Post Date:03/27/2026 8:40 AMSkagit PUD has completed a reverse-osmosis system replacement on Guemes Island, installing updated equipment at the Potlatch Beach water system on the island’s west shore.
The system is unusual by most utility standards. The new plant draws saltwater directly from Guemes Channel at 40 gpm and forces it through an extremely fine membrane that blocks dissolved salts and other contaminants, letting only clean water molecules pass through. The process produces 17 gpm of drinking water. Sodium hypochlorite is then injected for disinfection before the water reaches customers. The PUD has operated the system since 1998.
Arlington-based Case Marine fabricated and installed a custom RO membrane skid sized to fit the existing facility footprint, with fresh water membrane flush capability for longer membrane life and updated PLC programming. RH2 Engineering assisted with design and equipment selection. The new skid was installed and was producing water within a week.
The system currently serves 34 connections and is authorized by the Washington State Department of Health for up to 182. Total project cost is approximately $302,000.Return to full list >>
