The requirements for construction contractors and federally-assisted construction contractors are different. Construction contractors covered under VEVRAA and Section 503 are required to ask applicants and new hires to self-identify if they are a protected veteran or an individual with a disability. This obligation does not apply to federally-assisted construction contractors. Pam Ploor has written an excellent two-part article
that was published in The OFCCP Digest
that lays out the compliance obligations of construction contractors and the difference between a construction contract and a federally-assisted construction contract. I would encourage you to read her article.