2015-03-31 I&S Committee - Item 5 - Attachment 1 - Munna Pt Bridge Repairs Level 3 Bridge Report

       •   We expect that significant corrosion of all piles could start in the next 1-3
           years (2015-2017), making the bridge dangerous and increasingly costly to
           repair by 2017.

It is our understanding that there is a limited budget for this project. Tod Consulting’s
team has taken this into account in our recommendations. We strongly recommend and
urge Council to take actions 1 to 8, so that:

   a) Public safety is maintained.
   b) The repair cost and whole of life costs can be spread over a number of years.
   c) With impressed-current cathodic protection and protective paint-on coatings, the
      bridge life can be extended by an estimated 50 years to year 2064, if these
      protective measures are properly maintained.
      The media and the public could find a 24-hour-internet-connected 1979-era
      bridge interesting (see note i below).

       Notes:
       i) The cathodic protection system must include a modern internet-connected monitoring
       system. NSC or their nominated maintenance subcontractor can remotely check that the
       bridge is protected, and warning messages can be automatically sent to their mobile
       phones
       ii) The estimated life is based on the design conditions of today (2014), such as flood
       levels & velocities, sea levels, air temperatures, vehicle loads and the like. No allowance
       has been made for increased loads brought on by future climate change or vehicle type
       changes.
       ii) Life might be extended further by installing a replacement cathodic protection system, if
       a bridge engineer deems climate conditions, condition of reinforcement, and condition of
       high strength steel strand, satisfactory in the future. Special scour protection around piers
       and abutments, or even lengthening of the bridge might be required by that time.

REPAIRS BETWEEN NOW AND AUGUST 2014:

1. a) Confirm the reinforcement depth on site for the previously tested Pier 4 column, and
re-test the (inconclusive) chloride levels from the surface to the reo depth. This will help
to confirm if cathodic protection of the columns is required or not in the later stages.

b) Install an additional 900mm diameter concrete column between each pilecap beam
and headstock (6 columns total). This will effectively reduce stresses in the pilecap beam
reinforcement bars to 25-50% of current levels. The concrete and reinforcement should
be designed for a 100 year design life using AS5100.5 Bridge Code, and a
Portland:Flyash blended cement should be used for the concrete. Real world life is likely
to be 50 years, longer if protective coatings (installed in later stages) are maintained.

Background to this recommendation

The role of the pilecap beams is to transfer the loads amongst the 10 (cracked) piles
underneath. Bridges are typically designed with a safety factor of at least 2, so allowing



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