Service Contract Act and the Davis-Bacon Act

We have been awarded a subcontract from a construction company where the Prime is a Federal Agency that has incorporated the Davis-Bacon Act in the prime contract which flows down to us. We are providing security at the construction site so the labor category for Guard is not included under the Davis-Bacon Wage Determinations. Given this is a Federal contract, would our company need to follow the Service Contract Act Wage Determinations since Guards are included there? Or would the SCA have to be incorporated also in the Prime contract for this to apply? This happens regularly in our industry so I would like some opinions on how to handle. My first thought is that because the Prime contract is a construction contract and not a service contract per se, we are not subject to the SCA since it is not incorporated in the contract. But I do not want to get audited by DOL and be in violation. Any opinions would be greatly appreciated.