Environmental
impact associated with the dumping of dredged material at sea. A study for the Limassol port extension works
A.D.
Toumazis
Dion
Toumazis and Associates, Architects and Consulting Engineers, 4 Romanos Street, 1070 Nicosia, Cyprus
Water Science
and Technology,
Volume 32, Issues 9–10, 1995, Pages
151–158, Elsevier
Pollution
of the Mediterranean Sea, Selected Proceedings of the International Symposium
on Pollution of the
Abstract
The
construction of major marine works is frequently associated with the need to
relocate large quantities of material. Relocation at sea is associated with a
number of environmental impacts. For non-contaminated silty/clay
material main environmental effects include blanketing of the sea bed and
increase in turbidity, or reduction in the clarity of water.
Blanketing
of the sea bed has a harmful effect on the marine life whose ability to recolonise the new material is doubtful. The importance of
marine life can be evaluated in relation to the number of species and specimens
living on the sea bed. Measurements reveal that there is a reduction in the
number of species with increase in depth. The dumped material that covers the
sea bed, and therefore affects adversely the marine life, has less impact the
greater the water depth.
The
increase in turbidity, associated with the suspended soil material in the
water, although temporary, 11 nevertheless has a potential impact on the
tourist industry. Places which are popular with tourists because of the clarity
of their waters, might have adverse publicity if the
turbidity increases to noticeable levels. Turbidity levels depend on the
current direction and speed, the rate of mixing (dispersion coefficient), the
size and density of the dumped material and the method of dredging and
disposal. Predictions of expected turbidity levels can not therefore be made
with accuracy or great confidence if the above parameters are not well known.
Sensitivity analyses can however be made in order to predict the range of
values of the expected turbidity levels.
The
impact on marine life and the increase of turbidity can be reduced by dumping
the dredged material in deep water and at great distance from bathing beaches.
This measure is associated with adverse financial implications. The optimum
relocation site is one at which the total cost of both the environmental damage
and the relocation cost is minimum.