Do you ever think about where your sewage goes when it leaves your house and whether heavy rains affect the sewers? Well if not, you are certainly not alone – the problem is a classic out-of-sight, out-of-mind situation. For a house or a commercial building, the sewer lateral is the private connection to the main sewer in the street. There are tens of millions of private sewer laterals throughout the United States, and many are in a poor state of repair allowing clean rainwater to enter the sewer during heavy rains. This problem may seem negligible, but the extra water can overfill the sewers causing overflows of diluted sewage anywhere in the system where the capacity is inadequate. In addition, the extra volumes also cost more to treat at the sewage treatment plant. Dr. Ray Sterling, a professor at Louisiana Tech and Director of the Trenchless Technology Center (TTC), says, “Because of their [large] number, a major commitment of resources is typically required to inspect and rehabilitate the laterals, but the level of savings from such a program is not easy to predict.”
With funding from Water Environment Research Foundation (WERF), Dr. Sterling and Mrs. Jadranka Simicevic, a research engineer with the TTC, have investigated how to most cost-effectively improve the condition of sewer laterals. This research involved knowing how to identify sources of rainwater flowing into the laterals and how to inspect the condition of the pipes without having to dig them up first. They have reviewed and evaluated the methods available to rehabilitate private laterals and also have provided guidance on how cities have developed programs to assist homeowners with the financing of the repairs including the legal and liability issues of a public program that involves work on private property. Key participants on this project were TTC, Black & Veatch, Wade & Associates, and Computer Solutions & Services. These participants gathered data using a specially developed questionnaire and also by contacting a number of municipal forums that are organized in cities across the United States. Because of their interest in the topic, there are many cities that made a formal agreement to participate and support the project. The project team has been working since June 2003 and finished in May 2005.
The final report for this project has been released by the WERF on CD-ROM. According to the TTC Website, “Nashville, TN remains the agency that furnished so far the most complete data on quantification of I/I from laterals and effectiveness of lateral rehabilitation.” For further information on this project, please visit the TTC Website, http://www.ttc.latech.edu/werf/index.html