Illegal dredging has put the longest bridge on one of Sichuan Province 's major highways at risk of collapse.

The 396-metre-long Shitingjiang Bridge, located in Guanghan, a small city on the Chengdu-Mianyang Expressway, could struggle to withstand the upcoming flood season, officials said earlier this week.

On December 30, 2005, inspectors from the Chengdu-Mianyang Expressway Co Ltd, which oversees the road, watched closely as a dredger moved to an area about 200 metres from the bridge to mine sand.

As the barge gradually moved into the bridge's 200-metre safety zone, they reported the case to Guanghan Municipal Water Conservancy Bureau.

After an investigation, the bureau found that a local sand factory in Guanghan had bought the rights to extract sand from a 1,240-metre-long stretch of water, starting from the 200-metre-safety zone, at a Guanghan government auction last September.

But later this February, the factory signed an agreement with a nearby village to dig a channel starting 160 metres from the bridge to divert water into the village, which had inadequate water for irrigation.

As the local government prohibited both sand mining and pit digging in water within 200 metres of the bridge, the village asked the Chengdu-Mianyang Expressway Co Ltd to endorse the agreement in April, a request the company refused.

However, the factory still used the agreement as an excuse to begin mining in the safety zone.

"Our inspectors repeatedly informed the sand company of the local government's regulations, but despite agreeing to stop, they persisted," said Cai Kezhang, an official with the expressway company.

On May 30 the municipal government ordered the dredging to stop, and the factory withdrew the barge and filled the channel.

However, the dredging has caused the river bed below the bridge to drop more than 1 metre, severely damaging the bridge's foundations.

As the flood season draws near, the expressway company is worried that the bridge will not be able to take the strain, Cai said.

This is not the first instance of its kind in the province.

In September 2004, the newly built Sandushui Bridge on the Chengdu-Wenjiang-Qionglai Expressway collapsed because of illegal dredging, according to the Sichuan Provincial Water Conservancy Bureau.

(China Daily June 8, 2006)