The MTR has halted a section of the express rail construction project after failing to contain land subsidence of a fishpond at the Mai Po marshes. Environmental groups are “deeply concerned” over the ecological damage the railway corporation has caused.
A spokesperson for the MTR told HKFP that the company has temporarily stopped underground tunnel boring underneath the Mai Po site near Yuen Long as a precautionary measure and acknowledged public concern over the incident.
The spokesperson said that the company currently has no plans for resumption of the tunnel construction and will focus on repairing the area.
Sludge was seen spewing out from underground on the embankment of a fishpond of high ecological value last week. A 2-metre-high column of mud water was recorded at one point.
Following the incident, one of the measures the MTR-hired contractor took to repair damage was to plug the spew with concrete. However, InMedia reported that the repair was ineffective and the entire section of embankment has sunk underwater.
During the initial repairs, the contractor also made the mistake of pouring sludge into a reed pond on the site. The site is designated under the Ramsar Convention as a wetland of international importance.
WWF Hong Kong said in a statement on Wednesday that it is “deeply concerned” about the subsidence: “It is worrying that MTR has yet to identify the cause of the subsidence.”
It pointed out that the MTR had previously said express rail construction would not affect the wetlands, but the current incidents—sludge leakage, negative environmental impact on bird habitat, and land subsidence—appeared to contradict the company’s claims.
“WWF strongly urges MTR to immediately investigate the cause of the problem and implement effective measures to prevent endangering the precious biodiversity of the Mai Po and Inner Deep Bay wetland complex,” the statement said.
Conservation officer of the Hong Kong Bird Watching Society Woo Ming-chuan told InMedia that the ecology of the fishpond has been severely damaged. Woo said that the pond is no longer suitable for fish farming, and birds have lost a feeding place due to the contamination.
The affected fishpond is located on the edges of the Mai Po Ramsar site. Sightings of the critically endangered spoon-billed sandpiper were reported last year in the area.
On Saturday, the MTR said that the construction of cross-border underground tunnels is located 25 metres beneath the fishpond. During the tunnel-boring process, the front-end of the tunnel-boring machine must be artificially pressurised to ensure safety.
The company said that if there are minute holes on the surface, air pressure would be released through the holes. He added that the spillage of sludge is uncommon.
A construction worker said that the water levels of the pond had increased from the 1 metre norm to 3 metres, meaning that the bottom of the fishpond was subsiding and there was an outflow of water and soil from underground. Environmental groups have also reported seeing air bubbles appear on the water surface since construction started in 2011.
Prior to its launch in 2008, the express rail construction project sparked public concern. Possible subsidence of 0.1-0.5 metres was noted in the MTR’s environmental report for the construction. The Shenzhen section of the construction project, which has similar soil conditions as Mai Po, has seen four instances of land subsidence since 2008.
In 2014, the MTR announced that it had to delay the construction project, saying that it was unable to accurately survey the geological conditions of the area before the construction started.
The MTR told HKFP that it has a 24-hour survey team responsible for monitoring the environment and alerting the company if any issues arise. The company is in contact with various environmental groups to follow up on the situation.
Last month, MTR revealed its new estimates for the completion date and costs for the high-speed rail project. The opening date of the city’s cross-border link will be delayed from this year to the third quarter of 2018 and costs have risen by 31 percent to HK$85.3 billion. The MTR’s CEO said that the government should cover the extra costs.
The Mai Po marshes were designated a Ramsar site in 1995. The Ramsar Convention is an international treaty signed in 1971 on the conservation of wetlands. The Mai Po Ramsar site supports 16 globally threatened bird species and is particularly important due to it being the midpoint in the East Asian–Australasian migration route. More than 20,000 birds regularly use the area to rest and refuel before continuing their journey.