Checking SSSI impact risk zones before you apply

A site of special scientific interest impact risk zone is not a designation on your land. It is a consultation trigger: a mapped area around a protected site, tagged with the kinds of development that Natural England wants to be told about. If your site falls inside a zone and your proposal matches one of the tags, the local planning authority has to consult Natural England before deciding, and that consultation adds time and, often, a request for survey work.

Checking it takes about five minutes on the public mapping service, and doing it before you design the scheme is worth far more than doing it after the officer raises it.

What the zones are for

Public bodies have a statutory duty to consult Natural England before permitting operations likely to damage the special features of a site of special scientific interest. That duty sits in the wildlife and countryside legislation, and it applies whether or not the development is on the designated land itself.

The zones were created to make that duty workable. Rather than asking every authority to judge which applications might affect a protected site, Natural England mapped buffer areas around each one and tagged them with development categories. An authority checks the map, matches the proposal against the tags, and consults where there is a match.

Two consequences follow. A zone is not a constraint on development in its own right, and being inside one does not imply refusal. But an application inside a zone that has not anticipated the consultation will sit while it happens.

How the development type tags work

Each zone carries a list of development categories, and the categories are specific about scale and type. They cover things like residential development above stated unit thresholds, rural residential development, any discharge of water or liquid waste, infrastructure, combustion and air pollution sources, livestock and composting, minerals and oil and gas, and rural non-residential development.

The tags differ between zones, because they reflect what the underlying protected site is sensitive to. A zone around a wetland will flag water discharge and abstraction. A zone around a site sensitive to nitrogen deposition will flag combustion and livestock. A zone around a site vulnerable to recreational pressure will flag residential development at a lower unit threshold than elsewhere.

Read the tags for your specific zone rather than assuming a general rule. The single most common mistake is treating the presence of a zone as the answer, when the answer is whether your development type appears in that zone's list.

Finding your site and reading the trigger

The dataset is published through the government's public mapping service for the natural environment, and is also available through the planning data platform for anyone working with the underlying files.

1. Open the mapping service and search for your postcode or grid reference.
2. Turn on the impact risk zone layer, which sits under the statutory land-based designations.
3. Zoom to the site boundary and confirm whether any part of it falls within a zone, including access arrangements and any off-site works.
4. Click within the zone to open its attributes and read the full list of development categories.
5. Record the zone name, the protected site it relates to, and the exact wording of the categories that match your proposal.
6. Screenshot the map extract with the site boundary visible and date it.

That last step is the one that saves time later. A dated map extract in the application pack answers the question before it is asked. Building a site constraints plan from open data covers how to pull this layer alongside the others onto a single drawing.

What the consultation involves

Where a trigger is matched, the authority sends the application to Natural England, which has a period in which to respond as a statutory consultee.

The responses fall into a few patterns. No objection, sometimes with standing advice attached. No objection subject to conditions, typically securing mitigation or a management regime. A request for further information, most often a survey or an assessment of a specific pathway such as water quality or recreational pressure. Or an objection, which is rare and usually reflects a direct effect on the protected features.

Standing advice is worth reading early. Where Natural England has published standing advice covering your situation, the authority may rely on it without a bespoke response, which is quicker.

Budget for the consultation period in the programme rather than hoping it runs in parallel with everything else. On a minor application with an eight-week determination period, a consultation that produces a request for survey work in week four effectively ends any prospect of a decision in time.

Preparing for the likely question

Work backwards from the tag that matched.

If the trigger is residential development, the question is usually recreational pressure on the protected site, and the answer may involve a contribution to visitor management or the provision of alternative open space. If the trigger is water discharge, the question is where foul and surface water go and what that does to water quality, which pulls in a Drainage Strategy and possibly a Foul Sewage Assessment. If the trigger is air quality or combustion, the question is nitrogen deposition, and it needs modelling rather than assertion.

A Preliminary Ecological Appraisal is the usual starting point where the trigger relates to habitats or species, and it should refer to the zone explicitly rather than treating it as background.

Where the zone covers a large area

Some zones are very large, particularly around sites sensitive to air pollution or recreational disturbance, and it is common for an entire town to sit inside one. That does not make the zone meaningless, but it does change how you should read it.

In a large zone, the tags usually set higher thresholds, so a single dwelling may not trigger consultation where a scheme of fifty would. Check the threshold in the attributes rather than assuming.

Where the zone relates to a European site as well as a national one, a separate and more demanding assessment regime may apply under the habitats legislation, and the questions of nutrient or water neutrality may arise. That is a different exercise from the impact risk zone check and it cannot be answered from the same map.

Recording the check in your submission

Put it in the planning statement, briefly and specifically: the zone name, the protected site, whether the proposal matches a tagged category, and what has been done about it.

Where there is no match, say so and show the map extract. Where there is, say which category matched and cross-reference the report that deals with it. Authorities appreciate the check being done for them, and it removes an easy reason to delay validation or to issue a holding response. Keeping that extract current matters on long projects, as keeping constraint data current over a long project explains.

One honest caveat. The zones are a screening tool maintained centrally, and they are updated from time to time. A check done two years ago is not a check, and neither is a constraints report bought at the outset of a scheme that has since changed in scale.

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