de686747_inとは___goo_Wikipedia__ウィキペディア___American_English
[0] Combined sewer [British English] Same as American English [Comments] Stormwater mixed with sewage [American English] 
A sewer designed and intended to serve as a sanitary sewer and a storm sewer, or as an industrial sewer and a storm sewer.[1]
Storm drainとは - goo Wikipedia (ウィキペディア)
American English