Utility diversions and the cost nobody budgets

Utility diversion cost is the line most often missing from a development appraisal, and the reason is simple: nobody knows it exists until the topographical survey is overlaid with the asset records. A high voltage cable across the middle of a site, a water main under the proposed access, a gas main along the frontage where the footway is to be widened. Each one is a six figure possibility on a medium sized scheme and a programme item measured in months rather than weeks.

The cost itself is often unavoidable. The programme damage usually is avoidable, and that is where the money actually goes.

Identifying apparatus before the layout is fixed

Start with record enquiries to every undertaker that could plausibly have apparatus in the area: the electricity distribution network operator, the gas transporter, the water and sewerage undertaker, the telecommunications operators, cable operators, and on some sites high pressure gas or fuel pipeline operators, transmission network owners and the Ministry of Defence.

Records are indicative rather than accurate. They show that something is there, roughly, and they are frequently wrong about depth and alignment. So the second step is a physical utility survey, carried out to the recognised specification for underground utility detection and verification, which works through desk study, site reconnaissance, geophysical detection and then verification by trial hole. Each level costs more and tells you more, and the decision about how far to go should be driven by what the layout depends on.

Do this before the layout is fixed. A diversion avoided by moving a building five metres is the least expensive diversion there is.

Two habits pay for themselves. Get the asset records plotted onto the survey drawing by the surveyor rather than kept as PDFs in a folder, so that everyone designs against the same information. And walk the site looking for the evidence above ground: marker posts, valve covers, stop taps, inspection chambers, poles, stay wires and the line of a recent reinstatement across a road.

Who bears the cost of a diversion

The general position is that whoever requires the diversion for their own purposes pays for it. A developer moving a cable to build a house pays the full cost of moving that cable, including design, supervision and any temporary supply arrangements.

Where a highway authority carrying out highway improvement works requires apparatus to be diverted, regulations made under the New Roads and Street Works Act 1991 share the cost between the authority and the undertaker, with an allowance recognising the betterment the undertaker gets from new apparatus replacing old. That sharing does not help a developer directly, but it matters where your scheme includes highway works delivered through an agreement with the authority, because the cost allocation can differ from a straight developer funded diversion. The note on how section 278 highway works costs are built up covers how those packages are assembled.

Where apparatus sits in private land under an easement, the position turns on the terms of the easement rather than on street works legislation. A deed granting the undertaker rights in perpetuity, with a covenant preventing building over, means the diversion is negotiated rather than required.

Quotations, their validity and their exclusions

Undertakers usually work in two stages: a budget estimate, which is indicative and unpriced in detail, and a formal quotation, which is firm for a limited period. The validity period is short, often a matter of weeks or a few months, and it lapses quietly.

Read what the quotation excludes. Common exclusions are reinstatement to the highway authority's specification, traffic management beyond a basic arrangement, works outside normal hours, third party land costs, legal fees for new easements, protection or diversion of other undertakers' apparatus encountered during the works, and any outage or switching costs where the network has to be reconfigured.

Ask three questions on every quotation. What is the assumed alignment, because a change of route after acceptance is a new quotation. What programme does it assume, including any seasonal restriction on working. And what happens to the price if trial holes show the apparatus is not where the records said.

Lead times and the programme effect

This is the cost nobody budgets, because it appears as finance and preliminaries rather than as a diversion line.

The sequence for a significant diversion runs: enquiry, budget estimate, design, formal quotation, acceptance and payment, legal work for new easements, programming into the undertaker's own workload, notices under the street works regime, and then the works themselves. On higher voltage electrical apparatus the switching window may only be available at particular times of year, and on a single circuit feeding other customers a temporary supply may be needed first.

Several months is normal. Longer is common. Treat the diversion as an item on the critical path from the day you find the apparatus, not from the day the contractor arrives.

Where the diversion crosses third party land, add the time to negotiate access and rights, because that is entirely outside the undertaker's control and yours.

Easements, wayleaves and building over

The legal position is as important as the physical one, and the two words are not interchangeable. An easement is a permanent right over land, registered against the title. A wayleave is usually a terminable agreement, and overhead electricity lines commonly sit on wayleaves rather than easements.

That distinction drives the strategy. A terminable wayleave can be brought to an end, subject to its notice provisions and to the undertaker's statutory powers to seek a necessary wayleave where the supply must continue. A registered easement has to be released or varied by deed, which means the undertaker's legal team, its own valuation of the right, and time.

Building over retained apparatus is the alternative to moving it. Water and sewerage undertakers operate build over and build near agreements for public sewers, with conditions on foundation design, access and protection, and the drainage design has to reflect them, as set out in a Drainage Strategy. For electricity and gas, build over is generally refused and protection or diversion is the only route.

Check the title for existing easements before you buy. An easement that prohibits building within a corridor across the site is a planning constraint in everything but name, and a restrictive covenant can have the same practical effect.

Abandoned apparatus and its risk

Asset records show what an undertaker believes it owns. They are far less reliable about what it has stopped owning.

Abandoned cables, redundant mains, disused service connections and old lead pipes are common on brownfield sites, and undertakers frequently decline to remove them or to confirm they are dead. The practical consequences are real: a cable that cannot be confirmed as de-energised has to be treated as live, which means hand digging and safe working precautions. An abandoned gas main may still contain gas. Asbestos cement pipework is a controlled waste with its own handling requirements.

Budget for investigation rather than for removal. A trial hole and a written confirmation from the undertaker are much less expensive than a stoppage while somebody establishes what a cable is.

Sequencing it against the layout

The order that keeps the cost down:

1. Record enquiries and a utility survey before the layout is fixed.
2. Plot everything on one drawing, with the easement corridors from the title plan alongside the physical apparatus.
3. Test the layout against the apparatus, and move the buildings before you move the cables.
4. Raise diversion enquiries in parallel with the planning application, not after permission.
5. Reflect the diversion programme in the phasing and in the cash flow, and price temporary supplies where the works split a circuit.
6. Coordinate with any adoption agreement, because diverted apparatus in a road being offered for adoption affects the technical approval and the commuted sum discussion covered in the note on section 38 adoption and the commuted sum negotiation.

A Utilities Assessment submitted with the application should set out the apparatus identified, the capacity position for each service, the diversions proposed and the constraints they impose on phasing. Officers rarely refuse a scheme over utilities. They do impose phasing conditions that assume a diversion is straightforward, and those conditions are much easier to write sensibly if the evidence is in front of them.

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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.