When the surface has settled or dipped

What a professional will be trying to work out

These are the distinctions a professional makes when they attend. They are questions, not conclusions — and knowing them lets you follow the conversation rather than just receive its result.

• where the change sits relative to known buried services
• whether it is stable or progressing
• whether any excavation has happened there previously

What is worth writing down

These details are cheap to record now and impossible to reconstruct later.

• the location and approximate size
• dated photographs over time
• any known prior work in that area

Evidence that would change the next decision

If you are deciding whether something is worth paying for, these are the things that actually move the decision.

• dated photographs showing whether it is progressing
• records of prior excavation in that area
• whether the line’s route has been located

What a surface change puts in play

A dip is a reason to have somebody look, and dated photographs are what make a later comparison possible. Whether a buried line is involved at all is not something the surface answers, and ground moves for more than one reason.

If the line does turn out to be involved, work at that spot usually involves opening the ground over it. Putting the surface back afterwards is a stage of the job in its own right, and what a proposal says about restoration is worth reading before any machine arrives.