The New Mexico Supreme Court considered whether the word "sudden" found in the pollution exclusion of a liability policy was ambiguous. See United Nuclear Corp. v. Allstate Ins. Co., No. 32,939 (N.M. Aug. 23, 2012).
United Nuclear operated several uranium mines in New Mexico from the 1960s through the early 1980s. At Church Rock Mine, a dam breached. 94 million gallons of radioactive liquid escaped from the tailings pond and poured into nearby Rio Puerco. The spill was described as the largest accidental release of radioactive material in U.S. history.
United Nuclear was insured by a number of carriers. Policies issued by Allstate and in effect between August 1, 1977 and June 1, 1981, were at issue in this appeal. When sued, United Nuclear tendered to Allstate. Coverage was denied and United Nuclear filed a third-party complaint in the underlying suit, seeking a declaration that Allstate was required to defend and indemnify United Nuclear.
Allstate moved for summary judgment based upon the pollution exclusion which removed from coverage all claims for damages caused by pollution or contamination unless the discharges were "sudden and accidental." The trial court granted the motion, which was upheld by the Court of Appeals.
The Supreme Court first looked at dictionary definitions of the word "sudden." Dictionaries defined "sudden" as either synonymous with "unexpected," or as the temporal descriptor of a brief occurrence, or both. Other courts had found definitions of "sudden" to be so distinct as to render the term ambiguous.
The New Mexico Supreme Court further noticed that courts across the country were evenly divided on the meaning of the term "sudden," with nearly half concluding the term is ambiguous.
Therefore, in the absence of a definition of the term in the policies, finding diverging definitions in standard dictionaries and the lack of an consensus among courts nationwide, the court determined that the meaning of the term "sudden" as used in the policies was ambiguous. The case was remanded to allow United Nuclear to prove that its operations led to discharges that were in fact "sudden and accidental."