If you have been around Grant Street or North Main Street between North Street and Sibley Road during the past couple of weeks you have probably noticed some work going on in the sewers and large trucks with Insituform® marked on the side. This is a $121,000 project to line two sanitary sewer mains in the City. They finished the last section of sanitary sewer today on North Main Street between North Street and Buchanan Street.
Insituform® is a trenchless cured-in-place-pipe technology. I first became familiar with this process when I served in Riverview, Michigan. The City of Riverview used Insituform to line most of its older sanitary sewer mains in a $13 million effort to reduce the amount of inflow and infiltration of storm water into the system.
Here is a link to animation showing how the Insituform® process works. This process is very cost-effective since we do not have to dig up the road to replace the sewer line. The process usually takes a day or less (instead of days or weeks for other methods) and when it is done we have a brand new sanitary sewer pipe that will last for decades.
While the new pipe is slightly smaller than the old pipe, the flow through the new pipe is much better. [Trivia note: In situ is Latin meaning "in the original position." Therefore, Insituform® means "to form in the original position" or "to form in place."]
Sometimes, it is more cost-effective to use other methods for rehabilitating or replacing a sewer pipe such as performing an "open cut" replacement of a pipe. An above ground method is usually best if the line is in an open field or other open area that is easily accessible where there is not much infrastructure or obstructions above the sewer. Also, when the size of the sewer line needs to be increased, some other methods are used.