During our bridge meeting last Thursday, Albert Halff had proposed raising the abutments and adjacent grading by 2 feet to accommodate the “off-the-shelf” bridge that they had chosen.
 This was in order to provide 2 feet of freeboard above the 100 year flood elevation.  I said I would look at the grading along the creek embankment and the existing Savoye One building
to see if the grade change could be accommodated, thinking we would be able to construct some retaining walls to make up the extra two feet of grade change.  After further thought, I
remembered why the bridge was set at the elevations currently shown on the park drawings.  The initial design intent for the bridge was to be a thin, sleek profile.  Victor Lissiak looked
into the pre-fab bridges and found that you cannot get one that is 150 feet long without the structure being nearly 3 feet thick from top of pavement to bottom of the beam.  That is
the reason why we chose to pay Victor an additional fee to design the bridge from scratch in order to have a profile more on the order of 8” thick.  That said, it would be very difficult
and expensive to redesign the abutments and associated grading to raise the bridge 2 feet as proposed.  Savoye One has an existing retaining wall immediately adjacent to the abutment
landing on the northwest side of the creek.  If the bridge is raised, the abutment and landing would be higher than this retaining wall.  In addition, the proposed jogging path would
need to be constructed as a handicap ramp on each side of the abutment, complete with handrails, and designed with a switchback or a serpentined path in order to accommodate the difference
in grade.  I think we need to investigate further options for this bridge that will not raise the grades that are currently in place. 

 

BRUCE F. DUNNE, P.E.

President

icon Consulting Engineers, Inc.

Bicentennial Financial Center

250 W. Southlake Blvd., Suite 117

Southlake, Texas  76092

Phone: (817) 552-6210

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Mobile: (817) 707-9711