MURRIETA, Calif. (KESQ) - A 51-year-old Riverside County firefighter accused of sexually assaulting three women -- including while he was on duty in Temecula -- pleaded not guilty today to a dozen felony and misdemeanor offenses. David Renteria III of Placentia, in Orange County, was arrested in April following a sheriff's department investigation initiated last fall. Renteria is charged with four counts of forcible rape, two counts of sodomy…