A ChartAnnotation's siteId determines which site's trend charts the annotation appears on. Annotations are site-scoped rather than well-scoped because many events — such as a regulatory order, a remediation system startup, or a significant storm — affect the entire site and should be visible on charts for all wells at that location. When compliance staff generate a site summary report for a regulatory agency, the ChartAnnotations for that siteId provide the narrative context that accompanies the concentration data tables and trend plots.
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Chart Annotation Site
The `siteId` on a ChartAnnotation links the event marker to a specific monitoring site.