Montrose III: Appeals Court Rejects “Elective Vertical Stacking,” but Declines to Find “Universal Horizontal Exhaustion” Absent Proof of Policy Wordings

September 14, 2017
Christopher Kendrick & Valerie A. Moore – Haight Brown & Bonesteel LLP

In Montrose Chemical Corp. v. Superior Court (No. B272387; filed 8/31/17) (Montrose III), a California appeals court found that excess insurance is not triggered for continuous and progressive losses until there has been horizontal exhaustion of underlying insurance, but there is no “universal horizontal exhaustion” because the order or sequence in which excess policies may be accessed depends on the specific policy wording at issue.

The coverage lawsuit was initiated by Montrose in 1990, when it was named in environmental actions for continuous and progressive property damage emanating from its Torrance chemical plant since the 1960s. Montrose had varying levels of insurance coverage throughout, but the total limits and attachment points of differing levels of excess coverage in any given year had changed from year-to-year. The coverage action was stayed in 2006 due to concern of prejudice to the underlying defense, but the stay was lifted in 2014 with Montrose entering a consent decree in the CERCLA action.

Reprinted courtesy of Christopher Kendrick, Haight Brown & Bonesteel LLP and Valerie A. Moore, Haight Brown & Bonesteel LLP
Mr. Kendrick may be contacted at
Ms. Moore may be contacted at


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