P and Union (D) both participated in nearly a century of mining operations in the Coeur d'Alene River watershed. In the 1990s, the United States, the State of Idaho, and the Coeur d'Alene Tribe each filed various claims against P and other mining companies for response costs and natural resource damages at the Coeur d'Alene site. P was found at least 22 percent responsible. P filed for bankruptcy protection under Chapter 11 of the United States Bankruptcy Code. Through bankruptcy, P sought to resolve approximately $6.5 billion in environmental liabilities at 53 sites throughout the country. D and the United States both filed proofs of claim. P and the United States executed an agreement settling the United States' Coeur d'Alene claims. P then filed the underlying contribution action, seeking to recoup from D a share of the $482 million it paid under the US CDA Settlement. P's original complaint defined the Coeur d'Alene site as a 1,500-square mile area. Less than two months later, P filed a First Amended Complaint ('FAC') as of right under Rule 15(a)(1) and amended the definition of 'Coeur d'Alene Basin' to include the North Fork drainage area that was originally excluded. D filed a motion to dismiss under Rule 12(b)(6), arguing that the claim was barred in part by the statute of limitations. The court granted the motion because of a prior agreement to settle claims. The court rejected D’s claims regarding the statute of limitations. P appealed.