A 1,500-year-old World Heritage site in danger of collapse due to water erosion should be saved by a project to be launched within the year, experts said during the Int'l Seminar on Grotto Protection held in Shanxi between July 26-30.

At least 21 of the 45 major caves at the Yungang Grottoes near Datong, north China's Shanxi Province, have suffered water damage, and the organization charged with looking after the site says urgent action needs to be taken.

According to the Yungang Grottoes Institute, most seriously affected is the central Wuhua Cave, in which the tops of five supporting stone pillars have been eroded and are in danger of collapsing.

Pillars in front of the ninth, 10th and 12th caves are suffering from serious weathering as well, and exterior carvings of the three caves have eroded away.

"Water infiltration, which directly results in weathering, threatens the grottoes most," said Huang Jizhong, a researcher from the institute who leads the new project.

"Therefore, we have a comprehensive conservation plan to prevent further deterioration, and the anti-infiltration project is the key part."

The Yungang Grottoes contain 53 rock temples, dating from AD 460 to 524, carved into sandstone cliff.

Their 51,000 representations of Buddha, ranging from miniature bas-reliefs to statues 17 meters in height, are carved directly into the rock. Most carvings were restored in the Ming (1368-1644) and earlier dynasties by plastering mud over the eroded carving and were then decorated elaborately with polychrome and gilding.

However, over the centuries, the grottoes have suffered deterioration from rain, wind and earthquakes, and more recently from pollution due to industrialization and urban development.

Huang said the institute has been adopting anti-infiltration measures since the 1960s, but none of them have brought striking results. A joint effort with the US Getty Conservation Institution in 1992 was unsuccessful, as well.

According to Huang, the preliminary research of the new project started in 2002 and passed an evaluation last week by a group of 12 experts from such institutions as the State Administration for Cultural Heritage, the Chinese Academy of Science and the Chinese Academy of Engineering.

A special kind of clay named bentonite will be used for the drainage system above the cave ceilings in a 360,000-square-meter area, Huang said.

The use of bentonite for cultural heritage conservation is the first attempt of its kind in China. "It's a type of natural material and will not do any harm to the grottoes," Huang said.

The total expenditure will be 99.74 million yuan (US$12.3 million), and the project will begin with a few caves to test how it works. Huang said no timetable has been set, but the whole project will probably continue for years.

(China Daily August 3, 2005)