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www.marinelink.com 21 attacks and environmental threats (i.e., pipeline leaks). This usage is aimed at protecting human safety, preventing property damage, and protecting the marine environment. Use of the sonar by the Coast Guard is envisioned as of short duration and within a limited geographic area. For example, it might be used to protect a high-level dignitary during a visit to a waterfront facility. Alternatively, it could be used to examine an offshore facility from which oil is emanating to determine the location and extent of damage or other cause of the discharge so that it can be promptly remedied. At least for now, the Coast Guard in- tends to utilize commercially-available sonar with frequencies above 50 kHz. As a result the capabilities, limitations, and potential adverse effects of equip- ment are reasonably well-known. This, combined with the short duration and limited geographic scope of the sonar use, will serve to minimize any envi- ronmental impact. Further, the Coast Guard proposes to consult with other agencies, such as the Fish and Wildlife Service (FWS) and the National Marine Fisheries Service (NMFS) prior to each planned use in all but emergency situations to determine whether there are particular environ- mental concerns that should be consid- ered, such as endangered species in the vicinity. The Coast Guard also plans to utilize observers to monitor usage and identify any unexpected risks, such as boaters or swimmers approaching the area. The sonar systems under consideration by the Coast Guard operate within the hearing range of toothed whales (150- 180 kHz) and pinnipeds (75 Hz – 75 kHz). Some clupeid fi sh (i.e., herring, shad, sardine, menhaden) may also re- act to these sonar transmissions. Minor adverse impacts could also occur in the unlikely situation if a ROV or UUV were to touch down on seagrass, coral, or sediment. The use of low-power HF and UHF sonar (as opposed to high- power MF military sonar) minimizes adverse environmental impact by re- ducing the area ensonifi ed by the equip- ment. The purpose of the Coast Guard pro- posal is to broaden the agency’s capa- bility to locate and classify underwater threats and other targets of interest and to more safely and effectively accom- plish the Coast Guard missions. Targets of interest could include combat swim- mers or divers; explosives or other of- fensive devices that could be delivered to underwater hulls, piers, or other shore structures; and objects that have become submerged as a result of natu- ral or man-made disaster and have the potential to interrupt maritime transpor- tation, trade, commerce, recreational boating, or other maritime activities. The use of HF (50-999 kHz) and UHF (1,000 kHz and higher) active sonar technology would provide operational commanders with enhanced ability to support maritime security, marine safe- ty, and maritime stewardship with mini- mal impact on the environment. The likelihood of a terrorist attack by divers in US waters is extremely low. More likely are suspicious incidents that require prompt investigation and response, similar to the various pri- vate pilots that negligently stray into restricted airspace around the White House. It is expected that the Coast Guard will more frequently use sonar to investigate suspected contraband stashes affi xed to the underwater hull of incoming vessels, marine casualties, hazards to navigation, and environmen- tal threats. Used properly, sonar can provide the Coast Guard with important new capabilities. MR #1 (18-25).indd 21 1/7/2014 10:24:43 AM
