A settling CERCLA defendant that released or threatened to release hazardous substances into the environment at Operable Unit Two of the National Fireworks Superfund alternative site in Cordova, Tennessee, must reimburse EPA and the state of Tennessee for costs incurred and to be incurred in connection with response actions at the site, and DOD, as a settling federal agency, must pay defendant a percentage of past and future costs at the site and contribute to payments defendant is making for EPA's and the state's response costs.