Underground Storage Tanks

ASSESSMENT & REMEDIATION

Most UST's are used for petroleum products but they are also used for the storage of many other liquids.

Petroleum leaking from UST's moves downwards and outwards from the source to form a plume. If ground water is present the contamination tends to float and to move in the direction of ground water flow, contaminating the ground water as it spreads. Fluctuating ground water levels smear the petroleum out over the range of fluctuation. The contamination travels much faster in sandy soils than in clay soils, fault or fissures allow for fast migration. A trench made for a pipe or electrical cable and backfilled with sand provides an excellent conduit for the migrating petroleum which can spread quickly by this method.

DECOMMISSIONING

UST's may be left in place indefinitely provided they are appropriately decommissioned. Such a strategy is satisfactory in some instances but it does have limitations. If the tank has already leaked contamination might be slowly moving off site and/or contaminating the ground water. Expensive remediation or litigation from a neighbour can result. Decommissioned UST's are a liability when the site is being sold.

REMOVAL

Removal is the preferred option and is mandatory in many cases. Issues involved with removal include:

• Pumping out and disposal of contents.
• Explosivity - making the tanks safe and monitoring the atmosphere for explosivity. Fuel vapours mixed with air can explode with great violence.
• Removal and disposal of the tanks, associated fuel lines and dispensers.
• Soil sampling of the excavated pit and along fuel lines according to EPA Guidelines.
• Soil remediation if necessary.
• Final sign off validation that the site is clean.
  

GUIDELINES

Australian Institute of Petroleum Code of Practice "The Removal and Disposal of Underground Petroleum Storage Tanks AIP CP22 - 1994".
NSW Environmental Protection Authority (EPA) "Contaminated Sites, Guidelines for Assessing Service Station Sites", 1994.

HOW CAN NEW ENVIRONMENT HELP?

New Environment provides a full range of consulting and monitoring services in relation to UST decommissioning and removal, from explosivity testing through to full decommissioning, soil assessment and final sign off validation reports.