Annual r eport 2002 Annual r eport 2002 - Boskalis

Left Paul van der Burg, specialist submerged tunnels &
special survey applications and right Jan de Reus, director
Heinrich Hirdes.
Rostock tunnel project:
innovative approach
In the German harbor of Rostock, Boskalis
subsidiary Heinrich Hirdes is involved in the
building of a tunnel under the river Warnow. The
remarkably low weight of the tunnel elements
demands an integrated approach to the work. No
separate links, but a connected chain of work.
“The nice thing about the Rostock tunnel is that we
are involved in the project from A to Z, and not just
in a part of it”, says Paul van der Burg, a specialist
in submerged tunnels & special survey applications.
Heinrich Hirdes did all the dredging work using its
own equipment and people. A joint venture was
established with the German subsidiary of Van
Hattum en Blankevoort for the immersion of the
six tunnel elements. “A real ‘home market project’”,
says Heinrich Hirdes director Jan de Reus.
“Because the concrete tunnel elements are relatively
light, there was a risk that they might float upwards
during and after immersion. To make sure that didn’t
happen, ballast tanks in the elements were filled up
to the top with water. In addition, the immersion of
the tunnel elements and all the ground and dredging
work involved was dealt with as a single integrated
process. That needed well-planned logistics and
considerable precision in the implementation of the
work,” continues Jan de Reus.
The design of the armor on the roof of the tunnel also
required precise calculations for another reason,
namely the fact that the depth of the fairway had
to be maintained. So Heinrich Hirdes talked to the
number crunchers at Boskalis’ engineering consultancy
Hydronamic. In the spring of 2003, the layer
of stones that they have worked out as anchor
protection will be positioned on top of the tunnel.
70 Annual Report 2002