Planning permission for a slurry store or lagoon

Slurry store planning has two halves that farmers regularly confuse. Planning controls whether the structure can be built and what it looks like. The silage, slurry and agricultural fuel oil regulations control how it is built, how big it has to be and who must be told before it is used. A store can be permitted development for planning purposes and still be unlawful to fill, because the notice to the Environment Agency was never given.

Agricultural permitted development for waste storage

Class A of Part 6 of Schedule 2 to the General Permitted Development Order 2015 covers development on agricultural units of five hectares or more that is reasonably necessary for agriculture on that unit. That includes buildings, and it includes excavations and engineering operations, so an above-ground store and an earth-banked lagoon can both fall within the right.

The limits apply as they do to any Part 6 building. A building must not exceed 1,000 square metres of ground area, aggregated with other development under the class within 90 metres in the preceding two years. Height is capped at 12 metres, reduced to three metres within three kilometres of an aerodrome. Nothing may sit within 25 metres of the metalled portion of a trunk or classified road.

The restriction that matters most here is the protected building rule. A building for accommodating livestock, or a structure for storing slurry or sewage sludge, is not permitted development within 400 metres of the curtilage of a protected building. That distance rules out a great many convenient locations next to the existing yard.

Where the right applies, the prior notification procedure follows: apply for a determination as to whether prior approval is required for siting, design and external appearance, and the council has 28 days from receipt to respond.

Where the right stops and permission is needed

A full planning application is required where the holding is under five hectares, where any limit is exceeded, where the 400 metre rule bites, or where the store serves something other than agriculture on that unit.

That last point catches anaerobic digestion and imported waste. A store taking digestate or slurry brought in from other holdings is not serving agriculture on the unit in the ordinary way, and councils treat it as a waste management use requiring permission, often from the county council as waste planning authority rather than the district.

Where a full application is needed, a short Planning Statement covering herd numbers, the regulatory storage requirement, the siting options considered and the landscape response does most of the work. Set out the functional need with figures. A store sized to a regulatory minimum is easier to defend than one described as future-proofing.

The storage regulations

The silage, slurry and agricultural fuel oil regulations set construction standards and require notice to the Environment Agency before a new, substantially enlarged or reconstructed store is brought into use. The notice period is short but it is mandatory, and the regulations also set out design life and construction requirements referenced to the relevant British Standard for agricultural buildings.

Minimum storage capacity is set by reference to the period of production the store must hold, and longer periods apply in nitrate vulnerable zones. Those figures change, so check the current requirements on gov.uk rather than working from a neighbour's store built a decade ago. Undersized storage is the single most common reason a farm ends up spreading at the wrong time of year and attracting enforcement from a different regulator entirely.

Separation from watercourses is also prescribed, and the regulations set a minimum distance between stores and inland or coastal waters. Check that distance against your site before the design is fixed, because moving a lagoon 15 metres is easy on paper and expensive once the excavation has started.

Odour and separation from dwellings

There is no national separation distance between slurry storage and dwellings, which means the assessment is done case by case and neighbours object to almost every application.

Deal with it properly. Identify the nearest dwellings in other ownership with measured distances, describe the prevailing wind direction from local climate data, and set out the mitigation: a cover or crust management regime, filling arrangements that reduce agitation, and the timing of emptying. Where dwellings are close or the scheme is large, an Odour Assessment prepared by someone with the relevant experience is money well spent, and councils usually expect a suitably qualified author.

Covers do more than reduce odour. They cut rainwater ingress, which reduces the volume to be spread, and they reduce ammonia losses, which is increasingly a policy point in its own right.

Groundwater protection and lining

Earth-banked lagoons rely on the liner and the base. Where the site sits over a principal aquifer or within a source protection zone, the Environment Agency will want to see the design, the permeability of the liner, the leak detection arrangements and the groundwater monitoring proposed.

Check the source protection zone mapping and the groundwater position statements before choosing a location. A site inside an inner zone will attract an objection that is very hard to answer, and the alternative location half a kilometre away may be entirely acceptable.

Ground conditions matter for stability as well as containment. On sloping ground, on made ground or over old mine workings, a geotechnical appraisal of the bank design is worth having before the application rather than after a condition requires it.

Landscape effects of a large structure

A modern above-ground store is a tall cylinder in a flat field, and it will be visible. Site it against existing buildings, use a recessive colour, and show the structure on a photomontage from the nearest public road or footpath.

In a National Landscape or a National Park, expect a closer look and consider a Landscape and Visual Impact Assessment prepared to the recognised guidelines with viewpoints agreed in advance. Elsewhere a proportionate landscape appraisal with annotated photographs is usually enough.

Planting rarely screens a 6 metre tank quickly, so do not rely on it as the whole answer. Siting does more than mitigation.

Grant funding and the submission

Government grant schemes for slurry infrastructure have their own capacity, design and cover requirements, and those requirements can exceed the regulatory minimum. Check the current scheme rules before finalising the design, because a store built to the regulatory minimum may not qualify for funding and enlarging it later means going back through both regimes.

Illustrative example: a dairy unit needing additional storage, with the obvious yard-side location 340 metres from a neighbouring cottage. The protected building rule removes permitted development, so the farm applies in full for a covered above-ground store 120 metres further from the cottage, behind the existing shed range. The application includes herd figures, the regulatory capacity calculation, a cover specification and a photomontage from the lane. Granted, with conditions on colour and on the cover being installed before first use.

Allow six months from first sketch to a usable store. Planning or prior notification, the regulatory notice, the ground investigation and the build each take their own time, and the regulator deadlines do not move because the herd has grown.

This is general guidance, not legal advice. Check the position with your local planning authority, the Environment Agency or a qualified professional before relying on it.

PlanScope provides AI-assisted draft reports for planning applications. Reports should be reviewed before submission. We do not guarantee planning approval. Enter the farm postcode on PlanScope to see which documents a slurry storage proposal is likely to need.