Cabling and mooring a remotely operated ADCP for real-time data acquisition

Abstract

As part of a joint U.S. Army Corps of Engineers, Port of Miami, State of Florida, U.S. EPA, University of Miami (Rosenstiel School), National Oceanic and Atmospheric administration (NOAA) offshore dredged material disposal program, a real time current monitoring system (RTCMS) was designed by the Ocean Acoustics Division (OAD) of the Atlantic Oceanographic and Meteorological Laboratory (NOAA/AOML) for deployment offshore of Miami. This system consists of an acoustic Doppler current profiler (ADCP) moored on the ocean floor at a point southwest of the Offshore Dredge Material Disposal Site (ODMDS) and cabled to a near shore site. The near shore site chosen was a range marker at the Miami harbor entrance. From the range marker the data is transmitted via radio modem to the NOAA/AOML/OAD offices on Virginia Key. The high current regime and the requirement for periodic maintenance of the ADCP added unique challenges to the design of the cable and mooring system. Cable selection and routing was performed so as to minimize risk of damage due to recreational activities. For purposes of deployment and serviceability, the cabling and mooring system was divided into three sections. The first section extends from the range marker to a common point in 60 feet of water. The cable was laid and anchored in sandy areas where possible in order to avoid reef impact. The second section connects the common point to the first mooring point at a depth of 400 feet. The final section couples the first mooring point to the ADCP mooring point The ADCP mooring section consists of a two point moor with a subsurface center float to suspend the cable above the bottom. The deployment of the system was accomplished in two days on board a ninety five foot research vessel equipped with a stern mounted A-frame and deck winches. Divers were utilized to attach the cable to anchors in the shallow water sections, and to inspect the cable after installation.