He said the seawall, parts of which were 100 years old, contained boulders cemented in place. The main risk was that the concrete would fail in a quake and the boulders would fall.
The unbudgeted $40 million repair bill comes as the council faces cuts of hundreds of millions of dollars a year in running costs and capital investment in a 10-year budget being prepared by Mayor Len Brown.
It also follows concerns expressed by many ratepayers about a focus on spending in the central city at the expense of outlying suburbs and rural areas.
Mr Walden said the council was looking at a contract for a significant upgrade to the seawall to start about the middle of next year. The work would take about a year.
Repairing the seawall is one of several downtown projects, including the upgrade of Quay St, the possible privatisation of Queen Elizabeth Square in association with a major redevelopment of the Downtown Shopping Centre, a new bus terminal in lower Albert St and improved ferry services and public spaces.
The "downtown framework", as the work is called, is to go to a council committee next month.
Waitemata councillor Mike Lee said the seawall repair was a great opportunity to put a section of Quay St underground and provide extra harbourside space.
A mid-1990s plan by former Auckland City Mayor Les Mills for Britomart included plans to put part of Quay St underground, but this was dropped for cost reasons.
Pricetag
$40m repair bill for the downtown seawall between Princes and Marsden wharves. Parts of the seawall are 100 years old
$700k is being spent patching up a section between Princes and Queens wharves