open sewer manhole

aid alarm alert assistance attention background beware canalisation care careful caution city conduit construction cover danger dangerous detail drain drainage emergency floor footpath grate ground hole holes industry iron manhole material metal open outdoor path pattern pave paved pavement paving plate prevention protect protection public reminder repair risk road roadsign roadway rough safe safety sanitary secure security sewage sewer sewers shape sidewalk sign signboard site steel street supply surface traditional tube urban utility walkway warning water way work works