The toxic spill, caused by an explosion at a chemicals factory in China on November 13, is snaking its way down the Amur river.
Officials said the sandbag dam, one of two built hastily to prevent the possible flow of benzene-contaminated water from the Amur river into Khabarovsk, a city of 600,000 in Russia’s Far East region, would be completed during the night before the poison reached the city.
Two Russian military Mi-26 helicopters were flying non-stop to ferry sandbags to the site of the dam on the Kazakevich channel, one of many small branches of the Amur river west of Khabarovsk, to complete the last few meters of the 300-meter levy across the waterway.
A spokesman for the Russian emergency situations ministry, quoted by Interfax, said there were around 3,000 Chinese labourers, using 200 heavy construction trucks, working on the project in cooperation with the Russians.
Local officials are confident the dam will be completed before the first traces of
the spill could reach Khabarovsk.
Analyses of the water in the Amur river west of the city were being taken
According to officials sixty three tests had been conducted at various points on the river since Monday and no traces of toxic benzene had yet been detected.
The Amur river, which runs along the Russia-Chinese border before veering
exclusively into Russian territory, splits into numerous smaller branches above
Experts say the effect on the city will depend on which of these channels it enters and how strongly it is concentrated.
Benzene is a known carcinogen used as an industrial solvent and as a component of gasoline.
More than 100 tons of the chemical were dumped into the Songhua river, a Chinese tributary of the Amur, following the blast at the plant outside Harbin.
While most Russian experts forecast negligible effects from the spill on the population of Khabarovsk, nearly all have described it as a major ecological disaster which will have consequences on the environment along the Songhua and Amur rivers for years to come.
In the weeks that it has floated down the river, the spill has stretched in length to more than 190 kilometres and is expected to take a week for it to pass through Khabarovsk, experts said.
More than a month of advance warning however has allowed local residents and
authorities in Russia to preposition huge stocks of potable water in the event
that the city has to shut down public water treatment facilities.