The clean-up job required along Picton Road is so extensive that will closed for the next two Sunday nights.
The road - along with the M1 Princes Motorway - will be closed this Sunday for vegetation removal, repairing signs, clearing litter among other maintenance work.
The closures will take place between 8pm and 4am, with Picton Road eastbound closing from 7.30pm.
That closure won't give crews enough time to properly clean up Picton Road, so it will close again on November 17 and 18, from 8pm to 4am.
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"Littering is a major problem on Picton Road, and litter thrown from vehicles, or blown off uncovered loads collects along the roadway and in drains where it can cause flooding during heavy rain," Transport for NSW said.
"As the road is near the Cataract Dam catchment area it is very important that we work to keep the area clean and clear of rubbish that might wash into the water supply."
Detours will be via the M1 and Appin Road, while light vehicles can also use Broughton Pass.