Down-the-hole drilling construction acoustic research

nd The Alaska Department of Transportation and Public Faculties (DOT&PF) is conducting research to characterize underwater sounds from down-the-hole (DTH) drilling activities. This method of drilling is commonly used to drill holes through hard or rock substrates to support piles or tensions anchors for piles. A pneumatic DTH hammer is driven by pressured air coming from an air compressor that provides the energy to power the percussion piston that hits the drill bit with a specific impact frequency and energy to break the rock and advanced the hole. This activity produces continuous and impulsive sounds that affect marine mammals. Pile installation in marine environments typically uses vibratory drivers and/or impact pile driving. Underwater sounds from these activities have been well documented in publications, for example, there are compendiums prepared by Caltrans, and the U.S. Navy, along with many project-specific compliance reports submitted to resource agencies. However, there is limited acoustical data available for DTH activities, as the first published measurements were only made recently. The National Marine Fisheries Services (NMFS) recognizes the acoustical issues with DTH noise and is encouraging the collection and dissemination of additional sound data. This paper describes the research conducted and available DTH acoustic data.