brown
cement
clean
clear
conduit
danger
dark
development
dirt
dirty
drainage
dump
ecology
environment
environmental
flow
flowing
foam
green
ground
hole
industrial
industry
mud
nature
naturel
outfall
outlet
pipe
pipeline
plumbing
polluted
polluter
pollution
public
river
round
sewage
sewer
stream
toxic
tube
waste
water
waterpipe
waterway