Around 18 tonnes of rubbish including stacks of dumped tyres were cleared up by TV presenter Mel Giedroyc and other volunteers.
Two volunteer groups - the Litter Action Group for Ealing Residents and Clean Up the River Brent (CURB) - spent over three weekends clearing out rubbish in the River Brent.
The crews gathered at the Abbey Estate Open Space in Alperton and found various fly-tipped items over a combined 310 hours of work.
Many of the items were removed frmo steep banks leading down to the river, which runs along the Brent and Ealing boundary.
Ben Morris, from CURB, called the collection of rubbish an "eyesore".
He said: "It was fly-tipped and casually littered over many years, with rubbish embedded in the banks and tumbling down into the river.
"It now looks acceptable and normal. It’s still not perfect, and we hope to go back for one final effort before Brent Council put up a new fence."
According to the groups, the tyres were dumped "over a number of years" at the site off Queensbury Road.
Cathy Swift, chair of Ealing-based LAGER Can, said: "We knew that the rubbish in Alperton would eventually work its way down to Ealing, so we felt it was as much our problem as if it had been in the river in Ealing.
"Rubbish is no respecter of borough boundaries."
The Bake Off presenter, who was among the volunteers said that she loved rolling her sleeves and "getting stuck in".
Alperton Lib Dem councillor Anton Georgiou said: "The heroic efforts of the volunteers have totally transformed the River Brent banks here. I cannot understate the improvement.
"Unfortunately, uncertainty over land ownership and responsibility, as is often the case, meant that rubbish was allowed to build up over a long period.
"Now that volunteers have done such an incredible job, it is essential that rubbish is never allowed to build up in this way again."
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