Summaries
Gates and operating mechanisms for the
Oosterschelde barrier
The final design of the barrier-gates comprises
a bridge girder made of tubular sections,
considered to be the best to withstand wave-
attacks. Each gate can be raised or lowered by
hydraulic operating mechanisms, which are
installed on both sides of each gate. These
operating mechanisms must meet the highest
demands for accuracy and durability. The
piston-rod presented a major problem, as this
mechanical part will be continuously exposed
to corrosion by sea-water when the gate is
closed. After many tests, it was decided to use
a coating of nickel and chromium to protect the
piston-rod. In addition, every time that it is
extended the rod will pass through a lubricant.
Using the storm-surge barrier in the
Oosterschelde estuary for other purposes; a
first reconnaissance
The primary goal of the Oosterschelde barrier,
presently being built in the estuary, is to
protect the hinterland. Due to its particular
design it will be possible to preserve both the
natural values and the fishing industries. It may
well be possible, however, to use the barrier
for other purposes too, provided these are not
incompatible with the primary goal i.e. the
safety of the land.
In a recently published memorandum these
possible purposes are summed up and their
effects on the Oosterschelde area investigated.
An example of this is the usage of the Ooster
schelde barrier for the protection of oysters
during easterly storms.
The Minister responsible will ultimately have to
decide whether the barrier may be used for
such secondary purposes.
The research and working-vessel 'Lodycke'
The Measuring Services, which have to provide
intensive operational assistance during the
construction of the Oosterschelde barrier,
needed to expand and replace their existing
fleet of measuring vessels. The recently built
m.s. 'Lodycke' can serve not only as a measuring
vessel but also as a working-vessel; e.g. to
shift anchors. This is particularly important as,
in orderto prevent damaging the bed-protection
along the alignment of the barrier, normal
anchoring methods cannot be permitted. The
'Lodycke' is therefore fitted with special
anchors i.e. concrete mooring sinkers and truss
anchors, to which the measuring equipment on
board can be attached. The vessel is also
equipped to lower or hoist aboard survey
vehicles such as the bottom crawler.
Lake Grevelingen, salt or fresh?
Lake Grevelingen, which, at present is nearly as
saline as the North Sea, could be turned into a
fresh water lake in the future. A number of
working groups is presently investigating
whether this would be preferable.
This article provides a condensed report
regarding the consequences for the
watermanagement and the water-quality, if the
Grevelingen would become a fresh water body.
A fresh water Lake Grevelingen will have to be
fed bij the river Rhine, the water of which is
highly polluted with nutrients and heavy
metals, whereas in a saline Lake Grevelingen a
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