NZTA works to expose damaged bridges at Manawatu Gorge


The NZTA says the Manawatu Gorge slip is down to one sixth its original size as crews prepare for the task of assessing the damage of the road and bridges.

NZTA state highways manager David McGonigal says the Higgins crews have made superb progress, and the productive rate of dirt clearance means that the NZTA should be able to make a thorough assessment of the extent of damage to the underlying road and bridges over the next month.

"Our operations are continuing 24/7, and progress by the teams carting the debris out has been excellent. We're moving much closer to fully excavating the bridges, and as we dig down further we are getting a much better idea of the level of damage we can expect."

Mr McGonigal says this week alone the NZTA has shifted close to 20,000 cubic metres of debris. That makes a total of nearly 310,000 cubic metres gone, and about 60,000 more still on the road.

"We've cleared five-sixths of the dirt, and while there's still plenty of work to do, we are ploughing through it as fast as possible."

Mr McGonigal says the Woodville end carting crew has located the eastern bridge and, as expected, significant damage to the bridge has been identified.

The Woodville bridge has four spans (the sections between the bridge supports) and three piers (the supports themselves), and work this week uncovered Span #4 and Pier #3. A preliminary assessment has shown that the beam for Span #3 is missing, presumed destroyed in the slip, and Pier #3 has rotated. The spans and piers are crucial to the bridge's integrity, and are a good indication of what the NZTA is likely to find further down.

Given that the slip face in this section was very steep and close to the road edge, it is expected that the beams for Spans #1 and #2 may also be missing, and Piers #1 and #2 will also likely be damaged, if they are still in place.

"Seeing damage to the bridges uncovered is not the greatest news, but also not completely unexpected. We still need to confirm the extent of damage, so we are going to bolster the bridge structure with debris from the slip, continue to remove slip material and expose the entire bridge."

"Building and fixing bridges is something we're pretty experienced at, so we're keen to get in and begin repair and reconstruction work as soon as we possibly can."

Mr McGonigal says that while slip clearance work continues below, a crew has also been working above the slip, sorting out some loose ends, including:

  • Rock lining the drainage channel on Bench #1 and installing an overflow pipe
  • Installing a culvert pipe on the track above the slip
  • Finishing off the track for DOC, and
  • Shaping the farm track above the DOC area.

"We're really thrilled that the track we cut to begin our work on Bench #1 is going to stay in place. Our earlier discussions with DOC revealed that they'd been wanting to make a track through this particular area for some time. Their preferred route was slightly different to the one we proposed, so we realigned our track accordingly. This was a win for both sides, and that's a great thing. It was such a hard slog just getting it cut that I'm glad it's going to be a permanent feature."

Mr McGonigal says the telltale green tinge up above reflects the work the hydroseeding crew have been up to this week. The crew have been finishing the work above Bench #4 and all the areas that could be reached below.

"Hydroseeding is a vital part of our work to regenerate plant life on the hillside, and we are very pleased with how far we've come in this respect."

Mr McGonigal says that the NZTA reiterates its gratitude to the slip crews and the wider community for their ongoing perseverance during the closure.