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They cannot lease the property beyond the scope of their authority under the master lease. So they have no right to lease it beyond 2024 and that lease is void and you would be able to move to remove that lease or have it modified.
As far as the contamination, you as the property owner are ultimately liable, but you would have recourse to sue the party who owned the tanks or had them installed, which would be the gas station to make them pay for the contamination their tanks caused you to incur fees to clean up.