Fixing the plumbing: Building interoperability between wastewater genomic surveillance datasets and systems using the PHA4GE contextual data specification. As wastewater surveillance expands globally, the ability to share, compare, and integrate genomic and metadata across datasets becomes essential. This work describes the application of the PHA4GE contextual data specification to improve interoperability between wastewater genomic surveillance datasets and systems, enabling more effective collaborative public health responses.