The first step toward sustaining one of San Joaquin County’s most precious resources took nearly two years. And it may have been the easiest part of the journey. Still, local officials sound optimistic about their efforts to comply with the state’s new groundwater mandate,largely because the county’s diverse, sometimes feuding water agencies have agreed to at least sit down at the table and talk about it. “We’ve gotten this far,” San Joaquin County Supervisor Chuck Winn said last week, ahead of a major deadline at the end of this month.