R25-million investment announced
PORTNET WILL spend R25-million building a giant sand pipeline for Port Elizabeth harbour.
The port will be the first in the country to replace dredging operations with a sand pumping scheme, and could be a forerunner of similar projects at various other ports, including Durban.
After nearly 40 years of low-maintenance, Port Elizabeth has been faced with a growing silting problem over the past two years since the adjacent King's Beach has grown to the end of the breakwater and the sand is now moving past and gathering near the harbour mouth.
The storage capacity has now reached its limit as the beachline is approaching the edge of the breakwater, says port engineer Sidney Chait.
He says an environmental impact assessment has come up in favour of positioning giant pipes to pump the sand from King's Beach under the harbour and out into the bay.
We considered various options, but this scheme is the most cost-effective as its life expectancy is indefinite, says Chait.
The scheme involves the construction of a fixed jetty at King's Beach using sand embedded jet pumps mounted to it to pump sand from King's Beach updrift to the downdrift coast north of the port.
He says the sand will be transported with an underwater pipeline that runs across the entrance channel to the other side of the port.
The coastline will be brought back by about 60 metres to create sufficient storage for any future storm surges.
This will not only offer a permanent solution to the problem of sand built up at the entrance channel, but will also save dredging costs considerably in the long run, says Chait.
The scheme will cost about R25 million to implement, but dredging costs have increased from R1,7 million last year to R3,5 million this year and will continue to escalate.
The savings of dredging will pay for the sand bypassing scheme in about six years. This scheme has been applied successfully world-wide, says Chait.
Detailed design is already in progress and construction will start early in 1999. It will probably be completed by the end of March 2000, he says.
By Ed Richardson
