The usual answer is.. "as little as they can get away with"
🙂Sometimes if the occupiers are not there they will just trail it around on the surface. Usually they will lay it an inch or two under soil at the border of the "lawn".
I would advise you or the neighbour to be in attendance and ensure that its done to your/their satisfaction. But some flexibility may be needed to ensure the job does get done
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John
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I do not work for VM. My services: HD TV on VIP (+ Sky Sports & Movies & BT sport), x3 V6 boxes (1 wired 2 WiFi,) SH2 in modem mode with Airport Extreme Router +2 Airport Express's. On VIVID200, Talk Anytime Phone, x2 Mobile SIM only iPhones.