Environmental contamination often causes injuries that occur over long periods of time. These “long-tail” injuries, which tend to span periods during which a liable party was covered by multiple insurers, do not map neatly onto standard indemnification insurance policies. As a result, liable parties and their insurers frequently engage in protracted litigation to minimize the portion that they must contribute to environmental remediation projects. In Boston Gas Co. v. Century Indemnity, the U.S. Court of Appeals for the First Circuit upheld an application of Massachusetts’s recently announced pro rata apportionment rule, which greatly reduced the insurer’s liability. Proponents of pro rata apportionment argue that it lessens the burden that indemnification litigation puts on court dockets and that it promotes environmentally conscientious business practices. This Comment challenges those claims and argues that pro rata apportionment may actually undermine environmental remediation projects by limiting the amount of private resources available for them.