10,000 liters of arsenic

About 10,000 liters of water containing high levels of arsenic have leaked at a drilling site in Hokkaido, northern Japan.

Steam began erupting at the drilling site of a geothermal resource survey in Rankoshi Town in late June. High levels of arsenic were subsequently detected in water samples taken at the site.

The Japanese company conducting the drilling is currently transferring the tainted water to a well in another location.

But Mitsui Oil Exploration Company on Sunday said about 10,000 liters of tainted water being kept in a reservoir had overflowed into a forest owned by the Hokkaido prefectural government.

Company officials said the overflow volume accounted for about 0.5 percent of the water that has been spewing out of the ground in the form of steam every day.

They also said the arsenic levels in the water that leaked were found to be lower than the amount permitted for agricultural-use water when measured at three locations where water for agricultural use is drawn.

The company explained the leak's cause, saying a pipeline valve used to transfer water to another location should have been open but was closed.

Tainted water had also overflowed earlier this month. Company officials said they will determine why the valve was closed and pay closer attention to the site's operation.