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.