Sept. 27, 2007 -- Insituform Technologies® has been, for the past 30+ years, one of the most recognized names in the development of pipe lining systems. The recent and significant change in attitude of sewer network owners and water companies towards the lining of pipelines with significant groundwater infiltration problems across the UK, has once again brought Insituform Technologies' expertise to the fore. Most established lining systems are well-suited to work where infiltration is not too extensive, but where groundwater inflow is high owners have been searching for an improved performance from liners.
Such infiltration flows create the problems of higher flows at the treatment plant and dilution of the effluent, making it more difficult to treat. In some cases, the use of more traditional liners in very high flow situations have been known to transfer the infiltration to unlined sections further along the pipeline rather than being stemmed altogether.
To overcome these problems, Insituform Technologies Limited (ITL) has been working hard on its liner materials and with resin manufacturers, and in association with Thames Water in the UK, to develop, test and establish its new 'fit-for-purpose' infiltration prevention liner system, which substantially stems infiltration flows at source, eliminating any need for subsequent remedial work elsewhere in the pipeline.
An important part of the development process has been the product testing. Thames Water has established a standard test, overseen by WRc in the UK, which verifies product suitability for high infiltration lining operations. ITL has undertaken significant work to develop and prove the new system through the Thames Water/WRc testing regime, using both water inverted/hot water cure or air inverted/steam cure techniques. Subsequent to the test WRc issued a letter to ITL confirming the success of both curing methods.
ITL has been using the infiltration prevention liner system to rehabilitate high-infiltration sewers across the UK. Since its introduction, less than one year ago, ITL has successfully installed it on over 2.5 km of pipeline. The following highlights two such projects located at two different sites across southern England from Devon in the west to Essex in the East.
Beneath the village of Coleford, near Yeoford, Crediton, Devon, an old, 150 mm diameter, vitrified clayware sewer was in need of renovation. The Water Company responsible for the sewer, South West Water in association with its project engineering company Black and Veatch, investigated the sewer and found that it suffered significant infiltration problems that could affect the choice of rehabilitation technique used. Normal flows in the pipeline would generally have been expected to be well within the capacity of the pipeline. However, the infiltration due to the groundwater and pipeline route detailed below increased these flows by up to 40-50%, hence the need for the rehabilitation.
To eliminate as far as possible the excess flows, whilst minimizing the impact of the works on the small local community, it was decided to line the sewer with the infiltration prevention liner system offered by ITL with the hot water cure installation option.
The resin-based lining system effectively reduces liner shrinkage to nil during the curing process when used in conjunction with Insituform Technologies' standard non-woven fabric liner tube. The liner tubes, depending on the circumstance of the lining operation, the curing process used and the final product requirements, are available with either polypropylene, polyurethane or polyethylene inner coatings, a facility not offered by other installers.
In total, four individual, 150 mm diameter lining operations, with the epoxy-based infiltration prevention liner system were required subsequent to the usual cleaning and preparation works.
Pre-installation surveys on the pipelines showed heavy infiltration as lining runs 1 and 2 ran beneath a stream. Similarly, the remaining two runs ran beneath a ford. It was these locations that gave rise to the groundwater levels that gave the infiltration.
On the Coleford project, however, it was not the lining system per se or the pipeline that was to test the ingenuity and expertise of the lining crews. Having decided to utilise the hot water cure lining system, weather conditions came into play quite dramatically.
Despite the difficulties, however, on completion of lining of all four installations, the post-installation surveys confirmed that all infiltration had been stopped and the renovated system completely met all of the client's expectations.
Great Horkesley is a village on the outskirts of Colchester in Essex. As part of its work with Anglian Water Group (AWG), main contractor Barhale was required to renovate a 150 mm diameter vitrified clayware pumping main sewer. In order to complete the work Barhale enlisted the services of ITL which decided to utilise its infiltration prevention lining system to complete the renovation using an epros-manufactured EPROS310 resin to impregnate the liner to combat excessive infiltration in the sewer.
The work sites and pipeline route were located over approximately 800 m running along the main A134 road, known as The Causeway, which passes through the village of Great Horkesley and some link roads.
The location of the works meant that erection of scaffold towers to invert the linings into the sewer could prove problematical, given the nature of the roads and the traffic usage. It was therefore decided to utilise a Controlled Head Inversion Unit (CHIP), which enables the liners to be installed effectively from ground level, minimising the operational footprint of each set up. The system utilised hot water curing which required around 6 to 7 hours cure time for each liner.
ITL provided the lining crew as well as a CCTV unit to carry out pre-installation surveys to ensure the pipeline was ready to line. Pipe cleaning was achieved using jetting and tanker support with traffic management being sourced locally.
Impregnation of the liners was carried out at ITL's Ossett works, with the liners being road transported to site for installation.
The nature of the infiltration prevention lining system meant that, post-impregnation, delivery and installation were required to be completed relatively quickly to enable a successful installation of product as previously mentioned. To enable this to be achieved, impregnation procedures were revised using coordination between and notification of any difficulties from the Horkesley site to the factory operators.
Infiltration, which was more prevalent in the downstream section of the pipe route, created surcharge conditions toward head of system. Some excellent work by the jetting contractor during the course of the works, restored flows to at least 90% of the lining sites, which enabled the majority of the works to be completed according to plan. The infiltration in the last section, however, created conditions that required an open cut repair by Barhale before lining could be completed.
In addition to the lining program, ITL was requested to survey and remove intruding objects in another four pipeline sections.
All works were successfully completed and the pipeline re-commissioned by late summer 2007.
For more information, see: www.insituform.co.uk