Leaking Underground Storage Tank Trust Fund Amendments Act of 1998

Leaking Underground Storage Tank Trust Fund Amendments Act of 1998 - Amends the Solid Waste Disposal Act to require the Administrator of the Environmental Protection Agency (EPA) to distribute to States at least 80 percent of the funds appropriated to EPA from the Leaking Underground Storage Tank Trust Fund each fiscal year for the reasonable costs under State cooperative agreements of: (1) State actions under the EPA program for petroleum release responses; (2) necessary administrative expenses directly related to corrective action and compensation programs under State financial responsibility requirements; (3) other costs of such programs in any instance, as determined by the State, in which an owner's or operator's financial resources (including resources provided by such programs) are inadequate to pay the costs of a corrective action without significantly impairing the ability to continue in business; (4) enforcement by a State or local government of an approved State underground storage tank (UST) program or similar State or local requirements; and (5) State or local corrective actions pursuant to regulations regarding corrective action in response to UST releases. Prohibits use of such funds to provide financial assistance to an owner or operator in meeting regulatory requirements for upgrading of existing UST systems, except in the case described by (3) above.

Requires the Administrator to: (1) implement a strategy to take corrective action in response to releases from leaking USTs within the exterior boundaries of Indian reservations or other areas within the jurisdiction of an Indian tribe and enforce requirements regulating such USTs; and (2) report to the Congress biennially on the status of the UST program in such areas.

Sets forth requirements for allocation of funds to States. Requires States to limit the proportion of such funds used to pay administrative expenses to a percentage that may be established by State law.

Makes inapplicable to Trust Fund amounts provided to owners or operators under programs described in (2), above, provisions for recovery of petroleum release corrective or enforcement action costs.

(Sec. 3) Amends the Internal Revenue Code to make the Trust Fund available to carry out this Act.

(Sec. 4) Requires the Administrator to conduct a study to determine the corrosive effects of methyl tertiary butyl ether on USTs.