The Olympic Delivery Authority has started preparing the waterways in east London to take barges.
A 60-tonne craft has started dredging a 2.2km stretch of water from Bow Locks on Bow Creek to the Waterworks River, adjacent to the site of the Aquatics Centre.
The craft is expected to remove 30,000 tonnes of silt, gravel and rubble as well as tyres, shopping trolleys, timber and at least one motor car.
ODA environment manager Richard Jackson said: “The Olympic Park is characterised by a series of waterways which act as green corridors running through the heart of the site. Currently, they are polluted, neglected and under-used, and have been treated as a dumping ground for everything from shopping trolleys to cars.
“This dredging programme is an important step in regenerating the waterways and will help improve water quality, creating better habitats for wildlife and plants.
The clearing and cleaning of the waterways will enable freight barges to carry construction materials in, and waste out, of the park during the construction phase.
A wharf is being constructed on the WaterworksRivernear the Aquatics Centre and will be used to receive freight loads for the Olympic Park contractors.
Work began on the upper levels of the wharf this week and is due to be completed at the start of June.
Barges will then be able to travel into the Park by water via the new lock and water control structure, Three Mills Lock, at Prescott Channel. The £20 million structure comprises twin water control gates, a 62m-long tidal lock, footbridge, lock control building, fish pass and fixed weir.