offsetting collections received in fiscal year 2021 exceed $8,000,000, those excess amounts shall remain available until expended and be used for necessary expenses in this appropriation. Office of inspector general For necessary expenses of the Office of Inspector General in carrying out the provisions of the Inspector General Act of 1978, $45,100,000, to remain available until September 30, 2022. Buildings and facilities For construction, repair, improvement, extension, alteration, and purchase of fixed equipment or facilities of, or for use by, the Environmental Protection Agency, $39,676,000, to remain available until expended. Hazardous substance superfund (including transfers of funds) For necessary expenses to carry out the Comprehensive Environmental Response, Compensation, and Liability Act of 1980 (CERCLA), including sections 111(c)(3), (c)(5), (c)(6), and (e)(4) ( 42 U.S.C. 9611 ), and hire, maintenance, and operation of aircraft, $1,221,814,000, to remain available until expended, consisting of such sums as are available in the Trust Fund on September 30, 2020, as authorized by section 517(a) of the Superfund Amendments and Reauthorization Act of 1986 (SARA) and up to $1,221,814,000 as a payment from general revenues to the Hazardous Substance Superfund for purposes as authorized by section 517(b) of SARA: Provided , That funds appropriated under this heading may be allocated to other Federal agencies in accordance with section 111(a) of CERCLA: Provided further , That of the funds appropriated under this heading, $11,586,000 shall be paid to the Office of Inspector General appropriation to remain available until September 30, 2022, and $30,755,000 shall be paid to the Science and Technology appropriation to remain available until September 30, 2022. Leaking underground storage tank trust fund program For necessary expenses to carry out leaking underground storage tank cleanup activities authorized by subtitle I of the Solid Waste Disposal Act, $92,543,000, to remain available until expended, of