UST Release Detection & Prevention 3 — Questions and Answers
Question 1: Which of the following best describes 'interstitial monitoring' as a release detection method?
- Testing the space between a double-walled tank or piping for the presence of product or water (Correct answer)
- Monitoring groundwater wells located 20 feet from the tank
- Using ATG probes inside the product to measure ullage changes
- Installing vapor sensors along the property boundary
Correct answer: Testing the space between a double-walled tank or piping for the presence of product or water
Interstitial monitoring checks the interstitial space between the primary and secondary walls of double-walled tanks or piping for evidence of a release.
Question 2: A suction piping system that uses a check valve at the tank is considered 'safe suction' if the piping:
- Slopes back toward the tank and operates at negative pressure (Correct answer)
- Slopes away from the tank and uses positive pressure
- Uses a turbine pump and has automatic shutoff
- Is inspected monthly for corrosion
Correct answer: Slopes back toward the tank and operates at negative pressure
Safe suction piping slopes back toward the tank, has only one check valve at the pump end, and operates under negative pressure so that any leak drains back into the tank.
Question 3: For underground storage tanks storing petroleum, what is the maximum allowable inventory variance before an investigation is required under most state regulations?
- 0.5% of throughput plus 130 gallons
- 1% of throughput plus 130 gallons (Correct answer)
- 2% of throughput plus 260 gallons
- 5% of throughput
Correct answer: 1% of throughput plus 130 gallons
Most states follow the EPA guideline that a variance exceeding 1% of monthly throughput plus 130 gallons triggers a suspected release investigation.
Question 4: Which document must operators maintain on-site (or readily available) to demonstrate compliance with release detection requirements?
- Original tank manufacturer warranty
- Release detection monitoring records for the past year (Correct answer)
- Site assessment report from initial tank installation
- Property deed showing tank location
Correct answer: Release detection monitoring records for the past year
Operators must keep release detection records, including results of monitoring and testing, for at least one year and make them available for inspection.
Question 5: Under EPA's 2015 UST rule, new and replaced tanks must use which release detection approach?
- Manual tank gauging only if capacity is under 2,000 gallons
- Secondary containment with interstitial monitoring (Correct answer)
- Monthly inventory reconciliation combined with annual tightness testing
- ATG with a minimum 0.1 gallon per hour threshold
Correct answer: Secondary containment with interstitial monitoring
The 2015 EPA rule requires new and replaced USTs to have secondary containment (double walls) with interstitial monitoring as the release detection method.
Question 6: What action must an operator take within 24 hours of confirming a suspected release through release detection monitoring?
- Submit a corrective action plan to the EPA
- Notify the implementing agency (state or local authority) (Correct answer)
- Excavate the tank area to find the source
- Shut down all tanks at the facility
Correct answer: Notify the implementing agency (state or local authority)
Operators must report a suspected release to the appropriate implementing agency within 24 hours (or as required by state regulations) after confirmation.
Question 7: Petroleum UST systems with field-constructed tanks greater than 50,000 gallons have different release detection requirements because:
- They store aviation fuel only and are federally exempt
- Standard ATG probes cannot physically reach the bottom
- They require a site-specific plan approved by the implementing agency (Correct answer)
- EPA has permanently deferred their compliance deadlines
Correct answer: They require a site-specific plan approved by the implementing agency
Field-constructed tanks over 50,000 gallons must follow a site-specific release detection plan approved by the implementing agency due to their unique construction and size.
UST Release Detection & Prevention 3
Which of the following best describes 'interstitial monitoring' as a release detection method?