The mystery surrounding the material that resembled liquid cement and flooded streets in Kypseli has been resolved by Elliniko Metro S.A., clarifying that it is soil slurry related to the construction works of Metro Line 4 and not a cement leak.

According to the company, during tunnel excavation using a TBM (tunnel boring machine), a special foam with chemical additives is injected under controlled pressure. This foam is used to balance ground pressure and protect overlying structures.

In the case of Kypseli, the mixture of excavated material and foam escaped through an old sewage pipe. It initially ended up in the yard of an abandoned building and then spilled into surrounding streets, creating an image that alarmed residents.

Disruption and traffic interruption

The incident occurred on Wednesday afternoon (15/04), around 16:00, when residents of the area saw the material continuously flowing out from the yard of the building.

Within a short time, the slurry spread onto the roadway, covering parts of streets and causing serious traffic disruptions.

The Traffic Police proceeded to close traffic on Sofadon, Skyrou, and Evias streets, as the volume of the material made vehicle passage impossible. In some places, the slurry height exceeded 60 centimeters, even covering the wheels of parked motorcycles.

The contractor consortium of the project immediately carried out removal and cleaning operations in the area.

As stated in the Elliniko Metro announcement, the phenomenon is not linked to any safety issue nor does it cause permanent pollution.

At the same time, it is clarified that the tunnel excavation in this section of Line 4 has already been completed, with no subsidence or other structural issues recorded in the area.

The official explanation by the company comes to reassure residents after the strong concern caused by the incident.

Statement by Elliniko Metro S.A.

Regarding the leakage of soil slurry in streets of Kypseli, Elliniko Metro S.A. issues the following update:

“During excavation works with a TBM (tunnel boring machine) for the construction of the Line 4 tunnel, at the excavation face, foam composed of special chemical additives is injected under controlled pressure, mainly for safety reasons regarding overlying structures, in order to balance ground pressure. In this way, and without any subsidence occurring, the tunneling of the section between Katechaki and Evangelismos stations has already been completed.

In the Kypseli area, earlier today, leakage was observed through an old sewage pipe of soil slurry, meaning a mixture of the excavated material itself with injected pressurized foam, which ended up in the yard of an abandoned building and subsequently in nearby streets.

The contractor consortium has already proceeded with removal of the material and cleaning of the area. This incident does not create any safety issue or permanent pollution.”