Hot Tapping and Plugging Procedures Enable Replacement of Concrete Pressure Pipelines Reaching the End of Service Life without Service Interruption

Abstract

As water pipelines and sewer force mains reach the end of their service life, leaks and uncontrolled line failures become more common. These failures may result in unacceptable environmental incidents and lack of adequate potable water and sewage service. This paper will discuss how hot tapping and plugging is used as an effective enabling procedure that allows the replacement or rerouting of concrete pressure water lines and sewer force mains while maintaining operations. The discussions in the paper will include: the tapping and plugging concept and sequence; engineering principals involved; forces developed in the application of the procedure and the need to address those forces with adequate thrust block designs. Two specific projects will serve as case studies to highlight the use of the technique. One case study is about the relocation and replacement of a prestressed concrete cylinder pipe sewer force main in an urban area. The other case study is the replacement of a municipal concrete pressure pipe (noncylinder) water supply pipeline. TAPPING AND PLUGGING ENABLES REPLACEMENT OF FAILING PIPE As water pipelines and sewer force mains reach the end of their service life, the frequency of leaks and uncontrolled line failures become more common. These failures may result in unacceptable environmental incidents and lack of adequate potable water and sewage service that create unsanitary conditions for system users. Hot tapping and plugging may be an effective enabling procedure that allows the replacement, repair or rerouting of concrete pressure water lines and sewer force mains while maintaining operations. When necessary for continued operations a temporary bypass line is installed to permit continuous flow during the repair or modification (Figure 1).