Tank removal is a technical and dangerous process that requires a firm grasp of legislative requirements, environmental considerations, OH&S and project management requirements. Tank removal contractors undertaking the work must be appropriately licensed and insured, and should be trained to the minimum industry standard.
The general processes of tank removal once the OH&S, environmental and safety requirements have been applied include, but are not limited to:
- Removal of liquid waste from within the UST
- Service location of forecourt above the UST to confirm the non presence of service conduits
- Nitrogen purging or air venting the internal atmosphere of UST
- Excavation and stockpiling of overburden and exposure of the top of UST
- Onsite destruction of UST
- Breaking and removal of UST anchors
- Excavation and stockpiling of UST packing sands adjacent to and beneath the UST
- Tank removal from excavation and preparation for offsite disposal
- Offsite disposal of UST
- Validation sampling of UST excavation walls and floor and classification sampling of excavated stockpiled material
- Receipt and interpretation of analytical results
- Reinstatement and compaction of UST excavation
- Provision of a Site Validation Report
It should be noted that it is not always practical to remove a tank, such as when it is located beneath or immediately adjacent to a structure. When a tank cannot physically be removed or when it will cause serious damage to adjacent structures, in-situ abandonment should be considered.
In-situ abandonment is the process of rendering a UST permanently unusable without extracting the tank. This generally involves:
- Documenting work instructions and all relevant permits prior to the commencement of abandonment works.
- Removing all possible product from the tank using the normal pumping system.
- Disconnecting and isolating dispensers and other above ground pumping equipment.
- Removing any residual product using a pump suitable for a hazardous area and a suction hose and/or spear.
- Sealing all ground level connections to the tank except for the vent. All tank top fittings shall be exposed by excavation.
- Draining and disconnecting all piping.
- Purging the tank of product vapour as per AS4976-2006 requirements.
- Filling the tank with a free flowing inert solid material such as concrete slurry, sand or foam.
- Disconnecting the vent and plugging all tank openings.
- Removing all redundant piping associated with the tank. Any pipe that is impossible to be removed shall be isolated, drained and plugged at both ends.
- Notifying the applicable authority and if required, adjusting licenses, manifests and other documentation as required.
- Documenting the procedure in a written report
After in-situ abandonment, the underground storage tank and associated pipework must be investigated for any contamination and a site validation report must be prepared and submitted to the local authority within 60 days from abandonment. The report must clearly state the fact of in-situ abandonment and include a site drawing showing the location of all equipment and the system’s remaining infrastructure. It must also contain a clear conclusion about the site’s suitability for continued or proposed future land use.
For further information on what is required in removing or in-situ abandoning a tank please contact Australian Enviro Services.