Silage Slurry and Agricultural Fuel Oil (SSAFO) storage

Regulations regarding the design, location, construction and maintenance of silage, slurry and agricultural fuel oil stores, to prevent water pollution and how these are enforced by Northern Ireland Environment Agency (NIEA).

Regulations regarding Silage, Slurry and Agricultural Fuel Oil (SSAFO) storage

Under The Control of Pollution (Silage, Slurry and Agricultural Fuel Oil) Regulations (Northern Ireland) 2003  farmers must notify NIEA of any SSAFO store constructed, or substantially enlarged on or after 21 July 2003. They regulate the design, location, construction and maintenance of silage, slurry and agricultural fuel oil stores to stop water pollution.

The NIEA provide a SSAFO Notification form for notification purposes.

Slurry storage tanks

The base and walls of the slurry storage tank, any effluent tank, channels and reception pit as well as the walls of any pipes must be leak-proof. In addition, no part of the system can be put within 10 metres of a waterway.

All storage tanks must be fitted with two valves, in a series, with each valve capable of stopping the flow of slurry through the pipe.

The regulations also introduce the idea of 'freeboard'. This is the minimum distance allowed between the top of the tank and the surface of the slurry in the tank. This is to allow for rainfall, which could cause a tank to overflow if the tank was filled to the brim. In the case of earth banked slurry stores, the minimum freeboard has to be 750 millimetres otherwise it should be 300 millimetres.

Fuel oil stores

New, reconstructed or enlarged fuel oil stores are to be protected by a bund (another enclosure, or tank, around the tank which will contain any spills or leaks) holding 110 percent of the volume of the tank. The bund and the base of the storage area must be leak proof and designed and constructed so that, with proper maintenance, they will remain leak-proof for at least 20 years.

The regulations concerning fuel oil storage do not apply if the total amount of oil stored on the farm does not exceed 1,250 litres.


The base of the silo, where the retaining walls are made from something other than earth, has to extend beyond the walls and be provided with waste collection channels. These channels must drain to a waste tank. The base of the silo, the base and walls of its waste tank and channels, and the walls of any pipes have to be leak-proof and resistant to silage waste.

The silo has to be designed and constructed so that with proper maintenance it is likely to last at least 20 years.

Baled silage

Baled silage should not be stored or opened within 10 metres of a waterway (including field drains). This rule is designed to lessen the chances of acidic and highly polluting silage accidentally entering any nearby waterway in the case of a spill or rupture of any silage bales..


If, on inspection by NIEA, existing or new stores pose a risk of water pollution we may issue a Notice to require their repair or improvement. Farmers can appeal to the Water Appeals Commission against such a Notice if they consider the Notice unreasonable.

Exemptions to regulations

All structures are exempt under the regulations if their construction was completed before 1 December 2003. A structure can cease to be exempt if:-

  • any requirement of a Notice is not complied with within the period stated in the Notice
  • a structure has been substantially enlarged
  • a structure has been substantially reconstructed






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