Inflatable barrage for Estuary?

Press, Volume CXII, Issue 33052, 20 October 1972, Page 4

Inflatable barrage for Estuary?

If a barrage was built across the Estuary near its outlet, it was possible that it would be of the inflatable rubber type, the Christchurch Drainage Board’s chief engineer (Mr P. J. McWilliam) told the National Water and Soil Conservation Authority during its tour yesterday.

Water would be pumped into the rubber envelope according to the degree of rise wanted, he said. It was, possibly, the ideal type of control, but the board had to give final consideration in the light of the advice it received from consultants. Mr McWilliam was reminded that the sand spit had built up considerably in recent years at the point where the barrage could be built, across from Bay View Road, Redcliffs, and he was asked what guarantee there was that the spit would not again diminish.

“Nature is unpredictable, but whatever the board decides will be reinforced by exhaustive hydrological studies,” said Mr McWilliam. He said there was no estimate of costs — that was for the consultants’ consortium to assess.

Asked who controlled the Estuary, Mr McWilliam said that the Drainage Board was concerned with drainage, the Regional Water Board because the proposals would need a water right, the City Council because of its interests, the Ministry of Works, and the Ministry of Agriculture and Fisheries, as apart

from other questions, there might have to be navigation rights. River pollution Turning to the pollution of the Heathcote River, Mr MeWilliam said that the board had gone a long way towards helping the river to recover. Trade wastes at Woolston now went into the sewer, often at great expense to industry in pre-treatment. One firm would be connected in a fortnight, and there remained only one of importance to take action.

The recovery of the river would be helped by dredging to remove silt and waste matter, and the board had been told that fish were being seen further up the river than had been so for many years. The board also had antipollution by-laws, and regular inspections were made to check on possible sources of pollution. One of the basic jobs was trying to stop pollution from domestic rubbish and garden waste.

“The board must be congratulated on its efforts to overcome pollution,” said the authority’s deputy-chairman (Mr N. T. Gillespie).