Exclusive: Rainy Season Begins, but Two-Thirds of Permeable Paving Blocks Found Defective

[Anchor]

Rainy season showers are forecast to continue across the country throughout this week. When heavy rain falls, the inability of the ground to absorb the water can lead to significant damage. To prevent this, the Seoul Metropolitan Government has been installing permeable paving blocks, which allow rainwater to drain through. However, it has been revealed that these blocks are largely defective and failing to perform their intended function.

Climate and Environment Specialist Reporter Jang Se-man reports exclusively.

[Reporter]

On a rainy city street, rainwater pools on the asphalt, while the path paved with blocks remains clear.

This is where permeable blocks, designed to allow water to pass through, have been installed.

The blocks are manufactured with numerous microscopic pores, allowing rainwater to drain and seep into the soil.

[Jo Si-hyung / Seoul Metropolitan Government Official in Charge of Permeable Blocks: Permeable blocks absorb some of the rainwater, playing a role in preventing urban flooding damage.]

Videos from manufacturers show a clear difference between permeable blocks that absorb water and standard paving blocks that do not.

But do the blocks actually installed on the streets drain water as effectively?

The Seoul Institute conducted a field survey of 30 locations where the blocks had been installed for less than a year.

The method involved placing a bucket on top of the permeable blocks and measuring how quickly the water drained through.

While 10 locations met the installation standard of absorbing at least 0.1mm per second, 18 locations showed an absorption rate of only 40 percent of the standard, and the remaining two did not drain any water at all.

This means two-thirds of them are defective.

[Park Dae-geun / Senior Research Fellow, The Seoul Institute: The results showed that about two-thirds were either clogged or mostly clogged. This is to raise awareness about the severity of the situation.]

Previously, the Seoul Metropolitan Government enacted an ordinance in 2015 mandating the installation of permeable blocks to reduce rain-related damage.

The city explains that over time, foreign substances such as dust and soil can enter and clog the pores of the blocks.

However, as these blocks were found to be largely defective less than a year after installation, critics argue that it is necessary to investigate whether substandard products were supplied in the first place.

The Seoul Metropolitan Government has decided to expand the scope of its investigation to 1,000 locations for precise measurement.

(Video Report: Kim Young-hwan, Video Editing: Ahn Yeo-jin)

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[Anchor]

We are joined by reporter Jang Se-man, who covered this story, to discuss it in more detail.

Q. What is the scale of 'permeable blocks' installed in Seoul?

[Reporter Jang Se-man: I have brought both a permeable block and a standard block. As you can see, the standard block has a smooth cross-section, whereas the permeable block is rough and characterized by many gaps. As mentioned earlier, the Seoul Metropolitan Government has mandated the installation of permeable blocks since 2015. However, they currently account for only about 15 percent of all sidewalks. Permeable blocks are 10 to 20 percent more expensive than standard ones. The city explains that the installation process is slow because they are not tearing up perfectly fine sidewalks to replace them, but rather replacing them only when the old blocks need to be changed.]

Q. Was the possibility of clogging not anticipated?

[Reporter Jang Se-man: They were well aware of that possibility. That is why the current system requires the performance of these blocks to be inspected once every two years. However, this has not been properly implemented until now. The installation rate of permeable blocks is not high, and there was no established testing method to measure their performance. It was only recently that the Seoul Institute developed a testing method, making this year the first time a proper inspection has been conducted. The city explained that they expected some clogging and had initially planned to remove foreign substances from the blocks by spraying them with high-pressure cleaning equipment.]

Q. What are the countermeasures for clogged permeable blocks?

[Reporter Jang Se-man: Even normal permeable blocks can get clogged with foreign substances after long-term use. Performance maintenance and management are crucial. The equipment you see now is used to spray high-pressure water to remove debris, but there are currently only four such units in Seoul. It is important to restore the performance of these blocks by expanding the use of this high-pressure cleaning equipment and increasing the frequency of cleaning. Furthermore, a broader investigation is needed to determine if there were any issues in the supply process, such as the issuance of test reports, and to assess the overall condition of other permeable blocks.]
※ Please note: This article was translated by AI and may contain errors.