The Cross County MetroLink Extension project expanded the St. Louis MetroLink service towards the Clayton, Maplewood and Shrewsbury neighborhoods. The alignment includes three cut and cover tunnels which are currently experiencing water infiltration contributing to early concrete deterioration and other serviceability issues. Concrete floor and wall segments were cast-in-place against soldier pile and lagging walls with a bentonite-type waterproofing material between them. Pre-cast arch tops were installed and waterproofed using a separate bentonite waterproofing membrane followed by 5 to 20 feet (1.5 to 6 meters) of granular backfill material. Much of the construction occurred during cold and wet conditions, which was considered when assessing the performance of the waterproofing system.
Expert Review Services for Tunnel Leakage Assessment:
Gall Zeidler Consultants provided expert review services of design and construction documents to assess possible causes of tunnel leakage in the MetroLink Extension tunnels. Currently, GZ is providing design services to address the tunnel leakage. These consist of water diversion measures implemented from within the tunnel.