For the connection to the central wastewater treatment plant on the Císařský Island in Prague, a pipeline was installed under the Vltava River using the HDD method. Tight bending radii complicated the pipe insertion, and the geological conditions were unstable due to the slate rock. Therefore, an integrity test was required to verify the integrity of the new pipeline after the installation. The egeplast SLM® DCT (Detection and Checking Technology) pipe system was used for this purpose.
Connection of a sewage treatment plant
The connection of the Podbabsk sewage treatment plant in Prague to the central sewage treatment plant on the Císařský Island presented the general contractor ZEPRIS with major challenges. To increase transport capacities, a double pipeline with dimensions of 400 x 23.7 mm was laid, and five manhole structures were installed on the island. The total length of the pipeline is approximately 1050 m. The trenchless sections crossed under the Vltava River and an old tree population at the edge of the river.
The trenchless installation using the HDD method under the riverbed of the Vltava River was carried out by TALPA-RPF. The start and end of the river crossing were already predetermined by the connection points of the original pipeline. Due to these fixed points, a relatively short distance, and the resulting tight bending radius, the drilling was challenging. The pilot bore was also a major challenge, especially on the bank side. Due to the slate rock in the area of the borehole, the geological conditions were unstable and could have caused difficulties in the borehole area when pulling in the pipes. Due to the longitudinal profile of the culvert and the very demanding geology of the subsoil, the choice therefore fell on the SLM® DCT pipe, which enables an integrity test immediately after the installation.
After 18 days, the jet drilling of the two 160 m long pipe strings under the Vltava was completed. During the technical monitoring of the construction, the operator was able to check the quality of the system and the integrity of the installed pipelines several times. The planning office was able to successfully create the project documentation.
“We have used the system that enables the inspection of PE pipes after installation for the first time. However, the good experiences will certainly lead to further applications in our trenchless construction measures,” explains Ivan Demjan, Managing Director of TALPA-RPF s.r.o
Project description
Connection of a sewage treatment plant to the central sewage treatment plant on an island
Challenges
Tight bending radii and unstable geological conditions due to slate rock
Solution
Verification of the integrity of the new pipeline after trenchless pipe installation under difficult conditions
Pipe system
1,050 m SLM® DCT for waste water pressure; Dimension: 400 x 23.7 mm
Project participants
General contractor: ZEPRIS s.r.o., Prague
Jet drilling: TALPA-RPF s.r.o., Ostrava
Project documentation: D-PLUS
egeplast
SLM® DCT
Verification of the pipe system’s integrity for construction performance acceptance
Increased operational safety
permanent Localization Capability
Trenchless installation techniques are possible without life-shortening damage or reduction of the safety factor.
