How to avoid breaking electric wires, telephone wires, and water pipes in the garden while digging

Question

I'm located in France.

For a house (built over 30 years ago) I have to pull new cables through the garden (about 20 m - 30 m). The cable has to avoid certain trees, bushes, obstacles and arrive at a certain point.

Earth is rather hard (clay) and I considered renting a tiny soil trencher.

There are existing electricity cables in conduits, telephone cables in a conduit and water pipes (non metal).

Electricity counter is at the border of the garden. Water counter a few hundred meters away near the public street. The house is accessible via a private street with right of use).

The conduits are over 30 years old and broken and destroyed. The service trying to add a fiber connection to the house tried to use the existing phone line conduit, just to find out, that the probe wire (don't know the correct term) went in 5 meters and came then out in the the garden. So it seems the conduit is no more in a decent state.

I don't have any confidence that the previous owner respected the 'officially' required depths and that he used marker tapes, which should normally be placed a few centimeters above the actual cables / pipes to avoid digging in to them by accident.

I know where each one arrives at the house (so I know the starting point), but I do not know where exactly they are going.

Is there any equipment (to buy / to rent), or are there any specialists who can help locating the existing wires / pipes?

Are metal detectors good enough for thin electricity cables / phone wires? How can I detect water pipes without metal?

Are there other tricks and recommendations of how to avoid breaking the existing 'connections'?

Answer 1

France founded a centralized bureau to manage nation-wide location of public utilities in 2011, so you're in luck. You can find them here : Téléservice "réseaux-et-canalisations"

Vous êtes une collectivité territoriale, un maître d’ouvrage, un maître d'œuvre, un exploitant de réseaux, une entreprise du bâtiment ou de travaux publics, un agriculteur, un particulier… et vous avez des projets de travaux de terrassement, de sondage, de génie agricole…, le téléservice reseaux-et-canalisations.gouv.fr vous permet alors d’identifier gratuitement les exploitants de réseaux concernés par vos travaux et auprès desquels vous devez déclarer vos travaux.

You probably want the section for private individuals : Particulier.

The site above services all types of clients, including contractors, commercial, etc. It would seem that for private individuals you ultimately end up directed here : https://www.declarermonchantier.fr/

Note that this is not an optional step - if you dig and you cause damage you will be liable. The location service is free, so don't try to DIY this.

Attention : L’absence de déclaration fait courir des risques à vous-même, à votre entourage et à l’environnement. En cas de manquement, des sanctions sont prévues.

This service will not locate any private cables, pipes, conduit, etc, that were installed by previous owners, however. These would be connections from your main residence to things like pools, sheds, outdoor lights, or other things that are entirely your property - those would be your responsibility to locate.

The service will locate public utilities, however; electricity, gas, and water lines upstream of their respective meters, telephone and fiber before the demarc, sewer lines, etc, that are the property of the public utility.

Answer 2

In most parts of the world, official utility connections will be marked if you contact a "call before you dig" number that coordinates contacting all the utilities that might have buried service lines under your lawn/garden.

I don't know if France has that, or not.

Those services do NOT mark/locate private utility lines (i.e. if you have a line running from your house to an outbuilding/shed/garage.) They only mark service lines and underground distribution lines if they pass through your property.

There are locator services that can be contracted with (possibly the very same ones hired by the utilities in the above scenario) and there are also tools that can typically be rented through a tool rental store/service.

Standard "metal detectors" do not normally work well, you want a specialist tool for locating wires/cables/pipes.

Answer 3

There do exist instruments for locating buried utilities. Vivax, Radiodetection, Leica, and Greenlee/Textron are names of manufacturers I'm aware of. This equipment operates on the principle of connecting a transmitter to a conductor (a metallic wire or pipe, or a wire buried alongside plastic pipe) and using a receiver to detect the electric fields radiating from that conductor.

I recently noticed one such kit offered for rent at an irrigation supply specialty store -- if ordinary tool rental stores near you don't offer a locator, you might inquire at supply houses for irrigation, plumbing, or electrical contractors.

If you're unable to get a utility operator to mark the lines (perhaps because they're private lines) and unable to perform locating on your own, the next best thing is to make an educated guess about where the buried lines are likely to be. You can then arrange the trenching project to avoid those zones, work shallow in those zones, or hand-dig the trench for a meter or two where you anticipate a crossing. When hand digging, orient the blade of the shovel so that it is parallel to the suspected utility. This minimizes the probability that you'll strike and slice through it, especially for small cables like telephone, TV, or fiber optic.

You know where the buried utilities connect at the house. Do a little more work to figure out where they connect out in the garden, street/alley, or neighboring properties. There will be tell-tale signs: an access vault for a water meter or shutoff valve, a splicing point for electrical or other cables, and so on. One can't be certain that the services to the house run in a straight line across the garden, but such is common.

Answer 4

If the natural ground is very hard, you can try an archaeological approach.

Remove the top soil in a wider strip than you actually need to be able to detect different colours of the ground. If the top soil is deep, then remove it in 5cm layers until you hit the natural clay. Change in colour from the top soil or natural clay indicates that something was dug here before.

To make it easier for the next cable, put yours in a pipe (conduit) with some wire running through it so that you don't have to dig up the garden next time. The next cable than then just be pulled through the pipe by the wires.

Answer 5

I will enhance this answer over time to indicate what helped me and how I solved the issue.

There's multiple good answers each addressing another aspect of my question, so I had difficulties marking one answer as 'the correct' answer.

So far:

How to obtain information about existing cables and tubes for France:

Thanks to J...'s answer I went to www.reseaux-et-canalisations.ineris.fr which ultimately led to following link https://www.declarermonchantier.fr/

I created an account and declared that I want to do works, which resulted in four documents that were sent to four different potentially concerned authorities.

Will now see when and how I receive the information about the official pipes and cables, that are in my garden.

Within the hour I already got a first answer of one authority stating, that none of their cables is 50m near my garden.

Having reread J...'s answer

The service will locate public utilities, however; electricity, gas, and water lines upstream of their respective meters, telephone and fiber before the demarc, sewer lines, etc, that are the property of the public utility.

I'm not sure that the feedback will help in my particular case as the electric counter is at the border of the garden and the water counter even a few hundred meters down the street away from the garden.

For others who have the counters in their house, this will however be very useful.

2021-07-13: Enedis seems to provide information of their wires up to the electricity counter Just got feedback from Enedis concerning electricity. Information goes up to the counter. In my case I'm out of luck as the counter is at the border of the garden.