Race to get going on sinkhole-hit street

The government hopes to gradually reopen a section of Hai Tan Street in Sham Shui Po, which has been closed to traffic after a sinkhole formed on Friday, as soon as 6 am today.

Ground subsidence caused the eight by 12-meter sinkhole, which is about four meters deep, to form during heavy rains.

The water supplies, drainage services and highways departments will jointly investigate the cause.

A dozen maintenance workers have been removing road signs and barriers that fell into the sinkhole and filling it with gravel.

Hai Tan Street between Yen Chow and Kweilin streets remains closed, with affected buses diverted.

Kweilin Street between Tung Chau and Hai Tan streets was fully reopened yesterday.

The Water Supplies Department said that no water pipes were damaged.

However, the Drainage Services Department reported two foul sewers that measure 225 millimeters in diameter and two meters in depth sustained damage, while a 300-mm diameter stormwater sewer was also hit.

Director of Water Supplies Roger Wong Yan-lok, who inspected the site yesterday, believes the incident was caused by a damaged underground pipe due to soil erosion from the heavy rain.

"The department will use radar to check for similar issues on nearby roads and take preventive measures if needed," he said.

Hong Kong Institution of Engineers president Aaron Bok Kwok-ming said underground pipes in the area might have cracks for a long time now that led to groundwater flows and soil movements, causing erosion and voids.

The frequent rain recently expanded these voids, leading to the road section's collapse.

Bok said it is difficult to detect road subsidence risks on concrete roads, so he urges regular inspections of underground pipes, and for the public to report any potholes.

Legislative Council member Scott Leung Man-kwong, who represents Kowloon West, hopes the government will step up inspections of underground pipelines in districts whose urban infrastructure are older to prevent similar incidents.