1

MEMORANDUM | 24 March 2009

TO Cho-Yi Kwan and Timothy Roberts, EPA

FROM Cynthia Manson, Todd Chamoy, and Mark Ewen, Industrial Economics, Inc. 

SUBJECT

Detailed Assessment of UST Universe by Tank Purpose and Design

(WA 1-25, Task 6)

EPA’s Office of Underground Storage Tanks (OUST) is currently exploring the 

possibility of revising existing regulations associated with certain types of underground 

storage tank (UST) systems and equipment. Under Executive Order 12866, Under the 

requirements of the Regulatory Flexibility Act (RFA) of 1980, as amended by the Small 

Business Regulatory Enforcement Fairness Act of 1996 (SBREFA) and Executive Order 

(EO) 13272, entitled “Proper Consideration of Small Entities in Agency Rulemaking,”

agencies must consider the potential impact of regulations on small businesses, small 

governmental jurisdictions, and small organizations during the development of their rules.

This memorandum describes the underground storage tank universe with estimates of the

number of facilities and tanks, and the purposes of those tanks, in order to inform future 

small business and other regulatory analyses.

This memo classifies the universe of USTs into the following categories of tank purpose 

and design:

Retail motor fuel (i.e., service station) tanks;

Airport hydrant systems;

Emergency generator tanks;

Field-constructed tanks;

Non-retail fuel and other petroleum product tanks; and

Tanks storing used oil and non-petroleum substances (e.g., hazardous chemicals).

We will also include a discussion of USTs found on Tribal lands, including privatelyowned USTs as well as those owned by Tribal governments.

This section describes the regulated universe of USTs. We first distribute the known 

USTs by type or purpose of tank using two possible methodologies that provide a range 

of values. Next, we examine whether data on the contents of the tanks will help further 

refine these estimates. Finally, we conclude with a discussion of the industries using tanks 

on Tribal lands.

INTRODUCTION AND 

BACKGROUND 

THE UST UNIVERSE
2

TYPES AND PURPOSES O F USTS

Potential OUST regulatory revisions may affect one or more of six general categories of 

USTs according to the design and/or purpose of the tank:

Tanks storing motor fuel for retail sale at service (i.e., gas) stations;

Tanks (both storage tanks and hydrants) that are part of stationary airport hydrant 

refueling systems;

Field-constructed tanks (large scale storage for various purposes);

Tanks storing fuel to provide emergency generator support, including emergency 

generator tanks at nuclear power plants;

Tanks storing non-retail motor fuel for vehicles and fleets, and petroleum for other 

non-emergency purposes (e.g., lubricating or motor oil); and 

Tanks storing used oil and non-petroleum substances (e.g., petroleum additives, 

hazardous substances).

According to EPA data, 623,319 active underground storage tanks were reported in the 50 

states and on Tribal lands at the end of fiscal year 2008.

1 To distribute this total across 

the six categories of tank purpose we build on two previous research efforts. In the first 

analysis, IEc and PCCI estimated the distribution of USTs by state based on data from the 

Energy Information Administration (EIA), the EPA, and other sources.

2

Separately, E2

Incorporated (E2) analyzed state databases to determine the national distribution of tanks 

by industry sector.

3 We refine both of these analyses to include more specific data on the 

number of tanks from EPA, and more recent data on the number of motor fuel retailers 

(service stations) from National Petroleum News (NPN), and to distribute other tanks 

among their various uses.4

Exhibit 1 lists our two best estimates of tanks distributed by purpose, based on the 

refined PCCI and E2 methodologies. Both of these estimates indicate that motor fuel 

retailers account for the majority of underground storage tanks in the United States, 

although the estimates of the number of retail motor fuel tanks differ significantly. 

We extrapolate data from a set of state databases to estimate the number of emergency 

generator tanks and tanks storing used oil and non-petroleum products, and assume that 

the remaining tanks are used to provide non-retail fuel for vehicles and fleets (e.g., 

government-owned vehicles, car dealerships, school bus operators) and other large-scale, 

non-emergency petroleum product storage.

We have reliable estimates of the number of field-constructed tanks, nuclear emergency 

generator tanks, and airport hydrant refueling systems from the Federal Aviation 

Administration (FAA) and the Defense Energy Support Center (DESC).5 It appears that 

 

1

EPA, “FY2008 End-of-Year Activity Report,” November 20, 2008, as viewed at 

http://www.epa.gov/swerust1/cat/ca_08_34.pdf on February 12, 2009. This number includes tanks designated as 

“temporarily closed.”

2

See Industrial Economics, “Preliminary Assessment and Scoping of Data Related to Potential Revisions to the UST 

Regulations; Tasks 2-4, Work Assignment 1-25,” November 20, 2008, and appendices.

3

See E2, Incorporated, “Delivery Prohibition - Draft Preliminary Analyses,” December 18, 2006.

4

"Market Facts 2008 Overview," NPN Magazine July/August 2008, p.26.

5

PCCI identified 241 hydrant systems; 201 at Department of Defense facilities and 40 at commercial airports. PCCI’s 

research could not identify any operating field-constructed tanks except for 239 operated by the Department of Defense. Of 

these, approximately 75 percent (179) are located in states that require notification; these 179 tanks are therefore included 

in the non-retail tanks. The remaining 25 percent of field-constructed tanks (60 tanks) are located in states that defer this 
3

most commercial airport hydrant refueling systems employ aboveground storage tanks, 

and we assume that any military airport hydrant systems employing underground tanks 

are included in the non-retail fuel tanks.6 Airport hydrant system tanks are not, therefore, 

identified separately in Exhibit 1, but are reflected, to the extent that they have 

underground tanks, in non-retail fuel and other oil product tanks.

EXHIBIT 1 DISTRIBUTION OF TANKS BY USE

USE CATEGORY

NUMBER OF 

TANKS (REFINED 

PCCI 

METHODOLOGY)

PERCENTAGE

OF TOTAL

NUMBER OF 

TANKS (REFINED 

E

2

METHODOLOGY)

PERCENTAGE 

OF TOTAL

Retail Motor Fuel (Service Station) 

Tanks 437,1541

70.1% 480,613277.1%

Field-Constructed Tanks (FCTs)3239 0% 239 0%

Nuclear Emergency Generator Tanks 

(EGTs)4 104 0% 104 0%

Other Emergency Generator Tanks 

(EGTs)5 18,500 3.0% 18,410 3.0%

Other (Used Oil and Non-Petroleum 

Product) Tanks6 24,318 3.0% 23,238 3.7%

Non-Retail Fuel and Other Oil Product 

Tanks7 143,004 22.9% 100,715 16.2%

Total Active USTs8623,319 100% 623,319 100%

Notes:

1. Equal to 2.65 times the 161,768 retail motor fuel locations (service stations) reported by NPN, adjusted downwards in 

states where that value would exceed the total number of tanks. Also adjusted for more precise state data available in 

state and Tribal land UST databases.

2. Equal to 3.13 times 161,768 retail motor fuel locations reported by NPN, adjusted downwards in states where that value 

would exceed the total number of tanks. Also adjusted for more precise state data available in state and Tribal land UST 

databases.

3. Industrial Economics, “Preliminary Assessment and Scoping of Data Related to Potential Revisions to the UST Regulations; 

Tasks 2-4, Work Assignment 1-25,” November 20, 2008, Appendix A.

4. Industrial Economics, “Preliminary Assessment and Scoping of Data Related to Potential Revisions to the UST Regulations; 

Tasks 2-4, Work Assignment 1-25,” November 20, 2008, Appendix A.

5. Equal to 3 percent of total tanks, based on weighted average in databases from Florida, Massachusetts, Missouri, and 

Wisconsin, except in states where not enough tanks remain to account for other documented uses.

6. Equal to E

2

estimate of 4 percent of total tanks, except in states where not enough tanks remain to account for this 

category, and Alaska, where the state database identified 59 tanks containing used oil. Estimate based on review of 2006 

state data; according to E2, Category includes tanks containing used oil, hazardous chemicals, and substances labeled as 

“unknown” or “other” in state databases.

7. Equal to all unaccounted-for tanks after calculating other values.

8. EPA, “FY2008 End-of-Year Activity Report.”

The key difference between the refined PCCI and refined E2 methodologies is the 

estimated number of tanks per retail motor fuel location. The estimated number of retail 

motor fuel tanks under the PCCI methodology assumes that the average number of tanks 

per retail location is 2.65, based on the total national average number of tanks per facility 

reported in EPA’s June 2000 “Report to Congress on a Compliance Plan for the 

Underground Storage Tank Program.” The modified E2 methodology extrapolates state 

data collected by E2to that indicate that retail motor fuel locations typically have 3.13

tanks per facility. This method results in approximately 43,500 additional tanks (roughly 

 

type of tank from Subpart B state notification requirements. It is therefore possible that these 60 tanks may not be included 

in the 623,319 active tanks reported to EPA. However, due to the small number of tanks and the uncertainty about state 

reporting requirements, we do not adjust the EPA reported totals to include any potentially unaccounted-for fieldconstructed tanks.

6

See Industrial Economics, “Preliminary Assessment and Scoping of Data Related to Potential Revisions to the UST 

Regulations; Tasks 2-4, Work Assignment 1-25,” November 20, 2008, Appendix A, p.9.
4

seven percent of total tanks) identified as retail motor fuel tanks under the modified E2

methodology; most of these are assumed to be non-retail fuel tanks under the modified 

PCCI methodology. For a breakdown of the distribution of tanks by state under each 

methodology, see Appendix A.

7

As the results show, a number of differences exist between the figures, and certain 

estimates reflect considerable uncertainty. We discuss these issues below, including: (1) 

the number of tanks at motor fuel retailers; (2) the number of non-retail fuel tanks; (3) the 

number of emergency generator tanks; and (4) other non-fuel tanks.

Tanks at Motor Fuel Retailers

The number of tanks at motor fuel retailers is an estimate with considerable uncertainty. 

According to EPA’s June 2000 “Report to Congress on a Compliance Plan for the 

Underground Storage Tank Program,” facilities with tanks have an average of 2.65 tanks 

per facility.

8 However, a more recent investigation of a subset of state databases by E2

shows an average of 2.87 tanks per facility, with retail motor fuel locations specifically 

having 3.13 tanks per facility.

9

Finally, a comparison of the state data in EPA’s “FY2007 

End-of-Year Activity Report” and data on the number of motor fuel retailers in each state 

from the Energy Information Administration (EIA) shows that in many states there must 

be less than 2.65 tanks per location, as the total number of active USTs in all sectors is 

less than 2.65 times the number of retail motor fuel locations.

10

Note that a prior IEc and PCCI estimate using the EPA average of 2.65 tanks per facility 

(except in states where the number of tanks per facility must be lower, as discussed 

above) and 2007 retail motor fuel location data identified 427,500 tanks at retail motor 

fuel locations.

11 Exhibit 1 refines this estimate with more precise data from states that 

publish their UST databases and with 2008 tank population and retail fuel location data.

Applying the same adjustments to the E

2

state data-derived estimate of 3.13 tanks per 

retail motor fuel location, we estimate that the number of tanks at motor fuel retailers 

range approximately between 437,000 and 481,000.

Tanks with Non-Retail Motor Fuel and Other Petroleum Products

Non-retail motor fuel tanks typically include tanks used for multiple vehicles and “fleets,”

as well as other types of fuels (aviation fuel, home heating oil) and non-fuel petroleum 

projects such as motor oil and lubricating oil.

 

7 Note that under the modified E2 methodology, two states (Alabama and Nevada) have no tanks in either the non-retail or 

non-fuel categories. Two additional states (South Carolina and Washington), have no tanks in the non-retail fuel category. 

Under the modified PCCI methodology, two states (Iowa and North Dakota) have no tanks in either the non-retail fuel or nonfuel categories.

8

EPA, “Report to Congress on a Compliance Plan for the Underground Storage Tank Program,” June 2000, as viewed at 

http://www.epa.gov/OUST/pubs/rtc_0600.pdf on December 18, 2008, p.38.

9

E

2

, Incorporated, “Delivery Prohibition - Draft Preliminary Analyses,” December 18, 2006.

10 Industrial Economics, “Preliminary Assessment and Scoping of Data Related to Potential Revisions to the UST Regulations; 

Tasks 2-4, Work Assignment 1-25,” November 10, 2008, Appendix A. Note that this memorandum updates the Appendix A

estimates to reflect the number of service stations from NPN Market Facts 2008 and the number of tanks from EPA’s 2008 

End-of-Year Activity Report.

11 The number of service stations is derived from EIA data and other sources for non-state territories. This value is multiplied 

by 2.65 and compared to the total number of tanks reported in EPA’s “FY2008 End-of-Year Activity Report.” If the result 

exceeds the total number of tanks reported to EPA, we adjust the number of tanks per facility rate down to either 2.0 or 1.0 

until this is corrected. See Industrial Economics, “Preliminary Assessment and Scoping of Data Related to Potential Revisions 

to the UST Regulations; Tasks 2-4, Work Assignment 1-25,” November 20, 2008, Appendix A.
5

Information on the distribution of some non-retail motor fuel tanks comes from the Steel 

Tank Institute. In 2000, the Steel Tank Institute estimated that tanks serving vehicle

fleets accounted for just four percent of new UST installations.12 However, they further 

estimate that “institutions” (e.g., universities and hospitals) account for six percent of 

installations, and government account for another six percent. These sectors likely 

include a mix of refueling stations for vehicles and emergency generator tanks. In 

general, the Steel Tank Institute observes that, due to EPA regulations and clean-up costs 

associated with UST leaks, non-retail service station facilities that need tanks favor 

aboveground storage tanks.13 Because we do not have reliable estimates of non-retail 

tanks for fueling fleets and other vehicles, and because we believe these tanks account for 

a large portion of tanks not otherwise specified in this analysis, we assign all remaining 

tanks reported in EPA’s FY2008 End-of-Year Activity Report after calculating the other 

categories to non-retail fuel tanks. 

In addition to tanks used for non-retail vehicle fueling, a limited number of the tanks in 

this category support uses other than motor-vehicle fueling. These include tanks with 

non-transportation fuels such as propane and home heating oil stored for resale, other 

transportation fuels such as jet fuel (distributed through fueling trucks and no hydrant 

systems), and petroleum products such as lubricating oils and crude oil. A review of 

2006 state data collected by E2indicates that these non-motor-vehicle uses represent 

roughly three percent of all tanks. 

Emergency Generator Tanks

We identified a range of estimates of the number of emergency generator tanks from 

several states and in conversations with installers. Anecdotal evidence from the Hill 

Company, a large installer of USTs in Texas, suggests that up to 80 percent of tanks that 

are not at retail motor fuel locations may be part of emergency generators.14 However, an 

examination of several state databases suggests that a much smaller portion of the UST 

universe is emergency generator tanks. In Massachusetts, only two percent (243 of 

11,876) of active USTs in the state database are designated as emergency generator tanks, 

although over 18 percent do not have a usage designated.15 Wisconsin identifies a similar 

percentage of tanks as generators (234 of 12,354, or 1.9 percent), and while the state does 

not have any unidentified tanks, another 6.5 percent of tanks belong to the broad 

categories “Industrial” and “Mercantile/Commercial” and could be used to support 

emergency generation.16 Missouri identifies approximately 2.5 percent (215 of 8,419) of 

active tanks as emergency generators.17 Finally, while Florida’s database does not 

explicitly identify tanks as emergency generator tanks, according to the tank contents 

 

12 Geyer, Wayne, “UST History,” 2000, as viewed at 

https://www.steeltank.com/LinkClick.aspx?fileticket=GLBrj44tMj0%3D&tabid=108&mid=502 on November 23, 2008, p. 12.

Note the Steel Tank Institute does not define or otherwise specify what types of businesses are included in the category 

“fleet” in their statistics.

13 Geyer, Wayne, “UST History,” 2000, as viewed at 

https://www.steeltank.com/LinkClick.aspx?fileticket=GLBrj44tMj0%3D&tabid=108&mid=502 on November 23, 2008, p. 10.

14 Personal communication with Tommy Dillard, Estimator/Project Coordinator, the Hill Company, on November 24, 2008. It 

is not clear whether Mr. Dillard considers fleet refueling and government operations as part of his estimate of retail 

establishments. This may account for at least part of the discrepancy between his estimate and the state data.

15 Massachusetts’ UST database is available at http://www.mass.gov/Eeops/docs/dfs/osfm/ust/ust.exe

16 Wisconsin’s UST database is available at http://apps.commerce.state.wi.us/ers/ER-EN-TankArchive.zip

17 Missouri’s UST database is available at http://www.dnr.mo.gov/env/hwp/tanks/internet.zip
6

field, 3.8 percent (1,130 of 29,028) of tanks have the value “Emergency Generator 

Diesel” listed as the fuel.

18

Based on the weighted average percentage of emergency generator tanks identified in the 

four states reporting this distinction, we estimate that up to three percent of the total tanks 

in a state are emergency generator tanks (Exhibit 1). While four states are not enough to 

provide statistical significance in our national estimates, these states represent several 

regions of the United States, have differences in regulation for emergency generators, and 

present a tight range of estimates of emergency generator tanks, suggesting that it may be

reasonable to assume that these numbers are representative of national patterns.

Other Tanks: Field -Constructed Tanks, Nuclear Power Plant Tanks, and Non -Fuel 

Tanks

Exhibit 1 presents estimates of field-constructed tanks and emergency generator tanks at 

nuclear power plants identified in our previous research.19 While these estimates do not 

reflect a comprehensive effort to identify all tanks, the specific estimates are derived from 

Department of Defense data sources and other published estimates, and tank installation 

experts contacted asserted that these tank types are not used by other sectors. In addition, 

the tanks in this population are a small fraction of the total tank universe, suggesting that 

uncertainty associated with this estimate is not likely to affect regulatory costs.

Finally, up to four percent of tanks are designated as tanks for storage of non-fuel 

products.

20 Based on E2

’s analysis of state databases, approximately 1.8 percent of these 

tanks hold used oil, 0.3 percent hold hazardous chemicals, and the remaining tanks have 

contents labeled as “other” or “unknown” in the state databases.

TANK CONTENTS

To further refine and verify the precision of our estimates above, we investigated the 

types of fuels or other chemicals identified in 13 state databases that provide detail about 

tank contents. 

Our ability to identify tank purpose by tank content is limited by the multiple uses of

diesel fuel, which is associated with retail motor fuel establishments, non-retail motor 

fuel uses (e.g., agriculture, construction, and government) and emergency generators. 

However, a review of the state data provides some insights into estimates in Exhibit 1, in 

that:

Roughly 75 percent of all tanks in the 13 state databases contain gasoline or 

ethanol; this is generally consistent with the range of retail motor fuel tanks (70.1 

percent and 77.1 percent) described in Exhibit 1. While some of these tanks are 

likely associated with non-retail establishments, this number does not include the 

diesel fuel and other tanks associated with retail motor fuel sales. 

Tanks storing fuels appropriate for emergency generation (i.e., diesel not specified 

as vehicle fuel, propane, and kerosene) represent 18.5 percent of all tanks in the 13 

state databases. A large number of these tanks, however, are likely diesel tanks 

storing fuel for vehicle use at both retail and non-retail facilities. Similarly, some 

 

18 Florida’s UST database delivered by email from E2

via EPA on December 16, 2008.

19 Industrial Economics, “Preliminary Assessment and Scoping of Data Related to Potential Revisions to the UST Regulations; 

Tasks 2-4, Work Assignment 1-25,” November 20, 2008, Appendix A.

20 E2

, Incorporated, “Delivery Prohibition - Draft Preliminary Analyses,” December 18, 2006.
7

of the kerosene and propane storage tanks could support other applications such as 

heating fuel.

Tanks storing petroleum products and fuels other than gasoline and diesel (e.g., 

crude oil, aviation fuel, and motor oil) represent roughly three percent of all tanks 

in the 13 states. 

Other tanks (including those storing chemicals, used oil, and unidentified 

substances) represent 3.2 percent of the tanks in the 13 states. This number is 

roughly consistent with the four percent estimate provided by E2and used in 

Exhibit 1. We rely on the E2estimate in Exhibit 1 because it was based on a more 

thorough examination of state data and definitions than we used in this screeninglevel review.

Overall, however, our review of tank by content suggests that the basic distribution of 

tanks across purpose is not likely to change significantly based on additional tank content 

data, though more information about the uses of diesel fuel (e.g., the number of retail 

motor fuel establishments selling diesel) could help refine the estimate of the number of 

tanks used for emergency generation. In addition, a detailed review of state data 

matching content to specific facility name could potentially help refine estimates of retail, 

non-retail, and emergency uses of gasoline, diesel, and other fuels.

In addition to our general review of state data, we used data from Alaska to refine 

estimates in Exhibit 1. Alaska’s tank content data showed a higher number of tanks 

storing used oil than the four percent estimate from E2. After excluding the 564 tanks 

positively-identified as gas station tanks in Alaska, we distribute the remaining tanks by 

content, shown in Exhibit 2. Exhibit 2 also presents, for comparison purposes, the values 

for tank purpose estimated above.

EXHIBIT 2 NON-SERVICE STATION TANKS BY CONTENTS IN ALASKA

TANK CONTENTS TANKS COMMENTS

Diesel 319 Subset of the 524 emergency generator tanks and nonretail fuel tanks.

Gasoline 188 Subset of the 489 non-retail fuel tanks.

Kerosene 8

Used for jet fuel; included in non-retail fuel and other 

petroleum product tank category.

Other 7 Unknown.

Used Oil 59 Exceeds four percent of total tanks; Exhibits 1 and 2 

adjusted accordingly.

Source: Alaska state UST database provided by E2via EPA.

Gasoline accounts for 188 tanks, well below the 489 tanks identified earlier. Diesel tanks 

could be distributed as either non-retail fuel tanks or emergency generator tanks such that 

this does not conflict with our earlier estimates. The used oil tanks, however, exceed four 

percent of tanks in Alaska. We therefore adjusted our Exhibit 1 estimates to account for 

this higher number. This is the only case where the tank contents reported in the 13 state 

databases directly altered our initial estimates.
8

USTS ON TRIBAL LANDS

In general, OUST delegates UST activities to state-level environmental agencies. 

However, EPA is the agency responsible for implementing regulations on Tribal lands. 

Therefore, EPA is interested in specifically characterizing USTs located on Tribal lands. 

In addition, Tribal governments are typically small entities, so Tribal government-owned 

businesses must be considered under RFA/SBREFA. This section provides an estimate of 

the number of tanks on Tribal lands and a discussion of the industries and sectors to 

which these tanks belong.

In 2007, OUST produced a report to Congress entitled, “Report to Congress on 

Implementing and Enforcing the Underground Storage Tank Program in Indian Country.”

In the report, they established that 2,658 active tanks existed on Tribal lands at that 

time.21 This estimate differs only slightly from the 2,656 tanks estimated in the “FY2008

End-of-Year Activity Report”. Exhibit 3 lists the number of tanks in each industry sector 

as reported in an EPA database documenting tanks in seven of the ten EPA regions, and 

2,112 total tanks on Tribal lands.

EXHIBIT 3 DISTRIBUTION OF TANKS BY SECTOR ON TRIBAL LANDS

SECTOR NUMBER OF TANKS

Airlines & Aircraft Owners 7

Auto Dealership 6

Commercial 47

Contractor 2

Farm 18

Federal Military 18

Federal Non-Military 54

Retail Motor Fuel Sales (gas 

station) 1,653

Industrial 15

State/Local Government 120

Other/Unknown 129

Petroleum Distributor 9

Private 9

Residential 2

School 14

Truck/Transporter 6

Utilities 3

Total 2,112

Source: Database of USTs on Tribal lands provided by EPA.

The distribution of tanks by sector in Exhibit 3 is similar to the types of industries that use 

USTs in the rest of the United States, although there appear to more government-owned 

tanks than elsewhere. In addition, only 35 tanks are identified as emergency generator 

tanks, and only 724 tanks are identified as tribal-owned. 

 

21 EPA Office of Underground Storage Tanks, “Report to Congress on Implementing and Enforcing the Underground Storage 

Tank Program in Indian Country,” August 2007, p.28.
9

Of the 35 emergency generator tanks, only 9 are identified as owned by entities other than 

the Federal government. Conversations with two EPA regional inspectors representing 

Regions 8 and 9 (Lisa Luebke and Mary Keil, respectively) suggest that the estimates of 

emergency generator tanks may be low.

Region 9 includes the Navajo Nation, the largest tribe in the United States, which 

accordingly accounts for the largest number and variety of tanks. Ms. Keil identified 

several tank uses supporting the Tribe, including bus depots at schools, emergency 

generators at hospitals, and Tribal government fleet refueling sites. In addition, she noted 

that casinos and mining companies likely have a stronger representation on Tribal lands

than elsewhere. In addition, in her experience, all casinos have emergency generator

facilities, and many also operate their own retail gas stations. While the database 

identified numerous casino-operated gas stations, it contains only three casino-owned 

emergency generator tanks. Unless the remaining casinos use aboveground storage tanks, 

she believes that the emergency generator estimate for Region 9 may be low. Ms. Luebke 

had less detailed information on potential discrepancies in Tribal data, but confirmed that 

retail motor fuel establishments represent the majority of UST locations.

Other than the existence of casinos and natural resource extraction industries, we have not 

identified substantial differences between the types of businesses owning USTs on Tribal 

lands and businesses in the rest of the United States. However, it is noteworthy that a 

approximately one-third of tanks on Tribal lands appear to be owned by Tribal 

governments, most of which are small entities.

The number and uses of tanks described in this memo are based on various sources. 

While the total number of active, regulated USTs is relatively precise, we have 

encountered several conflicting estimates of how those USTs are distributed among 

industries and uses. Therefore, we present two estimates of these distributions, with 

roughly seven percent of the tanks redistributed between the estimates. However, the 

actual number of tanks of a particular type could be higher or lower than the figures 

presented in this memo. The greatest source of uncertainty is the distribution of uses for 

tanks with diesel fuel across emergency generation, retail motor fuel, and non-retail fuel 

uses.

The data presented in this memo on tanks on Tribal lands have several areas of 

uncertainty as well. Most significantly, three of the EPA regions representing 14 states

and two territories are not included in this analysis.

NEXT STEPS 

This analysis provides a general estimate of the number and type of USTs currently in 

use, and the general distribution of UST use by purpose and design. While the priorities 

for refining this analysis will be determined in part by the specific regulatory options 

under consideration, the following may provide useful insights:

Additional data on Tribal ownership patterns: The data collected to date do not 

address all tanks on Tribal lands and rely on limited contacts with EPA regional 

staff. If Tribal ownership or sector distribution of tanks on tribal lands is central to 

EPA’s rulemaking effort, collection of additional data on tank ownership and use 

from remaining regions and Tribes, as well as supplemental data from the regions 

already contacted, could be useful.

KEY SOURCES OF 

UNCERTAINTY AND NEXT

STEPS
10

Detailed analysis of specific sectors or tank applications: This analysis 

provides general information on the uses of USTs, but uses extrapolation from a 

limited set of data to identify emergency generator tanks. If a detailed assessment 

of tanks used for emergency generation is central to the evaluation of regulatory 

options, a more detailed investigation of additional states that track emergency 

generator tanks, coupled with an investigation of the distribution of different uses 

for diesel fuel, would be useful.

Refinement of estimate of retail gasoline establishments and tank use: This 

analysis identifies discrepancies in the number of tanks and establishments 

associated with the retail sale of motor fuel. If EPA determines that the uncertainty 

associated with retail motor fuel tank usage would have a significant impact on 

estimates of total regulatory cost, then refining this set of estimates, or undertaking 

a more detailed analysis of the distribution of ownership in this sector may be 

useful to support either a regulatory cost or small business analysis or both.
11

APPENDIX A

EXHIBIT A-1 DISTRIBUTION OF TANKS BY STATE AND USE (MODIFIED PCCI METHODOLOGY)

STATE OR 

TERRITORY

SERVICE 

STATION 

TANKS1

FCT2 NUCLEAR 

EGT3

OTHER 

EGT4

NON-RETAIL 

FLEET 

REFUELING 

TANKS5

OTHER 

(NON-FUEL) 

TANKS6

TOTAL 

ACTIVE 

USTS7

Alabama 16,298 0 5 562 1,115 749 18,728

Alaska 564 4 0 36 535 59 1,198

American Samoa 11 0 0 0 4 1 16

Arizona 5,435 0 3 212 1,129 282 7,061

Arkansas 6,731 0 2 280 1,960 374 9,347

California 27,030 87 4 1,121 7,641 1,495 37,379

Colorado 6,153 0 0 238 1,225 317 7,934

Connecticut 4,055 0 2 292 4,999 389 9,737

Delaware 1,131 0 0 44 218 58 1,450

District of Columbia 313 0 0 21 329 28 690

Florida 24,552 7 5 841 1,515 1,122 28,042

Georgia 23,120 0 4 898 4,709 1,197 29,928

Guam 111 33 0 8 97 10 259

Hawaii 959 24 0 50 571 67 1,671

Idaho 2,536 0 0 105 715 140 3,496

Illinois 11,649 0 11 666 8,978 888 22,192

Indiana 8,104 0 0 411 4,623 547 13,685

Iowa 7,155 0 1 19 0 0 7,175

Kansas 5,600 0 1 210 899 280 6,989

Kentucky 8,790 0 0 365 2,511 486 12,152

Louisiana 9,524 0 2 369 1,907 492 12,294

Maine 2,854 0 0 93 31 124 3,102

Maryland 5,883 0 2 257 2,094 343 8,580

Massachusetts 7,925 0 1 321 2,035 428 10,711

Michigan 12,959 0 4 594 5,449 792 19,797

Minnesota 9,990 0 3 438 3,592 584 14,608

Mississippi 6,738 0 1 262 1,369 349 8,718

Missouri 8,188 0 1 303 1,212 404 10,109

Montana 2,120 0 0 98 912 130 3,260

Nebraska 4,084 0 2 207 2,318 275 6,886

Nevada 3,658 0 0 112 0 0 3,770

New Hampshire 2,422 0 1 93 462 124 3,102

New Jersey 8,326 0 4 484 6,678 646 16,138

New Mexico 3,087 0 0 120 622 160 3,988

New York 17,225 0 6 883 10,129 1,177 29,419

North Carolina 18,227 0 5 851 8,157 1,135 28,375

North Dakota 2,088 0 0 63 0 0 2,151
12

STATE OR 

TERRITORY

SERVICE 

STATION 

TANKS1

FCT2 NUCLEAR 

EGT3

OTHER 

EGT4

NON-RETAIL 

FLEET 

REFUELING 

TANKS5

OTHER 

(NON-FUEL) 

TANKS6

TOTAL 

ACTIVE 

USTS7

Northern Mariana 

Islands 48 0 0 2 16 3 68

Ohio 13,136 0 2 701 8,607 935 23,382

Oklahoma 10,335 0 0 330 0 338 11,003

Oregon 4,433 0 0 180 1,154 240 6,008

Pennsylvania 12,489 0 9 727 10,040 969 24,235

Puerto Rico 3,146 0 0 136 1,081 182 4,545

Rhode Island 994 0 0 49 512 65 1,619

South Carolina 9,757 5 7 358 1,321 477 11,925

South Dakota 2,761 2 0 92 78 122 3,055

Tennessee 12,104 0 3 509 3,683 679 16,978

Texas 36,191 4 4 1,615 13,870 2,154 53,838

US Virgin Islands 98 0 0 4 36 6 144

Utah 2,981 0 0 120 743 160 4,005

Vermont 1,632 0 1 93 1,238 124 3,088

Virginia 15,189 23 4 599 3,351 799 19,964

Washington 8,178 50 1 302 1,121 402 10,054

West Virginia 3,843 0 0 169 1,383 225 5,619

Wisconsin 10,641 0 3 451 3,347 602 15,044

Wyoming 1,524 0 0 59 292 78 1,952

Tribal Lands 2,079 0 0 80 391 106 2,656

Totals 437,154 239 104 18,500 143,004 24,318 623,319

1. Equal to 2.65 times the 161,768 retail motor fuel locations (service stations) reported by NPN, adjusted downwards in states 

where that value would exceed the total number of tanks. Also adjusted for more precise state data available in state and 

Tribal land UST databases.

2. Industrial Economics, “Preliminary Assessment and Scoping of Data Related to Potential Revisions to the UST Regulations; 

Tasks 2-4, Work Assignment 1-25,” November 20, 2008, Appendix A.

3. Industrial Economics, “Preliminary Assessment and Scoping of Data Related to Potential Revisions to the UST Regulations; 

Tasks 2-4, Work Assignment 1-25,” November 20, 2008, Appendix A.

4. Equal to 3 percent of total tanks, based on weighted average in databases from Florida, Massachusetts, Missouri, and 

Wisconsin, except in states where not enough tanks remain to account for other documented uses.

5. Equal to E

2

estimate of 4 percent of total tanks, except in states where not enough tanks remain to account for this 

category, and Alaska, where the state database identified 59 tanks containing used oil. Estimate based on review of 2006 state 

data; according to E2, Category includes tanks containing used oil, hazardous chemicals, and substances labeled as “unknown” 

or “other” in state databases.

6. Equal to all unaccounted-for tanks after calculating other values.

7. EPA, “FY2008 End-of-Year Activity Report.”
13

EXHIBIT A-2 DISTRIBUTION OF TANKS BY STATE AND USE (MODIFIED E

2 METHODOLOGY)

STATE OR 

TERRITORY

SERVICE 

STATION 

TANKS1

FCT2 NUCLEAR 

EGT3

OTHER 

EGT4

NON-RETAIL 

FLEET 

REFUELING 

TANKS5

OTHER 

(NON-FUEL) 

TANKS6

TOTAL 

ACTIVE 

USTS7

Alabama 18,450 0 5 273 0 0 18,728

Alaska 564 4 0 36 535 59 1,198

American Samoa 13 0 0 0 2 1 16

Arizona 6,420 0 3 212 144 282 7,061

Arkansas 7,950 0 2 280 741 374 9,347

California 31,926 87 4 1,121 2,745 1,495 37,379

Colorado 7,268 0 0 238 111 317 7,934

Connecticut 4,789 0 2 292 4,265 389 9,737

Delaware 1,131 0 0 44 218 58 1,450

District of Columbia 369 0 0 21 272 28 690

Florida 24,552 7 5 841 1,515 1,122 28,042

Georgia 23,120 0 4 898 4,709 1,197 29,928

Guam 131 33 0 8 76 10 259

Hawaii 1,133 24 0 50 397 67 1,671

Idaho 2,995 0 0 105 256 140 3,496

Illinois 13,759 0 11 666 6,868 888 22,192

Indiana 9,572 0 0 411 3,156 547 13,685

Iowa 5,400 0 1 215 1,272 287 7,175

Kansas 5,600 0 1 210 899 280 6,989

Kentucky 10,382 0 0 365 919 486 12,152

Louisiana 11,249 0 2 369 182 492 12,294

Maine 2,854 0 0 93 31 124 3,102

Maryland 5,883 0 2 257 2,094 343 8,580

Massachusetts 7,925 0 1 321 2,035 428 10,711

Michigan 15,306 0 4 594 3,102 792 19,797

Minnesota 9,990 0 3 438 3,592 584 14,608

Mississippi 6,738 0 1 262 1,369 349 8,718

Missouri 8,188 0 1 303 1,212 404 10,109

Montana 2,504 0 0 98 528 130 3,260

Nebraska 4,823 0 2 207 1,579 275 6,886

Nevada 3,658 0 0 112 0 0 3,770

New Hampshire 2,861 0 1 93 23 124 3,102

New Jersey 9,834 0 4 484 5,170 646 16,138

New Mexico 3,646 0 0 120 62 160 3,988

New York 20,345 0 6 883 7,009 1,177 29,419

North Carolina 21,528 0 5 851 4,856 1,135 28,375

North Dakota 1,576 0 0 65 424 86 2,151
14

STATE OR 

TERRITORY

SERVICE 

STATION 

TANKS1

FCT2 NUCLEAR 

EGT3

OTHER 

EGT4

NON-RETAIL 

FLEET 

REFUELING 

TANKS5

OTHER 

(NON-FUEL) 

TANKS6

TOTAL 

ACTIVE 

USTS7

Northern Mariana 

Islands 56 0 0 2 7 3 68

Ohio 15,515 0 2 701 6,228 935 23,382

Oklahoma 7,800 0 0 330 2,433 440 11,003

Oregon 5,236 0 0 180 351 240 6,008

Pennsylvania 14,752 0 9 727 7,778 969 24,235

Puerto Rico 3,715 0 0 136 512 182 4,545

Rhode Island 1,174 0 0 49 332 65 1,619

South Carolina 11,525 5 7 358 0 31 11,925

South Dakota 2,084 2 0 92 755 122 3,055

Tennessee 12,104 0 3 509 3,683 679 16,978

Texas 42,746 4 4 1,615 7,315 2,154 53,838

US Virgin Islands 116 0 0 4 18 6 144

Utah 3,521 0 0 120 203 160 4,005

Vermont 1,928 0 1 93 943 124 3,088

Virginia 15,189 23 4 599 3,351 799 19,964

Washington 9,659 50 1 302 0 42 10,054

West Virginia 4,539 0 0 169 687 225 5,619

Wisconsin 10,641 0 3 451 3,347 602 15,044

Wyoming 1,800 0 0 59 16 78 1,952

Tribal Lands 2,079 0 0 80 391 106 2,656

Totals 480,613 239 104 18,410 100,716 23,238 623,319

1. Equal to 3.13 times the 161,768 retail motor fuel locations (service stations) reported by NPN, adjusted downwards in states 

where that value would exceed the total number of tanks. Also adjusted for more precise state data available in state and 

Tribal land UST databases.

2. Industrial Economics, “Preliminary Assessment and Scoping of Data Related to Potential Revisions to the UST Regulations; 

Tasks 2-4, Work Assignment 1-25,” November 20, 2008, Appendix A.

3. Industrial Economics, “Preliminary Assessment and Scoping of Data Related to Potential Revisions to the UST Regulations; 

Tasks 2-4, Work Assignment 1-25,” November 20, 2008, Appendix A.

4. Equal to 3 percent of total tanks, based on weighted average in databases from Florida, Massachusetts, Missouri, and 

Wisconsin, except in states where not enough tanks remain to account for other documented uses.

5. Equal to E

2

estimate of 4 percent of total tanks, except in states where not enough tanks remain to account for this 

category, and Alaska, where the state database identified 59 tanks containing used oil. Estimate based on review of 2006 state 

data; according to E2, Category includes tanks containing used oil, hazardous chemicals, and substances labeled as “unknown” 

or “other” in state databases.

6. Equal to all unaccounted-for tanks after calculating other values.

7. EPA, “FY2008 End-of-Year Activity Report.”