If two water diversion tunnels could help solve California’s water delivery woes, can one tunnel be even better? Over the past decade, state officials have designed a massive plumbing solution for the Sacramento-San Joaquin Delta. Known as California WaterFix, it involves building two giant tunnels to divert a portion of the Sacramento River’s flow underneath the estuary and directly to existing diversion pumps and canals near Tracy. The cost is estimated at more than $15 billion.