Safety precautions against fuel leakage into NATM tunnels of Uskudar – Umraniye - Cekmekoy Metro Project

Abstract: A sudden water inrush occurred along with fuel from the old / unused underground storage tanks of a fuel-station through one of the forepooling drills and thus, construction of the double- tube NATM tunnels with 30 m bench cross-section was stopped on 12 June 2015 in Uskudar - Umraniye - Cekmekoy Metro Project. The risks and safety precautions for re-starting the construction, are summarized. Probe-drill holes with 8 m length were drilled to drain the accumulated fuel within the fractures of limestone and mudstone and continue the construction. Ventilation system was revised; an automatic gas measurement and warning system was established; tunnel illumination and drainage were ex-proofed; some precautions were taken against a fire / explosion; safety clothes were provided for tunnel crew; the crew were educated for safety in the emerging conditions and evacuation. Surface of the temporary support was lined with a special membrane resistant against fuel and gasses.