Slurry store planning: permitted development and odour
Part 6 of the GPDO covers many farm slurry stores, but not within 400 metres of a protected building. The odour, water protection and access evidence a full application needs.
A new slurry store on an agricultural unit of five hectares or more is often permitted development under Part 6 of the General Permitted Development Order 2015. The exemption disappears within 400 metres of a protected building, and slurry store planning then becomes a full application carrying odour, water and traffic evidence. That distance rule catches more farms than owners expect, because a protected building means any permanent building normally occupied by people, so a neighbour's cottage, a village hall or a rented office all count.
Digestate is a separate problem. A lagoon or tank serving an anaerobic digestion plant is rarely a building reasonably necessary for the purposes of agriculture on that unit, so Part 6 does not reach it and permission is needed on its own terms.
When Part 6 covers a store and when it does not
Class A of Part 6 applies to agricultural units of five hectares or more. Class B covers units between 0.4 and five hectares with tighter limits. Both are conditional, and the conditions bite hard on slurry.
The restrictions that matter most for a store are these. Ground area of the new building is capped, height is limited (lower again within three kilometres of an aerodrome), and nothing may be built within 25 metres of the metalled part of a trunk or classified road. Then comes the exclusion that decides most schemes: no building for the accommodation of livestock, and no slurry or sewage sludge tank, within 400 metres of the curtilage of a protected building.
Buildings on the same agricultural unit do not count as protected, and neither does a dwelling occupied by someone employed there. Everything else does.
Where Class A does apply, you still cannot simply build. A prior approval application goes to the council for a determination on siting, design and external appearance, and the authority has 28 days to respond. Councils use that window to ask about colour finishes, screening and access. They cannot use it to refuse the principle.
If you are inside the 400 metre band, plan for a full application supported by a Planning Statement that deals with agricultural need, alternative siting and residential amenity. The need case is the part most owners under-evidence.
Separation distances that decide the site
Three separate distances apply and they come from three different regimes, which is why they are so often confused.
| Distance | Source | What it controls |
|---|---|---|
| 400 m from a protected building | GPDO 2015 Schedule 2 Part 6 | Whether permitted development applies at all |
| 10 m from inland or coastal waters | SSAFO Regulations 2010 | Where a new or enlarged store may be sited |
| 25 m from a trunk or classified road | GPDO 2015 Schedule 2 Part 6 | Position relative to the highway |
None of these is an odour standard. A store 450 metres from the nearest house clears Part 6 and still generates complaints, and the council can still refuse a full application on amenity grounds if the prevailing wind runs straight at a hamlet. Wind direction, topography and the position of the reception court usually matter more than raw metres.
Where a store sits close to a watercourse, the Environment Agency will look at the whole system rather than the tank alone. Yard drainage, dirty water diversion and the route a burst would take are all part of the picture.
What an odour assessment has to show
Councils rarely ask for full dispersion modelling on a single farm store. They do ask for a proportionate assessment when housing lies within a few hundred metres, and the usual approach follows the Institute of Air Quality Management's odour framework: identify the source, judge its odour potential, work out the pathway, then rate the sensitivity of the receptor.
For slurry the source strength depends on what you are storing and how. A covered tank with below-surface filling behaves very differently from an open lagoon stirred before spreading. An Odour Assessment should set out the agitation and emptying regime alongside the tank volume, because the worst hours of the year are the ones the council will be asked about later.
Digestate stores need more care. Whole digestate has a different odour signature from raw slurry, and importing feedstock changes the character of the operation from farming to processing in the eyes of most planning officers.
Sizing the store under the water rules
Storage capacity is a water protection question that lands in the planning file because it dictates how big the structure is.
Inside a Nitrate Vulnerable Zone the Nitrate Pollution Prevention Regulations 2015 set minimum storage periods, and they differ by livestock type. Grant schemes have pushed the working design standard towards six months for most cattle systems. Confirm the current figure with the Environment Agency before you fix a diameter, because a store sized to yesterday's rule is the most expensive kind of mistake.
The SSAFO Regulations 2010 sit alongside that. New, substantially reconstructed or enlarged slurry storage requires at least 14 days' written notice to the Environment Agency before it is used, and the structure must be built to a standard capable of lasting 20 years with maintenance.
And the two regimes do not talk to each other. Planning permission does not discharge the SSAFO notice, and a valid SSAFO notice does not make an unlawful store lawful.
Groundwater, source protection zones and permits
Check the aquifer designation before the layout is fixed. Environment Agency source protection zones around public water abstractions carry the tightest controls, and an inner zone will usually rule out an earth-banked lagoon entirely.
Discharges to ground of dirty water, silage effluent or yard washings need an environmental permit or a registered exemption under the Environmental Permitting Regulations 2016. A planning permission that assumes a discharge which the Environment Agency will not permit is worthless, so run the two enquiries in parallel rather than in sequence.
On sites with a landscape designation or a prominent skyline position, expect a request for a Landscape and Visual Impact Assessment. Steel tanks read as industrial from a distance, and colour, bunding and planting are the standard mitigation.
Tankers, access and mud on the road
Spreading is seasonal and intense. A store that holds six months of output empties in a few weeks, which means tanker movements concentrate into a short window on lanes that may be single track.
Set out the movement profile honestly in the application. Give the peak week rather than the annual average, name the routes, and say where tankers turn. Where the access serves a classified road, the highway authority will want visibility splays measured against recorded speeds rather than the posted limit.
Depositing mud on the highway is an offence under the Highways Act 1980, and councils routinely condition wheel washing or a hardstanding apron at the field gate. Designing that in at the outset costs far less than retrofitting after a complaint.
Conditions you should expect
Permissions for slurry and digestate storage tend to carry a recognisable set of controls:
- Covers or crusting management on open stores, with a specification approved before construction.
- Agitation and emptying restricted to defined hours, and sometimes to defined wind conditions.
- A dirty water and drainage scheme approved before the store is brought into use.
- Colour finish and screen planting, with a replacement clause for the first five years.
- Restriction of imported material, which is the condition that most often limits later diversification into anaerobic digestion.
That last one deserves attention at the drafting stage. A condition worded to permit only slurry produced on the holding will block a future contract to take waste from a neighbouring farm, and varying it later means a fresh application under section 73 of the Town and Country Planning Act 1990.
Where the farm also proposes to bring land into or out of agricultural use, an Agricultural Land Classification survey may be requested to show that the best and most versatile soils are not being sterilised by hardstanding.
Enter your postcode on PlanScope to see which reports a slurry or digestate store on your holding is likely to need before you commission any survey work.
This is general guidance, not legal advice. Check the position with your local planning authority 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.
Frequently asked questions
Do I need planning permission for a slurry store?
Not always. On an agricultural unit of five hectares or more, Part 6 Class A of the GPDO 2015 can cover a store subject to size, height and siting conditions, with a prior approval application for siting, design and external appearance. Permitted development does not apply within 400 metres of the curtilage of a protected building, and a full application is then needed.
What counts as a protected building for the 400 metre rule?
A permanent building normally occupied by people. That includes a neighbour's house, a village hall, a shop or an office. It excludes buildings on the same agricultural unit and dwellings occupied by someone employed in the farming business. A ruin or an open-sided shed is not normally a protected building.
Does a digestate store get the same permitted development rights?
Usually not. Part 6 covers development reasonably necessary for agriculture on that unit. A store serving an anaerobic digestion plant, particularly one taking imported feedstock, is generally treated as processing rather than agriculture, so it needs planning permission in its own right and often an environmental permit as well.
How far must a new slurry store be from a watercourse?
The SSAFO Regulations 2010 require new, substantially reconstructed or enlarged slurry storage to be at least 10 metres from any inland or coastal waters. You must also give the Environment Agency at least 14 days written notice before the store is used, and the structure must be built to last 20 years with maintenance.
Will the council ask for an odour assessment?
It depends on how close housing is and how the store is operated. Where dwellings sit within a few hundred metres, expect a proportionate assessment covering source, pathway and receptor sensitivity, along with the agitation and emptying regime. Full dispersion modelling is unusual for a single farm store but common for anaerobic digestion.
Sources and further reading
This article is general guidance about the planning system in England and, where stated, the rest of the UK. It is not legal or professional advice. Check your local planning authority’s validation requirements and take professional advice for your specific site.