According to Dŵr Cymru Welsh Water's filings with OFWAT, there should be a wastewater treatment plant near here, distinct from the main one in Mynytho. I haven't been able to find it from aerial imagery.

This one should be "Mynytho - Coed Y Fron WwTW", with a ref of "768"

Could a local mapper work out where it is and plot the boundary of it?