Hartford and Navigators want their money back. They say Nautilus walked away from a Missouri bridge claim it should have covered.
The two insurers sued Nautilus Insurance Company on May 14, 2026 in federal court in Arizona, alleging Nautilus wrongfully denied defense and indemnity to their shared insured, KCI Construction Company. According to the complaint, KCI was the general contractor on a Missouri Department of Transportation project to rehabilitate 24 bridges along Route I-55 in St. Louis.
KCI subcontracted the deck demolition on one bridge to Premier Demolition, Inc., the filing states. The subcontract required Premier to carry Commercial General Liability insurance and name KCI as an additional insured on a primary and non-contributory basis. The plaintiffs say Premier worked on Spans 1 through 8 between August 18 and October 4, 2023, and that significant damage followed - to girders, splice plates, stiffeners and web supports.
MoDOT moved quickly. On November 28, 2023, it ordered KCI to replace girder lines 3 through 9 and evaluate three others. According to the complaint, a June 2024 follow-up order stated the bridge "incurred significant damage during the deck removal in September and October 2023." KCI took Premier to arbitration, and by November 22, 2024 the two had stipulated to a $12 million judgment, with at least $6 million falling after 12:01 am on September 30, 2023 - inside the Nautilus policy period.
That timing is the whole fight. The complaint says the Nautilus primary and umbrella policies ran from September 30, 2023 to September 30, 2024, with $1 million / $2 million on the primary and $5 million / $5 million excess. Hartford and Navigators sat behind KCI's own program: Hartford on the primary at $1 million / $2 million, Navigators excess at $5 million / $5 million.
The Nautilus Primary Policy has two additional insured endorsements - one for ongoing operations, one for completed operations. The ongoing operations form, as quoted in the complaint, covers KCI for "property damage" directly caused by Premier or anyone working on Premier's behalf during Premier's ongoing operations for KCI. The completed operations form covers KCI for "property damage" directly caused by "your work" within the "products-completed operations hazard." Both endorsements say the Nautilus primary is primary and will not seek contribution from other insurance available to the additional insured. The excess policy follows form.
KCI tendered to Nautilus in March 2024, the filing states. On May 16, 2024, Berkley Environmental - acting for Nautilus - declined. According to the complaint, the denial focused only on Span 8, even though the broader claim involved Spans 1 through 8. The plaintiffs say Nautilus's position was that Premier finished Span 8 on September 21, 2023 and that KCI and Premier had notice of damage by September 22, 2023 - both dates falling before the Nautilus policies incepted on September 30.
KCI and Premier pushed back in three letters across May 2024, the complaint says, telling Nautilus the damage stretched across Spans 1 through 8, that Premier kept working those spans through October 4, and that the notice conversations Nautilus cited applied only to Span 8. KCI then tendered Premier's counterclaim on June 20, 2024. Nautilus declined again on July 12, 2024, the filing states, relying on what the complaint calls "the same incorrect and self-serving contentions."
By the time the suit was filed, the plaintiffs say, Hartford had paid over $75,000 in defense fees and costs plus $1 million in indemnity. Navigators says it had paid over $3.35 million in repair costs.
The two insurers now want declaratory relief on Nautilus's duty to defend and duty to indemnify, equitable indemnity, and - pled in the alternative - equitable contribution. They want a court to confirm KCI qualified as an additional insured under both Nautilus policies, that Nautilus's coverage sat primary to theirs, and that Nautilus must reimburse what they have already paid. The complaint alleges damages in excess of $75,000.
For insurers and claims teams, the fight turns on a familiar question: how additional insured endorsements interact with known-loss arguments when damage straddles a policy inception date.
The allegations have not been tested in court. Nautilus has not yet filed a response, and no court has ruled.
