Painters turned up at Melbourne's Bolte Bridge on Thursday morning as they began the sky-high job of abseiling down the pylon to cover up the vandalism.
Serial prankster and alleged vandal Jack Gibson-Burrell is accused of the July 7 paint job after he allegedly scaled the bridge to spray paint his infamous giant cartoon bird.
The graffiti covers about 200 sq m of the bridge pylon, which is roughly the area size of a typical family home, Transurban general manager of road operations Peter Munro said.
"It's a big job ... It'll go for a couple of days," he told ABC radio.
It will take workers about 40 minutes to climb up the pylon's internal stairs with their equipment to paint over the graffiti.
"Given it's over the top of the Yarra River, it wasn't an option to clean it off," Mr Munro said.
Painters applied a "primer coat" on Thursday to ensure the graffiti doesn't come through before returning over several days to apply the final paint coatings.
Transurban, which operates the bridge, confirmed taxpayers won't bear a single cent of the clean up cost, with the company footing the six-figure bill.
But motorists could face some minor disruptions as a single inbound lane is closed for the remedial works until Sunday.
Some in the community have objected to the clean up, with a GetUp petition calling for authorities to keep Pam the Bird on the bridge garnering more than 9500 signatures.
"While graffiti is often associated with vandalism, every now and then something appears that transcends a simple spray can on concrete," organiser Eric Giodmaina said.
"Pam the Bird has quickly become one of those rare pieces."
But Mr Munro said the road is part of Melbourne's critical infrastructure, and it was Transurban's role to make sure it was clean and free from graffiti.
Swinburne graffiti expert Stephen Glackin said highly visible graffiti that remains in place sends a clear signal to other graffiti taggers that a location is worth targeting.
Keeping Pam on the bridge could not only lead to more graffiti across Melbourne's transport network, but also riskier attempts from copycats, he said.
The alleged stunt, which began at 2am, morphed into an almost nine-hour stand-off with police, causing peak-hour traffic chaos.
Gibson-Burrell has been charged with criminal damage, conduct endangering life and graffiti-related offences among others.
During the stand-off, the accused vandal shared social media videos from atop the pillar demanding taxes be lowered and a peanut butter sandwich and glass of milk.
At one point, he abseiled down the pillar and taunted police and media below with a wave before returning to the top.
The bird cartoon has been graffitied across Melbourne for years, often on hard-to-reach places and heritage-listed buildings.
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