We are a general contractor bidding on a public project. For prevailing wages and certified payroll does that mean any subcontractor we hire to be on our job has to pay their employees prevailing wage and supply certified payroll to us, the general contractor?
Generally, yes. The prime contract will have that information but a safe answer is yes. If it's a "public project" that is actually a federal government project, the wage will stay the same under the Davis-Bacon act. Under a normal municipal of state goverment prevailing wage project, the wage can change (usually with inflation). So, if it's a long project make sure your bid has some escalation costs in there.
Also, make sure any subcontracts and purchase orders you use incorporate the prevailing wage requirements. The Department of Industrial Relations fines for violating this are big, you must pay them up front, and fighting them is costly and time consuming. So, better just to get it right the first time.