Award of Excellence: Water Systems Category

Beltline Interceptor Repair Project

St. Paul, Minnesota

Submitted by Paragon Constructors, Inc.

The Beltline Interceptor is a storm run-off tunnel that lies 20 to 65 feet (6 to 20 m) below the city of St. Paul, Minnesota. Constructed in 1915, this underground infrastructure was in need of repairs caused by inadequate concrete cover on the upper arch of the tunnel and poor concrete consolidation, resulting in severe spalling, cracking, and rebar corrosion.

Access was limited to manhole ports spaced every 1100 to 1200 feet (335 to 365 m). Continuous rushing water was present throughout the work schedule, at times as deep as four to five feet (1.2 to 1.5 m), as afternoon temperatures rose and caused snow to melt. Shotcrete was used to repair the horseshoe shaped tunnel, which required pumping the mix up to 650 feet (200 m) through the tunnel.

Great care was taken to insure a safe working environment and to create a quality project that only a few people will ever see.