310 – Oil Production Sumps & Well Cellars 

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SumpsCellars2007_modified 06February09.doc Rev. By: G. Stewart

2007 Area Source Emissions Inventory Methodology 

310 – OIL PRODUCTION FUGITIVE LOSSES 

I. Purpose 

This document describes the Area Source Methodology used to estimate fugitive 

emissions of volatile organic compounds (VOCs) from oil sumps and well cellars in 

the San Joaquin Valley Air Basin. An area source category is a collection of similar 

emission units within a geographic area (i.e., a County). An area source category 

collectively represents individual sources that are small and numerous, and that may 

not have been inventoried as specific point, mobile, or biogenic sources. The 

California Air Resources Board (CARB) has grouped these individual sources with 

other like sources into area source categories. These source categories are grouped 

in such a way that they can be estimated collectively using one methodology. 

II. Applicability 

The emission calculations from this Area Source Methodology apply to facilities that 

are identified by the following Category of Emission Source (CES) codes and 

Reconciliation Emission Inventory Codes (REIC): 

Table 1. Emission inventory codes. 

CES REIC Description 

81950 310-300-1600-0000 Oil Production Fugitive Losses – Sumps and Pits 

82016 310-312-1600-0000 Oil Production Fugitive Losses – Well Cellars 

III. Point Source Reconciliation 

Emissions from the area source inventory and point source inventory are reconciled 

against each other to prevent double counting. This is done using relationships 

created by the California Air Resources Board (ARB) between the area source REIC 

and the point sources’ Standard Industry Classification (SIC) code and emissions 

process Source Category Code (SCC) combinations. The area sources in this 

methodology are not represented within our point source inventory; therefore, 

reconciliation is not necessary. 

San Joaquin Valley

AIR POLLUTION CONTROL DISTRICT
310 – Oil Production Sumps & Well Cellars 

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IV. Methodology Description 

SUMPS:

After petroleum is pumped from the ground, the crude oil must be separated from 

the water, sand and other fluids present. In most cases, this process occurs in tanks 

or a combination of tanks and sumps. A sump is defined as an excavated lined or 

unlined pit (excavated depression) in the ground that is used to separate oil, water, 

and sand from oil production operations. For the purpose of estimating emissions, 

sumps can be separated into the following three classes based upon the stage 

within the treatment process: 

• First stage (primary) production sump: A sump that receives a stream of 

crude oil and produced water directly from one or more oil production wells or 

field gathering systems. 

• Second stage (secondary) production sump: A sump that receives waste 

water streams (water/oil) from one or more first stage separators (including 

first stage sumps and/or tanks). 

• Third stage (tertiary) production sump: A sump that receives waste water 

streams (water/oil) from one or more second stage separators (including 

second stage sumps and/or tanks). In most cases, there are only small 

amounts of oil present in the waste streams. 

Sumps are also classified based upon the type of petroleum they receive: 

• Light oil service sumps: Sumps which contain crude oil having an American 

Petroleum Institute’s (API) gravity of 30o or greater. 

• Heavy oil service sumps: Sumps which contain crude oil having an API 

gravity less than 30o. 

WELL CELLARS: 

A well cellar is a lined or unlined containment surrounding one or more wellheads, 

allowing access to the wellhead components for servicing and/or installation of 

blowout prevention equipment. A well cellar is designed to catch any liquid that may 

leak or spill from wellhead maintenance operations or faulty well equipment. As with 

sumps, well cellars are also classified based upon the type of petroleum they 

receive. 

This methodology estimates fugitive emissions of VOCs from sumps and well 

cellars. For this emissions inventory, the District surveyed the oil and gas production 

industry to determine the total surface area of first, second and third stage heavy 

and light oil sumps; as well as, the total surface area of heavy and light oil well 

cellars in the District. The total surface area of each sump and well cellar was then 

multiplied by an emission factor to estimate VOC emissions. 
310 – Oil Production Sumps & Well Cellars 

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V. Activity Data 

Oil production facilities within the District were surveyed to determine the number 

and surface area of active sumps and well cellars. A copy of the survey form is 

included in Appendix A. Industry response to the survey is presented in the 

following table: 

Table 2. Oil production facility response to the 

District’s sump and well cellar survey (2007). 

Surveys 

Facility Type Mailed 

(no.) 

Returned 

(no.) 

Returned 

(%) 

Large Operations1 39 37 94.9 

Small Operations 228 173 75.9 

TOTAL 267 210 78.7 

1

Large Operations: Operations subject to District Rule 2520 

(Federally Mandated Operating Permits)

The number of active sumps and well cellars by facility size and oil specific gravity 

are presented in the following table: 

Table 3. Survey results of the number of sumps and well cellars in the District 

by facility size and oil specific gravity (2007). 

Classification 

First Stage 

Sumps 

(no.) 

Second Stage 

Sumps 

(no.) 

Third State 

Sumps 

(no.) 

Well Cellars 

(no.) 

Large Operations 

 Light Oil 0 0 0 1,907 

 Heavy Oil 0 0 1 2,643 

Small Operations 

 Light Oil 0 6 10 972 

 Heavy Oil 0 34 44 1,275 

TOTAL 

 Light Oil 0 6 10 2,879 

 Heavy Oil 0 34 45 3,918 
310 – Oil Production Sumps & Well Cellars 

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The surface area of active sumps and well cellars by facility size and oil specific 

gravity are presented in the following table: 

Table 4. Survey results of the surface area of sumps and well cellars in the 

District by facility size and oil specific gravity (2007). 

Classification 

First Stage 

Sumps 

(ft2) 

Second Stage 

Sumps 

(ft2) 

Third Stage 

Sumps 

(ft2) 

Well 

Cellars 

(ft2) 

Large Operations 

 Light Oil 0 0 0 113,761 

 Heavy Oil 0 0 4,800 135,281 

Small Operations 

 Light Oil 0 4,266 35,206 61,254 

 Heavy Oil 0 68,372 103,829 38,763 

TOTAL 0 

 Light Oil 0 4,266 35,206 175,015 

 Heavy Oil 0 68,372 108,629 174,044 

The average facility sump and well cellar surface area was then calculated for large 

and small, heavy and light oil operations. 

For example: average surface area of large operations heavy oil third stage sumps 

Ave surface area 3° sumps ft2 = ∑ surface area 3° sumps ft2 ÷ ∑ facilities reporting 3° sumps 

 

Table 5. Facility average surface area of sumps and well cellars in the District 

by facility size and oil specific gravity (2007). 

Classification 

First Stage 

Sumps 

(ft2) 

Second Stage 

Sumps 

(ft2) 

Third Stage 

Sumps 

(ft2) 

Well 

Cellars 

(ft2) 

Large Operations 

 Light Oil 0 0 0 8,125.81 

 Heavy Oil 0 0 320.0 9,018.75 

Small Operations 

 Light Oil 0 101.57 838.24 1,458.42 

 Heavy Oil 0 876.56 1,331.14 496.96 

Sump and well cellar surface area was then adjusted to account for facilities that did 

not respond to the survey. For facilities that did not respond to the survey, an 

average value (see Table 5) was assumed based on the non-responding facility’s 

size and oil specific gravity (Large: 2 heavy oil; Small: 33 heavy and 20 light oil). 
310 – Oil Production Sumps & Well Cellars 

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Table 6. Adjusted surface area of sumps and well cellars in the District by 

facility size and oil specific gravity. Results adjusted to account for 

facilities that did not respond to the survey (2007). 

Classification 

First Stage 

Sumps 

(ft2) 

Second Stage 

Sumps 

(ft2) 

Third Stage 

Sumps 

(ft2) 

Well 

Cellars 

(ft2) 

Large Operations 

 Light Oil 0 0 0 113,761 

 Heavy Oil 0 0 5,440 153,319 

Small Operations 

 Light Oil 0 6,297 51,971 77,654 

 Heavy Oil 0 97,298 147,757 55,163 

TOTAL 

 Light Oil 0 6,297 51,971 191,415 

 Heavy Oil 0 97,298 153,197 208,481 

VI. Emission Factors 

Emission factors for crude oil production sumps and cellars are from a correction 

made to the Technical Guidance Document for the Emission Inventory Criteria and 

Guidelines Regulation for AB 2588 (Air Toxics “Hot Spots” Information and 

Assessment Act of 1987) by the Kern County Air Pollution Control District (see the 

memo presented in Appendix B) These emission factors are summarized in the 

following table: 

Table 7. Uncontrolled emission factors for oil sumps. 

Sump 

Classification 

Total Organic Gas 

(lb/ft2-day) 

Fractional Reactive 

Organic Gas* 

Reactive Organic 

Gas 

(lb/ft2-day) 

Heavy Oil (API <30°) 

First Stage 0.10459 0.80 0.0837 

Second Stage 0.05149 0.80 0.0412 

Third Stage 0.00641 0.80 0.0051 

Light Oil (API > 30°) 

First Stage 0.143 0.80 0.1144 

Second Stage 0.02 0.80 0.016 

Third Stage 0.01 0.80 0.008 

* See Appendix B: “Revised Technical Guidance Document” (ROG = 80% of TOG) 

The emission factors for first stage sumps were used for well cellars. 
310 – Oil Production Sumps & Well Cellars 

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VII. Emissions Calculations 

A. Assumptions

1. “Active” sumps are first, second, and third stage sumps used exclusively 

for the separation of crude petroleum from water produced during 

production. 

2. Total sump and well cellar area and classification (heavy/light oil, 

first/second/third stage sumps) as reported through the District’s survey 

are accurate. 

3. Emissions from active sumps are uncontrolled. 

4. The method used to account for facilities that did not respond to the 

District’s survey accurately represents their sump and well cellar area. 

5. Second and third stage sumps contain fluid 365 days per year. 

6. The emission factors for oil sumps are independent of temperature, and 

emissions activity is assumed to be uniform throughout the year. 

7. Well cellars receive fluid 1 day per year (letter from Chevron dated 

October 17, 2000). 

B. Sample Calculations

VOC emissions from light oil sumps in Kern County:

Step 1. Multiply the total area (ft2) of each stage sump by the appropriate 

emission factor for light oil (API > 30o) times 365 days/year. 

year

days First stage sump area ft x x365

ft day

0.0837 lbs VOC VOC ( )

2

2

First -stage sumps, lbs

−

= ∑ −

year

days

x x

365

ft day

0.0412 lbs VOC VOC Second stage sump area (ft )

2

2

Second -stage sumps, lbs

−

= ∑

year

days

x

365

ft day

0.0051 lbs VOC VOC Third stage sump area (ft )

2

2

Third -stage sumps, lbs ×

−

= ∑

Example: 

year

lbs VOC

year

days ft x x365 0

ft day

0.0837 lbs VOC VOC 0 2

2

First -stage sumps, lbs =

−

=
310 – Oil Production Sumps & Well Cellars 

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year

lbs VOC

year

days ft x x365 34 ,999

ft day

0.016 lbs VOC VOC ,5 993 2

2

Second -stage sumps, lbs =

−

=

year

lbs VOC

year

days ft x x365 111 ,562

ft day

0.008 lbs VOC VOC 38 ,206 2

2

Third -stage sumps, lbs =

−

=

Step 2. Add the annual VOC emissions for each sump stage and multiply by 1 

ton over 2,000 lbs to obtain the annual VOC emissions in tons of VOC per year. 

[ ]

,2000lbs

1ton VOCSumptotal,tons = lbsVOCFirst-stagesumps + lbsVOCSecond-stagesumps + lbsVOCThird-stagesumps

*

Example: 

year

tonsVOC

lbs

ton

year

VOCSump total tons

73 28.

,2 000

1

*

111,562lbs VOC

year

34,999lbs VOC

year

0 lbs VOC

, = 











= + +

VIII. Temporal Variation 

We assume sump emissions are independent of temperature, and emissions activity 

is uniform throughout the year. 

 A. Daily

 CARB Code 24. 24 hours per day - uniform activity during the day. 

 B. Weekly

 CARB Code 7. 7 days per week - uniform activity every day of the week 

 C. Monthly

 Uniform monthly activity. 8.33% per month 

We assume well cellars receive fluid one day per year. 

IX. Spatial Variation 

Oil production facilities are located in the Central and Southern Regions of the 

District, with the heaviest concentration in Kern County. 
310 – Oil Production Sumps & Well Cellars 

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X. Growth Factor 

Growth factors are developed by either the District’s Planning Department or CARB 

for each EIC. These factors are used to estimate emissions in future years. The 

growth factors associated with this emissions category may be obtained from the Air 

Quality Analysis Section of the District’s Planning Department. 

XI. Control Level 

Control levels are developed by either the District’s Planning Department or CARB 

for each EIC. Control levels are used to estimate emissions reductions in future 

years due to implementation of District rules. These control levels take into account 

the effect of control technology, compliance and exemptions at full implementation of 

the rules. 

Oil sumps are subject to District Rule 4402 (Crude Oil Production Sumps). Control 

levels associated with this emissions category may be obtained from the Air Quality 

Analysis Section of the District’s Planning Department. 

XII. ARB Chemical Speciation 

CARB has developed organic gas profiles in order to calculate reactive organic 

gasses (ROG), volatile organic compounds (VOC) or total organic gas (TOG) given 

any one of the three values. For each speciation profile, the fraction of TOG that is 

ROG and VOC is given. The organic gas profile codes can also be used to lookup 

associated toxics. CARB’s speciation profiles for fugitive emissions from oil sumps 

and well cellars is presented in Table 8. 

XIII. Assessment Of Methodology 

The accuracy of this estimate is dependent upon data provided to the District by the 

oil production industry (SIC 1311) through our survey. Our estimate excludes any 

pits, ponds or sumps not used for separating crude oil such as those used to for 

clean produced water; the EPA’s Spill Prevention, Control, and Countermeasure 

Rule (SPCC); inactive units, etc. 

Table 8. CARB organic gas speciation profiles for oil sumps (profile 537) and well 

cellars (profile 532). 

Fractions Profile Description CARB Organic 

Gas Profile# ROG VOC 

Crude Oil – Sumps, Wells, HOTS, Kern Co 537 0.912* 0.912* 

Oil & Gas Extraction – Well Heads & 

Cellars/Oil & Water Separators 532 0.606 0.606 

*These values differ from what the District uses. See Revised Technical Guidance document 

(ROG = 80% of TOG)
310 – Oil Production Sumps & Well Cellars 

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When ARB calculated oil sump emissions in 1993, they used an emission factor 

(EF) of 0.0515 lbs ROG/ft2

-day for second stage heavy oil sumps. In this 

methodology, the District uses an emission factor of 0.0412 lbs ROG/ft2-day for 

second stage heavy oil sumps. This emission factor represents a 3.6 fold decrease 

in lbs ROG/ft2-day compared to the one used in the previous estimate. The impact 

of this change is demonstrated below for Kern County’s 78,798 ft2 of second stage 

heavy oil sumps: 

year

tons

lbs

ton

x

year

days

x

ft day

lbs VOC

x

year

ft ARB EF 742 29.

,2 000

78,798 .0 0515 365 1

2

2

=

−

=

year

tons

lbs

ton

x

year

days

x

ft day

lbs VOC

x

year

ft District EF 593 84.

,2 000

78,978 .0 0412 365 1

2

2

=

−

=

As demonstrated above, this change results in an decrease of 148 tons per year of 

VOC in Kern County due to the use of the new emission factor for second stage 

heavy oil sumps. 

XIV. Emissions 

Since oil sumps and well cellars are not represented in the Districts point source 

inventory, the total unreconciled emissions are equal to the area source emissions. 

Following is the 2007 total unreconciled (point source plus area source) emissions 

inventory for oil sumps and well cellars. Emissions are reported for each county in 

the District. 

Table 9. Total emissions for oil sumps and well cellars (2007). 

Emissions (tons/year) County NOx CO SOx VOC(1)

 PM10 PM2.5

(2)

Oil Production Fugitive losses – Sumps and Pits (310-300-1600-0000) 

 Fresno N/A N/A N/A 9.75 N/A N/A 

 Kern N/A N/A N/A 761.35 N/A N/A 

 Kings N/A N/A N/A 0.00 N/A N/A 

 Madera N/A N/A N/A 0.00 N/A N/A 

 Merced N/A N/A N/A 0.00 N/A N/A 

 San Joaquin N/A N/A N/A 0.00 N/A N/A 

 Stanislaus N/A N/A N/A 0.00 N/A N/A 

 Tulare N/A N/A N/A 197.34 N/A N/A 

 TOTAL N/A N/A N/A 968.44 N/A N/A 

Oil Production Fugitive losses – Well Cellars (310-312-1600-0000) 

 Fresno N/A N/A N/A 1.11 N/A N/A 

 Kern N/A N/A N/A 19.01 N/A N/A 

 Kings N/A N/A N/A 0.12 N/A N/A 

 Madera N/A N/A N/A 0.00 N/A N/A 

 Merced N/A N/A N/A 0.00 N/A N/A 

 San Joaquin N/A N/A N/A 0.00 N/A N/A 

 Stanislaus N/A N/A N/A 0.00 N/A N/A 

 Tulare N/A N/A N/A 0.17 N/A N/A 

 TOTAL N/A N/A N/A 20.41 N/A N/A 
310 – Oil Production Sumps & Well Cellars 

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(1) The District only reports ROG to CARB. As noted in Section XII, ROG is the 

same as VOC. 
310 – Oil Production Sumps & Well Cellars 

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Following is the net change in total unreconciled emissions between this update 

(2007 inventory year) and CEIDARS data for the previous year (2006 inventory year) 

for oil sumps and well cellars. The changes in emissions are reported for each 

county in the District. 

Table 10. Net emissions change for oil sumps and well cellars (2007). 

Emissions (tons/year) County NOx CO SOx VOC(1)

 PM10 PM2.5

(2)

Oil Production Fugitive losses – Sumps and Pits (310-300-1600-0000) 

 Fresno N/A N/A N/A -9.13 N/A N/A 

 Kern N/A N/A N/A 645.17 N/A N/A 

 Kings N/A N/A N/A -20.16 N/A N/A 

 Madera N/A N/A N/A 0 N/A N/A 

 Merced N/A N/A N/A 0 N/A N/A 

 San Joaquin N/A N/A N/A 0 N/A N/A 

 Stanislaus N/A N/A N/A 0 N/A N/A 

 Tulare N/A N/A N/A 197.34 N/A N/A 

 TOTAL N/A N/A N/A 813.22 N/A N/A 

Oil Production Fugitive losses – Well Cellars (310-312-1600-0000) 

 Fresno N/A N/A N/A -0.73 N/A N/A 

 Kern N/A N/A N/A -23.42 N/A N/A 

 Kings N/A N/A N/A 0.04 N/A N/A 

 Madera N/A N/A N/A 0 N/A N/A 

 Merced N/A N/A N/A 0 N/A N/A 

 San Joaquin N/A N/A N/A 0 N/A N/A 

 Stanislaus N/A N/A N/A 0 N/A N/A 

 Tulare N/A N/A N/A 0.11 N/A N/A 

 TOTAL N/A N/A N/A -24.04 N/A N/A 

(1) The District only reports ROG to CARB. As noted in Section XII, ROG is the 

same as VOC. 

XV. Revision History 

2007. This is a new District methodology based on a survey of oil producers. 

XVI. Update Schedule 

The area source categories within this methodology have update authority “B” 

codes. This means that ARB develops default emissions for these sources, but 

Districts may overwrite them subject to ARB review and approval. Since the District 

is not directly responsible for maintaining these area source categories, they will only 

be updated as needed. 
310 – Oil Production Sumps & Well Cellars 

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XVII. References 

1. Kern County Air Pollution Control District. 1990. Corrections to CARB’s AB 

2588 Air “Hot Spots” technical guidance document, Table D-1, Page 118. 

2. California Air Resources Board. 2004. Definitions of VOC and ROG 

http://www.arb.ca.gov/ei/speciate/definitions.htm 

3. California Air Resources Board Technical Review Group. 1988. Technical 

support document for suggested control measure for the control of organic 

compound emissions from sumps used in oil production operations. 

4. Clark, L. 2007. Independent Oil Producers Agency. Personal Communication 

via e-mail and visit. 

5. Eaton, W.S. 1980. Fugitive hydrocarbon emissions from petroleum production 

operations. 

6. Funk, T.H. 2003. Emission inventory methodology – Oil and gas sumps. 

Somona Technology, Inc., Petaluma, CA. 

7. Gunderson, D. 2007. Aera Energy. Personal Communication via e-mail. 

8. San Joaquin Valley Air Pollution Control District. 2000. Rule 4441 (Draft): Well 

cellars and sumps. 

9. San Joaquin Valley Air Pollution Control District. 1991. Rule 4402: Crude oil 

production sumps. http://www.valleyair.org/rules/currntrules/r4401.pdf 

10. United States Environmental Protection Agency. 1993. Supplement D to 

Compilation of Emission Factors (AP-42), U.S. GPO, Washington D.C., 1993. 

http://www.epa.gov/ttn/chief/ap42/ 

XVIII. Appendices 

Appendix A. District Sump and Well Cellar Survey 

Appendix B. Memo from Kern Co. APCD: Revised Technical Guidance Document 
310 – Oil Production Sumps & Well Cellars 

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Appendix A. District Sump and Well Cellar Survey 

Active Sump and Well Cellar Data 

For Calendar Year 2007

Please complete this Emissions Inventory survey and return to any of the District offices. The data will 

be used to improve the District’s area-wide emission inventory. This information is vital to ensure that 

future air pollution control plans and rules reflect actual emissions and do not overestimate your 

industry’s emissions. Thank you for your assistance. If you have any questions please call Maya 

Hildebrand-Garcia at (559) 230-5934. 

The questions below refer only to active sumps used as first, second, and third-stage production sumps. It 

does not refer to sumps used to for clean produced water, the EPA’s (Spill Prevention, Control, and 

Countermeasure Rule (SPCC), evaporation, precipitation, percolation, or any pits and ponds not used for 

separating crude oil. 

1. Light Crude Oil (>30o API Gravity) 

Production Sumps Total number Total area (square feet) 

First Stage 

Second Stage 

Third Stage 

Well cellars 

2. Heavy Crude Oil (<30o API Gravity) 

Production Sumps Total number Total area (square feet) 

First Stage 

Second Stage 

Third Stage 

Well cellars 

3. Comments: 

4. Contact Information 

Facility name: _____________________________________________________________ 

Contact person: ____________________________________________________________ 

Address: _________________________________________________________________ 

Telephone:_______________FAX: ________________E-mail ______________________ 
310 – Oil Production Sumps & Well Cellars 

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Appendix B. Revised Technical Guidance Document 
310 – Oil Production Sumps & Well Cellars 

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