Recommended NZ | Guide to Money | Gimme: Competitions - Giveaways

Oamaru harbour breakwater rock armouring - 140 years of care

Contributor:
Fuseworks Media
Fuseworks Media

Rock around the clock

Waitaki’s property team are excited about the arrival of a 35 tonne loader, due to start work this week as part of the ongoing rock armourment of the breakwater.

This latest project consists of supply/delivery/placement and battering of 6000 tonne of conglomerate rock towards the southern end of the breakwater (adjacent to historic Macandrew Wharf); being the continuation of 8500 tonne of rock armouring completed in 2018-2019.

The last major rock armouring project occurred in the 1930s, involving the construction of the Ramsay Extension and the placement of a protective rock apron along the entire seaward face of the breakwater. This philosophy proved successful as there were no further records of damage until the 1970s, in an area which had most likely lost its rock protection.

Over 80 years on from the last time the breakwater was completely rock armoured, once again the focus of Waitaki District Council is to ensure this 140 year old historic structure remains in place for generations to come.

Due to improved 21st century technology, trucks and earthmoving machinery are bigger and stronger today, and are able to deal with rock armouring units up to 23 tonne, which is well in excess of the much smaller rock placed in the 1930s.

Abstract from the draft Oamaru Harbour Plan - August 2020

The harbour breakwater is the most critical structure within the harbour. It protects the harbour from the prevailing seas and without it the rest of the harbour would face the full force of the ocean, resulting in rapid deterioration of the rest of the harbour structures and risking the waterfront itself, much of which is reclaimed land.

The contract has been awarded to Road Metals who have a proud history servicing the Waitaki district for over six decades. The first job for their massive loader will be to create a ramp from the beach over Macandrew Wharf to gain access to the seaward side of the breakwater. Trucks will start carting in rock over the next fortnight, with some of the 286 truck loads carrying only 1 rock up to 23 tonne in size. The project is expected to take 6-8 weeks to complete (weather dependent).

Mayor for Waitaki, Gary Kircher said, "The breakwater serves the same purpose it always has - protecting our harbour from the ocean’s turbulence. The sailing ships and coastal traders may have gone, but as we strive to make Oamaru Harbour the best little harbour in New Zealand, the protection afforded by the breakwater is crucial. We are committed to retaining it as a safe harbour for locals and visitors to continue enjoying for many years to come."

In all, how much is the project expected to cost? The total project cost is $273,000. The previous 2018-2019 rock armouring projects cost about $400,000. The final rock armouring project is expected to get underway in 2022 and will comprise of another 7000 tonne of rock and is expected to cost around $350,000. The head of the breakwater is proposed to be protected in this next campaign as well as a final section south of the Ramsay Extension.

The construction of the breakwater and Macandrew Wharf between 1871 and 1884, at Oamaru was vital to create a safe anchorage for ships along a notoriously dangerous coast. The structure has historical, social and architectural significance in that its construction helped the town of Oamaru prosper into the late-nineteenth century hub of North Otago.

Wildlife are part of the planning too: The species most vulnerable to disturbance at the breakwater are Redbilled gulls and white-fronted terns. Their breeding season (nest-forming to chick fledging) runs from late August through to late January/February, with nesting mainly September to December. In the past these species have typically nested on the Ramsays Extension, which is some 150m away from the current rock armouring area.

Photos

1904

1937

1955 -large area of rock has washed away south of Ramsay Extension.

2007 - almost no rock armouring. Ramsay Extension almost lost.

2020 - Current photo

All articles and comments on Voxy.co.nz have been submitted by our community of users. Please notify us if you believe an item on this site breaches our community guidelines.