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www.sea-technology.com March 2015 / st 21 charging effciency of the system; and moorings should be checked every six months and replaced as required, de- pending on local conditions. It is also advisable to install a GPS locator on the buoy(s). This can allow the operators to double check that the buoy is in the correct position, but can also allow for location and recov- ery of the buoy in the unlikely event of a mooring failure, or if a buoy and its mooring become entangled with a passing vessel and dragged to a new location, which can be a problem in busy waterways, such as the Thames Estuary. Regular checks and mainte- nance for all systems should ensure that dredging uptime of 98 percent is consistently achievable. Data Reporting The data collected are often used proactively during the project by the dredge operator to manage the water quality levels in order to utilize dredg- ing time to full effciency. To be ef- fective, measurement data should be provided to the operator in real time. In most instances, the easiest and most effcient way to do this is with buoy- based monitoring systems. This system can then securely transmit the data to the dredge operator in real time (at regular intervals, often every 10 min- utes), to ensure that the pre-established threshold limits are not exceeded and allow the operators to make adjust- ments to the dredging program or vessel movements as required. Most commonly, telemetry is via satellite or cellular networks, but can also be via radio. The telemetry system used must be well-planned. Overloading of cel- lular networks at peak times has been known to interrupt communications, and network coverage in the correct areas is critical. Line of sight is essen- tial for radio telemetry, and large ves- sels moving within the dredged area may obstruct communications. Satel- lite is arguably the most reliable form of communication, but can be very costly. OSIL buoy systems are fexible and are customized to the specifc project and client requirements, but usually comprise a rugged hull and mooring system, with a high-visibility top frame holding solar panels, electronics and telemetry equipment. They can house as many sensors as needed (at mul- tiple depths to provide more compre- hensive data), and all equipment is powered via a marine battery and re- charging solar panel system. Continu- ous real-time data can be reported to operators directly to a single computer or network, or via a secure website for access from any Internet-ready device (i.e., tablets and smartphones) or by multiple users, with various alarms in place to warn when limits are being, or are close to being, surpassed. Careful planning of telemetry and data report- ing systems ensures that the dredging operations progress smoothly, and any control measures can be implemented immediately if parameter limits are ex- ceeded. Conclusion By undertaking extensive dedicated specialist monitoring, coupled with live data being supplied to dredge ves- sels, the dredge contractor is better able to monitor the dredge and there- fore operate the dredge in the most effcient and compliant way possible in terms of vessel movement and sedi- ment disposal with minimal environ- mental impact. n Dr. Richard Williams has been the managing di- rector of OSIL for the past eight years. During this time, OSIL has been established as a leader in spe- cialist monitoring and sampling platforms and has successfully developed a range of dedicated data buoys and a variety of sediment corers, including the 42-meter Giant Piston Corer. Becky Childs joined OSIL in 2010 as a client sup- port specialist and has proved a valuable asset to the company, now fulflling the role of technical services manager. "Careful planning of telemetry and data reporting systems ensures that the dredging operations progress smoothly, and any control measures can be implemented immediately if parameter limits are exceeded."