CHICAGO - Certification of a class of southern Illinois residents who claim that the value of their properties was affected by an underground plume from the leak of benzene-contaminated petroleum products from a nearby refinery was vacated Jan. 17 by the Seventh Circuit U.S. Court of Appeals, which said the trial judge should have explored the viability of plaintiffs' claims (ConocoPhillips Company, et al. v. Jeana Parko, et al., No. 13-8023, Shell Oil Company, et al. v. Jeana Parko, et al., No. 13-8024, 7th Cir.; 2014 U.S. App. LEXIS 1018).