ABSTRACT
AN INITIAL EVALUATION OF UNDERWATER REMOTE DETECTION AND
MONITORING OF SPILLED ORIMULSION® USING SONAR
In October 1998 flemingCo environmental was retained by Bitor (the company responsible for the production and marketing of Orimulsion) to study the potential use of sonar for the underwater remote detection and monitoring of spilled Orimulsion. Conclusions of a literature study led Bitor in the spring of 1999 to sponsor a small-scale tank test of a spilled Orimulsion underwater remote detection and monitoring system using acoustic means. A 455 kHz multibeam forward-looking sonar was tested.
The results of the test were very encouraging: The sonar detected and monitored the Orimulsion cloud for 45+ minutes after the release of eight liters in a 25 x 5 x 1.5 m (L x W x D) tank with 1.1% salinity water. As 30 % of Orimulsion is water, it was a gradually spreading cloud containing only 5.6 liters of hydrocarbon particles (10-20 micron) which could be observed 17 meters away in a water body of 180,000 liters. Due to the confinement of the tank, causing disturbing tank side- and bottom reflections, the sonar could only be used at 6 % of its full power. It is therefore the expectation that the sonar at full power, in an open water situation, will be operational at a 100 to 200 m range.
Further work is required to develop this technology and discussions and preparations are on-going in this respect. Recent developments in multibeam sonar technology have further added to the feasibility of designing an integrated survey system, providing both cost-effectiveness and reliability of detection. A whole range of commercial-off-the-shelf imaging sonar systems are available, providing various combinations in respect of range, resolution, beam steering capabilities and (digital) raw data acquisition.
It is expected that the sonar detection technology will have similar good potential with regards to the detection of other submerged oils such as LAPIOs (Low API Oils) or in the case of deep sea spills or blow outs.
F. Hvidbak - flemingCo environmental aps
Paul A. Gunter - Bitor Europe Ltd
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