Subject of renovation: siphon under the Vistula River with a diameter of DN 1500 and a length of 280m
Location: Kraków
Depth of well foundation: 8 - 10 m
Installed sleeve: Brandenburger Liner BB2.5
UV curing lamp set: UV Prokasro 12 x 1000 Watt
Curing speed: 0.6 m / min
Sleeve installation time including calibration: 9 hours
Lamp curing: 8 hours
Investor: MPWiK Kraków S.A.
Contractor: P.P.H.U. Akwa J.Biskup, S. Owczarek Spółka Jawna
This summer, when most Cracovians were passionate about the athletes' struggles in Rio de Janeiro, an important operation for the city was carried out under the Vistula, which few people were able to see. In between Olympic broadcasts, a siphon passing under the river was repaired using a UV-cured glass sleeve. The length of the repaired DN1500 section was 280 m
At the end of April 2016, we signed an agreement with MPWiK Kraków S.A. for the implementation of the task of Renovation of the DN1500 combined sewer siphon line under the Vistula River. The siphon to be repaired is one of four pipelines transporting all wastewater from the north of Krakow to the south of the city, where it reaches the sewage treatment plant in Płaszów.The beginning of the pipe (the upper head of the siphon) is in Miedziana Street and the end (the lower head of the siphon) is in the building on Portowa Street.
When the investor handed over 'our' line to us, he made the task a little easier, diverting the sewage to the other three siphons and the one that needed to be repaired was walled up in the huge chamber of the upper head of the siphon on Miedziana Street. There were a lot of unknowns in the beginning because the sewer, put into service in the 1950s, had basically been in operation all the years. It was therefore a great mystery what could be found inside. All that was known was what the developer had provided. However, there was not much of this information. We knew that the infiltration of water into the canal was about 20m cubic metres per day, and that there was a fibre optic cable that had to be suspended in the canal vault.
So get on with it!
The preparatory work began by placing pumps in the sewer and pumping out what was coming in through leaks in the pipe. The next stage was hydrodynamic cleaning. And then the first problems arose... The solid cleaning of the siphon was made possible by the cooperation with Wuko Krecik. When we started the cleaning by moving everything in the siphon, a very unpleasant and intense "smell" spread, to say the least. In the building where the end of the sewer is located, the concentration of hydrogen sulphide and methane jumped to such high levels that it was not even on the scale of our gas detectors. So the only sensible solution was to flee the building. Only after flushing the siphon several times did the concentrations of harmful gases fall, allowing us to continue working and inspecting the sewer. Cleaning was not easy.
After the initial hydrodynamic flushing, it was necessary to start working manually in the canal and remove build-up and sediment from the canal, and then suspend the fibre optic cable so that it would not interfere with us when we pulled the sleeve. Continuous aeration of the inside of the duct, working in heavy oxygen apparatus and the perseverance of the duct preparation team yielded excellent results and, after nearly two months, was successful. The pipe was prepared for renovation in an exemplary manner.
As the starter well was very narrow and 9m deep, an additional element in preparation for the repair itself was the excavation of a spot trench at the top head of the siphon and the cutting of a mounting window in the well (wall thickness 80cm!) to allow for the insertion of the liner and the renovation using CIPP technology. Once everything was perfectly prepared, all that remained was to wait for Brandenburger to manufacture the appropriate sleeve. Noteworthy, the production of the sleeve was also a challenge in itself, as no one had ever produced such a large and long sleeve before. The sleeve itself is already a 'real heavyweight' - 26 t of material, which we only had to 'throw' into the channel. The biggest concern before installing such a large and heavy sleeve was the pull-in procedure. It was with this element that we expected major difficulties.
A pleasant surprise was the fact that the sleeve retraction took place without any problems in a record time of 45 minuT! Not even a failure of the feeder controller hindered this, which was rectified in express time.
Next steps refurbishment such as filling the sleeve with air and pulling the lamps was already a formality.The German liner supplier lent us his UV kit - a Prokasro with a 12 x 1000 Watt chain. The set was equipped with a sufficiently long cable in an extra lagging (so as not to damage the liner at the siphon break), which allowed the sleeve to be cured once under the Vistula. The curing speed set by the operators was 0.6m / min. Once the lamps started working, all that remained was to watch in real time as success took shape and became a reality. It took eight hours to drive the lamps from Miedziana Street to Portowa Street. This is all it took for us and our Brandenburger colleagues to become pioneers in our industry. The siphon with a length of 280m and a diameter of DN1500 was successfully renovated in one section using a glass sleeve!
Before starting, we had many questions about how to undertake such a difficult task. However, the experience we have gained over the years with large-scale sewer renovations has paid off. Once again, it has been confirmed that good preparation is the basis for success. Analysis and early elimination of problems allowed the contract to be executed perfectly.
text: Piotr Grawżyn
