Seoul to invest $434.3 mil. to overhaul aging tap water system

Filtered water flows through an advanced filtration basin at Gangbuk Arisu Water Purification Center in Namyangju, Gyeonggi Province / Courtesy of Seoul Metropolitan Government

The Seoul Metropolitan Government said Wednesday it will invest a combined 607.7 billion won ($434.3 million) to expand daily production capacity and modernize its aging municipal water infrastructure, as heavy summer consumption strains processing plants originally constructed four decades ago.

The infrastructure package addresses a growing supply bottleneck across the capital region.

Seoul's six primary water treatment complexes currently operate at an average utilization rate of 81 percent of their total design capacity. During peak summer heat waves, operational loads regularly surge past 90 percent. Compounding the capacity crunch is the physical decline of the infrastructure itself: four of the city’s six complexes have been in continuous, uninterrupted operation for more than 40 years.

To stabilize output, the Seoul Arisu Headquarters is initiating a two-pronged development strategy targeting both immediate volume expansion and comprehensive facility modernization across key supply hubs.

At the Gangbuk Water Purification Center northeast of Seoul, engineers have begun construction on a 276.1 billion won project to install advanced water purification technology capable of filtering an additional 250,000 tons per day. Launched in December 2024, the expansion will lift the facility’s total daily processing threshold from 950,000 tons to 1.2 million tons upon its scheduled completion in 2029.

Concurrently, municipal crews broke ground in late July 2026 on a 331.6 billion won overhaul of the Gwangam Water Purification Center east of Seoul. The project introduces a 100,000-ton expansion in advanced treatment alongside the replacement of intake wells and sedimentation basins that have been continuously active for 47 years. The site will also incorporate a new pre-ozonation filtration system processing 400,000 tons daily, with final construction slated for 2030.

Combined, the two expansions will inject 350,000 tons of daily processing volume into the municipal system. The added capacity will bring Seoul's average plant utilization rate down from 81 percent to roughly 74 percent — aligning the capital's water grid with international engineering standards that recommend operating below 75 percent to maintain safe emergency reserves.

Following the work at Gangbuk and Gwangam, municipal authorities said they intend to execute phased modernizations across older facilities at Amsa, Guui and Yeongdeungpo. Feasibility and planning studies for the Amsa plant, built in 1986, are scheduled to conclude later this year.

"Purification facilities function as the beating heart of Seoul’s water supply," said Kwon Min, head of the Seoul Arisu Headquarters. "Because these core utility systems cannot pause operations for even a single day, we will execute capacity expansions and infrastructure modernization without disruption to daily public service."

This article was published with the assistance of generative AI and edited by The Korea Times.