Strangers - John Simm (2018) - Stanley Sewage Treatment Works, Stanley

David and Jonah head to the refuse depot from where the truck that killed their wife originated. In the show it quite obviously says "Shatin Refuse Depot" on the various images they are examining but in reality the place they visit (replete with "Shatin Refuse Depot" signs) is in fact the subterranean Stanley Sewage Treatment Works. It appears to have been quite a ground breaking bit of engineering (when HK was capable of doing that stuff) to move the treatment pools and associated heavy plant to this cavern system with an aim to creating a nicer environment for Stanley village dwellers.

The green board/display thing on the left in that last photo helped me find this place because I could just make out the "Drainage Services Dept" emblem at the top left of it. The actual entrance to this place is on Wong Ma Kok Road near to the prison.