Pipes for outlet?

Press, 25 November 1980, Page 13

Pipes for outlet?

A permanent system of outlet pipes from Lake Ellesmere to the sea would cost about $3 million to build, according to a consultant engineer specialised in such coastal works.

Mr R. W. Morris told the symposium that the rugged coastline did not make It impossible to build such a system but many precautions would oe needed.

■Mr Morris had studied the possibilities in 1975 and his updated cost estimate was for a 120-metre canal across the/.spit feeding water into five concrete pipes, each 2.4 metres ,in diameter and stretching- about 70 metres into the sea.'- ’ ■„ ?

The pipes would be. supported on piles and would empty, flow from the lake about the low spring tide level.

Mr Morris outlined, an alternative system which was a canal dug down the coastline’ and linking the lake, with the mouth of the Rakaia River. He estimated its cost at $4.33 million.

The pipe; system would provide better control and it would probably need floodgates to ensure the desired rise" and fall of the lake level, Mr Morris said. The pipes; would have to be positioned so that they did not silt up. The maintenance and running costs on a permanent control system would be low if it were properly designed and built, he said.

Asked about possible engineering solutions ,to flooding caused by windlashed water, he . suggested that a series of islands, built up' by dredging, could be placed across Lake Ellesmere in the path of the prevailing southerly wind.