Transhipment is the process of off-loading a container or goods from one vessel and loading it onto another vessel. A shipment may undergo more than one transhipment during its journey from origin port to destination port.

1. Hydrography for Transhipment
Neil Hewitt,
Managing Director
MSc (IHO CatA) MSSSI CPHS1
Precision Hydrographic Services

2. Hydrography for Transhipment
Metro Mining Bauxite Hills Project, Skardon River
Skardon River is 90km north of Weipa on
the western side of Cape York in
Queensland.

3. Remote Area
Only viable means of access by barge from Cairns

4. Aim
Safely transport bauxite along a 9km shallow river to bulk carriers offshore.
Simple…right?!

5. Barge Loading Facility
Skardon
River
Shallow Mobile Seabed
Vessel at Anchor
The Challenge
Distance from barge to anchorage is approx. 12km along a
winding river and across an area of mobile seabed consisting on
sand bars and sand waves.

6. Due to the nature of the location and hazardous navigational aspects,
hydrographic survey was an important part of the operation to ensure the
barges could be safely navigated to the ships.
Tasks included:
• Install Tide Gauges
• Conduct initial baseline survey to determine navigation plan
• Identify areas that require bed levelling
• Provide bed levelling survey support
• Provide ongoing cost effective survey solution
Survey Tasks

7. Tide Gauges
Radar Gauges
Transmitting UHF
FTP Via 3G
Ellipsoidal
connection
Historical Datum
Connection

8. Tide Display

9. Historical Datum
Recovering the historical datum

10. Historical Datum

11. Historical Datum

12. Historical Datum

13. Datum Connection
Datum Connection MOF Datum Connection TSB
LAT at the barge ramp was known below the PSM from MSQ tidal analysis in 1998,
this value was then connected to the ellipsoid via levelling and GNSS observation.
Data at the Tide Station Beacon was submitted to MSQ for analysis and subsequent
determination of LAT below the tidal benchmark established on the beacon.
This BM was also connected to the ellipsoid by GNSS observations.

14. Hydroid
From the MSQ analysis, historical datum and
connections to the ellipsoid a model of LAT to Ellipsoid,
or Hydroid was developed to facilitate accurate survey
to the ellipsoid in real time.

15. Baseline Survey

16. Baseline Survey

17. Baseline Survey
The real problem started when exiting the river into the areas for mobile
sand banks and sand waves.
Sand waves had moved, changed shape and got shallower.
The channel had moved and in some cases narrowed.
At times the was pretty much gone.

18. 200
9
201
7
This shows areas where the depth at LAT is shallower than 1.3m in
2009 with the black line being Nav route that had been determined.
The seabed had changed significantly since the nav route had been
defined requiring a change to the nav route.

19. Navigation Route
It was clear there was now a better route through the
shallows and was amended to take a route that would
minimise bed levelling requirements.

20. Navigation Plans
On completion of the baseline survey and once a navigation
route had been defined, detailed Navigation and bathymetric
plots were created by PHS GIS Coordinator who worked closely
with the client and MSQ GIS department.

21. Minimum surveyed depth outside the river is 0.4m
The minimum surveyed depth along the navigation route was 0.4m LAT, it is clear
that there is no way to get a 3m draft barge over that without at least 3m of tide,
even then it is pretty tight.
So we need a significant amount of tide to float the barges out over the sand bars.

22. 0
0.5
1
1.5
2
2.5
3
3.5
4
Skardon River Mouth
Luckily we do get 3m of tide in the Skardon River.
However, it only leaves a very small window of a up to 5 hours to get the barges
out, and as most of us know those sorts of time frames are very difficult to work
with.

23. Bed Levelling
We can’t do much about the height of tide so the solution is to move the
seabed around to increase the actual depth, effectively reducing the amount of
tide required to navigate safely over the sand bars.
A sweep system was manufactured onto the Profit Radiance vessel to take the
tops off the sand bars.

24. Bed Levelling

25. Qinsy provides the Tug master with a clear indication
of the areas needed to sweep as well as direction need
to sweep material into deeper areas to maintain the
passage through the sand bars.

26. Survey Support for Bed Levelling

27. • Rapid data turn around
• Surveyed to datum in real time
• Data cleaned on board
• Data loaded onto the tug system
Bed Levelling Survey Requirements

28. Results from Bed Levelling
The results were quite good, although the material turned out to be harder to move
than expected, a deeper navigation corridor was created in the shallow areas to 1.3m
LAT, increasing the minimum depth by almost a metre.
We did also note that the sand bar had increased in size since the 2017 survey,
requiring more volume to be removed than first anticipated.

29. R2Sonic Norbit
The R2Sonic showed slightly crisper resolution than
the Norbit.

30. Both system very capably detected small sand
waves of less than 5cm in height.

31. R2Sonic
99% all cells had a
95% Confidence of
5cm or less
Norbit
97% all cells had a
95% Confidence of
5cm or less

32. The client engaged the
services of hydrographic
surveyors early and
planned to continue with
the ongoing support.
It is very important that
Hydrographic surveyors
are engaged early on in
any project that involves
coastal infrastructure and
safe navigation, to advise
on tidal datums, correct
survey methodologies and
ongoing requirements.

33. THANK YOU!

47. Thanks for listening
Questions?