But finding a disposal or temporary storage site will be a tall order.
The estimate covers soil and dead leaves mainly from areas with radiation levels of more than 5 millisieverts per year in the prefectures of Fukushima, Miyagi, Yamagata, Tochigi and Ibaraki, whose data were used to mete out the rough figures.
In Fukushima, home of the nuclear plant leaking all the radiation, about 17.5 percent of the prefecture is contaminated to that level.
The estimate was submitted Tuesday to a 12-member expert panel working out decontamination plans. The panel assumed that 5 cm of topsoil should be removed from contaminated areas, including pinpoint decontamination efforts in certain locations with radiation of 1 to 5 millisieverts per year.
The government is hammering out details on plans to remove and store the soil and leaves. But finding a location to temporarily store such a huge amount of radioactive materials will be an extremely sensitive and politically difficult task for the central government.
Breaking down the total, contaminated soil from residential areas was estimated at 1.02 million cu. meters, farm land at 17.43 million cu. meters and forests at 8.76 million cu. meters, the Environment Ministry said.
A single facility capable of housing the entire 28.79 million cu. meters of soil would have to be 1 sq. km inarea and 30 meters deep. But if the central government decides on multiple facilities, negotiations would have to be completed with numerous local governments.
The location for a temporary facility is still undecided, but the government is reportedly considering Fukushima Prefecture.
In late August, then Prime Minister Naoto Kan met with Fukushima Gov. Yuhei Sato and told him the state may ask his prefecture to host a temporary storage facility. Sato was reportedly taken aback by the sudden proposal.
A Fukushima government spokesman said there has been no such request from the central government since then, but Prime Minister Yoshihiko Noda's Cabinet is believed to be going along with the idea of building a temporary storage facility there.
Currently, the contaminated material that has been removed is being stored in several areas. Once the central government decides on a new storage site, the local governments will have to ship the contaminated material to the temporary facility.