It is widely known that a significant proportion of East Anglia relies for its existence on the effective operation of widespread land drainage networks. Without these networks much of the region would not be able to function in the way that it does and the population would be hard pressed to continue their lifestyles in the way they do in the modern world due to the high ground water levels.
Much of the drainage to keep ground water levels in check is achieved using local pumping stations that take water from the land drainage network and pump it into local rivers and drainage channels that remove the water off the land and out to sea so keeping the local area from flooding. These pumping stations are under the control of the Internal Drainage Boards (IDB’s).
However, when undertaking rehabilitation of a pumping station at a site near Kings Lynn, a reverse syphon carrying water from the pump station to the main drainage channels that fed the local estuary, was found to have failed and there were fears that water normally carried by the syphon away from its local pumping station would cause problems.
The failure of the syphon meant that water from the pumping station was not, as would normally be the case, all removed from the network but that it was being returned back into and potentially undermining the pumping station due to leakage in the syphon. This was also causing the river bank near the pumping station to erode. It was causing problems in the pump station as water was recycling, meaning the pump station was working significantly harder than it should, incurring extra cost and potentially could lead to significant flooding problems for the area.
After careful consideration of the situation and the options available to affect a repair or replacement of the syphon by the project’s main contractor ADC East Anglia, working in close association with Dyno-Rod Norwich, specialist consultants and product suppliers it was decided that a lining option would offer the best solution with minimal disruption to the pumping network, the local residents and the importantly the environment.
The project required remedial repairs to be made on the 22 m long x 450 mm diameter cast iron reverse syphon. To ensure the long-term effectiveness of the repair ADC and Dyno-Rod Norwich called upon the expertise of CIPP Technical Services and product supplier C. J. Kelly Associates both of which have many years of experience in the lining of pipes in difficult situations.
A detailed look at the liners available, the resin options and the longevity required of the final installation as well the pressure fluctuations that would be encountered during the operational life of any liner led to the selection of a 450 mm diameter, 7.5 mm thick twin wall flexible liner. The 22 m long twin wall liner used on the operation comprised two thinner walled polyester needle felt liners which when laid and stitched together formed a final 7.5 mm thick liner with a single PU outer coating. The reason behind using the twin wall liner option was that given the geometry of the reverse syphon the liner used not only needed to provide a strong, long-life final product but also needed to offer significant flexibility during the inversion process and to ensure an effective curing process. The twin wall liner also offers a better resin impregnation process for the MC thermos-reactive resin used. Once successfully inverted the liner was heated to 90oC and kept that this curing temperature for about 9 hours.
The MC Construction Chemical resin used for the lining work the Konudur 170 TL-NV product as supplied by C.J. Kelly Associates. Designed as a Thermo-reactive epoxy resin for CIPP liner systems the product offers:
· Low-viscosity, two-component epoxy resin
· Warm-hardening epoxy resin
· Light-blue pigmentation
· Long application time
· High strength
· Short curing times depending on curing temperature
· Good adhesion on concrete, brick and ceramic
· Can be applied to dry and moist mineral or metallic substrates
The blue pigmented resin enables control of the impregnation process whilst the liner/resin combination is flexible enough to negotiate bends in the syphon. The thermosetting resin has a high chemical and thermal resistance and is easy to use. There is also no annulus gap between the host pipe and liner as the installed lining material sits flush to the old pipe wall. More importantly for the project in hand, the resin is certified to be environmentally compatible with groundwater so would cause no pollution potential for the ground water being moved through the syphon into the local river system.
Subsequent to the installation the IDB replaced the pumps in the station and completed a full pressure test the results of which showed that the leak in the syphon had been sealed and that it was working to the specification required once more.
Steve Paige Director with ADC East Anglia Ltd said of the works: “The project from the beginning had many issues. A remote location and access for plant to maintaining the flows during the works were all potential problems. However combining the expertise of all parties involved, the job was accurately accessed, planned and completed on time.”
Commenting on the project for Dyno Rod Norwich Mark Prendergast said: “This was an interesting and somewhat unusual installation that demonstrated to the Client how effective no-dig solutions can be. It was also very rewarding working closely with ADC and CJ Kelly Associates to achieve an excellent result.”
John Kelly of C.J. Kelly Associates said: “This project took several weeks to coordinate as we had to install the liner miles from anywhere in the fens just outside Kings Lyn. The liner was up and over the flood bank with a 90o bend on the apex of the bank and allowing for the time of year, over pumping and flood control was a major part of this lining project as was the flexible 450 mm diameter liner which was specially manufactured. Mark and Daryll from Dyno Norwich as well as ADC Kings Lyn performed ‘above and beyond’ on this difficult project, in my opinion this was the most interesting project in East Anglia for several years and despite its challenges it was brought in on time and on budget. As with any project you need the right product and the right contractor if you want to end up with a good lining project and a satisfied client.”