DCN October Edition 2019

PORT DESIGN, CONSTRUCTION & DREDGING
“Three cyclones in recent years, crossing north of the Port of
Mackay, have been a significant issue,” Mr Hinschen says.
“Cyclone Dylan category-2 and Cyclone Debbie category-4… they
both crossed the coast pretty much at the same place about 200km
north of Mackay, the impact was [especially] severe in Dylan due to
the duration of the storm surge.”
Following Tropical Cyclone Debbie, NQBP general manager
engineering and development Rochelle Macdonald said
investigations, including 3D laser scanning, showed damage that
was worse than first thought.
“The southern breakwater in particular has suffered damage to
the slope facing the sea,” Dr Macdonald said at the time.
We estimated that we needed
about 80,000 to 90,000 tonnes of rock.
We ended up replacing about
140,000 tonnes
John Hinschen, NQBP
“Like so many others in the region, TC Cyclone Debbie delivered
a powerful blow to our east coast operations.”
Mr Hinschen says TC Debbie wrought about $18m worth of
damage and TC Dylan in 2014 caused about $23m. He notes the
various impacts, including the costs of repairs, the impact of
shipping movements and the potential loss of revenue to the port
and customers and disruption of fuel supply to industry.
Mackay is a key port for the Bowen Basin coal-mining sector,
bringing in fuel and machinery, keeping the minerals sector
operating, as well as supporting the sugar and cane-growing sector.
“So fuel not being able to come through the port pretty much
stops Queensland’s economy very quickly,” Mr Hinschen says.
The southern breakwater at Mackay helps protect the port from
waves and oceans swells, however, Mr Hinschen says it was not
intended to be “a cyclone-safe haven”.
He notes significant damage to the southern breakwater during
TC Dylan, with the damage exacerbated due to it occurring over a
six-day period with many tide changes.
“We had damage from well down the wall to well over the top of
the wall,” he says.
“The biggest problem when fixing breakwaters is getting enough
rock in the timeframe. We’ve had rocks supplied from many
quarries. But duration of your repair is driven by how fast you can
get your rock, no matter how you call it,” he says.
“It is a very slow process in getting the right size and quantity
of rock.”
THE NORTH-WEST
Heading to the western side of the country, the North-West Shelf
is similarly affected by raging tropical storms. Director of Baird
Australia, David Taylor, spoke about the impacts of cyclones on
ports in that part of the world and some important adaptations.
Mr Taylor notes the North-West was the most active cyclonic
region in the Southern Hemisphere, with the highest frequency of
category-4 and category-5 storms. Some destructive cyclones had
included TC George in 2007 and TC Orson in the late 1980s and
TC Veronica earlier this year, which flooded mines and swamped
infrastructure.
“Having been involved in developing design criteria in this part
of the world for the last 15 years, it is definitely something that
warrants further consideration,” Mr Taylor says.
He notes work at Port Hedland regarding reducing the likelihood
of a channel blockage, given the tremendous costs involved should
a capesize vessel run ground on the channel margin. Various
factors would determine the impact but “the potential impact is a
long and very complex salvage operation to clear the channel and
clear the ship”.
“So the channel blockage risk has existed ever since these
ports were developed. But the value of that risk has exponentially
increased in the last 15 years,” he says.
“We have seen a rapid increase in port capacity. The number of
ships going through these channels has increased and there has
been a major increase in the value of the commodity – iron ore.”
A ROCKY RECOVERY
Following Cyclone Dylan, NQBP began emergency work on the
southern breakwater, including proceeding with work on the
1.8km-long (90metres had been completed prior to the cyclone).
“So we continued with that upgrade during the repair. We
estimated that we needed about 80,000 to 90,000 tonnes of rock. We
ended up replacing nearly 145,000 tonnes for the southern breakwater
and that was completed by August 2015,” Mr Hinschen says.
“So eighteen months after the storm, we just finished fixing the
southern breakwater.”
Repairs started on the northern and middle breakwaters in
November 2015, with about 23,000 tonnes of rock placed on the
northern breakwater and 21,000 tonnes on the middle breakwater.
Mr Hinschen says they were fortunate at Mackay to have their
own quarry within about one kilometre of their breakwaters.
PORT-RELATED DAMAGE FROM THE
CHRISTCHURCH 2011 EARTHQUAKE
All four Cashin Quay wharves were written off at a cost of
NZ$300m to replace.
Most of the Inner Harbour wharves were also damaged
and were either written off or had a significant reduction in
their levels of service.
The port head office had to be demolished, most of
the breakwaters had damage and the fuel wharf was also
written off.
One of the coal loaders was severely damaged and the
west coast coal mines had five days of storage and they had
to shut down as well, with big delays to coal shipping.
Container cranes were damaged when they jumped off
their rails.
LPG
36 October 2019
thedcn.com.au