3.24 Fuel storage – containment
Oil is a common and highly visible form of water pollution. Because of the way it spreads, even a small quantity can cause a lot of harm to the aquatic environment. Oil can pollute rivers, lochs, groundwater and coastal waters killing wildlife and removing vital oxygen from the water. Large quantities of water are taken from rivers and groundwater for use as drinking water and for irrigation. Oil contamination can make water unfit for these purposes.
Oil accounts for about a third of all reported pollution incidents in Scotland that are investigated by SEPA each year. That means around 500 to 600 pollution incidents a year with about 10 to 12% being serious. It is an offence to cause pollution and courts now impose heavy fines.
Oil is a ‘List I’ substance within the meaning of the EC Groundwater Directive (80/68/EEC). The UK government is required by this directive to prevent List I substances from entering groundwater and to prevent groundwater pollution by List II substances.
The storage of oil is a controlled activity under the Water Environment (Controlled Activities)(Scotland) Regulations 2005 and will be deemed to be authorised if it complies with The Water Environment (Oil Storage)(Scotland) Regulations 2006. Enforcement is by SEPA.
Fixed oil storage tanks between 90 and 2500 litres and the fuel feed system connecting them to a combustion appliance should be strong enough to resist physical damage and corrosion so that the risk of oil spillage is minimised. Tanks should be constructed in accordance with:
the recommendations of BS 799: Part 5: 1987, for a steel tank, or
the recommendations of OFTEC Technical Standard OFS T200, for a steel tank, with or without integral bunding, or
the recommendations of OFTEC Technical Standard OFS T100, for a polyethylene tank with or without integral bunding, or
a European harmonised product standard and assessed by a notified body.
Tanks with a capacity more than 3500 litres and the fuel feed system connecting them to a combustion appliance should be installed in accordance with the recommendations of BS 5410: Part 2: 1978.
Small tanks - tanks with a capacity of more than 90 litres but not more than 3500 litres and the fuel feed system connecting them to a combustion appliance should be installed in accordance with the recommendations of BS 5410: Part 1: 1997.
Underground tanks - reference should be made to the Code of Practice for the Owners and Operators of Petrol Stations and Other Fuel Dispensing/Storage Facilities Involving Underground Storage Tanks. This CoP provides guidance on underground and partially buried oil storage tanks. The Scottish Executive has also produced a code of practice for owners and operators of underground storage tanks under the Groundwater Regulations.
Care should be taken to prevent leakage from pipework. Pipework should be run so as to provide the most direct route possible from the tank to the burner. Joints should be kept to a minimum and the use of plastic coated malleable copper pipe is recommended. Pipework should be installed in accordance with the recommendations in BS 5410: Parts 1: 1997 and Part 2:1978 and OFTEC Technical Book 3.
It is necessary for a wide variety of possible hazards to be considered as to whether a catchpit (bund) is required or not. BS 5410: Part 1: 1997 highlights 2, as the size of the tank and its proximity to a watercourse. However other potential hazards should be borne in mind and a risk assessment should be carried out for each installation. It is preferable for installers to keep a record of this and OFTEC Technical Book 3 provides a simple crosscheck. The full list of potential hazards listed by OFTEC are:
tank within 10m of a watercourse
tank located where spillage could run into an open drain or to a loose fitting manhole cover
tank within 50m of a borehole or spring
tank over ground where conditions are such that oil spillage could run-off into a watercourse
tank located in a position where the vent pipe outlet is not visible from the fill point
any other potential hazard individual to the site.
Catchpit (bund) - if any of the above conditions apply, the oil storage tank should be provided with a catchpit. A catchpit means a pit, without a drain, which is capable of containing the contents of the tank, plus 10%.
An integrally bunded tank is a tank, together with a catchpit, manufactured as a self-contained unit complete with a removable lid and designed to contain the escape of any liquid escaping from the tank in an overfill situation.
A catchpit or integrally bunded tank should be provided in accordance with the recommendations of OFTEC Standard OFS T100 and OFS T200 and
for tanks with a capacity of more than 3500 litres, clause 45.3 of BS 5410: Part 2: 1978
for tanks with a capacity of not more than 3500 litres, clause 6.5 of BS 5410: Part 1: 1997.
A catchpit should also be provided in the following situations:
Table 3.22. Provisions of a catchpit
|Location of tank||Catchpit or integrally bunded tank|
|Within a building||recommended|
|External, above ground (2500 litres or less)||in accordance with clause 3.24.3|
|External, wholly below ground||not required|
In order to best exploit the advantages achieved through the use of woody biomass as low carbon technology it is recommended that wood fuel storage provision is of a size that will ensure bulk deliveries need not be made at intervals of less than 1 month.
Deliveries of wood pellets may be less frequent than deliveries of wood chips because pellets can have 3 times the calorific value of dry wood chips. Alternatively, the storage volume can be smaller for the same energy capacity.
The following table provides recommendations for some building types of varying size on the storage recommendations that will permit a large enough volume to be delivered whilst minimising vehicle movements. The table is intended to provide an estimate of fuel storage based on heat demand and to help with initial studies. A more systematic exercise should be carried out during development of the scheme design. Advice on the sizing of storage for woody biomass fuel for smaller buildings is provided in the non-domestic Technical Handbook.
Table 3.23. Woody fuel storage recommendations for 100% heating
|Building type (m2)||Heat demand (annual)||Wood chips||Wood pellets|
|MW hours||Fuel required (m3/year)||Storage||Fuel required (m3/year)||Storage|
|Education (400-2000)||90-450||110-565||10-60 m3||40-210||5-20 m3|
|Industrial (100-2000)||20-360||25-450||5-55 m3||10-165||5-20 m3|
|Office (100-2000)||20-420||25-525||5-55 m3||10-195||5-15 m3|
Figures represent monthly deliveries.
The storage recommendations relate to buildings constructed in accordance with the guidance in the 2007 edition of Section 6, Energy. Storage for buildings constructed to higher standards of energy conservation may be reduced, whilst storage for buildings constructed to earlier standards should be increased to equivalent.
Recommended storage capacity to meet 100% of the space and DHW heating demand assuming storage capacity is 25% larger than delivery size.