The Sierra Club joins the battle! Here’s what they have to say about one or two tunnels:
“The Delta tunnels represent a fundamentally flawed approach to managing the Delta. They would divert water needed to flush the Delta and protect wildlife.”
“One tunnel conveying less water makes even less financial sense. Many of the initial construction costs are still present, and the project promises even less water. This approach will likely stick ratepayers with higher bills with no benefit.”
“The shift to one tunnel without starting over in the application process on some permits isn’t legally defensible. Sierra Club California is currently one of many parties protesting the change in water rights for the tunnels at the State Water Resources Control Board. A big change like this substantially changes the project’s impacts. These hearings must begin again to provide adequate due process for impacted parties.”
“DWR will have to redo portions of its Environmental Impact Report (EIR) for the project. A one-tunnel approach was never studied in depth in the original EIR. If the department does want to roll out the project in stages it will have to backtrack its findings in the original EIR that notes that a phased approach won’t work.”
“Sierra Club California continues to argue for an evidence-based, climate-resilient approach to the Delta. That means limiting the pumping that has degraded the water quality and species of the Delta, and letting more fresh water flow through.”
“A smarter path to building a strong water system in California would be to help communities that rely on the Delta’s water now to invest in strategies that help them become more regionally self-reliant.”
https://www.sierraclub.org/california/capitol-voice-february-2018#Delta
Save the California Delta Alliance (STCDA) 
Good that the Sierra club has joined in the struggle. How about a petition to our elected reps in Sacramento?