The stormwater pipe where Aisling Symes died was decades old and never designed to service infill housing.
An inquest into her death heard yesterday how the 2-year-old fell down a manhole on October 5, 2009.
Evidence showed it was likely that water pressure popped the manhole cover off while Aisling's mother, Angela Symes, was cleaning out the home of her late parents.
Seven days later, Aisling's body was found 36m down the stormwater pipe.
The former Waitakere City Council had received complaints about the drain.
Council water services manager Richard Taylor said the pipe was built in the 1970s and was designed only to drain the roads.
Mr Taylor said the drain network that Aisling fell into was on a low priority for replacing.
"We didn't appreciate the risk of a toddler falling into a manhole, so it was off the radar."
Housing New Zealand asset manager Sandra Bond said she called the council in 2008 and told staff the manhole cover was lifting. She phoned them again a year later because the problem had not been fixed.
"I did believe there was a risk of a child standing on the manhole cover.
"I said: 'Every time the manhole cover pops off, we potentially have a situation there because we have young children there and the manhole cover is easily accessible on the driveway'."
Coroner Garry Evans asked Ms Bond what Housing NZ did when it received complaints about the manhole cover popping.
She replied that the stormwater drain belonged to the council. "Beyond ringing the council - nothing, to my knowledge."
In 2009 - a month before Aisling died - the council sent out a contractor to run a CCTV camera along the drain.
William Ihimaera managed the job for council contractor BBS.
He said they found tree roots blocking the pipe and decided to flush the line.
Coroner Evans asked Mr Ihimaera if he was aware at the time that, with further rain, the manhole lid would continue to pop out.
"Did you ask yourself, 'In the meanwhile, should we put in a grill or net?"'
Mr Ihimaera said he did not ask himself that question.
He said nowadays a 200-litre drum full of water is placed over a manhole until a steel grid can be fitted.
His boss Robert Coe said his company relied on the council engineers to direct what work got done and when. He said that following the Aisling tragedy, his firm's CCTV crews could directly communicate with the council.
Mr Coe said his company now alerted police to any drain work in the vicinity of a search and rescue operation.
Aisling inquest: council under fire
Aisling Symes. Photo / Supplied
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