Water grants 2015: lined biobed with existing washdown area (RP25)

Eligibility and requirements for lined biobed with existing washdown area.

This guidance was withdrawn on

Capital items for improving water quality are now available through the Mid Tier of Countryside Stewardship.

Farmers and other land managers can apply for water grants.

Read the accompanying guidance to find out more about Countryside Stewardship water grants 2015.

How much will be paid

£77 per square metre.

Where the item is available

This item is available in Catchment Sensitive Farming (CSF) target areas.

When this item can’t be used

It can’t be used

  • within 10m of a watercourse;
  • within 50m of a spring, borehole or well;
  • within 250m of a borehole used for food production; or
  • on historic or archaeological features or areas of wildlife value.

How this item will benefit the environment

This item reduces the risk of water pollution by degrading the pesticide residues that arise from pesticide handling activities.


Applicants must send the following with their application for this item:

If the site is in a Groundwater Source Protection Zone 1 area, applicants must consult the Environment Agency about using this item.

Applicants must send any advice and consent they receive with their application.

With permission from Natural England, advice and consent can be received up until 29 May 2015; applicants can discuss this with their local Catchment Sensitive Farming officer.

On the land

Successful applicants will need to construct a biobed that meets the requirements of the T32 waste exemption. All the capital works must also meet the relevant British Standards -check the most up-to-date standards.

How to construct a biobed

To construct a below-ground biobed, successful applicants must:

  • dig 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; and
  • 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, successful applicants must:

  • use pre-cast or reinforced concrete and a 1.2mm thick liner, or an impermeable pesticide grade container; and
  • 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), a drain must be inserted 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 isn’t 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; and
  • place a ring of perforated drainage pipe into the base of the biobed on top of the liner to assist the pump flow.

Pumps must then be installed to carry the treated discharge from the biobed to a vegetated area for irrigation. Alternatively, pump the treated discharge to a storage tank for irrigation or re-use.

How to prepare the biomix

To prepare the biomix, successful applicants must:

  • 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’s any settlement; and
  • use at least 1 cubic m of biomix for every 1000 litres of liquid treated in any 12 month period.

They must then turf over the biomix (except for evaporation systems) and lay perforated pipes to distribute pesticide washings across the surface. The biobed doesn’t need a cover or roof, unless it’s an evaporation system.

How to use evaporation systems

For biobeds designed to work by evaporation, successful applicants must:

  • cover the biobed with roof sheeting, using side ventilation to allow evaporation to occur without rainfall entering the system;
  • prepare the biomix as advised 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; and
  • get advice on design and volume calculations from specialists with experience in these systems.

For offset biobeds, pesticide washings must be collected from an existing pesticide loading and washdown area in a storage tank. The pesticide washings should then be pumped for treatment in the offset biobed.

For drive over biobeds, successful applicants must construct a bunded drive over grid above the biobed, with supporting foundations. They must make sure the grid and its foundations are suitable for the loading of any equipment driven over the grid.

Keeping records

Successful applicants will need to keep:

  • dated photographs taken before, during and after the construction of the biobed (submit these with any claim and show them on request);
  • the documents relating to waste exemption T32 (sent with the application);
  • any consents received in connection with the work (show these on request); and
  • receipted invoices and bank statements relating to this work

What must not be done

Don’t treat more than 15,000 litres of pesticide washings (excluding rainfall) in any 12-month period.

How to carry out this item

The following section gives advice on carrying out this item successfully.

How to choose a location

Successful applicants should construct the biobed in an area set aside for pesticide loading and washing operations, and where there is no other traffic.

The biobed can be constructed on the same area as the following features, even though they’re ineligible for the Basic Payment Scheme:

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

How to maintain the biobed

A fresh, pre-composted biomix should be added to the biobed every year to maintain 1m depth. Replace the biomix every 5 years. Waste exemption U10 will be needed to spread the biomix. Hazardous waste should not be treated in the biobed or biofilter.

Further information

See the Voluntary Initiative website for further information about pesticide handling areas and biobeds, including sizing and volume calculations.

Published 2 March 2015