Review of potential impacts to sea turtles from underwater explosive removal of offshore structures

• Published in: Environmental impact assessment review 2008-05, Vol.28 (4), p.267-285
• Main Authors: Viada, Stephen T., Hammer, Richard M., Racca, Roberto, Hannay, David, Thompson, M. John, Balcom, Brian J., Phillips, Neal W.
• Format: Article
• Language: English
• Subjects: Acoustic; Animals; Cetacea; CETACEANS; ENDANGERED SPECIES; Environmental impact studies; ENVIRONMENTAL SCIENCES; Explosive removal (severance); EXPLOSIVES; FISHES; GULF OF MEXICO; Impact; INJURIES; Mammals; Marine; Marine mammal; Methodology; METHYL METHANESULFONATE; Offshore structures; Sea turtle; Surveys; TURTLES; UNDERWATER; UNDERWATER EXPLOSIONS; Water
• ISSN: 0195-9255; 1873-6432
• DOI: 10.1016/j.eiar.2007.05.010

The purpose of this study was to collect and synthesize existing information relevant to the explosive removal of offshore structures (EROS) in aquatic environments. Data sources were organized and summarized by topic — explosive removal methods, physics of underwater explosions, sea turtle resources, documented impacts to sea turtles, and mitigation of effects. Information was gathered via electronic database searches and literature source review. Bulk explosive charges are the most commonly used technique in EROS. While the physical principles of underwater detonations and the propagation of pressure and acoustic waves are well understood, there are significant gaps in the application of this knowledge. Impacts to sea turtles from explosive removal operations may range from non-injurious effects (e.g. acoustic annoyance; mild tactile detection or physical discomfort) to varying levels of injury (i.e. non-lethal and lethal injuries). Very little information exists regarding the impacts of underwater explosions on sea turtles. Effects of explosions on turtles often must be inferred from documented effects to other vertebrates with lungs or other gas-containing organs, such as mammals and most fishes. However, a cautious approach should be used when determining impacts to sea turtles based on extrapolations from other vertebrates. The discovery of beached sea turtles and bottlenose dolphins following an explosive platform removal event in 1986 prompted the initiation of formal consultation between the U.S. Department of the Interior, Minerals Management Service (MMS) and the National Marine Fisheries Service (NMFS), authorized through the Endangered Species Act Section 7, to determine a mechanism to minimize potential impacts to listed species. The initial consultation resulted in a requirement for oil and gas companies to obtain a permit (through separate consultations on a case-by-case basis) prior to using explosives in Federal waters. Because many offshore structure removal operations are similar, a “generic” Incidental Take Statement was established by the NMFS that describes requirements to protect sea turtles when an operator's individual charge weights did not exceed 50 lb (23 kg). Requirements associated with the Incidental Take Permit were revised in 2003 and 2006 to accommodate advances in explosive charge technologies, removals of structures in deeper waters, and adequate protection of deep water marine mammal species in Gulf of Mexico waters. G