Water grants 2015: lined biobed plus pesticide loading and washdown area (RP24)

Eligibility and requirements for the lined biobed plus pesticide loading and washdown area.

This guidance was withdrawn on

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

Applies to England

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

£118 per square metre.

Where this item is available

  • This item is available in Catchment Sensitive Farming (CSF) target areas.
  • Applicants must have the support of a CSF officer to use it.

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; and
  • on historic or archaeological features.

How it benefits the environment

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


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 contact the Environment Agency to discuss using this item.

Applicants must send any advice or consent they receive from them with their application for this item. 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

All the capital works must meet the relevant British Standards - check the most up-to-date standards.

Successful applicants will need to install a concrete bunded loading area, holding tanks, and fixed pumps and pipes to remove washings from the tank. To do this, they must:

  • remove topsoil and dig an area for the washdown area and tank;
  • remove or divert any field drains that cross the site;
  • cover the site with 140 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’s 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) where you can pump and dispose of pesticide washings;
  • make sure the holding tank is made from seamless polyethylene, glass-reinforced plastic (GRP) or pre-cast concrete;
  • make sure the tank is sized according to local rainfall and the area of concrete (if there’s no roof or cover); and
  • make sure the whole structure is impermeable.

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 (send these with any claim and show them on request);
  • the documents relating to waste exemption T32 (sent with your application);
  • any permits or 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


  • treat more than 15,000 litres of pesticide washings (excluding rainfall) in any 12 month period;
  • treat hazardous waste in the biobed or biofilter;
  • use the area for any other purpose than pesticide handling operations;
  • allow the concrete to be damaged so that the area is impermeable; or
  • allow the storage tank to overflow.

How to carry out this option

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

How to get further design advice

Further advice is available from CSF on how to size the loading and washdown area and holding tanks, and on pesticide washing volume calculations.

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’s no other traffic. This item can be used on a part of a parcel.

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

  • farmyards; or
  • 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. A Waste exemption U10 will be needed to spread the biomix.

What to do with pesticide washings

The pesticide washings collected in the holding tank should be pumped before the tank reaches capacity. Use a pump float switch to dispose of the washings (a T32 exemption will be needed for this) or to transfer them to a biobed or biofilter for treatment.

How to maintain the slab, bund and pumps

The concrete slab and bund should be checked regularly. They should be repaired if they’re damaged or if they’ve deteriorated. The pumps should also be checked to make sure they’re operating properly.

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

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