“We dredged round the clock, 7 days a week”, says Works Manager Kleo Danau. “This means that planning was crucial. Every vessel had to keep the others permanently informed. That was not always easy, internet or phone connections sometimes…Read more
Another challenge of the Sabetta project was the amount of permafrost that had to be dredged. Because dredging works in the high North are very rare, this was a first for our company.
Permafrost is frozen soil that never thaws, in this case mainly frozen sand. Pieter Timmermans explains the corresponding challenge: “That soil is harder and thus production is lower. Anyway, we needed a cutter suction dredger for dredging the permafrost; this is a dredger with cutting teeth cutting and crushing the soil before sucking it in. The harder the soil, the sooner these cutting teeth will wear off and the sooner we will have to replace them. This makes the whole process more expensive. As such, it was important for us to pre-assess the percentage of soil that would be permafrost.
The estimated volumes were based on drilling tests performed in 2013 and indicated that the first 15 metre would be permafrost followed by softer soil. But these drillings were executed before the first dredging works. Because of the dredging works executed in the past few years, part of the permafrost had already made contact with seawater. As a result, the soil had already softened a bit in some places, which made dredging there easier.”