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

Option 1) – Construct new substructure                      Option 2) – Repair the existing bridge.
under bridge, as designed by Arup. 50                       50-year life if maintenance schedule is
year deck life & 100 year substructure life                 properly followed. This option makes no
(if maintenance schedule is properly                        special allowance for sea level rises or
followed). From our review of the design                    associated canal erosion
report for this option, it appears that there
is no special allowance for sea level rises
or associated canal erosion.
Comparison life costs (between 2014                         Comparison life costs (between 2014
and year 2064) = estimated $9,804,747 +                     and year 2064) = estimated $5,095,500 +
GST                                                         GST

Notes:                                                      Notes:
    1.   All costs are shown in today’s dollars. No             1.   All costs are shown in today’s dollars. No
         allowance for inflation or interest has been                allowance for inflation or interest has been
         made.                                                       made.
    2.   Costs estimates are for comparison                     2.   Costs estimates are for comparison
         purposes only. For detailed costs, it would                 purposes only. For detailed costs, it would
         be      necessary    to   develop    detailed               be     necessary     to   develop    detailed
         Engineering solutions and arrange for                       Engineering solutions and arrange for
         estimates or tenders from an Estimator or                   estimates or tenders from an Estimator or
         Civil Contractor                                            Civil Contractor
    3.   Extra bridge deck width is not included in             3.   Extra bridge deck width is not included in
         this estimate. Only the existing width is                   this estimate. Only the existing width is
         included.                                                   included.
    4.   The existing deck will be at the end of its life       6.   The existing deck will be at the end of its life
         at this time. Installing a new cathodic                     at this time. Installing a new cathodic
         protection system, if bridge engineer deems                 protection system, if bridge engineer deems
         condition of reinforcement and high strength                condition of reinforcement and high strength
         steel strand adequate at that time, could                   steel strand adequate at that time, could
         extend life.                                                extend life.
    5.   The substructure (piles, pilecap, columns,             4.   The substructure (piles, pilecap, columns,
         headstock) should have a further 50 years                   headstock) will be at the end of its life at
         of life, provided that maintenance schedule                 this time. Life could be extended by
         is followed                                                 installing a new cathodic protection system,
                                                                     if condition of reinforcement and high
                                                                     strength steel strand is deemed adequate
                                                                     by bridge engineer at that time


We can see that Option 2 (repair the bridge) is clearly a lower cost to Council and the
community, now and over the next 50 years. Option 1 would have a project delivery cost
of 2.9 times higher than recommended Option 2 (repair the bridge); and Option 1
comparison-life costs would be 1.9 times higher than Option 2.



5.0 Conclusions
In summary, the cracked pilecap beams, cracked piles and high chloride test results,
initially indicated the reinforcement would be in very poor condition. The observed
reinforcement in the pilecap beams of Piers 3, 4 & 5 and piles (No. 3 & 8, Pier 1) suggest
that reinforcement is in better condition than we first expected. It appears that macrocells


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