A 900mm diameter, 123m long culvert in Argoed, Flintshire was in need of relining and initially a UV CIPP installer was awarded the project. After an initial CCTV inspection it was clear the UV system was not suitable due to the number of bends within the culvert - up to 45 degrees in places.
Colus were tasked with finding a solution to successfully line the culvert and determined that a hot cure inversion liner would best suit the project although the amount of fall (40m) over the culverts length presented a number of risks.
After a meeting with the client it was agreed that the liner to be installed was to be 30mm thick, the next problem was that that the amount of water required to install the water was around 20,000 gallons (90 tonnes) the risk was that if the liner was not supported at the downstream end it would over expand and split during the cure, it was decided that the liner was to be stopped flush with the end of the pipe so a stopped end would need to be built that would hold the weight until the cure was completed, this was built using steel rsj’s and timber boards.
A scaffold was then designed to take the weight of the liner and then built over the upstream end of the culvert in order to give the required head of pressure to install the liner after the scaffold and stop end was completed it was then time to start the installation of the liner.
Due to the location and limited space of the upstream end of the culvert a 80 tonne crane was contracted in to lift the liner from the refrigerated delivery truck to the inversion scaffold, water was then pumped in the liner to start the inversion, this was done using tankers. As to reduce the environmental impacted of taking water from the water mains in the area the water was sourced from a local treatment works final effluent.
When the liner had come to rest on the stop end the liner was filled with the water and the cure started by heating the water inside the liner to 85 degrees , this was reached in stages to ensure the cure was correctly done.
After the cure was completed the water was then cooled this was also regulated to ensure the curing was completed correctly, after the water was cooled it then needed to be removed from the line to ensure that the water would not contaminate the water course downstream of the culvert.
As the downstream manhole of the culvert was 10mtrs deep it would require a tanker that could suck out the water at that depth so a liquid ring tanker was brought in from the Colus depot in Worchester.