A multi-million-dollar expansion means millions of more gallons of clean drinking water for San Diego’s South Bay.  The Sweetwater Authority dedicated the expansion of its Richard A. Reynolds Groundwater Desalination Facility Thursday. The $42 million expansion doubles the plant’s output to 10 million gallons of water a day.  Sweetwater Authority had to dig five new wells for the desal plant, which is located in Chula Vista. “It’s a day to celebrate,” said Sweetwater’s Director of Engineering Ron Mosher.