The clean-up cost is more than initially expected due largely to difficulties at Ohinemutu where the soft lake bed and ground conditions are making it harder to get to.
Three contractors with equipment needed to remove the weed, plus staff from Castlecorp, have been working non-stop to clear the mess.
One of those contractors, Bill Rigney, got a digger stuck in the lake near St Faith's Church while cleaning up the weed.
"We'd been backwards and forwards on that spot about a dozen times, but there are volcanic soft spots out there, it was my last load of the day, too, and the rocks underneath collapsed."
Mr Rigney said he was bringing in a 100-tonne crane this morning to pull the digger out of the lake in time for Anzac Day.
There were no oil leaks or any other damage, he said.
"The council were pretty keen to get it done before Anzac [Day] so we got down there as soon as we could to do our good deed for the community, but it all turned to custard.
"I've been doing this for them for about 25 years and this is the first time this has happened," Mr Rigney said.