermont Oregon 

Virginia South Dakota 

West Virginia Texas 

Wisconsin Utah 

 Washington 

 Wyoming 

Table W-2 of Subpart W of Part 98—Default Total Hydrocarbon Emission Factors for 

Onshore Natural Gas Processing 

Onshore natural gas processing plants 

Emission factor 

(scf/hour/component) 

Leaker Emission Factors—Compressor Components, Gas Service 

Valve1 14.84 

Connector 5.59 

Open-Ended Line 17.27 

Pressure Relief Valve 39.66 

Meter 19.33 

Leaker Emission Factors—Non-Compressor Components, Gas Service 

Valve1 6.42 

Connector 5.71 

Open-Ended Line 11.27 

Pressure Relief Valve 2.01 

Meter 2.93 

1 Valves include control valves, block valves and regulator valves. 

Table W-3 of Subpart W of Part 98—Default Total Hydrocarbon Emission Factors for 

Onshore Natural Gas Transmission Compression 

Onshore natural gas transmission compression Emission factor (scf/hour/component) 

Leaker Emission Factors—Compressor Components, Gas Service 

Valve 1 14.84 
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Onshore natural gas transmission compression Emission factor (scf/hour/component) 

Connector 5.59 

Open-Ended Line 17.27 

Pressure Relief Valve 39.66 

Meter 19.33 

Leaker Emission Factors—Non-Compressor Components, Gas Service 

Valve1 6.42 

Connector 5.71 

Open-Ended Line 11.27 

Pressure Relief Valve 2.01 

Meter 2.93 

Population Emission Factors—Gas Service 

Low Continuous Bleed Pneumatic Device Vents2 1.37 

High Continuous Bleed Pneumatic Device Vents2 18.20 

Intermittent Bleed Pneumatic Device Vents2 2.35 

1

 Valves include control valves, block valves and regulator valves. 

2 Emission Factor is in units of “scf/hour/device.” 

Table W-4 of Subpart W of Part 98—Default Total Hydrocarbon Emission Factors for 

Underground Natural Gas Storage 

Underground natural gas storage Emission factor (scf/hour/component) 

Leaker Emission Factors—Storage Station, Gas Service 

Valve1 14.84 

Connector 5.59 

Open-Ended Line 17.27 

Pressure Relief Valve 39.66 

Meter 19.33 

Population Emission Factors—Storage Wellheads, Gas Service 

Connector 0.01 

Valve 0.1 
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Underground natural gas storage Emission factor (scf/hour/component) 

Pressure Relief Valve 0.17 

Open Ended Line 0.03 

Population Emission Factors—Other Components, Gas Service 

Low Continuous Bleed Pneumatic Device Vents 2 1.37 

High Continuous Bleed Pneumatic Device Vents 2 18.20 

Intermittent Bleed Pneumatic Device Vents 2 2.35 

1 Valves include control valves, block valves and regulator valves. 

2 Emission Factor is in units of “scf/hour/device.” 

Table W-5 of Subpart W of Part 98—Default Methane Emission Factors for Liquefied 

Natural Gas (LNG) Storage 

LNG storage Emission factor (scf/hour/component) 

Leaker Emission Factors—LNG Storage Components, LNG Service 

Valve 1.19 

Pump Seal 4.00 

Connector 0.34 

Other 1 1.77 

Population Emission Factors—LNG Storage Compressor, Gas Service 

Vapor Recovery Compressor 2 4.17 

1 “Other” equipment type should be applied for any equipment type other than connectors, pumps, or valves. 

2 Emission Factor is in units of “scf/hour/device.” 

Table W-6 of Subpart W of Part 98—Default Methane Emission Factors for LNG Import 

and Export Equipment 

LNG import and export equipment Emission factor (scf/hour/component) 

Leaker Emission Factors—LNG Terminals Components, LNG Service 

Valve 1.19 

Pump Seal 4.00 

Connector 0.34 
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LNG import and export equipment Emission factor (scf/hour/component) 

Leaker Emission Factors—LNG Terminals Components, LNG Service 

Other 1 1.77 

Population Emission Factors—LNG Terminals Compressor, Gas Service 

Vapor Recovery Compressor2 4.17 

1 “Other” equipment type should be applied for any equipment type other than connectors, pumps, or valves. 

2 Emission Factors is in units of “scf/hour/compressor.” 

Table W-7 of Subpart W of Part 98—Default Methane Emission Factors for Natural Gas 

Distribution 

Natural gas distribution 

Emission factor (scf/hour/ 

component) 

Leaker Emission Factors—Transmission-Distribution Transfer Station1 Components, Gas Service 

Connector 1.69 

Block Valve 0.557 

Control Valve 9.34 

Pressure Relief Valve 0.27 

Orifice Meter 0.212 

Regulator 0.772 

Open-ended Line 26.131 

Population Emission Factors—Below Grade Metering-Regulating station1 Components, Gas Service2

Below Grade M&R Station, Inlet Pressure > 300 psig 1.30 

Below Grade M&R Station, Inlet Pressure 100 to 300 psig 0.20 

Below Grade M&R Station, Inlet Pressure < 100 psig 0.10 

Population Emission Factors—Distribution Mains, Gas Service3

Unprotected Steel 12.58 

Protected Steel 0.35 

Plastic 1.13 

Cast Iron 27.25 

Population Emission Factors—Distribution Services, Gas Service4
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Natural gas distribution 

Emission factor (scf/hour/ 

component) 

Unprotected Steel 0.19 

Protected Steel 0.02 

Plastic 0.001 

Copper 0.03 

1 Excluding customer meters. 

2 Emission Factor is in units of “scf/hour/station.” 

3 Emission Factor is in units of “scf/hour/mile.” 

4 Emission Factor is in units of “scf/hour/number of services.”