Farm Waste Structures: Guidance on Construction, Repair and Maintenance

Bunds for agricultural fuel oil tanks

Note No: CGN 009, July 2000
Prepared by ADAS National Building Design Team. Funded by The Department for Environment, Food & Rural Affairs.

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A bund provides containment for any loss of oil from a storage tank and associated pipe-work. It should consist of a base and surrounding walls that must be constructed of, or lined with, a material impermeable to the oil stored. The bund must contain at least 110% of the tank capacity.

Click to enlarge the image

  • The sketch typifies reinforced masonry construction of a bund wall for a single tank of up to 10 cubic metres capacity. It is provided for guidance purposes only.
  • Support tanks on walls or cradles properly designed to spread the weight over the width of the floor slab area. Un-roofed tanks should have a sump in the floor for emptying rainfall (see Reference 5).
  • Free draining ground is generally not susceptible to frost heave.

Site Suitability

  • Consult the Environment Agency about the site location.
  • Avoid sites in a flood plain or with a high water table.
  • Avoid, unstable slopes, variations in sub strata, sites likely to subside.
  • Look for a level site with a firm and uniform substrata e.g. firm sandy clay.
  • Good access required for fuel delivery vehicles.



  • Remove all vegetation and organic top soil from the site.
  • Excavate and trim to formation levels. Protect from weather.
  • Remove soft ground, compact and fill with Department of Transport specification type 1 hardcore to formation level or GEN 2 mix concrete to BS5328 (See Reference 5).
  • Spread and compact in uniform layers at least 150mm thickness of Department of Transport type 1 hardcore. Lay 1000 gauge polythene and lap the joints.
  • Compact using vibrating roller to a permissible bearing pressure of more than 200kN/m2.
  • Alternatively use a minimum of 75mm of C20 concrete to BS 8007 or GEN 2 mix concrete to BS 5328, instead of hardcore (See References 6 & 7).
  • Fix wall reinforcing steel accurately in position before casting the floor.
  • Construct the reinforced concrete floor slab to conform to BS 8007. Refer to Leaflet CGN004 for information about in-situ concrete work. Cast the slab in one pour to avoid the need for floor joints. If joints are needed, provide water-bars.
  • Fix in position during casting, a continuous water bar at the base of the wall. Use water-bar to BS 6213; metal e.g. copper or steel strip may be used on stable sites (See Reference 8).
  • Fix horizontal distribution bars to hold vertical bars in place during casting. All horizontal bars must be fixed prior to building the wall.
  • Build reinforced brickwork to conform to BS 5628 (See Reference 9).
  • Use clay, solid class B engineering bricks to BS 3921 Table 1 and Table 6, Class B.
  • Build the cavity wall as shown in bonded stretchers with the two skins tied together with stainless steel cavity ties. Fill and point the external joints. Do not provide a damp proof course (DPC). Keep the cavity clean of mortar droppings.
  • Use cement/lime/sand mortar to BS 5628 class (i) comprising 1 part Ordinary Portland Cement (OPC), 1/4 part hydrated lime and 3 parts sand.
  • Leave small gaps in the brickwork in the bottom course. Use them to clean the cavity prior to infilling, and to check that the infill at wall/floor junction is completed properly. Shutter these during casting to prevent loss of the concrete.
  • Use a RC30 grade concrete to BS 5328 for filling the cavity (See Reference 7).
  • Support brickwork to prevent damage during casting.
  • Uniformly place and properly compact concrete infill in one continuous operation. Take care not to damage or displace the brickwork during the operation.
  • Inspect floors and walls after casting. Make good pinholes and minor defects by bag rubbing with 1 part OPC and 1 part sand as used in the concrete mix.
  • Apply waterproof rendering to the internal surfaces.

Repair and Maintenance

  • Empty rainfall from the bund; rectify tank corrosion and other defects; rectify defects in the bund walls and floor. Inspect preferably on a weekly basis or after heavy rainfall. Oil contaminated rainfall must not be discharged to a watercourse.
  • Refer to CIRIA Report No 126 for information on repair techniques (See Reference 4).


  1. The Control of Pollution (Silage, Slurry and Agricultural Fuel Oil) Regulations 1991 (as amended).
  2. The Code of Good Agricultural Practice for Water; MAFF (Free publication).
  3. Environment Agency Pollution Prevention Guidelines.
  4. CIRIA Report No 126: Farm waste storage- Guidelines for construction.
  5. CIRIA Report No 163: Construction of bunds for oil storage tanks.
  6. British Standard 8007: Code of Practice for design of concrete structures for retaining aqueous liquids; British Standards Institution.
  7. British Standard 5328: Concrete specifications and procedures; British Standards Institution.
  8. British Standard 6213: Selection of construction sealants; British Standards Institution.
  9. British Standard 5628: Code of Practice for Masonry Parts 1, 2 & 3. British Standards Institution.

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