For many years, water companies across the globe have utilized resin injection sealing systems as part of their portfolio of renovation techniques for deteriorated sewer pipelines to minimize infiltration problems, with products superseding the earlier acrylamide resins.
Acrylate products have been successfully used on numerous sewer renovation projects where infiltration of groundwater has been the major symptom. However, there has always been a suspicion of a potential problem where, in certain circumstances, if groundwater levels fall, the drying of the current acrylate product may lead to them failing.
When acrylate is allowed to dry significantly, there is the potential for it to shrink and become less flexible. This can lead to failure of the seal, and infiltration starts again when groundwater levels return.
With some £7 million budgeted over the AMP 4 period (the government/regulatory pricing structure period for water services within the United Kingdom) for this type of sealing work, Wessex Engineering & Construction Services (WECS) decided to investigate the potential for a new sealing gel that would overcome this potential failure situation by not drying out or failing in such circumstances.
WECS has been working closely with specialist U.K. utility contractor Sdi-unistride, which handles the majority of WECS’s injection sealing work. During the early part of 2006, before his unfortunate loss in a road accident in August, James Fulker, then managing director of Sdi-unistride, suggested that a new gel could be formulated that would give the new properties required for such sustainable repairs.
In March 2006, WECS and Sdi-unistride, working with De Neef U.K., a manufacturer of acrylic resins, undertook a new product development program.
Working closely together, client, contractor and manufacturer initiated development work on both polyurethane-based and acrylate-based products. Initial testing showed the potential for a new acrylate product to be most favorable and further development then focused on this option.
While the precise chemical make-up of the new product is commercially sensitive information, it utilizes a rubberized, acrylate-based chemical to replace a proportion of the water used in the sealing gel. This dramatically reduces the potential for shrinkage under dryer operating conditions and keeps the seal flexible, effectively removing the potential of glassification. The new product is known as SewerSeal JF.
On completing the tests and field trials, Wessex Water’s Technical Standards Committee approved SewerSeal JF for use on Wessex Water’s pipe networks after studying a comprehensive technical submission detailing all testing and attributes of the new material, along with re-testing results for the original acrylate resin, to allow comparison of the tensile strengths and other properties. SewerSeal JF is now the material of choice for WECS.
As part of the trials for the new material, the new SewerSeal JF product was successfully utilized in February 2007 as the first commercial project in the United Kingdom on sewer renovation works at Montacute House near Yeovil in Somerset. The work was done by Sdi-unistride and over nine days, some 170 liters of SewerSeal JF were installed over 372 m of 225-mm diameter sewer pipe. Several further commercial applications for both Wessex Water and others have since been undertaken or are currently in operation. These included a project at Bowjeyan village in the far southwest of Cornwall, near the town of St. Just.
Bowjeyan village is one of many such settlements along the Cornish coast and is typical in layout, with narrow lanes and very limited access in terms of utility construction. This in part is why, for some years, the village has suffered from localized flooding problems associated with some of its sewers.
Over a period of five days, the new SewerSeal JF system was used to eliminate infiltration over a significant part of the Bowjeyan sewer network.
WECS has also used the product in the village of Newton Toney, northeast of Salisbury, Wiltshire, where 1,500 m of 150-mm diameter clay ware pipeline has been in the ground for many years and exhibited a significant degree of infiltration. The whole sewer network serving the village has been tested and 30 percent of all the joints in the system were found to be faulty. These were all treated with SewerSeal JF.
The new product is expected to provide a system that will enable Sdi-unistride to seal more than 500 m per week under normal operating circumstances and at a cost that is only marginally higher than that using the current sealing resins, while significantly increasing the life expectancy of the sealed pipe.
Ian Clarke is a freelance writer and owner of No-Dig Media Services, based in the United Kingdom.