Prevent groundwater pollution from underground fuel storage tanks

Installing an underground storage tank

How to install an underground storage tank, pipes and related equipment.

You should see the Blue Book for detailed technical advice on how to install tanks and related equipment.

Get planning permission

You need planning permission from your local planning authority to install a new underground storage tank (UST) system (the tank plus any equipment connected to it). You’ll need planning permission for individual tanks, but if changing pumps you may not - check with your local planning authority. You’re likely to need to send your environmental risk assessment with your application.

If your plans could significantly affect the environment, including the potential to cause groundwater pollution or affect nearby conservation interests, your local planning authority is likely to consult the Environment Agency or Natural Resources Wales (NRW). The Environment Agency and NRW may require specific controls or may object to your plans if you choose a site:

Section D (particularly D2 and D3 and the supporting text) of the Environment Agency’s approach to groundwater protection states its position in relation to the storage and transmission of pollutants including USTs. If the Environment Agency or NRW believes that the conditions your local planning authority set won’t minimise the risk to groundwater it may impose restrictions, eg require you to have an environmental permit with additional conditions.

Risks to groundwater and good practice when designing a system

You should consider the potential environmental risks when designing and constructing a facility. If you don’t, you risk causing a significant pollution incident.

When designing a new system you’ll need to assess any new risks alongside your overall existing risk assessment for the facility.

Design and site selection

You need to design the facility so that it reduces the potential groundwater pollution and health and safety risks. As part of your design and before installing a UST you need to consider the:

  • site’s environmental suitability
  • tank design
  • tank contents
  • pipework
  • materials used to construct the tank and associated pipework
  • environmental measures you’ll use, eg wetstock reconciliation

You should also consult the Environment Agency or NRW on where to site your UST before you install it. You should include in your risk assessment and say how close the tank will be to:

  • local watercourses
  • sensitive groundwater locations
  • public and private water abstraction points
  • environmentally sensitive areas (eg sites of special scientific interest)

You should also identify and include in your risk assessment:

  • the site’s geology and hydrogeology (both local and regional)
  • the proposed site layout and the equipment requirements
  • subsurface site layout and equipment requirements
  • historic site activities (including if there are any existing USTs)
  • whether the ground needs a specific type of foundation
  • how corrosive the soil is
  • groundwater conditions (eg anticipated depth to groundwater, including seasonal variations)

The Environment Agency or NRW will want to make sure that you have environmental controls in place if the groundwater is considered by the Environment Agency or NRW to be:

  • sensitive or vulnerable to pollution
  • in a groundwater source protection zone
  • shallow at the location

The Environment Agency or NRW may also oppose you installing the UST (for example if you’re in a Source Protection Zone (SPZ)). See section D of the Environment Agency’s approach to groundwater protection to find out when this may affect you.


You must have an experienced person supervise all on-site works so that the system is installed as agreed. If you don’t construct the facility correctly (eg through unsealed joints) you could lose fuel when the system’s used.

You must:

  • make sure that any protective coatings applied to the tanks and pipework aren’t damaged during installation
  • inspect protective coatings during and after installation
  • repair any damage to protective coatings immediately and before the excavation is filled in again

To minimise the risk to groundwater you should check and put in your risk assessment:

  • that the proposed tanks and pipework are appropriate for the site’s environmental setting
  • if the ground conditions mean that a specific foundation type is needed
  • the depth to the groundwater
  • if ground conditions are likely to corrode below-ground construction materials
  • if the site layout will create specific risks
  • where the surface water will drain to

You should make sure each of the following are correctly installed and secure against leaks and spills:

  • the tank
  • pipes
  • the leak detection system
  • the fuel dispensers
  • the drainage system - including oil separators
  • delivery areas

You should also carry out quality checks and get them certified by the experienced person before you use the tank.

Install the tank

All new tanks should:

  • be double-skinned (have an inner and outer skin)
  • have a class 1 or class 2 leak detection system (such as interstitial monitoring) that meets European standard EN13160

Doing this means that your tank is constantly tested for its life and the system will alert you if the inner skin fails. You can get more details on leak detection systems can in the Blue Book.

You must make sure that your UST has:

  • an access chamber to contain any leak or spill until you can clean it up
  • overfill prevention

Materials you can use for your UST include:

  • double-wall steel in line with EN12285-1
  • double-wall glass reinforced plastic (GRP)

If you use steel tanks the Environment Agency or NRW may need you to install effective and durable anti-corrosion measures. You can get more details in the Blue Book.

Install pipes

You should make sure that pipes meet the British Standard BS EN 14125 and are suitable for the particular UST system. They should be:

  • strong enough to cope with internal and external pressures
  • strong enough for handling and loading
  • compatible with the materials they’re carrying and any other materials they come into contact with through the ground or tanks
  • with correctly formed and sealed joints - ideally you should have as few joints as possible to minimise corrosion risk

You should install pipes above ground if possible, using ducts where they can be easily inspected (unless this causes a health and safety or fire risk).

If you have no alternative and have to bury pipes, you should:

  • use double-skinned pipes with interstitial monitoring (this will alert you to leaks before any product escapes into the soil)
  • avoid using joints, bends and fittings that can be mechanically dismantled

Install dispensers

You should install fuel dispensers where they won’t be damaged (eg in areas with low risk of vehicle collision).

You should also make sure that they meet British Standards (see the Blue Book for this information).

Prevent accidents in delivery areas

You should design your delivery area to make sure:

  • they’re large enough that vehicles can unload without difficulty
  • tanks don’t overfill - use automatic shut-off valves or electronic alarms to limit the amount of fuel delivered into the tank

Install a leak detection system

You need to have a leak detection system in your UST system - you can get detailed information on what you need in the Blue Book.

You should choose a system that offers the right level of protection for the site based on the site’s environmental sensitivity. You can get information on the groundwater vulnerability and environmental sensitivity of a particular site.

Make sure you choose a robust and accurate leak detection system that should allow you to monitor any product losses. You should use it along with other systems and checks to carry out wetstock reconciliation.

You must make sure that only trained people operate your leak detection system.

Sites in groundwater source protection zones

If your site is in an SPZ, you may need a more responsive wetstock management system to reduce the risk of pollution. For example, statistical inventory reconciliation, which enters wetstock figures into a statistical model every day and identifies small leaks of a few litres a day.

You should also install boreholes for groundwater monitoring around the UST and collect samples from the boreholes regularly. You can agree monitoring schedules with the Environment Agency and NRW.

Install a drainage system

You should have properly designed drainage systems and maintain them. You should make sure your drainage system:

  • contains all surface spills
  • doesn’t discharge contaminated site water to surface watercourses, soakaways or the ground - use waterproof surfacing in any places where loss of fuel could happen
  • carries surface water run-off to an appropriately designed oil-water treatment system (eg a separator)
  • is made from materials that are resistant to attack by hydrocarbons (this includes both the hardstanding and pipework)

Drainage systems you can use

There are 2 types of drainage system you can use:

  • separate systems
  • combined systems

Separate systems

Separate systems have 2 drains:

  • foul sewer carrying contaminated water (sewage or trade effluent, like vehicle wash water) to a sewage treatment works
  • surface water drains carrying uncontaminated clean water (drainage from roof or clean yard areas) connected directly to the water environment

Combined systems

Combined systems have one sewer carrying both foul and surface water to a sewage treatment works.


You can fit oil separators to surface water drains to prevent pollution by oils by separating and storing oil from water. These will help contain any oil leaks from vehicles, plant and accidental spillages.

You must correctly design, install and maintain oil separators for them to work effectively.

Carry out checks before you use the UST

Before you use a new underground storage tank you should make sure:

  • all valves, fill pipes and vent pipes are clearly identifiable, as set out in your management system
  • monitor any wells you’ve installed are identifiable, as set out in your monitoring or management plan

Before operating your UST you should carry out the following checks:

  • complete and test drainage systems, including separators, and discharges that need to be completed and tested - these tests should be carried out by a qualified drainage consultant
  • charge separators with water so you can start using them
  • seal electrical and other ducts
  • make sure tanker stands are installed and forecourt areas are completed
  • make sure any emergency equipment is installed and ready to use

You should record the outcomes of all these checks in your EMS.

You should also test the following for integrity and safety (see the Blue Book for advice on how to do so):

  • tanks
  • pipes
  • fuel dispensers
  • manhole chambers

If you’re using your tank to store petrol, you’ll need to carry out these tests before you can get a petroleum storage licence. You must keep any certificates for the tests on site for inspection.