Solving the Private I/I Quandary with Creative Field Investigations

Sanitary sewer evaluation surveys (SSES) and inflow/infiltration (I/I) investigations are not new. However, many previous studies have fallen significantly short of fully understanding where, why, how, and how much stormwater inflow and infiltration is entering the sanitary sewer system. CDM is currently working on two large-scale I/I studies for the city of Columbus, Ohio. CDM's approach is unique because detailed thorough field investigations are combined with creative engineering analyses and geographic information system (GIS) implementation. Some of the essential field investigations and engineering analyses include:Flow monitoring of sanitary sewersHydrologic/Hydraulic modelingRTK shape analyses of flow monitoring data for each sub-basinPrivate property questionnaires mailed to all residents, and compiled and entered into a databaseDry and wet weather CCTV inspections with PACP comprehensive databaseHouse-to-house, street, and alley inspections/surveys to identify potential I/I sources from area drains, manholes, and foundation drainsDye-testing of private property and public propertyGIS mapping and database compilationAlternative development and cost estimatingThe paper and presentation will detail the most critical and innovative methodologies, such as the use of hand-held GPS data loggers, to complete private property inspections in the study area. These methodologies identify the paths of stormwater and the efficiency of stormwater flows to the storm sewers or sanitary sewers from downspouts, sump pumps, and foundation drains.