All laborers and mechanics employed by contractors or subcontractors on projects assisted by the Secretary which are undertaken by approved applicants under this section shall be paid wages at rates not less than those prevailing on similar construction in the locality, as determined by the Secretary of Labor in accordance with sections
3141–3144,
3146, and
3147 of title
40. The Secretary shall not extend any financial assistance under this section for any project without first obtaining adequate assurance that these labor standards will be maintained on the construction work; except that compliance with such standards may be waived by the Secretary in cases or classes of cases where laborers or mechanics, not otherwise employed at any time on the project, voluntarily donate their services without compensation for the purpose of lowering the costs of construction and the Secretary determines that any amounts thereby saved are fully credited to the person, corporation, association, organization, or other entity, undertaking the project. The Secretary of Labor shall have, with respect to the labor standards specified in this section, the authority and functions set forth in Reorganization Plan Numbered 14 of 1950 (
15 F.R.
3176;
64 Stat. 1267), and section
3145 of title
40.