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.
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.
Explanation of terms
The following terms are included below to provide clarity to their meaning in this Technical Handbook.
Catchpit - means a pit, without a drain, which is capable of containing 110% of the containers storage capacity with base and walls that are impermeable to water and oil.
Integrally bunded tank - means a tank together with a catchpit manufactured as a self-contained unit.
Woody biomass fuel is unlikely to be locally sourced, except for chopped firewood, and for large installations is likely to be delivered in bulk. If the storage container is too small, the number of journeys by delivery vehicles will make unnecessary use of diesel fuel. Wood chips tend to be used in large boilers supplying heat to district heating systems rather than to individual houses. Information on woody biomass fuel can be found on the BSD website under: ‘Storage of woody biomass fuel for heating equipment’ http://www.scotland.gov.uk/topics/built-environment/building/building-standards.
Conversions - in the case of conversions, as specified in regulation 4, the building as converted shall meet the requirement of this standard (regulation 12, schedule 6).
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 of more than 2500 litres, and their associated pipework must be installed in accordance with the requirements of Regulation 6 of The Water Environment (Oil Storage)(Scotland) Regulations 2006. Oil storage containers up to 2500 litres serving domestic buildings will be deemed to be authorised if they comply with the building regulations.
Tanks with a capacity of more than 90 litres but not more than 2500 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.
Reference should be made to the Scottish Executive Code of Practice, Underground Storage Tanks for Liquid Hydrocarbons (2003/27). This CoP provide guidance on underground and partially buried oil storage tanks. The CoP is currently being updated to be consistent with The Water Environment (Controlled Activities)(Scotland) Regulations 2005 and will be issued by SEPA. SEPA also provide guidance in PPG 27, (Installation, Decommissioning and Removal of Underground Storage Tanks).
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.
Externally located, above ground, oil tanks with a capacity of not more than 2500 litres serving a domestic building should be provided with a catchpit or be integrally bunded if subject to any of the hazards described below:
tank located within 10m of the water environment (i.e. rivers, lochs, coastal waters)
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.
OFTEC Technical Book 3 provides a simple and helpful cross check to the above list.
A catchpit or integrally bunded tank should be provided in accordance with the recommendations of OFTEC Standard OFS T100 and OFS T200; and Clause 6.5 of BS 5410: Part 1: 1997.
Secondary containment should also be provided where a tank is within a building or wholly below ground.
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 that 3 months for bulk storage and 6 months for small installations.
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 recommended size of storage for a variety of different dwelling types that will permit a large enough volume to be delivered whilst minimising vehicle movements. Advice on the sizing of storage for woody biomass fuel for larger buildings is provided in the non-domestic Technical Handbook.
Table 3.19. Bulk woody biomass fuel storage: 100% heating (primary) and DHW
|Dwelling size||Wood pellets||Wood chips||Logs - stacked|
The figures in the table relate to deliveries made every 3 months.
The guidance to Standard 6.2 suggests that to achieve the carbon emissions target, designers and developers may use on-site renewable energy technologies to supply up to 10% of the annual heating demand, rather than adopting slightly more demanding insulation standards for walls. A small woody biomass stove or boiler could provide this level of heating.
The following table provides recommended size of storage for secondary heating for a variety of dwelling types:
Table 3.20. Woody biomass fuel storage: secondary heating
|Dwelling size||Wood pellets||Wood chips||Logs - stacked|
|< 80m2||0.3m3 (9 bags)||1m3||0.5m3|
|80 - 160m2||0.5m3 (13 bags)||1.5m3||1m3|
|> 160m2||0.7m3 (16 bags)||2m3||1m3|
The figures in the table relate to deliveries made every 6 months.