D disposed of trichloroethylene ('TCE') and other toxic chemicals at a military base. This created plumes of toxic pollution underneath property extending several miles north of Lowry, including the area underneath P's property. D tested P's irrigation well and found it was contaminated with TCE. Operations at the base had stopped 3 years before, but the toxic plume continued to migrate. P sued under the Federal Tort Claims Act for continuing trespass and nuisance and sought unspecified damages. The District Court granted D's motion to dismiss for lack of subject matter jurisdiction under Fed. R. Civ. P. 12(b)(1). P's permanent tort claims that were time-barred. The District Court held that P's 1998 claims were untimely because P knew or should have known his property might be contaminated by TCE from Lowry as of 1995. The court held that the nuisance and trespass was limited to the actual release of TCE by the United States and not the continued migration or ongoing presence of pollution on P's property. P appealed. P argued that the migration and presence of toxic chemicals on his property were in themselves wrongful acts for which the United States was responsible and constituted continuing torts. D argued that P's claims were permanent torts under our irrigation ditch cases and time-barred under the FTCA's statute of limitations. The Tenth Circuit certified two questions.