Oil is a highly frequent and problematic land contaminant with the potential to damage the environment, killing plants and animals, pollute water supplies and release sometimes dangerous vapours if it migrates into or under buildings. At the same time, oil remains a key source of fuel for home heating, especially in off-grid areas and for businesses.
Safe storage is key, with up to 3,000 oil pollution incidents every year reported to the UK Environmental Agencies every year, around eight incidents every day (with the likelihood that many more go undetected or unreported).
The cost of cleaning up toxic spills can amount to tens of thousands of pounds. This combined with the potential health hazards and disruption make it essential to ensure storage tanks and associated pipework are secure and well maintained to minimise leakage.
Staying within the law
In England, under the Oil Storage Regulations (2001), containers with a capacity of 200 litres or more (public, commercial or industrial sites) or 3,500 litres at a domestic dwelling must be stored in a bunded tank, bowser or other container with secondary containment, with certain exceptions e.g. farms, underground storage and at refineries and distribution sites.
While there are some differences in regulations in Scotland and Wales, the aim of the legislation remains the same: to minimise the risk of oil escape during storage and the subsequent need for lengthy soil remediation.
Oil tanks can leak for a variety of reasons; the most common being:
- failures of the tank body.
- damage to equipment on the tank such as sight gauges.
- damage to or wear-and-tear of fuel feed lines.
- failure of components at the boiler end of the system, such as flexible hoses.
Over the past twenty years or so there has been growing recognition that double skinned, or self-bunded, plastic oil tanks offer a far higher degree of prevention of loss than single skinned tanks.
To minimise the risk of pollution from an oil spill, installations near a river, well or any Controlled Water source are further required to have secondary containment measures in place. (In Wales, this requirement now applies to ALL new oil tanks, regardless of the environmental sensitivity of the site).
This can be achieved by either choosing an integrally bunded tank or constructing a bund around a tank. The bund must be capable of holding at least 110% of the tank’s contents. Most commonly this is now in the form of a double-skinned plastic tank; however integrally bunded metal tanks, and metal outer tanks with an inner plastic tank, are also available.
Safety from the bottom up
Even a moderately sized oil tank will hold over a tonne of kerosene when full. If an oil storage tank is not adequately supported, the tank itself can be weakened leading to the eventual failure and escape of the stored fuel. During the life of an installation an oil storage tank base will need to provide continual structural support, even though ground conditions may alter from season to season and year to year. Choosing a suitable base and support for the oil tank are therefore paramount, both for safety and environmental protection. It is important to ensure the base is:
- Adequate for the weight of the tank
- Non-combustible, imperforate and level
- Constructed of concrete, paving stones or stonework
- Large enough to extend 300 mm beyond all sides of the tank.
Locating your tank safely
Contrary to popular belief, a fire is unlikely to start with the oil storage tank. Building Regulations contain very specific requirements about tank locations in relation to buildings and boundaries, with precise separation distances designed to protect the stored fuel being ignited by a fire that may originate nearby.
The regulations call for tanks to be sited:
- 1.8m away from non-fire rated eaves of a building
- 1.8m away from a non-fire rated building or structure (e.g. garden sheds)
- 1.8m away from openings (such as doors or windows) in a fire rated building or structure (e.g. brick-built house or garage)
- 1.8m away from oil fired appliance flue terminals
- 760mm away from a non-fire rated boundary such as a wooden boundary fence
- 600mm away from screening (e.g. trellis and foliage) that does not form part of the boundary.
If it is impossible to comply with these requirements, then a fire protection barrier with at least 30 minutes fire rating should be provided. A minimum separation distance of 100 mm is required between the tank and fire rated barrier unless a larger distance is specified by the tank manufacturer.
If the tank must be located inside a building such as a garage or outhouse the tank should be self-contained within a 60-minute fire rated chamber.
It is also important to bear in mind local requirements, since oil storage tank installations also need to comply with regional Building Regulations. In England and Wales, OFTEC registered technicians (and some engineers registered with alternative ‘Competent Person’ schemes) can self-certify their own work without involving Local Authority Building Control. Installations by other engineers will require a Building Control Notice and inspection.
Getting to the bottom of oil leakages
Despite the introduction of the oil storage regulations, we still attend many domestic oil leaks and spillages every year.
As a UK Spill Accredited Contractor, Ecologia is required to compile data on oil spills that we attend to. The chart below shows how the percentage of incidents that Ecologia deals with has changed across four broad categories since 2008, in terms of principle causation.
Although the Oil Storage Regulations appear to have had an impact, around 30% of the cases that we attend (and there are many) are still the result of a failed single-skinned tank. The benefits of installing a bunded/double-skinned tank are clear, with very few incidents of oil leaks occurring from these.
While the oil tank is the part that most people pay attention to, as the most visible part of the oil storage infrastructure, it is also important to consider other aspects of the wider installation. 70% of cases that we attend are the result of a pipework failure or `other cause’. These include:
- Corroded filter bowl
- Accidental damage to oil lines whilst gardening
- Accidentally driving into oil tanks near driveways
- Spillages during oil deliveries
- Lightning strikes
- Subsidence causing damage to buried pipework
- Oil tanks being floated during flash flooding
- Tank bases collapsing due to flask flooding
- Incorrect installation – poor connections
Fundamentally, despite progress in reducing the risks associated with oil storage, leaks and spillages WILL happen – and when they do, Ecologia are always ready to help!
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