Los Angeles will soon begin building a $740-million project to transform wastewater into purified drinking water in the San Fernando Valley, expanding the city’s local water supply in an effort to prepare for worsening droughts compounded by climate change.

The city plans to break ground next month to start construction of new facilities at the Donald C. Tillman Water Reclamation Plant in Van Nuys. When completed, the facilities will purify treated wastewater and produce 20 million gallons of drinking water per day, enough to supply about 250,000 people.

The drinking water that the plant produces will be piped 10 miles northeast to L.A. County’s Hansen Spreading Grounds, where it will flow into basins and percolate into the groundwater aquifer for storage. The Los Angeles Department of Water and Power will later pump the water from wells, and after additional testing and treatment, the water will enter pipes and be delivered to taps.

L.A. has been recycling wastewater for decades but has previously used the treated water for outdoor irrigation in areas such as golf courses and parks. With the new facility, which is scheduled to be finished in 2027, the city will for the first time start using purified recycled water as part of the drinking water supply.

The project has been in the making for three decades. The city built part of the infrastructure, including the pipeline and pump stations, in the 1990s, but the effort was derailed in 2000 when debate erupted over what opponents and newspaper headlines called a “toilet-to-tap” project. The issue was caught up in a mayoral campaign and a 2001 ballot measure calling for the Valley to secede from the city.

“This was recycled water that should have been in the city’s system 20 years ago, but the politics of water stopped it,” Gold said. “It’s great that it’s finally happening and will be completed quickly.”