Better talk to your insurer. "Occurrence based" and "claims made" are NOT the same type of coverage no matter who is doing the covering. They are also tied into the legal definitions for the state where the project is occurring.
If your client truly is asking for an insurance product that isn't available in the state of California, a nice letter from your carrier should clear that up.
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Anne Whitacre Assoc. AIA
Gensler
San Francisco CA
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