Gov. Jerry Brown’s plan to build two giant tunnels to send Northern California water southward moved a step closer Thursday to final state and federal decisions, with the state’s release of a 90,000-page environmental review supporting the $15.7 billion project. Brown’s administration is pushing for final federal and state approval of the 35-mile-long, 40-foot-wide tunnels, touted to ensure more reliable water deliveries to city and farm water agencies in Central and Southern California.