This environmental impact assessment for Kriegers flak ... - Vattenfall

16.3 The effects on the environment
and the consequences thereof
16.3.1 The Construction Phase
16.3.1.1 The Sea
Temporarily, the water will become cloudy and the
sediments will be affected in connection with the
laying of cables and construction of the transformer
stations.
As mentioned earlier, the cables will be placed
under the seabed by washing, plowing or digging. In
all cases, a temporary clouding of the water will occur.
The extent of the spread of sediment is dependant on
the nature of the bottom and currents.
Were digging will occur (nearest to the coast) the
shifted material will be put back and where plowing
and washing will occur, the softened material will
be put back in the cable shaft. A reasonable view is
that within a year or two the seabed will return to its
natural state.
When the seabed material has been put back, the
water will become clear again.
During the construction of the transformer stations,
physical impact will occur similar to that accounted for
in Chapters 5.7.1.1. and 5.7.1.2.
As a relatively insigniÞ cant and temporary clouding
of the water will occur, the impact on ß ora and fauna
will be negligible.
The stationary ß ora and fauna existing in the area
where washing/digging will occur (or piling/drilling
for the foundations of the transformer stations), will
be damaged or suffer from severely changed living
conditions. The algae will in this area be torn up and
drift away. Benthic animals will be exposed and may
possibly move to other habitats.
Fish will look for food among the uncovered organisms.
During the construction phase, increased trafÞ c
will occur in the area where the cable is laid. This will
affect both commercial shipping and Þ shing. As this
disturbance is limited in time, the negative effects will
be small.
16.3.1.2 Land
As the cable laying mainly will occur across cultivated
land, only a temporary impact on the land use will oc-
CABLE LAYING 167
cur. Crops will be damaged and there will be a certain
impact on the use of land during the work, especially
during wet weather. Crossing drainage must be dug
that will be damaged but repaired when the work has
Þ nished and the area been restored.
The cable laying has been planned so that protection
worthy environments and objects will be avoided. The
construction may hit upon unknown ancient remains,
but this will be dealt with in accordance with the
Swedish National Heritage Law. The impact on animals
and humans is judged as negligible as the activity
can be compared to conventional light entrepreneurial
activities. Noise limits will be in accordance with the
rules of the Swedish Environmental Protection agency.
16.3.2 The Operating Phase
16.3.2.1 The Sea
The cables will cause a magnetic Þ eld with a strength
of 3.5 µT at maximum use. As a comparison, it could
be mentioned that a vacuum cleaner and an electric
drill at a distance of 30 cm would generate a magnetic
Þ eld corresponding to 20 µT and a TV set 5 µT. The
magnetic Þ eld generated by the cable would decline
rapidly with the distance and end at a distance of 20
metres, see picture below. Left then will be the natural
magnetic Þ eld of the earth measuring 50 µT.
No electric Þ elds will occur as the cables will be
screened.
On the other hand, a secondary electric Þ eld will be
generated. This Þ eld is, however, very faint and will be
of no consequence.
The cables generate heat and calculations have been
made in order to Þ nd out whether the cables would
generate any signiÞ cant heat. During these calculations,
a worst scenario of maximum output and summer
temperature of the water were used. The result
showed no signiÞ cant increase in temperature of the
seabed.
16.3.2.2 Land
After the construction area has been restored, the land
can again be used as before. The cables will generate
some heat but this will have no negative impact on
the surroundings. Maintenance and supervision will
in principle only take place during digging activities
around the cables or when a fault has been reported.