Major accident hazard pipelines and consultation distances

A hazardous pipeline consultation distance is the zone around a major accident hazard pipeline within which a local planning authority must consult the Health and Safety Executive before deciding an application. The Executive then advises for or against, by reference to the sensitivity of the proposed development and its distance from the pipeline. Its advice is not binding, and in practice authorities follow it almost without exception.

Developers find out about these pipelines late, usually when the consultation response arrives three weeks before committee. By then the layout is fixed and the affected part of the site is the part with the housing on it.

Which pipelines carry a planning consultation distance

High pressure pipelines carrying hazardous substances, principally natural gas and some liquid fuels and chemicals, are notified under the Pipelines Safety Regulations 1996 where they meet the criteria for a major accident hazard pipeline. For those, the Executive establishes consultation distances and local planning authorities are expected to consult it on development within them.

The distances are typically divided into zones: an inner zone closest to the pipeline where the Executive advises against most development, a middle zone, and an outer zone where only the most sensitive uses attract an objection. The width of each zone depends on the pipeline's diameter, pressure, wall thickness, depth and contents, so two pipelines of the same diameter can have very different distances.

Separately, the same framework applies to fixed installations handling hazardous substances, with consultation distances around them, and to sites subject to the major accident hazard regime. Pipelines and installations are dealt with under the same planning consultation arrangements but they are different things, and a response about one does not tell you about the other.

Finding the pipeline and its corridor

Pipeline routes are not published on a single open map, partly for security reasons, so finding them takes several steps.

Work through these in order:

1. Ask the local planning authority, which holds the consultation distance mapping it uses to decide when to consult.
2. Check the development plan's policies map and any safeguarding or hazard constraint layer.
3. Commission a utility and asset search covering the site and a margin beyond it.
4. Inspect the site for marker posts, aerial markers, stiles over a cleared strip and an unexplained absence of hedgerow trees along a line.
5. Contact the operator identified by the search for its asset plan and its requirements.
6. Walk the line of any easement shown on the title.

Marker posts are the giveaway. A line of yellow posts across a field, or a mown strip that no farmer would choose, means a pipeline. The absence of markers does not mean the absence of a pipeline, since markers are not continuous.

Title documents matter here too. An easement in favour of a pipeline operator will usually appear on the register with a plan, and the registered extent is the starting point for what you can and cannot do.

How the Health and Safety Executive advises

The Executive assesses the proposal against the sensitivity of the development and the zone it falls in. Sensitivity depends on the number of people, their vulnerability and the difficulty of evacuating them, so a warehouse and a care home in the same position attract very different advice.

The practical pattern is that housing densities, schools, care homes, hospitals and large places of assembly attract objections closer to the pipeline than industrial or storage uses do. A proposal that puts open space, parking or a commercial unit in the inner zone and the dwellings beyond the outer zone can often be supported.

Where the Executive advises against and the authority is nevertheless minded to grant permission, there is a procedure requiring the authority to notify it before issuing the decision, which gives the Executive the opportunity to comment further. Check the current arrangements in the development management procedure rules, since they have been amended over time.

Treat that as the shape of the system rather than as a rule. The Executive's own assessment for your pipeline is the only answer that counts, and it is worth obtaining before the layout is drawn.

Building, excavating and planting near a pipeline

The operator's requirements run alongside the planning position and are often stricter. Typical restrictions within the easement strip cover building, deep excavation, heavy plant movements, changes in ground cover, the planting of trees and deep-rooting shrubs, and any works that would affect access for inspection.

Crossing the pipeline with a road, a drainage run or a service requires the operator's written agreement and usually a method statement, with constraints on cover depth, loading, trench proximity and plant type. Construction traffic crossing the line needs assessment, and the usual answer is a designated crossing point with protective slabbing.

Cover these points in the Construction Management Plan: the crossing points, the plant restrictions, the exclusion zone, the operator's notification requirements, and who holds the method statement on site. Where ground conditions affect loading on the pipeline, the Geotechnical Assessment should refer to it rather than treating it as someone else's problem.

Landscape proposals need checking against the operator's restrictions before they are submitted. A landscape plan with an avenue of lime trees along the easement strip will be refused by the operator after it has been approved by the council, which is an awkward position to be in.

Easement rights and the operator agreement

The easement is a property right, independent of planning. It typically grants the operator rights to lay, inspect, maintain and replace the pipeline, with covenants restricting what the landowner may do.

Two consequences follow. Planning permission does not override the easement, so a consent for a building on the strip is worthless without the operator's agreement. And the operator's consent is a commercial negotiation with no statutory timetable, which makes it a programme risk rather than a procedural step.

Read the deed rather than relying on the register's summary. The width of the strip, the activities restricted and the consent mechanism are all in the document, and they vary between operators and between decades.

Diversion as an option and its cost

Diversion is technically possible and expensive. For a high pressure gas pipeline it involves design, land assembly for the new route, new easements, construction, commissioning and decommissioning of the old section, with the whole programme measured in years rather than months.

The decision is usually straightforward once the figures exist. On a site where the pipeline crosses the middle of the developable area and the density needed to make the scheme viable cannot be achieved around it, diversion may be the only route. On most sites, designing around the corridor costs an order of magnitude less.

Get an indicative figure from the operator early. The number tends to settle the argument quickly.

Evidence to submit

For an application within a consultation distance, the file should contain a plan showing the pipeline, the easement strip and the consultation zones against the proposed layout, the operator's correspondence, and a short statement of the measures taken.

The Planning Statement should address the constraint openly rather than leaving it to the consultation response. Officers respond better to a layout that has demonstrably been designed around the pipeline, with the sensitive uses placed furthest from it, than to one where the pipeline appears for the first time in the Executive's objection.

Where a constraint has shaped the layout in a way that reduces unit numbers, record that too. It is relevant to density policy, and it is relevant to viability. The same logic applies to other buried constraints, as source protection zones and development over groundwater illustrates for a different hazard.

This is general guidance, not legal advice. Consultation distances, zone boundaries and the procedure for notifying the Executive are set and revised by the regulator, so check the current position with your local planning authority, the pipeline operator and 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.