Complete Dictionary of Dreams
by Dr. Mıchael LennoxA sewer is primarily under the surface and also connects with elements of life that are generally thought of as repulsive, so this is a shadow symbol.
If your dream takes place in a sewer, you are exploring the underbelly of your psyche and considering the more disowned parts of yourself. Such a dream may be reflecting a desire to be free of things you prefer not to look at. There is an added meaning to sewers from the notion that through them, you could move from one area to another without being seen, as long as you were willing to navigate the underbelly of your psyche.
The Big Dictionary of Dreams
by Martha ClarkeDreaming of them, therefore, predicts arguments and reprehensible actions by the people around you.
If valuables appear in the sewer it means that someone could get you in trouble by questioning whether something really belongs to you.