British Standards Relevant to Agriculture

 

British Standard Summaries

BS5502: Part 50: 1993
Building and Structures for Agriculture
Code of Practice for Design, Construction and Use of Reception Pits & Storage Tanks for Livestock Slurry

The text herein is not a a full reproduction of the British Standard. It is summary based upon interpretation of the original text and not intended as a replacement for the full text. It should be used for general guidance only.

BS5502 is sub-divided into a number of individual standards. These can be broadly broken down as follows:

  • Part 0: Introduction
  • Parts 10 - 19: Reference information
  • Parts 20 - 39: General designs
  • Parts 40 - 59: Livestock buildings
  • Parts 60 - 79: Crop buildings
  • Parts 80 - 99: Ancillary buildings

This standard supersedes BS5502: Part 50 1989 which has been withdrawn. The Standard aims to give recommendations for the design, construction and use of agricultural storage tanks and reception pits for livestock slurry. For full details see BSI standard. The following text outlines the salient points:

General

When siting the tank the following must be considered:

  • The official classification of the building must be considered (special conditions apply to certain structures).
  • The risk of odour nuisance.
  • Any adjacent structures particularly protected buildings.
  • The risk of water pollution.
  • The risk of accidental impact of vehicles.
  • The site ground conditions.
  • Nuisance from odours must be minimised by siting storage tanks away from housing and consider prevailing winds.
  • Slurries have a high BOD and all precautions to prevent it entering watercourses must be made. Adequate sizing of tanks to prevent accidental overflow is needed.
  • Minimum requirements for the siting, sizing, and constructional requirements are given in Control of Pollution (Silage, Slurry and Agricultural Fuel Oil) Regulations 1991.

The building

  • Tanks must be sized by considering the quantities of slurry and dirty water generated and the frequency at which slurry can be safely disposed of. Provision for at least 4 months storage is required in England and Wales where safe disposal is not possible during the winter months. Allowances should also be made for rainfall and for the freeboard. The Standard gives specific guidelines for sizes.
  • Estimates of waste and dirty water can be made from standard figures but these must always be checked against individual installations.
  • Reception pits should be capable of storing a minimum of two days waste.

Loads

  • The principal loads of slurry storage tanks and reception pits are from internal slurry pressure, wind loads on above ground tanks, external earth pressures, groundwater pressure and the loads on the pit cover.
  • Slurry should be treated as an isotropic liquid with a relative density of 1.1.
  • Details for calculating the internal pressure of the tank are given in the full standard.
  • Wind loads can be calculated from information given in BS5502:22.
  • Pressure of the external wall surface of the pit will depend on the characteristics of the soil, other backfill, level of the watertable and on the surcharge conditions of the surrounding ground.
  • Accurate loading data requires a soil survey.
  • Formula for calculating the loads from soil or backfill are given in the full Standard.
  • Formula for calculating surcharge conditions from point loads , uniform loads and isolated foundation bases are given in the full standard.
  • Formula for calculating the upthrust on floors are given in the full standard.
  • Reception pit cover/grid loadings should be calculated from information given in BS5502:22.

Structural design

  • Slurry storage tanks, reception pits and their covers should be designed to the recommendations given in BS5502:22 with a usual minimum class 2 building classification (there are some specified exceptions to this classification).
  • Reception pits and tanks should be designed to resist flotation induced by groundwater pressure.
  • Floors, walls and joints must be impermeable.

Materials

  • All materials and components used in the construction must comply with the relevant British Standard.
  • Materials and components should have a life span of no less than 20 years.
  • All internal surfaces must be protected against corrosion and degradation. The slurry should be assumed to have a pH of 6.0-9.0.
  • Concrete surfaces should be designed according to BS8007.
  • Masonry should be designed and constructed to E3 exposure as defined in BS5628.
  • Galvanised surfaces should be cleaned and painted with a suitable resistant coating before use.

Safety

  • The atmosphere within slurry storage tanks and reception pits may contain insufficient oxygen to support life. If they may also contain noxious and explosive gases. A fire risk may also exist.
  • All open or accessible structures must be surrounded by a childproof fence at least 1.3m above ground. If less than 2m it should be topped by barbed wire.
  • Access to the tank rim must be by portable ladder or a combination of portable and fixed access ladders on which the lowest rung is not less than 2.4m or more than 3m above ground.
  • Guard-rails must be provided around working platforms.
  • Safety and warning notices should be in accordance with BS5502:20.
  • A handbook for the user should be provided.

A British Standard nor this summary does not, necessarily, include all the necessary information for correct implementation of the Standard to any specific application. This is purely the responsibility of the user. Standards are updated by either amendment or revision. Users should ensure that they are using the latest version.


 

The full text of this Standard can be obtained from the British Standard Institution

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