The Secretary of the Interior, the Secretary of the Army, and the Secretary of Energy, respectively, shall appoint such attorneys, engineers, and other experts as may be necessary for carrying out the functions entrusted to them under this chapter, and shall fix the compensation of each of such attorneys, engineers, and other experts; and they may, subject to the civil-service laws, appoint such other officers and employees as may be necessary to carry out such functions and fix their salaries in accordance with chapter 51 and subchapter III of chapter 53 of title 5. In the administration of this chapter the services of regular employees in the Bureau may be utilized and an equitable part of the salaries of such employees whose services are thus utilized may be charged by the Bureau to the operating costs of the power features of the Fort Peck project. The Bureau similarly may utilize and charge for facilities of the Bureau which economically can be used in connection with the administration of this chapter.