The wastewater collection system that the Metropolitan Commission owns and maintains conveys raw wastewater from over 17,000 customers throughout St. Mary's County and delivers it to a number of different treatment facilities for proper treatment and disposal. The sanitary sewer system water shed is comprised of 10 Sanitary Sewer District drainage basins. MetCom operates over 200 miles of gravity sanitary lines and 64 wastewater pump stations serving various neighborhoods throughout the county.

​

Within the sanitary sewer system there are over 2400 manholes and approximately 1400 grinder pumps. The gravity mains vary in size from 6 inches to 42 inches; and vary in depth from 3 feet to 30 feet deep. The materials used include vitrified clay pipe, reinforced concrete pipe, transite pipe and polyvinyl chloride (PVC) pipe. The age of some of the sewers within the county date to the World War II era. There are no combined sewers (stormwater and wastewater) in our system, as they were eliminated well over 30 years ago.