PROS AND CONS
Replacing a damaged and leaky pipe with a structurally stable pipe resistant to leaks reduces inflow and infiltration into the sewer collection system. This can lead to a reduction in sanitary sewer overflows from the municipal sewer system.
The EPAis encouraging Region 4 municipalities, for example, to achieve this reduction through self-assessment of their Management, Operation, and Maintenance (MOM) programs. The goal is to develop a plan to correct sewer infrastructure problems, and trenchless technology can help in achieving the plan's goals.
The program's effect may have been conveyed by comments from one PUBLIC WORKS survey respondent, who reported opting for trenchless technology because “my MOM told me to.”
In choosing between traditional open-cut and no-dig methods, limitations of trenchless processes must be considered. Some methods, such as CIPP and sliplining, will cause a reduction in pipe diameter; this reduction may be offset by reducing the roughness coefficient, so overall changes to hydraulic capacity must be evaluated.
In addition, your project may require extensive excavation to create access pits and reconnect laterals. The need to install numerous laterals along an old or new line will decrease the benefits gained by using trenchless methods for the main line.
For rehabilitation and replacement projects, the length of bypass time for existing flows may impact the decision to implement a no-dig application. If lengthy sewer shutdowns are required and cannot be coordinated with homeowners and businesses, you may have to opt for open-cut construction. — Broviak is the director of public works/city engineer for LaSalle, Ill.