I live out in Concord (actually more like Clayton) and for all my lab procesing I use Action Photo Service who are excellent. Ive had slides, c41, and B/W developed there with excellent quality and turnaround time (same day if dropped off before 10am). They are in downtown concord. Their website is: http://www.actionphotoservice.com/
It may be far out for Antioch though...

-Josh