In response to reports of a sinking ground surface around the 40-year-old Sarinah building in Central Jakarta, the building management plans to install devices to detect soil movement.

"In the near future, we will install two to four devices called inclinometers surrounding the building compound to monitor the movement and subsidence of soil due to groundwater exploitation," said Mardiana Daoed, director of the consultant company for Sarinah building structure, PT Deta Decon.

She was speaking on the sidelines of a media conference held by building management PT Sarinah on Tuesday.

She said the devices, which would cost the company hundreds of millions of rupiahs, would be placed about 40 meters underground and would be checked every two weeks.

It was reported last week the sinking soil around Sarinah complex had caused the tilting of the south annex of the main building, designated for the automatic teller machines center.

PT Sarinah dresident director Ketut Arnaya said during the Tuesday media conference the tilting of the annex, which had been discovered in 2007, would not affect the main building's construction.

"The structure of the south annex has been separated from the main building. The ATM center has been moved inside the main building, near the north entrance door," he said.

Between 1992 and 1994, the building management discovered the parking lot had subsided by two to three centimeters.

Mardiana said, "It is a natural thing for the surface to subside about 6 millimeters to one centimeter a year."

She said the ATM center constructed in 2003 on a shallow concrete slab foundation was unable to withstand the impact of the sinking soil.

"A stronger, deeper foundation is costly to construct."

The main building, she added, was built on a steel foundation 36 to 42 meters deep and on a concrete foundation of 33 to 36 meters deep in the hard soil.

"This kind of deep foundation is 100 percent guaranteed unaffected by soil movement," said Mardiana.

Head of the city's property management and control agency, Hari Sasongko, concurred the Sarinah main building was safe.

"The subsidence is a natural phenomenon in Jakarta, where the soil is relatively young."

The agency has requested the installment of an inclinometer and other supporting devices to assist the mapping of soil layers, horizontal and vertical movements of the soil, as well as the movements' path and origin.

"The building management will have its own consultant to monitor the device and report their findings to our agency," Hari said.

Hari said the 45,343 square-meter 15-story building on Jl. MH Thamrin, built on a 17,465 square-meter plot of land, was not the only multi-story building experiencing sinking soil.

"Nevertheless, Sarinah's parking lot is the most extreme case in the area," he said Tuesday, adding the devices would also benefit the building management in terms of its expansion plan.

PT Sarinah plans to expand the shopping mall into Sarinah Square, which will have apartments, a hotel and a business center in the complex.

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