Bridge stayed open despite risks

The old footbridge is to be replaced with a new design (artists's impression top right) over summer. Photo / Supplied

Pedestrians were allowed to keep using an 85-year-old footbridge above Auckland's Tamaki Drive for four months after engineers had said it was not safe.

On October 27 Auckland Council closed the bridge to the Parnell Baths and Point Resolution, more than 10 months after engineers had given it just a six-month clearance.

But although the council cited the six-month limit in its announcement, without saying when the clock started ticking from an initial engineering report from consultants Tonkin & Taylor, it now insists temporary repairs it conducted at the end of February would have extended the bridge's life for another year without endangering the public.

That followed a second report from engineers Peters & Cheung recommending old steel trusses be repaired or replaced "within the next year".

The Tonkin & Taylor report recommended to the council on December 14 last year that it should replace the bridge, which crosses the main trunk railway line and the tidal channel to Judges Bay as well as Tamaki Drive, as they considered it "safe for the public to use for another six months only".

Contractors have since demolished the bridge, ready to build an architecturally striking replacement for $3.5 million over summer.

The February repairs, during which the bridge was closed for three days, involved strengthening much of its deck with structural plywood.

According to papers the Herald has obtained from the council, that followed Tonkin & Taylor's discovery of advanced corrosion to steel supports under sections of the bridge's superstructure across the railway and the tidal channel, which were built in 1927.

Less severe corrosion was found in the bridge's third section, which was built as an extension over Tamaki Drive to the waterfront in 1972, although its handrails were deemed in immediate need of repairs.

But the council, with the Waitemata Local Board, decided to replace the entire structure after separate advice that its ad hoc appearance gave it a negative heritage value.

Although Tonkin & Taylor recommended notices at each bridge approach to restrict loads to no more than 20 pedestrians at a time, it took the council two months to erect those after it had repaired the handrails.

It then hired a watchman and brought forward the deck strengthening by several weeks after KiwiRail - as operator of passenger and freight trains under the bridge - questioned the adequacy of the notices.

"If your report indicates over-loading risks from pedestrians, then in my opinion there needs to be more than a sign to ensure this does not occur," KiwiRail structures inspector John Kilkenny said in an email on February 13 to council projects manager Greg Hannah.

"I would expect to see immediate temporary strengthening works to remove this identified risk while you plan the bridge renewal or close this structure down immediately."

After being told on March 2 that the bridge had been strengthened and reopened for normal loads, he complimented Mr Hannah on "nice work". A KiwiRail spokeswoman told the Herald the company had nothing to add.

Although Mr Hannah said in an earlier email to KiwiRail that the Tonkin & Taylor report gave the bridge "six-month life for structure", he told the newspaper that the plywood reinforcement had left it safe enough for public use until it could be replaced during this summer's annual summer maintenance and construction shutdown of Auckland's rail network.

The new bridge will be built about a metre higher so power lines for electric trains can go underneath.

Pt Resolution footbridge

1927: Spans over railway and channel to Judges Bay built.
1972: Extension over Tamaki Drive built.
Replacement programme
Bridge cost: $3.5 million (walkway connections funding to be confirmed).
December 26 to mid-January: Construction (evening closures of Tamaki Drive).
March: Connection to upgraded stairs to Parnell.
Easter to June: Replacement of walkway connection to bridge from Parnell Baths (after baths close for season).