OSAKA — Two Mitsubishi group companies failed to report that they had detected high levels of arsenic and selenium in underground water in 1997 at a business and housing complex they operate in Osaka, sources said Tuesday.
Contaminated underground water was detected at the Osaka Amenity Park in Kita Ward, but Mitsubishi Materials Corp. and Mitsubishi Estate Co. did not disclose the findings for more than five years.
During an inspection conducted in the spring, arsenic at 65 times the maximum allowable level and selenium at 83 times the maximum level were found in underground water at the site, they said.
The complex features two high-rise apartment buildings and the Imperial Hotel. There is also a possibility that the contamination may have spread to neighboring areas through the underground water.
“We did not make the findings public because we did not think the water posed a safety problem as the surface is covered with asphalt,” an official at Mitsubishi Materials said.
The asset value of land and buildings usually falls when contamination is confirmed at the relevant site. A resident of the complex said the concealment of the discovery may constitute breach of trust.
The complex was developed on a site previously used as a smelting plant by the predecessor company of Mitsubishi Materials. Mitsubishi Materials began selling housing lots at the site in 1997.
According to the two Mitsubishi firms, contaminated earth was detected during construction work in 1989. The tainted soil was removed at a cost of around 3 billion yen.
An inspection conducted in January 1997, however, found that underground water at the site was also contaminated, the companies said. They said regular inspections have since been carried out.
The firms did not reveal the findings to the public, but following a newspaper report last month, residents of the complex were finally briefed Sept. 28 on the contamination. “We plan to ask a third party to conduct an in-depth investigation to assuage concerns among our residents and users,” the Mitsubishi Materials official said.
The complex, which covers an area of about 5 hectares, consists of the Imperial Hotel, a 180-meter office building and two 30-story apartment buildings. The development was completed in January 2001.