Method and system for the remediation of contaminated earth from hazardous substances in a batch-wise ex-situ on site manner. At least one mobile earth moving equipment, at least one mobile tumbler reactor and at least one liquid-solid separator are organized at a location in the proximity of the contaminated site. Contaminated earth portions are collected from the contaminated site batch by batch in the mobile earth moving equipment and transferred to the mobile tumbler reactor at the location. The contaminated earth portions in the mobile tumbler reactor are dosed with cleaning agents and water washed in the reactor under agitation or tumbling. The mixture of water washed earth portions and wash water with cleaning agents transferred into the liquid-solid separator and the wash water with the cleaning agents is separated from the mixture in the separator. The cleaned earth portions in the separator are transferred into the earth moving equipment, transported back to the contaminated site and deposited at th
