Montrose III: Vertical Exhaustion Applies in Upper Layers of Excess Coverage

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Attorneys Christopher Kendrick and Valerie A. Moore analyze Montrose Chemical Corp. of Cal. v. Superior Court.

May 18, 2020
Christopher Kendrick & Valerie A. Moore – Haight Brown & Bonesteel LLP

In Montrose Chemical Corp. of Cal. v. Superior Court (No. S244737, filed 4/6/20) (Montrose III), the California Supreme Court held that, as between excess insurers at differing levels of coverage, a rule of “vertical exhaustion” or “elective stacking” applies, whereby the insured may access any excess policy once it has exhausted other excess policies with lower attachment points in the same policy period. The Court limited the rule to excess insurance, stating that “[b]ecause the question is not presented here, we do not decide when or whether an insured may access excess policies before all primary insurance covering all relevant policy periods has been exhausted.”

Montrose manufactured the insecticide DDT in Torrance from 1947 to 1982. In 1990, the state and federal governments sued Montrose for environmental contamination and Montrose entered into partial consent decrees agreeing to pay for cleanup. Montrose claimed to have expended in excess of $100 million doing so, and asserted that its future liability could exceed that amount.

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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