Project Description

In 1998, LACHEL & Associates, Inc. (LFA) inspected, evaluated, and designed a rehabilitation program for a historic canal tunnel in Pennsylvania.

The Union Canal Tunnel is the oldest existing transportation tunnel in the United States. At the time of construction in 1826, the tunnel was considered an engineering marvel for this country. The tunnel was originally 728 feet long, but was subsequently reduced in length to 620 feet as part of the canal widening project in 1858. The canal and tunnel served as a primary transportation link until 1885. The construction of the tunnel required excavation through a ridge of mixed sedimentary rocks utilizing a primitive form of drill and blast excavation techniques. The interior of the tunnel is unlined with only the portals and approaches being lined with dressed stone masonry. Over time, the retaining walls of the approaches were gradually overloaded due to an accumulation of debris, eventually causing a massive failure of one of the approach walls. The historic significance of tunnel was recognized in 1994 by being designated a National Historic Landmark.

Scope of Services

LACHEL & Associates, Inc., as a subconsultant to Kauffman Hickey Architects, assessed the stability of the tunnel, portals, approaches, and the surrounding slopes. Specifically, LFA was responsible for assessing the safety of the unlined tunnel for use by the public. LFA mapped the tunnel walls documenting visible structural features. Additionally, LFA designed a slope stabilization system for the approaches consisting of shotcrete and soil nails. LFA produced drawing details and specifications for implementation of the slope stabilization efforts. The overall rehabilitation program included brick and mortar restoration of the portals and approaches, complete reconstruction of the failed approach retaining walls, and slope stabilization. Due the significance of the structure, all rehabilitation alternatives maintained the architectural and historical integrity of the tunnel.

Client

Kauffman Hickey Architects - Lancaster, PA
Lebanon County Historical Society