They initially thought that the mewling sounds were a kitten - but then Mr Otte realised that the cries were human.
"I've got two kids of my own so I know what a baby screaming sounds like," he told The Sydney Morning Herald. "It was so intense; you couldn't not tell it was a baby. We couldn't see it but we could hear it. It was distressed."
The drain was covered by a concrete slab which weighed over 200kg and took six people to lift, including two police officers who had arrived at the scene.
'He wanted to get out'
They were then able to extract the baby boy, who was wrapped in a striped hospital blanket covered in dirt with the peg still attached to his cut umbilical cord.
"You go through life seeing things but you never ever imagine you'll see something like this," said Mr Otte, who only cycles the route once a month, said.
"That baby had no chance if we and the other people hadn't been there. Something made us find that baby today. I'm glad we got there to save him. He was very loud and he wanted to get out.'
The boy, who appears to be of Indian or Middle Eastern descent, was lifted out of the drain by Senior-Constable Mark McAlister who climbed in with another officer to retrieve him.
"How could someone do it? I, myself, have kids and we're expecting a baby in a few more months so it's not good that someone's going through this and has done this to a little one," he said.
The incident has left Quakers Hill residents in shock .
Graham Bridges, 44, walked the bike track regularly and said it was usually very popular with riders on a Sunday morning.
He said he saw police gathered on the path as he walked back home. "As I walked passed them, the police asked me if I had seen an Indian looking man around in an orange shirt.
"Usually I walk that way but I used a different path today... because our dog likes chasing after the bikes. It was hot... the baby may not have survived an hour [later]. I'm glad it ended well and that the baby's alive."
There were fears that the baby may have suffered internal injuries after being dumped in the drain, which had a drop of 2.5m.
At a press conference earlier today, police said that he had no signs of outward injuries but that he was malnourished.
Undernourished and dehydrated
"We all thought the worst but the baby was still alive," said Inspector David Lagats, who attended the scene. "Once we found out how far the drop was, we were concerned about the baby's welfare but it was wrapped up pretty well."
He said police were liaising with hospitals to find any record of a baby who was of Indian or Middle Eastern appearance born in the past couple of days matching the description of the one found.
He revealed that some of the cyclists who found him saw an Indian male in an orange shirt walking on the cycle track moments after they heard the baby's cries.
With the mercury set to hit 40 degrees in the area on Sunday, he added that it was lucky that the baby was found quickly.
"The child was already undernourished and dehydration would have taken effect, so we held grave fears for the child's welfare if he was exposed to this weather," he said.
The boy is currently under the care of the NSW Minister for Family and Community Services.
"We are really worried primarily for his welfare and mum's," said Lisa Charet, the department's district director for Western Sydney.
Ms Charet said such an incident was rare but "it does happen" and that the mother must have been desperate to commit such an act.
"It is often fear that stops people coming forward but we are here to help," she said.
