1 Kelly, Shaheerah

From: Stewart, Kathleen

Sent: Tuesday, October 07, 2014 7:56 AM

To: Stewart, Kathleen Subject: Fw: McElmo flare concern?
Attachments: McElmo_SCREEN.zi

**************************************************** Children's Environmental Health and Schools Team, EPA Region 9 75 Hawthorne St (CED-4) San Francisco, CA 94105

Phone (415) 947-4119 Fax: 947-3583

I work a part-time schedule. I am available Tuesday s and Thursdays, from 6:30AM-3:00PM, and Wednesdays from 8:30-12:30. Should you need assistance at other ti mes, you can contact Jacquelyn Hayes at (415) 972- 3259.

----- Forwarded by Kathleen Stewart/R9/USEPA/US on 10/07/2014 07:56 AM -----

From: Kathleen Stewart/R9/USEPA/US To: Scott Bohning/R9/USEPA/US@EPA, Date: 04/28/2006 08:42 AM Subject: Re: McElmo flare concern?

Scott - did you ever hear back from these guys?

************************************* Katie Stewart Environmental Scientist Air Division, Permits Office 75 Hawthorne Street US EPA, Region 9 San Francisco, CA 94105-3901 (415) 947-4119 (415) 947-3579 fax

Scott Bohning/R9/USEPA/US

Scott Bohning/R9/USEPA/US

04/06/2006 03:09 PM To "John Bunyak" <John_Bunyak@nps.gov>, John_Notar@nps.gov

cc Kathleen Stewart/R9/USEPA/US@EPA

Subject McElmo flare concern?

John & John -

I hope you're both doing well -- I'll probably s ee you in Denver last week of April.

ExxonMobil has to do a PSD permit for McElmo Main Flare as par t of a consent decree. This source is probably too small2 to be of interest to you, but they shoul d have contacted you anyway. Please let us know if you have a concern over this source, or if they could be excused from AQRV analysis.

It's in Utah, SW corner. Long & Lat is: -109.2038, 37.26

Their worst-case emission estimates for this flare: SO 2 320.00 tons/yr; CO 659.1 tons/yr; NOx 76.8 tons/yr

According to their SCREEN3 modeling, maximum impacts ar e about 1 km away, and are below the Class II significance levels, and way below NAAQS.

The nearest Class I areas are Canyonlands NP (UT) and Mesa Verde NP (CO), and are within 100 km (but more than 50 km). I did quick rerun of SCREEN3 for 40-50 km, and source is below Class I significance levels.

Source contact info: "Neil Ryan" <neil.j.ryan@exxonmobil.com> US Production OIMS - ER Supervisor 281/654-1042

Thanks...

- Scott B.

P.S. Katie - sorry for the delay, I meant to get this out Monday a.m.

=+=+=+=+=+=+=+=+=+=+=+=+=+=+= Scott Bohning U.S. EPA Region 9, AIR-7 bohning.scott@epa.gov 415/947-4127 fax-3579

Attached ZIP file contains: - Model Input Data and Summary Results_3- 28-05.doc - ExxonMobil's SCREEN3 results - mcelmo_c1.gif - my location map showing source and Class I areas - ME300.dat, me300.out , ME443.dat, ME443.out - my SCREEN 3 input & output for 300 and 443 BTU/scf heat content scenarios - McElmo_SCREEN3_SCALE.XLS - my SCREEN3 results sc aled to emission rates, comparison to sig levels

(Note: Attachments with names ending in ".zi" are ZIP archives; to use, detach and rename to have ".zip" ending. EPA e-mail administrators strip .zip files from all outgoing and incoming e-mail, on the grounds that several years ago there was a flurry of viruses/worms contained in e- mailed .zip files, e.g. MyDoom.) (See attached file: McElmo_SCREEN.zi)McElmo Main Flare Model and Assumptions

- 1 - McElmo Main Flare Dispersion Model Results and Assumptions

Project

In order to comply with Section V, Para graph 14a of the 2005 Consent Decree between Mobil Exploration and Producing U.S. Inc. a nd the United States Environmental Protection Agency (EPA) an air quality analysis was perf ormed in accordance with the requirements of 40 C.F.R. §52.21. The purpose of this documen t is to summarize the assumptions and processes utilized to complete the air quality analysis.

A preliminary analysis was performed using the SCREEN3 dispersion modeling program.
This model was used to run the emissions a ssociated with the McElmo Main Flare, to
evaluate NO x , CO, and SO 2 . The following section pertai ns to the input data and assumptions used to model the emissions using SCREEN3.

Model Input Data

The dispersion modeling program was run base d on two different lo wer heating values (LHV) of the gas being burned at the McElmo Main Flare. The lowest value input into SCREEN3 was 300 BTU/scf, which is the lowe st allowable LHV as stated in 40 CFR 60.18(c)(3)(ii). The higher value utilized was 44 3 BTU/scf, which is th e lowest of the four most recent actual plant gas samples from Mc Elmo. The four analyses are dated 4/28/04, 5/27/04, 8/29/04, and 9/29/04; and their LHV values in BTU/scf were 443, 505, 512, and 453, respectively. The 443 BTU/scf LHV was ut ilized due to the assumption that it would provide the least amount of heat rise, thus producing the lowest effective release height.

The maximum flare rate utilized was 689,423 acf /hr (618,104 scf/hr), which assumes that the flare is operating at 14.83 MCFD for the entire year. The flare rate value of 618,104 scf/hr was based on the assumption that the new flare tip will be 24 inches in diameter and will have a flare tip exit ve locity of 64.74 ft/s. This exit ve locity is below the maximum exit velocity as specified by 40 CFR 60.18, which is 66.98 ft/s.

The heat released from the flare tip was then ca lculated and converted to a rate of calories per
second based on the conversion of 1 BTU = 252. 1644 calories. The equation used for this
calculation is as follows:

s cal V LHV

s cal heat 3600 ) 1644

. 252 )( )( ( ) / ( 

Where: LHV = lower heating va lue of gas burned (BTU/scf) V = 618,104 scf/hr.

The actual flare stack height of 195 feet wa s taken from drawing D-SA-107 as provided by Zeeco, Inc. from 1991. This measurement was fi eld verified to ensure proper stack height.

The emission factors for NO x and CO were derived by the Chemical Section of the Texas Commission on Environmental Quality NSR Di vision based on data published in the 1983McElmo Main Flare Model and Assumptions

- 2 - Chemical Manufacturer's Association document entitled "A Report On A Flare Efficiency Study." The factors used were as follows:

NO x = 0.0641 lb/MMBTU
CO = 0.5496 lb/MMBTU.

Therefore, the equation used to calculate the emission rate for NO x and CO contaminants at the specified LHV is as follows:

s hr

lb g
MMBTU lb EF BTU MMBTU scf BTU LHV hr scf V s g rate 3600 * 59

. 453 * * 10 * * ) / (
6 

Where: V = 618,104 scf/hr LHV = lower heating value of gas burned (BTU/scf) EF = emission factor (lb/MMBTU).

Recent tests at the McElmo site indicate the plant inlet gas contains approximately 450 ppm
H 2 S. However, it was assumed that the flared gas contains 700 ppm H 2 S on the SCREEN3
SO 2 dispersion model. This H 2 S value was used in order to pr ovide a conservative estimate
of SO 2 emissions from the flare. The emi ssion rate was calculated as follows:

hr lbSO MMparts mol scf molSO lb ppm hr scf rate / 2 06

. 73 1 / 379 2 / 64 700 / 104

, 618

   



Model Runs

Once all assumption and data was obtained, the SCREEN3 model was run for each
contaminant at the LHV of 300 BTU/scf and 443 BTU/scf. The model was run using the full meteorology scenario and was set to provide co ntaminant concentrations at ground level. The model results are based on the simple terr ain inputs as detailed in the assumptions and utilizing the rural option based on the area of the flare location.McElmo Main Flare Model and Assumptions

- 3 - Results

The results provided by SCREEN3 are based on 1-hour averaging period concentrations.
The one hour estimates were converted to l onger averaging periods utilizing the following EPA factors: 0.9 (3-hr); 0.7 (8-hr); 0.4 ( 24-hr); and 0.08 (Annual) . The results are summarized in Tables 1 & 2 below. The equa tion used for converting to longer averaging periods is as follows:

C F m g ion concentrat * ) / ( 3

 

Where:
F = EPA conversion factor C = 1-hour averaging period concentration (  g/m 3 ).

Table 1: Maximum Contaminan t Concentrations at 300 BTU Pollutant Averaging
Period Max. Modeling Concentration @ 1097 meters (  g/m 3 ) PSD Modeling Significance Levels (  g/m 3 ) NAAQS (  g/m 3 )

NO x Annual 0.15 1 100 CO 8-hour 11.35 500 10,000

1-hour 16.21 2,000 40,000
SO 2 Annual 0.93 1 80

24-hour 4.65 5 365
3-hour 10.47 25 1300

Table 2: Maximum Contaminan t Concentrations at 443 BTU Pollutant Averaging
Period Max. Modeling Concentration @ 1075 meters (  g/m 3 ) PSD Modeling Significance Levels (  g/m 3 ) NAAQS (  g/m 3 )

NO x Annual 0.17 1 100 CO 8-hour 12.90 500 10,000

1-hour 18.43 2,000 40,000
SO 2 Annual 0.72 1 80

24-hour 3.58 5 365
3-hour 8.06 25 1300McElmo Main Flare Model and Assumptions

- 4 - Summary

In order to prepare a conservative model for the prediction of emissions from the McElmo Main Flare several assumptions were made. Ma ny of these assumptions were made with the intent of providing conserva tive estimates including: 1. The lowest heat value rating for the ga s at McElmo to lower the effective release height of the emissions produced by the McElmo Main Flare. 2. The maximum design flare rate of 14.83 MCFD.
3. The H 2 S concentration of 700 ppm instead of the actual measured value of approximately 450 ppm.

Emission limitations established by the Consent Decree for the McElmo Main Flare are 60 tons per year of SO 2 , 73 tons per year of CO, 13.4 tons per year of NO x , and 94.5 tons per year of VOC. The worst-case conditions ba sed on this maximum flare rate of 14.83 MCFD
and a LHV of 443 BTU/scf result in emi ssions of 320.00 tons per year of SO 2 , 659.1 tons per year of CO, and 76.8 tons per year of NO x . With these worst-case estimates as mentioned above, the modeling results do not meet the NAAQS concentrations as can be seen above in Tables 1 & 2. These very conservative assu mptions model release conditions over five times greater than current air permit lim its. In addition, the actual field conditions are not capable of sustaining a flow rate of 14.83 MCFD.McElmo Flare - comparison of distant impact to Class I significance levelsScaling of 1 g/s SCREEN3 run, automated distances 40 km - 50 kmSCREEN3 averaging time conversionsimple terrain complex terrainmulitply 1-hr by: mulitply 24-hr by:averaging timconversion fauncerainty averaging timconversion factor110 143 0.9 0.1 3 46 0.76 0.2 6 48 0.7 0.2 8 324 0.4 0.2 24 18760 0.08 0.02 8760 0.32SCREEN3 maxin 40-50 km0.2782 Class I Class IIpollutant avg.time conv. factor emission rateprediction sig. level sig. level NAAQS300 BTU SO2 700ppm3 0.9 9.21 8.5672 ok 25 512 1300SO2 700ppm24 0.4 9.21 3.9622 ok 5 91 365SO2 700ppm8760 0.08 9.21 1.015 ok 2 20 80SO2 3 0.9 10.52 9.7462 ok 25 512 1300SO2 24 0.4 10.52 4.4862 ok 5 91 365SO2 8760 0.08 10.52 1.1198 ok 2 20 80NOx 8760 0.08 1.5 0.3982 ok 2.5 25 100CO 1 1 12.84 13.1182 40000CO 8 0.7 12.84 9.2662 10000SCREEN3 maxin 40-50 km0.2243pollutant avg.time conv. factor emission rateprediction443 BTU SO2 700ppm3 0.9 9.21 8.5133 ok 25 512 1300SO2 700ppm24 0.4 9.21 3.9083 ok 5 91 365SO2 700ppm8760 0.08 9.21 0.9611 ok 2 20 80SO2 3 0.9 10.52 9.6923 ok 25 512 1300SO2 24 0.4 10.52 4.4323 ok 5 91 365SO2 8760 0.08 10.52 1.0659 ok 2 20 80NOx 8760 0.08 2.21 0.4011 ok 2.5 25 100CO 1 1 18.96 19.1843 40000CO 8 0.7 18.96 13.4963 10000ME300 McElmo Flare 300 BTU f 10.0 Source type F=flare 1.000 emission rate (g/s) 59.45 flare stack height (m) .129887E+08 heat release rate (cal/s) .0000 flagpole receptor height (m) r Urban/Rural option (If u, delete fumigation block.) n Consider building downwash? n Complex terrain heights? n *Simple terrain heights? (If no, delete lines with *) 1 Meteorology: 1=full, 2=enter P-G class, 3=enter P-G & u y Automated distance array? 40000, 60000 {minimum, maximum receptor distances n Discrete receptors? n Fumigation calculation? (If urban, delete block.) n Hardcopy?

Page 1me300.out 04/06/06 14:22:47 *** SCREEN3 MODEL RUN *** *** VERSION DATED 96043 ***

McElmo Flare 300 BTU

SIMPLE TERRAIN INPUTS: SOURCE TYPE = FLARE EMISSION RATE (G/S) = 1.00000 FLARE STACK HEIGHT (M) = 59.4500 TOT HEAT RLS (CAL/S) = .129887E+08 RECEPTOR HEIGHT (M) = .0000 URBAN/RURAL OPTION = RURAL EFF RELEASE HEIGHT (M) = 70.9117 BUILDING HEIGHT (M) = .0000 MIN HORIZ BLDG DIM (M) = .0000 MAX HORIZ BLDG DIM (M) = .0000

THE REGULATORY (DEFAULT) MIXING HEIGHT OPTION WAS SELECTED. THE REGULATORY (DEFAULT) ANEMOMETER HEIGHT OF 10.0 METERS WAS ENTERED.

BUOY. FLUX = 215.357 M**4/S**3; MOM. FLUX = 131.320 M**4/S**2.

*** FULL METEOROLOGY ***

********************************** *** SCREEN AUTOMATED DISTANCES *** **********************************

*** TERRAIN HEIGHT OF 0. M ABOVE STACK BASE USED FOR FOLLOWING DISTANCES ***

DIST CONC U10M USTK MIX HT PLUME SIGMA SIGMA (M) (UG/M**3) STAB (M/S) (M/S) (M) HT (M) Y (M) Z (M) DWASH

------- ---------- ---- ----- ----- ------ ------ ------ ------ ----- 40000. .2782 5 1.0 2.0 10000.0 212.67 1382.31 147.53 NO 50000. .2430 5 1.0 2.0 10000.0 212.67 1678.21 156.86 NO

MAXIMUM 1-HR CONCENTRATION AT OR BEYOND 40000. M: 40000. .2782 5 1.0 2.0 10000.0 212.67 1382.31 147.53 NO

DWASH= MEANS NO CALC MADE (CONC = 0.0) DWASH=NO MEANS NO BUILDING DOWNWASH USED DWASH=HS MEANS HUBER-SNYDER DOWNWASH USED DWASH=SS MEANS SCHULMAN-SCIRE DOWNWASH USED DWASH=NA MEANS DOWNWASH NOT APPLICABLE, X<3*LB

*************************************** *** SUMMARY OF SCREEN MODEL RESULTS *** ***************************************

CALCULATION MAX CONC DIST TO TERRAIN PROCEDURE (UG/M**3) MAX (M) HT (M)

-------------- ----------- ------- ------- SIMPLE TERRAIN .2782 40000. 0.

*************************************************** ** REMEMBER TO INCLUDE BACKGROUND CONCENTRATIONS ** ***************************************************

Page 1ME443 McElmo Flare 443 BTU f 10.0 Source type F=flare 1.000 emission rate (g/s) 59.45 flare stack height (m) .191799E+08 heat release rate (cal/s) .0000 flagpole receptor height (m) r Urban/Rural option (If u, delete fumigation block.) n Consider building downwash? n Complex terrain heights? n *Simple terrain heights? (If no, delete lines with *) 1 Meteorology: 1=full, 2=enter P-G class, 3=enter P-G & u y Automated distance array? 40000, 60000 {minimum, maximum receptor distances n Discrete receptors? n Fumigation calculation? (If urban, delete block.) n Hardcopy?

Page 1ME443.out 04/06/06 14:28:18 *** SCREEN3 MODEL RUN *** *** VERSION DATED 96043 ***

McElmo Flare 443 BTU

SIMPLE TERRAIN INPUTS: SOURCE TYPE = FLARE EMISSION RATE (G/S) = 1.00000 FLARE STACK HEIGHT (M) = 59.4500 TOT HEAT RLS (CAL/S) = .191799E+08 RECEPTOR HEIGHT (M) = .0000 URBAN/RURAL OPTION = RURAL EFF RELEASE HEIGHT (M) = 73.2591 BUILDING HEIGHT (M) = .0000 MIN HORIZ BLDG DIM (M) = .0000 MAX HORIZ BLDG DIM (M) = .0000

THE REGULATORY (DEFAULT) MIXING HEIGHT OPTION WAS SELECTED. THE REGULATORY (DEFAULT) ANEMOMETER HEIGHT OF 10.0 METERS WAS ENTERED.

BUOY. FLUX = 318.009 M**4/S**3; MOM. FLUX = 193.915 M**4/S**2.

*** FULL METEOROLOGY ***

********************************** *** SCREEN AUTOMATED DISTANCES *** **********************************

*** TERRAIN HEIGHT OF 0. M ABOVE STACK BASE USED FOR FOLLOWING DISTANCES ***

DIST CONC U10M USTK MIX HT PLUME SIGMA SIGMA (M) (UG/M**3) STAB (M/S) (M/S) (M) HT (M) Y (M) Z (M) DWASH

------- ---------- ---- ----- ----- ------ ------ ------ ------ ----- 40000. .2243 5 1.0 2.0 10000.0 234.08 1382.49 149.12 NO 50000. .2001 5 1.0 2.0 10000.0 234.08 1678.35 158.35 NO

MAXIMUM 1-HR CONCENTRATION AT OR BEYOND 40000. M: 40000. .2243 5 1.0 2.0 10000.0 234.08 1382.49 149.12 NO

DWASH= MEANS NO CALC MADE (CONC = 0.0) DWASH=NO MEANS NO BUILDING DOWNWASH USED DWASH=HS MEANS HUBER-SNYDER DOWNWASH USED DWASH=SS MEANS SCHULMAN-SCIRE DOWNWASH USED DWASH=NA MEANS DOWNWASH NOT APPLICABLE, X<3*LB

*************************************** *** SUMMARY OF SCREEN MODEL RESULTS *** ***************************************

CALCULATION MAX CONC DIST TO TERRAIN PROCEDURE (UG/M**3) MAX (M) HT (M)

-------------- ----------- ------- ------- SIMPLE TERRAIN .2243 40000. 0.

*************************************************** ** REMEMBER TO INCLUDE BACKGROUND CONCENTRATIONS ** ***************************************************

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