EXPLAINER
The Yuma Biosolids Dispute: A Timeline
A chronology of supported research, requests and public actions, with event dates kept separate from scientific findings.
This chronology follows dated records. A report date identifies when a document was issued or presented; it is not necessarily the sampling date. A request identifies what a public body asked for; it does not prove the allegations supporting the request. An announcement identifies what an agency said it had done.
2015 and 2018: the historical research
July 13, 2015: a University of Arizona Cooperative Extension report, prepared with the Yuma County Pest Abatement District, describes fly-pathogen sampling. The study’s observations belong to its sampled locations and trapping dates.
April 24, 2018: Paula Rivadeneira’s presentation describes a selected-site investigation carried out in 2017. Its findings and calls for further research should be read together. Neither historical record can, on its own, allocate regional fly sources in 2026.
Read the historical research event
December 2025: a request to the State
December 1, 2025: the County Board’s signed letter asks the State Land Department to terminate AgTech’s month-to-month lease and identify another lessee. The letter documents the Board’s position and the concerns it relayed. The underlying complaints and loss calculations are separate evidence.
July and September 2026: different public actions
July 1, 2026: EPA announces draft guidance about reducing PFOA and PFOS risks in biosolids. This federal draft process is distinct from Arizona’s later lease action.
September 2, 2026: Yuma’s Council record lists the biosolids service award as passed. An award is not a payment ledger.
September 10, 2026: the Governor announces action affecting five AgTech-related agricultural leases. The Attorney General separately issues a statement about its investigation. These records concern related issues, but each has its own institutional purpose and evidence limits.
Browse the complete public chronology
Why some dates are absent
The draft library also identifies an April County news release and an ADEQ inspection. Their original dated records could not be recaptured in this review, so their exact-date entries remain unpublished pending that check. This does not mean the events did not occur.
Court events are also excluded until the underlying docket and filings can support their dates and descriptions. Filing, service, a hearing and a ruling are different procedural events. A news report or research note cannot be silently promoted into a court record.
How to read changes over time
A later government action does not retroactively turn an earlier complaint into a proven fact. Conversely, an earlier limited inspection does not settle conditions at every later date. Follow each event’s source and compare the question it actually addresses with the conclusion being drawn from it.