MEMORANDUM

Date: May 13 , 201 4

Subject: MACT

- Allowable Emissions for the Off

- Site Waste and Recovery Operations Source Categor y

From: Lesley Stobert, EC/R Incorporated

To: Paula Hirtz, EPA/OAQPS/SPPD

_________________________________________________________________________________ The purpose of this memorandum is to present analyses related to the determination of “MACT

- allowable” emissions levels and risks for the Off

- Si te Waste and Recovery Operations (OSWRO) source categor y being addressed under the EPA’s Risk and Technology Review (RTR)
program.

The RTR program addresses statutory requirements in section 112(f) and 112(d)(6) of the Clean Air Act (CAA) for federal air toxics regulations. The federal air toxics regulations are National Emission Standards for Hazardous Air Pollutants (NESHAP) contained in 40 CFR part 63 ( commonly referred to as Maximum Achievable Control Technology (MACT) standards ) . The e missions data used for the RTR risk assessment for th is categor y consist s of data representative of “actual” emission levels. In addition to the risks associated with these actual emission levels, the EPA also consider ed the levels of HAP emissions that so urces could emit and still be in compliance with the applicable MACT regulation. These emission levels are referred to as “MACT

- allowable” emissions. The purpose of this memorandum is to discuss these MACT

- allowable emission levels for the OSWRO
source cat egory and to relate the potential risks if facilities emitted at these levels.

This memorandum is organized as follows. Section 1 presents the estimated maximum risk levels based on the actual emission levels for the source category. Section 2 presents the approach to estimating the risks at the MACT

- allowable levels. The last section (Section 3) presents a discussion of the estimation of the MACT

- allowable emission level for the OSWRO MACT standards . Section 3 also includes a presentation of the estimat ed risks at the estimated MACT

- allowable emissions levels.

1.0 Risk Levels Based on Actual Emissions

The estimated maximum inhalation risks for the source category are summarized in Table 1. These risks are based on actual emission levels.2

Table 1. Summary of Estimated Inhalation Risks for the OSWRO Source Category Based On Actual Emissions Levels

Source Category Maximum individual cancer risk (in a million) 1 Maximum chronic non

cancer TOSHI 2 Off

- Site Waste and Recovery Operations (OSWRO) 9 0.6

1 Maximum individual excess lifetime cancer risk.

2 Maximum target organ specific hazard index (TOSHI). The maximum TOSHI is based o n respiratory ef fects.

2.0 Approach t o Estimating Risks from MACT

- Allowable Emiss ion Levels

Detailed MACT

- allowable emissions information is not available on an emission point

specific level. Therefore, modeling was not conducted to estimate the risks from MACT

- allowable emission levels.

The basic approach to estimate the risks from MACT

- allowable emission levels was to first estimate the relations hip between the actual and MACT

- allowable emission levels, and then to estimate the potential risk impacts from the differences between actual a nd MACT

- allowable emissions. In general, the risk impact was assumed to be proportional to the difference in emissi on levels. For example, if MACT

- allowable emissions were estimated to be three times as high as actual emissions, it was assumed that risks could be as much as three times as high as those estimated from the modeling conducted using actual emissions.

This assumption regarding the linear relationship between emissions and risks is generally reasonable for chronic cancer and non

- cancer risks. However, using this approach for acute ris ks would likely overestimate the impacts. The acute assessment already has numerous built in conservative assumptions. First, the acute assessment assumed a short

- term emission rate up to 10 times that of the average longer term emission rate. Also, the ma ximum acute risks assume the simultaneous occurrence of independent factors that may vary greatly, such as hourly emissions rates, meteorology, and human activity patterns. In the assessment using actual emissions, EPA assumed that individuals remained for 1 hour at the point of maximum ambient concentration as determined by the co

- occurrence of peak emissions and worst

- case meteorological conditions. These assumptions would tend to overestimate actual exposures since it is unlikely that a person would be l ocated at the point of maximum exposure during the time of worst

- case impact. The addition of another factor to account for the MACT

- allowable emissions level would further increase the conservativeness of the estimated MACT

- allowable acute risks. Therefor e, this analysis does not discuss acute risks or estimate acute risks for the MACT

- allowable emissions level.

3.0 Analysis and Results

The OSWRO NESHAP addresses emissions from the followin g types of emission sources : (1) storage tanks, (2) oil

- water and organic

- water separators , (3) surface impoundments , (4) containers

, (5) transfer systems , (6) process vents
, and (7) equipment leaks. Table 2 summarizes the formats of the standards for these emission points.3 Table 2. Format s of Standards for the OSWRO NESHAP

Emission Source Type Format of Primary Standard Storage Tanks Equipment Standards or Performance Standard (% reduction) Oil

- Water and Organic

- Water Separators Equipment Standards a Surface Impoundments Equipment Standards a

Containers Equipment Standards a , Performance Standard (% reduction) for containers used for waste stabilization Transfer Systems Equipment Standards a Process Vents Performance Standard (% reduction) Equipment Leaks Work Practice Standards

a As an alternative, the N ESHAP allows emissions to be routed through a closed vent system to a control device that reduces emissions by 95%

The ability to estimate MACT

- allowable emissions for specific emission points, or for specific emission point types, is largely dependent on the format of the standards. For equipment standards, sources subject to the OSWRO NESHAP are required to install specific equipment. Assuming t hat the equipment is maintained properly and is in good working condition (as required), there would not be a difference in the actual emissions level and the level allowed by the standard. Based on data collected from facilities through a CAA section 114 information collection request, facilities are complying with the equipment standards rather than the alternative standard to vent emissions through a closed vent system routed to a control device for oil

- water and organic

- water separators, surface impound ments, containers and transfer systems. Similarly, f or emission sources subject to work practice requirements, there would be no dif ference between actual and MACT

- allowable emissions, provided that facilities are not conducting additional work practices p roven to reduce emissions beyond those required in the rule. W e are not aware of any such situations at facilities in the OSWRO source categor y . Therefore, for equipment leaks, oil

- water and organic

- water separators, surface impoundments, containers and tr ansfer systems , which are subject to equipment and work practice standards, we believe that the actual emission levels are a reasonable estimation of the levels allowed by the standard.

For process vents, the OSWRO NESHAP requires an emissions reduction of 95% of either the total organic compounds or the specific HAP listed in Table 1 of the rule

. For storage tanks, the OSWRO NESHAP requires either the installation of a floating internal or external roof, pressure vessel, or fixed roof with emissions to b e routed through a closed vent system to a control device reducing either the total organic compounds or the specific HAP listed in Table 1 of the OSWRO NESHAP by 95%

. Based on information from the CAA section 114 information collection request, tanks in the OSWRO source category are controlled by fixed roofs that are vented to control devices. In addition, information from the CAA section 114 information collection request shows that emissions reductions from some control devices on process vents and storage tanks are 9 9 %. In these cases, 5 % of the uncontrolled amount of H AP would be emitted at the MACT

- allowable level, while some process vents and tanks are actually only emitting 1 % (i.e., 9 9 % emissions reduction). The rati o of MACT

- allowable to a ctual emissions for these emissions sources is therefore 5 / 1 = 5.4

For facilities where data were available to determine whether an emission s point was a process
vent , tank or other type of emissions source (i.e., facilities that provided data in response to the CAA section 114 information collection request) , this ratio of 5 was applied to the process vent and tank emissions. For facilities where only NEI data were available, it was not possible to determin e whether an emission s point was a process vent , tank or other type of emissions source , and th e ratio of 5 could not be applied to only process vent and tank emissions. For these facilities, this ratio was revised to a value that could be applied to all t he OSWRO emissions . Based on data from the CAA section 114 information collection request responses, emissions from pr ocess vents and storage tanks contribute approximately 50% to the total OSWRO HAP emissions. The ratio of 5 was revised to 2.5 to reflect the impact a factor of five applied to 50% of the emissions would have on the total OSWRO emissions. This factor of 2.5 was then applied to the total OSWRO emissions for the facilities with only NEI data available

. The impacts on the cancer MIR and non

- cancer TOSHI were determined based on the application of the factors of 5 and 2.5 to the OSWRO emissions. The MIR based on actual emissions is 9 , which is caused by a facility with only NEI emissions data. The application of a factor of 2.5 to the emis sions at this facility results in the MIR at the MACT

- allowable level of 2 0

. a The maximum TOSHI bas e d on actual emissions is 0.6, which is also caused by a facility with only NEI emissions data. The application of a factor of 2.5 to the emissions at this f acility results in the maximum TOSHI at the MACT

- allowable level of 1

. a These values for the MIR and TOSHI were the highest values estimated in our analyses , even when considering the application of a factor of 5 to process vent and tank emissions at facilities where emission point data were available.

The resulting risks based on the application of the ratio s of 5 and 2.5 are shown in the MACT

allowable level risks presented in Table 3.

Table 3 . Summary of Estimated Inhalation Risks for the OSWRO Source Category Based On MACT

- Allowable Emissions Levels

Actual MACT

- Allowable

Source Category Maximum individual cancer risk (in a million) Maximum

chronic non

cancer TOSHI Maximum

individual cancer risk (in a million) Maximum

chronic non

cancer TOSHI

Offsite Waste and Recovery Operations 9 0. 6 2 0 1

a The TOSHI at the reported actual emissions level is 0.5978. This value multiplied by 2.5 is 1.49, which rounds down to 1. The MIR at the reported actual emissions level is 9. This value multiplied by 2.5 is 2 2.5 , which rounds down to 20. TOSHI and MIR values are presented with one significant digit.