Marmaray Project – Bosphorus Railway Crossing Tunnel
The Marmaray Project represents one of the most technically advanced railway infrastructure programmes ever undertaken, connecting Europe and Asia through an immersed tube tunnel beneath the Bosphorus Strait in Istanbul.
Through Techno Engineering and Associates, Valentin Milkovserved as Contract Manager supporting the General Directorate of Infrastructure Investments of the Republic of Turkey during the construction and delivery of this nationally strategic transportation programme.
The project integrates underground rail tunnels, high-capacity commuter rail infrastructure, and seismic-resilient engineering to deliver a modern cross-continental transportation system.
Contract Management Role
Acting as Contract Manager, Valentin Milkov supported contract administration, claims management, variation assessments, and coordination between multiple stakeholders involved in the delivery of one of the world’s most complex rail infrastructure projects.
The role required close collaboration with engineers, contractors, project directors, and government authorities to ensure contractual compliance, risk mitigation, and alignment with programme objectives.
Contract & Governance Focus
Responsibilities included evaluation of contractual claims, change orders, payment certifications, and schedule implications across civil works, tunnel construction, rail systems installation, and station development.
The work also required maintaining documentation integrity, ensuring contractual transparency, and facilitating communication across international contractors and public-sector stakeholders.
Project Scale & Technical Overview
- • Total project alignment: 76.3 km
- • Underground section: 13.6 km (Ayrılıkçeşme – Yedikule)
- • Total stations: 40 (37 above ground, 3 underground)
- • Immersed tube tunnel length: 1,387 m
- • Deepest point below sea level: 60.46 m
- • Design speed: 100 km/h
- • Passenger capacity per direction: 75,000
- • Minimum train headway: 2 minutes
Strategic Impact
The Marmaray Project represents a milestone in global infrastructure engineering, combining seismic resilience, underwater tunnelling innovation, and metropolitan rail integration at unprecedented scale.
Contributing to this programme provided Valentin Milkov with deep exposure to complex infrastructure governance, large-scale contract management, and multi-disciplinary coordination under demanding technical and institutional environments.