WA UST SITE ASSESSOR EXAM
QUESTIONS AND ANSWERS GRADED A+
2025/2026
What is the hold time for soil and preserved GW GRO samples? - ANS 14 days
Is an ICC certification needed to install an AST? - ANS No
Flammability limits of gasoline - ANS 1.4 to 7.6%
How many days do you have from a tank closure to report/provide the UST checklist to ECY? -
ANS 30 days
MTCA Method A lead CUL, soil - ANS 250 mg/kg
MTCA Method A lead CUL, GW - ANS 15 ug/L
Is the vadose zone saturated or unsaturated? - ANS Unsaturated
List in order of most mobile to least mobile: Bunker C, heating oil, diesel, gasoline -
ANS Gasoline, diesel, heating oil, Bunker C
1 @COPYRIGHT 2025/2026 ALLRIGHTS RESERVED.
, Is oxygenated gasoline more or less likely to dissolve in water? - ANS More likely; fuel
additives like MTBE are more soluble than gasoline
Where to sample on dispenser? - ANS 2 feet below where the piping enters the UST
Where to sample along piping? - ANS Every 50 linear feet and along joints/elbows
How many GW samples are needed after decommissioning if a release to GW is confirmed, and
where relative to the tank? - ANS 3; 1 upgradient, 2 downgradient
What vapor is an FID used to measure? - ANS Methane
What is a PID measuring? - ANS Mixture of all volatiles
What conditions might impede a PID? - ANS Moisture/humidity, dust, transformers, power
lines
What UST capacity does not require a site assessment at closure? - ANS Less than 110 gallons
Purpose of a site check - ANS To investigate a UST site for the presence of a release when
evidence indicated that a release may have occurred
Purpose of a site assessment - ANS To investigate a UST site at the time of closure or change-
in-service to determine if a release has occurred
2 @COPYRIGHT 2025/2026 ALLRIGHTS RESERVED.
QUESTIONS AND ANSWERS GRADED A+
2025/2026
What is the hold time for soil and preserved GW GRO samples? - ANS 14 days
Is an ICC certification needed to install an AST? - ANS No
Flammability limits of gasoline - ANS 1.4 to 7.6%
How many days do you have from a tank closure to report/provide the UST checklist to ECY? -
ANS 30 days
MTCA Method A lead CUL, soil - ANS 250 mg/kg
MTCA Method A lead CUL, GW - ANS 15 ug/L
Is the vadose zone saturated or unsaturated? - ANS Unsaturated
List in order of most mobile to least mobile: Bunker C, heating oil, diesel, gasoline -
ANS Gasoline, diesel, heating oil, Bunker C
1 @COPYRIGHT 2025/2026 ALLRIGHTS RESERVED.
, Is oxygenated gasoline more or less likely to dissolve in water? - ANS More likely; fuel
additives like MTBE are more soluble than gasoline
Where to sample on dispenser? - ANS 2 feet below where the piping enters the UST
Where to sample along piping? - ANS Every 50 linear feet and along joints/elbows
How many GW samples are needed after decommissioning if a release to GW is confirmed, and
where relative to the tank? - ANS 3; 1 upgradient, 2 downgradient
What vapor is an FID used to measure? - ANS Methane
What is a PID measuring? - ANS Mixture of all volatiles
What conditions might impede a PID? - ANS Moisture/humidity, dust, transformers, power
lines
What UST capacity does not require a site assessment at closure? - ANS Less than 110 gallons
Purpose of a site check - ANS To investigate a UST site for the presence of a release when
evidence indicated that a release may have occurred
Purpose of a site assessment - ANS To investigate a UST site at the time of closure or change-
in-service to determine if a release has occurred
2 @COPYRIGHT 2025/2026 ALLRIGHTS RESERVED.
