UST Leak Detection with Statistical Inventory Reconciliation

February 13, 2019
By Brian Schefke

If you’re the owner of an underground storage tank (UST), you’re no doubt aware that federal and state laws require you to have a method of leak detection to ensure that oils or hazardous materials are not released into the surrounding environment. Many UST owners equip their tanks with a system of electronic sensors to detect leaks. Such a system can be very effective, but can also be expensive to install and maintain. Statistical Inventory Reconciliation (SIR) is a lower-cost alternative that only requires equipment that you already have available.

SIR is a software package that uses statistical methods to analyze data from the UST owner to determine the likelihood of a release. The tank owner will need the following equipment:

• Automatic tank gauge, or
• Gauge stick with a tank chart to convert stick readings into volumes
• Calibrated dispensing meters to track outgoing product

The UST owner then gathers the following information over a period of at least thirty days:

• Daily stick readings or tank gauge readings (beginning and end of day)
• Daily sales volume of product
• Number and volume of deliveries during the month
• Dimension of the tank(s)

Using this data, you can then run statistical tests using SIR software. If the UST passes the tests, then the system is determined not to be leaking. If the UST fails the tests, then the UST could be leaking, and the UST owner is required to notify the responsible UST regulatory agency, investigate the issue, and implement corrective actions where necessary.

The SIR results may also be inconclusive, which usually means that the data collected by the UST owner is of insufficient quality to make a determination of pass or fail. In the event of an inconclusive result, the UST owner should inform the responsible UST regulatory agency of the result and ensure that its data collection practices are sound.

If you would like to know more about how Freer Consulting can help you with UST regulatory compliance, contact us at 206-285-9044 or info@freerconsulting.com.