Underground Storage Tanks

An underground storage tank (UST), as defined by Australian Standard AS1940-1993,  is a system in which a tank is installed either totally or partially below ground. The terms underground storage system (USS) and underground petroleum/fuel storage system (UPSS) are also used to describe the associated tank infrastructure including the delivery systems (e.g. dispensing pumps and piping), tank filling point, dip points, vent lines, vapour recovery systems, tank anchor and electrical cabling. Underground storage tanks are commonly associated with the storage of petroleum products (e.g. petrol or diesel fuel) and are considered a major source of soil, surface and groundwater contamination. This is due to the potential for leaks to occur. Fluid loss from a UST can be difficult to detect as the tank and infrastructure is located underground, making inspections difficult. HRS can assist with:

  • Investigations
  • Removal
  • Monitoring

 

Investigations

Site investigation may be required as a result of known or suspect loss of product from the USS; it may be required when a lease is transferred, as part of due-diligence or if the site is to be redeveloped for a more sensitive land use. An underground storage tank or system may have been installed on your property long before you purchased the land and you may not even be aware it exists however current legislation requires that you inform any potential purchasers of the property that an UST or USS exists on the site. The Contaminated Sites Act may even hold you liable for the clean-up of contaminated sites and water resources if the tank is leaking, unbeknownst to you. Clean-up and treatment of polluted sites, particularly as groundwater migrates can be difficult and expensive. If you suspect an underground tank may be located on your site contact HRS for advice or a preliminary site inspection.

Monitoring

The WA Dangerous Goods Safety Regulations (2007) requires that all underground storage systems need to monitored or tested by some means every 2 years. Monitoring a USS/UPSS can be done in a number of ways, such as automatic tank gauging systems (directly tests the integrity of the tank and piping through leak detection, overfill alarms, automated processes to monitor product level and inventory control or interstitial monitoring); soil vapour monitoring probes (an indirect method that tests the vapour content within soils) or groundwater monitoring wells (another indirect method that tests the groundwater beneath the site for contamination). Monitoring is necessary to prevent contamination to the environment, prevent potential human health issues (drinking waters, vapour intrusion, etc.), help maintain property values and to avoid delays or unforeseen costs during sale (due to the contamination risk posed by a USS on a site a mortgage lender may require an Environmental Site Assessment prior to granting a loan). HRS performs regular tank monitoring via groundwater monitoring wells at several well-known locations across Perth including marinas along the Swan River.

Removal

If a UST is no longer being used for its originally intended purpose WA environmental guidelines recommend that the tank and all associated infrastructure be removed by a qualified site contamination consultant. Unfortunately removal of a UPSS can be expensive. However this needs to be considered against the cost of clean-up and treatment of polluted sites, which can be difficult and expensive, and the fall in your property’s value or desirability due to the contamination risk posed by USS. Tank removal requires the tank to be drained and contents disposed of at an approved facility. The surface needs to be taken up, the soils surrounding the tank excavated and the tank and soils removed, transported and disposed of by licensed operators at licensed facilities. The excavation pit needs to be backfilled using clean soils and the area resurfaced. Soil and groundwater sampling is required by the Department of Environment Regulation to confirm no product has leeched into soils or groundwater whilst the tank was underground. Upon completion, any existing Department of Mines and Petroleum Dangerous Goods Licenses held against the site can be removed by the DMP.