Baltimore Sewer System Evaluation Survey

An Infiltration/Inflow (I/I) Analysis conducted (by others) on the Baltimore Sewage Collection System in the mid 1970s indicated that I/I was possibly excessive in six areas of the system. In the early 1980s, we conducted a Sewer System Evaluation Survey on these 400 miles of sanitary sewer to identify sources of infiltration and inflow that could be eliminated economically. Elimination of these sources would reduce the operating costs of the pumping station and treatment plant; reduce the frequency and magnitude of overflows, thereby improving water quality; and reduce the amount of planned expansion of the treatment plant and conveyance system.

Through a stepped process of flow monitoring, manhole inspections, TV inspection, smoke testing and inspection for illegal sump pump connections, we identified 78 million gallons per day (mgd) of inflow and 25 mgd of infiltration. A rehabilitation program, estimated to able to cost effectively remove 40 mgd of the inflow and 2 mgd of the infiltration, was developed and recommended.