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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.
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