EPA seeks to recovery costs incurred in performing a removal action the settling party had agreed to perform, but failed to perform. The Respondent has agreed to reimburse EPA's costs for the removal action in question (only a small, discrete part of the work required at the Site), plus interest beginning to accrue on March 31, 2004, the date of EPA's demand for costs. The Respondent has also agreed to pay a penalty for its failure to perform.