Submarine blasting at Palmer Station, Antarctica

During June and July 1999 a United States Antarctic Program (USAP) team of three commercial divers and one blaster successfully removed an underwater rock obstruction which interfered with safe docking practices of research vessels that call at Palmer Station - the USAP research facility located on Anvers Island, Palmer Peninsula Area, Antarctica. Ordinarily, such a project might be considered routine. However, certain aspects of the project, particularly those dealing with logistics in a remote corner of the earth, safeguards for marine biota, and working underwater in the dark of the austral winter, conspired to make this project interesting Even more challenging was ensuring the protection of the existing pier - a deeply corroded sheet pile structure backfilled with loose gravel and rock - which lay less than 50 feet away from the target obstruction, not to mention uncertainties at the outset as to the nature of the rock mass forming that obstruction. The rock removal team spent a number of the early dives assessing the target mass, and establishing survey control on the seafloor to guide the project. Early test blasting at the site - monitored by commercial blasting hydrophones - established the underwater shock wave and seafloor blast reflection characteristics. These in turn established not-to-exceed values for charge weights and shot distances - both for protection of the pier and of marine biota. Finally, an air-bubble curtain device employed for additional pier protection indicated 70% effective reduction of the peak underwater shock wave. This paper presents a description of the project operations and its results. Topics include: Background Planning and Logistics On Site Target Assessment Development of an Effective Bubble Curtain, Test Blasting Diving and Blasting Operations, Blast Effects Project Conclusion.