The Eighth Circuit faced unusual facts in determining that the collapse of a cave serving as a storage facility was not covered under the policy. Westchester Surplus Lines Ins. Co. v. Interstate Underground Warehouse & Storage, Inc., 2020 U. S. App. LEXIS 83 8th Cir. Jan. 3, 2020).

Interstate operated an underground storage facility in a cave that formerly housed a limestone mine. In 2014, Interstate experienced a series of "dome-outs," in which layers of rock destabilized, detached, and collapsed from above into the cave.

Interstate's policy with Westchester included coverage for collapse of a "building" caused by "building decay." Westchester sought a declaratory judgment that Interstate's loss was not covered. The district court granted summary judgment for Westchester because the cause of the loss was not "building decay" within the meaning of the primary policy.