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www.sea-technology.com February 2015 / st 45 A new, real-time water quality monitoring system was deployed in October 2014 in support of INPEX Austra- lia's Ichthys LNG project. INPEX (Perth, Australia) contrac- tor AEC Environmental (Adelaide, Australia) collaborated with Imbros Pty. Ltd. (Moonah, Tasmania) and Soundnine Inc. (Kirkland, Washington) to build and deploy an array of eight data buoys throughout Darwin Harbor. AEC will oper- ate the system for the life of the multiyear project to monitor changes to the predredging baseline water quality within the estuary. AEC and Imbros worked closely to develop a specifca- tion for the data buoys that carefully considered the unique monitoring requirements and environmental conditions of Darwin Harbor, and could be economically sustained long term. Budget objectives were met by leveraging the unique features of Soundnine's (S9) DANTE System with Imbros's own simplifed buoy design, as well as using instrumen- tation that minimized the need for on-site service. The re- sult is a surprisingly affordable, robust and highly capable monitoring system, tailored to the project requirement for high-accuracy measurements and affordable long-term op- eration. Site Challenges The deployment site challenges are signifcant. The large tidal variation, monsoon conditions and remote buoy loca- tions require a robust mooring and buoy system, capable of surviving cyclones. Timely buoy retrieval ahead of or fol- lowing a storm would be impossible. The potential combi- nation of tides and storms creates the real possibility that buoys could be dragged off station by foating debris after rain storms or pulled several meters underwater by storm surge. Imbros engineers and consultants designed the buoy specifcally for the proposed instrument suite and the worst predicted conditions. The buoy structure and mooring were modeled using wind and swell data obtained during Cy- clone Tracy, which devastated Darwin in 1974. The remote mooring sites require satellite telemetry of the real-time data. Each buoy monitors water temperature, conductivity (salinity), pressure, dissolved oxygen, turbidity and pH. The long (90-day) service intervals keep operating costs down, but require sensors able to maintain accuracy in warm surface water conducive to fouling. The completed system reports scientifc-quality data in engineering units directly to the end-users. Automated email alerts are also sent if measurements are out of acceptable ranges, such as in high-turbidity, low-pH or anoxic conditions. System Design The S9 DANTE System enabled a simpler, smaller, less costly buoy design. The modular DANTE components (con- troller, PowerPack and solar panels), with pre-engineered connectivity and small, tightly integrated submersible hous- ings, eliminated the need for a waterproof compartment on New Path to Affordable, High-Accuracy Real-Time Water Quality Monitoring Buoy System Lowers Cost, Allows for Long-Term Deployment By Doug Bennett • Martin Hills Deployment from a small barge using a Hiab-type crane.