Paramedics were called to the Lucas Heights Waste Management and Recycling Centre on New Illawarra Road at 3.15pm (AEDT) on Monday.
It’s believed the man was washed into the drain and became trapped as torrential rain lashed parts of the city.
He died at the scene and is believed to have drowned.
“Unfortunately there was nothing we could do,” a NSW Ambulance spokesman told AAP.
The waste management plant is operated by SITA.
It remains unclear if the man was employed at the plant.
The NSW SES have now received just over 220 calls for emergency assistance of which 6 were flood rescues. If you… http://t.co/Tlc3Ts267a
— NSW SES (@NSWSES) March 24, 2014
Earlier, two people were rescued from their cars by the New South Wales State Emergency Service (SES).
The SES is responding to around 60 calls to manage fallen trees and damage to houses.
The people were rescued from their cars at Milperra and Canterbury, with further flash flooding at Mascot, Bankstown and Zetland.
Drivers are being advised to slow down and avoid flooded areas as heavy rain continues to pour.
Wolli Creek in Sydney’s south is flooded and Bexley Road in closed in both directions.
The Bondi-Randwick exit on the Eastern Distributor is also closed at Moore Park.
The SES says the wet weather will continue for the next 48 hours.
More to come.