p.1 

OAR Box 1875 

Prepped by Ollie Stewart 

Document Number: 

84) ll-F-31 

Docket Number: 

A-90-19 

Printed 12/1/200811:12:49 AM Sheet 84 of 86 
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A-90-19 

ll-F-31 

TO: Troy Hillier, OMB 

FROM: Jan Meyer, EPA 

DATE: October 23, 1992 

Attached please find the revised Section VII. A (rationale 

for Subpart G). The revised language reflects changes made to 

the process vents discussions as well as clarifying changes. We 

are still making clarifying edits to this discussion. 

The attached is being provided to give you an opportunity to 

start the review before you receive the complete, consolidated 

revised package later today. I tried repeatedly Friday evening 

and over the weekend to fax you this material. Because your fax 

machine was not on, I was not able to send this to you until now. 

You may notice some format and editorial differences between 

the attached draft and the 10/6 draft. These differences should 

be ignored and will not exist in the final version. 

Please call me at (919) 541-5254 if you have any questions 

or want to discuss the draft revisions. 

1992 
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VII. RATIONALE FOR PROVISIONS IN SUBPART G 

A. Selection of Emission Control Requirements 

The Act specifies that the EPA must select emission control 

requirements for sources being regulated under Section 112 that 

are at least as stringent as, or more stringent than, the 

emission control identified as the floor. As a result, EPA began 

the process of selecting control requirements for the HON by 

determining the floor for the sources that would be subject to 

the HON. Once the floor was established for both new and 

existing sources, EPA considered additional control for each kind 

of emission point and the source as a whole taking into 

consideration the criteria enumerated in Section 112(d) of the 

Act: cost of achieving such reductions, any non-air quality 

health and environmental impacts, and energy requirements. 

This section of the preamble describes the process EPA used 

to determine the floor for new and existing sources, the criteria 

EPA used to evaluate additional control requirements and the 

outcome of EPA's floor analysis and control selection process for 

each kind of emission point in the source. Section V of this 

preamble gives an overview of the data base used in this process 

and memoranda in the docket provide a detailed description of the 

methodology and data used to derive the floors for new and 

existing sources. 

1. Overview of the Process and Factors Considered 

For SOCMI, what distinguishes a well-controlled facility is 
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not only the type of control equipment used, but also the number 

of emission points that.are controlled. Facilities differ in the 

number, combination, and design of their chemical manufacturing 

processes; the production capacities of their processes; the 

particular chemicals manufactured; and the control equipment 

used. Consequently, although SOCMI consists of similar kinds of 

emission points and the same controls are applicable, actual 

emissions and characteristics of SOCMI facilities vary widely 

from plant site to plant site. Due to this diversity, no 

"typical" source could be identified that would be representative 

across the source category. This diversity affected the approach 

used to define the floor for existing and new sources. 

Specifically, this diversity precluded the use of mass emission 

rate as a measure of performance since a mass rate based on an 

"average" source could require no control at some sources and be 

unachievable at other sources. Therefore, it was necessary for 

EPA to combine data on control efficiencies achieved on each kind 

of emission point to develop the source-wide floor. This process 

can be expected to result in a floor determination that is at 

least as stringent as that which would have been generated with 

actual source wide data. 

The information EPA used in determining the source-wide 

floor consisted of the estimates of the number and 

characteristics of the model emission points, the emission 

control requirements expected for each emission point in the 

absence of this standard, and the expected control efficiencies 
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for the control technology. As discussed earlier in this notice, 

EPA used data on the control requirements in existing State and 

Federal regulations to identify those emission points that must 

be controlled and to identify the required controls. (The 

regulations were used as a surrogate for actual data on the 

control levels achieved in practice. In this analysis, EPA 

assumed all facilities would be in compliance with all applicable 

regulations.) The requirements in existing State and Federal 

regulations were used to estimate the controls that would be in 

place on the model emission points at the time of promulgation of 

the HON. 

In the analysis of existing regulations, EPA found that 

where State and Federal rules require controls on emission 

points, they typically require use of the most effective control 

technologies (or performance levels) that are generally 

applicable. These control technologies are the same as the 

controls required in previous NSPS standards for the SOCMI and 

are widely accepted by the industry and regulatory agencies as 

technologies appropriate as bases for emission standards. These 

control technologies have been designated as the "reference 

control technologies" for the purpose of the standard being 

proposed today. 

The reference control technologies (and their performance 

levels) specified in the proposed standard reflect information 

and knowledge of SOCMI that EPA has been developing since 1976. 

Through development of standards under Section 111 and 
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Section 112 for SOCMI, EPA has developed extensive knowledge of 

the range of demonstrated control technologies applicable to 

SOCMI and the expected performance of these technologies. The 

selected technologies identified as the basis for the reference 

control requirements are: 

98 percent combustion control for process vents and 

transfer operations. For halogenated streams, 

98 percent control is achieved using a thermal 

incinerator, boiler, or process heater, plus acid gas 

scrubbing. For nonhalogenated streams, 98 percent 

control is achieved using either a thermal incinerator, 

a flare, or a boiler or process heater. 

95 to 98 percent volatile organic HAP control of 

wastewater (for highly volatile chemicals) or control 

to a target concentration using a controlled steam 

stripper or other treatment technology. The actual 

control depends on individual chemical properties, 

approximately 95 percent control of storage tanks 

through tank modifications or application of a vapor 

recovery system and control devices. The actual 

efficiency depends on the individual chemical 

properties. 

The above control technologies and work practices were 

selected as the technological basis for the standard since EPA 

was not aware of any demonstrated control technologies and 

operations that would perform with higher efficiencies and also 
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be universally applicable to SOCMI. In many cases, application 

of the reference control technology is already required by either 

an existing State or Federal regulation. 

To determine the source-wide floor for existing sources, EPA 

next examined the supporting information to identify the 

characteristics of emission points which had at least 12 percent 

controlled by the reference control technology. This analysis 

was done for each kind of emission point. The characteristics 

used to identify groups of emission points were physical 

parameters such as flow rate, HAP concentration, and vapor 

pressure. All the identified groups of emission points 

controlled by the reference control technology were then combined 

to define the weighted average % reduction achieved by the best 

performing 12% of the sources. (Because of the assumption of a 

single control efficiency for each reference technology, the 

average of the best performing 12% is the same as the performance 

of the 12th percentile.) The results of this analysis are 

described in the next section as part of the discussion of 

specific considerations for each kind of emission point. 

A similar method was used to determine the source-wide floor 

for new sources. For each kind of emission point, the 

characteristics of the smallest emission point controlled by the 

reference control technology was identified as determining the 

best controlled. Again, the source-wide floor was determined by 

the combination of control levels for all emission points. 

Once the floors were established, EPA considered whether to 
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establish a standard that requires an emission reduction that is 

more stringent than the floor. In selecting the standard, EPA 

considered the magnitude of the reduction in HAM emissions, the 

cost and economic impacts, energy impacts, non-air quality health 

impacts, and other environmental impacts. The objective in this 

consideration is to achieve the maximum degree of emission 

reduction that does not result in unreasonable economic or other 

impacts. As with the floors, EPA determined the standard for the 

source by combining selected control levels for each kind of 

emission point. The next section presents the additional control 

levels considered for each kind of emission point and the basis 

for the selected level. 

2. Alternative Control Levels and Selection of 

Requirements 

In the selection of the proposed standard, EPA first 

considered alternative control levels for each kind of emission 

point and selected control requirements considering the overall 

impacts of the group of decisions as well as the merits of the 

individual decisions in light of the statutory criteria. In the 

first step of the process, regulatory alternatives were developed 

for each kind of emission point. These alternatives differed 

only in the number of emission points that would be controlled by 

the reference control technology. Regulatory alternatives were 

developed using information for the chemical processes that could 

be characterized sufficiently to permit assignment of model 

emission points. Approximately 97 percent of the nationwide 
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chemical production capacity is associated with these wellcharacterized processes. The emission reduction and control cost 

estimates for the regulatory alternatives are summarized in 

Tables 5 and 6. Table 5 provides the control costs and emission 

reductions associated with alternative control levels considered 

for existing sources in the source category. Table 6 presents 

the same information for the alternative control levels 

considered for new sources in the source category. The estimates 

presented in Tables 5 and 6 differ from the estimates summarized 

in Section IV of this notice because those earlier estimates 

include an extrapolation to account for processes that could not 

be modeled. 

In selection of the proposed standard, EPA considered: 

(1) the technical feasibility; (2) economic impacts and 

feasibility; (3) the magnitude of the emission reduction; (4) the 

quality of the emission and cost estimates; (5) consistency with 

previous NSPS and NESHAP standards, CTG's and other regulations; 

and (6) and other environmental and energy impacts. Based on 

consideration of these factors, EPA selected a standard that 

would ensure a significant reduction in HAP emissions from the 

SOCMI. The EPA's analysis estimates that the selected standard 

would reduce HAP emissions from the four kinds of emission points 

by 322,000 megagrams per year from existing sources and 

63,000 megagrams per year from new sources in the fifth year of 

the standard. This represents an emission reduction of about 

86 percent for existing sources (87 percent for new sources) in 
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comparison to the emissions that would have occurred without the 

standard. The total nationwide annual 
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Table 5 
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Tabl e 6 

10 
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cost associated with this emission reduction is estimated to be 

about $91 million ($280 per megagram). (As stated above, these 

estimates represent processes sufficiently well characterized to 

assign models and are lower than the national numbers presented 

in Section IV.) 

The control requirements and applicability criteria for 

storage vessels and transfer operations would also result in 

significant emission reductions, relative to the current emission 

levels for these kinds of emission points. 

a. Process vents: existing sources. The selection of a 

criterion to use in identifying the group of process vents not 

controlled with the reference control technology was based on 

consideration of the various parameters that affect emission 

rates (flow rate, HAP concentration, net heating value, and 

corrosion properties). These parameters are highly variable from 

one process to another depending on the constituents of the vent 

stream. Therefore, it is not appropriate to select any one of 

them or even any specific combination of all of them since the 

combination would be different from one process to another. A 

surrogate measure for these parameters that influence whether or 

not a vent stream is controlled and the specific control 

technology applied is cost effectiveness. Cost-effectiveness 

values can be used to reflect all possible combinations of these 

parameters and the cost of controlling streams with the reference 

control technology (98 percent efficient combustion control). 

Use of the single criterion of cost effectiveness would result in 

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a more understandable and enforceable rule. 

The procedure used to define the groups of process vents was 

to rank all process vents in the data base from highest to lowest 

cost-effectiveness of control and to determine the point where 

less than 12 percent of the vents were controlled. This analysis 

showed that the dividing line between the groups occurred at a 

cost effectiveness of $1,500/Mg. Of the process vents with cost 

effectiveness values of less than $1,500/Mg, 44 percent were 

controlled with the 98 percent efficient combustion devices. The 

group of process vents with cost effectiveness values of 

$1,500/Mg and higher had fewer than 10 percent controlled at 

baseline. Thus, all process vents with cost effectiveness of 

$1,500/Mg and higher would be considered uncontrolled in the 

determination of the source-wide floor. 

In selection of the proposed standard for existing sources, 

EPA believes that a level of emission reduction from process 

vents more stringent than the level associated with the floor is 

achievable. The EPA is proposing to require the control level in 

Option 2, which has an incremental cost-effectiveness of 

$1,800/Mg ($1635/ton) and would require control of vents that 

have cost-effectiveness values of up to $2,000/Mg ($1,814/ton). 

Although EPA is proposing this specific control level, EPA is 

requesting comment on Options 1 through 4. These options span 

the range of control for vents with TRE cost-effectiveness values 

of up to $1,500/Mg ($l,360/ton) in Option 1 (the floor component) 

to those with TRE cost-effectiveness values of up to $5,000/Mg 

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($4,540/ton) in Option 4. The EPA anticipates that in 

consideration of the final decision EPA will give more weight to 

Options 1 through 3. The Option 2 control level was selected in 

the proposed rule based on considerations specific to the SOCMI 

category and would not necessarily be appropriate for other 

source categories. Therefore, it should not be viewed as a 

precedent for decisions on other standards. The EPA recognizes 

that there are differing views regarding the appropriate criteria 

for determining the control level. Consequently, EPA is 

requesting comments on the appropriateness of particular control 

choices within the range of options described above and asks that 

commenters provide supporting rationale for their preferences. 

The EPA selected the proposed control level considering the 

emission reduction achieved by the alternative control options 

and considering the criteria enumerated in Section 112(d) of the 

Act: the cost of achieving such emission reduction; any non-air 

quality health and environmental impacts; and energy 

requirements. As a matter of general policy in decisions to 

select control levels above the floor, EPA believes that the 

cost-effectiveness of controls and a comparison of benefits, both 

quantifiable and nonquantifiable, and costs is a primary 

consideration. In any such comparison of costs and benefits, the 

uncertainties associated with the benefit and cost estimates 

should be characterized. 

In this proposed rulemaking, however, EPA's ability to do 

such a comparison was severely limited due to the limited data on 

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the characteristics of the emission sources and the complexity of 

the SOCMI category. A preliminary assessment of the benefits of 

the potential emission reductions was prepared using the 

available data. However, because of the data limitations cited 

above, EPA does not believe that the analysis provides an 

adequate basis for decisionmaking. This analysis has been placed 

in Docket A-90-19. The EPA invites comment on this analysis, its 

usefulness and defensibility, and requests the submittal of data 

on methods that could improve the analysis. The EPA will review 

any such comments arid data and will, to the extent practicable, 

evaluate their implications for the risk assessment prior to the 

final rule. Despite the difficulty of estimating quantitative 

benefits for this rulemaking, due to the complexity of the source 

category, data limitations, and timing of the rule, EPA remains 

committed to evaluating benefits as well as costs associated with 

decisions to go above the floor in future MACT standards. The 

EPA also intends to review cost-effectiveness of decisions as 

part of these future rulemakings. 

Due to this lack of a benefits assessment, EPA used 

benchmarks from previous air toxics regulatory decisions and past 

air toxics benefits studies as a surrogate measure for benefits 

considerations in the decision on the proposed control level. 

The information considered consisted of the Benzene NESHAP 

decisions ( FR ) and the Vinyl Chloride NESHAP ( 

FR ). For example, one decision that reflected consideration 

of balancing emission reductions against costs was the benzene 

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storage standard ( FR ). In that decision, the costeffectiveness of the selected option was estimated to range from 

$128/Mg to $909/Mg in 1982$ ( $160/Mg to 1,100/Mg in 1989$ ). 

Although the cost-effectiveness measures from past decisions 

were considered in selection of the proposed control level, EPA 

also considered the differences between this proposed rule and 

the earlier decisions on benzene and vinyl chloride. This rule 

applies to emissions of over 100 HAP's while the earlier rules 

only addressed cancer health effects of a single HAP (i.e., 

benzene or vinyl chloride). Because many of the 100 HAP's 

emitted from HON facilities have noncancer health effects, there 

are questions about the relevance of the past decisions to this 

proposal. 

Additional factors were considered in the selection of the 

proposed control level. These f.actors include the magnitude of 

the emission reduction, the cost of this reduction, consistency 

with past decisions, location of facilities near population 

centers, and other environmental benefits from the control. The 

consideration of these factors is summarized below. 

Existing source process vents are the single largest 

contributor of HAP emissions from the SOCMI source category. The 

additional emission reduction beyond that achieved at the floor 

that would result from the proposed control level is about 

1,600 Mg/yr, which, due to the magnitude of the baseline 

emissions, represents 0.7% of the emission reduction achieved at 

the floor. This additional control has a cost effectiveness of 

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$1,800/Mg of HAP and with a TRE equivalent to a costeffectiveness of $2,000/Mg. The cost of this additional control 

(along with the cost of the other proposed control requirements) 

is estimated to result in less than a 3% price increase for SOCMI 

chemicals. The EPA requests comments on whether the costs of the 

selected control requirements are reasonable and the basis for 

the commenters assessment of the costs. 

The EPA is requesting comment on a range of control options 

because of the uncertainties in the measure of the benefits of 

control and the uncertainties in the cost that would actually be 

experienced. Because of the conservative assumptions used to 

develop the control costs and the TRE format of the vent 

provisions, it is unlikely that any source would actually incur 

cost at the TRE level (the criterion for defining vents that must 

apply control) that is equivalent to $2,000/Mg ($1,814/ton). The 

cost analysis used in developing the supporting information for 

this standard was based on use of a dedicated control device for 

each vent. Actual costs would be lower where one device could be 

used to control emissions from several vents. The cost of 

control would also be lower in those cases where it is feasible 

to use a boiler or process heater. Finally, the provisions are 

structured using a TRE index approach. Since the standard is in 

a TRE format, many facilities may be able to use product recovery 

to change vent stream characteristics so that they are below the 

relevant applicability criteria. This flexibility is expected to 

allow some sources through changes in equipment or operations to 

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lower their cost of compliance. As a result, the impacts 

analysis may overstate the costs of complying with the proposed 

control requirement. The EPA solicits comments concerning 

whether the control costs for process vents are overestimated and 

the extent of the overestimate. 

b. Process vents: new sources. The analysis of the data 

base also showed that the maximum degree of emission reduction 

being achieved by the best-controlled vent occurs at a cost 

effectiveness value of $11,000/Mg ($9,980/ton). In the 

determination of the process vent component of the source-wide 

floor for a new source, vents with a cost effectiveness value for 

control of $11,000/Mg ($9,980/ton) would be controlled. 

For the standard for new sources, EPA considered selecting a 

level of emission reduction more stringent than the level 

associated with the source-wide floor. However, a standard more 

stringent than the floor component is not being proposed because 

the costs were considered high given the very small additional 

emission reduction available. The additional control would 

achieve an additional emission reduction of about 100 Mg/yr at a 

cost of about $5 million/yr. Therefore, the control level 

associated with the source-wide floor was considered to represent 

the maximum reduction achievable considering cost and other 

impacts. The proposed standard for new sources reflects the 

floor level of control for new vents. 

c. Storage vessels: existing sources. In the analysis of 

the data base to determine the storage vessel components of the 

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source-wide floor, EPA divided the population of model vessels 

into three size ranges. The size ranges were: 38 m3 to 75 in3 

(10,000 to 20,000 gal) (small); 75 to 151 m3 (20,000 to 

40,000 gal) (medium); and greater than or equal to 151 m3 

(40,000 gal) (large). The first two of the ranges are the two 

smallest model vessel sizes in the data base and the third range 

is the combination of the remaining four model vessel size 

ranges. The larger size range vessels were aggregated into one 

group because no differences based on vessel capacity were 

expected for the vessels exceeding 40,000 gallons capacity. Only 

one State regulation distinguishes among vessels with capacities 

greater than 151 m3 (40,000 gal) and none of the greater than 151 

m

3 (40,000 gal) storage vessels in the data base are affected by 

those requirements. Consequently, separate analysis of each of 

the larger capacity range model vessels would provide the same 

results as a combined analysis. 

The parameter used in the analysis to determine the storage 

vessel components of the source-wide floor was the vapor pressure 

of the liquid being stored. Vapor pressure is one of three major 

factors that most influence emissions from storage vessels and 

potential emission reductions. Furthermore, vapor pressure is 

commonly a prime determining factor in whether or not a vessel is 

controlled. 

For each segment of the storage vessel population, the 

procedure used to define components for the source-wide floor was 

to rank storage vessels from lowest to highest vapor pressure. 

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Next, the vapor pressure at which at least 12 percent of the 

vessels is controlled by the reference control technology was 

determined. The analysis showed that more than 12 percent of the 

medium and large vessels storing liquids with vapor pressures of 

13.1 kPa (1.9 psia) and higher are controlled with the reference 

technology. Of the vessels storing liquids with vapor pressures 

of 13.1 kPa (1.9 psia) and higher, about 30 percent of the medium 

vessels and 45 percent of the large vessels were controlled with 

the reference technology. Therefore, the storage vessel 

components of the source-wide floor are control of vessels 75 m3 

(20,000 gal) and higher that store liquids with vapor pressures 

of 13.1 kPa (1.9 psia) and higher. For small vessels, the 

analysis of the data base showed that only 6 percent of the 

vessels were expected to be controlled with the reference 

technology. Therefore, since less than 12% of the small vessels 

are controlled with the refeerence control technology the small 

vessel component of the source-wide floor is no control. 

For each of the three populations of storage vessels, EPA 

considered several alternative levels of emission limitation. 

The alternatives differed in the vapor pressures of the liquids 

that would require control and ranged from the vapor pressure 

associated with the component of the source-wide floor (i.e., 

13.1 kPa [1.9 psia]) to vapor pressures of 0.07 kPa (0.01 psia). 

After considering the alternatives and the associated impacts, 

EPA proposes to require the following storage vessels be equipped 

with the reference control technology: (1) vessels with a 

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capacity greater than or equal to 151 m3 (40,000 gal) storing 

HAP's with vapor pressures of 5.2 kPa (0.75 psia) or greater and 

(2) vessels with a capacity greater than or equal to 75 irT 

(20,000 gal) storing HAP's with vapor pressures of 13.1 kPa (1.9 

psia) and greater. No control requirements are being proposed 

for storage vessels with capacities less than 75 m3 (20,000 gal). 

In the selection of these proposed control requirements, EPA 

believes, based on the available data, that an emission reduction 

more stringent than the level associated with the floor component 

for large vessels is achievable considering the statutory 

criteria. The EPA also believes that no emission levels more 

stringent than the level associated with the floor components for 

medium and small vessels are achievable considering the statutory 

criteria. The statutory criteria considered in selection of the 

proposed control requirements were the magnitude of the emission 

reductions, the cost and economic impacts, energy impacts, nonair quality health impacts, and other environmental impacts. The 

specific considerations of the statutory factors in each of these 

decisions are summarized below. 

The proposed control requirements for large storage 

vessels containing liquids with HAP vapor pressures of 5.2 kPa 

(0.75 psia) or higher are estimated to achieve an emission 

reduction of 4,800 Mg/yr (5,280 tons/yr) of HAP's compared to 

emissions that would occur without the standard. This represents 

a 48 percent reduction of emissions from this segment of the 

SOCMI storage vessel population. The annual cost to achieve this 

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reduction is about $7.3 million and the incremental costeffectiveness of the control beyond the floor is $1,000/Mg. 

Although EPA consider controlling HAP's with vapor pressures of 

10.3 kPA (1.5 psia), it was found that this option was less 

economically efficient (i.e., higher incremental costeffectiveness) than the proposed- option. The cost-effectiveness 

of the proposed option is in the range of the cost-effectiveness 

values of the Benzene Storage NESHAP and the range of values from 

the NSPS for VOL storage (Subpart Kb of 40 CFR Part 60). 

The non-air quality health impacts as well as the energy and 

other environmental impacts of the alternative control levels 

were also considered in the selection of the proposed 

requirements for large storage vessels at existing sources. No 

non-air quality health impacts were expected from any of the 

alternatives and the energy and other environmental impacts did 

not vary significantly among the alternatives. Thus, these 

considerations did not affect the choice of the proposed 

requirements. The controls required by the proposed requirements 

are not expected to create any secondary emissions of carbon 

monoxide or nitrogen oxides. In addition, no secondary benefits 

of control of non-HAP VOC's are expected. The energy impacts 

estimated for the selected control requirements were about 

5,400,000 kW-hr/yr for electricity. The energy requirements 

associated with control of all large vessels storing HAP's of any 

vapor pressure was about 20% greater. The energy required for 

the control equipment represents a small percentage of the total 

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energy requirement for this industry. Based on previous studies 

of SOCMI, no unreasonable adverse energy impacts are expected 

from any of the alternative control levels considered. 

A more stringent level of emission reduction is not being 

proposed because the additional reduction that could be achieved 

through further control of large storage vessels was not 

considered significant, given the additional cost. The 

additional emission reduction achieved through control of HAP's 

with vapor pressures lower than 5.2 kPa (0.75 psia) is about 

4,000 Mg/yr (4,300 tons/yr). This control would cost 

$11.2 million per year. The cost-effectiveness of this 

additional emission reduction is $2,900/Mg. The cost of 

achieving this emission reduction was not considered reasonable. 

In selecting the proposed emission limitations for small and 

medium storage vessels at existing sources, EPA considered levels 

of emission reduction more stringent than the level associated 

with the source-wide floor for these emission points. The 

alternative control options considered for small vessels were: 

(1) vapor pressures of 76.6 kPa (11.1 psia) and higher; (2) 

vapor pressures of 5.2 kPa (1.9 psia) and higher; and (3) vapor 

pressures greater than 0.07 kPa (0.01 psia). The alternative 

control options beyond the floor component considered for medium 

vessels were: (1) vapor pressures of 0.7 kPa (0.1 psia) and 

higher; and (2) vapor pressures greater than 0.07 kPa (0.01 

psia). None of the alternative options for either small or 

medium vessels is being proposed since the costs were considered 

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P.25 

high given the very small potential emission reductions. Control 

beyond the floor component for medium storage vessels would 

reduce emissions by less than 100 Mg/yr (110 tons/yr) at a cost 

of $3.6 million/yr. With small storage vessels the maximum 

potential reduction of 360 Mg/yr would cost about $19 million/yr. 

The average cost effectiveness of these control requirements 

varied from $53,000/Mg ($48,000/ton) for small vessels to about 

$14,000/Mg ($12,700/ton) for medium vessels. Therefore, EPA 

believes that the control level for the small and medium storage 

vessels components of the source-wide floor represented the 

maximum reduction achievable considering cost and other impacts. 

The EPA is proposing to require control of medium storage vessels 

storing HAP's with vapor pressures of 5.2 kPa (1.9 psia) and 

higher. No control requirements are being proposed for small 

storage vessels. For both small and medium storage vessels, this 

proposal requires no control beyond the respective components of 

the source-wide floor. 

An additional consideration in the selection of the proposed 

options was the non-air quality health impacts as well as the 

energy and other environmental impacts of the alternative control 

levels. No non-air quality health impacts were expected from any 

of the alternatives and the other environmental impacts did not 

vary significantly among the alternatives. Thus, these 

considerations did not affect the choice of the proposed 

requirements. The co-controls required by the proposed 

requirements are not expected to create any secondary emissions 

23 
P.26 

of carbon monoxide or nitrogen oxides. In addition, no secondary 

benefits of co-control of non-HAP VOC's are expected. The energy 

impacts for the required controls for medium storage vessels 

would be about 2,600,000 kW-hr/yr for electricity. The energy 

requirements associated with control of medium storage vessels 

containing liquid HAP's of any vapor pressure is slightly 

greater, but is not considered significant. The energy required 

for the control equipment represents a small percentage of the 

total energy requirement for this industry. Based on previous 

studies of SOCMI, no unreasonable adverse energy impacts are 

expected from any of the alternative control levels considered. 

d. Storage vessels: new sources. The determination of the 

best controlled storage vessels also used the three size ranges 

of model vessels. For the reasons previously described, the 

parameter used in the analysis to determine the storage vessel 

components of the source-wide floor was the vapor pressure of the 

liquid being stored. 

The analysis of the data base showed that the maximum degree 

of emission limitation being achieved by the best-controlled 

vessels in each population segment occurs at 13.1 kPa (1.9 psia) 

for small and medium vessels and at 5.2 kPa (0.75 psia) for large 

vessels. For each of the three segments of the storage vessel 

population, EPA considered several alternative levels of emission 

limitation more stringent than the emission level associated with 

the floor component. The alternatives were structured similarly 

to those for existing storage vessels but differed in the vapor 

1 24 
P.27 

pressures of the liquids that would be required to apply 

controls. The alternative control options examined for storage 

vessels at new sources were: (1) for large and medium vessels, 

vapor pressures 0.7 kPa (0.1 psia) and greater and vapor 

pressures of 0.07 kPa (0.01 psia) and greater; and (2) for small 

vessels, vapor pressures of 0.07 kPa (0.01 psia). 

The EPA is proposing to control large storage vessels that 

store HAP's with vapor pressures of 0.7 kPa (0.1 psia) and 

higher. This proposed control will result in a significant 

emission reduction at a reasonable cost. The proposed control 

requirement for large storage vessels is estimated to achieve an 

emission reduction of 1,100 Mg/yr (1,200 tons/yr) of HAP's 

compared to emissions that would occur without the standard. 

This represents an 87 percent reduction from this segment of the 

SOCMI storage vessel population. The annual cost to achieve this 

reduction is about $0.8 million and the cost-effectiveness of 

this control is $735/Mg ($670/ton). 

The non-air quality health impacts were considered in this 

decision as well as the energy and other environmental impacts of 

the alternative control levels. As with the other decisions, 

these factors did not vary significantly among the alternatives. 

Thus, these considerations did not affect the choice of the 

proposed requirements. The energy required for control beyond 

the floor component would be about 200,000 kW-hr/yr for 

electricity. 

The EPA is not proposing to require control of vapor 

25 
P.28 

pressures greater than 0.7 kPa (0.1 psia) because the additional 

emission reduction achieved through further control was not 

significant, given the additional cost. Further control was 

estimated to result in only 2 Mg/yr additional reduction at an 

additional cost of $233,000/yr. This cost was judged to be 

disproportionately high. 

For small and medium vessels, none of the alternative 

control options more stringent than the floor components were 

selected. After considering the emission reductions, costs, and 

other impacts of the alternatives, EPA determined the cost to 

achieve the additional reduction was high given the very small 

potential emission reductions. Additional control would reduce 

emissions from medium storage vessels by less than 20 Mg/yr (22 

tons/yr) at an additional cost of about $700,000/yr. For the 

small storage vessels segment of the population, further control 

would result in less than 10 Mg/yr (11 tons/yr) emission 

reduction at an added cost of about $2.1 million/yr. The 

incremental cost effectiveness values for these control 

requirements are about $304,000/Mg ($276,000/ton) fro small 

vessels and $42,000/Mg ($38,100/ton) for medium vessels. The 

consideration of the non-air quality health impacts as well as 

the energy requirements and other environmental impacts was 

similar to that in the decision for existing storage vessels. 

Therefore, EPA determined that the control level for the small 

and medium storage vessels components of the source wide floor 

represented the maximum reduction achievable considering cost and 

26 
P.29 

other impacts. 

e. Transfer operations: existing sources. In the analysis 

of the data base to determine the transfer rack components of the 

source wide floor, EPA divided the population of model racks into 

two groups based on the vapor pressure of materials loaded. The 

vapor pressure groupings were transfer racks loading materials 

with average vapor pressures less than 10.3 kPa (1.5 psia) and 

racks loading materials with vapor pressures of 10.3 kPa 

(1.5 psia) and higher. These two groups are the result of 

several simplifying assumptions used in the analysis and the fact 

that most State regulations only require control of racks loading 

chemicals with vapor pressures of 10.3 kPa (1.5 psia) and higher. 

The procedure used to determine the transfer rack components 

of the source-wide floor was to rank the racks by quantity loaded 

(throughput) in ascending order. Since emissions from transfer 

operations are largely determined by throughput and vapor 

pressure, throughput was expected to provide a good measure of 

whether or not a rack is controlled. For both groups, the 

throughput at which more than 12 percent of the racks is 

controlled by the reference control technology was determined. 

The analysis showed that for transfer racks that load HAP's with 

vapor pressures of 10.3 kPa (1.5 psia), and higher, that have 

throughputs greater than 64 3.5 m3/yr (170,000 gal/yr) more than 

12% of the racks are controlled with the reference technology. 

None of the transfer racks that load HAP's with vapor pressures 

less than 10.3 kPa (1.5 psia) were controlled with the reference 

27 
P.30 

technology. 

Only two levels of emission limitation were evaluated and 

considered in the selection of the proposed control requirements. 

These alternatives were the emission level associated with the 

transfer.rack component of the source-wide floor and the level 

associated with control of all transfer racks. To simplify the 

consideration of control alternatives, the emissions and cost 

information for the two groups of racks were combined. After 

considering the emission reductions, costs, and other impacts of 

the alternatives, EPA believes that the level of emission 

limitation associated with the component of the source-wide floor 

is achievable. The more stringent level of emission reduction is 

not being proposed because the additional emission reduction 

achieved is not significant and the cost of this reduction is 

high. Control beyond the level associated with the source-wide 

floor would reduce emissions from transfer racks by less than 

70 Mg/yr (77 tons/yr) at a cost of $3.4 million/yr. The average 

cost effectiveness of this control is $50,000/Mg ($45,400/ton). 

As with the decisions on the other emission points, no non-air 

quality health impacts were expected from any of the alternatives 

and the other environmental impacts did not vary significantly 

among the alternatives. Thus, these considerations did not 

affect the choice of the proposed requirements. The controls 

required by the proposed requirements are not expected to create 

any significant secondary emissions of carbon monoxide or 

nitrogen oxides. In addition, no secondary benefits of co28 
P.31 

control of non-HAP VOC's are expected. The energy impacts for 

the required controls are also not believed to be significant. 

f. Transfer operations: new sources. The analysis of the 

data base showed that the maximum degree of emission reduction 

being achieved by the best controlled transfer rack occurs at 

vapor pressures of 10.3 kPa (1.5 psia) and throughputs greater 

than 643.5 m3/yr (0.17 million gal/yr). Thus, for new sources 

the transfer rack component of the source wide floor is identical 

to that for existing sources. 

The decision on the control requirements considered the same 

two levels of emission limitation that were considered for 

transfer racks at existing sources. For the same reasons 

discussed earlier, EPA is not proposing to require a more 

stringent level of emission reduction. After considering 

emission reductions and other information, EPA believes that the 

level of emission limitation associated with the component of the 

source-wide floor is achievable. 

g. Process wastewater: existing sources. The parameters 

used in the analysis of the data base to identify the floor level 

of control for wastewater streams were: concentration of 

chemicals with high volatility in wastewater (e.g., benzene or 

vinyl chloride); concentration of chemicals with lower 

volatilities than benzene, or semi-volatile HAP's; and flow rate. 

These parameters were used because they are among the primary 

factors that most influence air emissions from wastewater 

streams. 

29 
P.32 

As previously noted, EPA used data on the control 

requirements in existing State and Federal regulations to 

identify streams that must be controlled and to identify the 

required controls. The only controlled wastewater streams in the 

data base were those estimated to meet the applicability 

requirements of either the Vinyl Chloride NESHAP, 40 CFR Part 61 

Subpart F, or the Benzene Waste Operations NESHAP, 40 CFR Part 61 

Subpart FF. There are no State regulations requiring control of 

air emissions from wastewater. Consequently, the procedure used 

in the analysis of the existing control level for wastewater 

operations was to determine the proportion of processes and 

wastewater streams that have concentrations above the control 

criteria in the Benzene Waste NESHAP or Vinyl Chloride NESHAP 

(greater than 10 ppm benzene or vinyl chloride compared to the 

total number of processes and wastewater streams. The estimate 

of the number of processes and benzene containing wastewater 

streams subject to the Benzene Waste NESHAP was adjusted by the 

expected proportion of the facilities exceeding the facility-wide 

threshold for control. This analysis showed that fewer than 

5 percent of SOCMI processes and fewer than 3 percent of the 

wastewater streams are currently controlled to the efficiency of 

the reference control technology. Therefore, since less than 

12 percent of existing wastewater streams are controlled, the 

component of the source-wide floor for existing wastewater 

streams is estimated to be no control. 

The EPA considered alternative levels of emission reduction 

30 
P.33 

that varied from controlling those process wastewater streams 

that are larger and more cost effective to control to controlling 

all wastewater streams. The EPA is proposing to require control 

of process wastewater streams with greater than 10 liters per 

minute flow rate and greater than 1000 ppmw total VOHAP 

concentration. The proposed control level was selected 

considering the emission reductions of the alternative control 

options and the criteria enumerated in Section 112(d) of the Act. 

The proposed alternative is considered to achieve the maximum 

emission limitation that is achievable considering cost, non-air 

quality health and environmental impacts, and energy 

requirements. Although EPA is proposing this specific option, 

commenters should be aware that there are a number of technical 

issues regarding the emission and cost estimation methodologies. 

(These issues are discussed in Section VII.E.3 of this notice.) 

The EPA anticipates that for wastewater controls there may be 

changes in the emission and cost estimates that result from the 

resolution of the technical and science issues and any new 

information received during the public comment period. The final 

rule will be based on consideration of the revised estimates. 

The considerations of the currently available information on the 

alternative control options are summarized below. 

Wastewater streams at existing sources are believed to be 

the second largest contributor of HAP emissions from the emission 

points regulated by the HON. The proposed control requirements 

are expected to achieve an emission reduction of 82,100 Mg/yr 

31 
P.34 

(90,300 tons/yr) of HAP's compared to current emission levels. 

This represents a 77 percent reduction from the uncontrolled 

emission rate. The annual cost to achieve this reduction is 

$23.9 million. The cost-effectiveness of going from no control 

to the proposed control is $290/Mg ($265/ton). 

The estimated costs of the proposed wastewater control 

requirements are based on use of steam strippers to control the 

wastewater stream and do not reflect any potential cost savings 

from use of the other means of demonstrating compliance that are 

provided in the wastewater provisions. One of these compliance 

options allows a source to demonstrate compliance through use of 

pollution prevention measures and waste treatment to change the 

wastewater stream characteristics. This compliance option is 

expected to lower the cost of compliance for some sources. Thus, 

EPA believes that the cost analysis may overstate the cost of 

complying with the proposed wastewater provisions. Industry 

representatives have indicated that they believe the cost 

estimates to be understated. The EPA requests comments on 

whether the costs of the proposed control requirements are 

reasonable and asks that commenters provide supporting 

information for their estimates. 

The non-air quality health impacts as well as the energy and 

other environmental impacts of the alternative control levels 

were also considered in the selection of the proposed 

requirements. No non-air quality health impacts were expected 

from any of the alternatives and the energy and other 

32 
P.35 

environmental impacts did not vary significantly among the 

alternatives. Thus, these considerations did not affect the 

choice of the proposed requirements. The energy impacts 

estimated for the selected control requirements were about 

4,500,000 kW-hr/yr for electricity and 4,200,000 million Btu/yr 

for steam. The energy required for the most stringent control 

level was only slightly greater for electricity and steam. These 

energy requirements represent a small percentage of the total 

energy requirement for this industry. Based on previous studies 

of SOCMI, no unreasonable adverse energy impacts are expected 

from any of the alternative control levels considered. 

While EPA could not quantify the non-air quality benefits, 

EPA considers control of wastewater streams to result in non-air 

quality benefits. These benefits include generation of less 

hazardous waste, less groundwater contamination, and less 

contamination of stormwater. Another secondary non-air quality 

benefit considered in the selection of the proposed alternative 

is that SOCMI wastewater streams also can contain non-HAP VOC's. 

These non-HAP VOC's will be controlled when streams are 

controlled for HAP emissions. This co-control is expected to 

significantly reduce emissions of non-HAP VOC's, thereby 

contributing to efforts to reduce tropospheric ozone. 

Alternative control Options 2 through 5 were not selected 

because the additional emission reduction achieved through 

further control was not significant, given the costs and the 

uncertainty regarding the characterization of SOCMI wastewater 

33 
P.36 

systems. Specifically, control of wastewater streams with flows 

of 5 liters per minute or greater and concentrations of 500 ppmw 

VOHAP (Option 2) was estimated to result in about 700 Mg/yr 

additional reduction at a cost of about $1.8 million/yr. This 

control option has a cost-effectiveness value of $2,600/Mg. 

Options 3 through 5 achieve only a small additional emission 

reduction at cost-effectiveness values of $3,000/Mg to 

$15,000/Mg. Given the technical uncertainties that exist 

regarding the representation of SOCMI wastewater streams and 

industry practices in design of wastewater collection and 

treatment systems, it is uncertain whether any of the alternative 

control options considered would result in additional emission 

reductions. Therefore, EPA is not proposing any options more 

stringent than Option 1. 

h. Process wastewater: new sources. The analysis of the 

data base also showed the maximum emission reduction being 

achieved is determined by the control requirements for the 

Benzene Waste Operations NESHAP and the Vinyl Chloride NESHAP. 

Under these rules, wastewater streams with 10 ppmw or greater and 

flow rates greater than 0.02 liters per minute have to be treated 

prior to discharge and units in which waste is managed before 

treatment must be equipped with 95 percent efficient air emission 

controls. This emission limitation was assumed to be equally 

applicable to other chemicals that have volatilities in water 

equal to or greater than benzene and vinyl chloride. These 

chemicals, which are termed WHAP, are listed in Table 8 of 

34 
P.37 

proposed Subpart G. As previously noted, there are no State or 

Federal regulations that would require control of chemicals other 

than benzene or vinyl chloride. Therefore, there is no control 

at the floor for chemicals with volatilities lower than that of 

benzene or vinyl chloride. In the determination of the sourcewide floor component for new sources, wastewater streams 

containing 10 ppmw, or more, of WHAP would be required to be 

controlled to the efficiency of the reference technology and 

chemicals with lower volatilities would not. 

The EPA developed alternative control options for process 

wastewater streams at new sources by first considering whether to 

require control beyond the floor component for WHAP containing 

streams and then considering control options for lower volatility 

chemicals (i.e., VOHAP) in wastewater streams. No alternatives 

were developed for further control of WHAP since the potential 

additional emission reduction for WHAP was minimal. For the 

less volatile chemicals, EPA examined several alternative 

options. Alternatives considered included control of streams 

with total VOHAP concentrations of 800, 500, 200, and 5 ppmw. 

Table 6 shows the emission reductions and costs associated with 

the floor control for WHAP combined with the emission reduction 

and costs for control of total VOHAP concentrations of either 800 

ppmw (Option 2) or 5 ppmw (Option 3). After considering the 

alternatives and the associated impacts, EPA is proposing the 

control requirements in Option 2. The proposed control 

requirements for new source wastewater streams would apply to 3 

35 
P.38 

sets streams: streams with flow rates of 0.02 £pm or greater and 

concentrations of 10 ppmw or greater of WHAP (as defined in 

Table 8 in Section 63.132 of Subpart G); streams with flow rates 

of 10 £pm or greater and concentrations of 1000 ppmw or greater 

of VOHAP (as defined in Table 9 of Section 63.138 of Subpart G); 

and all streams with concentrations of 10,000 ppmw or greater of 

VOHAP. The proposed control level was selected considering the 

emission reduction achieved by the alternative control options 

for VOHAP emissions and considering the criteria enumerated in 

Section 112(d) of the Act. The proposed alternative is 

considered to achieve the maximum emission reduction considering 

the cost, nonair quality health effects, environmental impacts, 

and energy requirements. The considerations of these factors and 

the uncertainties in the estimates are described below. 

The proposed control requirements are estimated to achieve a 

reduction of 14,500 Mg/yr (16,000 tons/yr) of WHAP and VOHAP 

compared to emissions in absence of this rule. As with the 

requirements for existing sources, this represents an 77 percent 

reduction from uncontrolled emission rates for wastewater. The 

annual cost to achieve this reduction is about $6.9 million. As 

noted in the discussion of the proposed control for existing 

wastewater streams, there is uncertainty whether the costs are 

understated or overstated. 

Option 2 is estimated to achieve an emissions reduction of 

about 1,500 Mg/yr (1650 tons/yr) of VOHAP emissions above the 

floor. This control would cost about $1.5 million/yr and have a 

36 
P.39 

cost-effectiveness value of $1000/Mg ($910/ton). 

In selecting Option 2 for the proposed control requirements, 

EPA also considered the non-air quality health effects as well as 

the energy requirements and other environmental impacts. The 

consideration of these criteria was similar to that in the 

selection of controls for existing wastewater streams. No nonair quality health impacts were expected from any of the 

alternatives. In comparing the alternatives, EPA found that the 

environmental and energy impacts did not vary significantly among 

the alternatives. The energy and secondary impacts from the 

control devices were not considered significant. 

The proposed control requirements are expected to have 

secondary non-air quality benefits such as reduced potential for 

groundwater contamination. The selected alternative is estimated 

to result in control of about 30 percent of the total wastewater 

volume from new SOCMI sources. 

The EPA is not proposing a more stringent level of emission 

limitation because control beyond the selected level is estimated 

to achieve only a small additional emission reduction. The 

further control would reduce emissions by an additional 1,400 

Mg/yr (1,500 tons/yr) of VOHAP. This control would cost about 

$23 million per year, an increase of about $16 million per year 

over the cost of the proposed control level. Because the cost is 

disproportionately large compared to this additional emission 

reduction and the great uncertainties regarding the potential 

emission reduction, EPA is not proposing the more stringent 

37 
P.40 

control option. 

38