Source : Webster's Revised Unabridged Dictionary (1913)

Sewerage \Sew"er*age\, n.
   1. The construction of a sewer or sewers.

   2. The system of sewers in a city, town, etc.; the general
      drainage of a city or town by means of sewers.

   3. The material collected in, and discharged by, sewers. [In
      this sense {sewage} is preferable and common.]

Source : WordNet®

sewerage
     n 1: waste matter carried away in sewers or drains [syn: {sewage}]
     2: a waste pipe that carries away sewage or surface water [syn:
         {sewer}, {cloaca}]