The US Department of Labor issues wage determinations. Each one lists the minimum wage and fringe rate for each trade classification in an area. The determination is bound into the bid documents.
Covered projects usually require certified payroll reports. Many states have their own prevailing wage laws for state and local work, with different rules.
Check the front-end documents for a wage determination before you price labor. Use the rates for the right classification and the right county. Ask the general contractor or the agency if a classification is unclear. This is general information, not legal advice. Check the bid documents and your state.