Deluge threat to drains

PAUL GORMAN

Last updated 05:00 05/04/2011

http://www.stuff.co.nz/the-press/news/christchurch/4847225/Deluge-threat-to-drains

Cold, wet weather this week will put pressure on Christchurch's broken sewerage system and add to the misery of those living in quake-damaged homes.

Civil Defence and the MetService are warning a change to wintry weather will severely test the wastewater network, with more than 20 millimetres of rain likely by the weekend.

Christchurch City Council water and waste manager Mark Christison has issued a plea for residents to conserve water over the next few days.

"The water that goes down your drain is leaking into the wastewater network through broken pipes," he said. "This is putting extra pressure on the system and on the Christchurch wastewater treatment plant, which was significantly damaged during the earthquake."

Broken sewerage systems could not cope with large volumes of wastewater and the more water used, the more raw sewage would be flushed into the city's rivers, the Avon-Heathcote Estuary and the ocean.

Residents needed to conserve water by: Having quick showers.

Only flushing solid waste down the toilet.

Using chemical toilets or portable toilets in the eastern suburbs, even if household toilets are flushing.

Only using washing machines and dishwashers when full.

Civil Defence and council staff were "working around the clock" to repair the sewerage network and there was still a long way to go, he said.

The main concern was significant damage to the treatment plant.

"If the oxidation ponds cannot cope with the extra load, they will start to smell," Christison said.

MetService severe weather forecaster Andy Downs said five-day rainfall forecasts were being provided to Civil Defence so it could prepare for increased pressure on the wastewater system.

Up to 15mm of rain was likely by this morning, followed by blustery showers today before it cleared.

Tomorrow would provide some respite before more cold southerlies and showers blew in on Thursday and Friday.

"It's really going to cool off," Downs said.

"Until now the weather gods have been relatively kind to you.

"Despite the odd outbreak it hasn't been particularly cold or wet, but you are in for quite a spell.

"By the weekend the ridge [of high pressure] will be building, the winds going a bit more westerly, so at least for the weekend it should be a nice spell of fine weather."