In a victory for toxic tort defendants facing putative class actions and underscoring the “rigorous analysis” that district courts must perform prior to certifying a class, the Seventh Circuit reversed a district court’s certification of a class of Illinois property owners who claimed that benzene and other contaminants from Defendants’ oil refinery had leaked into the groundwater under their homes. See Parko v. Shell Oil Co., Nos. 13-8023 & 12-8024 (7th Cir. Jan. 17, 2014). The court held that the district court judge had not adequately analyzed the question of predominance, a requirement for class certification, and remanded the issue for further factual development. Parko, slip op. at 9.

The district court certified a class of approximately 150 property owners in Roxana, Illinois, in an action based in common law nuisance and torts. Id. at 2-3. On appeal, the Seventh Circuit rejected Defendants’ argument regarding the numerosity requirement for class certification, holding that the number of class members with a valid claim is an issue to be determined post-certification. Id. at 3. However, on the question of predominance, the Seventh Circuit agreed with Defendants that the alleged contamination occurred over a period of 90 years and may have been caused by various responsible parties, and therefore the property owners in the class experienced different levels of contamination and damages, if any. Id. at 5.

In addition, the Seventh Circuit questioned Plaintiffs’ intent to rely on a hydrogeologist’s measure of benzene in the groundwater beneath the homeowners’ properties to show loss in property value. The court emphasized that the owners’ water supply did not come from groundwater but from an aquifer, and if the expert’s evidence was rejected, there would be “no basis for the claim that the benzene levels in the groundwater are the common cause of the loss of property values that the class alleges.” Id. at 6. Finding that the district court failed to investigate the “realism of the [P]laintiffs’ injury and damage model” in light of Defendants’ arguments, the Seventh Circuit reversed and instructed the district court judge to revisit the issue of certification in light of its opinion. Id. at 7.