Stations in Contra Costa County are set to close: They include Station No. 4 on Hawthorne Drive in Walnut Creek, No. 11 on Center Avenue in Clayton, No. 12 on Shell Avenue in Martinez, and No. 16 on Los Arabis Avenue in Lafayette. That would leave the total number of district stations to 24 when the closures go into effect January 1, 2013. Stephanie Chuang reports.