ELR Citation: ELR 21112
No(s). 90-1573 (D.C. Cir. Jun 14, 1991)

The court holds that the Environmental Protection Agency (EPA) failed to adequately explain how it used arsenic in determining the toxicity score that was used in placing a facility on the National Priorities List (NPL), pursuant to §105 of the Comprehensive Environmental Response, Compensation, and Liability Act (CERCLA). The court first holds that petitioner waived its challenge to the "observed release" score component of the air route, one of three routes that are scored under the Hazard Ranking System to measure the potential for harm to humans and the environment from migration of a hazardous substance. Petitioner failed to object to the wind direction data on the date in question during comments to EPA. However, as to the "toxicity" score component of the air route, the court holds that EPA failed to explain how arsenic, which is bound in slag at petitioner's facility, can reasonably be expected to escape into the atmosphere. EPA's mere claim that the bound arsenic poses a threat of release, without any explanation but that the slag is not contained, is insufficient for the court to determine whether the Agency's decision was reasonable. The court is not expert in the scientific theory by which the potential for migration is measured and cannot defer to agency expertise that was never explained. Thus, the court remands to EPA of a reasoned explanation for the Agency's conclusion that arsenic is reasonably likely to be transported via the air route.

Counsel for Petitioner
James W. Moorman
Cadwalader, Wickersham & Taft
1333 New Hampshire Ave. NW, Washington DC 20036
(202) 862-2200

Counsel for Respondent
George Wyeth
Environmental Protection Agency
401 M St. SW, Washington DC 20460
(202) 382-4700

Before: MIKVA, Chief Judge, SILBERMAN and THOMAS, Circuit Judges.