Deep in the Piedmont Hills, Gregg Semler and Casey Leblanc are checking up on what could be described as the Bay Area’s newest and smallest hydroelectric power plant. … The team installed the miniaturized turbine in a pipeline connecting part of the East Bay Municipal Utility District’s water distribution system. It takes the place of the normal water pressure regulator, housed in a small building next door. But instead of just controlling the flow, they say it harnesses it to produce electricity, spinning the turbine-driven generator.