The construction of the “Czajka” WTP emergency collector - from A to Z
Once again, PE-HD technology has facilitated the quick and streamlined construction of a temporary pipeline on a pontoon bridge. This unconventional sewerage bypass had to be built in the wake of a failure in the GRP collector, a component in the wastewater trunk system for the “Czajka” wastewater treatment plant (WTP). Thanks to the properties of polyethylene pipes, which include low weight, flexibility, and easy handling of installation, the pipeline was commissioned for operation less than 2 weeks after deliveries to the construction site. This allowed the shutting down of the emergency sewage discharge into the Vistula.
The first failure of the GRP collector buried under the River Vistula, and feeding Warsaw’s sewage to “Czajka”, was in August 2019. It was then that decided to initiate the emergency discharge of untreated sewage into the river, and to build a temporary pipeline on a pontoon bridge. DN1000 PE-HD pipes from Uponor Infra were used for this solution. Uponor Infra provided a total of 2200m of piping, which formed two pipelines, each measuring 1100m in length.
The second failure occurred almost exactly one year later: the emergency sewage discharge into the Vistula, necessitated again by the failure of the “Czajka” collector, required a green light for another construction of emergency pipeline over a pontoon bridge (the previous emergency piping solution was removed in November 2019). On 3 September 2020, just a few days after the failure on 29 August 2020, Uponor Infra signed a contract with MPWiK to build a “turnkey” emergency bypass for the failed pipeline. The emergency pipeline which transfers sewage from left-bank Warsaw to the “Czajka” WTP was once again constructed from PE-HD pressure pipes.
This time, the emergency pipeline was built from PE-HD pipes (measuring approximately 2 km in total) purchased by Wody Polskie, and supplied by Uponor Infra, in 2019. Once disassembled and disinfected, the pipes were handed over free of charge to MPWiK, and reused. The pipes passed the laboratory tests at Uponor Infra, including weld-rupture-strength tests. The piping material revealed no evidence of ageing through exposure to waste water or disinfectant. The remaining 1300m of piping required for the project were manufactured in priority mode at Uponor Infra’s production plant in Kleszczów, near Bełchatów.
The PE-HD emergency pipeline in figures
The first delivery of pipes was completed on 4 September 2020, just one day after signing the contract. Nine pipe-welding machines, and over a dozen service crews, were deployed at the construction site, and worked 24-hour shifts. The piping was assembled on schedule, with the first pipes welded on 5 September 2020. The welding process came up to full speed the next day, and it took only eight days to make 246 welds, a truly-record number for this type of project. In three more days, 10 additional welds were made for connections required by valves.
Our crews made a total of 256 butt welds, which ensured tightness and high tensile strength along the entire length of the emergency pipeline. Each joint passed the quality inspection performed jointly by Uponor Infra and MPWiK. The 250m-long pontoon bridge over the Vistula was put in place by the Polish Army.
In total, we laid two DN1000 diameter pipelines, each 1600m long (3.2 km in total), in the record time of 13 days!
However, the emergency pipeline built this time is slightly different from the one built in 2019. It is approximately 1 km longer, as last year there were 2 pipelines of 1,100m each, while this year there are 2 pipelines of 1,610m. What’s more, the wastewater is be collected directly from the chamber located on the premises of the “Farysa” Plant, and not from the place of discharge. This way, even if the pumping of sewage has to be stopped temporarily, it will be possible to contain it within the sewage system for some time. The sewage is carried to the “Świderska” Plant on the right-bank of the Vistula River, and then by a collector towards the “Czajka” WTP.
The emergency pipeline will remain in operation until the end of November 2020, after which there will be a risk of damage to the pontoons from ice sheets forming on the river. Following its removal, the piping from the emergency pipeline can be re-used for future projects.