The self-supporting frameless portable temporary oil storage tanks have been designed to meet the most stringent requirements of temporary collected oil storage. In remote areas, the self-supporting tanks are designed for easy setup. The LAT may be filled by pumping collected oil into the self-supporting Onion tank. As the self-supporting tank begins to fill with oil, its unique design allows it to become self-supporting automatically. The LAT does not require any additional supporting framework, assembly, or frame installation. They are ready to be deployed at any time, as they hold themselves up without a frame due to the floating collar which rises as the tank is filled. They include handles at the bottom, allowing the base of the tank to be positioned as required. The LAT tank is manufactured in PVC-coated polyester which is both flexible and oil resistant. All joins are high frequency welded, eliminating the need for seams or adhesives. The tanks’ design, fabric, and manufacturing process make them extremely hard-wearing and suitable for intensive use. All LAT tanks can be folded up to facilitate transport and storage. They are supplied folded inside a carry bag with handles making them easy to carry and deploy.