Can anyone tell me what's happened here?

victorys_sweet, Oct 16, 6:13pm
https://trademe.tmcdn.co.nz/photoserver/full/418820624.jpg

Not sure if gardening & DIY is the best place, but I'm scratching my head over this. Came home from work late last night to find someone had used the hose (water everywhere), there are contractors on our street installing fibre so assumed it was them, irritating but not that weird. Then noticed a gully trap grille had been taken off and there was this grey powdery stuff splattered everywhere. I'm sure there has to be some rational explanation for this! Ideas?

ro42, Oct 16, 6:32pm
Looks like cement powder to me - the spatters you get when washing off tools that have been used for concreting. If so, it should wash off pretty easily. But it suggests they have been pouring waste down the trap, and I wouldn't be happy about that if it were me.

aj.2., Oct 16, 6:42pm
Looks the same too me .
Hope OP is not on septic tank ,

comadi, Oct 16, 6:43pm
If the contractors are directional drilling the duct hole for the fibre, the grey stuff could be drilling slurry. A product used to bind and keep the hole open.
Depending on how much they washed down your drain it may or may not have an affect.
I'd be contacting the company and asking some serious questions.

victorys_sweet, Aug 31, 5:04am
Thanks guys! Yes will get in contact with them and ask some questions!