Before the Tunnel Boring Machine "Karpatką" of the consortium of Mostostal Warsaw S.A. and Acciona Construccion S.A. a total of 44 have been drilled to check for dangerous gases like methane and also excess water.

Yesterday the government site has released the following information (partially taken from a more detailed version here):

Detection of methane In July 2023, during trial pumping aimed at reducing the water mirror for the needs of tunnel drilling with a TBM machine, gas was found. Gas appeared in 2 out of 44 wells.

In order to ensure the safety of staff working at the construction site, the contractor suspended the work related to trial pumping and drilling of other wells. The presence of methane was confirmed using the appropriate equipment in gas samples. Samples for laboratory tests were also taken, which also confirmed the presence of methane in water. It is also worth emphasizing that the occurrence of gas did not stop the work on S19. Construction work continued on the rest of this 10-kilometer section.

From the very beginning, a wide team of specialists worked on the solving of this problem both on the side of the contractor and the investor with whom the team of experts from the AGH University of Science and Technology from Krakow and the Higher Mining Office in Katowice and the District Mining Office in Krosno collaborated.

Due to the detection of methane, it was necessary to properly prepare the TBM machine for work in methane conditions. After analyzes carried out by mining experts, as part of the machine retrofitting, it was necessary, among others Installation of the sensor system on the machine detecting the presence of methane at the tunnel drilling stage and the installation of a modified ventilation system with increased efficiency enabling the tunnel ventilation and preventing methane accumulation inside the excavation. It was also necessary to replace some components for devices that could work under the conditions found.

All these works result from the provisions of the EU ATEX directive relating to devices and protective systems intended for use in a potentially explosive atmosphere, which requires that the devices and machines that work in an atmosphere threatening to ignite or explode methane have adequate protection, primarily sparking.

It is worth emphasizing that the process of drilling the tunnel is subject to the provisions of geological and mining law, and therefore the contractor developed a draft tunnel in methane hazard conditions, which has gained a positive opinion of the Commission for Threats at the Mining Plant at the Higher Mining Office in Katowice. Subsequently, Appendix 1 was developed to the T1 tunnel drilling plant. This supplement in April this year. Pursuant to the law, he was approved by the decision of the District Director of the Mining Office in Krosno, which formally allows the start of tunnel drilling.

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As a Polish citizen, I am very content that such a work has been performed for work safety.

A more complete information on this Tunnel Boring Machine bored project is in this link I posted in another group. https://tunnelcontact.com/discussion/view/58383/poland-the-first-13-meters-of-tunnel-in-babica-has-been-excavated