Technical Memorandum 

TO: EPA Docket No. EPA-HQ-OAR-2010-0682 

FROM: Brenda Shine, Environmental Engineer 

Refining and Chemicals Group, SPPD (E143-01) 

DATE: January 6, 2014 

SUBJECT: Post Control Modeling Results 

I. Purpose: 

The purpose of this memo is to summarize the approach used to estimate the risk reductions 

associated with the proposed control scenarios on the Petroleum Refining source category. 

While the draft risk report for the source category presents post control risk results relating to 

maximum individual risk (MIR), incidence, and non cancer effects for all emission sources in the 

refining source categories, this memorandum presents additional results related to cancer 

incidence and incidence reductions associated with specific types of emission sources. 

II. Background: 

The EPA conducted a detailed Information Collection Request (ICR) of all U.S petroleum 

refineries. The ICR had four components: (1) a questionnaire on processes and controls to be 

completed by all petroleum refineries (Component 1); (2) an emissions inventory to be 

developed by all petroleum refineries using the emissions estimation protocol developed for this 

effort (Component 2); (3) distillation feed sampling and analysis to be conducted by all 

petroleum refineries (Component 3); and (4) emissions source testing to be completed in 

accordance with an EPA-approved protocol for specific sources at specific petroleum refineries 

(Component 4). The emissions inventory submitted in response to Component 2 of the ICR was 

used as the input for the modeling file to estimate the risk associated with refinery process 

emissions. 

III. Post Control Scenarios: 

For each emission source within the refining MACT 1 or MACT 2 source categories, we applied 

a reduction in emission estimates resulting from application of proposed controls. The “postcontrol” emission file used the quality-assured ICR Component 2 emissions file as a starting 

point. As facilities could report in Component 2 the groupings of sources included in Component 

1, it was not practical to perform the post-control emission estimates at the individual release 

point level. Instead, facility-specific emission reduction factors were developed from the results 

of the technology review analysis conducted using ICR Component 1. These reduction factors 

were used to adjust the emissions of all pollutants reported for that specific source type at that 

facility to account for the post-control emissions. For example, an overall HAP emission 

reduction factor was calculated for storage tanks for a given facility based on the number and 

types of tanks, the type of fluid in the tank and the additional controls required to comply with 
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the proposed standards for storage vessels. That overall HAP reduction factor was then applied 

uniformly to all storage vessel emissions (all pollutants) reported for that facility. Table 1 

presents emissions, before and after control, associated with the proposed controls, which 

impacts delayed coking units, equipment leaks, and storage vessels. 

TABLE 1. EMISSION REDUCTIONS FROM POST CONTROL SCENARIO 

Emission Process Group 

Baseline, 

TPY 

Post Control, 

TPY Reductions 

Boilers (external combustion) 381 381 0% 

Catalytic cracking unit vent 5081 5081 0% 

Catalytic reforming unit vents 92 92 0% 

Chemical processes HON 12 12 0% 

Chemical processes hydrogen 34 34 0% 

Coking unit vents & coke handling 410 218 47% 

Cooling towers 2078 2078 0% 

Degreasing/cleaning/painting 78 78 0% 

Flares 1189 1189 0% 

Fugitive dust/blasting/construction 147 147 0% 

Incinerators 78 78 0% 

Internal combustion engines 198 198 0% 

Labs 3 3 0% 

Marine vessel loading and unloading 244 244 0% 

Miscellaneous process vents 57 57 0% 

Other combustion 3 3 0% 

Other waste treatment/disposal 4 4 0% 

Process equipment leaks 2982 2982 0% 

Process heaters 1467 1467 0% 

Refinery processes (other) 618 618 0% 

Storage vessels 1664 969 42% 

Sulfur recovery unit vents 482 482 0% 

Tank car & truck loading and unloading 68 68 0% 

Wastewater treatment 2776 2776 0% 

TOTAL 20145 19257 4% 

It is important to note that the emission reductions anticipated from application of the proposed 

standards as presented in Table 1 differ from the rule’s presented impacts because of the way in 

which the baseline emission estimates were developed. In developing the impacts for the rule, 

emission estimates were developed using modeling techniques and site-specific data on the units 

as reported in Component 1 of the ICR (e.g., size of vessels, temperature of coke drum when 

venting, number of valves and pumps, type of roof and fitting controls, etc.). The modeled 
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baseline emissions estimates for storage vessels agree reasonably well with the industry’s 

reported emissions inventory because the emission estimation procedures for these sources has 

been well established for years. The modeled baseline emission estimate for delayed coking 

units were quite different from the reported emissions for several reasons. First, the emission 

estimation protocol for delayed coking units is new and not all facilities reported emissions for 

their delayed coking units or they reported emission but did not use the emission factors and 

methodologies provided in the Emission Estimation Protocol for Petroleum Refineries (RTI, 

2011). As such, the emissions reported in the refinery-supplied inventory dataset (Component 2) 

were less than projected using the Protocol’s default emission factor and the number of coke 

drums and cycle times as reported in Component 1 of the ICR. Second, in order to develop 

impacts for different control options, a more detailed model had to be developed to account for 

changes in emissions at different coke drum vessel venting pressures (and/or drum 

temperatures). Consequently, there may also be a significant difference in the emissions 

estimated using the impact model’s unit-specific approach and the emissions estimated for that 

same unit using the Protocol’s default emission factor. 

Given the differences outlined above, a delayed coking unit projected to have large baseline 

emissions when developing the rule’s impacts is likely to average (or no) emissions in the 

reported inventory. The delayed coking units with the largest modeled baseline emissions were 

those that reported to vent at the highest drum temperature or pressure, so these units were also 

the units that had the largest emission reductions when controls were applied. If these units did 

not have the high baseline emissions in the industry-supplied inventory, the overall percent 

emission reduction calculated in the inventory dataset would be less than the emission reductions 

projected using the impact model dataset. For example, assume the impact model’s baseline 

emission estimates for delayed coking units at three facilities were 5, 10, and 100 tons/yr and the 

post-control emissions were 5, 10, and 10 tons/yr, resulting in a projected 78 percent reduction 

from baseline. From this data, post-control reduction factors for these facilities would be 0, 0, 

and 90 percent, respectively. If the emissions reported in the inventory for these three facilities 

were 6, 8, and 7 tons/yr, the post-control inventory would be calculated as 6, 8, and 0.7 tons/yr 

(applying the 90 percent reduction for Facility 3), resulting in only a 30 percent reduction in the 

post-control inventory emissions. 

Emission estimating procedures for delayed coking units presented in the Protocol were new and 

uncertain. These methodologies were further revised when developing impacts for control 

options, leading to high emissions projected for a select number of facilities. Even with the 

differences in the emission estimation approach used between the impacts model and inventory 

data set, the post-control factors applied to the inventory dataset still project significant 

emissions reductions from delayed coking units. 

IV. Post Control Incidence 

The cancer incidence for key emission sources as determined using the reported (baseline) 

emissions inventory data and the post-control inventory emission estimates is presented in 

Table 2 and graphically presented in Figure 1. 
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TABLE 2. INCIDENCE REDUCTION FROM CONTROLS 

Emission Source 

Baseline 

Cancer 

Incidence 

(cases/yr) 

Source 

Contribution to 

Baseline 

Cancer 

Incidence 

(% of 

total) 

Postcontrol 

Cancer 

Incidence

(cases/yr)

Reduction in 

Cancer 

Incidence 

% 

Reduction 

in Cancer 

Incidence 

from 

Source 

 % 

Reduction 

in Cancer 

Incidence 

Overall 

Delayed Cokers 0.104 31% 0.052 0.052 50% 15% 

Equip Leaks 0.078 23% 0.078 0 0% 0% 

Wastewater 0.042 12% 0.042 0 0% 0% 

FCCU 0.033 10% 0.033 0 0% 0% 

Cooling Towers 0.021 6% 0.021 0 0% 0% 

Storage Tanks 0.025 7% 0.015 0.010 39% 3% 

Flares 0.018 5% 0.018 0 0% 0% 

Other 0.018 5% 0.018 0 0% 0% 

Total 0.340 100% 0.278 0.062 18% 

V. References 

RTI. 2011. Emission Estimation Protocol for Petroleum Refineries. Version 2.1.1, Final ICR 

Version Corrected. Prepared for U.S. Environmental Protection Agency, Office of Air 

Quality Planning and Standards, Research Triangle Park, NC. May 2011. 

 
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Figure 1. Comparison of cancer incidence pre-control (baseline) and post-control for key refinery emissio

0.000.020.040.060.080.100.12

Cancer Incidence (Cases per year)

Refinery Source

Cancer Incidence for Each Source by Pollutant (Pre vs. Post Cont

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