Early detection of leaks (or loss) from underground petroleum storage systems (UPSS) helps prevent environmental pollution, health risks, costly remediation of land and damage to vehicles.
The Environmental Management and Pollution Control (Underground Petroleum Storage Systems) Regulations 2020 (UPSS Regulations) require loss monitoring of UPSS. Loss monitoring records must be kept by the UPSS system operator for 10 years and provided to the EPA if required.
Small storage systems
Small storage systems are defined as 1 or many tanks with a total (in aggregate and including waste oil tanks) storage capacity of 5,500 L. The system operator must complete manual tank gauging at least twice each year, no sooner than four months apart. Gauging records must be kept by the system operator.
Manual tank gauging involves measuring the level of petroleum in the fuel tank, leaving the storage system for at least 36 hours without petroleum being added or removed, then measuring the petroleum level again. If the difference is greater than 2% of the tank capacity then the system operator must notify the infrastructure owner, prevent further fuel being lost and not use the storage system until it is repaired or replaced. The infrastructure owner must ensure that the Director is notified and an Environmental Site Assessment is conducted in accordance with the UPSS Regulations.
All other storage systems
For all other storage systems the monitoring method must be capable, at a minimum, of detecting a leak of 0.76L/hr (18L per day). This is not an allowable level of loss/gain but it is the industry and government standard set for loss detection.
Commonly, a statistical inventory reconciliation analysis (or SIRA) is the monitoring method used to detect a loss/gain of 0.76L/hr.
The SIRA method used must be evaluated and certified by the
National Work Group on Leak Detection Evaluations.
If SIRA is used, inventory data (fuel delivered, fuel used/sold and dip levels) are sent to an external company to analyse data and report on any fuel loss.
As an alternative to SIRA, automatic tank gauging in conjunction with a leak monitoring system for product piping (in accordance with Section 4.5.3 of Australian Standard AS 4897-2008) can be used.
Companies that undertake SIRA
The SIRA method used must be certified as meeting the US EPA standard.
SIRA providers in Tasmania include:
- Environmental Management Solutions
Phone: 1300 367 783
Fax: 1300 367 785
- Leighton O’Brien Pty Ltd
Phone: +61 3 9804 2200
If a loss is detected
If loss monitoring indicates that petroleum is being lost from a storage system or water is entering a UPSS then:
- within 14 days the system operator must determine whether the loss/gain is due to inaccurate data.
- if the loss/gain is not due to inaccurate data then the system operator must notify the infrastructure owner; and
- the infrastructure owner must ensure that loss investigation occurs in accordance with the UPSS Regulations.
It is essential that daily inventory control is still conducted in order to detect a major system failure. If there is a major failure it needs to be detected as soon as possible rather than waiting potentially more than a month for SIRA to provide a loss result.
Inventory Control is the comparison of: fuel in tank yesterday (from dip readings) + deliveries – sales/use which should equal the amount of fuel in the tank today (from dip readings).
Double walled tanks
Double walled (secondary containment) tanks are tanks with an inner and outer wall with water or a vacuum between the tank walls (in the interstitial space). By monitoring the interstitial space, leaks should be detected before they are released into the environment. The regulations require that, in addition to loss monitoring, the interstitial space between the two walls in a double walled tank must be monitored on at least two occasions, at least four months apart, in each year.
The date, name of the person conducting the monitoring and the results of the monitoring event must be recorded and kept by the system operator.
If interstitial monitoring determines that there is a hole in a wall of a tank then the system operator must notify the infrastructure owner, prevent further fuel being lost and not use the storage system until it is repaired or replaced. The infrastructure owner must ensure that leak investigation occurs in accordance with the UPSS Regulations.
 Australian Standard AS 4897 The design, installation and operation of underground petroleum storage systems, issued and published on 5 February 2008.