Special topic: SINKHOLES
Record-breaking skyscraper threatened by sinkholes
(2014 August 6: http://www.cnn.com/2014/08/05/world/asia/seoul-skyscraper-sinkholes/)
(CNN) -- The construction of what would be Seoul's tallest building has hit a snag following the appearance of a number of mysterious sinkholes in and around the neighborhood where it is being built.
Residents of South Korea's capital are alarmed by the increasing incidence of sinkholes -- depressions, measuring up to several feet in depth and diameter, which have suddenly appeared around Seoul.
The first one was discovered in June, and since then several others have appeared, local media have reported. Now, in a climate marked by increased safety concerns, the construction of a huge skyscraper in the city has come under scrutiny.
Last month, two holes within a couple of meters of each other were discovered near the National Assembly in the Yeouido district of the capital.
Several examples of this unexplained phenomenon have occurred near the site of the Lotte World Tower, a half-constructed commercial and office development by Korean conglomerate Lotte which, when completed, will be the sixth tallest tower in the world.
Holes have appeared in at least two streets in the Songpa district, where the new tower is being built, including a 50 centimeter (20 inch) wide hole only half a kilometer (a third of a mile) from the Lotte World Tower construction site.
So far, authorities are baffled. "We do not know the cause yet," a police officer told the Korea Times. "In cooperation with Seoul Metro and Seoul Metropolitan Government, we investigated the problem and only found that the holes have nothing to do with sewerage."
A lake near the site, which appears to be shrinking, is also cause for concern. Water levels have fallen about 70 centimeters (27 inches), although Seulki Lee, a spokesperson for Lotte Group, told CNN that it would be "nearly impossible" for the water to drain into the tower's foundations due to a slurry wall between the lake and the construction.
The spokesperson also said that the company was looking into the mysterious sinkholes.
"We are working on an investigation of sinkholes but it will take some time to figure out what's going on," she said.
She said that academics and engineers from Lotte have told the construction company that the sinkholes are not related to the site but it is "necessary to figure out what is going on" to provide assurance for the public.
Plans for the 555-meter (1,821-foot), 123-story tower were first put forward almost two decades ago, but planning permission was slow in coming, due to security concerns from a nearby military base.
Construction of the tower, designed by American firm KPF, is underway and more than half of the tower's floors have been completed. The architecture firm was, at the time of press, unavailable for comment.
Professor Hong Gun Park of Seoul National University's Department of Architecture and Architectural Engineering was a consultant on the project, completing an "outsider's evaluation."
He told CNN that the foundations of the building were solid, and that Seoul had no history of subsidence.
"People found sinkholes near the building site, (and) since there is a small lake, they are worried about the robustness of the foundation of the building.
"However, recently many sinkholes were found here and there in Seoul. Furthermore the foundation of the building is deep and is sitting on the deep hard rock. Thus in my opinion there is no problem (with) the structural safety of the building."
He said that it was unlikely that the Seoul municipal government would halt construction without reasonable cause.
The safety concerns over the building come months after the country was shocked by the sinking in April of the Sewol ferry, which led to widespread criticism throughout South Korea that safety was not a priority. Almost 300 people, mostly teenagers on a school trip, died when the ferry capsized.
An increasing number of sinkholes have appeared in and around the neighborhood where the Lotte World Tower is being built in Seoul, South Korea. The first one was discovered in June and several others have appeared since then, according to local media reports, causing the construction of what would be Seoul's tallest building to come under scrutiny.
Sinkholes Threaten Record Skyscraper
(2014 August 6: http://www.durabilityanddesign.com/news/?fuseaction=view&id=11798)
The spreading eruption of sinkholes throughout Seoul, South Korea, is now threatening progress on what was to be the capital's tallest building.
Several sinkholes have opened up this summer in the neighborhood where the $3.5 billion Lotte World Tower is under construction, The Korea Times reports. Three holes were found in June, and several more appeared in July, the news outlet said. Two recently appeared just meters apart near the National Assembly.
Streets are affected as is a lake near the Lotte project. One hole about 500 meters from the construction site measured half a meter wide and 20 centimeters deep.
Meanwhile, the lake's water level has dropped from 16.5 feet to 14 feet recently, the Associated Press reported.
Park Chang-khun, a civil engineering professor at Kwandong University, told the AP that underground water was pooling in the sixth basement level of the Lotte tower, suggesting water displaced from the lake.
A recent report by Korea Today noted that more than 130 sinkholes have opened up in Seoul in the past five years.
Seoul has seen more than 130 sinkholes erupt in the last five years, raising concerns of structural ability and safety throughout the capital, Korea Today reported.
Planned for 123 stories, the Lotte World Tower will be the world's sixth-tallest building when it is completed. The project is being developed by the Lotte Co. Ltd., a Japan-based food and shopping multinational.
The project has been on the books since 1995, and groundbreaking did not begin until March 2011. Nearly 70 floors of the building have been completed.
The developer is doing its best to reassure the public that the project is safe. One company official said the holes were far from the construction site and were not necessarily caused by the project.
Wikimedia Commons / Teddy Cross
Seventy of the Lotte World Tower's 123 stories had been completed as of July.
But fears for public safety—and doubts about the government's ability to guarantee it—have run high since the capsizing of the Seoul ferry in April killed 300 people, most of them teenagers.
The Lotte World Tower is now undergoing a review by experts and has been ordered to put on hold the opening of adjacent low-rise buildings that form part of its complex.
Lee Won-woo, CEO of Lotte Moolsan, the tower's builder, told reporters last this month that Lotte had pumped water into the lake to maintain the water level while a separate inspection by Korean and British experts is underway, the AP reported.
South Korea's capital has seen about a half-dozen new sinkholes this summer.
The city formed the advisory team of lawyers, engineers, architects, environmentalists and university professors to submit their opinions about the construction site.
SInkholes have been causing damage worldwide in the past year, swallowing homes and other property on multiple continents. In the U.S., Florida has been particularly hard hit.
In February, a security camera captured a sinkhole-triggered collapse at the National Corvette Museum in Bowling Green, KY, swallowed a number of classic cars.
Shrinking lake, sinkholes threaten 123-storey tower being built in Seoul
The tower will usurp Pyongyang
For the developers of the world's sixth tallest building in Seoul, a mysteriously shrinking lake and the appearance of small sinkholes in residential neighbourhoods couldn't have come at a more inopportune time.
Plans for the 555-metre tower first surfaced in 1995 and it took another 15 years to gain approval, after the air force objected to it as a risk to a nearby military airport.
Now it faces new doubts as South Korea reels from the Sewol ferry sinking in April that killed hundreds of teenagers. The disaster provoked a scathing reassessment of an ethos that put economic progress before safety.
This month and last, residents in parts of Songpa district surrounding the development reported holes in at least two roads.
One about 500 metres from the building site was half a metre wide and 20cm deep. There were claims that construction was the cause a drop in the depth of the lake the tower overlooks, from five metres to 4.3 metres.
With about 70 of its 123 floors completed, the Lotte World Tower is now under review by experts and has delayed the opening of adjacent low-rise buildings that form part of the complex.
Lee Won-woo, CEO of Lotte Moolsan, the tower's builder, said recently that Lotte had pumped water into the lake to maintain the water level while a separate inspection by Korean and British experts took place.
Another official at Lotte said the holes were far from the construction site and could be caused by other factors.
Songpa district's local government said the tower was not to be blamed for the sinkholes. But the Seoul city government said it would look at the lake's lower level and how that affected the land in the area.
Lotte Group plans to fill the US$3.5 billion complex including the Korean peninsula's tallest tower with a high-class hotel, office accommodation, flats and an observatory.
"After Sewol, the public's sentiment has taken a turn to stress safety over any other values including economic development," said Park Chang-kun, a professor of civil engineering at Kwandong University, who is on a special Seoul city government advisory team on the tower.
When the ground gives away – sinkholes in other countries
(2014 August 6: http://www.cnn.com/2014/08/05/world/asia/seoul-skyscraper-sinkholes/)
Eight Corvettes fell into a sinkhole that opened up beneath a section of the National Corvette Museum in Bowling Green, Kentucky, on February 12. The sinkhole was about 40 feet wide and 25-30 feet deep.
The rear portion of a residential home is consumed by a sinkhole November 14 in Dunedin, Florida.
A 60-foot-wide sinkhole formed underneath the Summer Bay Resort in Clermont, Florida, about 10 minutes from Walt Disney World, on August 11. One resort building collapsed, and another slowly sank.
A backhoe is swallowed by a sinkhole in Montreal, Quebec, Canada, on August 6. The driver of the backhoe was not injured.
A sinkhole killed a guard at a construction site in Shenzhen, China, on March 27. The sinkhole might have been caused by heavy rains and the collapsing of old water pipes running beneath the surface, the Shenzhen Special Zone Daily reported.
Workers watch the demolition of the house where a sinkhole opened three days before in Seffner, Florida, on March 3. Sinkholes caused by acidic groundwater corroding the limestone or carbonate rock underground are common in Florida, according to the Florida Department of Environmental Protection.
Buildings fell into a sinkhole near a subway construction site in Guangzhou, China, in January 2013. The hole measured about 1,000 square feet across and 30 feet deep and was without casualties, according to a state media report.
A basketball court in Ortley Beach, New Jersey, fell into a sinkhole caused by Superstorm Sandy in November 2012.
In July 2011, a man inspects a 40-foot-deep sinkhole that a family found after they heard a booming noise in their kitchen in Guatemala City, Guatemala.
Construction on a subway line caused a huge sinkhole to form in a road in Beijing in April 2011.
An aerial photo shows sinkholes created by the drying of the Dead Sea near Israel in 2011.
A utility worker examines the area around a sinkhole caused by a broken water main in Chevy Chase, Maryland, in December 2010.
Tropical Storm Agatha caused a sinkhole to open in Guatemala City in May 2010.
A fire truck protrudes from a sinkhole as Los Angeles Mayor Antonio Villaraigosa talks to reporters in September 2009.
A water main collapsed an entire block-long part of Ocean Park Boulevard in Santa Monica, California, in December 2002.
In Orlando, a sinkhole 150 feet wide and 60 feet deep swallowed trees, pipelines and a section of sidewalk near an apartment building in June 2002.
A 30-foot-deep sinkhole appeared in a busy street in a suburb east of downtown Los Angeles. A motorist drove into the hole but was rescued before a concrete slab fell onto the car.
"The Great Blue Hole" is the name of a massive underwater sinkhole off the coast of Belize. The deeper you go, the clearer the water becomes, revealing amazing stalactites and limestone.