By WAYNE THOMPSON
When the heavy rain woke them at midnight, North Shore City officials thought they might be in for a busy day. By 3 am they knew it. The country's fourth-largest city was again at the mercy of rainstorms.
The council's 24-hour call centre, Actionline, fielded 3400 calls on the morning of June 29 after 90mm of rain fell - 50mm of it in just one hour.
Residents complained about blocked drains, flooded house basements and swollen streams disgorging raw sewage on to beaches.
East Coast Bays fire crews took 20 calls for help from 2.50 am and civil defence volunteers and engineers turned out from 4 am to inspect 150 house floods.
Welfare teams were on stand-by for distressed residents.
For up to 12 hours after the storm, raw sewage oozed from popped manholes, and a third of the 86 coastal and suburban pumping stations that feed the wastewater treatment plant in Albany.
The plant's oxidation ponds, known as Lake Rosedale, were 200mm above normal. But the plant management had heeded the weather forecast and lowered pond levels to give more storage.
The dam-like banks held firm and plant officials did not use the emergency spillway into the Oteha Stream, which enters the Upper Waitemata Harbour.
But by Monday the spillway option, with its danger to wildlife, was again at the back of staff minds.
The plant was receiving four times its normal flow.
There was 33mm of rain on Friday; 42mm on Saturday and 32mm on Sunday.
More than 20 pumping stations overflowed and 14 beaches were closed to bathers as a health precaution.
Treatment plant manager Steve Singleton reported that the ponds were within 180 mm of spilling.
A spill last occurred in 1964. Triggering the spillway was considered after the severe storms of July 1998, but the council chose instead to switch off six coastal pumping stations.
This eased the pressure but caused illegal discharges of raw sewage from the stations into the stormwater flowing into the Rangitoto Channel.
Last Monday's emergency dissolved when the rain obligingly stopped, reducing flows into the plant and giving it a chance to catch up.
The experience showed the harm done by the city's network of leaky sewer pipes, and illegal connections by householders to get rid of their stormwater and swimming pool surplus.
The council's spokesman on water issues, councillor Joel Cayford, said yesterday that although Monday was fine, the plant's effluent inflow was three times greater than the rate on a normal fine day.
This was because the water table had risen and covered the pipe network.
Groundwater was getting into leaky pipes and heading for the treatment plant.
Dr Cayford said that in such conditions, as soon as it started to rain, the sewage pumping stations overflowed and 24 hours later the plant got higher volumes of effluent.
The option of fixing the problem of a 1200km network of pipes was an expensive one in the council's Project Care programme, Dr Cayford said.
But the council's policy was to "get the best environment for its bucks."
The council plans to spend $9 million on the wastewater network this year, including installing a holding tank -about the size of seven Olympic swimming pools - at Wairau.
Project Care aims to improve beach quality over 10 to 20 years. It could cost between $80 million and $260 million, depending on which options the community favours during the present consultation exercise.
The council's director of water services, Geoff Mason, said that, put simply, the community was being asked to choose how much more they were willing to pay to have more days when they could safely swim at the beaches.
While plans for Project Care and a $180 million upgrade and expansion of the treatment plant are on the boil, Mr Mason said the city's stormwater improvement programme was not well-advanced.
He said stormwater was a big contributor to beach closures and not much was known about the effects on public health of contaminants carried in the water.
About $1.6 million is being spent this year on improving the quality of stormwater discharged on to the beaches. Methods include setting up "treatment trains" - a series of ponds and wetlands to filter out pollutants.
The council says about $2 million needs to be spent in each of the next 20 years to address the problem.
Recent rain highlights fragile wastewater system
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