ZHENGZHOU - Authorities in Central China's Henan province have promised to clean up a toxic waste dump after local residents aired their concerns about contamination in their drinking water.

Fears mounted among villagers near the city of Yima, where 250,000 metric tons of chromium waste have remained for 10 years, after news spread about chromium waste illegally dumped near a reservoir in Southwest China's Yunnan province in August, sickening local residents there.

Residents in the town of Lianggou have reported seeing yellow sediment, a sign of chromium contamination, in their tap water, leading them to suspect that a dump site on a nearby hill was to blame for the appearance of the sediment.

"Water flowing down from the hill is severely polluted. Nearby plants have shriveled and the well water tastes bitter," said local resident Wu Yinxing.

Pollution fears have even provoked protests from local residents over the past five years, Wu said.

The city's environmental protection bureau said the waste, produced by a local chemical plant, remained unprocessed after a power plant built to deal with the waste was shut down in 2005.

Later attempts to decontaminate the area were hampered by cost issues, according to Li Fajun, the city's vice mayor. He said it would cost 140 million yuan ($22 million) to clean up the contamination.

The toxic waste thus remained stored at the dump site until a prolonged flood season this year caused a leak at the site, said Qi Zhanyuan, deputy director of the city's environmental protection bureau.

Nearby land has also been affected, although tests conducted on underground water in the area came back negative for contamination, Qi said.

The city government of Yima has pledged to reopen the power plant and enlist two companies to process the waste with an investment of 80 million yuan this year.

The decontamination will be completed by October 2012, the city government said.

In a related case, 10,000 metric tons of chromium waste in Henan will be disposed of by the end of this month, according to the Henan Provincial Department of Environmental Protection.