Locating electrical conduit under walkway

Question

I am installing a home EVSE charging station. From the circuit breaker box, there are unused conduits that lead to a lamp fixture location near the end of the driveway. I have located the panel end of this conduit, and would like to tap off the conduit halfway to the direction of the EVSE.

1. How to properly splice two conduits under a garden-tile walkway?
2. How to locate the conduit under a garden tile walkway?

The walkway is about 3 meters wide, each tile in the photograph is about 30 cm square and the photo shows half the walkway. As can be seen, I have dug up part of the walkway looking for the conduit. However, I do not know how deep it is. Under the garden tiles I found ~10 cm of soft brown filler material, then below that seems to be some type of gravel-concrete mixture. After digging away at that for an hour I've only penetrated maybe 5 cm or so.

Is there an easier way to locate the unused (empty) conduit?

I tried having my son make noise at the conduit's end, then using a stethoscope against the ground. Alas, I have only a children's stethoscope and no access to medical equipment, and this did not work.

Answer 1

A couple of options:

1. Keep digging. You should eventually find it if it's there. The most labor intensive but people do this every day.

2. Rent a cable locator or hire someone who provides this service. An underground cable locator is a device that can actually detect and locate a buried cable to within a few inches in any direction. The conduit will either need to have a wire in it that can be connected to or the end accessible so that a conductor or sonde (a small RF transmitter) can be threaded into the conduit and then located.

Once you have the location from the locator you can dig there and get to the conduit.

Answer 2

In addition to @jwh20 fine answer, once you find the conduit, if there are wires in it, you'll need to remove the existing wires and cut the conduit and route it into a hand hole along with the other end of the conduit and the new conduit to the EVSE station. Then pull and splice wires. The hand hole will need to be accessible. See picture from Granger below:

If you find an empty conduit like you assume that's in good shape, you can connect it to the new run of conduit and just pull wire from panel to EVSE station. If it will be a long run with bends, you'll probably need the hand hole.

Answer 3

I'm not sure where in the world you are located, but in the US in order to "splice two conduits":

1. The splice must be in a junction box of the appropriate type.
2. The junction box must remain accessible without tools (beyond a screwdriver to remove the JB's water tight cover). AIUI, this means that if you bury the box under the walkway, you have to be able to get to it by simply lifting one of those pavers with your hands - no pry bars allowed, no digging through bedding material, etc.

Instead of destroying the rest of the walkway to get to the conduit & put the splice below there, move away from the walkway and put the splice box in the yard. It may not be quite as pretty, but the box needs to remain exposed, and it'll be a lot easier digging up dirt than it will be digging through the bedding for your walkway then trying to recompact it to keep the walkway stable.

I would imagine that your locale (if not US) would have similar code requirements. Even if it doesn't, not burying the junction box in a very difficult to access location simply makes sense.