David Cosgrave serves as Senior Legislative Aide to Supervisor Ray Mueller, representing the Third Supervisorial District in San Mateo County. In this role, he advises on a broad range of policy and community issues, including public safety, emergency management, infrastructure, land use, and constituent services. He works closely with county departments, partner agencies, and community stakeholders to advance district priorities, support informed decision-making, and help implement Supervisor Mueller’s initiatives by connecting policy, projects, and community input.
Cosgrave brings more than 35 years of experience in fire service, emergency response, emergency management, and community preparedness. He is credentialed as an Emergency Management Specialist through the California Governor's Office of Emergency Services, a Certified Fire Officer, holds an Associate of Science degree in Fire Science, and is a retired paramedic. He previously served as a Supervising Emergency Manager for the County, where he led disaster planning, coordinated countywide response and recovery efforts, managed evacuation planning and alert and warning systems, and worked with local, state, and private partners on fire mitigation and fuel management initiatives.
While in that role, Cosgrave was directly involved with Supervisor Mueller’s CRISP project. Through his current position, he continues to support and advance the CRISP project, bringing the expertise developed in his previous role together with his firsthand knowledge and lived experience as a lifelong resident of the Third Supervisorial District.
He also served in senior fire service leadership positions, including Division Chief / Assistant Chief, and Battalion Chief, where he supervised personnel, managed operations and budgets, and served incident command roles during complex emergencies. He has contributed to regional planning efforts, including participation in the County’s Multi-Jurisdictional Local Hazard Mitigation Plan.
A lifelong resident of the Third Supervisorial District, Cosgrave brings deep local knowledge and a longstanding commitment to serving the communities of his district. He is passionate about individual and community preparedness and resilience, and continues to support efforts that strengthen readiness, public awareness, and community capacity across the Third Supervisorial District.
Community Liaison to:
- Constituents west of Skyline Blvd
Portfolio:
- Building and Planning
- Public Works
- Public Safety Communications
- Emergency Management
- County Fire
