Photo/IllutrationThe Shibuyagawa river flows behind the wall to the left in the area above the ceiling of a new east exit underground plaza under construction at Tokyo’s Shibuya Station. (Kenji Tsuji)

Railway operator Tokyu Corp. showed off the progress of construction on a new underground plaza and massive water tank around Tokyo’s bustling Shibuya Station on June 16.

“We plan to thoroughly restructure the station so that people will be able to make use of the Shibuya district with ease,” said Masahiro Mori, a senior official of the company’s development business department.

The area around Shibuya Station, one of the busiest rail hubs in Japan, is undergoing a major makeover on a scale that occurs only once in 100 years, according to the railway operator.

The new east exit underground plaza will measure about 1,600 square meters. It will be located beneath the Shibuyagawa river, which flows one level underground. The course of the river was redirected last summer as part of the project.

Below the plaza and 25 meters below ground level, a huge water tank is also being installed. The tank measures 22 meters by 45 meters and is 7 meters deep, a capacity that can hold up to 4,000 tons of rainwater, equivalent to the volume of eight 25-meter-long swimming pools.

Because Shibuya Station is surrounded by hills, the water tank is designed to help prevent flooding of the station and neighboring areas during rainstorms.

Tokyu said the reservoir will be utilized if the district experiences heavy showers totaling more than 50 millimeters per hour.

The railway operator plans to complete the plaza by around fiscal 2019 and the water tank by fiscal 2020.