Defining, Understanding Lateral Rehab Options

Part 2 in a series
By Jeff Griffin, Senior Editor | May 2011, Vol. 66 No. 5

Members of the NASSCO Lateral Committee continue to refine a document to provide a comprehensive overview of lateral and main-lateral connection repair and sealing technologies.

NASSCO (the National Association of Sewer Service Companies) is a national organization dedicated to establishing and implementing standards for rehabilitation of underground utilities and is comprised of several hundred members representing rehabilitation industry manufacturers and suppliers, municipalities and utility districts, engineers and contracting firms.

A draft of the report was completed in January 2011 and is undergoing peer review by committee members, said Larry Kiest, chairperson of the committee. The draft’s contents covering types of resin systems and lining tubes for lateral rehabilitation appeared in the March issue of Underground Construction magazine. This report covers methods of installation, curing and sealing connections.

Cured-in-place pipe (CIPP) liners are available with various resin systems, including polyester, epoxy, vinyl ester and silicate. Depending on job conditions and pipeline effluent, one resin may be preferable over another.

Lining tubes typically are constructed from a needle punched felt or a knitted tube. Liner tubes vary in density and flexibility in order to negotiate small diameter pipe and bends and to reduce pressures for inverting the liner so the tube is not overstressed. Correct installation practices combined with the right material are keys to successful lateral lining rehabilitation.

Manufacturer installation procedures must be strictly followed to reduce risk and increase the chances of a successful installation. It is easier to renew a lateral from an excavated pit, and the risk is much less than renewing a lateral from a clean out or remotely from the main pipe. However, there is no digging required when a lateral is renewed through a clean-out or from the main pipe and when a lateral is renewed from the main, the connection is also sealed.

Basically, there are risks and rewards for all lateral repair/renewal methods, and the positive and negative attributes of these technologies are a major part of the NASSCO lateral committee’s report. The key is to know which technology to use and when.

For the lining process, laterals may be accessed from a clean out located either outside or inside a building, from a manhole connecting to a lateral, an access point made by an excavation, or remotely from the sewer main. Accessing the lateral where no excavation is required is typically preferred.