### MEMORANDUM SUBJECT: Fenceline Ambient Benzene Concentrati ons surrounding Petroleum Refineries FROM: Ted Palma, Physical Scientist USEPA/OAQPS/Health and Environmental Impacts Division Darcie Smith, Physical Scientist USEPA/OAQPS/Health and Environmental Impacts Division TO: Brenda Shine, Environmental Engineer USEPA/OAQPS/Sector Policies and Programs Division DATE: January 7, 2014 Background Benzene is a key hazardous air pollutant emitted by all petroleum refineries. To support the effort to develop a fenceline monitoring program around petroleum refineries, EPA risk assessors estimated the maximum chronic off-site ambient benzene conc entrations surrounding each of the 148 petroleum refinery facilities in the country ba sed on the benzene emissions inventor y developed for these sources. Approach In support of the residual risk and technology review required by CAA sections 112(f) and 112(d)(6) for this source sector, on April 1, 2011 EPA sent out an information collection request (ICR) under the authority of Section 114 of the C AA to the petroleum refining industr y. The ICR requested available information regarding process equipment, control de vices, point and fugitive emissions of all HAP, practices used to control fugitive emissions, and other aspects of facility operations, including stack parameters and locations for each of the two refine ry source categories (MACT 1 and MACT 2) covered in the proposed rulemaking as well as all other sources present at the facility (i.e., whole facility). Details on the ICR and development of the emissions inventory for risk assessment modeling can be found in the National Emission Standards for Air Polluta nt Emissions: Petroleum Refinery Sector. This is believed to be the best available, most current emissions inventory for this industry. Further, EPA used this inventory to develop es timates of HAP emissions at each f acility after full implementation of the proposed standards, calling this the “post-cont rol” emissions inventory. While the ICR and emissions inventories contained estimates of all h azardous air pollutants emitted from the facility, as noted above benzene was select ed as a surrogate for purposes of estimating fenceline HAP concentrations. Following development of the pos t-control emissions invent ory, long- term ambient concentrations for each facility in the source ca tegory were estimated using the EPA’s American Meteorological Society/EPA Regulatory Model dispersion modeling system (AERMOD). The

### AERMOD is a state-of-the-science Gaussian plum e dispersion model that is preferred by EPA for modeling point, area, and volume sources of continuous air emissions from facility applications. The model is used to develop annual average ambient concentrations through the simulation of hour-by-hour dispersion from the emission sources into the surroundi ng atmosphere. Hourly emission rates used for this simulation are generated by evenly dividing the total annual emission rate from the inventory into the 8,760 hours of the year. Concentra tions are estimated by the model at a set of polar grid receptors centered on the facility as well as surrounding census block centroid receptors extending from the facility outward to 50 km. For purposes of this modeling analysis, EPA assumed that the nearest offsite polar grid receptor (P) was the best representati on of each facility’s fencel ine concentration in the post-control case, unless there was a census block centroid that was ne arer to the fenceline than the nearest off-site polar grid receptor. In those inst ances, EPA estimates the fenceline concentration as the concentration at the census block centroid (C) (see A ttachment 1). Only receptors (either the polar or census block) that were estimated to be outside the facility fenceline were considered in determining the maximum benzene level for each facility. Meteorology for the analysis generally consisted of a single year of data from a nearby nationa l weather service office. Further details on the approach used are provided in the source category risk assessment report (Draft Residual Risk Assessment for the Petroleum Refining Source Sect or USEPA, January 2014). Results Individual facility estimates of the maximum ambient annual average offsite benzene concentration are provided in Attachment 1. The maxi mum offsite annual average at any facility is estimated to be 9 μg/m 3 

### . The average of the estimated maximum con centrations across all 142 facilities is 0.8 μg/m 3



### . Four facilities are estimate d to create ambient benzene levels at or above 4 μg/m 3 

### , while 36 are estimated to create maximum ambi ent benzene levels above 1 μg/m 3 

### . In most cases, maximum off-site annual average concentrations are estimated to occur at or just adjacent to the fac ilities fenceline. Figure 1 shows the value and location of the maximum facility-level annual average benzene concentration at the facility with the highest modeled value in this analysis. As the figur e illustrates, this concentration is near, but just outside of, th e fenceline of the facility. It is important to keep in mind that these estimate s of ambient benzene concen trations are due only to the facility-specific emissi ons of benzene in the inventory noted above and do not reflect ambient levels from other nearby sources of benzene such as adjacen t facilities or mobile source emissions. Further the estimates do not include potential contributions from unidentified or unqua ntified on-site sources, and are subject to the typical uncertainties as sociated with estimating emissions and modeling atmospheric dispersion. We note that a recent model-to-monitor comparison of chronic ambient benzene concentrations conducted for the 2005 National Air Toxic Assessment (NATA) (http://www.epa.gov/ttn/atw/nata200 5/05pdf/nata2005_model2monitor.pdf) , which utilized the same modeling approach, found average m odel-to-monitor ratios between 0.9 to 1.1. Thus, we have a high degree of confidence that the disp ersion modeling approach utilized in this analysis will provide accurate benzene concentrations adja cent to the subject facilities.

### Figure 1. Maximum Off-site Annual Average Benzene Concentration Adjacent to Facility NEI33031

Attachment cc: Erika Sasser Kelly RimerFacility NEI ID Max Conc (ug/m3) Census Block / Polar Receptor Latitude Longitude NEI33031 9 P 29.99787 ‐ 90.3970 4 NEI12988 5 P 36.66466 ‐ 97.08543 NEI12711 4 P 29.72632 ‐ 95.25439 NEI33010 4 P 30.13709 ‐ 93.32137 NEI12486 3 P 28.4625 4 ‐ 98.18753 NEI876 3 P 33.20236 ‐ 92.67681 NEI12458 3 P 45.65532 ‐ 108.76732 NEI6166 3 P 30.19286 ‐ 93.32202 NEI18372 3 P 30.77933 ‐ 88.05951 NEI42016 3 P 40.84067 ‐ 111.92355 NEI11663 2 P 40.7127 4 ‐ 84.12492 NEI6130 2 C 30.4776 4 ‐ 91.20601 NEI42583 2 P 46.69099 ‐ 92.0658 8 NEI32762 2 P 37.79026 ‐ 96.87261 NEI371 2 P 42.86427 ‐ 106.23821 NEI40732 2 C 41.83017 ‐ 79.1247 0 NEI6136 2 C 30.53457 ‐ 91.75137 NEI41864 2 P 27.84163 ‐ 97.52475 NEI55835 2 P 38.84236 ‐ 90.0538 0 NEI40723 2 C 39.92161 ‐ 75.19419 NEI34898 2 P 32.85445 ‐ 104.39475 NEI6519 1 P 29.06465 ‐ 95.75525 NEI49781 1 C 39.00496 ‐ 87.7255 6 NEI2KS125003 1 P 37.05288 ‐ 95.6076 0 NEI11715 1 P 41.68487 ‐ 87.4738 8 NEI34907 1 P 35.48633 ‐ 108.42925 NEI42020 1 C 40.89069 ‐ 111.91001 NEI11449 1 C 41.69193 ‐ 83.4472 6 NEI34050 1 P 44.85609 ‐ 93.00545 NEI42370 1 P 47.25273 ‐ 122.39775 NEI46556 1 C 17.71525 ‐ 64.75793 NEI12460 1 P 45.82142 ‐ 108.4297 7 NEI11192 1 C 31.76743 ‐ 106.40501 NEI7130 1 P 29.34569 ‐ 98.46071 NEI18406 1 C 64.7288 0 ‐ 147.35141 NEI11574 1 P 40.77267 ‐ 81.42201 NEI18408 0.9 P 64.73552 ‐ 147.34841 NEI13322 0.9 P 21.30509 ‐ 158.1145 0 NEI42382 0.9 C 48.46419 ‐ 122.5679 6 NEI11885 0.8 C 42.27993 ‐ 83.1493 6 NEI12084 0.8 P 27.82325 ‐ 97.48873 NEI34057 0.8 P 30.3206 0 ‐ 88.48512 Attachment 1 Maximum Predicited Off ‐ Site Ambient Benzene Concentrations

1 of 4Facility NEI ID Max Conc (ug/m3) Census Block / Polar Receptor Latitude Longitude NEI6062 0.8 C 30.25247 ‐ 93.2723 6 NEI6436 0.7 C 29.3809 4 ‐ 94.92845 NEI20616 0.7 P 33.87289 ‐ 118.1597 8 NEI363 0.7 P 41.12698 ‐ 104.78535 NEI53718 0.7 P 41.42458 ‐ 88.1841 4 NEI6022 0.7 P 30.47572 ‐ 91.19501 NEI6123 0.6 C 29.94009 ‐ 89.9717 4 NEI02185REF5 0.6 P 70.32646 ‐ 149.6050 4 NEI109 0.6 C 39.81992 ‐ 75.4197 4 NEI6127 0.6 C 29.9364 4 ‐ 89.94282 NEI7781 0.6 C 29.73146 ‐ 95.01372 NEIWYT$1215 6 0.5 P 41.26311 ‐ 110.8064 7 NEI05139REF1 1 0.5 P 33.36493 ‐ 92.71275 NEI42413 0.5 P 48.89636 ‐ 122.74343 NEI46752 0.5 P 40.61551 ‐ 80.63267 NEI43243 0.5 C 41.77862 ‐ 107.1127 6 NEI7233 0.5 P 30.07883 ‐ 94.0731 8 NEI33008 0.5 C 32.47127 ‐ 93.79299 NEI02185REF 4 0.5 P 70.25488 ‐ 148.35501 NEI11119 0.4 P 29.73121 ‐ 95.11721 NEI40371 0.4 P 46.85179 ‐ 100.8707 0 NEI12969 0.4 P 36.14521 ‐ 96.0087 4 NEI11450 0.4 C 41.63321 ‐ 83.49532 NEI26473 0.4 P 32.10499 ‐ 81.12462 NEI41591 0.4 P 35.08812 ‐ 90.07445 NEI6475 0.4 C 32.36581 ‐ 95.28325 NEI11200 0.4 P 29.87087 ‐ 93.9661 4 NEINJT$891 0.4 C 39.84275 ‐ 75.2479 0 NEI12044 0.4 C 29.37901 ‐ 94.9107 8 NEI7988 0.4 P 27.8091 4 ‐ 97.4326 4 NEI34061 0.4 P 31.81567 ‐ 89.0074 6 NEI2NV110905 0.3 P 38.62078 ‐ 115.6190 4 NEI20154 0.3 P 35.39483 ‐ 119.04533 NEI26533 0.3 P 21.30106 ‐ 158.0966 7 NEI6116 0.3 P 29.66963 ‐ 89.9707 4 NEI6963 0.3 P 35.7006 4 ‐ 101.35233 NEI12791 0.3 P 29.37451 ‐ 94.88921 NEI7441 0.3 P 29.90022 ‐ 93.97262 NEI42040 0.3 C 40.79986 ‐ 111.9144 4 NEI41863 0.3 C 27.80795 ‐ 97.45492 NEI12480 0.3 P 29.73071 ‐ 95.21391 NEI40531 0.3 P 34.6358 4 ‐ 97.1645 8 NEI21130 0.3 P 33.89713 ‐ 118.1426 8 NEI32864 0.3 C 38.37415 ‐ 82.5867 4 NEI41771 0.3 P 29.95579 ‐ 93.8936 4 2 of 4Facility NEI ID Max Conc (ug/m3) Census Block / Polar Receptor Latitude Longitude NEI42081 0.3 P 40.83179 ‐ 111.9244 4 NEI19870 0.3 P 38.05765 ‐ 122.2607 8 NEI12459 0.3 P 45.7838 4 ‐ 108.48222 NEI42425 0.3 P 48.83963 ‐ 122.69135 NEI42381 0.3 C 48.48863 ‐ 122.55232 NEI13371 0.2 C 60.67983 ‐ 151.3659 7 NEI32801 0.2 C 38.36035 ‐ 97.6743 0 NEI6617 0.2 P 27.81467 ‐ 97.49765 NEI40039REF103 3 0.2 P 35.6935 0 ‐ 98.66335 NEI42309 0.2 P 37.22601 ‐ 76.43341 NEI404 0.2 P 43.84852 ‐ 104.2179 7 NEI25450 0.2 P 38.06709 ‐ 122.1237 7 NEI7134 0.2 P 27.81565 ‐ 97.41899 NEI12968 0.2 P 36.11221 ‐ 96.0069 8 NEI6375 0.2 C 40.64209 ‐ 74.22462 NEI12464 0.2 P 47.52463 ‐ 111.28821 NEI19587 0.1 P 37.9433 4 ‐ 122.38152 NEI6084 0.1 C 30.10181 ‐ 90.9075 8 NEI34022 0.1 P 44.7533 0 ‐ 93.0372 8 NEI20467 0.1 C 33.91713 ‐ 118.40801 NEI889 0.1 P 39.80721 ‐ 104.94512 NEI113 0.1 C 39.82745 ‐ 75.39881 NEINMT$1247 8 0.1 P 32.87441 ‐ 103.29923 NEI6087 0.1 C 30.05835 ‐ 90.59093 NEI20966 0.1 P 33.94597 ‐ 118.1640 8 NEI2CA254640 0.1 P 34.93051 ‐ 120.51069 NEI46764 0.1 C 41.97837 ‐ 78.6200 8 NEI18394 0.1 P 33.1944 0 ‐ 87.60883 NEI2CA314628 0.1 P 38.03532 ‐ 122.06583 NEI11232 0.1 C 29.7311 4 ‐ 95.23785 NEIOKT$1100 9 0.1 P 34.21512 ‐ 97.10752 NEI53702 0.1 C 41.64506 ‐ 88.04593 NEI32353 0.1 P 37.93962 ‐ 87.9162 4 NEI20103 0.1 C 35.29259 ‐ 118.91221 NEICA0370363 0.1 P 33.77005 ‐ 118.2773 6 NEI2CA131003 0.1 C 33.79987 ‐ 118.2210 4 NEI19834 0.1 P 38.03548 ‐ 122.12911 NEICA0379991 0.1 P 33.8005 0 ‐ 118.2381 8 NEI20797 0.05 P 33.79579 ‐ 118.2382 7 NEICA1910268 0.04 C 33.79232 ‐ 118.22299 NEI6095 0.04 P 30.0020 4 ‐ 90.3901 4 NEI21034 0.04 P 33.8521 0 ‐ 118.3171 6 NEI34872 0.04 P 40.56527 ‐ 74.2500 4 NEI6446 0.03 P 32.27176 ‐ 101.42189 NEI32997 0.02 P 37.07069 ‐ 84.61031 3 of 4Facility NEI ID Max Conc (ug/m3) Census Block / Polar Receptor Latitude Longitude NEI8139 0.02 C 35.94462 ‐ 101.90042 NEI19869 0.02 P 35.03892 ‐ 120.5973 4 NEI21466 0.01 C 33.7776 4 ‐ 118.24223 NEI01053REF1_5 0.01 P 31.18032 ‐ 87.43803 NEI26218 0.01 C 39.57491 ‐ 75.60037 NEI20174 0.01 P 35.36919 ‐ 119.0815 4 NEI33007 0.01 P 32.59303 ‐ 93.51312 NEI34873 0.003 C 40.53223 ‐ 74.2640 6 NEI34069 0.002 P 32.4106 4 ‐ 90.91859 NEI18415 0.001 P 61.06517 ‐ 146.2902 4

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