ICC U2 UST Decommissioning Exam Prep
Underground Storage Tank Practice Questions &
Rationales
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
Prior to any tank removal or closure, the UST owner must notify the implementing
agency of intent to close at least:
A) 15 days prior
B) 30 days prior
C) 45 days prior
D) 60 days prior
Correct Answer: B) 30 days prior
Rationale: Federal regulations under 40 CFR §280.71(a) require owners and operators to
notify the implementing agency at least 30 days before beginning permanent closure or
change-in-service .
Question 2
,According to API 1604, which document provides the industry standard for removal and
disposal of used underground petroleum storage tanks?
A) API 2015
B) API 1604
C) API 1631
D) NFPA 326
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 3
When purging a tank of flammable vapors using inert gas, the acceptable lower
explosive limit (LEL) reading before hot work can proceed is:
A) Less than 10%
B) Less than 5%
C) Less than 1%
D) Less than 20%
Correct Answer: C) Less than 1%
Rationale: Before hot work or tank entry, the tank atmosphere must be confirmed to have
an LEL reading of less than 1% to ensure flammable vapors have been adequately purged .
Question 4
The safe oxygen range for tank entry during UST 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 confirmation that oxygen levels are maintained
between 19.5% and 23.5% to safely support life and prevent oxygen-enriched fire hazards
.
Question 5
When removing liquids and residues from a tank, the equipment must be:
A) Standard electric pumps
B) Explosion-proof or air-driven pumps
C) Gasoline-powered pumps
D) Manual hand pumps only
Correct Answer: B) Explosion-proof or air-driven pumps
Rationale: All pumps used for removing liquids and residues must be explosion-proof or
air-driven with proper bonding to the tank or grounding to prevent ignition of flammable
vapors .
Question 6
For a closure-in-place, the tank must be completely filled with:
A) Water only
B) Sand only
C) Approved solid inert material
D) Gravel only
Correct Answer: C) Approved solid inert material
Rationale: Permanent closure in place requires the tank to be filled completely with an
approved solid inert material such as sand-cement slurry meeting minimum 7 MPa
compressive strength at 28 days per API 1604 .
, Question 7
The required notification period to the implementing agency before breaking concrete
during UST closure activities is typically:
A) 30 days
B) 15 days
C) 24 hours verbal notice
D) 48 hours written notice
Correct Answer: C) 24 hours verbal notice
Rationale: Most implementing agencies require 24-hour verbal notice prior to breaking
concrete to allow for inspection scheduling .
Question 8
When venting vapors from a tank during purging operations, the vent must be located
at a minimum height of:
A) 6 feet above grade
B) 12 feet above grade and 3 feet above adjacent roof lines
C) 10 feet above grade
D) 15 feet above grade
Correct Answer: B) 12 feet above grade and 3 feet above adjacent roof lines
Rationale: Vapors must be vented at a minimum height of 12 feet above grade and 3 feet
above any adjacent roof lines until the tank is purged of flammable vapors .
Question 9
The three elements required for the fire triangle are:
Underground Storage Tank Practice Questions &
Rationales
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
Prior to any tank removal or closure, the UST owner must notify the implementing
agency of intent to close at least:
A) 15 days prior
B) 30 days prior
C) 45 days prior
D) 60 days prior
Correct Answer: B) 30 days prior
Rationale: Federal regulations under 40 CFR §280.71(a) require owners and operators to
notify the implementing agency at least 30 days before beginning permanent closure or
change-in-service .
Question 2
,According to API 1604, which document provides the industry standard for removal and
disposal of used underground petroleum storage tanks?
A) API 2015
B) API 1604
C) API 1631
D) NFPA 326
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 3
When purging a tank of flammable vapors using inert gas, the acceptable lower
explosive limit (LEL) reading before hot work can proceed is:
A) Less than 10%
B) Less than 5%
C) Less than 1%
D) Less than 20%
Correct Answer: C) Less than 1%
Rationale: Before hot work or tank entry, the tank atmosphere must be confirmed to have
an LEL reading of less than 1% to ensure flammable vapors have been adequately purged .
Question 4
The safe oxygen range for tank entry during UST 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 confirmation that oxygen levels are maintained
between 19.5% and 23.5% to safely support life and prevent oxygen-enriched fire hazards
.
Question 5
When removing liquids and residues from a tank, the equipment must be:
A) Standard electric pumps
B) Explosion-proof or air-driven pumps
C) Gasoline-powered pumps
D) Manual hand pumps only
Correct Answer: B) Explosion-proof or air-driven pumps
Rationale: All pumps used for removing liquids and residues must be explosion-proof or
air-driven with proper bonding to the tank or grounding to prevent ignition of flammable
vapors .
Question 6
For a closure-in-place, the tank must be completely filled with:
A) Water only
B) Sand only
C) Approved solid inert material
D) Gravel only
Correct Answer: C) Approved solid inert material
Rationale: Permanent closure in place requires the tank to be filled completely with an
approved solid inert material such as sand-cement slurry meeting minimum 7 MPa
compressive strength at 28 days per API 1604 .
, Question 7
The required notification period to the implementing agency before breaking concrete
during UST closure activities is typically:
A) 30 days
B) 15 days
C) 24 hours verbal notice
D) 48 hours written notice
Correct Answer: C) 24 hours verbal notice
Rationale: Most implementing agencies require 24-hour verbal notice prior to breaking
concrete to allow for inspection scheduling .
Question 8
When venting vapors from a tank during purging operations, the vent must be located
at a minimum height of:
A) 6 feet above grade
B) 12 feet above grade and 3 feet above adjacent roof lines
C) 10 feet above grade
D) 15 feet above grade
Correct Answer: B) 12 feet above grade and 3 feet above adjacent roof lines
Rationale: Vapors must be vented at a minimum height of 12 feet above grade and 3 feet
above any adjacent roof lines until the tank is purged of flammable vapors .
Question 9
The three elements required for the fire triangle are:
