Tokyo Electric Power Company, or TEPCO, hopes the move will slow the accumulation of radioactive wastewater in the buildings, which is building up at a rate of 300 tons a day due to the inflow of groundwater.
The utility will target groundwater from wells dug around the No.1 through No.4 reactor buildings. It plans to filter out much of the radioactive material before releasing the water into the ocean.
Workers on Thursday began pumping up groundwater from 20 wells. They plan to remove 200 tons through the afternoon and store it in special tanks.
TEPCO has yet to reach an agreement with local authorities and fishermen about when to release the decontaminated water, but it will likely be later this month.
The utility claims the drainage will cut the amount of wastewater in the reactor buildings by about half.
But local authorities and fishermen worry about what could happen to the environment if something goes wrong.