Steel net long-term safety solution

17:00, Aug 31 2014

A 1600 square metre steel net will be anchored into a section of the Mangaotaki Bluffs above State Highway 3 to prevent rockfalls like the one that struck and killed passing motorist Joy Thompson.

The $2.5 million safety project will start today.

The NZ Transport Agency announcement comes after the Waikato Times reported state highway bureaucrats had been repeatedly told that rockfalls posed "a significant hazard to motorists" beneath the bluffs.

Major engineering works were never done to remedy the problem.

Instead, standard maintenance, emergency responses and minor risk-reduction operations were done, including a $45,000 contract that was scheduled to begin three days after the fatal accident on March 28.

The revelations were exposed in Transport Agency documents released to the Times under the Official Information Act.


They stretched back to 2000 and show engineering contractors were "certain" rocks would continue to fall onto State Highway 3 and potentially strike vehicles long before Thompson, 74, was killed beneath the southern Mangaotaki Bluffs.

The rock that struck her and her sister hit with such force that it stoved in the car's passenger side and spun the car 180 degrees on to the opposite side of the road.

In May, Thompson's daughter Karen Ngatai was "disgusted" and in tears when she heard the revelations. "It was preventable - it didn't have to happen.

"I didn't have to lose my mother like that."

The project was expected to be completed by December, NZ Transport Agency's regional performance manager Karen Boyt said.

The stretch of highway has been down to one lane with a temporary barrier to contain falling rocks since March. Traffic management will remain while contractors complete the work.

Boyt said the steel net was a long term solution.

"Geotechnical specialists worked their way through a detailed inspection and rock scaling process earlier this year to gain a better understanding of what work was needed to stabilise the cliff face," she said.

"Since then we have removed larger rocks by blasting at the site but our investigations show that the steel net is the best long-term safety solution."

The southern Mangaotaki Bluffs consist of relatively hard limestone and sandstone over weaker mudstone.

Boyt said a crew of abseilers would begin by clearing loose material off the rockface.

Most of the work to anchor the net would be completed using drill rigs attached to two cranes.

"When the project is complete, the steel net will be secured to the bluff by 500 anchors.

"This will dramatically reduce the risk and impact of rockfalls in the future."

Waikato Times