HSE HSG47 (3rd edition, 2014) is guidance. It is not compulsory and it does not bind a contractor on its own. What binds the job is the asset owner's own plant-protection specification, the document that document that HSG47 itself points back to when it discusses excavation near a live service. Two jobs on the same street, one over a gas main and one over a water main, can sit under two different documents with two different requirements, even though both operators cite the same HSE guidance somewhere in their own text.

Why the wording differs by network

Each asset owner, whether a gas distribution network, an electricity distribution network operator (DNO) or a water company, writes its own plant-protection specification and sets its own clause numbers, its own tolerances and its own list of permitted techniques. One network's specification may name vacuum excavation as the only acceptable method within a stated distance of the asset. Another may allow hand tools as an alternative. The clause wording is what a contractor can be held to.

What this means for a scope of works

Citing HSG47 alone in a scope of works leaves a gap: it tells a contractor what HSE recommends. The clause that actually governs the dig sits in the network's own specification, and it needs to be identified and quoted before the scope is written.

• Check which network owns the asset before selecting a technique.
• Locate that network's current plant-protection specification.
• Read the clause covering excavation method.
• Treat HSG47 as background reading on method, and the asset owner's specification as the requirement to meet.

For the reasoning behind HSG47's own wording, see What HSG47 Actually Says. Once the governing clause is identified, it can be carried into the tender document; see Specifying It in a Scope of Works for how that wording is normally set out.

Each gas distribution network publishes its own plant-protection specification, and the clause governing excavation near a gas asset is worded differently by each one. Cadent's CAD/SP/SSW/22 (February 2023), section 6.2.1, states: "No mechanical excavation is permitted within 500mm of a gas asset." SGN, NGN and WWU set out the same kind of requirement in their own documents, under their own section numbers, in their own wording.

A clause written for one network does not carry across to another. If Cadent's specification governs the asset in question, the SGN, NGN or WWU clause is not the one to quote in a scope of works, even where the distance and the technique required happen to match.

What to check before quoting a clause

• Which network owns the gas asset at this location
• The reference number and edition date of that network's current plant-protection specification
• Whether the clause has been reissued since the version held on file

Where the clause is not to hand, the wording set out for specifying it in a scope of works shows how to reference it once identified, and what HSG47 actually says covers how the HSE guidance relates to whichever asset owner clause applies.

An electricity distribution network operator (DNO) sets its own excavation clearances in its plant-protection specification, and that document decides whether a dig near a live cable needs vacuum excavation, hand-dug trial holes, or both. The clearance distance, the permitted tool and the trial-hole spacing all vary by network, and by voltage within a network.

What to check per network

Each DNO publishes its own specification number and its own wording for excavation near cables. The clearance stated for a low-voltage service cable is not the clearance stated for a high-voltage feeder, and a specification written for one network's territory does not apply on another's. Before pricing or scheduling the dig, identify which DNO owns the ground, then pull that operator's current specification.

What the clause usually covers

• The minimum clearance from a cable before mechanical plant is excluded
• Whether hand tools alone are permitted inside that clearance, or whether vacuum excavation is named as an accepted method
• Trial-hole spacing and depth where the cable route is uncertain
• Any additional requirement where cables run in ducts or joint bays

Where a specification names vacuum excavation explicitly as the method inside the clearance zone, that instruction sits above general guidance such as HSE's HSG47, which recommends but does not compel a technique. Read what HSG47 actually says to see how the two relate on this point.

A specification clause on its own does not tell you which excavation technique will actually clear a given cable route without damaging it. Read suction, air and water, which suits this ground once you have the governing clearance, and paste the confirmed clause into your tender using the wording set out in specifying it in a scope of works.

A water company's plant-protection specification is the document that governs excavation near a water main or service, in the same way a gas network's specification governs excavation near a gas asset. Each water company publishes its own, and the clause wording differs between them, so the reference number matters as much as the requirement itself when you take it to a contractor.

What the clause typically sets out

Where a water company specification addresses excavation method, it usually states a minimum distance from the main or service within which mechanical excavation is not permitted, and names the excavation technique required inside that zone. That wording sits alongside, and can be stricter than, the general recommendations in HSG47. HSG47 is guidance; the asset owner's specification is what binds the job.

Why the reference number matters

A clause quoted without its document name, reference number and edition date cannot be checked, and a contractor can reasonably query it. Citing the specification by its full reference lets you paste the requirement into a scope of works and hold the contractor to the wording that actually applies to that network's assets.

Once you know which water company's specification governs the dig, you can check the technique it requires against ground and asset conditions on Suction, air and water — which suits this ground, and carry the clause wording forward into Specifying it in a scope of works.

A dig near a gas main, an electricity cable or a water main sits under two kinds of document at once: guidance published by the Health and Safety Executive, and a specification published by the company that owns the asset. They do not carry the same weight, and knowing which one binds the job on the day is what the table below is for.

HSG47 is guidance, not a rule

HSG47 is HSE guidance, not a statutory instrument, and it does not set itself up as one. A contractor can depart from it and still meet the law, provided the departure is justified on the day. Where HSG47 does and does not set a method is covered on What HSG47 Actually Says.

The specification that actually binds the job

The document that fixes the excavation method for a given asset is the plant-protection specification published by the network that owns it: a gas distribution network, an electricity distribution network operator, or a water company. Each writes its own clause, in its own wording, and each can require more than HSG47 recommends. Where the two differ, the asset owner's specification is the one a contractor has to meet.

Reading the table

The table below sets each network's clause against its reference number and the technique it requires, so the wording can be checked against the original rather than taken on trust. A clause changes when the asset owner issues a new edition of its specification, and the wording here should be checked against that current edition before it goes into a scope of works. For the paste-in wording itself, see Specifying It in a Scope of Works.