Just like any other sewage treatment plant, the wastewater treatment facility in Healdsburg, California purifies wastewater into clean and disinfected water that can be discharged back into the environment. What makes it unique is the floating solar array that sits on top of the wastewater treatment ponds.
An Example of Energy Efficiency
The solar array is designed to power the plant while at the same time, manage the recycled water ponds by helping to reduce evaporation and algae growth. Ronald Howard, CEO of Northern California Power Agency, said, “This is one of the most unique solar installations in California and was a must see for HCI members. This unique floating solar project is one of only three in the nation an provides almost eight percent of the city’s annual electrical needs.” The participants of the 2025 Hometown Connections Annual Gathering visited two treated water ponds at Healdsburg’s wastewater treatment plant that were covered with rows of solar panels. The solar panels are held in place with a metal cable anchoring system that allows the panels to rise and fall as the water’s depth changes. This project, in large part, ensures a significant reduction of algae growth so that the water is usable, while the solar panels provide clean power.
The wastewater-reclamation facility is part of the City of Healdsburg’s wastewater utility, which is designed to handle an average of 1.4 million gallons per day with a sustained peak of 4 million gallons. It includes 36 miles of sewer mains and 9 sewer lift stations. When White Pine Renewables built the 4.78 megawatt photovoltaic (PV) solar array in 2021, it was the largest floating solar project in the United States. This cutting-edge solar power site is managed for the city of Healdsburg by Rob Scales, Water/Wastewater Manager. Scales said, “The site holds 25 million gallons of water in a wastewater pond. The water must be held, by statute, until a certain date in May, and then can be released into the Russian River. Until that date, we hold the water and try to prevent algae growth. The pond has 11,600 solar panels floating. The city of Healdsburg is proud to be a leader in solar power adaptations!
The Healdsburg Wastewater Treatment Plant is unique in another way as well – It is located in Sonoma County, the heart of California’s Wine Country. The local wineries are happy for several reasons. One, because the treated water has no impact on sensitive equipment as the algae growth is controlled. Two, there is sometimes a backlash against using agricultural lands for solar farms and the cost per acre in Sonoma County continues to increase. Terry Crowley, Utilities Director for the city of Healdsburg stated, “This adaptation – floating solar panels – addresses both concerns – the cost of and the concerns over using agricultural land for soar installations. The Healdsburg floating solar project provides power to around 1,120 households on an annual basis.
Healdsburg wastewater treatment manager Rob Scates pointed out the Canada Geese walking on the solar panels. “Their egg laden nests are on the banks. Cleaning bird droppings will be done when the cost is outweighed by a loss of efficiency in the solar panel output, it must pay for itself.”
Healdsburg is the only city-owned utility in the county and can boast lower rates than the investor-owned utilities. In fact, this solar installation can act as an emergency power supply should wildfire threaten the area. The natural disaster of wildfires in the state is an ongoing and worsening problem. California, often a leader in environmental aspects, has stipulated a milestone of attaining a renewable energy portfolio of 60% by 2030. This project contributes to that goal.
The Plant provides four main benefits to its neighbors. First, floating the solar panels on top of the wastewater removes the need to compete with wine growers for land. Second, it provides recycled treated wastewater for vineyard irrigation. Third, the recycled water provides water security during the recurrent droughts occurring in the area. Fourth, the energy produced provides renewable energy for the area.