The contractor OpenIJ has finally sunk a 150,000-tonne concrete caisson at the troubled project for the world’s largest sea lock in IJmuiden, Netherlands. A need to reinforce the 81-meter-long, 55-m-wide and 28-m-tall caisson design contributed to more than $222 million in cost overruns by OpenIJ, an equal joint venture of BAM Infra and VolkerWessels. It had been aiming for a 2019 completion of the $668-million contract at its 2016 start, but OpenIJ now expects the 500-m-long, 70-m-wide, 18-m-deep lock to be operational in 2022.