RP8: Constructed wetlands for the treatment of pollution

This item is part of Higher Tier Capital Grants 2025. You must read the Higher Tier Capital Grants 2025 guidance to understand the rules and how to apply.

If you’re applying for this item as part of a Countryside Stewardship Higher Tier (CSHT) application, you must read the CSHT applicant’s guide to understand the rules and how to apply.

How much you’ll be paid

50% of actual costs

How this item benefits the environment

It creates and maintains wetland features that treat field run off and other contaminated water generated from agricultural activities. This helps reduce the risk of sediment and other pollutants entering a nearby watercourse.

Where you can use this item

You can only use this item alongside a feasibility study or a Catchment Sensitive Farming water holding structure action plan developed with Natural England either:

• in areas targeted to reduce water pollution from agriculture
• to treat field and farmyard diffuse runoff

Catchment Sensitive Farming provides advice where there are water quality or flood risk issues linked to farming.

You’ll need to get relevant advice or consents from the Environment Agency, lead local flood authority or internal drainage board before you start any work.

You must also contact your local planning authority to check if planning permission is needed.

You cannot use this item:

• to treat slurry, silage liquor, heavily contaminated water or concentrated pesticide spills and washings as defined under the Nitrate Action Plan Regulations, Slurry, Silage and Agricultural Fuel Oil Regulations or by the Health and Safety Executive
• on historic or archaeological features identified in your Historic Environment Farm Environment Record (HEFER)

What you must do to use this item

You must:

• provide 3 written quotations for completion of the work with your application, including associated costings according to the specification in your plan or study
• agree the selected quotation with Natural England
• create, install and complete the works according to the agreed specification and timescale
• follow the advice on maintenance and management agreed with Natural England (after you have carried out the work)

Read the constructed farm wetlands guide produced by the Wildfowl and Wetland Trust for further help carrying out this item.

You must not place spoil on any historic or archaeological feature or wildlife area identified on your FER, HEFER or on MAGIC.

You should discuss and agree requirements that are specific to your site with your adviser.

Evidence you must keep

You must keep and provide with your claim:

• receipted invoices or bank statements where a receipted invoice is not available
• 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 work
• any consents or permissions connected with the work, including from your local planning authority

If you do not need consent or permission from your local planning authority, you must provide evidence to show this. This can be a:

• letter from the authority confirming you do not need permission
• note of a telephone conversation with a local authority representative, with the name, date, and time of the call
• link to online guidance or printout of guidance text which shows you do not need permission

You must also keep and provide on request:

• photographs of the site before works start
• a copy of the feasibility study or a Catchment Sensitive Farming water holding structure action plan developed with Natural England

Read the record keeping and site visit requirements in the Agreement holder’s guide: Capital Grants, Higher Tier capital grants and Protection and Infrastructure grants for more information.

If you’re applying for this item as part of a Countryside Stewardship Higher Tier (CSHT) application, read the record keeping and site visit requirements in the CSHT agreement holder’s guide.

Other items you can use with this item

You can use this item with RP10: Silt filtration dams or seepage barriers

Advice to help you use this item

The following advice may help you to use this item, but you do not have to follow it to get paid. It’s not part of this item’s requirements.

What the specification needs to include

Your plan or study will create a detailed specification that’s specific to your site. A likely design would be a treatment structure built in at least 3 stages.

Stage 1: create an open pond to act as a sediment trap without much wildlife value. The pond should be accessible to farm machinery for routine maintenance.

Stage 2: plant to encourage settlement and remove nutrients.

Stage 3: there’ll be a shallow wetland, heavily vegetated to reduce pollutants in the water such as:

• nitrates or ammonia
• biological oxygen demand (BOD)
• faecal indicator organisms (FIOs)

Throughout each stage:

• restrict livestock access to reduce the risk of eroding or degrading the treatment area
• build on a non-permeable substrate (made up of 20% clay) or line the area so there’s a permanent pool of water for most of the year
• avoid building on sandy, gravelly and excessively wet soil to prevent contact with groundwater before treatment
• build gentle slopes with a gradient of no more than 1 in 4 – the edges should provide good wildlife habitat and act as a safety feature
• make sure the pond edges are undulated with higher and lower points to provide more edge habitat
• make sure outlet pipes are larger than inlet pipes to prevent water backing up along the system
• obtain a waste exemption if excavated material needs removing – this information should be included in the agreed management plan

Managing the outfall

You’ll need to agree an acceptable water quality standard with the Environment Agency before directing any outfall into the local watercourse.