(a) Final denial of an administrative claim shall be in writing and sent to the claimant, his attorney, or legal representative by certified or registered mail. The notification of final denial may include a statement of the reasons for the denial and shall include a statement that, if the claimant is dissatisfied with EPA's action, he may file suit in an appropriate U.S. District Court not later than 6 months after the date of mailing of the notification.

(b) Prior to the commencement of suit and prior to the expiration of the 6-month period after the date of mailing by certified or registered mail of notice of final denial of the claim as provided in 28 U.S.C. 2401(b), a claimant, his duly authorized agent, or legal representative, may file a written request with the EPA for reconsideration of a final denial of a claim under paragraph (a) of this section. Upon the timely filing of a request for reconsideration, EPA shall have 6 months from the date of filing in which to make a final disposition of the claim and the claimant's option under 28 U.S.C. 2675(a) to bring suit shall not accrue until 6 months after the filing of a request for reconsideration. Final action on a request for reconsideration shall be effected in accordance with the provisions of paragraph (a) of this section.