RP24: Lined biobed plus pesticide loading and washdown area

Find out about eligibility and requirements for the lined biobed plus pesticide loading and washdown area item.

How much will be paid

£118 per square metre.

Where to use this item

Available for Mid Tier and Higher Tier


  • in areas targeted for the reduction of water pollution from agriculture
  • with support from a Catchment Sensitive Farming (CSF) officer

Where this item cannot be used

  • within 10m of a watercourse
  • within 50m of a spring, borehole or well
  • within 250m of a borehole used to supply water for producing domestic food without prior agreement from the Environment Agency (EA)
  • on historic or archaeological features or areas of wildlife value identified on the Farm Environmental Record (FER), the Environmental Information Map or the HEFER
  • without relevant advice, consents or waste exemption from the Environment Agency (EA)

How this item will benefit the environment

This item will contain and collect sprayer and applicator washings and degrade them in a biobed. This will help prevent pesticides from entering drains or water bodies, which will help reduce the risk of water pollution.


  • meet the requirements of the T32 waste exemption
  • meet relevant British Standards - examine copies of the most up-to-date standards for guidance

Loading and washdown area

Install a concrete bunded loading area, holding tanks, and fixed pumps and pipes to remove washings from the tank, as follows:

  • remove topsoil and excavate an area for the washdown area and tank
  • remove or divert any field drains that cross the site
  • cover the site with 140mm to 160mm of well compacted hardcore and at least 25mm of sand blinding
  • lay a damp-proof membrane weighing at least 1200g
  • lay a reinforced concrete slab at least 150mm thick to falls of at least 1:100
  • construct a concrete bund around the perimeter of the slab, making sure that all concrete joints are sealed with a proprietary sealant
  • make sure the bund is at least 100mm high, so that it can contain liquids
  • make sure the concrete bunded area is as wide as the sprayer plus 2m, and as long as the sprayer plus 1.5m
  • make sure the bunded concrete slab contains a slotted-cover type drain connected to a silt trap with a removable cover that has a nominal capacity of 250mm below the inlet
  • alternatively, lay the concrete so it is sloping 4 ways to a drain in the centre of the slab - the drain should have a silt trap within it
  • direct the drain containing the silt trap to a tank or chamber (no larger than 1500 litres) from which pesticide washings can be pumped and disposed of
  • make sure the holding tank is made from seamless polyethylene, glass-reinforced plastic (GRP) or pre-cast concrete
  • make sure the holding tank is sized according to local rainfall and the area of concrete (if there is no roof or cover)
  • make sure the whole structure is impermeable


To construct a below-ground biobed:

  • excavate an area for the biobed
  • remove and block off any field drains
  • compact the sides of the earth bank to a slope of 30 to 35 degrees (about 1 in 1.5) towards the base
  • lay an impermeable synthetic liner at least 1.2mm thick (pesticide grade) on top of a geotextile membrane underlay (190g per square m) and 25mm of sand blinding

To construct an above-ground biobed:

  • use pre-cast or reinforced concrete and a 1.2mm thick liner, or an impermeable pesticide grade container
  • follow the liner manufacturer’s installation instructions

Any necessary holding tanks, pumps and pipes must then be installed for the below or above-ground biobed.

How to install a biobed outlet

To construct a biobed outlet (except for evaporation systems):

  • either insert a drain through the liner to create a 100mm bonded outlet at the lowest point of excavation
  • alternatively:

  • create an internal sump when digging the biobed pit
  • lay the liner to incorporate the sump
  • make sure the liner is not perforated
  • insert a central, permeable, vertical access tube (0.5m in diameter) to allow water to flow into the sump base
  • install a pump within the tube, operated by a float switch setting
  • place a ring of perforated drainage pipe into the base of the biobed on top of the liner to assist the pump flow

  • install pumps to carry the treated discharge from the biobed to a vegetated area for irrigation; or pump it to a storage tank for irrigation or re-use

How to prepare the biomix

  • mix one part peat-free compost, one part topsoil and 2 parts straw (wheat or barley) by volume
  • allow the biomix to compost for 30 to 90 days before using it to fill the biobed to an effective depth of 1m, topping it up if there is any settlement
  • use at least 1 cubic m of biomix for every 1000 litres of liquid treated in any 12 month period
  • turf over the biomix (except for evaporation systems)
  • lay perforated pipes to distribute pesticide washings across the surface

The biobed does not need a cover or roof, unless it is an evaporation system.

How to use evaporation systems (biobeds designed to work by evaporation)

  • cover the biobed with roof sheeting, using side ventilation to allow evaporation to occur without rainfall entering the system
  • prepare the biomix as detailed for a non-evaporation system, but with a 50:50 ratio of soil and straw, and without turfing over it
  • base the treatment volumes on evaporation calculations
  • get advice on design and volume calculations from specialists with experience in these systems

Offset biobeds

  • collect pesticide washings from an existing pesticide loading and washdown area in a storage tank
  • pump them for treatment in the offset biobed

Drive-over biobeds

  • construct a bunded drive-over grid above the biobed, with supporting foundations
  • make sure the grid and its foundations are suitable for the loading of any equipment driven over the grid

Do not treat more than 15,000 litres of pesticide washings (excluding rainfall) in any 12 month period.

Keeping records

Agreement holders will need to keep the following records and supply them on re request:

  • any consents or permissions connected with the work
  • receipted invoices, or bank statements where a receipted invoice is unavailable
  • please see the record keeping and inspection requirements as set out in the Mid Tier manual for more detail

Agreement holders will need to keep the following records and supply them with the claim:

  • photographs of the site during the different stages of construction or contracts, invoices or other documents confirming the technical specification for the completed works
  • photographs of the completed works in place and installed

Before applying, applicants must seek advice from the EA and obtain any consent that may be required to carry out the planned work. Applicants must check whether they are in a Groundwater Source Protection Zone 1 area.

Applicants will have to send the following with their application:

This item can be used on the same area as RP28 - Roofing (sprayer washdown area, manure storage area, livestock gathering area, slurry stores, silage stores).

Advice and suggestions for how to carry out this item

The following section gives advice on carrying out this item successfully but does not form part of the requirements for this item.

How to get further design advice

Further design advice is available on how to size the loading and washdown area and holding tanks, and on pesticide washing volume calculations, from Catchment Sensitive Farming and in the Biobed Manual on the Voluntary Initiative website. Payment rate is £118 per square metre of the bunded area.

How to choose a location

The biobed should be constructed in an area set aside for pesticide loading and washing operations, and where there is no other traffic.

It can be constructed on the same area as the following features, even though they are ineligible for the Basic Payment Scheme:

  • farmyards
  • areas of land, or farm buildings, not used for production

How to maintain the biobed

Add fresh, pre-composted biomix to the biobed every year to maintain 1m depth. Replace the biomix every 5 years. A U10 or U11 exemption for spreading waste will be required to spread the biomix to land. Hazardous waste must not be treated in the biobed or biofilter.

What to do with pesticide washings

The pesticide washings from the loading and washdown area collected in the holding tank should be pumped before the tank reaches capacity using a pump float switch. Transfer the washings to the biobed for treatment.

How to main the slab, bund and pumps

Inspect the concrete slab and bund regularly and repair any damage or deterioration. The pumps will also need to be checked regularly to make sure they are operating properly.

Also ensure that:

  • the area is not used for any purpose other than pesticide handling operations
  • the concrete in not damaged so that the area becomes impermeable
  • the storage tank does not overflow

Further information

More information about pesticide handling areas and biobeds, including sizing and volume calculations, is available from the Voluntary Initiative.

Catchment Sensitive Farming (CSF) operates in parts of the country where there are water quality issues linked to farming. CSF provides farmers with free advice and training. See guidance for further information on CSF support

See the Mid Tier manual or Higher Tier manual to find out more about the scheme and how to apply.

Published 2 April 2015
Last updated 10 March 2017 + show all updates
  1. Updated for 2017 applications.
  2. Information updated for applications in 2016
  3. First published.