The crews removed three inches of sediment from the river bed , retrieving about 3,500 barrels ( 560 m ) of waste materials over the course of three months .
This amount was estimated as only 1 % of the solid waste spilled .
The crews removed three inches of sediment from the river bed , retrieving about 3,500 barrels ( 560 m ) of waste materials over the course of three months , but this amount was estimated as only 1 % of the solid waste spilled .