Chief Contreras was hired as a Firefighter with the City of Hayward in 1995. During 2005, he was promoted to Captain. In 2008 and 2011, Chief Contreras was further promoted to the positons of Battalion Chief and Deputy Chief (Special Operations), respectively. He attained the position of Fire Chief in 2012.
During his lengthy tenure with the City, Chief Contreras has been heavily involved with Firefighters Local 1909. He was elected president in 2002 and served in that capacity for 6 years. During this time, he was heavily involved in negotiating 3 labor contracts with the City. In addition to serving as president, Chief Contreras was instrumental in helping to remodel the Local 1909 Union Hall, served as chair of the 1909 Political Action Committee, and spent 5 years as an executive board member and shift representative.
Outside of his work related duties, Chief Contreras served as an executive board member for the Alameda County Central Labor Council and was also an active participant in the successful passage of Measure A in 2009, which was the only user utility tax to pass in the state during that time.