Tankers containing sewage water from the landfill in Liulitun, a neighborhood in Beijing's Haidian district, have been illegally discharging their contents into wells for clean-water pipelines during the past several years, sina.com.cn reported on Tuesday.

The illegal dumping came to light when one of the tankers was impounded by Haidian urban management officials on April 8 as it was en route to Xi'erqi, a neighborhood in the district about 10 kilometers away from the landfill.

Workers at the landfill, who spoke under the condition of anonymity, said they dump about 200 tons of sewage water via tanker trucks on a nightly basis. The dumping saves garbage facility about 2.8 million yuan, or $451,000 U.S., per year.

The sewage tankers, which travel under the guise that they are sprinkler trucks, depart the landfill after 10 p.m. in order to minimize suspicion of their activites. They dump smelly sewage water through a black tube into the wells for clean-water pipelines in Xi'erqi neighborhood.