1

M E M ORA N D U M

D A TE: May 30
, 2014

S UBJ E CT: Estimated Risk s and Risk Reductions Associated with the Emissions Controls

Options Considered in the Ample Margin of Safety Analysis for the Off

- Site Waste and Recovery Operations Source Category

F RO M : Lesley Stobert, EC/R Incorporated

TO: Paula Hirtz , EPA/OAQPS

The pur p ose o f this m e m o ra ndum i s to describe how risks and risk reduction s w ere estimated for each of the emissions control options considered in the ample margin of safety analysis conducted for the Off

- Site Waste and Recovery Operations (OSWRO) sou r c e ca t e gor y under the EPA’s Risk and Technology Review (RTR) program

.

1.0 BACKGROUND
As directed by section 112(f)(2) of the Clean Air Act, a baseline risk assessment was conducted to ass e ss t he h ea l t h a nd e nvironme n t a l risks that re main a ft e r affected facilities have

c omp l ied with the maximum achievable control technology (MACT) standards for the OSWRO source category (40 CFR part 63, subpart DD). The results of these baseline risk assess m ents were analyzed to determine whether more stringent standards must be set. The first step in the process of evaluating residual risk is the d etermination of acceptable risk. It was determined that the risks from the OSWRO source category are acceptable , considering the available health risk information and factors, including the uncertainties associated with the risks

. The second step is the determination of whether standards must be further revised in order to provide an ample margin of safety to protect public health. The ample margin of safety is the level at which the standards must be set, unless an even more stringent standard is necessa ry to prevent, taking into consideration costs, energy, safety and other relevant factors, an adverse environmental effect. While the baseline risks were determined to be acceptable, in striving to provide the maximum feasible protection against risks to h ealth from hazardous air pollutants ( HAP )
, available emissions control options that might reduce the risk associated with HAP emissions from the source category were then estimated, along with all of the health risks and other health information considered in determining risk acceptability , in the ample margin of safety decision process

.2

2.0 IDENTIFIED EMISSIONS AND RISK REDUCTION OPTIONS

A s part of the RTR
, a technology review was conducted that focused on identifying developments in practices, processes and control technologies for the emission sources in the OSWRO production source category

. Through this review, several developments in practices, process or control technologies were identified

. 1 T he control options identified to reduce risks

ar e the same as those identified in the technology review

. No options were identified that would reduce HAP emissions from containers, surface impoundments, oil

- water separators, organic

water separators or transfer systems beyond what is currently required in the rule. For process vents, tanks and equipment leaks, several additional control options were identified that might reduce the risk associated with emissions from the source category . For process vents, one emissions control option was identified that would require compliance with a 98 percent reduction in HAP emissions rather than the currently required 95 percent reduction. For tanks, two emissions control options were identified. Tanks Option 1 requires more stringent control of emissions for additi onal tanks containing liquids with lower vapor pressures, and tanks Option 2 requires compliance with a 98 percent reduction in HAP emissions rather than the currently required 95 percent reduction. For equipment leaks, two emission control options were id entified. Equipment leaks Option 1 requires compliance exclusively with 40 CFR part 63, subpart H, rather than allowing compliance with 40 CFR part 61, subpart V, without the connector leak detection and repair (LDAR) requirements of subpart H. Equipment l eaks Option 2 requires compliance with equipment leaks Option 1, plus it includes the connector LDAR requirements of subpart H.

3.0 ESTIMATION OF POTENTIAL RISKS AND RISK REDUCTION

To determine the risk reduction that would be achieved with the implementation of these control options, the maximum risk s for the source category and the amount of those risks attributed to OSWRO process vents, tanks and equipment leaks were examined

. The basic approach to estimate the risk reduction that would be ach ieved with the implementation of these control options was to first estimate the relationship between the current MACT

- allowable emission s and the MACT

- allowable emission s that would result from the implementation of the control options, and then to estima te the potential risk impacts from the differences between these emission levels. In general, the risk impact was assumed to be proportional to the difference in emission levels. For example, if MACT

- allowable emissions after implementation of the control option were estimated to be three times lower than the current MACT

- allowable emissions
, it was assumed that risks could be as much as three times lower than the risks estimated using current MACT

- allowable emissions

.

1 See Technology Review and Cost Impacts for the Proposed Amendments to the Off

- Site Waste and Recovery Operations Source Category , which is available in the docket for this action.3

T he ca ncer maximum individual risk (MIR) and noncancer target organ

- specific hazard index ( TOSHI ) were examined in this analysis, and these values were attributed to a facility for which information is not available regarding the processes and emission point types th at contribute to these maximum risk values. Because it was not possible to precisely determine the magnitude of HAP emissions from specific process types and how those emissions relate to the risk estimates, it was conservatively assumed that the type of e quipment under investigation was responsible for the maximum risks. For example, in the assessment of process vents, it was

as sumed the maximum risks for were due to process vents. An evaluation of how further controls might reduce this risk was then under taken

. Table 1 provides a summary of the OSWRO inhalation risk assessment results and the estimated risks that would occur with the implementation of the identified control options

. The sections that follow describe how the levels were estimated for each e quipment type w h ere alternative control options were identified.

Table 1 . Summary of OSWRO Baseline Inhalation Risks and Estimated Risks After

Implementation of Identified Control Options

Source Category Actual MACT

- Allowable 1 Maximum individual

cancer risk (in a million) Maximum

chronic non

cancer TOSHI Maximum

individual cancer risk (in a million) Maximum

chronic non

cancer TOSHI OSWRO 9 0.6 20 1 Control Options Process V ents option

----- ----- 8 0.4 Tanks Option 1

----- ----- 1 0.05 Tanks Option 2

----- ----- 0.4 0.02 EL Option 1 7 0.5

----- ----- EL Option 2 5 0.3

----- ----- 1 Emissions from equipment leaks are estimated to be the same at actual and MACT

- allowable emission levels.

3.1 Process V ents

For process vents emissions control option was identified that requir es compliance with a 98 percent reduction in HAP emissions rather than the currently required 95 percent reduction. In this case, 5 percent of the HAP is currently emitted at the MACT

- allowable level, and the control option would require that only 2 percent of the HAP could be emitted at the MACT

- allowable level. Therefore, emissions would be reduced by 60 percent with this control option (i.e., 5 percent emitted reduced to 2 percent emitted for a differen ce of 3 percent , and 3/5 =0.6=60% ). To assess the maximum potential for risk reduction that could result from this process vent control option, it was assumed that the maximum risks are due to emissions from a process vent with emissions controlled at 95 percent and that the emissions and resulting risks would be reduced by 60 percent

. As shown in Table 1 , the maximum cancer MIR at the MACT

- allowable emissions4

level is 20

- in

- 1 million , and the maximum non

- cancer TOSHI at the MACT

- allowable emissions level is 1

. Applying the emissions reduction factor to the cancer MIR value results in a MIR of 8

- in

- 1 million (i.e., 20 *(1

- 0.6) = 8)
, and application of this factor to the non

- cancer TOSHI value results in a TOSHI of 0.4 (i.e., 1 *(1

- 0.6) = 0.4)

. 3 .2 Tanks

For tanks
, two emissions control options were iden ti fied . Option 1 requires Level 2 control of emissions for additional tanks containing liquids with lower vapor pressures , where these tanks are currently required to use Level 1 emission controls . “Level 2” control essentially requires one of five options:
(1) A fixed roof tank equipped with an internal floating roof;
(2) A fixed roof tank equipped with an external floating roof;
(3) A tank with a vapor

- tight cover and vented through a closed

- vent system t o a control device that has an efficiency of 95 percent or more; (4) A pressure tank; or
(5) A tank inside a permanent total enclosure (PTE) that is vented through a closed

- vent system to an enclosed combustion control device. “Level 1” control generall y requires a fixed roof with closure devices. To assess the maximum potential for risk reduction that could result from this tank control option, it was assumed the maximum risks are due to emissions from a tank not currently subject to Level 2 controls an d that a 95 percent reduction in emissions and resulting risks would occur from this tank with the implementation of this option

. As shown in Table 1 , the maximum cancer MIR from the OSWRO source category at the MACT

- allowable emissions level is 20

- in

- 1 million, and the maximum non

- cancer TOSHI at the MACT

- allowable emissions level is 1. Applying the emissions reduction factor to the cancer MIR value r esults in a MIR of 1

- in

- 1 million (i.e., 20 *(1

- 0.95) = 1), and application of this factor to the non

- cancer TOSHI value results in a TOSHI of 0.05 (i.e., 1*(1

- 0.95) = 0.05).

Tank control Option 2 requires compliance with Option 1, plus it requires a 98 pe rcent reduction rather than a 95 percent reduction in HAP emissions from tanks that are vented through a closed

- vent system to a control device or are located in a PTE that is vented through a closed

- vent system to a control device

. To assess the maximum p otential for risk reduction that could result from this tank control option, it was assumed that the maximum risks for the OSWRO source category are due to emissions from a tank not currently subject to Level 2 controls and that a 95 percent reduction in emissions and resulting risks would occur from the implementation of control Option 1

. It was further assumed that this tank would be required with tank control O ption 2 to reduce HAP emissions by 98 percent . In this case, emissions would be5

reduced by 60 percent with tank control Option 2 over tank control Option 1 (i.e., 5 percent emitted reduced to 2 percent emitted for a difference of 3 percent , and 3/5=0.6=60%)

. As discussed above , the maximum cancer MIR from the OSWRO source category at the MACT

allowable emissions level after implementation of tank Option 1 is 1

- in

- 1 million, and the maximum non

- cancer TOSHI at the MACT

- allowable emissions level after implementation of tank Option 1 is 0.05 . Applying the emissions reduction factor of tan k control Option 2 to th is cancer MIR value results in a MIR of 0.4

- in

- 1 million (i.e., 1 *(1

- 0.6) = 0.4 ), and a pplication of this factor to this non

- cancer TOSHI value results in a TOSHI of 0. 02 (i.e., 0.05 *(1

- 0.6) = 0. 02 ).

3 .3 Equipment Leaks
The OSWRO MACT standards currently require compliance with either 40 CFR part 61, subpart V, or 40 CFR part 63, subpart H, to control emissions from equipment leaks. While many provisions of these two rules are the same or similar, 40 CFR part 63, subpart H requires the use of a more stringent leak definition for valves in gas and vapor service and in light liquid service, pumps in light liquid service, and connectors. For equipment leaks
, two emissions control options were identified

. Equipment leaks control Option 1 (EL Option 1) requires compliance exclusively with 40 CFR part 63, subpart H, without the connector LDAR requirements of subpart H. To assess the maximum potential for risk reduction that could result from this equipment leak s control opti on, several assumptions were made . For instance, it was assumed that the maximum risks for the OSWRO source category are due to emissions from equipment leaks. It was also assumed that since emissions from equipment leaks are estimated to be the same at ac tual and MACT

- allowable emission levels, the risks due to equipment leaks at the MACT

- allowable level are the same as risks due to equipment leaks at actual emissions levels. It was additionally assumed, based on the analysis of estimated ba seline equipmen t leak emissions (i.e., compliance with 40 CFR part 61, subpart V) in the technology review referenced above
, that half of the equipment leak emissions causing the maximum risks are from non

connector components (i.e. pumps and valves), and the other half are from connectors. This analysis also showed that a HAP emissions reduction of 23 % would be achieved with E L Option 1 over the baseline emissions

. As shown in Table 1
, the maximum cancer MIR from the OSWRO source category at the MACT

- allowable emissions level for equipment leaks is 9

- in

- 1 million, and the maximum non

- cancer TOSHI at the MACT

- allowable emissions level for equipment leaks 0.6 . Applying a 23 percent emissions reduction factor to the cancer MIR value results in a MIR of 7

- in

- 1 million (i.e., 9*(1

- 0. 2 3) = 7 ), and application of this factor to the non

cancer TOSHI value results in a TOSHI of 0.5 (i.e.
, 0.6*(1

- 0.23) = 0.5).
Equipment leaks control Option 2 (EL Option 2) requires compliance with EL Option 1, plus it includes the connector LDAR requirements of 40 CFR part 63, subpart H. To assess the maximum potential for risk reduction that could result from this equipment leak control option, the same assumptions described for EL Option 1 were made

. Based on the analysis of estimated equipment leak emissions and the reductions that would be achieved with EL Option 2 in the technology review referenced above , a HAP emissions reduction of 31 percent would be6

achieved with EL Option 2 over th at of EL Option 1. As discussed above, the maximum cancer MIR from the OSWRO source category at the MACT

- allowable emissions level including EL Option 1 is 7

- in

- 1 million, and the maximum non

- cancer TOSHI at the MACT

- allowable emissions level including EL Option 1 is 0.5. Applying the emissions reduction factor of EL Option 2 to this cancer MIR value results in a MIR of 5

- in

- 1 million (i.e., 7 *( 1

- 0. 31 ) = 5 ), a nd application of this factor to this non

- cancer TOSHI value results in a TOSHI of 0. 3 (i.e., 0. 5*(1

- 0. 31 ) = 0. 3 ).