The stadium's original seating
is cast-in-place concrete risers placed on compacted
earth berms and as-excavated
soil with variable height
retaining walls at the field level. This system
was experiencing significant instability marked
by progressive retaining wall tilt, fractured
risers, and increasing separation at the top of
the seating from the concourse level. Our preliminary
analysis revealed stability deficiencies that
were used to set the final design criteria. The
stabilization system used two soil anchors, placed
near the tops of the field retaining walls, for
each individual run of wall. The wall sections
were temporarily shored while the lower riser
was removed and replaced as a horizontally spanning
load distribution element between the soil anchors.
The most heavily distressed risers were removed
and replaced, the new riser design reconciled
the cause of instability revealed in the preliminary
analysis and subsequent riser replacement will
follow this design. Construction took place in
the spring of 1999, final cost excluding turf
replacement was $580,000.
Contractor: Structural
Systems, Inc. of Missoula
Soil Anchors: Chance Helical Piers installed
by Matelich Const., Kalispell, MT
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