CHULA VISTA — Former Chula Vista police Chief Richard Emerson, a visionary who led the force for 18 years, died peacefully Friday, the Police Department announced this week. He was 70. Emerson, who was remembered as a role model and mentor who left a mark on the careers of his subordinates, led the Police Department between 1992 and 2009 — a period in which the city and police force saw tremendous growth. Emerson worked for the Pasadena Police Department for 23 years before he was hired as chief in Chula Vista. Under his leadership, the Chula Vista Police Department created new units, including a special investigations team; doubled the size of the traffic unit to address community concerns; expanded the school resource officer unit from one officer to 23; created volunteer positions, including senior patrol volunteers; founded the Chula Vista Police Foundation, the fundraising arm of the Police Department; and constructed the police station that houses the department today, officials said.