Infiltration/Inflow Control - Town of Highland, IN
The Town of Highland and its Sanitary District have a long history of dealing with infiltration and inflow to the sanitary sewer system. During the 1970s and early 1980s, another firm designed a series of projects to separate the old combined sewers into separate storm and sanitary sewers. Those projects resulted in a huge number of sewage backups into basements.
NIES' initial assignment was to stop the backups. The basement flooding problem was addressed with a series of smaller projects which removed excess storm flow from undersized sanitary lines. Underground storage basins were created to store excess flow during pump station outages or during exceptional rainfall events. By this time, complaints due to basement sewer backups had been reduced to a handful per year and the cause was usually traced to roots or some other blockage in the sewer.
The next challenge came when the utility providing sewage treatment raised its rates. Basement backups were under control but the cost for sewage treatment became the issue. NIES in cooperation with the District staff designed a program to address infiltration and inflow on private property in a cost effective manner.
The District realized that approximately 50 percent of the total sewer length was on private property and that while considerable work had been performed on the public portion of the sewer system, no work had been done on the private portion. The current program is ongoing, but cost for sewage treatment by another utility has decreased four years in a row!
Public officials agree that the effort has been a big success. The program is continuing and is expected to result in even greater future savings.