STOCKTON, Calif. (CN) –With California trudging ahead with a contentious $16.7 billion water project, a cache of environmental and social concerns remain around its plan to replumb the source of drinking water for an estimated 25 million residents. Backed by the state’s largest urban and agricultural water suppliers, outgoing Gov. Jerry Brown wants to build two massive 30-mile-long tunnels and funnel water from California’s largest river directly to farms and cities to the south.