24 June, 2013

Attempts to open lake hampered by conditions

Hazardous conditions over the last week prevented Environment Canterbury from opening Lake Ellesmere/ Te Waihora, however, workers have been able to access the designated opening site this morning. Preliminary earthworks are underway.

“The site is marked out, machinery is now on site and earthworks have begun,” says Leigh Skerten, Senior Engineering Advisor at Environment Canterbury. “But given the current large swell, it is unlikely a full opening or connection to the sea will be able to be made today.”

Lake Ellesmere/ Te Waihora is at a very high level – 1.74m at the Taumutu end this morning – levels have not been this high since 1941.

“The flooding around the lower lake catchment is extensive and we appreciate that this is having a significant effect on many in the area. We understand it’s a stressful time and we are doing all we can to relieve the situation.

“The lake wasn’t able to be opened over the last week due to extremely large southerly swell at the opening site. Waves were overtopping Kaitorete Spit into the lake making access to the opening site impossible. Any works attempted in those conditions would have risked human life and would probably have been unsuccessful. “

Extra machinery is being moved to the site to speed up earthworks. An attempt will be made as soon as weather and sea conditions allow.

“Opening a channel from the lake to the sea can be a lengthy process at times,” explains Ms Skerten. “Given the current conditions successfully completing the channel could take at least 2-3 days.

“The site of the opening is also extremely hazardous and we strongly suggest to anybody wishing to observe operations stay well away from the construction site.”

Ms Skerten adds that the river channel, Halswell drainage system, and adjoining ponding areas are full to capacity. These areas are beginning to drain and without further significant rainfall and a successful Lake opening, this should continue over the coming week. The Halswell River which feeds into the lake peaked early Sunday morning at levels not seen since 1977.

Anyone that goes down to the opening site does so at their own risk; it is a health and safety controlled area and media are advised to not attempt access to the site.

The lake is opened by cutting a pilot channel of 15 metres wide and 1.8 metres deep through the beach with bulldozers. It can take two plus days on the first attempt to open the lake and it can take multiple attempts.

During this time the lake will continue to rise. The length of the channel can vary from 100 to 300 metres. The sea will close the artificial channel again.

A National Water Conservation Order set levels at which the lake may be opened.

ENDS

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