INTRODUCTION Hamina, which is close to the Russian border in south-east Finland, is a home port for the oil industry and a transit harbor for timber, cars and other goods on their way to Russia. To provide access for larger vessels it had to deepen the existing channel by two meters to 12 meters and create a new channel section. Terramare Oy, a subsidiary of Royal Boskalis Westminster, won this assignment in late 2008. The project started in July 2009. ENVIRONMENTAL CHALLENGES In the harbor basin, the first step was to remove a contaminated layer of sludge 20 cm deep. The Tributylin contamination was caused in part by fragments of paint from the anti-fouling coating on ship hulls. One of Terramare’s top-class vessels was used to dredge up the sludge: the Kahmari 2, which

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