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ICC U2 UST
DECOMMISSIONING EXAM
2026/2027 EDITION
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250 Real Exam Questions with Verified Answers & Rationales | Graded A+
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, ICC U2 UST DECOMMISSIONING EXAM | 2026/2027 EDITION
Section 1: Brief Introduction
The International Code Council (ICC) U2 UST Decommissioning Certification Examination
(2026/2027 Edition) evaluates the technical competence, regulatory mastery, and environmental
safety protocols required for the decommissioning, removal, and closure of underground storage
tank systems. This comprehensive 250-question examination covers core domains including EPA
40 CFR Part 280 regulations, NFPA 30 and NFPA 30A standards, API 1604 and API 2015
recommended practices, OSHA excavation and confined space safety rules, tank purging and
inerting, site assessment and soil/groundwater sampling, hazardous waste transport, and
environmental remediation. Each question is fully integrated with verified correct answers and
detailed technical rationales to ensure complete readiness for certification.
Section 2: The Complete Exam
1. Under EPA 40 CFR Part 280, which of the following is the legal definition of an Underground
Storage Tank (UST)?
A. Any one or combination of tanks, including connected underground pipes, that has at
least 10 percent of its total volume beneath the surface of the ground.
B. Any commercial petroleum storage tank with a capacity exceeding 10,000 gallons regardless
of placement depth.
C. Any tank system having 100% of its total volume located completely below the ground
surface.
D. Any aboveground storage tank that has underground delivery piping longer than 50 feet.
Rationale: EPA 40 CFR § 280.12 explicitly defines an underground storage tank (UST) as any one or
combination of tanks (including underground pipes connected thereto) that is used to contain an
accumulation of regulated substances, and the volume of which (including the volume of underground
pipes connected thereto) is 10 percent or more beneath the surface of the ground.
2. Which of the following underground storage tank systems is explicitly exempt from federal EPA
40 CFR Part 280 regulatory requirements?
A. Commercial fleet diesel storage tanks with a capacity of 5,000 gallons.
B. Farm or residential tanks with a capacity of 1,100 gallons or less used for storing
motor fuel for noncommercial purposes.
C. Used oil storage tanks located at automotive dealership service centers.
D. Retail gasoline service station USTs storing unleaded motor fuel.
Rationale: EPA 40 CFR § 280.12 excludes farm or residential tanks of 1,100 gallons or less capacity
used for storing motor fuel for noncommercial purposes, as well as tanks storing heating oil for
consumptive use on the premises where stored.
ICC U2 UST Decommissioning Certification • 250 Real Exam Questions with Rationales
, ICC U2 UST DECOMMISSIONING EXAM | 2026/2027 EDITION
3. According to API Recommended Practice 1604, what is the primary objective of vapor-freeing or
purging an underground storage tank during decommissioning?
A. To eliminate water contamination from the bottom of the tank shell.
B. To ensure the internal oxygen concentration is maintained at 0 percent.
C. To reduce the flammable vapor concentration inside the tank to a safe level below 10
percent of the Lower Explosive Limit (LEL).
D. To remove heavy residual sludge without entering the tank.
Rationale: API RP 1604 Section 4.2 states that the objective of purging or vapor-freeing is to dilute and
displace flammable hydrocarbon vapors with ambient air until the combustible gas level drops to below
10% of the Lower Explosive Limit (LEL), preventing an explosive atmosphere during excavation, cutting,
and handling.
4. According to EPA 40 CFR § 280.71, what is the mandatory minimum advance notification time
required before initiating permanent closure or a change-in-service of a UST system?
A. At least 24 hours prior to starting excavation.
B. At least 30 days before beginning either permanent closure or change-in-service,
unless the implementing agency specifies otherwise.
C. Within 10 business days following completion of the tank removal.
D. At least 90 calendar days prior to the start of site assessment work.
Rationale: Under EPA 40 CFR § 280.71(a), UST owners and operators must notify the implementing
regulatory agency at least 30 days before beginning either permanent closure or a change-in-service
under § 280.71, or within another reasonable time period determined by the regulatory authority.
5. Under NFPA 30 (Flammable and Combustible Liquids Code), what is the classification of Class I
liquids such as standard unleaded motor gasoline?
A. Combustible liquids having a flash point at or above 100°F (37.8°C).
B. Flammable liquids having a closed-cup flash point below 100°F (37.8°C) and a Reid
vapor pressure not exceeding 40 psia.
C. Non-flammable regulated hazardous substances.
D. Class IIIA combustible liquids having flash points between 140°F and 200°F.
Rationale: NFPA 30 defines Class I flammable liquids as any liquid that has a closed-cup flash point
below 100°F (37.8°C) and a Reid vapor pressure not exceeding 40 psia (2068 mmHg). Motor gasoline is
a Class IB flammable liquid with a flash point typically around -45°F (-43°C).
6. Which industry standard provides the primary guidelines for the safe removal, abandonment in
place, and disposal of underground petroleum storage tanks?
A. ASHRAE Standard 62.1
ICC U2 UST Decommissioning Certification • 250 Real Exam Questions with Rationales
, ICC U2 UST DECOMMISSIONING EXAM | 2026/2027 EDITION
B. ASME Boiler and Pressure Vessel Code Section VIII
C. API Recommended Practice 1604
D. AWWA Standard C200
Rationale: API RP 1604 ('Closure of Underground Petroleum Storage Tanks') is the universally
recognized consensus standard providing comprehensive procedures for decommissioning, vapor-
freeing, removal, in-place abandonment, and disposal of USTs.
7. When a UST system is placed into temporary closure for a period exceeding 12 months, what
does EPA 40 CFR § 280.70 require unless an extension is granted?
A. The owner must permanently close the UST system in accordance with § 280.71
through § 280.74 if it does not meet new UST performance standards or upgrading
requirements.
B. The owner must conduct daily manual tank gauging indefinitely.
C. The owner must fill the tank completely with water and cap the fill pipe.
D. The tank may remain in temporary closure indefinitely without site assessment.
Rationale: EPA 40 CFR § 280.70(c) specifies that when a UST system is temporarily closed for more
than 12 months, owners and operators must permanently close the UST system if it does not meet either
the performance standards in § 280.20 for new UST systems or the upgrading requirements in § 280.21,
unless the regulatory agency grants an extension after a site assessment.
8. Which document outlines the standard practice for installation and decommissioning of
underground storage systems published by the Petroleum Equipment Institute?
A. PEI RP1400
B. PEI RP1200
C. PEI RP100
D. PEI RP900
Rationale: PEI RP100 ('Recommended Practices for Installation of Underground Liquid Storage
Systems') is the primary publication covering UST installation, and along with PEI RP1700 covers
closure and decommissioning procedures in the fueling industry.
9. Under EPA 40 CFR § 280.72, what is the mandatory requirement for assessing the excavation
zone during permanent UST closure?
A. A visual inspection of the grass surrounding the tank pad is sufficient.
B. Soil sampling is required only if free petroleum product is visibly pooling in the pit.
C. No site assessment is required if the tank was empty for over 5 years.
D. Owners and operators must measure for the presence of a release where
contamination is most likely to be present at the UST site (site assessment).
ICC U2 UST Decommissioning Certification • 250 Real Exam Questions with Rationales
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ICC U2 UST
DECOMMISSIONING EXAM
2026/2027 EDITION
━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━
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250 Real Exam Questions with Verified Answers & Rationales | Graded A+
••••••••••••••••
❖◆◈⬥◆❖
, ICC U2 UST DECOMMISSIONING EXAM | 2026/2027 EDITION
Section 1: Brief Introduction
The International Code Council (ICC) U2 UST Decommissioning Certification Examination
(2026/2027 Edition) evaluates the technical competence, regulatory mastery, and environmental
safety protocols required for the decommissioning, removal, and closure of underground storage
tank systems. This comprehensive 250-question examination covers core domains including EPA
40 CFR Part 280 regulations, NFPA 30 and NFPA 30A standards, API 1604 and API 2015
recommended practices, OSHA excavation and confined space safety rules, tank purging and
inerting, site assessment and soil/groundwater sampling, hazardous waste transport, and
environmental remediation. Each question is fully integrated with verified correct answers and
detailed technical rationales to ensure complete readiness for certification.
Section 2: The Complete Exam
1. Under EPA 40 CFR Part 280, which of the following is the legal definition of an Underground
Storage Tank (UST)?
A. Any one or combination of tanks, including connected underground pipes, that has at
least 10 percent of its total volume beneath the surface of the ground.
B. Any commercial petroleum storage tank with a capacity exceeding 10,000 gallons regardless
of placement depth.
C. Any tank system having 100% of its total volume located completely below the ground
surface.
D. Any aboveground storage tank that has underground delivery piping longer than 50 feet.
Rationale: EPA 40 CFR § 280.12 explicitly defines an underground storage tank (UST) as any one or
combination of tanks (including underground pipes connected thereto) that is used to contain an
accumulation of regulated substances, and the volume of which (including the volume of underground
pipes connected thereto) is 10 percent or more beneath the surface of the ground.
2. Which of the following underground storage tank systems is explicitly exempt from federal EPA
40 CFR Part 280 regulatory requirements?
A. Commercial fleet diesel storage tanks with a capacity of 5,000 gallons.
B. Farm or residential tanks with a capacity of 1,100 gallons or less used for storing
motor fuel for noncommercial purposes.
C. Used oil storage tanks located at automotive dealership service centers.
D. Retail gasoline service station USTs storing unleaded motor fuel.
Rationale: EPA 40 CFR § 280.12 excludes farm or residential tanks of 1,100 gallons or less capacity
used for storing motor fuel for noncommercial purposes, as well as tanks storing heating oil for
consumptive use on the premises where stored.
ICC U2 UST Decommissioning Certification • 250 Real Exam Questions with Rationales
, ICC U2 UST DECOMMISSIONING EXAM | 2026/2027 EDITION
3. According to API Recommended Practice 1604, what is the primary objective of vapor-freeing or
purging an underground storage tank during decommissioning?
A. To eliminate water contamination from the bottom of the tank shell.
B. To ensure the internal oxygen concentration is maintained at 0 percent.
C. To reduce the flammable vapor concentration inside the tank to a safe level below 10
percent of the Lower Explosive Limit (LEL).
D. To remove heavy residual sludge without entering the tank.
Rationale: API RP 1604 Section 4.2 states that the objective of purging or vapor-freeing is to dilute and
displace flammable hydrocarbon vapors with ambient air until the combustible gas level drops to below
10% of the Lower Explosive Limit (LEL), preventing an explosive atmosphere during excavation, cutting,
and handling.
4. According to EPA 40 CFR § 280.71, what is the mandatory minimum advance notification time
required before initiating permanent closure or a change-in-service of a UST system?
A. At least 24 hours prior to starting excavation.
B. At least 30 days before beginning either permanent closure or change-in-service,
unless the implementing agency specifies otherwise.
C. Within 10 business days following completion of the tank removal.
D. At least 90 calendar days prior to the start of site assessment work.
Rationale: Under EPA 40 CFR § 280.71(a), UST owners and operators must notify the implementing
regulatory agency at least 30 days before beginning either permanent closure or a change-in-service
under § 280.71, or within another reasonable time period determined by the regulatory authority.
5. Under NFPA 30 (Flammable and Combustible Liquids Code), what is the classification of Class I
liquids such as standard unleaded motor gasoline?
A. Combustible liquids having a flash point at or above 100°F (37.8°C).
B. Flammable liquids having a closed-cup flash point below 100°F (37.8°C) and a Reid
vapor pressure not exceeding 40 psia.
C. Non-flammable regulated hazardous substances.
D. Class IIIA combustible liquids having flash points between 140°F and 200°F.
Rationale: NFPA 30 defines Class I flammable liquids as any liquid that has a closed-cup flash point
below 100°F (37.8°C) and a Reid vapor pressure not exceeding 40 psia (2068 mmHg). Motor gasoline is
a Class IB flammable liquid with a flash point typically around -45°F (-43°C).
6. Which industry standard provides the primary guidelines for the safe removal, abandonment in
place, and disposal of underground petroleum storage tanks?
A. ASHRAE Standard 62.1
ICC U2 UST Decommissioning Certification • 250 Real Exam Questions with Rationales
, ICC U2 UST DECOMMISSIONING EXAM | 2026/2027 EDITION
B. ASME Boiler and Pressure Vessel Code Section VIII
C. API Recommended Practice 1604
D. AWWA Standard C200
Rationale: API RP 1604 ('Closure of Underground Petroleum Storage Tanks') is the universally
recognized consensus standard providing comprehensive procedures for decommissioning, vapor-
freeing, removal, in-place abandonment, and disposal of USTs.
7. When a UST system is placed into temporary closure for a period exceeding 12 months, what
does EPA 40 CFR § 280.70 require unless an extension is granted?
A. The owner must permanently close the UST system in accordance with § 280.71
through § 280.74 if it does not meet new UST performance standards or upgrading
requirements.
B. The owner must conduct daily manual tank gauging indefinitely.
C. The owner must fill the tank completely with water and cap the fill pipe.
D. The tank may remain in temporary closure indefinitely without site assessment.
Rationale: EPA 40 CFR § 280.70(c) specifies that when a UST system is temporarily closed for more
than 12 months, owners and operators must permanently close the UST system if it does not meet either
the performance standards in § 280.20 for new UST systems or the upgrading requirements in § 280.21,
unless the regulatory agency grants an extension after a site assessment.
8. Which document outlines the standard practice for installation and decommissioning of
underground storage systems published by the Petroleum Equipment Institute?
A. PEI RP1400
B. PEI RP1200
C. PEI RP100
D. PEI RP900
Rationale: PEI RP100 ('Recommended Practices for Installation of Underground Liquid Storage
Systems') is the primary publication covering UST installation, and along with PEI RP1700 covers
closure and decommissioning procedures in the fueling industry.
9. Under EPA 40 CFR § 280.72, what is the mandatory requirement for assessing the excavation
zone during permanent UST closure?
A. A visual inspection of the grass surrounding the tank pad is sufficient.
B. Soil sampling is required only if free petroleum product is visibly pooling in the pit.
C. No site assessment is required if the tank was empty for over 5 years.
D. Owners and operators must measure for the presence of a release where
contamination is most likely to be present at the UST site (site assessment).
ICC U2 UST Decommissioning Certification • 250 Real Exam Questions with Rationales
