Valley Water in the South Bay is set to vote Tuesday on whether or not to join other local water agencies in contributing to Gov. Gavin Newsom’s Central Valley water tunnel project. A dozen agencies have voted in favor of helping fund the planning and design of the 45-mile long underground tunnel that would connect the Sacramento–San Joaquin River Delta with the California Aqueduct. The Santa Clara Valley Water District will consider a $9.7 million contribution towards the massive infrastructure project that’s estimated to cost a total of $20 billion. The idea is to build a concrete tunnel 36 feet in diameter to take fresh water from the Sacramento River and divert it underground to large water pumps located in Tracy. From there, the water would be diverted to other parts of the state and the roughly 27 million people who rely on the water that comes from the Delta. Former Gov. Jerry Brown for years pushed for two tunnels. Newsom changed the project to one tunnel. The state says the tunnel is badly needed to capture more water during the big rains and protect our water supply from major earthquakes. The current delivery system relies on levees that could crumble in a big shaker and allow salt water to intrude. Environmental groups and counties along the Delta oppose the water tunnel, arguing the diversion of fresh water would make the Delta waters saltier, lead to more algae blooms and hurt the fish who swim in it.