# The Water Resources (Control of Agricultural Pollution) (Wales) Regulations 2021, Paragraph 4

Extent: E+W

(1) The base of the silo must be—
(a) designed in accordance with the code of practice for design of concrete structures for retaining aqueous liquids published by the British Standards Institution and numbered BS 8007: 1987, or
(b) constructed using appropriate hot-rolled asphalt in accordance with the code of practice for selection and use of construction materials published by the British Standards Institution and numbered BS 5502: Part 21: 1990.
(2) The base of the silo, the base and walls of its effluent tank and channels and walls of any pipes must be impermeable.

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Source: https://www.legislation.gov.uk/wsi/2021/77/schedule/5/paragraph/4 (the official version)
Page: https://openlegislation.uk/water-resources-control-of-agricultural-pollution-wales-regulations-2021/schedule-5/paragraph-4
Contains public sector information licensed under the Open Government Licence v3.0. Source: legislation.gov.uk, The National Archives.