ICC U2 UST Decommissioning Exam Prep
Underground Storage Tank Practice Questions &
Rationales 2026
This specialized technical preparation resource provides targeted practice questions,
verified answers, and detailed regulatory rationales for the International Code Council
(ICC) U2 Underground Storage Tank (UST) Decommissioning certification. It
systematically covers the core safety protocols and engineering guidelines required for
tank removal, including site assessment, permanent closure procedures, vapor freeing,
and soil safety testing. Environmental technicians and safety engineers will master
critical OSHA, EPA, and API standards to ensure a passing score on this highly
technical environmental licensing track.
Question 1
The primary reference standard for closure of underground petroleum storage tanks is:
A) API 2015
B) API 1604
C) API 1631
D) API 570
Correct Answer: B) API 1604
Rationale: API Recommended Practice 1604, "Closure of Underground Petroleum Storage
Tanks," is the primary industry standard governing removal and disposal procedures.
Question 2
A UST system that has been temporarily closed for more than 12 months must be:
,A) Returned to service immediately
B) Permanently closed
C) Inspected monthly
D) Filled with water
Correct Answer: B) Permanently closed
Rationale: Tank systems temporarily closed for more than 12 months must be
permanently closed in accordance with regulatory requirements.
Question 3
During tank removal, soil samples are typically collected from:
A) The surface only
B) The excavation bottom and sidewalls
C) The tank interior
D) Nearby surface water
Correct Answer: B) The excavation bottom and sidewalls
Rationale: Soil samples are collected from the excavation bottom and sidewalls to assess
whether contamination has occurred from the UST system.
Question 4
The first step in the tank removal process is:
A) Purge the tank of vapors
B) Obtain all necessary permits
C) Excavate the tank
D) Remove the tank from the ground
Correct Answer: B) Obtain all necessary permits
,Rationale: Before any work begins, all applicable permits must be obtained from the
regulatory agency.
Question 5
When a tank is purged, the atmosphere inside must be reduced to what percentage of
the lower explosive limit (LEL) before entry?
A) 10%
B) 5%
C) 1%
D) 0.5%
Correct Answer: C) 1%
Rationale: The tank atmosphere must be reduced to less than 1% of the LEL before hot
work or entry is permitted.
Question 6
The safe oxygen range for tank entry during decommissioning is:
A) 15.0% to 19.5%
B) 19.5% to 23.5%
C) 20.0% to 25.0%
D) 10.0% to 15.0%
Correct Answer: B) 19.5% to 23.5%
Rationale: Gas-freeing operations require oxygen levels between 19.5% and 23.5% to
safely support life and prevent fire hazards.
, Question 7
Which of the following is NOT a component of an underground storage tank system?
A) Tank
B) Connected piping
C) Above-ground storage shed
D) Dispensers
Correct Answer: C) Above-ground storage shed
Rationale: A UST system includes the tank, connected piping, ancillary equipment,
containment system, and dispensers. An above-ground storage shed is not part of the UST
system.
Question 8
When removing liquids and residues from a tank, pumps must be:
A) Standard electric pumps
B) Explosion-proof or air-driven
C) Gasoline-powered
D) Manual hand pumps only
Correct Answer: B) Explosion-proof or air-driven
Rationale: All pumps must be explosion-proof or air-driven with proper bonding and
grounding to prevent ignition of flammable vapors.
Question 9
A vacuum truck used for liquid removal should be positioned:
A) Downwind of the tank
B) Upwind of the tank
Underground Storage Tank Practice Questions &
Rationales 2026
This specialized technical preparation resource provides targeted practice questions,
verified answers, and detailed regulatory rationales for the International Code Council
(ICC) U2 Underground Storage Tank (UST) Decommissioning certification. It
systematically covers the core safety protocols and engineering guidelines required for
tank removal, including site assessment, permanent closure procedures, vapor freeing,
and soil safety testing. Environmental technicians and safety engineers will master
critical OSHA, EPA, and API standards to ensure a passing score on this highly
technical environmental licensing track.
Question 1
The primary reference standard for closure of underground petroleum storage tanks is:
A) API 2015
B) API 1604
C) API 1631
D) API 570
Correct Answer: B) API 1604
Rationale: API Recommended Practice 1604, "Closure of Underground Petroleum Storage
Tanks," is the primary industry standard governing removal and disposal procedures.
Question 2
A UST system that has been temporarily closed for more than 12 months must be:
,A) Returned to service immediately
B) Permanently closed
C) Inspected monthly
D) Filled with water
Correct Answer: B) Permanently closed
Rationale: Tank systems temporarily closed for more than 12 months must be
permanently closed in accordance with regulatory requirements.
Question 3
During tank removal, soil samples are typically collected from:
A) The surface only
B) The excavation bottom and sidewalls
C) The tank interior
D) Nearby surface water
Correct Answer: B) The excavation bottom and sidewalls
Rationale: Soil samples are collected from the excavation bottom and sidewalls to assess
whether contamination has occurred from the UST system.
Question 4
The first step in the tank removal process is:
A) Purge the tank of vapors
B) Obtain all necessary permits
C) Excavate the tank
D) Remove the tank from the ground
Correct Answer: B) Obtain all necessary permits
,Rationale: Before any work begins, all applicable permits must be obtained from the
regulatory agency.
Question 5
When a tank is purged, the atmosphere inside must be reduced to what percentage of
the lower explosive limit (LEL) before entry?
A) 10%
B) 5%
C) 1%
D) 0.5%
Correct Answer: C) 1%
Rationale: The tank atmosphere must be reduced to less than 1% of the LEL before hot
work or entry is permitted.
Question 6
The safe oxygen range for tank entry during decommissioning is:
A) 15.0% to 19.5%
B) 19.5% to 23.5%
C) 20.0% to 25.0%
D) 10.0% to 15.0%
Correct Answer: B) 19.5% to 23.5%
Rationale: Gas-freeing operations require oxygen levels between 19.5% and 23.5% to
safely support life and prevent fire hazards.
, Question 7
Which of the following is NOT a component of an underground storage tank system?
A) Tank
B) Connected piping
C) Above-ground storage shed
D) Dispensers
Correct Answer: C) Above-ground storage shed
Rationale: A UST system includes the tank, connected piping, ancillary equipment,
containment system, and dispensers. An above-ground storage shed is not part of the UST
system.
Question 8
When removing liquids and residues from a tank, pumps must be:
A) Standard electric pumps
B) Explosion-proof or air-driven
C) Gasoline-powered
D) Manual hand pumps only
Correct Answer: B) Explosion-proof or air-driven
Rationale: All pumps must be explosion-proof or air-driven with proper bonding and
grounding to prevent ignition of flammable vapors.
Question 9
A vacuum truck used for liquid removal should be positioned:
A) Downwind of the tank
B) Upwind of the tank
