FROM: David Randall, RTI International

TO: Nick Parsons, EPA/OAQPS

FOR: EPA Docket No. EPA-HQ-OAR-2010-0871

DATE: January 20, 2012

SUBJECT: Survey of Control Technology for Storage Vessels and Analysis of Impacts for 

Storage Vessel Control Options

1. Purpose

This memorandum documents the survey of control technologies for storage vessels. It reviews 

control alternatives and estimates the costs and environmental impacts for the alternatives 

identified. Monitoring, recordkeeping, and reporting burden and costs are also estimated.

2. Legislative Background

The Clean Air Act (CAA) requires EPA to review promulgated standards periodically to ensure 

that new source performance standards (NSPS) and national emissions standards for hazardous 

air pollutants (NESHAP) reflect advances in emissions reduction technology. Specifically, 

Section 112(d)(6) of the Clean Air Act (CAA) states that “[t]he Administrator shall review, and 

revise as necessary (taking into account developments in practices, processes, and control 

technologies), emission standards promulgated under this section no less often than every 8 

years.” Similarly, Section 111(b)(1)(B) requires EPA to review NSPS for a given source 

category every 8 years, and, if appropriate, revise such standards. To facilitate these required 

reviews, EPA is evaluating key emission sources that exist across several source categories to 

provide a consistent framework when evaluating the emissions from these key sources for a 

particular source category. This memorandum documents the technology review for storage 

vessels.

3. Introduction

Storage vessels are used to store liquid and gaseous feedstocks for use in a process and liquid 

and gaseous products from a process. Most storage vessels are designed for operation at 

atmospheric or near atmospheric pressures; high pressure vessels are used to store compressed 

gases and liquefied gases. Atmospheric storage vessels are typically cylindrical with a vertical 

orientation, and they are constructed with either a fixed roof or a floating roof. Some, generally 

small, atmospheric storage vessels are oriented horizontally. High pressure vessels are either 

spherical or horizontal cylinders. All of the storage vessels in this analysis are aboveground 

storage vessels; underground storage tanks are not considered.

4. Description of Emission Releases

Emissions from Fixed Roof Storage Vessels 

Emissions from fixed roof storage vessels (both vertical and horizontal vessels) occur from 

working losses, breathing loses, and leaks. Working losses are the combined emissions from 
Technical Memorandum – Technology Review for Storage Vessels

January 20, 2012

2

filling and emptying the storage vessel. Emissions during filling operations result from an 

increase in the liquid level in the storage vessel. As the liquid level increases, the pressure inside 

the tank exceeds the relief pressure and vapors are expelled from the storage vessel. Emissions 

also occur as a result of withdrawing liquid from the storage vessel because some of the stored 

liquid evaporates to partially saturate the air that is drawn in as the liquid is withdrawn. This 

increase in the amount of vapor causes the pressure to increase; as when filling the storage 

vessel, when the pressure exceeds the relief pressure, the vent opens and vapors are released to 

the atmosphere. Factors that affect the mass of working losses include the saturation level of the 

pollutant in the vapor space, vapor pressure of the stored material, vapor molecular weight, total 

throughput, and capacity of the storage vessel.

Breathing (or standing) losses are emissions caused by vapor expansion and contraction, which 

are the result of changes in temperature and barometric pressure. These emissions occur without 

any changes in the liquid level in the storage vessel. Factors that affect the mass of breathing 

losses are the vapor pressure of the stored material, atmospheric conditions (e.g., daily total solar 

insolation and daily range of ambient temperatures), breather vent pressure and vacuum settings, 

vessel dimensions, and vapor molecular weight. If the stored liquid is maintained at a constant 

temperature, breathing emissions are minimized or eliminated.

Another potential source of emissions from storage vessels is leaks from various improperly 

closed openings such as defective pressure/vacuum vents and poorly fitting or deteriorated 

gaskets used to seal closure devices for openings such as access hatches. Procedures for 

estimating such emissions are not available. However, factors that affect the mass of these 

emissions are the size and number of openings, the vapor pressure of the stored material, and

atmospheric conditions such as wind. Some of the breathing and working emissions may also 

occur through the leak openings rather than the intended vent.

Emissions from Floating Roof Storage Vessels

During normal operations, a floating roof is floating on the liquid in the storage vessel. 

Emissions during normal operations occur due to withdrawal losses, rim seal losses, and deck 

fitting losses. In addition, deck seam losses are a source of emissions from internal floating roofs 

(IFRs) with bolted decks. When the storage vessel is emptied to the point that the floating roof is 

landed on its supports, emissions also occur due to standing idle losses and filling losses.

Withdrawal losses occur as the liquid level and floating roof are lowered. Some liquid remains 

on the inner wall of the storage vessel and evaporates. Similarly, liquid that remains on the 

surface of fixed roof support columns in IFR storage vessels will also evaporate. The mass of 

these emissions is a function of the surface area-to-volume ratio of the storage vessel, the 

roughness of the wall (which affects the amount of liquid that can cling to the wall after the 

liquid level drops), the total throughput, and the density of the stored liquid.

Rim seal losses are emissions that escape through gaps between the rim seal and the inner wall of 

the storage vessel. The primary mechanism generating rim seal emissions is the wind and thus, 

rim seal losses for external floating roofs (EFRs) are greater than for IFRs. For average fitting 

seals, an empirical relationship has been developed that estimates the emissions as a function of 

the type of rim seal system (type and number of seals), storage vessel construction (riveted or 

welded), vapor pressure of the stored liquid, average wind speed, and vapor molecular weight 

(U.S. EPA, 1995a).
Technical Memorandum – Technology Review for Storage Vessels

January 20, 2012

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Numerous fittings pass through or are attached to floating roof decks to accommodate structural 

support components or to allow for operational functions. Typical deck fittings include access 

hatches, gauge floats, gauge-hatch/sample ports, rim vents, deck drains, deck legs, vacuum 

breakers, and guidepoles. Storage vessels with IFRs may also have fixed-roof support columns, 

ladders, and stub drains. Empirical relationships have been developed to estimate emissions from 

these deck fittings; these relationships express emissions as a function of the number of each 

type of fitting, fitting design (e.g., type of cover, wiper, gasket, or other features to minimize 

openings), vapor pressure of the stored material, and vapor molecular weight (U.S. EPA, 1995a). 

Internal floating roofs with a deck formed from panels bolted together also have emissions 

through the seams between the panels. These emissions are estimated as a function of the total 

length of seams, an average emission factor per unit length of seam, the vapor pressure of the 

stored material, and the vapor molecular weight.

After a floating roof is landed on its supports, each vacuum breaker is open (if the device is 

activated when the leg extension associated with the vacuum breaker contacts the floor of the 

storage vessel). These openings provide a pathway for outside air to circulate through the vapor 

space under the landed floating roof and for pollutant vapors to escape. Rim seal gaps and other 

non-vapor tight deck fittings provide additional pathways for circulation. The three mechanisms 

that contribute to standing idle losses are: (1) breathing losses from the vapor space; (2) wind 

losses; and (3) clingage losses. The primary factors affecting the amount of emissions are the 

amount of time the roof is landed, the size of the vapor space, and whether there is a liquid heel.

Additional emissions are generated when the storage vessel is refilled to the point of refloating 

the floating roof. These emissions occur as the vapor is displaced through the vacuum vents and 

other openings as it is replaced with liquid. The quantity of emissions depends on the saturation 

level in the vapor space. The saturation level for a vessel with a liquid heel is greater than for a 

drain dry tank. Wind effects cause the saturation level for a storage vessel with an EFR to be 

lower than for a storage vessel with an IFR.

Emissions from Pressure Vessels 

Low-pressure tanks (2.5 to 15 psig) have working losses just like fixed roof tanks, but breathing 

losses generally are prevented. High-pressure tanks are considered closed systems and, if 

properly maintained and operated, should have virtually no emissions; there may be low levels of 

fugitive emissions, and vessels storing liquefied gases may be vented periodically to purge inerts.

Emissions from Degassing Storage Vessels 

All storage vessels must occasionally be shut down for cleaning, maintenance, inspections, or 

other reasons. If facility personnel need to enter the storage vessel, or residual liquid needs to be 

removed before refilling with a different material, or the storage vessel is to be taken out of 

service, the storage vessel first may be degassed. Degassing means the process of removing 

stored material vapors from the storage vessel. Historically, these vapors have been vented to the 

atmosphere. The mass of emissions will vary depending on the size of the vapor space, the vapor 

pressure of the stored liquid, the amount of residual liquid in the storage vessel, the degree of 

saturation in the vapor space when degassing begins, and the vapor molecular weight.
Technical Memorandum – Technology Review for Storage Vessels

January 20, 2012

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5. Identification of Control Technologies

Fixed roof storage vessels

Working and breathing losses from fixed roof storage vessels can be controlled by: (1) installing 

an IFR; (2) routing displaced vapors through a closed vent system to a control device; (3) vapor 

balancing back to the transport vehicle that supplies the liquid being added to the storage vessel; 

or (4) replacing the fixed roof storage vessel with a storage vessel that has an EFR. Leaks from 

fittings on the fixed roof (e.g., conservation vents, access hatches, and emergency pressure relief 

devices) are another source of emissions. Leaks can be controlled by periodic monitoring for 

leaks and repair of fittings that are found to be leaking. Table 1 summarizes the four control 

options that we developed and evaluated in the impacts analysis. These options are based on 

variations in IFRs and monitoring for leaks. The closed vent system to control device and vapor 

balancing approaches generally achieve control levels comparable to, or marginally better than, a 

well controlled IFR (at least for storage vessels that store materials with higher vapor pressures). 

However, a closed vent system and control device is more costly than an IFR (U.S. EPA, 1980; 

U.S. EPA, 1984; Randall and Fields, 2000), and vapor balancing may not be feasible for storage 

vessels that are designed to operate at pressures less than 2.5 psig, which is the required set 

pressure for pressure relief devices under vapor balancing options in current rules; thus, these 

techniques are not evaluated as separate control options in this analysis. We also did not develop 

a control option based on the use of an EFR because a storage vessel with a fixed roof is 

generally used for material with a lower vapor pressure than storage vessels with an EFR. 

Furthermore, the cost to construct a new tank and EFR is expected to be more than the cost to 

install an IFR in an existing fixed roof storage vessel. Thus, we expect facilities generally would 

not elect to make such a switch. 

Table 1. Summary of control options for fixed roof storage vessels

Control 

Option Technology or work practice Comments

ST1 IFR with single rim seal and typical deck fittings See Table 4 for a list of the typical deck 

fittings and their typical control

ST2 IFR with single rim seal and deck fittings 

controlled as required by current rules such as 40 

CFR part 63, subpart WW

See Table 4 for the more effective deck 

fitting control designs

ST3 Slotted ladder leg controls consisting of a 

gasketed deck cover, cap on top of the slotted 

leg, a ladder sleeve, and pole wipers 

ST4 Annual leak detection monitoring of fittings on 

fixed roof using either EPA Method 21 or optical 

gas imaging, and repair if leak is detected

Leak defined as instrument reading 

greater than 500 ppmv (Method 21) or an 

image of emissions (optical gas imaging)

Control Options ST1 and ST2 are based on the use of an IFR. Different levels of control are 

possible depending on the type of technology used to control deck fittings. Control Option ST1 

consists of an IFR with a single rim seal and typical deck fitting controls. Control Option ST2 

consists of an IFR with the same rim seal as in Control Option ST1 and more effective deck 

fittings controls such as those required in 40 CFR part 63, subpart WW. See section 6 of this 

memorandum for details regarding the typical and upgraded fittings under Control Options ST1 

and ST2.
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January 20, 2012

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We also evaluated impacts for two narrowly targeted control options. First, slotted ladder legs 

that are used for gauging liquid levels are one type of deck fitting that has not been clearly 

addressed in existing rules. Emissions from such ladders can be controlled using a gasketed deck 

cover, a cap on the top of the ladder leg, and either a flexible enclosure or various combinations 

of a ladder sleeve, pole wipers, and/or pole float that eliminate the vapor emission pathway from 

inside the storage vessel through the ladder slots to air above the floating roof. In this analysis, 

Control Option ST3 is based on the use of a ladder sleeve and pole wiper, which is comparable 

to one of the options for slotted guidepoles in 40 CFR part 63, subpart WW. This control option 

can be viewed as an extension of either Control Option ST1 or ST2 (both control options assume 

ladder legs are solid). Second, EPA inspectors have conducted instrument-based monitoring of 

fittings on fixed roofs (i.e., using optical gas imaging) and identified leaks that were not detected 

when conducting visual inspections (Parsons, 2012). Thus, we developed Control Option ST4 to 

evaluate the impacts of conducting instrument-based monitoring of fittings on fixed roof storage 

vessels that are not subject to other controls.

Storage vessels with external floating roofs

Adding an EFR can be a control technique for an open vessel. However, in this analysis we 

assumed that there are no open-top vessels storing volatile organic materials and that an external 

floating roof with one rim seal and typical deck fittings is baseline. Table 2 summarizes the three 

control options that we developed for evaluation in the impacts analysis. Control Option ST5 

consists of adding a second rim seal, Control Option ST6 consists of upgrading the deck fitting 

controls to be consistent with the requirements in current rules such as 40 CFR part 63, subpart 

WW, and Control Option ST7 consists of installing a geodesic dome over a storage vessel that is 

meeting the requirements of Control Option ST6. See Table 6 for the typical and more effective 

deck fitting controls.

Table 2. Summary of control options for EFR storage vessels

Control option Technology and work practices Comments

ST5 Add a second rim seal Baseline is one rim seal and 

typical deck fittings

ST6 Upgrade a storage vessel that meets the criteria of 

Control Option ST5 to more effective deck fittings 

controls consistent with requirements in current 

rules such as 40 CFR part 63, subpart WW

ST7 Install a geodesic dome over a storage vessel that 

meets the criteria of Control Option ST6

Pressure vessels

No control options apply for pressure vessels because pressure vessels are defined as closed 

systems that do not vent when properly operated and maintained.

Degassing 

Degassing emissions can be controlled by drawing vapors from the storage vessel (below the 

floating roof, if so equipped) to a control device. State and local rules that require degassing 

controls require operation of the control system until the concentration in the storage vessel 
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January 20, 2012

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drops below a threshold level, which varies among the rules. For example, Texas requires vapors 

to be routed to a control device until the VOC concentration is less than 34,000 ppmv expressed 

as methane (or less than 50 percent of the lower explosive limit), and the South Coast Air 

Quality Management District (SCAQMD) requires control until the concentration is less than 

5,000 ppmv expressed as methane. The required performance of the control devices also varies 

among existing rules. For example, Texas requires the control device to maintain a control 

efficiency of at least 90 percent, and the SCAQMD requires control devices to reduce emissions 

to an outlet concentration less than 500 ppmv (TCEQ; SCAQMD, 2008a). Typically, facilities 

control degassing emissions by routing vapors to a mobile control device that is owned and 

operated by an outside contractor. Mobile control systems that have been used include thermal 

oxidizers, refrigerated condensers, and internal combustion engines. Some facilities have 

installed closed vent systems to convey degassing emissions (as well as breathing and working 

losses) to permanent onsite control devices such as flares and thermal oxidizers (Moore, 2009). 

We developed one control option for evaluation in this analysis. Control Option ST8 consists of 

routing emissions to a mobile thermal oxidizer (operated by a contract service provider) until the 

concentration of organic compounds in the storage vessel are reduced to less than 5,000 ppmv as 

methane.

6. Model Development 

Fixed Roof Storage Vessels and Internal Floating Roofs 

The impacts of Control Options ST1 and ST2 for fixed roof storage vessels were developed 

using three model storage vessels with the characteristics presented in Table 3. A majority of 

fixed roof storage vessels that store organic chemicals are smaller than Model C (U.S. EPA, 

1980; Randall and Fields, 2000). Some fixed roof storage vessels are several times larger, but the 

impacts for model C are such that they adequately represent the impacts for larger storage 

vessels. Model A was selected because it represents the smallest practical size for control with an 

internal floating roof. For each model, the diameter-to-height (D/H) ratio was assumed to be 

about 1:1, as in previous analyses (U.S. EPA, 1980; U.S. EPA, 1994). The typical throughput 

was developed based on a survey of turnovers for different sized storage vessels at chemical 

manufacturing facilities (U.S. EPA, 1980). Each model storage vessel was evaluated with a 

variety of stored materials representing a wide range of vapor pressures because the total 

emissions are a strong function of the vapor pressure.

Table 3. Model fixed roof storage vessels

Parameter Model storage vessel characteristics

Model A B C

Capacity, gal 20,000 40,000 200,000

Height, ft 15 19 33

Diameter, ft 15 19 32

Throughput, gal/yr 4,700,000 5,600,000 10,000,000

Vapor pressure of stored material, 

psia at 25°C1

Varied Varied Varied

1

Vapor pressures varied from less than 0.1 psia to more than 8 psia (see Table 8).

The IFRs for the model storage vessels were assumed to have typical fittings and a typical 

number of fittings as presented in AP-42 chapter 7.1, except that we also included an unslotted 
Technical Memorandum – Technology Review for Storage Vessels

January 20, 2012

7

guidepole (U.S. EPA 1995a). We examined the impacts for storage vessels with no guidepole 

and with a slotted guidepole, but only the results for the unslotted guidepole are presented in this 

memorandum because all three results are similar, and the results for the unslotted guidepole are 

between those for no guidepole and a slotted guidepole. The typical construction of each deck 

fitting for Control Option ST1 is also based on information from AP-42 chapter 7.1. The 

modeled deck fittings for Control Option ST2 are consistent with requirements in many recent 

rules such as 40 CFR part 63, subpart WW. The decks were assumed to be constructed from 5-ft 

wide panels bolted together. Specific details of the fittings in IFRs for the model storage vessels 

are summarized in Table 4.

Table 4. Deck fittings for IFRs

Type of deck 

fitting

Deck fitting counts Deck fitting construction

Model 

A

Model 

B

Model

C Control Option ST1 Control Option ST2

Access hatches 1 1 1 Unbolted cover, 

ungasketed

Bolted cover, gasketed

Automatic gauge 

float wells

1 1 1 Unbolted cover, 

ungasketed

Bolted cover, gasketed

Column wells 1 1 1 Built up column, 

ungasketed sliding cover

Built-up column, 

gasketed sliding cover

Unslotted 

guidepole

1 1 1 Ungasketed sliding cover Gasketed sliding cover 

and pole wiper

Ladder wells 1 1 1 Sliding cover, ungasketed Sliding cover, gasketed

Roof legs 7 8 10 Adjustable

Sample wells 1 1 1 Slit fabric seal, 10% open

Stub drains 2 3 9 Slit fabric seal, 10% open

Vacuum breakers 1 1 1 Weighted mechanical actuation, gasketed

Models in the analysis of Control Option ST3 consisted only of a typical ladder with solid legs 

versus a comparable ladder with slots in one leg and a flexible enclosure. The typical ladder was 

assumed to have an ungasketed sliding deck cover, consistent with information in Table 7.1-12 

in AP-42 (U.S. EPA, 1995a).

We evaluated impacts of Control Option ST4 for a single typical storage vessel with 8 fittings on 

the fixed roof (an access hatch, a gauge hatch, a conservation vent, an emergency pressure relief 

vent, and 4 miscellaneous valves and instruments). Details of the costs and emissions for Control 

Option ST4 are presented in section 10 of this memorandum with analyses for other monitoring, 

recordkeeping, and reporting options.

External Floating Roofs 

Storage vessels designed with EFRs often are much larger than fixed roof storage vessels, 

particularly at petroleum refineries. To represent such storage vessels, we developed the six 

models presented in Table 5. These model storage vessels store three typical types of material at 

petroleum refineries: crude oil (RVP 5.0), gasoline (RVP 8.3), and jet naphtha. The diameters 

and heights are based on typical values from permits for refineries in Louisiana (RTI, 2002). The 

throughputs are based on the same data used to estimate throughputs for the models in Table 3. 

(Many storage vessels at petroleum refineries have much higher throughputs. However, such 
Technical Memorandum – Technology Review for Storage Vessels

January 20, 2012

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differences do not affect this analysis because changes in throughput affect only withdrawal 

emissions, and none of the control options reduces withdrawal emissions.) In addition to these 

six models, we also evaluated impacts for smaller EFR storage vessels at chemical 

manufacturing facilities using the three models presented in Table 3 (except that they are 

assumed to have an EFR in this analysis rather than a fixed roof). All of the models have a 

welded shell, white paint in good condition, a pontoon-type EFR, and a mechanical shoe rim 

seal.

Table 5. Model EFR storage vessels at petroleum refineries

Parameter Model storage vessel characteristics

Model D E F G H I

Stored material Crude oil Crude oil Gasoline Gasoline Jet naphtha Jet naphtha

Capacity, million gal 3.38 10.9 1.05 10.9 1.90 6.79

Height, ft 40 40 40 40 40 40

Diameter, ft 120 215 67 215 90 170

Throughput, million gal 26.9 40.4 17.9 40.4 22.2 34.3

Vapor pressure of 

stored material, psia at 

25°C

3.97 3.97 5.85 5.85 1.81 1.81

For Baseline and Control Option ST5, the count and construction of each deck fitting is assumed 

to be consistent with designations in Table 7.1-12 of AP-42, chapter 7.1 (U.S. EPA, 1995a). For 

Control Option ST6, the model deck fittings are consistent with requirements in recent rules such 

as 40 CFR part 63, subpart WW. Specific details of the fittings in EFRs for the model storage 

vessels are presented in Table 6. For Baseline and all control options, the secondary rim seal is 

assumed to be rim-mounted. The model storage vessels and EFRs for Control Option ST7 are the 

same as in Control Option ST6, except that they include a geodesic dome over the storage vessel.

We examined impacts for EFRs with both slotted and unslotted guidepoles. Only the results for 

slotted guidepoles are presented in this document because storage vessels with slotted guidepoles 

are used in a significant fraction of EFR storage vessels at petroleum refineries, and both the 

emissions and costs for control can be significantly higher than for unslotted guidepoles. 

Furthermore, the resulting cost effectiveness values are comparable for both types of guidepoles 

if the most costly control technique (a flexible enclosure) is used for the slotted guidepoles. 

Therefore, Table 6 shows the model EFR storage vessels are equipped with a slotted guidepole. 

Under Baseline and Control Option ST5 the model slotted guidepole was assumed to have an 

ungasketed cover, and under Control Options ST6 and ST7 the guidepole was assumed to be 

controlled with a flexible fabric enclosure.

Pressure Vessels

No model pressure vessels were developed for the control impacts analysis because no control 

options were developed for pressure vessels.
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January 20, 2012

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Table 6. Deck fittings for EFRs

Type of 

deck fitting

Deck fitting counts Deck fitting construction

Model 

A/B/C

Model 

D

Model 

E/G

Model 

F

Model 

H

Model 

I

Baseline and 

Control Option 

ST5

Control Option 

ST6 and Control 

Option ST7

Access 

hatches

1 1 1 1 1 1 Bolted and gasketed cover

Automatic 

gauge float 

wells

1 1 1 1 1 1 Unbolted, 

ungasketed 

cover

Bolted and 

gasketed cover

Vacuum 

breakers

1 1 3 1 1 2 Weighted mechanical actuation, 

gasketed

Slotted 

guidepoles

1 1 1 1 1 1 Ungasketed 

sliding cover

Gasketed sliding 

cover with 

flexible 

enclosure

Gaugehatch/

sample 

wells

1 1 1 1 1 1 Weighted mechanical actuation, 

gasketed

Roof legs 

(pontoon 

area)

4 19 32 13 16 27 Ungasketed

Roof legs 

(center 

area)

2 24 83 9 12 49 Ungasketed

Rim vents 1 1 1 1 1 1 Weighted mechanical actuation, 

gasketed

Degassing 

We evaluated the impacts of degassing controls for a matrix of model storage vessels. The model 

storage vessels presented in Table 3 were not used in this analysis because the resulting cost 

impacts are very high for storage vessels in that size range that have a floating roof. Therefore, 

for this analysis we developed models that resulted in a range of cost effectiveness values 

between about $2,500/ton of emissions reduction and $10,000/ton of emissions reduction under 

Control Option ST8. For each type of stored material we developed small models that have a 

cost effectiveness of about $2,500/ton, medium models that have a cost effectiveness of about 

$5,000/ton, and large models that have a cost effectiveness of about $10,000/ton. To meet these 

criteria, the model storage vessel sizes differed for each type of stored material. For storage 

vessels with a floating roof, the volume of vapor space to be degassed is the volume under the 

roof at its landed height. In this analysis, we assumed the roof lands at a height of 5 feet above 

the floor of each model storage vessel. We varied the model heights in 8-ft increments based on 

the standard width of the sheet metal, up to a maximum of 40 feet for petroleum products and 48 

feet for chemicals. Diameters for the models were selected based on the following criteria: (1) 

the diameter was always equal to or greater than the height; (2) for the small and medium 

models, the D/H ratio ranged up to 1.5:1 before going to the next height; and (3) for any model at 
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January 20, 2012

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the maximum height, the diameter was set at whatever size was needed to reach the cost 

effectiveness value of $2,500/ton. All of the characteristics of the stored materials and resulting 

model storage vessel dimensions and capacities are presented in Table 7.

7. Emissions Estimates

Uncontrolled emissions from fixed roof storage vessels

Uncontrolled emissions from the model fixed roof storage vessels in Table 3 were calculated 

using TANKS4.0.9d (U.S. EPA, 2006). Meteorological conditions were based on Houston, 

Texas. The sum of the working and breathing losses are presented in Table 8. We wanted to 

focus on scenarios where cost impacts of control options ranged from break even to about 

$10,000/ton of VOC. Therefore, the analysis for small models includes storage of materials with 

slightly higher vapor pressures than the analysis for large models.

Controlled emissions from Fixed Rood Storage Vessel (Control Options ST1 and ST2)

Controlled emissions from the model fixed roof storage vessels with characteristics presented in 

Tables 3 and 4 were calculated using a spreadsheet that replicates the procedures in 

TANKS4.0.9d. The resulting sum of rim seal losses, withdrawal losses, deck fitting losses, and 

deck seam losses for storage vessels with unslotted guidepoles are presented in Table 9. Only the 

deck fitting losses change between Control Options ST1 and ST2; the difference in deck fitting 

construction as presented in Table 4 accounts for this difference in emissions.

Baseline and Controlled Emissions for Slotted Ladders (Control Option ST3)

Emissions factors for slotted ladder legs are unavailable. However, according to AP-42, a ladder 

with solid legs and a gasketed deck cover has an emission factor (KFa) of 56 lbmole/yr. This is 

about 80 percent higher than the KFa for an unslotted guidepole with an ungasketed deck cover in 

AP-42 (i.e., 31 lbmole/yr). Thus, we assumed the KFa for a ladder with a slotted leg is also 80 

percent higher than the KFa for a slotted guidepole with a gasketed deck cover (77 lbmole/yr 

versus 43 lbmole/yr). The emission factor for a ladder with solid legs and a ladder sleeve in 

addition to a gasketed deck cover has been estimated to be 29 lbmole/yr (Ferry, 2006). This is 

about 3.3 times higher than the factor for an unslotted guidepole with the same controls (i.e., 8.6 

lbmole/yr). Assuming the same ratio applies for slotted ladder legs and slotted guidepoles gives a 

controlled emission factor of about 37 lbmole/yr for a slotted ladder leg controlled with a ladder 

sleeve and a gasketed deck cover (i.e., 11 x 3.3 = 37). According to the AP-42 factors, adding a 

pole wiper lowers the factor slightly. Therefore, we assumed a factor of 35 lbmole/yr for this 

analysis.
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January 20, 2012

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Table 7. Characteristics of model storage vessels for analysis of degassing controls

Parameter

Characteristics of model storage vessels storing various materials

Crude oil 

(RVP 5)

Gasoline 

(RVP 8.3)

Vinylidene 

chloride n-pentane

Methylene 

chloride Diethylamine Chloroprene

Vapor molecular weight 50 68 96.5 72.15 84.94 73.14 88.54

Vapor pressure1 3.56 5.46 11.06 9.09 7.32 4.02 3.94

Density of liquid (lb/gal) 7.1 5.6 10.38 5.25 11.12 5.91 8.05

Lower heating value, Btu/lb 18,400 18,700 4,800 19,500 2,500 16,600 3,000

Vessel volume (gal)

 Small 611,000 230,000 33,900 103,000 88,100 286,000 205,000

 Medium 1,580,000 763,000 111,000 348,000 244,000 903,000 541,000

 Large 7,280,000 3,730,000 332,000 2,930,000 635,000 4,200,000 1,380,000

Height (ft)

 Small 40 32 16 24 24 32 32

 Medium 40 40 24 32 32 40 40

 Large 40 40 32 48 40 48 48

Diameter (ft)

 Small 51 35 19 27 25 39 33

 Medium 82 57 28 43 36 62 48

 Large 176 126 42 102 52 122 70

Volume degassed for vessel 

with IFR/EFR (ft3)

2

 Small 10,000 4,800 1,400 2,900 2,500 6,000 4,300

 Medium 26,000 13,000 3,100 7,300 5,100 15,000 9,000

 Large 120,000 62,000 6,900 41,000 11,000 58,000 19,000 1

Vapor pressure at the temperature of the vapor space, which was assumed to be 74°F for each model storage vessel.

2

Volume under the floating roof determined assuming the floating roof lands at a height 5 ft above the floor for each model storage vessel.
Technical Memorandum – Technology Review for Storage Vessels

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Table 7. Characteristics of model storage vessels for analysis of degassing controls (continued)

Parameter

Characteristics of model storage vessels storing various materials

Chloroform n-hexane 1,1,1-trichlorethane Methanol Benzene

Vapor molecular weight 119.39 86.17 133.42 32.04 78.11

Vapor pressure1 3.47 2.62 2.25 2.13 1.66

Density of liquid (lb/gal) 12.49 5.53 11.22 6.63 7.37

Lower heating value (Btu/lb) 1,500 19,400 4,000 9,100 17,400

Vessel volume (gal)

 Small 127,000 476,000 244,000 1,720,000 818,000

 Medium 348,000 1,540,000 635,000 3,790,000 2,490,000

 Large 903,000 7,960,000 1,670,000 9,440,000 10,100,000

Height (ft)

 Small 24 40 32 48 40

 Medium 32 48 40 48 48

 Large 40 48 48 48 48

Diameter (ft)

 Small 30 45 36 78 59

 Medium 43 74 52 116 94

 Large 62 168 77 183 189

Volume degassed for vessel 

with IFR/EFR (ft3)

2

 Small 3,500 8,000 5,100 24,000 14,000

 Medium 7,300 22,000 11,000 53,000 35,000

 Large 15,000 110,000 23, 000 130,000 140,000 1

Vapor pressure at the temperature of the vapor space, which was assumed to be 74°F for each model storage vessel.

2

Volume under the floating roof determined assuming the floating roof lands at a height 5 ft above the floor for each model storage vessel.
Technical Memorandum – Technology Review for Storage Vessels

January 20, 2012

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Table 8. Uncontrolled emissions from fixed roof storage vessels

Stored material

Vapor pressure at 

25°C

Uncontrolled emissions, lb/yr

Model A Model B Model C

Acrylic acid 0.08 270 970

Xylene 0.13 620 2,200

Toluene 0.55 1,500 2,400 8,400

Methyl methacrylate 0.70 2,000 3,300 12,000

1,4-Dioxane 0.72 1,800 3,000 11,000

Formic acid 0.83 1,100 1,800 6,400

Isooctane 0.95 3,200 5,200 18,000

Ethanol 1.2 1,500 2,500 8,600

Trichloroethylene 1.3 5,100 8,300 29,000

Ethylene dichloride 1.5 4,400 7,100 25,000

Methyl ethyl ketone 1.7 3,700 6,000 21,000

Acetonitrile 1.8 2,200 3,500 12,000

Ethyl acetate 1.8 4,700 7,700 26,000

Jet naphtha 1.8 7,200 25,000

Benzene 1.8 4,200 6,900 24,000

Vinyl acetate 2.2 5,600 9,100 31,000

Acrylonitrile 2.2 3,500 5,600 19,000

Methanol 2.4 2,300 3,700 13,000

1,1,1-trichlorethane 2.6 10,000 17,000 56,000

Methylcyclopentane 2.7 6,700 11,000 37,000

Hexane 2.9 7,600 12,000 42,000

Chloroform 3.8 13,000 22,000 74,000

Diethylamine 4.6 10,000 16,000

Methylene chloride 8.3 23,000
Technical Memorandum – Technology Review for Storage Vessels

January 20, 2012

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Table 9. Emissions from fixed roof storage vessels controlled with IFR

Stored material

Controlled emissions (lb/yr)

Model A Model B Model C

Control 

Option 

ST1

Control 

Option 

ST2

Control 

Option 

ST1

Control 

Option 

ST2

Control 

Option 

ST1

Control 

Option 

ST2

Acrylic acid 120 120 140 130

Xylene 150 130 180 160

Toluene 350 280 370 300 460 390

Methyl methacrylate 460 360 490 400 610 510

1,4-Dioxane 440 350 460 380 570 480

Formic acid 320 270 330 280 400 350

Isooctane 660 500 710 560 900 740

Ethanol 360 280 380 300 470 390

Trichloroethylene 1,100 850 1,200 930 1,500 1,200

Ethylene dichloride 940 730 1,000 800 1,300 1,100

Methyl ethyl ketone 770 590 840 650 1,100 870

Acetonitrile 480 380 520 410 650 540

Ethyl acetate 980 750 1,100 830 1,300 1,100

Jet naphtha 980 760 1,200 1,000

Benzene 890 680 960 750 1,200 1,000

Vinyl acetate 1,200 890 1,300 990 1,600 1,300

Acrylonitrile 740 570 800 630 1,000 840

Methanol 510 400 540 430 680 570

1,1,1,-trichloroethane 2,100 1,600 2,300 1,800 2,900 2,400

Methylcyclopentane 1,400 1,000 1,500 1,200 1,900 1,600

Hexane 1,500 1,200 1,700 1,300 2,200 1,800

Chloroform 2,800 2,100 3,100 2,400 3,900 3,200

Diethylamine 2,100 1,600 2,300 1,800

Methylene chloride 5,400 4,000

Baseline and Controlled Emissions from External Floating Roof Storage Vessels

Baseline emissions and the controlled emissions under Control Options ST5, ST6, and ST7 from 

model storage vessels with an EFR and the characteristics in Tables 3, 5, and 6 were estimated 

using a spreadsheet that replicates the procedures in TANKS4.0.9d. The results are presented in 

Table 10. The emissions include rim seal losses, withdrawal losses, and deck fitting losses. As 

with the fixed roof and IFR storage vessels, meteorological conditions in Houston, Texas were 

considered to be representative.
Technical Memorandum – Technology Review for Storage Vessels

January 20, 2012

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Table 10. Emissions from model storage vessels with an EFR

Stored material

Vapor 

pressure at 

25°C

Emissions (lb/yr)

Baseline

Control 

Option ST5

Control 

Option ST6

Control 

Option ST7

Model A

Xylene 0.13 710 640 130 86

Toluene 0.55 2,600 2,300 200 100

Methyl methacrylate 0.70 3,500 3,200 250 120

Formic acid 0.83 2,000 1,800 200 130

Isooctane 0.95 5,500 5,000 320 120

Methyl ethyl ketone 1.7 6,500 5,800 380 140

Benzene 1.8 7,600 6,700 440 160

Methanol 2.4 4,100 3,600 260 120

Hexane 2.9 14,000 12,000 720 210

Chloroform 3.8 25,000 23,000 1,300 410

Model B

Acrylic acid 0.08 370 340 100 91

Xylene 0.13 730 640 110 81

Toluene 0.55 2,600 2,300 200 100

Methyl methacrylate 0.70 3,600 3,200 260 120

Formic acid 0.83 2,100 1,800 200 120

Isooctane 0.95 5,700 5,000 340 120

Methyl ethyl ketone 1.7 6,700 5,900 410 140

Benzene 1.8 7,800 6,800 470 160

Methanol 2.4 4,200 3,600 280 110

Hexane 2.9 14,000 12,000 780 2208

Model C

Acrylic acid 0.08 410 340 110 97

Xylene 0.13 800 660 120 86

Toluene 0.55 2,900 2,300 240 110

Methyl methacrylate 0.70 4,000 3,200 310 130

Formic acid 0.83 2,300 1,900 240 130

Isooctane 0.95 6,300 5,100 420 140

Methyl ethyl ketone 1.7 7,400 6,000 570 180

Benzene 1.8 8,600 6,900 340 130

Methanol 2.4 4,600 3,700 500 160

Hexane 2.9 16,000 13,000 970 250

Petroleum liquid models

Model D (crude oil) 4.0 9,100 5,100 1,100 420

Model E (crude oil) 4.0 13,000 5,700 1,800 580

Model F (gasoline) 5.8 36,000 24,000 3,000 730

Model G (gasoline) 5.8 69,000 30,000 8,500 2,200

Model H (jet naphtha) 1.8 13,000 7,700 1,200 310

Model I (jet naphtha) 1.8 18,000 8,600 2,100 540
Technical Memorandum – Technology Review for Storage Vessels

January 20, 2012

16

Emissions from Degassing

Uncontrolled emissions from degassing operations were estimated based on data from degassing 

logs obtained by the SCAQMD during development of degassing regulations in the District 

(SCAQMD, 2008). Most of the logs were for degassing storage vessels that were used to store 

gasoline. These logs showed a wide range in the mass of emissions relative to the amount of 

gasoline vapor that could be held in the vapor space at saturation. On average, the emissions 

were 1.3 times the saturated vapor level, which suggests that in many cases, storage vessels

contain residual liquid (alone or as a component in sludge) that volatilizes and is emitted while 

degassing. In the absence of data for degassing of storage vessels used to store other types of 

materials, we assumed that this factor is representative of degassing all storage vessels and used 

it to estimate typical degassing emissions for all of the model storage vessels in Table 7. The 

results are presented in Table 11.

Table 11. Uncontrolled degassing emissions from model storage vessels

Stored material

Uncontrolled degassing emissions, lb/event

Small Medium Large

Crude oil 410 1,100 4,900

Gasoline 410 1,100 5,200

Vinylidene chloride 340 750 1,700

n-pentane 430 1,100 6,100

Methylene chloride 350 720 1,500

Diethylamine 400 1,000 3,900

Chloroprene 340 720 1,500

Chloroform 330 680 1,400

n-hexane 410 1,100 5,700

1,1,1-trichlorethane 350 720 1,600

Methanol 370 820 2,000

Benzene 400 1,000 4,100

Control devices can be designed and operated to reduce incoming emissions by 95 percent or 

more. However, the overall reduction relative to uncontrolled emissions will also depend on how 

much material is left in the storage vessel when degassing control stops. If degassing is required 

until the concentration in the vapor space remains below a specified level, then the overall 

efficiency will also depend on the vapor pressure of the stored material. Specifically, the 

efficiency will increase as vapor pressure increases. For this analysis, we assumed the model 

storage vessels are degassed to a concentration below 5,000 ppmv and that the floor and walls 

are dry. With these assumptions, the overall control efficiencies range from 92 percent for 

benzene to more than 94 percent for vinylidene chloride; the control efficiency for gasoline is 94 

percent.
Technical Memorandum – Technology Review for Storage Vessels

January 20, 2012

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8. Control Costs

Cost of Fixed Roof Control Options 

The unit costs and factors used to estimate costs for a typical internal floating roof retrofit 

(Control Option ST1), improved deck fittings (Control Option ST2), and slotted ladder leg 

controls (Control Option ST3) are presented in Table 12. Note that Control Option ST4 is based 

on monitoring procedures, and the costs are presented in section 10 of this memorandum.

Cost of EFR Control Options

The unit costs and factors used to estimate costs for secondary rim seals (Control Option ST5), 

improved fittings control (Control Option ST6), and geodesic domes (Control Option ST7) are 

presented in Table 13. For Control Option ST6, costs were estimated for only those deck fittings 

that are assumed not to be controlled to typical regulatory levels at baseline.
Technical Memorandum – Technology Review for Storage Vessels

January 20, 2012

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Table 12. Capital and annual cost factors for fixed roof and IFR control options

Costing element Unit cost or costing factor Basis1

Control Option ST1 (add IFR with single rim seal and typical deck fittings)

Capital costs

Internal floating roof E = see footnote 2 Fit a curve to quoted installed costs from three 

vendors and then multiplied by the fraction for 

equipment from one vendor (Dia is in ft)

Mobilization MO = $2,000 Assumed

Taxes and freight TF = 0.08 x E EPA Control Cost Manual (U.S. EPA, 2002)

Installation I = see footnote 3 Similar to basis for E

Total capital investment TCI = E + MO + TF + I

Annual costs

Capital recovery CR = 0.1098 x TCI Capital recovery factor calculated using 

equation in OAQPS Control Cost Manual (U.S. 

EPA, 2002); assumed IFR life of 15 years and 

used 7% interest rate

Maintenance MA = 0.05 x TCI From other EPA analyses (U.S. EPA, 1994)

Property taxes, 

insurance, 

administration

P = 0.04 x TCI EPA Control Cost Manual (U.S. EPA, 2002)

Product recovery credit R = $900/ton for chemicals

R = $500/ton for petroleum 

products

Average of typical chemical costs as noted in 

EL NSPS review memo (Parrish and Randall, 

2007)

Total annual cost TAC = CR + MA + P + R

Control Option ST2 (upgrade deck fittings)

Capital costs

Bolted, gasketed cover 

for access hatches

$400/hatch Approximated value based on several quotes for 

covers on wells for various fittings

Bolted, gasketed cover 

for automatic gauge 

float wells

$400/well Approximated value based on several quotes for 

covers on wells for various fittings

Column well cover $550/column From vendor quotes. 

Ladder cover (gasketed) $400/ladder From vendor quote

Gasketed cover and 

pole wiper for unslotted 

guidepole

$950/guidepole Approximated cover cost based on costs for 

column well covers ($550). No data for pole 

wipers; assumed no more than $400, a quoted 

cost for a gauge pole sleeve.

Annual costs Same factors as for Control Option 

ST1

Control Option ST3 (slotted ladder leg controls)

Capital costs for slotted 

ladder leg gasketed deck 

cover, ladder sleeve, and 

pole wiper

$1,250/ladder Sum of quoted costs for gasketed cover ($400), 

and ladder sleeve ($450), and assumed pole 

wiper cost ($400). Equipment costs (E) assumed 

to be 50 percent of total.. 

Taxes and freight TF = 0.08 x E EPA Control Cost Manual (U.S. EPA, 2002)

Annual costs Same factors as for Control Option 

ST1 1

Vendor quotes are maintained in the OAQPS CBI files. Some of the cited costs are averages of two or three quotes; 

others are based on a single quote. Details are provided in the CBI files (Randall, 2012a). 2

E = (29.207 x Dia^0.1796)/100 x (6.3825 x Dia^2 + 374.27 x Dia + 19017). 3

I = (1 – (29.207 x Dia^0.1796)/100 x (6.3825 x Dia^2 + 374.27 x Dia + 19017)
Technical Memorandum – Technology Review for Storage Vessels

January 20, 2012

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Table 13. Capital and annual cost factors for EFR control options

Costing element Unit cost or costing factor Basis1

Control Option ST5 (add second rim seal)

Capital costs

Secondary rim seal

materials

S = (Circumference) x (383.47 x 

(Dia.)^-0.262)/2

Curve fit to quoted installed 

costs; assumed material costs are 

50 percent of the total installed 

cost. Circumference and Dia are 

expressed in feet.

Mobilization M = $2,000 Assumed

Taxes and freight TF = 0.08 x S EPA Control Cost Manual (U.S. 

EPA, 2002)

Installation I = S Assumed installation costs are 50 

percent of the total installed cost

Total capital investment TCI = S + M + TF + I

Annual costs

Capital recovery CR = 0.1098 x TCI Capital recovery calculated using 

equation in EPA Control Cost 

Manual (U.S. EPA, 2002); 

assumed seal life of 15 years and 

used 7% interest rate

Property taxes, 

insurance, administration

P = 0.04 x TCI EPA Control Cost Manual (U.S. 

EPA, 2002)

Product recovery credit R = $900/ton for chemicals

R = $500/ton for petroleum products

Average of typical chemical costs 

as noted in EL NSPS review 

memo (Parrish and Randall, 

2007)

Total annual cost TAC = CR + P + R

Control Option ST6 (upgrade deck fittings)

Capital costs

Bolted, gasketed cover 

for automatic gauge float 

wells

$400/well Approximated value based on 

several quotes for covers on wells 

for various fittings

Flexible fabric enclosure 

for slotted guidepole

$150/ft of tank height From vendor quotes

Annual costs Same factors as for Control Option ST5

Control Option ST7 (add geodesic dome)

Capital costs 13.85 x Dia^2 + 125.62 x Dia + 21572 Curve fit through quotes from 3 

vendors as reported in 2001 

SCAQMD staff report 

(SCAQMD, 2001; Randall, 

2012b). Dia is expressed in feet.

Annual costs Same factors as for Control Option ST5 1

The original vendor quotes are maintained in the OAQPS CBI files; procedures used to develop the cited costs in 

this table are also maintained in the CBI files (Randall, 2012a).
Technical Memorandum – Technology Review for Storage Vessels

January 20, 2012

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Cost of Control for Degassing

We considered two sources of cost information. The SCAQMD determined that degassing 

companies typically charged between $2,000 and $20,000 to degas storage vessels ($7,000 to 

$10,000 to degas an average sized storage vessel) when SCAQMD rule 1149 required control for 

at least 2.3 air exchanges (SCAQMD, 2008). (This cost consisted of a $2,000 flat fee and the 

remainder as an hourly charge. They also determined that on average, degassing a typical tank 

for 2.3 air exchanges takes about 8.5 hours. Thus, the hourly rate was estimated to be about $940 

(2,000 + 8.5 x 940 = 10,000). For proposed amendments that would require degassing until the 

organic concentration in the vapor space is less than 5,000 ppmv, SCAQMD estimated the 

average degassing time would increase to 24 hours, and the cost would increase to about 

$24,000. Both of these costs, however, are significantly higher than the unit cost of about $1.5/lb 

of VOC destroyed presented in literature from Envent, a company that conducts degassing using 

four models of mobile thermal oxidation units that are capable of controlling between 160 lb 

VOC/hr and 360 lb VOC/hr (Envent). Multiplying this unit cost by the reported VOC destruction 

capacity and hours to reach less than 20 percent of the LEL (i.e., about 7,000 ppmv for gasoline) 

for 3.36 million gallon gasoline storage vessel resulted in a total cost of about $3,700. See 

attachment A for details of the information available from Envent.)

For this analysis we decided to use the cost information from Envent because it could be 

customized for different storage vessels. Furthermore, it is apparently an achievable cost for one 

type of degassing control technology, whereas the information in the SCAQMD analysis is 

reportedly an average cost for an unknown mix of technologies, some of which may be more 

costly than others. To use the Envent costs, we also assumed that the fees would be structured as 

reported by SCAQMD (i.e., a flat fee plus an hourly charge). Because the overall SCAQMD 

costs were significantly higher, we assumed both the flat fee and the hourly rate should be lower 

for the Envent costs, but we reasoned that the flat fee obtained by SCAQMD is likely more 

accurate than the hourly charge. Therefore, we selected a flat fee of $1,600 (20 percent lower 

than SCAQMD) and an hourly charge of $250/hr (more than 70 percent lower than SCAQMD). 

As an example, when applied to the second largest of the four Envent degassing control systems, 

this structure resulted in a total cost of about $3,900 for the 3.36 million gallon gasoline storage 

vessel, which is only about 5 percent higher than total cost that we derived using the data 

available from Envent.

To estimate costs for the model storage vessels with the characteristics presented in Table 7 and 

the uncontrolled degassing emissions presented in Table 11, we first estimated the time to degas 

the applicable volume (i.e., the volume under a floating roof or the total volume of a fixed roof 

storage vessel) to an organic compound vapor concentration less than 5,000 ppmv. We assumed 

the thermal oxidation units could handle the same total heat load regardless of the organic 

compound in the degassing exhaust stream. Thus, the estimated time to degas a storage vessel 

increases with increases in the lower heating value of the material stored in the storage vessel. 

The resulting estimates of degassing time and cost are presented in Table 14.
Technical Memorandum – Technology Review for Storage Vessels

January 20, 2012

21

Table 14. Degassing time and cost for model storage vessels

Stored 

material

Small model (cost 

effectiveness = 

$10,000/ton)

Medium model (cost 

effectiveness = $5,000/ton)

Large model (cost 

effectiveness = $2,500/ton)

Degassing 

time (hr)

Degassing 

cost ($)

Degassing 

time (hr)

Degassing 

cost ($)

Degassing 

time (hr)

Degassing 

cost ($)

Crude oil 1.4 2,000 3.7 2,500 17 5,900

Gasoline 1.4 2,000 3.8 2,500 19 6,200

Vinylidene 

chloride

0.3 1,700 0.7 1,800 1.5 2,000

n-Pentane 1.6 2,000 4.0 2,600 23 7,200

Methylene 

chloride

0.2 1,600 0.3 1,700 0.7 1,800

Diethylamine 1.2 1,900 3.1 2,400 12 4,700

Chloroprene 0.2 1,600 0.4 1,700 0.9 1,800

Chloroform 0.1 1,600 0.2 1,600 0.4 1,700

n-Hexane 1.5 2,000 4.0 2,600 21 6,800

1,1,1-

Trichlorethane

0.3 1,700 0.5 1,700 1.2 1,900

Methanol 0.6 1,800 1.4 1,900 3.4 2,500

Benzene 1.3 1,900 3.3 2,400 13 4,900

9. Impact Estimates for Storage Vessels

Fixed roof

Figures 1 and 2 are plots of the cost effectiveness versus vapor pressure of Control Options ST1 

and ST2 for model fixed roof storage vessels. The equations on the graphs can be used to 

calculate costs for the trendlines through the data for each model storage vessel. Each trendline is 

based on a power function. Note that all of the points that are well above the applicable 

trendlines are for compounds with low molecular weights (i.e., methanol, ethanol, formic acid, 

acetonitrile, and acrylonitrile). Points well below the trendlines are for compounds with high 

molecular weights. The cost effectiveness for Control Option ST2 varies only with the vapor 

pressure of the stored material, not the size of the storage vessel; the slightly different values 

(and trendlines) in Figure 2 are due to slight differences in rounding of the emissions estimates in 

the product recovery credit calculations. See attachment B for tabular summaries of the capital 

cost, annual cost, emission reduction, and cost effectiveness for each model and control option. 
Technical Memorandum – Technology Review for Storage Vessels

January 20, 2012

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Figure 1. Plot of cost effectiveness versus vapor pressure of Control Option ST1 for Models 

A, B, and C
Technical Memorandum – Technology Review for Storage Vessels

January 20, 2012

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Figure 2. Plot of cost effectiveness versus vapor pressure of Control Option ST2 for Models 

A, B, and C
Technical Memorandum – Technology Review for Storage Vessels

January 20, 2012

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Table 15 presents the results of the impacts analysis for Control Option ST3 (slotted ladder leg 

controls) (the results are the same for each model storage vessel because the costs are a function 

of the number of ladders, which is one for each of the models). The capital costs for the deck 

cover gasket, ladder sleeve, and pole wiper are the same for all storage vessels regardless of the 

storage volume. Annual costs also are the same for all storage vessels, but the product recovery 

credit varies because the mass of emissions prevented varies depending on the characteristics 

(vapor pressure and molecular weight) of the stored material. As a result, the cost effectiveness 

impacts are the same for any size of storage vessel and vary with the vapor pressure of the stored 

material. The results in Table 15 also show the cost effectiveness to be similar to the cost 

effectiveness values for Control Option ST1.

Table 15. Impacts of Control Option ST3

Stored 

material

Vapor 

pressure at 

25°C

Total capital 

investment ($)

Total annual 

cost ($/yr)

Emission 

reduction 

(lb/yr)

Cost 

effectiveness 

($/ton)

Xylene 0.13 1,300 260 8.3 62,000

Toluene 0.55 1,300 240 35 14,000

Methyl 

methacrylate

0.70 1,300 240 50 9,500

Formic acid 0.83 1,300 250 28 17,000

Isooctane 0.95 1,300 220 82 5,400

Methyl ethyl 

ketone

1.7 1,300 210 100 4,100

Benzene 1.8 1,300 210 120 3,400

Methanol 2.4 1,300 230 67 6,900

Hexane 2.9 1,300 150 240 1,300

Chloroform 3.8 1,300 56 450 250

EFR

Figures 3 through 5 are plots of the cost effectiveness versus vapor pressure of Control Options 

ST5, ST6, and ST7 for model EFR storage vessels (for Models A, B, and C, which are smaller 

storage tanks at chemical manufacturing facilities). Figure 3 shows the costs are a stronger 

function of the vapor pressure of the stored material than the size of the storage vessel. 

Trendlines and the corresponding equations based on power functions are also shown on Figure 

3. Figure 4 shows Control Option ST6 results in cost savings for nearly all storage vessels 

except those that store material with a vapor pressure less than about 0.4 psia. Figure 5 shows the 

costs of Control Option ST7 are much higher than the costs of any of the other control options. 

See attachment C for tabular summaries of the capital cost, annual cost, emission reduction, and 

cost effectiveness for each model and control option. Tables 16 through 18 show that the impacts 

for larger model storage tanks storing petroleum products (Models D through I) are in line with 

the results in Figures 3 through 5 for smaller storage vessels.
Technical Memorandum – Technology Review for Storage Vessels

January 20, 2012

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Figure 3. Plot of cost effectiveness versus vapor pressure of Control Option ST5 for Models 

A, B, and C
Technical Memorandum – Technology Review for Storage Vessels

January 20, 2012

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Figure 4. Plot of cost effectiveness versus vapor pressure of Control Option ST6 for Models 

A, B, and C
Technical Memorandum – Technology Review for Storage Vessels

January 20, 2012

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Figure 5. Plot of cost effectiveness versus vapor pressure of Control Option ST7 for Models 

A, B, and C
Technical Memorandum – Technology Review for Storage Vessels

January 20, 2012

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Table 16. Impacts of Control Option ST5 (add secondary rim seal) for large storage vessels 

with EFR that contain petroleum products

Model Stored material

Total capital 

investment ($)

Total annual 

cost ($/yr)

Emission 

reduction 

(lb/yr)

Cost 

effectiveness 

($/ton)

D Crude oil 45,000 5,700 4,000 2,800

E Crude oil 68,000 8,400 7,300 2,300

F Gasoline 30,000 1,400 12,000 240

G Gasoline 68,000 460 39,000 23

H Jet naphtha 37,000 4,200 5,000 1,700

I Jet naphtha 57,000 6,200 9,400 1,300

Table 17. Impacts of Control Option ST6 (upgrade fittings) for large storage vessels with 

EFR and slotted guidepole that contain petroleum products

Model

Total 

capital 

investment 

($)

Total 

annual cost 

($/yr)

Emission reduction (lb/yr) Cost effectiveness ($/ton)

Versus 

baseline

Versus 

Control 

Option ST5

Versus 

baseline

Versus 

Control 

Option ST5

D 51,000 5,700 8,000 4,000 1,400 (18)

E 74,000 8,300 11,000 4,000 1,500 (18)

F 36,000 (2,900) 33,000 21,000 (180) (410)

G 74,000 (3,900) 60,000 21,000 (130) (410)

H 43,000 3,600 12,000 6,500 (620) (210)

I 64,000 5,600 16,000 6,500 (700) (210)

Table 18. Impacts of Control Option ST7 (add geodesic dome) for large storage vessels with 

EFR and slotted guidepole that contain petroleum products

Model

Total capital 

investment ($)

Total annual 

cost ($/yr)

Emission reduction 

(lb/yr) Cost effectiveness ($/ton)

Versus 

baseline

Versus 

Control 

Option 

ST6

Versus 

baseline

Versus 

Control 

Option ST6

D 290,000 41,000 8,700 670 9,400 100,000

E 760,000 110,000 12,000 1,200 18,000 170,000

F 130,000 10,000 36,000 2,300 580 12,000

G 760,000 98,000 67,000 6,300 2,900 32,000

H 190,000 25,000 12,000 870 4,000 49,000

I 510,000 72,000 18,000 1,500 8,200 86,000
Technical Memorandum – Technology Review for Storage Vessels

January 20, 2012

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Degassing

Figure 6 presents the storage vessel size and vapor pressure relationships for two cost 

effectiveness curves ($2,500/ton and $5,000/ton). Curves for higher cost effectiveness values 

(e.g., $10,000/ton) would be lower on the graph. Curves for lower cost effectiveness values (e.g., 

$1,500/ton) would be higher on the graph, if they are feasible at all; most materials reach a point 

of diminishing returns where increasing size of the storage vessel results in essentially equivalent 

percentage increases in both the cost of degassing and the additional emission reduction. Both of 

the curves in Figure 6 show the cost impacts of degassing control are much higher than for 

Control Options ST1, ST2, ST3, ST5, and ST6. Stated another way, for the same cost 

effectiveness value, the storage vessel size must be significantly large under Control Option ST8 

than under the other control options. For example, the $2,500/ton curve shows IFR and EFR 

storage vessels would have to be over 2,000,000 gal if the vapor pressure is less than 5 psia. 

Similarly, the $5,000/ton curve shows IFR and EFR storage vessels would have to be larger than 

1,000,000 gal if the vapor pressure is less than 3 psia.

Figure 6. Cost effectiveness curves for degassing controls (Control Option ST8)
Technical Memorandum – Technology Review for Storage Vessels

January 20, 2012

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Nationwide Impacts for SOCMI Facilities and Petroleum Refineries

For most chemical manufacturing facilities, the costs to comply with the combined requirements 

of Control Options ST1, ST2, ST5 and ST6 for atmospheric storage vessels above the proposed 

thresholds are expected to be zero or minimal because they are already subject to current rules 

that have the same or similar thresholds and control requirements. However, many storage 

vessels at petroleum refineries are subject to 40 CFR part 63, subpart CC, which does not require 

control of deck fittings (i.e., Control Options ST2 and ST6). Based on information provided by 

petroleum refiners in response to an information request, we determined that nationwide there 

are approximately 2,400 storage vessels with an EFR and 1,400 storage vessels with an IFR that 

meet or exceed the thresholds for control in current rules (e.g., the HON), and about 60 percent 

of these storage vessels have slotted guidepoles (U.S. EPA, 2011). About 50 percent of the IFR 

storage vessels that have slotted guidepoles are controlled, and about two-thirds of the EFR 

storage vessels that have slotted guidepoles are controlled. We assumed all of the other fittings 

have typical controls (i.e., consistent with Control Options ST1 and ST5). We also assumed each 

EFR is equipped with two rim seals, as required in 40 CFR part 63, subpart CC, and in Control 

Option ST5. To estimate current annual emissions, we first represented each storage vessel with 

one of four model sizes. Each model storage vessel also was assigned one of four model liquids 

depending on the reported vapor pressure of the actual stored liquid. Storage vessels containing 

liquids with the lowest vapor pressures were represented with methyl ethyl ketone. The other 

storage vessels were organized into three groups, each of which was represented with a different 

grade of gasoline (RVP6, RVP10 and RVP14).

We estimated the current and controlled emissions for each model refinery storage vessel using 

the AP-42 procedures and other assumptions as described in section 7 of this memorandum. We 

estimated costs to upgrade fittings for each storage vessel using the same information described 

in section 8 of this memorandum. We also applied a product recovery credit of $500/ton of VOC 

to the prevented petroleum product emissions. The emission reductions associated with 

upgrading the deck fittings on EFR storage vessels, particularly slotted guidepoles, resulted in a 

product recovery credit that exceeded the estimate of all costs associated with Control Options 

ST2 and ST6. Thus, the nationwide impacts of the control options for petroleum refineries is a 

cost savings of about $350/ton of VOC controlled. Table 19 summarizes the nationwide number 

of storage vessels, capital and annual costs, emission reductions and cost effectiveness. 

Attachment D provides details of the model storage vessels used to represent each of the storage 

vessels nationwide.

Table 19. Nationwide impacts of Control Options ST2 and ST6 for petroleum refineries

Type 

of 

storage 

vessel

Nationwide 

number of 

storage 

vessels

Nationwide 

VOC 

emission 

reduction 

(tpy)

Nationwide 

total capital 

investment 

($)

Nationwide 

total annual 

costs (without 

VOC recovery 

credit) ($/yr)

Nationwide 

VOC 

recovery 

credit

($/yr)

Nationwide 

total annual 

cost with 

VOC 

recovery 

credit ($/yr)

Cost 

effectiveness 

($/ton VOC 

controlled)

IFR 1357 874 7,070,000 1,060,000 (437,000) 622,000 710

EFR 2362 10,500 4,540,000 680,000 (5,250,000) (4,570,000) (440)

Total 3719 11,400 11,600,000 1,740,000 (5,690,000) (3,950,000) (350)
Technical Memorandum – Technology Review for Storage Vessels

January 20, 2012

31

10. Monitoring, Recordkeeping, and Reporting

Monitoring Fittings on Fixed Roofs

We assumed a typical fixed roof has one access hatch, one gauge hatch, one conservation vent, 

one emergency pressure relief vent, and four miscellaneous valves and instruments. As discussed 

in section 5 of this memorandum, Control Option ST4 is based on periodic monitoring of these 

fittings for leaks. In this analysis we examined three types of monitoring approaches. Control 

Option ST4a is based on visual monitoring, Control Option ST4b is based on monitoring using 

Method 21, and Control Option ST4c is based on monitoring using optical gas imaging. 

Emissions for baseline and visual inspections were assumed to be the same (i.e., we do not have 

sufficient data to estimate reductions that are achieved when annual visual inspections are 

conducted). The baseline emissions for access hatches and gauge hatches were estimated using 

AP-42 procedures for estimating emissions from such fittings on EFRs. We assumed the access 

hatch has an unbolted gasketed cover, and that the gauge hatch has a weighted mechanical 

actuation and is gasketed. We estimated the baseline emissions for the conservation vent, 

emergency pressure relief vent, and other valves/instruments using the average emission factors 

for open ended lines, pressure relief vents, and valves, respectively, in the synthetic organic 

chemical manufacturing industry from EPA’s Protocol for Equipment Leak Emission Estimates 

(U.S. EPA, 1995b). (Note that this methodology may underestimate baseline emissions for 

storage vessels storing petroleum products if the average emission factors for equipment in 

petroleum refineries provide a more realistic estimate of emissions for such storage vessels.) 

Based on the experience of EPA inspectors, we assumed that monitoring with Method 21 would 

find an average of one leaking fitting per storage vessel (instrument reading greater than 500 

ppmv); thus, 12.5 percent of fittings are assumed to be leaking currently. We assumed 5 percent 

of the fittings would be found leaking during annual monitoring with Method 21, resulting in an 

average 80 percent reduction in emissions. In an LDAR program for equipment leaks, optical gas 

imaging is assumed to achieve comparable performance to Method 21, provided the optical gas 

imaging is conducted more frequently than Method 21 monitoring. For this analysis, we assumed 

that optical gas imaging conducted semiannually would result in performance comparable to that 

for annual Method 21 monitoring. Table 20 presents the estimated uncontrolled/baseline 

emissions and the controlled emissions when annual monitoring is conducted using Method 21 

and semiannual monitoring is conducted using optical gas imaging.

The estimated level of effort and cost of monitoring, repair, recordkeeping, and reporting for 

three monitoring approaches are presented in Table 21. The average time to conduct either type 

of instrument monitoring was assumed to be greater than for visual monitoring because of the 

instrument setup, calibration, and operating requirements. We also assumed the average 

monitoring time increases slightly with increases in the size of the facility to account for 

potentially greater travel distances to the storage vessels and a greater percentage of large storage 

vessels at large facilities (which take longer to climb and to access all fittings). Initial monitoring 

costs are lower for optical gas imaging than for monitoring using Method 21 because the initial 

monitoring with Method 21 finds more leaks that must be repaired. As in analyses for leak 

detection and repair programs for equipment leaks, repair costs for fittings were estimated 

assuming 75 percent of the leaks can be repaired by making a simple adjustment that takes an 

average of about 15 minutes per fitting, and 25 percent require a more extensive offline repair or 

replacement. Offline repairs for gauge hatches, emergency pressure relief vents, and 
Technical Memorandum – Technology Review for Storage Vessels

January 20, 2012

32

miscellaneous valves and instruments were assumed to take an average of 4 hours. We assumed 

leaking access hatches and conservation vents would be replaced at costs of $400 and $651, 

respectively (Ellsworth, 2011a and 2011b). Reporting costs were estimated assuming 0.5 hr to 

assemble relevant records of a leaking fitting in an annual periodic report and that 5 percent of 

fittings leak each year. As a result, on average, each storage vessel has a reportable leak once 

every 2.5 years (or 0.4 reports per year). Labor rates for repair, inspection/monitoring, and 

recordkeeping/reporting are shown in Table 22. These rates are based on U.S. Department of 

Labor, Bureau of Labor Statistics labor rates (U.S. DOL, 2010). A fringe benefit loading rate of 

1.5 and an overhead and profit rate of 1.4 were multiplied by each hourly rate to obtain loaded 

rates. Recordkeeping and reporting labor rates are based on 0.5 hr of managerial time and 1 hr of 

administrative support per hr of environmental engineering time; thus, the weighted average 

labor rate per hour of engineering time is $92.72/hr.

Table 23 presents the total annual cost, emission reduction, and cost effectiveness of the various 

monitoring options. The costs in Table 23 are for a large facility. Monitoring costs for medium 

and small facilities would be slightly less, as noted in Table 21, but the estimated emissions are 

an average across all storage vessels. Therefore, the estimated cost effectiveness values would be 

higher for medium and small facilities.

Table 20. Estimated emissions from fittings on fixed roof storage vessels

Type of fitting

Number of 

fittings per 

storage 

vessel

Initial leak 

rate 

(kg/hr/fitting)

Total annual 

baseline 

emissions 

(lb/yr)

Annual 

emissions 

when 

conducting 

annual 

Method 21 

monitoring 

(lb/yr)

Annual 

emissions 

when 

conducting 

semiannual 

optical gas 

imaging 

(lb/yr)

Access hatch 1 NA 290 58 58

Gauge hatch 1 NA 2.1 0.42 0.42

Conservation vent 1 0.00170 33 6.6 6.6

Emergency 

pressure relief vent

1 0.104 2,000 400 400

Valves/instruments 4 0.00597 460 93 93

Total 2,800 560 560
Technical Memorandum – Technology Review for Storage Vessels

January 20, 2012

33

Table 21. Monitoring, repair, recordkeeping, and reporting burden and costs of different monitoring approaches for fittings 

on fixed roof storage vessels

Type of 

monitoring

MRR labor effort (hr/yr) MRR costs

Monitoring Repair Recordkeeping Reporting Total

Initial 

and 

capital 

costs ($)

Annualized 

initial and 

capital 

costs ($/yr)

Repair 

costs 

($/yr)

Annual 

monitoring 

costs ($/yr)

Annual 

recordkeeping 

and reporting 

costs ($/yr)

Total 

annual 

costs 

($/yr)

Visual 0.5 NA 1 0.025 1.5 0 0 NA 24 95 120

Method 21

 Small facility 0.67 0.38 0.5 0.2 1.7 170 24 31 32 65 150

 Med facility 0.83 0.38 0.5 0.2 1.9 180 25 31 40 65 160

 Large facility 1.0 0.38 0.5 0.2 2.1 180 26 31 48 65 170

OGI

 Small facility 0.67 0.38 0.5 0.2 2.9 130 19 31 64 110 220

 Med facility 0.83 0.38 0.5 0.2 3.2 140 20 31 79 110 240

 Large facility 1.0 0.38 0.5 0.2 3.6 150 21 31 95 110 260
Technical Memorandum – Technology Review for Storage Vessels

January 20, 2012

34

Table 22. Labor rates for monitoring, repair, recordkeeping, and reporting

(A)

Mean hourly 

labor rate1

($/hr)

(B)

Fringe 

benefit 

loading rate2

(C) 

Overhead 

and profit 

rate2

(D=AxBxC) 

Loaded wage 

rate ($/hr)

Professional Specialty and 

Technical (SOC Code: 17-2081) 39.53 1.5 1.4 83.01

Executive, Administrative and 

Managerial (SOC Code: 11-9041) 57.80 1.5 1.4 121.38

Administrative Support, Including 

Clerical (SOC Code: 43-0000) 17.31 1.5 1.4 36.35

Installation, Maintenance, and 

Repair (SOC Code: 49-0000) 22.08 1.5 1.4 47.71

Plant and System Operators, All 

(SOC Code: 51-8099) 22.72 1.5 1.4 46.37

1

Labor rates as reported by U.S. Department of Labor, Bureau of Labor Statistics for May 2009 (U.S. DOL, 2010). 2

Factors estimated to give overall loading of 110 percent as in supporting statements (OMB, 2011).

Table 23. Cost effectiveness of different monitoring techniques for fittings on fixed roof 

storage vessels

Control Option

Total 

annual cost 

($/yr)

Emission 

reduction 

versus baseline 

(tpy)

Cost 

effectiveness 

versus baseline 

($/ton)

Incremental 

cost 

effectiveness 

($/ton)

ST4a (Visual monitoring) 120 NA NA --

ST4b (Method 21 monitoring) 170 1.1 150 NA

ST4c (Optical gas imaging) 260 1.1 230 Undefined

Monitoring Equipment in Closed Vent Systems and Monitoring Control Device Operating 

Parameters

We estimated that, on average, a closed vent system conveying emissions from a storage vessel 

has six connectors, three valves, and one open-ended line. We estimated labor burden and costs 

to monitor the equipment visually, using Method 21, or using optical gas imaging. We assumed 

no reporting cost because we assumed that reporting would be required only if a facility does not 

repair leaking fittings and that all facilities would comply with such requirements. Table 24

summarizes the burden and cost of each monitoring approach.

We assumed that the typical control device will be a thermal oxidizer. The memorandum 

“Development of Monitoring Costs for the Proposed Part 65 Uniform Standards for Control 

Devices—Subpart M” estimates that the total annual cost to monitor temperature, keep records, 

and report continuous data is $8,400/yr, and the total initial cost, including costs for planning and 

the costs to purchase and install the monitor, is $9,900 (Gibson et. al., 2012). We assumed the 
Technical Memorandum – Technology Review for Storage Vessels

January 20, 2012

35

control device is dedicated to storage tank emission control and included the full cost of 

monitoring the control device in this analysis.
Technical Memorandum – Technology Review for Storage Vessels

January 20, 2012

36

Table 24. Burden and cost to inspect or monitor equipment in a closed vent system

Type of 

monitoring

Initial 

setup cost 

($)1

Annualized 

initial cost 

($/yr)2

Frequency of 

inspection or 

monitoring

Inspection 

labor (hr/yr)

Inspection or 

monitoring 

cost ($/yr)3

Recordkeeping 

labor (hr/yr)

Recordkeeping 

cost ($/yr)4

Total 

annual cost 

($/yr)

Visual 0 0 1 0.5 24 0.25 23 47

Method 21 240 34 footnote 5 N/A6 14 0.25 23 71

OGI 240 34 6 0.25 72 0.25 23 130 1

Based on $23.80 per piece of equipment, as in the analyses for equipment leaks (Hancy, 2011).

2

Capital recovery factor of 0.1098 calculated using standard OAQPS procedures assuming the closed vent system life is 15 years and using an interest rate of 7 

percent (U.S. EPA, 2002). 3

For Method 21, based on contractor fees of $2.50/connector and $1.50/valve and OEL (Hancy, 2011). For OGI, we assumed 15 minutes to conduct monitoring 

of the entire closed vent system. No rules currently specify monitoring frequency for optical gas imaging of storage vessels; therefore, the OGI monitoring 

frequency was based on maximum allowed monitoring interval in the Alternative Work Practice for equipment leaks (i.e., bimonthly) (40 CFR 63.11(c)). Labor 

rate for visual inspections and OGI assumed to be $47.71/hr, based on data in Table 22. 4

Labor rate assumed to be $92.72/hr, based on data in Table 22. 5

Assumed monitoring consistent with the frequency in the analysis for the equipment leaks Uniform Standards (i.e., once every 4 years for connectors, 2 times 

per year for valves, and 1 time per year for OEL) (Hancy, 2011).

6

Assumed monitoring is conducted by a contractor.
Technical Memorandum – Technology Review for Storage Vessels

January 20, 2012

37

Monitoring Rim Seals and Deck Fittings on IFRs and EFRs

Current rules typically require periodic visual inspections of floating roofs, and seal gaps must be 

measured for storage vessels that are equipped with EFRs. In this analysis we estimated the 

burden and cost to conduct such monitoring for a series of model storage vessels. We also 

estimated the burden and cost of alternative monitoring based on the use of either optical gas 

imaging or EPA Method 21. The results for all three monitoring approaches are presented in 

Table 25. Assumptions used in the analysis are documented in footnotes to Table 25.

Monitoring for Floating Roof Landings and Overfill

Table 26 presents an estimate of the capital and annual costs to monitor and provide warning of 

potential floating roof landings in storage vessels that are equipped with a floating roof, and 

Table 27 presents an estimate of the capital and annual costs to monitor and provide warning of 

potential overfill in any atmospheric storage vessel. Both types of monitoring are based on 

monitoring the liquid level in the storage vessel. Levels below a low set point provide warning of 

a potential floating roof landing, and levels above a high set point provide warning of potential 

overfill.

We obtained purchased equipment costs from three vendors for liquid level monitoring systems 

that can monitor both high and low levels. Some of the vendors requested that their quotes be 

maintained as confidential. Therefore, only the average purchased equipment cost is presented in 

this memorandum. The original quotes are maintained in the OAQPS CBI files (Randall, 2012a).

Other assumptions used in the analysis are documented in footnotes to the Tables.

Monitoring Pressure Vessels

We assumed that pressure vessels have the same number of fittings as on a fixed roof. 

Therefore, the monitoring, recordkeeping, and reporting burden and cost estimates in Table 21

also apply to monitoring for pressure vessels.
Technical Memorandum – Technology Review for Storage Vessels

January 20, 2012

38

Table 25. Burden and cost estimates of monitoring options for storage vessels with EFR or IFR

Model 

ID

Storage vessel 

capacity (gal)

EFR IFR

Total labor (hr/yr) Total annual cost ($/yr)1 Total labor (hr/yr) Total annual cost ($/yr)1

Visual2 OGI3

Method 

214 Visual OGI

Method 

21 Visual5 OGI6

Method 

217 Visual OGI

Method 

21

Small 30,000 (SOCMI) 5.4 3.2 3.2 350 240 240 2.6 3.2 N/A 210 240 N/A

Medium 100,000 (SOCMI)

450,000 (refinery)

6.5 3.3 3.3 400 250 250 2.7 3.3 N/A 220 250 N/A

Large 2,000,000 (SOCMI)

3,300,000 (refinery)

7.1 3.3 3.3 430 250 250 2.7 3.3 N/A 220 250 N/A

Very 

large

8,000,000 (refinery)

22,000,000 (refinery)

7.2 3.4 3.4 430 250 250 2.7 3.4 N/A 220 250 N/A

1

Labor rates were $47.71/hr for inspections and gap measurements, and $92.72/hr for recordkeeping and reporting, based on data in Table 22. 2

Activities include annual visual inspection, annual measurement of deck fitting gasket gaps, annual measurement of secondary seal gaps, measurement of 

primary seal gaps every 5 years, recordkeeping related to each inspection, and reporting of each inspection failure. We assumed 0.5 hr to conduct visual 

inspections, regardless of the storage vessel capacity. We assumed the time to measure gaps between deck fitting gaskets and the surfaces they are intended to 

seal as 0.5 hr for a small storage vessel and 1 hr for medium, large, and very large storage vessels. The supporting statement for information collection request 

related to the Consolidated Federal Air Rule for the Synthetic Organic Chemical Manufacturing Industry (in the tabular summary for NSPS subpart Ka) 

estimated an average of 5 hr to measure secondary seal gaps and 2 hr to measure primary seal gaps (OMB, 2011). For this analysis, we assumed the 5 hr and 2 hr 

estimates in the ICR were transposed. We also assumed the time would be a little less than average for small storage vessels and a little more than average for 

large storage vessels. Specifically, we assumed the time to measure primary seal gaps as 4.5 hr, 5 hr, 5.5 hr, and 6 hr for the small, medium, large, and very large 

model storage vessels, respectively. For the secondary seal, we assumed the time to measure gaps as 1.5 hr for small storage vessels, 2 hr for medium storage 

vessels, and 2.5 hr for both large and very large storage vessels. We assumed an average of 2 hr to document the results of each inspection, including calculations 

of seal gap areas. We assumed 0.5 hr to compile the applicable records of an inspection failure into a periodic report, and we assumed one percent of storage 

vessels have an inspection failure each year.

3

Same activities as for visual inspection, except seal gap measurements and deck fitting gasket measurements are replaced with annual OGI monitoring of the rim 

seal and deck fittings. We assumed 0.67 hr, 0.75 hr, 0.83 hr, and 0.92 hr to conduct OGI monitoring for small, medium, large, and very large storage vessels, 

respectively. The time was assumed to increase slightly for larger storage vessels to account for potentially more images on larger storage vessels and the time to 

climb taller tanks and walk around or across larger diameter storage vessels. 4

Assumed the time to setup, calibrate, and conduct Method 21 monitoring is the same as for OGI monitoring. Thus, the estimate burden is also the same. 5

Same as for EFR, except no rim seal gap measurements, and the deck fitting gasket measurements are every 5 years instead of annually. 6

Same level of effort and monitoring frequency as for EFR.

7

Assumed that Method 21 monitoring would not be required inside an operating storage vessel due to safety concerns.
Technical Memorandum – Technology Review for Storage Vessels

January 20, 2012

39

Table 26. Costs for floating roof landing sensor and alarm systems

Costing element Variable designations and equations Cost

Capital and other initial costs ($)

Planning1 PL = 10 hr x $92.72/hr 930

Purchased equipment cost2 PEC 850

Freight and sales tax3 FST = 0.08 x PEC 68

Installation4 I = 0.47 x (PEC + FST) 430

Total initial costs TIC = PL + PEC + FSR + I 2,280

Annual costs ($/yr)

Maintenance5 M = 0.1 x (PEC + I) 130

Capital recovery6 CR = 0.1424 x TIC 320

Property tax, insurance, and administration3 TIA = 0.04 x TIC 91

Recordkeeping7 REC = 5 hr x $92.72/hr 460

Reporting8 REP = 0.5 hr x $92.72/hr 46

Total annual cost TAC = M + CR + TIA + REC + REP 1,100 1

Assumed average of 10 hr of an engineer’s time to review rule, research options, and initiate purchasing process. 

Burdened labor rate includes 0.5 hr of management and 1 hr of administrative support per hour of engineering labor. 

Refer to Table 22 for labor rates 2

Equipment cost based on average of prices for three systems that monitor both high and low levels. Therefore, half 

of the cost attributed to floating roof landing (i.e., low level) monitoring and half attributed to overfill monitoring as 

shown in Table 27 (Randall, 2012a). 3

Factor is from EPA Air Pollution Control Cost Manual (U.S. EPA, 2002). 4

Installation factor is from “Plant Design and Economics for Chemical Engineers” (Peters et. al., 2003).

5

Assumed annual maintenance cost is equal to 10 percent of the total initial cost. Also assumed half of the cost is for 

labor and half is for materials. Thus, labor burden is $98/2/$47.71/hr = 1 hr/yr. 6

Capital recovery was calculated using procedures in EPA Air Pollution Control Cost Manual (U.S. EPA, 2002). 

Assumed monitor life of 10 years, and used interest rate of 7 percent. 7

Assumed rule would specify conditions under which landings are allowed, that emissions would have to be 

calculated for each landing, and that records documenting the circumstances for each unallowed landing would be 

required. Assumed average of 2 landings per year, one of which is unallowed. Assumed 2 hr to calculate and 

document emissions from each landing, and 1 hr to document information about the unallowed landing. Estimated 

burdened labor rate as described in footnote number 1.

8

Assumed 0.5 hr to compile records of emissions calculations and unallowed landings in periodic reports. Estimated 

burdened labor rate as described in footnote number 1.
Technical Memorandum – Technology Review for Storage Vessels

January 20, 2012

40

Table 27. Costs for overfill sensor and alarm systems

Costing element Variable designations and equations

Cost

(IFR/EFR)

Cost

(Fixed Roof)

Capital and other initial costs ($)

Planning1 PL = 10 hr x $92.72/hr 930 930

Purchased equipment cost2 PEC 850 1,700

Freight and sales tax3 FST = 0.08 x PEC 68 140

Installation4 I = 0.47 x (PEC +FST) 430 860

Total initial costs TIC = PL + PEC + FSR + I 2,280 3,600

Annual costs ($/yr)

Maintenance5 M = 0.1 x (PEC + I) 130 260

Capital recovery6 CR = 0.1424 x TIC 320 520

Property tax, insurance, and 

administration3

TIA = 0.04 x TIC 91 150

Recordkeeping7 REC = 3 hr x (1/20) x $92.72/hr 14 14

Reporting8 REP = 0.5 hr x (1/20) x $92.72/hr 2 2

Total annual cost TAC = M + CR + TIA + REC + REP 560 930 1

Assumed average of 10 hr of an engineer’s time to review rule, research options, and initiate purchasing process. 

Burdened labor rate includes 0.5 hr of management and 1 hr of administrative support per hour of engineering labor. 

Refer to Table 22 for labor rates 2

Equipment cost based on average of prices for three systems that monitor both high and low levels. For storage 

vessels with an IFR or EFR half of the cost is attributed to floating roof landing (i.e., low level) monitoring as shown 

in Table 26 and half attributed to overfill monitoring. For storage vessels with a fixed roof, the entire cost of the 

system is assigned to overfill monitoring (Randall, 2012a). 3

Factor is from EPA Air Pollution Control Cost Manual (U.S. EPA, 2002).

4

Installation factor is from “Plant Design and Economics for Chemical Engineers” (Peters et. al., 2003).

5

Assumed annual maintenance cost is equal to 10 percent of the total initial cost. Also assumed half of the cost is for 

labor and half is for materials. Thus, labor burden is $90/2/$47.71 = 0.94 hr/yr.

6

Capital recovery was calculated using procedures in EPA Air Pollution Control Cost Manual (U.S. EPA, 2002). 

Assumed monitor life of 10 years, and used interest rate of 7 percent. 7

Assumed rule would require estimate of emissions from each overfill and documentation of the cause of the overfill 

and actions taken in response to the alarm. Also assumed 1 overfill every 20 years, and 3 hr to prepare the required 

records. Estimated burdened labor rate as described in footnote number 1.

8

Assumed reporting required only in the event of an overfill (i.e., every 20 years in this analysis). Assumed 0.5 hr to 

compile records of emissions calculations and other information in periodic reports. Estimated burdened labor rate 

as described in footnote number 1.
Technical Memorandum – Technology Review for Storage Vessels

January 20, 2012

41

Impacts for Model SOCMI Facilities and Model Petroleum Refineries

We estimated the total cost and burden for several chemical manufacturing facilities and 

petroleum refineries to comply with all of the monitoring, recordkeeping, and reporting activities 

described in this memorandum. These costs and burden estimates were developed for four model 

chemical manufacturing facilities and three model petroleum refineries. Tables 28 and 29

summarize the counts of different types of storage vessels at the model facilities.

The model chemical manufacturing facilities were informed by information provided in 

responses to an information request for the MON and other available information. The model 

facilities represent a range of characteristics, but they are not intended to represent the full range 

of possible storage vessel characteristics throughout all sectors of the chemical manufacturing 

industry. 

The number, type, and sizes of storage vessels at model petroleum refineries were developed 

based on data provided by petroleum refineries in response to a recent information collection 

request (U.S. EPA, 2011). The refineries in the database were sorted into three groups based on 

the total number of storage vessels equipped with EFRs and IFRs (and that meet or exceed size 

and vapor pressure thresholds for control in current rules). Small facilities had up to 20 such 

storage vessels, medium facilities had between 20 and 40 such vessels, and large facilities had 

between 40 and 100 such storage vessels. Small facilities had an average of approximately 5 

EFRs and 5 IFRs, medium facilities had an average of approximately 18 EFRs and 12 IFRs, and 

large facilities had an average of approximately 40 EFRs and 20 IFRs. Storage vessels in the 

database that are equipped with EFR or IFR were sorted into four size categories: (1) small 

storage vessels have a capacity less than 1 million gal and were represented with a model that 

has a capacity of 450,000 gal; (2) medium storage vessels have a capacity between 1 million gal 

and 5 million gal, and were represented with a model that has a capacity of 3.3 million gal; (3) 

large storage vessels have a capacity between 5 million gal and 17 million gal, and were 

represented with a model that has a capacity of 8 million gal; and (4) very large storage vessels 

have a capacity greater than 17 million gal, and were represented with a model that has a 

capacity of 22 million gal. Nearly all of the very large storage vessels in the database had an 

EFR. The ratio of EFRs to IFRs was 5:1 for the large storage vessels, 2:1 for the medium storage 

vessels, and 0.5:1 for the small storage vessels. This information was used to estimate the 

number and distribution of IFRs and EFRs at each model facility; the ratios from the database 

were adjusted slightly so that the model counts are whole numbers and so that the total capacity 

for the models is close to the total capacity of actual storage vessels in each size range. Counts of 

fixed roof storage vessels that vent to control and pressure vessels at the model facilities were 

based on average counts of these vessels at refineries in each of the three groups of facilities 

described above. The average count of fixed roof storage vessels that vent to atmosphere was 

lower for the medium facilities in the database (i.e., those with between 20 and 40 EFRs and 

IFRs) than for small and large facilities; therefore, the average number of such storage vessels at 

all refineries in the database was used for each of the three model petroleum refineries.

Tables 30 and 31 present the monitoring, recordkeeping, and reporting costs for each type of 

monitoring activity at the model facilities. The monitoring for landings and overfill are the 

individual monitoring activities with the highest total costs. Facilities with storage vessels 

complying with a control requirement by connecting storage vessels to a closed vent system and 

control device were assumed to have a single centralized system that controls emissions from all 
Technical Memorandum – Technology Review for Storage Vessels

January 20, 2012

42

such storage vessels. The tables show the total costs for visual monitoring and manual 

measurements are very similar to the total costs for monitoring using Method 21 or optical gas 

imaging. The tables show the total cost to comply with all monitoring activities described in this 

memorandum, but the incremental cost relative to current costs will be less for existing facilities 

that are already implementing some of the monitoring to comply with current rules or for other 

reasons.

Tables 32 and 33 present the labor burden associated with each type of monitoring option for 

each of the model SOCMI facilities and petroleum refineries. The tabulated values reflect the 

annual burden per facility, and burden associated with initial setup or planning activities is noted 

in footnotes to the tables.

Table 28. Number of storage vessels at model SOCMI facilities

Model 

facility

Fixed roof 

venting to 

atmosphere1

Fixed roof 

venting to 

control

Pressure 

vessels

EFR2 IFR2

S M L S M L Total

1 2 0 0 1 0 0 1 0 0 4

2 2 2 0 0 0 0 0 0 0 4

3 6 2 1 1 2 0 2 4 0 18

4 10 4 3 1 1 4 2 2 2 29 1

Storage vessels below size and maximum true vapor pressure (MTVP) thresholds for control in current rules. 2

”S” means a small storage vessel (30,000 gal), “M” means a medium storage vessel (100,000 gal), and “L” means a 

large storage vessel (2,000,000 gal).

Table 29. Number of storage vessels at model petroleum refineries

Model 

facility

Fixed roof 

venting to 

atmosphere1

Fixed roof 

venting to 

control

Pressure 

vessels

EFR2 IFR2

S M L VL S M L Total

1 12 4 3 1 1 3 0 3 1 1 29

2 12 4 9 3 7 8 0 6 3 3 55

3 12 8 16 6 14 17 3 11 6 3 96 1

Storage vessels below size and MTVP thresholds for control in current rules. 2

”S” means a small storage vessel (450,000 gal), “M” means a medium storage vessel (3,300,000 gal), “L” means a 

large storage vessel (8,000,000 gal), and “VL” means a very large storage vessel (22,000,000 gal).
Technical Memorandum – Technology Review for Storage Vessels

January 20, 2012

43

Table 30. Total monitoring, recordkeeping, and reporting cost for storage vessels at model SOCMI facilities

Model 

facility

Type of 

monitoring1

Total annual costs ($/yr)

Pressure vessels 

and fixed roof 

venting to 

atmosphere

Fixed roof 

venting to 

control EFR IFR2

Closed 

vent 

system

Control 

device3

Floating roof 

landings 

monitor and 

alarm

Overfill 

monitor 

and alarm Total

1 Visual 240 0 350 210 0 0 2,100 1,100 4,000

Method 21 300 0 240 240 0 0 2,100 1,100 4,000

OGI 450 0 240 240 0 0 2,100 1,100 4,200

2 Visual 240 240 0 0 94 8,400 0 1,900 11,000

Method 21 300 300 0 0 140 8,400 0 1,900 11,000

OGI 450 450 0 0 260 8,400 0 1,900 11,000

3 Visual 830 240 1,200 1,300 94 8,400 9,500 6,900 28,000

Method 21 1,100 300 730 1,500 140 8,400 9,500 6,900 29,000

OGI 1,600 450 730 1,500 260 8,400 9,500 6,900 29,000

4 Visual 1,500 480 2,500 1,300 190 8,400 13,000 10,000 38,000

Method 21 2,100 640 1,500 1,500 280 8,400 13,000 10,000 38,000

OGI 3,100 960 1,500 1,500 510 8,400 13,000 10,000 39,000 1

For storage vessels with EFR or IFR, pressure vessels, fixed roof storage vessels (all), and closed vent systems. 2

As noted in Table 25, Method 21 monitoring is not likely to be required inside an operating storage vessel; therefore, the costs for the Method 21 option are 

instead based on costs for optical gas imaging. 3

Assumed to be a thermal oxidizer.
Technical Memorandum – Technology Review for Storage Vessels

January 20, 2012

44

Table 31. Total monitoring, recordkeeping, and reporting cost for storage vessels at model petroleum refineries

Model 

facility

Type of 

monitoring1

Total annual costs ($/yr)

Pressure 

vessels and 

fixed roof 

venting to 

atmosphere

Fixed roof 

venting to 

control EFR IFR2

Closed 

vent 

system

Control 

device3

Floating roof 

landings 

monitor and 

alarm

Overfill 

monitor and 

alarm Total

1 Visual 1,800 480 2,100 1,100 190 8,400 11,000 9,300 34,000

Method 21 2,400 640 1,300 1,200 290 8,400 11,000 9,300 34,000

OGI 3,600 960 1,300 1,200 510 8,400 11,000 9,300 36,000

2 Visual 2,500 480 7,700 2,600 190 8,400 32,000 21,000 74,000

Method 21 3,600 680 4,500 3,000 290 8,400 32,000 21,000 73,000

OGI 5,400 1,000 4,500 3,000 510 8,400 32,000 21,000 75,000

3 Visual 3,300 950 17,000 4,400 380 8,400 63,000 41,000 140,000

Method 21 4,700 1,400 10,000 5,000 570 8,400 63,000 41,000 130,000

OGI 7,200 2,100 10,000 5,000 1,000 8,400 63,000 41,000 140,000 1

For storage vessels with EFR or IFR, pressure vessels, fixed roof storage vessels (all), and closed vent systems. 2

As noted in Table 25, Method 21 monitoring is not likely to be required inside an operating storage vessel; therefore, the costs for the Method 21 option are 

instead based on costs for optical gas imaging.

3

Assumed to be a thermal oxidizer.
Technical Memorandum – Technology Review for Storage Vessels

January 20, 2012

45

Table 32. Total monitoring, recordkeeping, and reporting burden for storage vessels at model SOCMI facilities

Model 

facility

Type of 

monitoring1

Total annual burden (hr/yr)

Pressure vessels 

and fixed roof 

venting to 

atmosphere

Fixed roof 

venting to 

control EFR IFR2

Closed 

vent 

system3

Control 

device4

Floating roof 

landings 

monitor and 

alarm5

Overfill 

monitor 

and alarm5 Total

1 Visual 3.1 0 5.4 2.6 0 0 23 2.2 40

Method 21 3.5 0 3.2 3.2 0 0 23 2.2 40

OGI 5.8 0 3.2 3.2 0 0 23 2.2 40

2 Visual 3.1 3.1 0 0 1.5 110 0 2.2 120

Method 21 3.5 3.5 0 0 0.5 110 0 2.2 120

OGI 5.8 5.8 0 0 1.0 110 0 2.2 130

3 Visual 11 3.1 18 16 1.5 110 59 12 230

Method 21 12 3.5 9.7 19 0.5 110 59 12 230

OGI 20 5.8 9.7 19 1.0 110 59 12 240

4 Visual 20 6.1 40 16 3.0 110 78 18 290

Method 21 25 7.6 20 20 1.0 110 78 18 280

OGI 42 13 20 20 2.0 110 78 18 300 1

For storage vessels with EFR or IFR, pressure vessels, fixed roof storage vessels (all), and closed vent systems. 2

As noted in Table 25, Method 21 monitoring is not likely to be required inside an operating storage vessel; therefore, the costs for the Method 21 option are 

instead based on costs for optical gas imaging.

3

Also one-time initial burden of 23 minutes per piece of equipment for initial setup when monitoring using Method 21 or OGI. 4

Assumed to be a thermal oxidizer. Also one-time initial burden of 42 hr for planning. 5

Also one-time initial burden of 11.5 hr per storage vessel for planning.
Technical Memorandum – Technology Review for Storage Vessels

January 20, 2012

46

Table 33. Total monitoring, recordkeeping, and reporting burden for storage vessels at model petroleum refineries

Model 

facility

Type of 

monitoring1

Total annual costs ($/yr)

Pressure vessels 

and fixed roof 

venting to 

atmosphere

Fixed roof 

venting to 

control EFR IFR2

Closed 

vent 

system3

Control 

device4

Floating roof 

landings 

monitor and 

alarm5

Overfill 

monitor 

and alarm5 Total

1 Visual 23 6.1 35 14 3.0 110 65 16 270

Method 21 29 7.6 17 17 1.0 110 65 16 260

OGI 49 13 17 17 2.0 110 65 16 290

2 Visual 32 6.1 130 32 3.0 110 195 38 540

Method 21 44 8.3 61 40 1.0 110 195 38 500

OGI 75 14 61 40 2.0 110 195 38 540

3 Visual 43 12 280 54 6.0 110 390 76 970

Method 21 58 17 130 66 2.0 110 390 76 850

OGI 100 29 130 66 4.0 110 390 76 910 1

For storage vessels with EFR or IFR, pressure vessels, fixed roof storage vessels (all), and closed vent systems.

2

As noted in Table 25, Method 21 monitoring is not likely to be required inside an operating storage vessel; therefore, the costs for the Method 21 option are 

instead based on costs for optical gas imaging.

3

Also one-time initial burden of 23 minutes per piece of equipment for initial setup. 4

Assumed to be a thermal oxidizer. Also one-time initial burden of 42 hr for planning. 5

Also one-time initial burden of 11.5 hr per storage vessel for planning when monitoring using Method 21 or OGI.
Technical Memorandum – Technology Review for Storage Vessels

January 20, 2012

47

11. References

John M. Ellsworth Co., Inc. 2011a. “Shand & Jurs 2” Conservation Vent (Pressure/Vacuum)”. 

Retrieved from http://www.jmesales.com/item/130113/Shand-Jurs-Conservation-VentsPressure-Vacuum-Model-94020.aspx. Accessed November 2011.

John M. Ellsworth Co., Inc. 2011b. “Shand & Jurs 4” Aluminum Gauge Hatch Model 95021”. 

Retrieved from http://www.jmesales.com/item/136311/Shand-Jurs-Gauge-Hatches-Model95021.aspx. Accessed November 2011.

Envent. 2011. Environmental Protection Applications-Comparison of Degassing Methods. 

Retrieved from: http://www.degassingsafely.com/. Last accessed in November 2011.

Ferry, R. 2006. Emission Factors for a Ladder/Guidepole Combination. Prepared by R. Ferry, 

the TGB partnership.

Gibson, G., J. Renzaglia, M. Thomas, and P. Crawford. 2012. Memorandum from G. Gibson, J. 

Renzaglia, M. Thomas, and P. Crawford, ERG, to A. Bouchard and B. Shine, EPA/OAQPS. 

Development of Monitoring Cost Estimates for the Proposed Part 65 Uniform Standards for 

Control Devices—Subpart M. January 20, 2012. Docket No. EPA-HQ-OAR-2010-0868.

Hancy, C. 2011. Memorandum from C. Hancy, RTI International to J. Howard, EPA/OAQPS. 

Technology Review for Equipment Leaks. December 21, 2011. Docket No. EPA-HQ-OAR2010-0869.

Moore, J. 2009. Letter from J. Moore, Baker Botts, LLP, to E. Lin, TCEQ. Comments on 

Chapter 115 Degassing Rules. December 11, 2009.

Office of Management and Budget (OMB). 2011. Supporting Statement for Consolidated Air 

Rule for Synthetic Organic Chemical Manufacturing Industry. OMB Control Number 2060-

0443. Retrieved from 

http://www.reginfo.gov/public/do/PRAViewDocument?ref_nbr=201102-2060-018. Last 

accessed in November 2011.

Parrish, K. and D. Randall. 2007. Memorandum from K. Parrish and D. Randall, RTI 

International, to K. Rackley, EPA/SPPD. Final Impacts Analysis for Regulatory Options for 

Equipment Leaks of VOC in the SOCMI. October 30, 2007. Docket Item No. EPA-HQ-OAR2006-0699-0090.

Parsons, N. 2012. Memorandum from N. Parsons, EPA/OAQPS. Leaks Observed from Fixed 

Roof and Floating Roof Fittings. February 6, 2012.

Peters, Timmerhaus, and West. 2003. Plant Design and Economics for Chemical Engineers. 

Fifth Edition. McGraw Hill, New York, NY. p. 251.

Randall, D. and J. Fields. 2000. Memorandum from D. Randall and J. Fields, Midwest Research 

Institute, to MON Project File. MACT Floor, Regulatory Alternatives, and Nationwide 

Impacts for Storage Tanks at Miscellaneous Organic Chemical Manufacturing Facilities.
Technical Memorandum – Technology Review for Storage Vessels

January 20, 2012

48

July 31, 2000. Part of Hazardous Air Pollutant Emissions for Miscellaneous Organic 

Chemical Manufacturing, Supplementary Information Document for Proposed Standards. 

December 2000. Docket A-96-04, Item No. II-B-28.

Randall, D. 2012a. Memorandum from D. Randall, RTI International, to Uniform Standards 

Docket. Development of Costs for Floating Roofs, Rim Seals, Deck Fitting Controls, and 

Liquid Level Sensor/Alarm Systems. January 17, 2012.

Randall, D. 2012b. Memorandum from D. Randall, RTI International, to N. Parsons, 

EPA/OAQPS. Geodesic Dome Costs. January 17, 2012.

RTI. 2002. Petroleum Refinery Source Characterization and Emission Model for Residual Risk 

Assessment. Prepared for U.S. Environmental Protection Agency, Office of Air Quality 

Planning and Standards, Research Triangle Park, NC. EPA Contract No. 68-D6-0014. July 2, 

2002. Docket Item No. EPA-HQ-OAR-2003-0146-0083.

South Coast Air Quality Management District (SCAQMD). 2001. Further Reductions of VOC 

Emissions From Storage Tanks at Petroleum Facilities. Final Staff Report Proposed Rule 

1178. December 11, 2001. Retrieved from: http://www.aqmd.gov/hb/2001/011233a.html. 

Last accessed in November 2011.

South Coast Air Quality Management District. (SCAQMD). 2008a. Rule 1149. Storage Tank and 

Pipeline Cleaning and Degassing. Retrieved from: 

http://www.aqmd.gov/rules/reg/reg11/r1149.pdf. Last accessed in November 2011.

South Coast Air Quality Management District (SCAQMD). 2008b. Proposed Amended Rule 

1149—Storage Tank and Pipeline Cleaning and Degassing. Final Staff Report. Retrieved 

from: http://www.aqmd.gov/hb/2008/May/080534a.htm. Last accessed in November 2011.

Texas Commission on Environmental Quality (TCEQ). Chapter 115-Control of Air Pollution 

from Volatile Organic Compounds, Subchapter F: Miscellaneous Industrial Sources, 

Division 3: Degassing of Storage Tanks, Transport Vessels, and Marine Vessels. Retrieved 

from: http://www.tceq.texas.gov/assets/public/legal/rules/rules/pdflib/115f.pdf. Last accessed 

in November 2011.

U.S. Department of Labor (DOL), Bureau of Labor Statistics. 2010. Occupational Employment 

Statistics: May 2009 Occupational Employment and Wage Estimates, National Sector NAICS 

Industry-Specific Estimates. Last modified date May 14, 2010. Retrieved from: 

http://www.bls.gov/oes/2009/may/naics2_31-33.htm. Last accessed in November 2011.

U.S. EPA. 1980. Organic Chemical Manufacturing Volume 3: Storage, Fugitive, and Secondary 

Sources, Office of Air Quality Planning and Standards. EPA-450/3-80-025.

U.S. EPA. 1984. VOC Emissions from Volatile Organic Liquid Storage Tanks—Background 

Information for Proposed Standards. Office of Air Quality Planning and Standards. EPA450/3-81-003a.
Technical Memorandum – Technology Review for Storage Vessels

January 20, 2012

49

U.S. EPA. 1992. Hazardous Air Pollutant Emissions from Process Units in the Synthetic 

Organic Chemical Manufacturing Industry—Background Information for Proposed 

Standards. Volume 1C: Model Emissions Sources. Office of Air Quality Planning and 

Standards. EPA-453/D-92-016c.

U.S. EPA. 1994. Alternative Control Techniques Document: Volatile Organic Liquid Storage in 

Floating and Fixed Roof Tanks. Office of Air Quality Planning and Standards. EPA-453/R94-001.

U.S. EPA. 1995a. Compilation of Air Pollutant Emission Factors, Volume 1: Stationary Point 

and Area Sources, AP-42, Fifth Edition, Office of Air Quality Planning and Standards.

Available at http://www.epa.gov/ttn/chief/ap42/index.html.

U.S. EPA. 1995b. Protocol for Equipment Leak Emission Estimates. Office of Air Quaility 

Planning and Standards. EPA-453/R-95-017.

U.S. EPA. 2002. EPA Air Pollution Control Cost Manual Section 1 Chapter 2. Sixth Edition. 

Office of Air Quality Planning and Standards. EPA-452/B-02-001.

U.S. EPA. 2006. TANKS Emission Estimation Software, Version 4.09D. Office of Air Quality 

Planning and Standards, Technology Transfer Network, Clearinghouse for Inventories and 

Emissions Factors, Available at: http://www.epa.gov/ttn/chief/software/tanks/index.html.

U.S. EPA. 2011. Petroleum Refinery Database, Based on Refinery Information Collection 

Request (ICR) for Calendar Year 2010. March 31, 2011. Docket No. EPA-HQ-OAR-2010-

0682.
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Attachment A:  Costs for Envent’s Degassing Control Systems
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Sizing Comparison Chart for Degassing Control Systemsa

Thermal oxidizers

Initial 

flow rate 

from 

tank 

(scfm)

End of job 

flow rate 

(scfm)b

VOC 

destruction 

capacity 

(lb/hr)

Time to 

degas to 

20% LEL 

(hr)

Make-up 

fuel (LPG) 

required 

(gal/hr)

Typical 

costs ($/lb 

VOC 

destroyed)

Calculated VOC 

emission 

reduction (lb)c

Calculated 

job cost 

($)d

Calculated 

cost using 

algorithm 

($)e

1,000 scfm; low Btu unit 72 1,000 80 42 4.7 2.25 3,360 7,560

2,000 scfm; EMTOS-20 144 2,000 160 16 8.7 1.55 2,560 3,968 5,600

2,500 scfm; EMTOS-25 180 2,500 200 14 10.9 1.5 2,800 4,200 5,100

3,500 scfm; EMTOS-35 252 3,500 280 9 15.5 1.45 2,520 3,654 3,850

4,500 scfm; EMTOS-45 324 4,500 360 6 19.2 1.4 2,160 3,024 3,100

a

Data in first 7 columns of the table were obtained from Envent's website at: http://www.degassingsafely.com/. The reported data are for degassing a 

 typical 80,000 bbl gasoline storage vessel, drained dry.

b

When VOC concentration has dropped below 50% LEL.

c

Assuming system achieves VOC destruction capacity every hour of operation.

d

Calculated as product of calculated VOC emission reduction times the typical costs in $/lb VOC destroyed.

e

Calculated assuming a base fee of $2,000 per job plus a variable fee of $250/hr.
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Attachment B:  Impacts for Model Storage Vessels that are Controlled

Using an IFR
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TABLE B.1

Impacts for Control Option ST1 for model storage vessels with no guidepoles

Xylene Toluene

Methyl 

methacrylate 1,4-Dioxane Formic acid Isooctane Ethanol Trichloroethylene

Ethylene 

dichloride

Methyl ethyl 

ketone Acetonitrile

Model A

Total capital investment ($) 29,058 29,058 29,058 29,058 29,058 29,058 29,058 29,058 29,058 29,058

Total annual cost ($/yr) 5,295 5,085 5,159 5,438 4,642 5,271 3,956 4,222 4,466 5,035

Emission reduction (tpy) 0.57 0.80 0.72 0.41 1.29 0.59 2.06 1.76 1.49 0.86

Cost effectiveness ($/ton) 9,330 6,352 7,180 13,312 3,590 8,865 1,924 2,399 3,002 5,882

Model B

Total capital investment ($) 31,560 31,560 31,560 31,560 31,560 31,560 31,560 31,560 31,560 31,560

Total annual cost ($/yr) 5,393 5,029 5,153 5,630 4,273 5,355 3,063 3,530 3,969 4,951

Emission reduction (tpy) 1.01 1.42 1.28 0.75 2.26 1.06 3.60 3.08 2.60 1.51

Cost effectiveness ($/ton) 5,318 3,545 4,026 7,496 1,892 5,068 850 1,145 1,529 3,290

Model C

Total capital investment ($) 41,163 41,163 41,163 41,163 41,163 41,163 41,163 41,163 41,163 41,163 41,163

Total annual cost ($/yr) 7,299 4,649 3,275 3,742 5,538 483 4,562 (4,087) (2,290) (578) 3,089

Emission reduction (tpy) 1.03 3.97 5.50 4.98 2.99 8.60 4.07 13.68 11.68 9.78 5.71

Cost effectiveness ($/ton) 7,096 1,170 595 751 1,855 56 1,121 (299) (196) (59) 541
Model A

Total capital investment ($)

Total annual cost ($/yr)

Emission reduction (tpy)

Cost effectiveness ($/ton)

Model B

Total capital investment ($)

Total annual cost ($/yr)

Emission reduction (tpy)

Cost effectiveness ($/ton)

Model C

Total capital investment ($)

Total annual cost ($/yr)

Emission reduction (tpy)

Cost effectiveness ($/ton)

TABLE B.1

Impacts for Control Option ST1 for model storage vessels with no guidepoles

Ethyl acetate Benzene Acrylonitrile Vinyl acetate Methanol

1,1,1-

trichlorethane Methylcyclopentane Hexane Chloroform Diethylamine

Methylene 

chloride

29,058 29,058 29,058 29,058 29,058 29,058 29,058 29,058 29,058 29,058 29,058

4,084 4,265 4,553 3,749 4,997 2,074 3,365 3,043 913 2,112 (2,168)

1.91 1.71 1.39 2.29 0.90 4.15 2.71 3.07 5.44 4.10 8.86

2,136 2,491 3,271 1,641 5,565 500 1,241 992 168 515 (245)

31,560 31,560 31,560 31,560 31,560 31,560 31,560 31,560 31,560 31,560 31,560

3,306 3,619 4,118 2,727 4,885 (175) 2,071 1,520 (2,191) (102) (1,382)

3.33 2.99 2.43 3.98 1.58 7.20 4.71 5.32 9.44 7.12 8.54

992 1,212 1,694 686 3,096 (24) 440 286 (232) (14) (162)

41,163 41,163 41,163 41,163 41,163 41,163 41,163 41,163 41,163

(3,054) (1,883) 5 (5,175) 2,870 (15,960) (7,563) (9,577) (23,342)

12.53 11.23 9.13 14.89 5.95 26.87 17.54 19.78 35.07

(244) (168) 1 (348) 482 (594) (431) (484) (666)
TABLE B.2

Impacts for Control Option ST1 for model storage vessels with unslotted guidepoles

Xylene Toluene

Methyl 

methacrylate 1,4-Dioxane Formic acid Isooctane Ethanol Trichloroethylene

Ethylene 

dichloride

Methyl ethyl 

ketone Acetonitrile

Model A

Total capital investment ($) 29,058 29,058 29,058 29,058 29,058 29,058 29,058 29,058 29,058 29,058

Total annual cost ($/yr) 5,305 5,100 5,172 5,446 4,664 5,281 3,991 4,252 4,493 5,050

Emission reduction (tpy) 0.56 0.78 0.70 0.40 1.27 0.58 2.02 1.73 1.46 0.84

Cost effectiveness ($/ton) 9,532 6,500 7,347 13,632 3,677 9,058 1,980 2,464 3,081 6,020

Model B

Total capital investment ($) 31,560 31,560 31,560 31,560 31,560 31,560 31,560 31,560 31,560 31,560

Total annual cost ($/yr) 5,403 5,043 5,166 5,637 4,295 5,365 3,099 3,561 3,996 4,966

Emission reduction (tpy) 1.00 1.40 1.27 0.74 2.23 1.05 3.56 3.05 2.57 1.49

Cost effectiveness ($/ton) 5,387 3,594 4,081 7,592 1,923 5,134 870 1,168 1,557 3,338

Model C

Total capital investment ($) 41,163 41,163 41,163 41,163 41,163 41,163 41,163 41,163 41,163 41,163 41,163

Total annual cost ($/yr) 7,301 4,658 3,288 3,754 5,545 504 4,572 (4,053) (2,260) (553) 3,103

Emission reduction (tpy) 1.03 3.96 5.48 4.97 2.98 8.58 4.06 13.64 11.65 9.75 5.69

Cost effectiveness ($/ton) 7,120 1,176 600 756 1,863 59 1,127 (297) (194) (57) 545
Model A

Total capital investment ($)

Total annual cost ($/yr)

Emission reduction (tpy)

Cost effectiveness ($/ton)

Model B

Total capital investment ($)

Total annual cost ($/yr)

Emission reduction (tpy)

Cost effectiveness ($/ton)

Model C

Total capital investment ($)

Total annual cost ($/yr)

Emission reduction (tpy)

Cost effectiveness ($/ton)

TABLE B.2

Impacts for Control Option ST1 for model storage vessels with unslotted guidepoles

Ethyl acetate Benzene Acrylonitrile Vinyl acetate Methanol

1,1,1-

trichlorethane Methylcyclopentane Hexane Chloroform Diethylamine

Methylene 

chloride

29,058 29,058 29,058 29,058 29,058 29,058 29,058 29,058 29,058 29,058 29,058

4,118 4,295 4,578 3,790 5,014 2,148 3,413 3,100 1,015 2,190 (1,969)

1.88 1.68 1.36 2.24 0.88 4.06 2.66 3.01 5.32 4.02 8.64

2,195 2,560 3,355 1,692 5,701 529 1,284 1,031 191 545 (228)

31,560 31,560 31,560 31,560 31,560 31,560 31,560 31,560 31,560 31,560 31,560

3,339 3,650 4,142 2,768 4,901 (101) 2,120 1,576 (2,089) (23) (1,280)

3.30 2.95 2.40 3.93 1.56 7.12 4.65 5.26 9.33 7.03 8.43

1,013 1,237 1,723 704 3,142 (14) 456 300 (224) (3) (152)

41,163 41,163 41,163 41,163 41,163 41,163 41,163 41,163 41,163

(3,022) (1,854) 29 (5,136) 2,886 (15,889) (7,516) (9,523) (23,243)

12.50 11.20 9.11 14.84 5.93 26.79 17.49 19.72 34.96

(242) (166) 3 (346) 487 (593) (430) (483) (665)
TABLE B.3

Impacts for Control Option ST2 for model storage vessels with no guidepoles

Xylene Toluene

Methyl 

methacrylate 1,4-Dioxane Formic acid Isooctane Ethanol Trichloroethylene

Ethylene 

dichloride

Methyl ethyl 

ketone Acetonitrile

Model A

Incremental total capital investment ($) 1,750 1,750 1,750 1,750 1,750 1,750 1,750 1,750 1,750 1,750

Incremental total annual cost ($/yr) 324 314 317 330 293 323 258 270 283 310

Incremental emission reduction (tpy) 0.029 0.040 0.036 0.022 0.063 0.030 0.10 0.088 0.074 0.044

Incremental cost effectiveness ($/ton) 11,368 7,952 8,812 14,993 4,650 10,755 2,528 3,073 3,825 7,138

Model B

Incremental total capital investment ($) 1,750 1,750 1,750 1,750 1,750 1,750 1,750 1,750 1,750 1,750

Incremental total annual cost ($/yr) 324 314 317 330 293 323 258 270 283 310

Incremental emission reduction (tpy) 0.029 0.040 0.036 0.022 0.063 0.030 0.10 0.088 0.074 0.044

Incremental cost effectiveness ($/ton) 11,368 7,952 8,812 14,993 4,694 10,755 2,528 3,073 3,825 7,046

Model C

Incremental total capital investment ($) 1,750 1,750 1,750 1,750 1,750 1,750 1,750 1,750 1,750 1,750 1,750

Incremental total annual cost ($/yr) 343 324 314 317 329 292 322 256 269 282 310

Incremental emission reduction (tpy) 0.008 0.029 0.040 0.037 0.023 0.064 0.031 0.10 0.090 0.075 0.045

Incremental cost effectiveness ($/ton) 45,719 11,157 7,841 8,679 14,640 4,563 10,564 2,478 3,007 3,762 6,957
Model A

Incremental total capital investment ($)

Incremental total annual cost ($/yr)

Incremental emission reduction (tpy)

Incremental cost effectiveness ($/ton)

Model B

Incremental total capital investment ($)

Incremental total annual cost ($/yr)

Incremental emission reduction (tpy)

Incremental cost effectiveness ($/ton)

Model C

Incremental total capital investment ($)

Incremental total annual cost ($/yr)

Incremental emission reduction (tpy)

Incremental cost effectiveness ($/ton)

TABLE B.3

Impacts for Control Option ST2 for model storage vessels with no guidepoles

Ethyl acetate Benzene Acrylonitrile Vinyl acetate Methanol

1,1,1-

trichlorethane Methylcyclopentane Hexane Chloroform Diethylamine

Methylene 

chloride

1,750 1,750 1,750 1,750 1,750 1,750 1,750 1,750 1,750 1,750 1,750

264 273 286 246 309 159 225 208 91 151 (151)

0.10 0.086 0.071 0.12 0.046 0.21 0.14 0.16 0.29 0.22 0.56

2,761 3,189 4,025 2,127 6,784 753 1,615 1,320 316 682 (272)

1,750 1,750 1,750 1,750 1,750 1,750 1,750 1,750 1,750 1,750 1,750

264 273 286 246 308 159 225 208 91 151 205

0.10 0.086 0.071 0.12 0.046 0.21 0.14 0.16 0.29 0.22 0.29

2,761 3,189 4,025 2,140 6,701 753 1,615 1,320 316 682 708

1,750 1,750 1,750 1,750 1,750 1,750 1,750 1,750 1,750

262 271 285 244 308 156 223 206 88

0.10 0.087 0.072 0.12 0.047 0.22 0.14 0.16 0.29

2,705 3,119 3,956 2,076 6,619 726 1,580 1,285 302
TABLE B.4

Impacts for Control Option ST2 for model storage vessels with unslotted guidepoles

Xylene Toluene

Methyl 

methacrylate 1,4-Dioxane Formic acid Isooctane Ethanol Trichloroethylene

Ethylene 

dichloride

Methyl ethyl 

ketone Acetonitrile

Model A

Incremental total capital investment ($) 2,700 2,700 2,700 2,700 2,700 2,700 2,700 2,700 2,700 2,700

Incremental total annual cost ($/yr) 508 496 500 515 471 507 428 444 458 492

Incremental emission reduction (tpy) 0.035 0.049 0.044 0.027 0.077 0.037 0.12 0.11 0.091 0.053

Incremental cost effectiveness ($/ton) 14,736 10,223 11,360 19,079 6,152 13,879 3,468 4,165 5,061 9,278

Model B

Incremental total capital investment ($) 2,700 2,700 2,700 2,700 2,700 2,700 2,700 2,700 2,700 2,700

Incremental total annual cost ($/yr) 508 496 500 516 471 507 428 443 458 492

Incremental emission reduction (tpy) 0.035 0.048 0.044 0.027 0.077 0.037 0.12 0.11 0.091 0.053

Incremental cost effectiveness ($/ton) 14,736 10,338 11,501 19,456 6,152 13,879 3,450 4,142 5,061 9,278

Model C

Incremental total capital investment ($) 2,700 2,700 2,700 2,700 2,700 2,700 2,700 2,700 2,700 2,700 2,700

Incremental total annual cost ($/yr) 531 508 496 500 515 471 507 428 443 458 492

Incremental emission reduction (tpy) 0.009 0.035 0.048 0.044 0.027 0.077 0.037 0.12 0.11 0.091 0.053

Incremental cost effectiveness ($/ton) 59,038 14,736 10,338 11,360 19,079 6,152 13,879 3,450 4,142 5,061 9,278
Model A

Incremental total capital investment ($)

Incremental total annual cost ($/yr)

Incremental emission reduction (tpy)

Incremental cost effectiveness ($/ton)

Model B

Incremental total capital investment ($)

Incremental total annual cost ($/yr)

Incremental emission reduction (tpy)

Incremental cost effectiveness ($/ton)

Model C

Incremental total capital investment ($)

Incremental total annual cost ($/yr)

Incremental emission reduction (tpy)

Incremental cost effectiveness ($/ton)

TABLE B.4

Impacts for Control Option ST2 for model storage vessels with unslotted guidepoles

Ethyl acetate Benzene Acrylonitrile Vinyl acetate Methanol

1,1,1-

trichlorethane Methylcyclopentane Hexane Chloroform Diethylamine

Methylene 

chloride

2,700 2,700 2,700 2,700 2,700 2,700 2,700 2,700 2,700 2,700 2,700

435 445 462 413 489 309 388 367 224 297 (72)

0.12 0.10 0.086 0.14 0.056 0.26 0.17 0.19 0.35 0.27 0.68

3,750 4,262 5,373 2,953 8,733 1,203 2,301 1,910 639 1,105 (106)

2,700 2,700 2,700 2,700 2,700 2,700 2,700 2,700 2,700 2,700 2,700

435 445 462 413 489 309 388 367 224 297 363

0.12 0.10 0.086 0.14 0.056 0.26 0.17 0.19 0.35 0.27 0.35

3,771 4,262 5,373 2,953 8,733 1,203 2,301 1,910 641 1,105 1,033

2,700 2,700 2,700 2,700 2,700 2,700 2,700 2,700 2,700

435 445 462 413 489 308 387 366 224

0.12 0.10 0.086 0.14 0.056 0.26 0.17 0.19 0.35

3,750 4,262 5,373 2,953 8,733 1,199 2,292 1,902 639
TABLE B.5

Impacts for Model Petroleum Products Storage Vessels

Model Model Model Model Model Model

D E F G H I

Control Option ST1

Models with no guidepoles

 Total capital investment ($) 166,441 420,701 78,361 420,701 111,873 284,795

 Total annual cost ($/yr) (1,118) 8,869 (29,303) (87,585) (153) 9,796

 Emission reduction (tpy) 68.7 150 89.9 343 45.0 94.2

 Cost effectiveness ($/ton) (16) 59 (326) (255) (3) 104

Models with unslotted guidepoles

 Total capital investment ($) 166,441 420,701 78,361 420,701 111,873 284,795

 Total annual cost ($/yr) (1,107) 8,879 (29,246) (87,528) (136) 9,813

 Emission reduction (tpy) 68.7 150 89.8 343 45.0 94.2

 Cost effectiveness ($/ton) (16) 59 (326) (255) (3) 104

Models with slotted guidepoles

 Total capital investment ($) 166,441 420,701 78,361 420,701 111,873 284,795

 Total annual cost ($/yr) (1,103) 8,884 (29,224) (87,506) (129) 9,820

 Emission reduction (tpy) 68.7 150 89.8 343 45.0 94.2

 Cost effectiveness ($/ton) (16) 59 (326) (255) (3) 104

Control Option ST2

Models with no guidepoles

 Incremental total capital investment ($) 5,050 13,300 1,750 13,300 4,500 10,000

 Incremental total annual cost ($/yr) 953 2,531 205 1,977 816 1,836

 Incremental emission reduction (tpy) 0.11 0.25 0.29 1.36 0.17 0.32

 Incremental cost effectiveness ($/ton) 8,590 10,003 706 1,452 4,884 5,676

Models with unslotted guidepoles

 Incremental total capital investment ($) 6,000 14,250 2,700 14,250 5,450 10,950

 Incremental total annual cost ($/yr) 1,138 2,715 363 2,136 996 2,017

 Incremental emission reduction (tpy) 0.12 0.26 0.35 1.42 0.19 0.34

 Incremental cost effectiveness ($/ton) 9,286 10,264 1,033 1,501 5,354 5,888

Models with slotted guidepoles

 Incremental total capital investment ($) 6,400 14,650 3,100 14,650 5,850 11,350

 Incremental total annual cost ($/yr) 1,215 2,793 433 2,205 1,073 2,093

 Incremental emission reduction (tpy) 0.13 0.27 0.37 1.44 0.19 0.35

 Incremental cost effectiveness ($/ton) 9,608 10,401 1,163 1,527 5,587 6,007
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Attachment C:  Impacts for Model Storage Vessels that are Controlled

Using an EFR
[this page intentionally left blank]
TABLE C.1

Impacts for Control Option ST5 for model storage vessels with unslotted guidepoles

Xylene Toluene MM Formic acid Isooctane MEK Benzene MeOH Hexane Chloroform

Model A

Total capital investment ($) 11,244 11,244 11,244 11,244 11,244 11,244 11,244 11,244 11,244 11,244

Total annual cost ($/yr) 1,654 1,565 1,518 1,592 1,420 1,373 1,323 1,492 1,019 473

Emission reduction (tpy) 0.034 0.13 0.19 0.10 0.29 0.35 0.40 0.21 0.74 1.35

Cost effectiveness ($/ton) 48,639 11,764 8,204 15,453 4,829 3,968 3,300 6,971 1,379 352

Model B

Total capital investment ($) 13,006 13,006 13,006 13,006 13,006 13,006 13,006 13,006 13,006

Total annual cost ($/yr) 1,910 1,797 1,737 1,831 1,613 1,554 1,491 1,704 1,106

Emission reduction (tpy) 0.043 0.17 0.23 0.13 0.37 0.44 0.51 0.27 0.94

Cost effectiveness ($/ton) 44,408 10,662 7,408 14,029 4,330 3,543 2,939 6,276 1,181

Model C

Total capital investment ($) 18,170 18,170 18,170 18,170 18,170 18,170 18,170 18,170 18,170

Total annual cost ($/yr) 2,656 2,467 2,367 2,524 2,157 2,310 2,057 1,952 1,303

Emission reduction (tpy) 0.073 0.28 0.39 0.22 0.63 0.46 0.74 0.86 1.58

Cost effectiveness ($/ton) 36,385 8,701 5,999 11,500 3,438 5,056 2,783 2,282 827
TABLE C.2

Impacts for Control Option ST5 for model storage vessels with slotted guidepoles

Xylene Toluene MM Formic acid Isooctane MEK Benzene MeOH Hexane Chloroform

Model A

Total capital investment ($) 11,244 11,244 11,244 11,244 11,244 11,244 11,244 11,244 11,244 11,244

Total annual cost ($/yr) 1,653 1,565 1,518 1,592 1,420 1,373 1,323 1,492 1,019 473

Emission reduction (tpy) 0.035 0.133 0.185 0.103 0.294 0.346 0.401 0.214 0.739 1.35

Cost effectiveness ($/ton) 47,921 11,764 8,204 15,453 4,829 3,968 3,300 6,971 1,379 352

Model B

Total capital investment ($) 13,006 13,006 13,006 13,006 13,006 13,006 13,006 13,006 13,006

Total annual cost ($/yr) 1,910 1,797 1,737 1,831 1,613 1,554 1,491 1,704 1,106

Emission reduction (tpy) 0.043 0.169 0.235 0.131 0.373 0.439 0.508 0.272 0.936

Cost effectiveness ($/ton) 44,408 10,662 7,408 14,029 4,323 3,543 2,935 6,276 1,181

Model C

Total capital investment ($) 18,170 18,170 18,170 18,170 18,170 18,170 18,170 18,170 18,170

Total annual cost ($/yr) 2,657 2,467 2,366 2,524 2,157 2,310 2,059 1,952 1,303

Emission reduction (tpy) 0.073 0.28 0.40 0.22 0.63 0.46 0.74 0.86 1.58

Cost effectiveness ($/ton) 36,642 8,701 5,991 11,500 3,434 5,056 2,796 2,282 826
TABLE C.3

Impacts for Control Option ST6 for model storage vessels with unslotted guidepoles

Xylene Toluene MM Formic acid Isooctane MEK Benzene MeOH Hexane Chloroform

Model A

Incremental total capital investment ($) 1,350 1,350 1,350 1,350 1,350 1,350 1,350 1,350 1,350 1,350

Incremental total annual cost ($/yr) 94 (334) (545) (213) (985) (1,195) (1,416) (663) (2,779) (5,228)

Incremental emission reduction (tpy) 0.154 0.60 0.83 0.46 1.32 1.55 1.80 0.96 3.31 6.03

Incremental cost effectiveness ($/ton) 612 (561) (656) (462) (747) (770) (788) (690) (839) (866)

Model B

Incremental total capital investment ($) 1,350 1,350 1,350 1,350 1,350 1,350 1,350 1,350 1,350

Incremental total annual cost ($/yr) 65 (334) (545) (213) (985) (1,195) (1,416) (663) (2,779)

Incremental emission reduction (tpy) 0.153 0.60 0.83 0.46 1.32 1.55 1.80 0.96 3.31

Incremental cost effectiveness ($/ton) 422 (560) (656) (462) (747) (770) (788) (690) (839)

Model C

Incremental total capital investment ($) 1,350 1,350 1,350 1,350 1,350 1,350 1,350 1,350 1,350

Incremental total annual cost ($/yr) 65 (334) (545) (213) (985) (604) (1,168) (1,502) (2,779)

Incremental emission reduction (tpy) 0.153 0.60 0.83 0.46 1.32 0.90 1.52 1.89 3.31

Incremental cost effectiveness ($/ton) 422 (561) (656) (462) (747) (674) (767) (793) (839)
TABLE C.4

Impacts for Control Option ST6 for model storage vessels with slotted guidepoles

Xylene Toluene MM Formic acid Isooctane MEK Benzene MeOH Hexane Chloroform

Model A

Incremental total capital investment ($) 2,650 2,650 2,650 2,650 2,650 2,650 2,650 2,650 2,650 2,650

Incremental total annual cost ($/yr) 186 (544) (914) (332) (1,687) (2,056) (2,443) (1,121) (4,836) (9,133)

Incremental emission reduction (tpy) 0.27 1.05 1.46 0.81 2.32 2.73 3.16 1.69 5.81 10.6

Incremental cost effectiveness ($/ton) 694 (521) (628) (410) (729) (754) (774) (665) (832) (863)

Model B

Incremental total capital investment ($) 3,250 3,250 3,250 3,250 3,250 3,250 3,250 3,250 3,250

Incremental total annual cost ($/yr) 245 (455) (824) (242) (1,597) (1,966) (2,353) (1,031) (4,746)

Incremental emission reduction (tpy) 0.27 1.05 1.46 0.81 2.32 2.73 3.16 1.69 5.81

Incremental cost effectiveness ($/ton) 910 (435) (566) (299) (690) (721) (746) (611) (816)

Model C

Incremental total capital investment ($) 5,350 5,350 5,350 5,350 5,350 5,350 5,350 5,350 5,350

Incremental total annual cost ($/yr) 560 (140) (509) 72 (1,282) (643) (1,618) (2,146) (4,431)

Incremental emission reduction (tpy) 0.27 1.05 1.46 0.81 2.32 1.61 2.69 3.27 5.81

Incremental cost effectiveness ($/ton) 2,085 (134) (350) 89 (554) (602) (655) (401) (762)
TABLE C.5

Impacts for Control Option ST7 for model storage vessels with unslotted guidepoles

Xylene Toluene MM Formic acid Isooctane MEK Benzene MeOH Hexane Chloroform

Model A

Incremental total capital investment ($) 26,573 26,573 26,573 26,573 26,573 26,573 26,573 26,573 26,573 26,573

Incremental total annual cost ($/yr) 3,944 3,956 3,947 3,962 3,926 3,917 3,908 3,941 3,845 3,735

Incremental emission reduction (tpy) 0.006 0.027 0.0375 0.021 0.060 0.0705 0.081 0.0435 0.15 0.273

Incremental cost effectiveness ($/ton) 657,404 146,523 105,245 188,644 65,440 55,560 48,241 90,604 25,636 13,680

Model B

Incremental total capital investment ($) 28,959 28,959 28,959 28,959 28,959 28,959 28,959 28,959 28,959

Incremental total annual cost ($/yr) 4,331 4,309 4,298 4,316 4,275 4,264 4,252 4,292 4,181

Incremental emission reduction (tpy) 0.0080 0.0315 0.044 0.0245 0.0695 0.082 0.095 0.0505 0.175

Incremental cost effectiveness ($/ton) 541,331 136,809 97,687 176,155 61,515 52,001 44,762 84,998 23,959

Model C

Incremental total capital investment ($) 39,774 39,774 39,774 39,774 39,774 39,774 39,774 39,774 39,774

Incremental total annual cost ($/yr) 5,947 5,917 5,900 5,926 5,867 5,850 5,833 5,891 5,728

Incremental emission reduction (tpy) 0.012 0.046 0.064 0.036 0.10 0.12 0.14 0.074 0.26

Incremental cost effectiveness ($/ton) 495,597 130,044 92,193 164,599 57,799 48,957 42,118 79,613 22,419
TABLE C.6

Impacts for Control Option ST7 for model storage vessels with slotted guidepoles

Xylene Toluene MM Formic acid Isooctane MEK Benzene MeOH Hexane Chloroform

Model A

Incremental total capital investment ($) 26,573 26,573 26,573 26,573 26,573 26,573 26,573 26,573 26,573 26,573

Incremental total annual cost ($/yr) 3,939 3,939 3,923 3,948 3,889 3,872 3,856 3,914 3,751 3,562

Incremental emission reduction (tpy) 0.0115 0.046 0.064 0.0355 0.102 0.12 0.139 0.074 0.255 0.465

Incremental cost effectiveness ($/ton) 342,524 85,631 61,294 111,225 38,316 32,270 27,840 52,890 14,710 7,669

Model B

Incremental total capital investment ($) 28,959 28,959 28,959 28,959 28,959 28,959 28,959 28,959 28,959

Incremental total annual cost ($/yr) 4,327 4,293 4,275 4,303 4,237 4,220 4,201 4,264 4,086

Incremental emission reduction (tpy) 0.013 0.050 0.070 0.039 0.11 0.13 0.15 0.082 0.28

Incremental cost effectiveness ($/ton) 346,128 85,857 61,069 110,327 38,004 32,213 27,638 52,325 14,592

Model C

Incremental total capital investment ($) 39,774 39,774 39,774 39,774 39,774 39,774 39,774 39,774 39,774

Incremental total annual cost ($/yr) 5,943 5,899 5,877 5,913 5,829 5,782 5,863 5,806 5,634

Incremental emission reduction (tpy) 0.017 0.065 0.0905 0.0505 0.144 0.196 0.105 0.169 0.36

Incremental cost effectiveness ($/ton) 349,569 90,761 64,934 117,080 40,619 29,576 55,843 34,354 15,650
TABLE C.7

Impacts for Model Petroleum Products Storage Vessels

Model Model Model Model Model Model

D E F G H I

Control Option ST5

Models with unslotted guidepoles

 Total capital investment ($) 44,889 67,956 29,897 67,956 36,685 57,461

 Total annual cost ($/yr) 5,712 8,366 1,448 455 4,247 6,249

 Emission reduction (tpy) 2.02 3.63 6.06 19.45 2.50 4.72

 Cost effectiveness ($/ton) 2,822 2,307 239 23 1,701 1,325

Models with slotted guidepoles

 Total capital investment ($) 44,889 67,956 29,897 67,956 36,685 57,461

 Total annual cost ($/yr) 5,712 8,366 1,448 455 4,247 6,249

 Emission reduction (tpy) 2.02 3.63 6.06 19.45 2.50 4.72

 Cost effectiveness ($/ton) 2,822 2,307 239 23 1,701 1,325

Control Option ST6

Models with unslotted guidepoles

 Incremental total capital investment ($) 1,350 1,350 1,350 1,350 1,350 1,350

 Incremental total annual cost ($/yr) (365) (365) (2,838) (2,838) (730) (730)

 Incremental emission reduction (tpy) 1.13 1.13 6.08 6.08 1.86 1.86

 Incremental cost effectiveness ($/ton) (322) (322) (467) (467) (392) (392)

Models with slotted guidepoles

 Incremental total capital investment ($) 6,400 6,400 6,400 6,400 6,400 6,400

 Incremental total annual cost ($/yr) (36) (36) (4,377) (4,377) (677) (677)

 Incremental emission reduction (tpy) 1.99 1.99 10.67 10.67 3.27 3.27

 Incremental cost effectiveness ($/ton) (18) (18) (410) (410) (207) (207)

Control Option ST7

Models with unslotted guidepoles

 Incremental total capital investment ($) 236,086 688,797 92,161 688,797 145,063 443,192

 Incremental total annual cost ($/yr) 35,214 102,902 13,336 101,696 21,542 66,033

 Incremental emission reduction (tpy) 0.301 0.552 0.939 2.964 0.376 0.710

 Incremental cost effectiveness ($/ton) 116,990 186,417 14,202 34,310 57,292 93,004

Models with slotted guidepoles

 Incremental total capital investment ($) 236,086 688,797 92,161 688,797 145,063 443,192

 Incremental total annual cost ($/yr) 35,196 102,884 13,239 101,600 21,512 66,003

 Incremental emission reduction (tpy) 0.337 0.588 1.133 3.157 0.436 0.770

 Incremental cost effectiveness ($/ton) 104,439 174,973 11,690 32,182 49,396 85,774
[this page intentionally left blank]
Attachment D: Nationwide Impacts for Storage Vessels at Petroleum Refineries
[this page intentionally left blank]
Model size2

Model vapor 

pressure3

Nationwide 

number of Tanks4

Nationwide VOC 

emissions 

reduction (tpy)

Nationwide total 

capital investment 

($)5

Nationwide total 

annual costs 

without VOC 

recovery credit 

($/yr)

Nationwide 

VOC credit 

$/yr6

Nationwide total 

annual costs with 

VOC recovery credit 

($/yr)

External floating roof

Slotted guidepole Small low 13 35.7 83,200 12,463 17,843 (5,379)

Slotted guidepole Small medium 19 136 121,600 18,216 68,025 (49,809)

Slotted guidepole Small high 19 257 121,600 18,216 128,393 (110,177)

Slotted guidepole Small very high 7 151 44,800 6,711 75,460 (68,749)

Slotted guidepole Medium low 23 63.2 147,200 22,051 31,579 (9,528)

Slotted guidepole Medium medium 84 602 537,600 80,532 300,804 (220,272)

Slotted guidepole Medium high 94 1,271 601,600 90,120 635,323 (545,203)

Slotted guidepole Medium very high 60 1,293 384,000 57,523 646,275 (588,752)

Slotted guidepole Large low 4 11.0 25,600 3,835 5,487 (1,652)

Slotted guidepole Large medium 42 87.4 268,800 40,266 43,680 (3,414)

Slotted guidepole Large high 55 771 352,000 52,730 385,688 (332,958)

Slotted guidepole Large very high 22 492 140,800 21,092 245,960 (224,868)

Slotted guidepole Extra Large low 0 0 0 0 0 0

Slotted guidepole Extra Large medium 10 71.6 94,000 14,081 35,800 (21,719)

Slotted guidepole Extra Large high 3 40.6 28,200 4,224 20,276 (16,052)

Slotted guidepole Extra Large very high 1 21.6 9,400 1,408 10,775 (9,367)

Solid guidepole Small low 37 56.5 49,950 7,483 28,259 (20,776)

Solid guidepole Small medium 59 235.1 79,650 11,932 117,572 (105,641)

Solid guidepole Small high 31 233.2 41,850 6,269 116,599 (110,330)

Solid guidepole Small very high 17 204.2 22,950 3,438 102,085 (98,647)

Solid guidepole Medium low 58 88.7 78,300 11,729 44,327 (32,597)

Solid guidepole Medium medium 220 877 297,000 44,491 438,460 (393,969)

Solid guidepole Medium high 174 1,309 234,900 35,188 654,458 (619,269)

Solid guidepole Medium very high 90 1,079 121,500 18,201 539,663 (521,462)

Solid guidepole Large low 19 29.0 25,650 3,842 14,488 (10,645)

Solid guidepole Large medium 78 92.8 105,300 15,774 46,410 (30,636)

Solid guidepole Large high 42 337 56,700 8,494 168,630 (160,136)

Solid guidepole Large very high 14 179 18,900 2,831 89,670 (86,839)

Solid guidepole Extra Large low 1 1.53 1,350 202 764 (562)

Solid guidepole Extra Large medium 12 47.8 16,200 2,427 23,910 (21,483)

Solid guidepole Extra Large high 6 45.1 8,100 1,213 22,568 (21,354)

Solid guidepole Extra Large very high 5 60.0 6,750 1,011 30,000 (28,989)

Controlled guidepole Small low 23 0.98 9,200 1,378 489 889

Controlled guidepole Small medium 42 4.73 16,800 2,517 2,363 154

Controlled guidepole Small high 18 3.87 7,200 1,079 1,935 (856)

Controlled guidepole Small very high 23 7.94 9,200 1,378 3,968 (2,589)

Controlled guidepole Medium low 52 2.26 20,800 3,116 1,131 1,985

Controlled guidepole Medium medium 154 17.2 61,600 9,228 8,624 604

Type of storage vessel1
Model size2

Model vapor 

pressure3

Nationwide 

number of Tanks4

Nationwide VOC 

emissions 

reduction (tpy)

Nationwide total 

capital investment 

($)5

Nationwide total 

annual costs 

without VOC 

recovery credit 

($/yr)

Nationwide 

VOC credit 

$/yr6

Nationwide total 

annual costs with 

VOC recovery credit 

Type of storage vessel ($/yr) 1

Controlled guidepole Medium high 195 41.4 78,000 11,684 20,719 (9,034)

Controlled guidepole Medium very high 202 69.2 80,800 12,104 34,593 (22,489)

Controlled guidepole Large low 18 0.72 7,200 1,079 360 719

Controlled guidepole Large medium 94 9.87 37,600 5,632 4,935 697

Controlled guidepole Large high 97 69.8 38,800 5,812 34,920 (29,108)

Controlled guidepole Large very high 70 81.2 28,000 4,194 40,600 (36,406)

Controlled guidepole Extra Large low 6 0.26 2,400 360 132 228

Controlled guidepole Extra Large medium 22 2.48 8,800 1,318 1,238 81

Controlled guidepole Extra Large high 19 4.04 7,600 1,138 2,019 (880)

Controlled guidepole Extra Large very high 8 2.80 3,200 479 1,400 (921)

Totals for External Floating Roofs: 2,362 10,500 4,542,650 680,000 5,249,000 (4,568,000)

Internal floating roof

Slotted guidepole Small low 39 4.19 120,900 18,111 2,096 16,015

Slotted guidepole Small medium 75 20.7 232,500 34,829 10,350 24,479

Slotted guidepole Small high 43 22.3 133,300 19,968 11,126 8,842

Slotted guidepole Small very high 32 26.6 99,200 14,860 13,280 1,580

Slotted guidepole Medium low 22 4.29 152,900 22,904 2,145 20,759

Slotted guidepole Medium medium 68 34.7 472,600 70,795 17,340 53,455

Slotted guidepole Medium high 61 59.2 423,950 63,508 29,585 33,923

Slotted guidepole Medium very high 35 54.3 243,250 36,439 27,125 9,314

Slotted guidepole Large low 8 2.69 104,000 15,579 1,344 14,235

Slotted guidepole Large medium 13 11.5 169,000 25,316 5,753 19,564

Slotted guidepole Large high 23 38.5 299,000 44,790 19,263 25,528

Slotted guidepole Large very high 20 52.7 260,000 38,948 26,350 12,598

Slotted guidepole Extra Large low 0 0 0 0 0 0

Slotted guidepole Extra Large medium 2 2.99 45,800 6,861 1,495 5,366

Slotted guidepole Extra Large high 3 8.45 68,700 10,291 4,223 6,069

Slotted guidepole Extra Large very high 0 0 0 0 0 0

Solid guidepole Small low 54 5.18 145,800 21,841 2,592 19,249

Solid guidepole Small medium 89 22.0 240,300 35,997 10,992 25,005

Solid guidepole Small high 45 20.3 121,500 18,201 10,125 8,076

Solid guidepole Small very high 25 18.6 67,500 10,112 9,313 799

Solid guidepole Medium low 38 7.03 248,900 37,285 3,515 33,770

Solid guidepole Medium medium 89 43.2 582,950 87,326 21,583 65,743

Solid guidepole Medium high 68 62.2 445,400 66,721 31,110 35,611

Solid guidepole Medium very high 31 45.3 203,050 30,417 22,630 7,787

Solid guidepole Large low 3 0.98 37,800 5,662 488 5,175

Solid guidepole Large medium 8 6.84 100,800 15,100 3,420 11,680
Model size2

Model vapor 

pressure3

Nationwide 

number of Tanks4

Nationwide VOC 

emissions 

reduction (tpy)

Nationwide total 

capital investment 

($)5

Nationwide total 

annual costs 

without VOC 

recovery credit 

($/yr)

Nationwide 

VOC credit 

$/yr6

Nationwide total 

annual costs with 

VOC recovery credit 

Type of storage vessel ($/yr) 1

Solid guidepole Large high 6 9.72 75,600 11,325 4,860 6,465

Solid guidepole Large very high 2 5.17 25,200 3,775 2,585 1,190

Solid guidepole Extra Large low 0 0 0 0 0 0

Solid guidepole Extra Large medium 0 0 0 0 0 0

Solid guidepole Extra Large high 0 0 0 0 0 0

Solid guidepole Extra Large very high 0 0 0 0 0 0

Controlled guidepole Small low 28 2.10 49,000 7,340 1,050 6,290

Controlled guidepole Small medium 74 14.1 129,500 19,399 7,030 12,369

Controlled guidepole Small high 58 20.9 101,500 15,205 10,440 4,765

Controlled guidepole Small very high 40 23.2 70,000 10,486 11,600 (1,114)

Controlled guidepole Medium low 24 3.96 134,400 20,133 1,980 18,153

Controlled guidepole Medium medium 72 31.0 403,200 60,399 15,480 44,919

Controlled guidepole Medium high 71 57.5 397,600 59,560 28,755 30,805

Controlled guidepole Medium very high 59 75.2 330,400 49,494 37,613 11,881

Controlled guidepole Large low 1 0.31 11,650 1,745 153 1,593

Controlled guidepole Large medium 5 4.00 58,250 8,726 2,000 6,726

Controlled guidepole Large high 3 4.50 34,950 5,236 2,250 2,986

Controlled guidepole Large very high 20 48.2 233,000 34,903 24,100 10,803

Controlled guidepole Extra Large low 0 0 0 0 0 0

Controlled guidepole Extra Large medium 0 0 0 0 0 0

Controlled guidepole Extra Large high 0 0 0 0 0 0

Controlled guidepole Extra Large very high 0 0 0 0 0 0

Totals for Internal Floating Roofs: 1,357 874 7,073,000 1,060,000 437,100 622,500

Nationwide Totals: 3,719 11,400 11,616,000 1,740,000 5,686,000 (3,946,000)

1

2

3

4

5

6

Assumed all storage vessels need additional deck fitting controls as specified in Tables 4 and 6 for Control Options ST2 and ST6, except additional guidepole controls are not included for 

storage vessels that currently have controlled guidepoles. Costs for these controls were based on the information in Tables 12 and 13 of this memorandum.

Assumed a VOC recovery credit of $500/ton.

Assumed all solid guidepoles currently are equipped with an ungasketed deck cover. Controlled guidepoles are slotted guidepoles that meet regulatory requirements like those in 40 CFR 

part 63, subpart WW.

The small model represents storage vessels with capacities less than 1 million gallons, the medium model represents storage vessels with capacities of 1 million gallons to less than 6 million 

gallons, the large model represents storage vessels with capacities of at least 6 million gallons to less than 17 million gallons, and the very large model represents storage vessels with 

capacities of 17 million gallons or greater. The model sizes are 450,000 gal; 3,300,000 gal; 8,000,000 gal; and 22,000,000 gal.

Model vapor pressures are based on methyl ethyl ketone, gasoline (RVP 6), gasoline (RVP 10), and gasoline (RVP 14). The low, medium, high, and very high models represent materials 

with vapor pressures of 0.7 psia to 1.9 psia, >1.9 psia to 5 psia, >5 psia to 8 psia, and >8 psia, respectively.

The number of storage vessels meeting the model guidepole, size, and vapor pressure criteria are based on information in the Refineries ICR database (U.S. EPA, 2011). This analysis 

excluded wastewater storage vessels and storage vessels for which no vapor pressure was reported. Storage vessels without a reported size were represented with the appropriate small 

model storage vessel.