American Civil Contractors contacted Fugro Seacore back in 2006 to come up with a solution for a project in DutchHarbour, Unalaska for a new highway bridge. The challenge was to insert 4 No. 108 inch casings through layers of large glacial tilth 18-20’ deep, and then to drill a 102 inch diameter, 32 foot deep socket into very hard Alaskan Andesite, measuring 80-150 mpa. Added to the difficulties of the unforgiving ground conditions were the sloping bedrock levels (up to 40° ) which were constantly trying to kick out the toe of the casings.
The equipment was mobilised to Seattle in the USA where it was loaded onto a barge and towed to Unalaska. Work started at the end of July and FSCL managed to drill the sockets in 15-20 hours, utilising the Company’s Teredo 40-4 drill rig and extensive drilling experience to seat casings into the bedrock, ready for local contractors to insert 120 ton rebar cages into the sockets and then concrete them up for foundations. All the piles were installed and concreted by mid September and equipment shipped out before the winter set in.