Gorge crews uncovering more rock on the slope


The NZ Transport Agency says crews at the Manawatu Gorge are striking increasing amounts of rock at the slip site, and a big job remains ahead shifting the rock and completing the benching.

NZTA Palmerston North state highways manager David McGonigal says the increased amount of greywacke rock that crews have uncovered lately is both a blessing and a curse for the crews working to secure the hillside.

"It's much more difficult and time-consuming to shift rock than dirt, so it's proving to be hard work for our crews up on the slope. The silver lining is that it's shedding more light on the geological makeup of the slope, and the more solid rock that we find, the more secure it's likely to be.

"However, the rock we've uncovered so far is quite fractured, so benching the hillside remains the linchpin of keeping the slope stable in the long-run"

Mr McGonigal said the NZTA are eager to announce a prospective timeframe for the reopening of the gorge, and this would be ready next week once the NZTA had formed a clearer picture of the complex task that lies ahead.

He says crews have had another week of good progress stabilising the slip face.

"The third bench is nearly done, and we expect to start cutting the fourth bench next week. Mother Nature's been smiling on us this week, and we're crossing our fingers for more fine weather so we can continue to make solid progress."

"Crews continue to work long hours, seven days a week, and as we cut more and more into the slip, we're getting a clearer picture of exactly what we're facing."

Mr McGonigal says the planting is taking hold well on the batter (edge) of the first bench, and moss hydroseeding on the Bench #2 batter is planned for next week.

The Woodville end of the second bench is also being tapered to allow more working room for the crew on the third bench.  This tapering will also allow for better drainage that will help to keep the hillside secure.

Mr McGonigal says that while the NZTA has come across larger amounts of greywacke rock, the slip surface is still made up of different kinds of rocks and soil.  The rocks have all weathered at different rates, so some are soft and some are very hard, and they range in size from pebbles to boulders.  Some crumble and some have to be excavated using specialist rock breakers.

He says the worksite is still very challenging, and safety remains paramount.  Spotters are in place at both the top and bottom of the slip to watch for any indication of movement that may put workers at risk, and crews work with the utmost care at all times.

Road crews continue to cart out as much material as possible, although the material below the benches has been left in place as it acts as a working platform for the machines as they come down the slip.  This means that only small amounts of it can be removed by the trucks down at road level.

The river is still flowing, and the NZTA remains very mindful about minimising the impact on the river.  The 200 metres of river either side of the slip remain closed, and the NZTA are still working closely with its river engineer and Horizons Regional Council to monitor river levels and any impacts the slip may be having.

Mr McGonigal reiterated the NZTA's gratitude to police for their enforcement of Saddle Road and the Pahiatua Track as part of Operation Detour, and urged motorists to drive with care and observe the posted speed limits at all times.