A bill to authorize the Administrator of the Environmental Protection Agency to accept, as part of a settlement, diesel emission reduction Supplemental Environmental Projects, and for other purposes.

Authorizes the Administrator of the Environmental Protection Agency (EPA) to accept, as part of a settlement of any alleged violations of environmental law, diesel emissions reduction Supplemental Environmental Projects if the projects: (1) protect human health or the environment; (2) are related to the underlying alleged violations; (3) do not constitute activities that the defendant would otherwise be legally required to perform; and (4) do not provide funds for EPA's staff or for contractors to carry out EPA's internal operations.

Directs the Administrator, in any such settlement agreement, to require the defendant to include in the settlement documents a certification under penalty of law that the defendant would have agreed to perform a comparably valued, alternative project other than a diesel emissions reduction Supplemental Environmental Project if the Administrator were precluded by law from accepting a diesel emission reduction Supplemental Environmental Project. States that failure by the Administrator to include this language shall not create a cause of action against the United States under the Clean Air Act or any other law or create a basis for overturning a settlement agreement entered into by the United States.

Amends the Energy Policy Act of 2005 to include the District of Columbia as a state for purposes of grant programs for diesel emission reductions.