Providing Solutions on Land and Sea
RANGE OF PROJECTS

Sonar and magnetometer survey of seabed feature in Geelvink Channel, Geraldton

Escalating interest in locating HMAS Sydney (which sank in WWII with the loss of entire 645-man crew) resulted in the survey of a seabed feature located in 24 fathoms at the northern end of the Geelvink channel and 15 miles off Lucky Bay, south of the Balline fence-line. Terry Ash (professional fisherman) located the "Lucky Bay Lump" some 30 years ago, which has yielded excellent catches of pink snapper and crayfish.

This seabed feature or 'lump' is several hundred metres long and rises some 10 metres above the seabed with sharp sides, smooth top and the suggestion of a hull shape. It has been considered in recent years to possibly indicate the final resting place of HMAS Sydney.

Our interest in this area is based on recent oceanographic and historical research which indicates the Sydney lies in shelf waters approaching the northern entrance of the Geelvink Channel.

This survey was carried out on 7th October 2001 using modern search techniques and a modest budget of $5,000. Sea state was calm with an 8 knot breeze, 10+ metre water visibility and south-bound migrating humpback whales.

Sidescan sonar with a 800m wide swathe and 10cm resolution was towed at 6 knots to survey the 'lump' and surrounding square kilometre of seafloor. Navigation used a 12-channel GPS with resolution better than 10 metres, despite US military activity in Afghanistan. The sonar image indicates an elongate hard carbonate reef zone, but none of the discordant features that characterise an intact or shattered steel shipwreck.
A magnetometer was then towed on six traverses across the 'lump' to record the total magnetic field with 1 nanotesla (1 nT) resolution at 6 metre intervals. Magnetometer response was less than 20 nT whereas a 7000 tonne warship would provide a magnetic signature greater than 500nT under these survey conditions. The integrated magnetometer and side-scan sonar survey indicates that HMAS Sydney is not at this location.

It is a pleasure to acknowledge the crew (Steve and Max) and skipper/owner (Terry & Cheryl Ash) of "Miss Horrocks II" for sharing their knowledge and west-coast hospitality. David Burchill and Max Cramer provided focus and encouragement. John Bye, Ros Page and Michael McGeorge are thanked for introducing us to the mystery of HMAS Sydney.

National Pollution Inventory NPI (1999 - 2002)
Dioxin and Furan emissions have been measured from several industrial sites in South Australia using USEPA Method 23 and 23A. Results generally conform with the European standard of 0.1 ng/Nm3.
Samples are analysed by the AgriQuality Dioxin Laboratory at Gracefield, New Zealand. We visit the laboratory regularly to keep up with developments.
Zinc smelter Gas Train Surveys (1998-9)
A gas sampling system was set-up to cope with high dust loadings at temperatures up to 1100°C and velocities to 30m/s. Gas analyses were made by both IR and EC instruments, with data acquired from up to 5 sites spread over 80 metres of ductwork simultaneously.
Large-scale seabed search (1994-5)

Click map to view enlarged image
 A large-scale search was carried out in Gulf St Vincent, South Australia to locate a submerged vessel. Orientation survey on dredge and pontoons sunk off Port Stanvac is shown. The initial search area exceeded 500km2 with water depths ranging to 40 metres. Sidescan sonar coupled with magnetometer was used on a grid search, with a line spacing of 700metres and DGPS navigation to 4metres. A target was located after 120 hours of survey and identified for the client by detailed sonargram. (See enlarged image of map.) Total survey cost was <$50,000.

Oil exploration (1992-9)
Reconnaissance oil exploration surveys have been undertaken using nearsurface geochemical techniques developed in North America and Australia during the 1980's. Some onshore case-histories were published in Severne et al. 1991, Bull. Assoc. Petroleum Geochemical Explorationists. v.7 no. 1 pp.88-115.
Current activity is focussed in South Australian continental shelf waters, primarily screening seismic structures for active microseepage. Analyses are carried out in-house by conventional GC-FID tuned for ppb levels of ethane and propane.

Continuous Emission Monitoring System (CEMS)
A portable CEMS unit was brought on-line in 1999. This Horiba PG-250 unit measures NOx, SO2, CO, CO2 and O2 using chemiluminescence and non-dispersive infra-red. It meets all USEPA requirements for backup CEMS. NATA calibration gas standards ensure accuracy and dilution probes cope with wet (>20% moisture) and high (>1%) SO2, high (>20%) CO2 gas streams. Logging is via RS-232C interface to user specification.