Cal Park Hill Tunnel Rehabilitation Program Review

Transforming a collapsed train tunnel into a rails-with-trails pathway, the Cal Park Hill Tunnel rehabilitation project restored a crucial transportation link between San Rafael and Larkspur in Marin County, California. The historic railroad tunnel is now a dual-use recreation trail and commuter rail facility. Schnabel provided independent constructability review services to the HDR-led team completing the makeover.

The tunnel is approximately 1,100-feet long with concrete tunnel linings at both the north and south portals, and timber ground supports within the interior. The linings had severely deteriorated, with a complete collapse of the tunnel lining near the southern portal, missing and badly rotted timber supports in the interior, and a partial collapse of the timber tunnel lining near the north portal.

Our constructability review services included an assessment of the 90% tunnel and approach improvement-related drawings and specifications. The rehabilitation alternatives we reviewed involved lining removal and sequencing; ground support schemes including shotcrete, rock bolts, contact grouting, steel ribs, and steel lagging; and drainage control provisions. Our assessment was successful in identifying several aspects of the project where the proposed rehabilitation approach required further refinement and/or the use of alternative construction methods.

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